Search

Aims: To compare survival of Escherichia coli and faecal coliforms (FC) in bovine faeces deposited in a pasture or incubated in a controlled laboratory environment at temperatures within the same range. Methods and Results: Faecal samples from three cow herds were deposited as shaded and nonshaded cowpats in a field and incubated in a laboratory for one month at 21·1, 26·7 and 32·2°C. Both FC and E. coli concentrations increased as much as 1·5 orders of magnitude both in the field and in the laboratory during the 1st week and subsequently decreased. In shaded cowpats, the die-off of E. coli and FC was significantly slower, and the proportion of E. coli in FC was significantly larger as compared with nonshaded cowpats. The die-off was faster in the field than in the laboratory at similar temperatures. Conclusions: FC and E. coli die-off rates were substantially lower in laboratory conditions than in the field within the same range of temperatures. Significance and Impact of the Study: This study underscores the importance of field data on survival of manure-borne FC and E. coli, and indicates that laboratory die-off rates have to be corrected to be used for field condition simulations. [ABSTRACT FROM AUTHOR]

Aim: To test the hypothesis that Escherichia coli and enterococci bacteria have similar release rates and transport characteristics after being released from land-applied manure. Methods and Results: Turfgrass soil sod was placed into 200 cm long boxes that had the top two 25 cm sections separated to monitor the release and infiltration of bacteria, which affected bacteria transport in the rest of the box. Dairy manure with added KBr was broadcast on the top two sections. Boxes with either live or dead grass stand were placed under a rainfall simulator for 90 min. Runoff and infiltration samples were collected and analysed for Br, E. coli, enterococci and turbidity. Significant differences in release kinetics of E. coli and enterococci were found. A change from first-order release kinetics to zero-order kinetics after 1 h of rainfall simulation was observed. Conclusion: Differences in release rates but not in the subsequent transport were observed for E. coli and enterococci. Significance and Impact of the Study: Because both E. coli and enterococci are currently used as indicator organisms for manure-borne pathogens, the differences in their release rates may affect the efficiency of using these organisms as indicators. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance has become a major public health concern, and animal agriculture is often implicated as a source of resistant bacteria. The primary objective of this study was to determine prevalence of antimicrobial resistance in Salmonella and E. coli from healthy animals on dairy farms in Pennsylvania. Confidence intervals (CI) of farm prevalence were calculated for resistance, and the comparisons between different animal groups were adjusted for within-farm clustering. The secondary objective was to identify potential risk factors associated with antimicrobial resistance. In particular, we investigated the correlations between previous antimicrobial use and current resistance in E. coli using multiple logistic regression models. A total of 444 composite manure samples were collected from 80 herds in Pennsylvania. Four age and production groups were included: pre-weaned calves, post-weaned calves, dry cows, and lactating cows. E. coli (n = 2370) and Salmonella (n = 1095), when isolated from the manure composite samples (n = 444), were screened for resistance on antimicrobial supplemented agar. Isolates of interest were further assayed against 14 antimicrobials using a broth microdilution method. Salmonella was isolated from at least one composite manure sample from 51 (67%) farms, with 99% being pan-susceptible, and was detected more frequently in lactating cows and dry cows than pre- and post-weaned calves. The most prevalent Salmonella serogroups were K, C1, and C2. Among the E. coli isolates, resistance was more frequently detected in pre-weaned and post-weaned calves than in dry and lactating cows for all 14 antimicrobials tested (P < 0.05). Multi-drug resistance (resistant to ≥3 antimicrobial classes) in E. coli was detected in 66 farms (83%) and was detected more often in pre-weaned calves (P < 0.05). The blaCTX-M and blaCMY genes were found in cephalosporin-resistant E. coli from 5% and 35% of the farms surveyed, respectively. A number of risk factors, including antimicrobial use, were found to be associated with an increased likelihood of resistance in E. coli, and these associations were not limited to the same antimicrobial classes. The results of this study showed dairy farms, especially pre-weaned calves and their environment, are significant reservoirs for antimicrobial resistance, and antimicrobial use may aggravate the resistance problem. [ABSTRACT FROM AUTHOR]

