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We determined the prevalence of plasmid-mediated quinolone resistance mechanisms among non-Typhi Salmonella spp. isolated from humans, food animals, and retail meat in the United States in 2007. Six isolates collected from humans harbored aac(6')Ib-cr or a qnr gene. Most prevalent was qnrS1. No animal or retail meat isolates harbored a plasmid-mediated mechanism. [ABSTRACT FROM AUTHOR]

Goats are often asymptomatic carriers of Campylobacter , including the foodborne pathogen Campylobacter jejuni. Infections can have significant and economically detrimental health outcomes in both humans and animals. The primary objective of this study was to estimate the prevalence of Campylobacter in U.S. goat herds. Campylobacter species were isolated from 106 of 3,959 individual animals and from 42 of 277 goat operations that participated in fecal sample collection as part of the National Animal Health Monitoring System Goat 2019 study. Weighted animal-level prevalence was 2.3% (SE = 0.5%) and operation prevalence was 13.0% (SE = 3.2%). Animal-level prevalence ranged widely from 0 to 70.0%, however, 52.4% of positive operations (22/42) had only a single isolate. C. jejuni was the most frequently isolated species (68.9%; 73/106), followed by C. coli (29.3%, 31/106). A total of 46.2% (36/78) of viable isolates were pan-susceptible to 8 antimicrobials. Resistance to tetracycline (TET) was observed in 44.9% (35/78) of isolates, while 12.8% (10/78) were resistant to ciprofloxacin (CIP) and nalidixic acid (NAL). Among all isolates, a single resistance profile CIP-NAL-TET was observed in 3.8% (3/78) of isolates. A total of 35 unique sequence types (STs) were identified, 11 of which are potentially new. Multiple C. jejuni STs were observed in 48.1% (13/27) of positive operations. Goats with access to surface water, operations reporting antibiotics in the feed or water (excluding ionophores and coccidiostats), and operations reporting abortions and without postabortion management tasks had significantly greater odds of being Campylobacter positive. This snapshot of the U.S. goat population enriches the limited pool of knowledge on Campylobacter species presence in U.S. goats.

Surveillance of antimicrobial-resistant pathogens in U.S. retail meats is conducted to identify potential risks of foodborne illness. In this study, we conducted a phenotypic and genotypic analysis of Escherichia coli recovered from a diverse range of retail meat types during 2018-2019 in North Carolina. The investigation was conducted as part of the National Antimicrobial Resistance Monitoring System (NARMS). Retail meat sampling and E. coli isolation were performed in accordance with NARMS retail meat isolation protocols. We used the Sensititre™ broth microdilution system to determine phenotypic resistance to 14 antimicrobial agents and the Illumina next-generation sequencing platform for genotypic resistance profiling. The highest prevalence of E. coli isolates was found in ground turkey ( n  = 57, 42.9%) and chicken ( n  = 27, 20.3%), followed by ground beef ( n  = 25, 18.9%) and pork ( n  = 24, 18%). The isolates were divided into seven different phylogroups using the Clermont typing tool, with B1 ( n  = 59, 44.4%) and A ( n  = 39, 29.3%) being the most dominant, followed by B2 ( n  = 14, 10.5%), D ( n  = 7, 5.3%), F ( n  = 6, 4.5%), E ( n  = 3, 2.3%), and C ( n  = 2, 1.5%). Using multilocus sequence typing (MLST), 128 Sequence types (STs) were identified indicating high diversity. Phenotypic and genotypic resistance was observed toward aminoglycosides, sulfonamides, beta-lactams, macrolides, tetracyclines, phenicols, and fluoroquinolones. Ground turkey samples were more resistant to the panel of tested antimicrobials than chicken, beef, or pork ( p  < 0.05). All isolates were found to be susceptible to meropenem. A high percentage of turkey isolates ( n  = 16, 28%) were multidrug-resistant (MDR) compared with 18.5% of chicken ( n  = 5), 8.4% of pork ( n  = 2), and 8% of beef isolates ( n  = 2). This study highlights the benefit of surveillance to identify MDR E. coli for epidemiologic tracking and is a comprehensive report of the phenotypic and genotypic characterization of E. coli isolated from retail meats in North Carolina.

Escherichia coli and Enterococcus species are normal bacteria of the gastrointestinal tract and serve as indicator organisms for the epidemiology and emergence of antimicrobial resistance in their hosts and the environment. Some E. coli serovars, including E. coli O157:H7, are important human pathogens, although reservoir species such as goats remain asymptomatic. We describe the prevalence and antimicrobial resistance of generic E. coli , E. coli O157:H7, and Enterococcus species collected from a national surveillance study of goat feces as part of the National Animal Health Monitoring System (NAHMS) Goat 2019 study. Fecal samples were collected from 4918 goats on 332 operations across the United States. Expectedly, a high prevalence of E. coli (98.7%, 4850/4915) and Enterococcus species (94.8%, 4662/4918) was found. E. coli O157:H7 prevalence was low (0.2%; 10/4918). E. coli isolates, up to three per operation, were evaluated for antimicrobial susceptibility and 84.7% (571/674) were pansusceptible. Multidrug resistance (MDR; ≥3 classes) was uncommon among E. coli , occurring in 8.2% of isolates (55/674). Resistance toward seven antimicrobial classes was observed in a single isolate. Resistance to tetracycline alone (13.6%, 92/674) or to tetracycline, streptomycin, and sulfisoxazole (7.0% 47/674) was the most common pattern. All E. coli O157:H7 isolates were pansusceptible. Enterococcus isolates, up to four per operation, were prioritized by public health importance, including Enterococcus faecium and Enterococcus faecalis and evaluated. Resistance to lincomycin (93.8%, 1232/1313) was most common, with MDR detected in 29.5% (388/1313) of isolates. The combination of ciprofloxacin, lincomycin, and quinupristin resistance (27.1%, 105/388) was the most common pattern detected. Distribution and characteristics of antimicrobial resistance in E. coli and Enterococcus in the U.S. goat population from this study can inform stewardship considerations and public health efforts surrounding goats and their products.

Background: Escherichia coli is commonly used as an indicator for antimicrobial resistance (AMR) in food, animal, environment, and human surveillance systems. Our study aimed to characterize AMR in E. coli isolated from retail meat purchased from grocery stores in North Carolina, USA as part of the National Antimicrobial Resistance Monitoring System (NARMS)., Materials and Methods: Retail chicken (breast, n = 96; giblets, n = 24), turkey (n = 96), and pork (n = 96) products were purchased monthly from different counties in North Carolina during 2022. Label claims on packages regarding antibiotic use were recorded at collection. E. coli was isolated from meat samples using culture-based methods and isolates were characterized for antimicrobial resistance using whole genome sequencing. Multi-locus sequence typing, phylogroups, and a single nucleotide polymorphism (SNP)-based maximum-likelihood phylogenic tree was generated. Data were analyzed statistically to determine differences between antibiotic use claims and meat type., Results: Of 312 retail meat samples, 138 (44.2%) were positive for E. coli, with turkey (78/138; 56.5%) demonstrating the highest prevalence. Prevalence was lower in chicken (41/138; 29.7%) and pork (19/138;13.8%). Quality sequence data was available from 84.8% (117/138) of the E. coli isolates, which included 72 (61.5%) from turkey, 27 (23.1%) from chicken breast, and 18 (15.4%) from pork. Genes associated with AMR were detected in 77.8% (91/117) of the isolates and 35.9% (42/117) were defined as multidrug resistant (MDR: being resistant to ≥3 distinct classes of antimicrobials). Commonly observed AMR genes included tetB (35%), tetA (24.8%), aph(3'')-lb (24.8%), and blaTEM-1 (20.5%), the majority of which originated from turkey isolates. Antibiotics use claims had no statistical effect on MDR E. coli isolates from the different meat types (X2 = 2.21, p = 0.33). MDR was observed in isolates from meat products with labels indicating "no claims" (n = 29; 69%), "no antibiotics ever" (n = 9; 21.4%), and "organic" (n = 4; 9.5%). Thirty-four different replicon types were observed. AMR genes were carried on plasmids in 17 E. coli isolates, of which 15 (88.2%) were from turkey and two (11.8%) from chicken. Known sequence types (STs) were described for 81 E. coli isolates, with ST117 (8.5%), ST297 (5.1%), and ST58 (3.4%) being the most prevalent across retail meat types. The most prevalent phylogroups were B1 (29.1%) and A (28.2%). Five clonal patterns were detected among isolates., Conclusions: E. coli prevalence and the presence of AMR and MDR were highest in turkey retail meat. The lack of an association between MDR E. coli in retail meat and antibiotic use claim, including those with no indication of antimicrobial use, suggests that additional research is required to understand the origin of resistance. The presence of ST117, an emerging human pathogen, warrants further surveillance. The isolates were distinctly diverse suggesting an instability in population dynamics., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Aworh et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Salmonella species are an important cause of gastrointestinal disease in animals, including goats. Additionally, Salmonella species are among the top five U.S. foodborne pathogens causing illness to humans. The goat industry is rapidly expanding in the U.S. yet estimates of Salmonella prevalence within these populations is lacking. The aim of this study was to investigate the fecal prevalence, antimicrobial resistance (AMR), biofilm potential, and virulence profile of Salmonella species isolated from goat feces as part of the United States Department of Agriculture (USDA) National Animal Health Monitoring System (NAHMS) Goat 2019 study, enteric microbe component. A total of 4917 fecal samples were collected from 332 operations, from September 2019-March 2020. Salmonella were isolated using standard enrichment and culture methods; antimicrobial susceptibility was determined by broth microdilution. Biofilm production was assessed using a crystal violet assay and normalized to a positive control strain, and PCR was used to detect virulence genes. Overall, we detected a low prevalence (0.7%, n = 35/4917) of Salmonella in goat feces and identified a broad range of serotypes including S. Bareilly (35%) and a single rare S. Sharon. All isolates were pansusceptible to 14 antimicrobials except one, which was resistant to only tetracycline (MIC ≥ 32 µg/mL). All strains were found to possess the majority of virulence determinants screened, and 40% (14 of 35) formed weak, moderate, or strong biofilm. We found a low prevalence of Salmonella, and characteristics of Salmonella in the U.S. goat population informs ongoing public health efforts to manage risk of animal food products and animal interactions., Competing Interests: Declaration of interest None., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Salmonella enterica subsp. enterica serovar Heidelberg has been associated with a broad host range, such as poultry, dairy calves, swine, wild birds, environment, and humans. The continuous evolution of S . Heidelberg raises a public health concern since there is a global dispersal of lineages harboring a wide resistome and virulome on a global scale. Here, we characterized the resistome, phylogenetic structure and clustered regularly interspaced short palindromic repeats (CRISPR) array composition of 81 S . Heidelberg strains isolated from broiler farms ( n = 16), transport and lairage ( n = 5), slaughterhouse ( n = 22), and retail market ( n = 38) of the poultry production chain in Brazil, between 2015 and 2016 using high-resolution approaches including whole-genome sequencing (WGS) and WGS-derived CRISPR genotyping. More than 91% of the S . Heidelberg strains were multidrug-resistant. The total antimicrobial resistance (AMR) gene abundances did not vary significantly across regions and sources suggesting the widespread distribution of antibiotic-resistant strains from farm to market. The highest AMR gene abundance was observed for fosA7 , aac(6')-Iaa , sul2 , tet(A) , gyrA , and parC for 100% of the isolates, followed by 88.8% for bla CMY -2 . The β-lactam resistance was essentially driven by the presence of the plasmid-mediated AmpC (pAmpC) bla CMY -2 gene, given the isolates which did not carry this gene were susceptible to cefoxitin (FOX). Most S . Heidelberg strains were classified within international lineages, which were phylogenetically nested with Salmonella strains from European countries; while CRISPR genotyping analysis revealed that the spacer content was overall highly conserved, but distributed into 13 distinct groups. In summary, our findings underscore the potential role of S . Heidelberg as a key pathogen disseminated from farm to fork in Brazil and reinforce the importance of CRISPR-based genotyping for salmonellae. Hence, we emphasized the need for continuous mitigation programs to monitor the dissemination of this high-priority pathogen., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Monte, Nethery, Berman, Keelara, Lincopan, Fedorka-Cray, Barrangou and Landgraf.)

Salmonella enterica is the most common foodborne pathogen worldwide. It causes two types of diseases, a self-limiting gastroenteritis and an invasive, more threatening, infection. Salmonella gastroenteritis is caused by several serotypes and is common worldwide. In contrast, invasive salmonellosis is rare in high-income countries (HIC) while frequent in low- and middle-income countries (LMIC), especially in sub-Saharan Africa (sSA). Invasive Nontyphoidal Salmonella (iNTS), corresponding to serotypes other than Typhi and Paratyphi, have emerged in sSA and pose a significant risk to public health. We conducted a whole-genome sequence (WGS) analysis of 72 strains of Salmonella isolated from diarrheic human patients and chicken meat sold in multipurpose markets in Dakar, Senegal. Antimicrobial susceptibility testing combined with WGS data analysis revealed frequent resistance to fluoroquinolones and the sulfamethoxazole-trimethoprim combination that are among the most used treatments for invasive Salmonella. In contrast, resistance to the historical first-line drugs chloramphenicol and ampicillin, and to cephalosporins was rare. Antimicrobial resistance (AMR) was lower in clinical isolates compared to chicken strains pointing to the concern posed by the excessive use of antimicrobials in farming. Phylogenetic analysis suggested possible transmission of the emerging multidrug resistant (MDR) Kentucky ST198 and serotype Schwarzengrund from chicken to human. These results stress the need for active surveillance of Salmonella and AMR in order to address invasive salmonellosis caused by nontyphoidal Salmonella strains and other important bacterial diseases in sSA., Competing Interests: The authors have declared that no competing interests exist.

The increase in antimicrobial-resistant (AMR) foodborne pathogens, including E. coli and Salmonella in animals, humans, and the environment, is a growing public health concern. Among animals, cattle, pigs, and chicken are reservoirs of these pathogens worldwide. There is a knowledge gap on the prevalence and AMR of foodborne pathogens in small ruminants (i.e., sheep and goats). This study investigates the prevalence and antimicrobial resistance of extended-spectrum beta-lactamase (ESBL) E. coli and Salmonella from sheep and their abattoir environment in North Carolina. We conducted a year-round serial cross-sectional study and collected a total of 1128 samples from sheep (n = 780) and their abattoir environment (n = 348). Sheep samples consisted of feces, cecal contents, carcass swabs, and abattoir resting area feces. Environmental samples consisted of soil samples, lairage swab, animal feed, and drinking water for animals. We used CHROMAgar EEC with 4 μg/ml of Cefotaxime for isolating ESBL E. coli, and ESBL production was confirmed by double-disk diffusion test. Salmonella was isolated and confirmed using standard methods. All of the confirmed isolates were tested against a panel of 14 antimicrobials to elucidate susceptibility profiles. The prevalence of ESBL E. coli and Salmonella was significantly higher in environmental samples (47.7% and 65.5%) compared to the sheep samples (19.5% and 17.9%), respectively (P < 0.0001). We recovered 318 ESBL E. coli and 368 Salmonella isolates from sheep and environmental samples. More than 97% (310/318) of ESBL E. coli were multidrug-resistant (MDR; resistant to ≥3 classes of antimicrobials). Most Salmonella isolates (77.2%, 284/368) were pansusceptible, and 10.1% (37/368) were MDR. We identified a total of 24 different Salmonella serotypes by whole genome sequencing (WGS). The most common serotypes were Agona (19.8%), Typhimurium (16.2%), Cannstatt (13.2%), Reading (13.2%), and Anatum (9.6%). Prevalence and percent resistance of ESBL E. coli and Salmonella isolates varied significantly by season and sample type (P < 0.0001). The co-existence of ESBL E. coli in the same sample was associated with increased percent resistance of Salmonella to Ampicillin, Chloramphenicol, Sulfisoxazole, Streptomycin, and Tetracycline. We presumed that the abattoir environment might have played a great role in the persistence and dissemination of resistant bacteria to sheep as they arrive at the abattoir. In conclusion, our study reaffirms that sheep and their abattoir environment act as important reservoirs of AMR ESBL E. coli and MDR Salmonella in the U.S. Further studies are required to determine associated public health risks., (Copyright © 2021. Published by Elsevier B.V.)

For decades, Salmonella Typhimurium and Salmonella Enteritidis have prevailed in several countries as agents of salmonellosis outbreaks. In Brazil, the largest exporter of poultry meat, relatively little attention has been paid to infrequent serovars. Here, we report the emergence and characterization of rare serovars isolated from food and related sources collected between 2014 and 2016 in Brazil. Twenty-two Salmonella enterica isolates were analyzed through the use of whole-genome sequencing (WGS) and clustered regularly interspaced short palindromic repeats (CRISPR) genotyping. These isolates were classified into 10 infrequent serovars, including S. Abony, S. Isangi, S. Rochdale, S. Saphra, S. Orion, S. Ouakam, S. Grumpensis, S. Carrau, S. Abaetetuba, and S. Idikan. The presence of six antimicrobial resistance (AMR) genes, qnrB19, bla CMY-2 , tetA, aac(6')-Iaa, sul2 and fosA7, which encode resistance to quinolones, third-generation cephalosporin, tetracycline, aminoglycoside, sulfonamide and fosfomycin, respectively, were confirmed by WGS. All S. Isangi harbored qnrB19 with conserved genomic context across strains, while S. Abony harbored bla CMY-2 . Twelve (54.5%) strains displayed chromosomal mutations in parC (Thr57→Ser). Most serovars were classified as independent lineages, except S. Abony and S. Abaetetuba, which phylogenetically nested with Salmonella strains from different countries. CRISPR analysis revealed that the spacer content was strongly correlated with serovar and multi-locus sequence type for all strains, independently confirming the observed phylogenetic patterns, and highlighting the value of CRISPR-based genotyping for Salmonella. These findings add valuable information to the epidemiology of S. enterica in Brazil, where the emergency of antibiotic-resistant Salmonella continues to evolve., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

International lineages, such as Salmonella Typhimurium sequence type (ST) 19, are most often associated with foodborne diseases and deaths in humans. In this study, we compared the whole-genome sequences of five S. Typhimurium strains belonging to ST19 recovered from clinical human stool samples in North Carolina, United States. Overall, S. Typhimurium strains displayed multidrug-resistant profile, being resistance to critically and highly important antimicrobials including ampicillin, ticarcillin/clavulanic acid, streptomycin and sulfisoxazole, chloramphenicol, tetracycline, respectively. Interestingly, all S. Typhimurium strains carried class 1 integron (intl1) and we were able to describe two genomic regions surrounding blaCARB-2 gene, size 4,062 bp and 4,422 bp for S. Typhimurium strains (HS5344, HS5437, and HS5478) and (HS5302 and HS5368), respectively. Genomic analysis for antimicrobial resistome confirmed the presence of clinically important genes, including blaCARB-2, aac(6')-Iaa, aadA2b, sul1, tetG, floR, and biocide resistance genes (qacEΔ1). S. Typhimurium strains harbored IncFIB plasmid containing spvRABCD operon, as well as rck and pef virulence genes, which constitute an important apparatus for spreading the virulence plasmid. In addition, we identified several virulence genes, chromosomally located, while the phylogenetic analysis revealed clonal relatedness among these strains with S. enterica isolated from human and non-human sources obtained in European and Asian countries. Our results provide new insights into this unusual class 1 integron in virulent S. Typhimurium strains that harbors a pool of genes acting as potential hotspots for horizontal gene transfer providing readily adaptation to new surrounds, as well as being crucially required for virulence in vivo. Therefore, continuous genomic surveillance is an important tool for safeguarding human health., Competing Interests: The authors have declared that no competing interests exist.

The increasing prevalence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli is worrisome. Coordinated efforts to better understand global prevalence and risk factors are needed. Developing lower- and middle-income countries need reliable, readily available, and cost-effective solutions for detecting ESBL E. coli to contribute to global surveillance. We evaluated MacConkey agar supplemented with ceftriaxone or cefotaxime as a screening method for accurately detecting and quantifying potential ESBL E. coli MacConkey agar from eight manufacturers, representing seven countries, was prepared with 2 or 4 μg/ml ceftriaxone or cefotaxime. Four E. coli strains (NC11, ATCC 25922, CM-13457, and CM-10455) and one Klebsiella pneumoniae strain (CM-11073) were grown overnight, serially diluted, and plated in triplicate for enumeration on all medium combinations. After recovery was assessed, US-1 MacConkey agar with cefotaxime was used to further evaluate the reproducibility and detection of potential ESBL E. coli from poultry cecal ( n  = 30) and water ( n  = 30) samples. Results indicated the recovery of E. coli 13457 from four MacConkey agar manufacturers was reduced by up to 4 log CFU/ml, and phenotypic differences in colony size and color were apparent for each manufacturer for control E. coli strains. A true ESBL, NC11, was not reduced with 4 μg/ml cefotaxime. From ceca and water, potential ESBL E. coli isolates were only confirmed from MacConkey agar with 4 μg/ml cefotaxime, where 45% and 16.6% of E. coli isolates phenotypically expressed ESBL production. The quality and reproducibility of MacConkey agar varied by manufacturer, which suggests that a single manufacturer and medium type should be selected for global monitoring efforts so that training and interpretation can be standardized., (Copyright © 2020 American Society for Microbiology.)

Multidrug-resistant (MDR) Salmonella enterica has been deemed a high-priority pathogen by the World Health Organization. Two hundred and sixty-four Salmonella enterica isolates recovered over a 16-year period (2000 to 2016) from the poultry and swine production chains, in Brazil, were investigated by whole-genome sequencing (WGS). Most international lineages belonging to 28 serovars, including, S. enterica serovars S. Schwarzengrund ST96, S. Typhimurium ST19, S. Minnesota ST548, S. Infantis ST32, S. Heidelberg ST15, S. Newport ST45, S. Brandenburg ST65 and S. Kentucky ST198 displayed MDR and virulent genetic backgrounds. In this regard, resistome analysis revealed presence of qnrE1 (identified for the first time in S. Typhimurium from food chain), qnrB19, qnrS1, bla CTX-M-8 , bla CTX-M-2 and bla CMY-2 genes, as well as gyrA mutations; whereas ColpVC, IncHI2A, IncHI2, IncFIA, Incl1, IncA/C2, IncR, IncX1 and po111 plasmids were detected. In addition, phylogenetic analysis revealed multiple independent lineages such as S. enterica serovars S. Infantis, S. Schwarzengrund, S. Minnesota, S. Kentucky and S. Brandenburg. In brief, ocurrence and persistence of international lineages of S. enterica serovars in food production chain is supported by conserved genomes and wide virulome and resistome.

A colistin-resistant Salmonella enterica 4, [5],12:i:- sequence type (ST) 34 harbouring mcr-3.1 was recovered from a patient who travelled to China 2 weeks prior to diarrhoea onset. Genomic analysis revealed the presence of the mcr-3.1 gene located in the globally disseminated IncHI2 plasmid, highlighting the intercontinental dissemination of the colistin-resistant S. enterica 4, [5],12:i:- ST34 pandemic clone.

Enterobacteriaceae producing β-lactamases have spread rapidly worldwide and pose a serious threat to human-animal-environment interface. In this study, we present the presence of Salmonella enterica (1.3%) and commensal Escherichia coli (96.3%) isolated from 400 environmental fecal dairy cattle samples over 20 farms in Uganda. Among E. coli isolates, 21% were resistant to at least one antimicrobial tested and 7% exhibited multidrug resistance. Four E. coli isolates displayed extended-spectrum beta-lactamase (ESBL)-producing genes, including bla CTX-M-15 (n = 2/4), bla CTX-M-27 (n = 1/4), bla SHV-12 (n = 1/4), and bla TEM-1B (n = 2/4). Whole genome sequencing confirmed the presence of the plasmid-mediated quinolone resistance qnrS1 gene among three ESBL isolates. No statistically significant differences in seasonal prevalence for E. coli and S. enterica among dairy cattle sampling periods were observed. Furthermore, to our knowledge, this is the first report of E. coli carrying bla CTX-M-15 , bla CTX-M-27 , bla SHV-12 , or qnrS1 isolated from dairy cattle in Uganda. We conclude that the presence of globally disseminated bla CTX-M-15 and bla CTX-M-27 warrants further study to prevent further spread. In addition, the presence of fluoroquinolone resistant ESBL-producing E. coli on dairy farms highlights the potential risk among the human-livestock-environment interaction. This study can be used as a baseline for implementation of a more robust national integrated surveillance system throughout Uganda.

As Salmonella enterica is an important pathogen of food animals, surveillance programmes for S. enterica serovars have existed for many years in the United States. Surveillance programmes serve many purposes, one of which is to evaluate alterations in the prevalence of serovars that may signal changes in the ecology of the target organism. The primary aim of this study was to evaluate changes in the proportion of S. enterica serovars isolated from swine over a near 20-year observation period (1997-2015) using four longitudinal data sets from different food animal species. The secondary aim was to evaluate correlations between changes in S. enterica serovars frequently recovered from food animals and changes in S. enterica serovars associated with disease in humans. We found decreasing proportions of S. enterica serovar Typhimurium, serovar Derby and serovar Heidelberg and increasing proportions of S. enterica serovar 4,[5],12:i:-, serovar Infantis and serovar Johannesburg in swine over time. We also found positive correlations for the yearly changes in S. enterica serovar 4,[5],12:i:-, serovar Anatum and serovar Johannesburg between swine and human data; in S. enterica Worthington between avian and human data; and in S. enterica serovar 4,[5],12:i:- between bovine and human data. We found negative correlations for the yearly changes in S. enterica serovar 4,[5],12:i:- and serovar Johannesburg between avian and human data., (© 2018 Blackwell Verlag GmbH.)

Background: Ceftriaxone resistance in Salmonella is a serious public health threat. Ceftriaxone is commonly used to treat severe Salmonella infections, especially in children. Identifying the sources and drivers of ceftriaxone resistance among nontyphoidal Salmonella is crucial., Materials and Methods: The National Antimicrobial Resistance Monitoring System (NARMS) tracks antimicrobial resistance in foodborne and other enteric bacteria from humans, retail meats, and food animals. We examined NARMS data reported during 1996-2013 to characterize ceftriaxone-resistant Salmonella infections in humans. We used Spearman rank correlation to examine the relationships between the annual percentage of ceftriaxone resistance among Salmonella isolates from humans with isolates from retail meats and food animals., Results: A total of 978 (2.9%) of 34,100 nontyphoidal Salmonella isolates from humans were resistant to ceftriaxone. Many (40%) ceftriaxone-resistant isolates were from children younger than 18 years. Most ceftriaxone-resistant isolates were one of three serotypes: Newport (40%), Typhimurium (26%), or Heidelberg (12%). All were resistant to other antimicrobials, and resistance varied by serotype. We found statistically significant correlations in ceftriaxone resistance between human and ground beef Newport isolates (r = 0.83), between human and cattle Typhimurium isolates (r = 0.57), between human and chicken Heidelberg isolates (r = 0.65), and between human and turkey Heidelberg isolates (r = 0.67)., Conclusions: Ceftriaxone resistance among Salmonella Newport, Typhimurium, and Heidelberg isolates from humans strongly correlates with ceftriaxone resistance in isolates from ground beef, cattle, and poultry, respectively. These findings support other lines of evidence that food animals are important reservoirs of ceftriaxone-resistant Salmonella that cause human illness in the United States.

The objective of this study was to determine the prevalence and characteristics of Salmonella spp. isolated from feces of cattle in feedlots in the United States. Fecal samples were collected from up to three pens of cattle in each of 68 feedlots in 12 states. Samples included up to 25 individual fecal pats from the pen floors and up to five composite samples from the floors of the same pens. The prevalence of Salmonella-positive samples was 9.1% (460/5050) and 11.3% (114/1009) for individual and composite samples, respectively. The prevalences of Salmonella at the pen level were 35.6% (72/202) and 22.8% (46/202) for individual and composite samples, respectively. Dietary factors, including inclusion of cottonseed hulls, coccidiostats, and antimicrobial drugs, were associated with differences in prevalence of Salmonella isolation. Overall, 32 serotypes of Salmonella were identified, but six serotypes accounted for 69.1% (495/716) of the isolates. Nearly two-thirds (64.7%, 44/68) of feedlots had at least one positive sample. All isolates were evaluated for susceptibility to a panel of 15 antimicrobial drugs. Most isolates (74.4%, 533/716) were susceptible to all antimicrobial drugs in the panel. When resistance was detected, it was most commonly to tetracycline (21.7%, 155/716 of isolates) or sulfisoxazole (12.4%, 89/716 of isolates). Less than 10% of the isolates were resistant to any other antimicrobials in the panel. The results of this study indicate that the prevalence of Salmonella in individual fecal samples was less than 10%, but that Salmonella is widely distributed among feedlot cattle. Furthermore, when Salmonella is present in feedlot cattle, there is a low occurrence of antimicrobial resistance with the exception of tetracycline and sulfisoxazole. More research is indicated to understand the ecology of Salmonella and antimicrobial resistance, when present, in cattle-feeding operations.

A challenge to the development of foodborne illness prevention measures is determining the sources of enteric illness. Microbial subtyping source-attribution models attribute illnesses to various sources, requiring data characterizing bacterial isolate subtypes collected from human and food sources. We evaluated the use of antimicrobial resistance data on isolates of Salmonella enterica serotype Hadar, collected from ill humans, food animals, and from retail meats, in two microbial subtyping attribution models. We also compared model results when either antimicrobial resistance or pulsed-field gel electrophoresis (PFGE) patterns were used to subtype isolates. Depending on the subtyping model used, 68-96% of the human infections were attributed to meat and poultry food products. All models yielded similar outcomes, with 86% [95% confidence interval (CI) 80-91] to 91% (95% CI 88-96) of the attributable infections attributed to turkey, and 6% (95% CI 2-10) to 14% (95% CI 8-20) to chicken. Few illnesses (<3%) were attributed to cattle or swine. Results were similar whether the isolates were obtained from food animals during processing or from retail meat products. Our results support the view that microbial subtyping models are a flexible and robust approach for attributing Salmonella Hadar.

Clostridium difficile is commonly associated with a spectrum of disease in humans referred to as C. difficile-associated disease (CDAD) and use of antimicrobials is considered a risk factor for development of disease in humans. C. difficile can also inhabit healthy food animals and transmission to humans is possible. As a result of the complexity and cost of testing, C. difficile is rarely tested for antimicrobial susceptibility. A total of 376 C. difficile strains (94 each from swine and dairy feces, and 188 from beef cattle feces) were isolated from healthy food animals on farms during studies conducted by the National Animal Health Monitoring System. Using the Etest (AB Biodisk, Solna, Sweden), samples were tested for susceptibility to nine antimicrobials implicated as risk factors for CDAD (linezolid, amoxicillin-clavulanic acid, ampicillin, clindamycin, erythromycin, levofloxacin, metronidazole, rifampicin, and vancomycin). Vancomycin was active against all isolates of C. difficile (MIC90=3.0μg/ml) while almost all isolates (n=369; 98.1%) were resistant to levofloxacin. With the exception of vancomycin, resistance varied by animal species as follows: linezolid (8.5% resistance among swine versus 2.1 and 1.1% resistance among dairy and beef, respectively), clindamycin (56.4% resistance among swine versus 80% and 90.9% resistance among dairy and beef, respectively), and rifampicin (2.1% and 0% resistance among swine and dairy cattle isolates, respectively versus 14.3% resistance among beef isolates). Regardless of species, multiple drug resistance was observed most often to combinations of clindamycin and levofloxacin (n=195; 51.9%) and ampicillin, clindamycin and levofloxacin (n=41; 10.9%). The reason for the variability of resistance between animal species is unknown and requires further research., (Published by Elsevier B.V.)

Salmonella Kentucky has become the predominant serovar recovered from broilers slaughtered in the United States, and the prevalence of antimicrobial resistance (AMR) has increased dramatically in this serovar. Relationships between AMR, genotype, and plasmid replicon types were characterized for 600 Salmonella Kentucky isolates recovered from chicken carcasses from 2004 to 2013. Pulsed-field gel electrophoresis cluster analysis revealed 112 unique types sharing 79% similarity. Over half of the isolates studies were assigned to two large clusters (unique restriction patterns) consisting of 190 (A) and 151 (B) isolates. The remaining (n = 259) more diverse isolates (110 unique patterns) shall be designated cluster C for discussion. Clusters A had significantly more (p < 0.05) isolates resistant to streptomycin (68.4%) and tetracycline (91.6%) compared to cluster C (50.6% and 40.9% to streptomycin and tetracycline, respectively) or cluster B, which had the least (p < 0.05) resistance (11.9% and 13.2% to streptomycin and tetracycline, respectively). In addition, there was segregation of plasmid replicon types among clusters. Cluster A had significantly more (p < 0.05) replicon type FIB (90.5%) compared to cluster C (37.1%), which had significantly more compared to cluster B (10.6%). Cluster B had significantly more (p < 0.05) replicon type I1 (87.4%) compared to cluster C (68.7%), which had significantly more (p < 0.05) compared to cluster A (32.6%). Cluster C harbored significantly more (p < 0.05) HI2 replicon type (18.1%) compared to clonal clusters A (1.6%) or B (1.3%). The prevalence of plasmid replicon type A/C did not differ among clusters (A, 0.5%; B, 2.0%; C, 0.4%). Both streptomycin and tetracycline resistance were significantly linked (p < 0.05) to plasmid replicon type FIB. In addition, replicon type HI2 was also significantly linked (p < 0.05) to streptomycin resistance. We conclude that the dramatic increase in streptomycin and tetracycline resistance among Salmonella Kentucky isolated from poultry is due to the expansion of strains harboring plasmid replicon types FIB and HI2.

The housing of laying hens is important for social, industrial, and regulatory aspects. Many studies have compared hen housing systems on the research farm, but few have fully examined commercial housing systems and management strategies. The current study compared hens housed in commercial cage-free aviary, conventional cage, and enriched colony cage systems. Environmental and eggshell pool samples were collected from selected cages/segments of the housing systems throughout the production cycle and monitored for Salmonella and Campylobacter prevalence. At 77 wk of age, 120 hens per housing system were examined for Salmonella and Campylobacter colonization in the: adrenal glands, spleen, ceca, follicles, and upper reproductive tract. All isolates detected from environmental swabs, eggshell pools, and tissues were identified for serotype. Two predominant Salmonella were detected in all samples:S.Braenderup andS.Kentucky.Campylobacter coli and C. jejuni were the only Campylobacter detected in the flocks. Across all housing systems, approximately 7% of hens were colonized with Salmonella, whereas >90% were colonized with Campylobacter Salmonella Braenderup was the isolate most frequently detected in environmental swabs (P<0.0001) and housing system impacted Salmonella spp. shedding (P<0.0001).Campylobacter jejuni was the isolate most frequently found in environmental swabs (P<0.01), while housing system impacted the prevalence of C. coli and jejuniin ceca (P<0.0001). The results of this study provide a greater understanding of the impact of hen housing systems on hen health and product safety. Additionally, producers and academia can utilize the findings to make informed decisions on hen housing and management strategies to enhance hen health and food safety., (Published by Oxford University Press on behalf of Poultry Science Association 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

Salmonella is a major cause of foodborne illness and can cause clinical disease in animals. Understanding the on-farm ecology of Salmonella will be helpful in decreasing the risk of foodborne transmission. An objective of this study was to determine the prevalence of Salmonella among fecal samples collected on sheep operations in the United States. Another objective was to compare the use of composite fecal samples with fecal samples collected from individual sheep as a tool for screening sheep flocks for Salmonella. Sheep fecal samples (individual and composite) were collected on operations in 22 states. Salmonella isolates were characterized with regard to species, serotype, and antimicrobial susceptibility profile. Most operations (72.1%) had at least one positive sample and overall 26.9% of samples were positive. The percentage of positive samples varied by animal age class. Composite and individual samples gave similar results. The majority of the isolates (94%) were Salmonella enterica subspecies diarizonae serotype 61:-:1,5,7. Nearly all of the isolates (91.2%) tested for antimicrobial susceptibility were susceptible to all antimicrobials in the panel. The findings suggest that salmonellae typically associated with foodborne disease transmission are infrequently found on sheep operations in the United States.

Salmonella enterica is one of the most common causes of bacterial foodborne illness in the United States. Although most Salmonella infections are self-limiting, antimicrobial treatment of invasive salmonellosis is critical. The primary antimicrobial treatment options include fluoroquinolones or extended-spectrum cephalosporins, and resistance to these antimicrobial drugs may complicate treatment. At present, S. enterica is composed of more than 2,600 unique serotypes, which vary greatly in geographic prevalence, ecological niche, and the ability to cause human disease, and it is important to understand and mitigate the source of human infection, particularly when antimicrobial resistance is found. In this study, we identified and characterized 19 S. enterica serotype Albert isolates collected from food animals, retail meat, and humans in the United States during 2005 to 2013. All five isolates from nonhuman sources were obtained from turkeys or ground turkey, and epidemiologic data suggest poultry consumption or live-poultry exposure as the probable source of infection. S. enterica serotype Albert also appears to be geographically localized to the midwestern United States. All 19 isolates displayed multidrug resistance, including decreased susceptibility to fluoroquinolones and resistance to extended-spectrum cephalosporins. Turkeys are a likely source of multidrug-resistant S. enterica serotype Albert, and circulation of resistance plasmids, as opposed to the expansion of a single resistant strain, is playing a role. More work is needed to understand why these resistance plasmids spread and how their presence and the serotype they reside in contribute to human disease., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

Escherichia albertii is a recently described species that has been associated with gastroenteritis in humans and with healthy and ill birds. Most recently, it has been identified as the causative agent in a food-borne outbreak in Japan. The distribution and clinical importance of E. albertii are not well studied because its importance is unclear. Culture methods for clinical isolation frequently miss E. albertii or incorrectly identify it as Shigella spp., Escherichia coli, or Hafnia alvei. This study was designed to determine if E. albertii could be recovered from chicken carcass rinses collected at slaughter during a 1-year period from November 2009 until October 2010. Colonies were isolated from chicken carcass rinses and tested by PCR for the presence or absence of clpX, lysP, mdh, intimin (eae), Shiga toxins 1 and 2 (stx1, stx2, and stx2f), heat-stable enterotoxin A (staA), and cytolethal distending toxins 1 and 2 (cdtB) genes. Sixty-five isolates were analyzed by sequencing a section of the rpoB gene. Analysis of the rpoB gene sequences revealed 14 fixed differences between E. albertii and other, closely related organisms. The fixed differences found in the rpoB gene could aid in future discrimination of E. albertii from closely related bacteria., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

Hen housing for commercial egg production continues to be a societal and regulatory concern. Controlled studies have examined various aspects of egg safety, but a comprehensive assessment of commercial hen housing systems in the US has not been conducted. The current study is part of a holistic, multidisciplinary comparison of the diverse aspects of commercial conventional cage, enriched colony cage, and cage-free aviary housing systems and focuses on environmental and egg microbiology. Environmental swabs and eggshell pools were collected from all housing systems during 4 production periods. Total aerobes and coliforms were enumerated, and the prevalence of Salmonella and Campylobacter spp. was determined. Environmental aerobic and coliform counts were highest for aviary drag swabs (7.5 and 4.0 log cfu/mL, respectively) and enriched colony cage scratch pad swabs (6.8 and 3.8 log cfu/mL, respectively). Aviary floor and system wire shell pools had the greatest levels of aerobic contamination for all eggshell pools (4.9 and 4.1 log cfu/mL, respectively). Hens from all housing systems were shedding Salmonella spp. (89-100% of manure belt scraper blade swabs). The dry belt litter removal processes for all housing systems appear to affect Campylobacter spp. detection (0-41% of manure belt scraper blade swabs) considering detection of Campylobacter spp. was much higher for other environmental samples. Aviary forage area drag swabs were 100% contaminated with Campylobacter spp., whereas enriched colony cage scratch pads had a 93% positive rate. There were no differences in pathogen detection in the shell pools from the 3 housing systems. Results indicate egg safety is enhanced when hens in alternative housing systems use nest boxes. Additionally, current outcomes indicate the use of scratch pads in hen housing systems needs to be more thoroughly investigated for effects on hen health and egg safety., (© The Author 2015. Published by Oxford University Press on behalf of Poultry Science Association.)

Unlabelled: Antimicrobial-resistant staphylococci have been associated with wounded or ill companion animals, but little is known about the prevalence of resistant staphylococci among healthy animals. In this study, 276 healthy dogs and cats from veterinary clinics were tested for the presence of antimicrobial-resistant Staphylococcus spp. Isolates were tested for antimicrobial susceptibility and the presence of select resistance genes, and typed using Pulsed-Field Gel Electrophoresis (PFGE). Staphylococcus aureus and Staphylococcus pseudintermedius were also characterized using multilocus sequence typing (MLST), spa typing and SCCmec typing. Approximately 5% (14/276) of the animals were positive by enrichment for five species of staphylococci [Staph. aureus (n = 11), Staph. pseudintermedius (n = 4), Staphylococcus sciuri (n = 6), Staphylococcus simulans (n = 1) and Staphylococcus warneri (n = 1)]. Seventy-eight per cent (18/23) of staphylococci were resistant to oxacillin and also multidrug resistant (resistance to ≥ 2 antimicrobials). All Staph. aureus isolates were mecA+ and blaZ+, SCCmec type II, spa type t002, ST5 and clonal using PFGE. Staphylococcus pseudintermedius were SCCmec type IV or V, spa type t06 and ST170; two of the isolates were pvl(+) . These results suggest that healthy companion animals may be a reservoir of multidrug-resistant staphylococci, which may be transferred to owners and others who handle companion animals., Significance and Impact of the Study: In this study, antimicrobial-resistant coagulase-negative and coagulase-positive staphylococci were isolated from various body sites on healthy dogs and cats. Resistance to 14 antimicrobials was observed including resistance to oxacillin; the majority of staphylococci were also multidrug resistant. Results from this study suggest that healthy dogs and cats may act as reservoirs of antimicrobial-resistant bacteria that may be transferred to people by simple interaction with the animals. Such carriage poses an underlying risk of infection, which should be considered during handling of healthy dogs and cats by pet owners and veterinary personnel., (© 2014 The Society for Applied Microbiology. This article has been contributed to by US Government employees and their work is in the public domain in the USA.)

Salmonella is an important cause of foodborne illness; however, identifying the source of these infections can be difficult. This is especially true for Salmonella serotype Typhimurium, which is found in diverse agricultural niches. Extended-spectrum cephalosporins (ESC) are one of the primary treatment choices for complicated Salmonella infections. In Salmonella, ESC resistance in the United States is mainly mediated by blaCMY genes carried on various plasmids. In this study, we examined whether the characterization of blaCMY plasmids, along with additional information, can help us identify potential sources of infection by Salmonella, and used serotype Typhimurium as a model. In the United States, monitoring of retail meat, food animals, and ill persons for antimicrobial-resistant Salmonella is conducted by the National Antimicrobial Resistance Monitoring System. In 2008, 70 isolates (70/581; 12.0%) (34 isolates from retail meat, 23 food animal, and 13 human) were resistant to ceftriaxone and amoxicillin/clavulanic acid. All were polymerase chain reaction (PCR)-positive for blaCMY and 59/70 (84.3%) of these genes were plasmid encoded. PCR-based replicon typing identified 42/59 (71.2%) IncI1-blaCMY plasmids and 17/59 (28.8%) IncA/C-blaCMY plasmids. Isolates from chickens or chicken products with blaCMY plasmids primarily had IncI1-blaCMY plasmids (37/40; 92.5%), while all isolates from cattle had IncA/C-blaCMY plasmids. Isolates from humans had either IncA/C- blaCMY (n=8/12; [66.7%]) or IncI1- blaCMY (n=4/12 [33.3%]) plasmids. All of the IncI1-blaCMY plasmids were ST12 or were closely related to ST12. Antimicrobial susceptibility patterns (AST) and pulsed-field gel electrophoresis (PFGE) patterns of the isolates were also compared and differences were identified between isolate sources. When the source of a Typhimurium outbreak or sporadic illness is unknown, characterizing the outbreak isolate's blaCMY plasmids, AST, and PFGE patterns may help identify it.

Postchill neck skin maceration (NSM) and whole-carcass rinsing (WCR) are frequently used methods to detect salmonellae from processed broilers. These are practical, nondestructive methods, but they are insensitive and may result in false negatives (20 to 40%). Neck skin samples comprise only 4% of the skin from the broiler carcass by weight, while WCR will not detect firmly attached Salmonella organisms and only 7.5% of the rinsate is utilized. Whole-carcass enrichment (WCE) involves incubation of the whole carcass overnight in a preenrichment broth and can recover as few as 8 inoculated Salmonella cells per carcass. The objective of this study was to use NSM, WCR, and WCE sampling to detect naturally occurring Salmonella from the same commercially processed broiler either prechill or postchill. Ten carcasses were obtained prechill and another 10 postchill on each of two replicate days from each of two commercial processing plants. From each carcass, 8.3 g of neck skin was sampled, and then the carcass was rinsed with 400 ml of 1% buffered peptone water. Thirty milliliters was removed and incubated (WCR), and the remaining 370 ml of broth and the carcass were incubated at 37°C for 24 h (WCE). Overall, Salmonella organisms were detected on 21, 24, and 32 of 40 prechill carcasses by NSM, WCR, and WCE, respectively, while 2, 2, and 19 of 40 postchill carcasses were positive by the respective methods. Prechill carcasses were 64% (77 of 120) positive for Salmonella, while postchill carcasses were 19% (23 of 120) positive. Commercial processing reduced the positive-sample prevalence by 45%. Salmonella organisms were detected on 20% (24 of 120) of the samples from plant 1 and 63% (76 of 120) of the carcasses from plant 2. This study demonstrates significant differences in the results for Salmonella prevalence among sampling methods both before and after immersion chilling, as well as between processing plants on days that samples were taken.

Salmonellosis is one of the most important foodborne diseases affecting humans. To characterize the relationship between Salmonella causing human infections and their food animal reservoirs, we compared pulsed-field gel electrophoresis (PFGE) and antimicrobial susceptibility patterns of non-typhoidal Salmonella isolated from ill humans in Pennsylvania and from food animals before retail. Human clinical isolates were received from 2005 through 2011 during routine public health operations in Pennsylvania. Isolates from cattle, chickens, swine and turkeys were recovered during the same period from federally inspected slaughter and processing facilities in the northeastern United States. We found that subtyping Salmonella isolates by PFGE revealed differences in antimicrobial susceptibility patterns and, for human Salmonella, differences in sources and invasiveness that were not evident from serotyping alone. Sixteen of the 20 most common human Salmonella PFGE patterns were identified in Salmonella recovered from food animals. The most common human Salmonella PFGE pattern, Enteritidis pattern JEGX01.0004 (JEGX01.0003ARS), was associated with more cases of invasive salmonellosis than all other patterns. In food animals, this pattern was almost exclusively (99%) found in Salmonella recovered from chickens and was present in poultry meat in every year of the study. Enteritidis pattern JEGX01.0004 (JEGX01.0003ARS) was associated with susceptibility to all antimicrobial agents tested in 94.7% of human and 97.2% of food animal Salmonella isolates. In contrast, multidrug resistance (resistance to three or more classes of antimicrobial agents) was observed in five PFGE patterns. Typhimurium patterns JPXX01.0003 (JPXX01.0003 ARS) and JPXX01.0018 (JPXX01.0002 ARS), considered together, were associated with resistance to five or more classes of antimicrobial agents: ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline (ACSSuT), in 92% of human and 80% of food animal Salmonella isolates. The information from our study can assist in source attribution, outbreak investigations, and tailoring of interventions to maximize their impact on prevention.

Non-Typhi Salmonella cause over 1.7 million cases of gastroenteritis in North America each year, and food-animal products are commonly implicated in human infections. For invasive infections, antimicrobial therapy is indicated. In North America, the antimicrobial susceptibility of Salmonella is monitored by the U.S. National Antimicrobial Resistance Monitoring System (NARMS) and The Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS). In this study, we determined the susceptibility to cephalosporins by broth microdilution among 5,041 non-Typhi Salmonella enterica isolated from food animals, retail meats, and humans. In the United States, 109 (4.6%) of isolates collected from humans, 77 (15.7%) from retail meat, and 140 (10.6%) from food animals displayed decreased susceptibility to cephalosporins (DSC). Among the Canadian retail meat and food animal isolates, 52 (13.0%) and 42 (9.4%) displayed DSC. All isolates displaying DSC were screened for β-lactamase genes (bla(TEM), bla(SHV), bla(CMY), bla(CTX-M), and bla(OXA-1)) by polymerase chain reaction. At least one β-lactamase gene was detected in 74/109 (67.9%) isolates collected from humans, and the bla(CMY) genes were most prevalent (69/109; 63.3%). Similarly, the bla(CMY) genes predominated among the β-lactamase-producing isolates collected from retail meats and food animals. Three isolates from humans harbored a bla(CTX-M-15) gene. No animal or retail meat isolates harbored a bla(CTX-M) or bla(OXA-1) gene. A bla(TEM) gene was found in 5 human, 9 retail meat, and 17 animal isolates. Although serotype distributions varied among human, retail meat, and animal sources, overlap in bla(CMY)-positive serotypes across sample sources supports meat and food-animal sources as reservoirs for human infection.

Salmonella enterica is a prevalent foodborne pathogen that can carry multidrug resistance (MDR) and pose a threat to human health. Identifying the genetics associated with MDR in Salmonella isolated from animals, foods, and humans can help determine sources of MDR in food animals and their impact on humans. S. enterica serovars most frequently carrying MDR from healthy animals, retail meats, and human infections in the United States and Canada were identified and isolates resistant to the largest number of antimicrobials were chosen. Isolates were from U.S. slaughter (n=12), retail (9), and humans (9), and Canadian slaughter (9), retail (9), and humans (8; total n=56). These isolates were assayed by microarray for antimicrobial resistance and MDR plasmid genes. Genes detected encoded resistance to aminoglycosides (alleles of aac, aad, aph, strA/B); beta-lactams (bla(TEM), bla(CMY), bla(PSE-1)); chloramphenicol (cat, flo, cmlA); sulfamethoxazole (sulI); tetracycline (tet(A, B, C, D) and tetR); and trimethoprim (dfrA). Hybridization with IncA/C plasmid gene probes indicated that 27/56 isolates carried one of these plasmids; however, they differed in several variable regions. Cluster analysis based on genes detected separated most of the isolates into two groups, one with IncA/C plasmids and one without IncA/C plasmids. Other plasmid replicons were detected in all but one isolate, and included I1 (25/56), N (23/56), and FIB (10/56). The presence of different mobile elements along with similar resistance genes suggest that these genetic elements may acquire similar resistance cassettes, and serve as multiple sources for MDR in Salmonella from food animals, retail meats, and human infections.

Campylobacter is an important human pathogen, and consumption of undercooked poultry has been linked to significant human illnesses. To reduce human illness, intervention strategies targeting Campylobacter reduction in poultry are in development. For more than a decade, there has been an ongoing national and international controversy about whether Campylobacter can pass from one generation of poultry to the next via the fertile egg. We recognize that there are numerous sources of Campylobacter entry into flocks of commercial poultry (including egg transmission), yet the environment is often cited as the only source. There has been an abundance of published research globally that refutes this contention, and this article lists and discusses many of them, along with other studies that support environment as the sole or primary source. One must remember that egg passage can mean more than vertical, transovarian transmission. Fecal bacteria, including Campylobacter, can contaminate the shell, shell membranes, and albumen of freshly laid fertile eggs. This contamination is drawn through the shell by temperature differential, aided by the presence of moisture (the "sweating" of the egg); then, when the chick emerges from the egg, it can ingest bacteria such as Campylobacter, become colonized, and spread this contamination to flock mates in the grow house. Improvements in cultural laboratory methods continue to advance our knowledge of the ecology of Campylobacter, and in the not-so-distant future, egg passage will not be a subject continuously debated but will be embraced, thus allowing the development and implementation of more effective intervention strategies.

The objectives of this study were to estimate the prevalence of Salmonella for individual, pooled, and composite fecal samples and to compare culture results from each sample type for determining herd Salmonella infection status and identifying Salmonella serovar(s). During the U.S. Department of Agriculture National Animal Health Monitoring System Dairy 2007 study, data and samples were collected from dairy operations in 17 major dairy states. As part of the study, composite fecal samples (six per operation) were collected from cow areas, such as holding pens, alleyways, and lagoons, where manure accumulates. Fecal samples also were collected from individual cows (35 per operation), and fecal sample pools were created by combining samples from 5 cows (7 per operation). A total of 1,541 composite fecal samples were collected from 260 operations in 17 states, and 406 (26.3%) of these samples were culture positive for Salmonella. Among the 116 operations for which all three sample types were obtained, 41.4% (48 operations) were Salmonella culture positive based on individual samples, 39.7% (46 operations) were positive based on pooled samples, and 49.1% (57 operations) were positive based on composite fecal samples. Relative to individual samples, the sensitivity of composite fecal samples for determining herd infection status was 85.4% and the sensitivity of pooled fecal samples was 91.7%. On 33.6% of operations (39 of 116), Salmonella was cultured from all three fecal sample types (individual, pooled, and composite), and 20 (51.3%) of these operations had exactly the same serovar in all three sample types. Use of composite fecal samples is less costly and time-consuming than use of individual or pooled samples and provides similar results for detecting the presence and identifying serovars of Salmonella in dairy herds. Therefore, composite sampling may be an appropriate alternative to culture of individual samples when assessing Salmonella status in dairy herds.

Multi-drug-resistant (MDR) bacteria in food animals are a potential problem in both animal and human health. In this study, MDR commensal Escherichia coli isolates from poultry were examined. Thirty-two E. coli isolates from broiler carcass rinses were selected based on their resistance to aminoglycosides, β-lactams, chloramphenicols, tetracyclines, and sulfonamide antimicrobials. Microarray analysis for the presence of antimicrobial resistance and plasmid genes identified aminoglycoside [aac(6), aac(3), aadA, aph, strA, and strB], β-lactam (bla(AmpC), bla(TEM), bla(CMY), and bla(PSE-1)), chloramphenicol (cat, flo, and cmlA), sulfamethoxazole (sulI and sulII), tetracycline [tet(A), tet(C), tet(D), and tetR], and trimethoprim (dfrA) resistance genes. IncA/C plasmid core genes were detected in 27 isolates, while IncHI1 plasmid genes were detected in one isolate, indicating the likely presence of these plasmids. PCR assays for 18 plasmid replicon types often associated with MDR in Enterobacteriaceae also detected one or more replicon types in all 32 isolates. Class I integrons were investigated by PCR amplification of the integrase I gene, intI1, and the cassette region flanked by conserved sequences. Twenty-five isolates were positive for the intI1 gene, and class I integrons ranging in size from ~1,000 to 3,300 bp were identified in 19 of them. The presence of class I integrons, IncA/C plasmid genes, and MDR-associated plasmid replicons in the isolates indicates the importance of these genetic elements in the accumulation and potential spread of antimicrobial resistance genes in the microbial community associated with poultry.

Salmonella enterica is one of the most common causes of foodborne illness in the United States. Although salmonellosis is usually self-limiting, severe infections typically require antimicrobial treatment, and ceftriaxone, an extended-spectrum cephalosporin (ESC), is commonly used in both adults and children. Surveillance conducted by the National Antimicrobial Resistance Monitoring System (NARMS) has shown a recent increase in ESC resistance among Salmonella Heidelberg isolated from food animals at slaughter, retail meat, and humans. ESC resistance among Salmonella in the United States is usually mediated by a plasmid-encoded bla(CMY) β-lactamase. In 2009, we identified 47 ESC-resistant bla(CMY)-positive Heidelberg isolates from humans (n=18), food animals at slaughter (n=16), and retail meats (n=13) associated with a spike in the prevalence of this serovar. Almost 90% (26/29) of the animal and meat isolates were isolated from chicken carcasses or retail chicken meat. We screened NARMS isolates for the presence of bla(CMY), determined whether the gene was plasmid-encoded, examined pulsed-field gel electrophoresis patterns to assess the genetic diversities of the isolates, and categorized the bla(CMY) plasmids by plasmid incompatibility groups and plasmid multi-locus sequence typing (pMLST). All 47 bla(CMY) genes were found to be plasmid encoded. Incompatibility/replicon typing demonstrated that 41 were IncI1 plasmids, 40 of which only conferred bla(CMY)-associated resistance. Six were IncA/C plasmids that carried additional resistance genes. pMLST of the IncI1-bla(CMY) plasmids showed that 27 (65.8%) were sequence type (ST) 12, the most common ST among bla(CMY)-IncI1 plasmids from Heidelberg isolated from humans. Ten plasmids had a new ST profile, ST66, a type very similar to ST12. This work showed that the 2009 increase in ESC resistance among Salmonella Heidelberg was caused mainly by the dissemination of bla(CMY) on IncI1 and IncA/C plasmids in a variety of genetic backgrounds, and is likely not the result of clonal expansion.

Campylobacter is a leading cause of foodborne illness in humans, and improving our understanding of the epidemiology of this organism is essential. The objective of this study was to identify the genes that discriminate isolates of C. jejuni by analysis with whole-genome DNA microarrays. Statistical analyses of whole-genome data from 95 geographically diverse cattle, chicken, and human C. jejuni isolates identified 142 most significant variable genes. Of this total, 125 (88%) belonged to genomic prophage and hypervariable regions. The significance of genomic prophage and hypervariable regions in determining C. jejuni isolate genomic diversity is emphasized by these results. These genes will be useful as biomarkers and components of genotyping systems for C. jejuni to improve our understanding of the epidemiology and population genetics of this major foodborne pathogen.

Concern about Salmonella contamination of food is compounded by fear that antimicrobials traditionally used to combat the infection will become useless due to rising antibiotic resistance. Livestock, in particular swine, often are blamed for illnesses caused by Salmonella and for increasing antibiotic resistance due to use of antibiotics in pigs. As part of the National Animal Health Monitoring System Swine 2000 and 2006 studies, swine fecal samples were cultured for Salmonella. These samples were collected from 123 operations in 17 states in 2000 and from 135 operations in 17 states in 2006. At each operation, 50 and 60 fecal samples were collected from late finisher pig pens in 2000 and 2006, respectively. Salmonella isolates were characterized to determine serogroup and serotype and were tested for susceptibility to a panel of 17 and 15 antimicrobial drugs in 2000 and 2006, respectively. A total of 5,470 and 7,788 samples were cultured for Salmonella in 2000 and 2006, respectively. Overall, 6.2% of the samples and 34.2% of the farms were positive for Salmonella in 2000. In 2006, 7.2% of the samples and 52.6% of the farms were positive. Salmonella Derby, Salmonella Typhimurium var. 5- (formerly Salmonella Typhimurium var. Copenhagen), and Salmonella Agona were the three serotypes most often recovered in both study years. The most common antimicrobial resistance pattern for Salmonella Derby in the two study years was resistance to streptomycin, sulfisoxazole, and tetracycline. Most isolates were resistant to tetracycline, sulfisoxazole, and streptomycin in both study years. The proportion of Salmonella isolates that were susceptible to all antimicrobials (pansusceptible) was 38.1% in 2000 and 20.4% in 2006. The proportion of Salmonella isolates that were resistant to three or more antimicrobials (multidrug resistant) was similar in 2000 and in 2006 (52.8 and 57.7%, respectively).

In the family Enterobacteriaceae, plasmids have been classified according to 27 incompatibility (Inc) or replicon types that are based on the inability of different plasmids with the same replication mechanism to coexist in the same cell. Certain replicon types such as IncA/C are associated with multidrug resistance (MDR). We developed a microarray that contains 286 unique 70-mer oligonucleotide probes based on sequences from five IncA/C plasmids: pYR1 (Yersinia ruckeri), pPIP1202 (Yersinia pestis), pP99-018 (Photobacterium damselae), pSN254 (Salmonella enterica serovar Newport), and pP91278 (Photobacterium damselae). DNA from 59 Salmonella enterica isolates was hybridized to the microarray and analyzed for the presence or absence of genes. These isolates represented 17 serovars from 14 different animal hosts and from different geographical regions in the United States. Qualitative cluster analysis was performed using CLUSTER 3.0 to group microarray hybridization results. We found that IncA/C plasmids occurred in two lineages distinguished by a major insertion-deletion (indel) region that contains genes encoding mostly hypothetical proteins. The most variable genes were represented by transposon-associated genes as well as four antimicrobial resistance genes (aphA, merP, merA, and aadA). Sixteen mercury resistance genes were identified and highly conserved, suggesting that mercury ion-related exposure is a stronger pressure than anticipated. We used these data to construct a core IncA/C genome and an accessory genome. The results of our studies suggest that the transfer of antimicrobial resistance determinants by transfer of IncA/C plasmids is somewhat less common than exchange within the plasmids orchestrated by transposable elements, such as transposons, integrating and conjugative elements (ICEs), and insertion sequence common regions (ISCRs), and thus pose less opportunity for exchange of antimicrobial resistance.

Multidrug-resistant (MDR) Salmonella enterica serovar Typhimurium is the most prevalent penta-resistant serovar isolated from animals by the U.S. National Antimicrobial Resistance Monitoring System. Penta-resistant isolates are often resistant to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline. To investigate MDR in Salmonella Typhimurium (including variant 5-), one isolate each from cattle, poultry, and swine with at least the ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline phenotype were selected for each year from 1997 to 2007 (n = 33) for microarray analysis of antimicrobial resistance, incompatibility IncA/C, and HI1 plasmid genes. Cluster analysis based on these data separated 31 of the isolates into two groups A and B (15 and 16 isolates, respectively). Isolates in group A were phage type DT104 or U302 and were mostly swine isolates (7/15). Genes detected included intI1, bla(PSE-1), floR, aadA, sulI, tet(G), and tetR, which are often found in Salmonella Genomic Island I. Isolates in group B had numerous IncA/C plasmid genes detected and were mostly cattle isolates (9/16). Genes detected included bla(CMY-2), floR, aac(3), aadA, aphA1, strA, strB, sulI, sulII, dfrA, dhf, tet(A)(B)(C)(D), and tetR, which are often found on MDR-AmpC IncA/C plasmids. The IncA/C replicon was also detected in all group B isolates. The two remaining isolates did not cluster with any others and both had many HI1 plasmid genes detected. Linkage disequilibrium analysis detected significant associations between plasmid replicon type, phage type, and animal source. These data suggest that MDR in Salmonella Typhimurium is associated with DT104/Salmonella Genomic Island I or IncA/C MDR-AmpC encoding plasmids and these genetic elements have persisted throughout the study period.