The extent to which carriage of antibiotic resistant bacteria in food animals is responsible for the burden of antibiotic resistance in human infections is currently not well known. Thus, there is a need to further evaluate the genomic diversity of multidrug resistant (MDR) bacteria and the microbial communities in which they are found within these animals. To further evaluate the prevalence of antibiotic resistance in the feces of dairy animals, we sequenced the genomes of 160 antibiotic resistant Escherichia coli and 28 fecal metagenomes isolated from adult dairy cows, veal calves, and pre-weaned calves. E. coli isolates were collected from composite fecal samples and fecal grab samples taken directly from the animal. Isolates were screened for susceptibility to a panel of 14 antibiotics, and 150 showing resistance to at least one antibiotic and 10 antibiotic-susceptible isolates were selected for whole genome shotgun sequencing using a paired-end sequencing approach on an Illumina NextSeq 500. Twenty-eight fecal grab samples collected from animals shedding variable levels of antibiotic resistant E. coli were selected for shotgun metagenomics sequencing. Phylogenetic relationships among the E. coli genomes were inferred using a maximum likelihood approach in RAxML, and sequence types were determined in silico. At least four E. coli isolates from each of the major phylogroups were detected. The most frequently detected sequence types were ST88 (10% of all isolates), ST10 (9%), and ST117 (6%). Within these sequence types, isolates from different animals on the same farm and isolates from different farms were closely related, indicating that some strains of antibiotic resistant E. coli may be circulating among dairy herds within the same region. Interestingly, several MDR ST117 isolates were closely related to human ExPEC isolates and isolates recovered from chickens with colibacillosis. Metagenomic analyses indicated that for all samples tetracycline resistance genes were the most frequently identified resistance genes (61% of all resistance genes), followed by aminoglycoside (20%), macrolide (8%), beta-lactam (3%), sulfonamide (0.8%), and trimethoprim (0.6%) resistance genes. In veal calf fecal samples trimethoprim and fluoroquinolone resistance genes were more frequently detected than in pre-weaned dairy calf samples. Future work will identify genomic features that may confer persistence of high frequency antibiotic resistant E. coli strains and sequence types in the dairy cow hindgut and factors that influence the presence of antibiotic resistance in pre-weaned calves. [ABSTRACT FROM AUTHOR]

Salmonella is a prominent foodborne pathogen in the US and dairy cattle have frequently been identified as reservoirs for this organism. Here we describe a long-term outbreak of Salmonella enterica subsp. enterica Cerro that was detected in a Pennsylvania dairy herd during routine monitoring as part of a longitudinal study of several dairy herds. An initial analysis of individual fecal grab samples from the milking herd indicated a very low prevalence of Salmonella (1/102) and Salmonella was not detected in 10 environmental samples. In a subsequent sampling 6 mo later, Salmonella was isolated from 43.5% (47/108) of the cows and 40% of collected environmental samples (10/25). The Salmonella isolated in the first sampling was serovar Typhimurium var. Copenhagen, however isolates from the second herd sampling were serovars Cerro (91.5%) and Kentucky (8.5%). Sporadic environmental sampling between these initial complete milking herd samplings yielded serotypes Kentucky, Typhimurium var. Copenhagen, and Cerro and clinical salmonellosis was observed in several cows shedding Typhimurium var. Copenhagen. The herd was sampled nine additional times over the next 14 mo and fecal prevalence of Salmonella ranged from 8.4% to 89%. Prevalence remained high (58 to 69%) over the following 8 mo, showed evidence of decline over the next 3 mo, and then increased again to 89%. Cerro was the only serotype isolated during this period. Bulk milk was cultured weekly during this 22-mo period and Salmonella was isolated from 5.3% (5/94) of milk samples. For the last 14 mo of the study, milk filters were also cultured for Salmonella on a weekly basis and 65% (37/57) of the filters tested positive. There were no significant health or production concerns in the herd during this outbreak. Based on these observations we conclude that sub-clinical Salmonella enterica subsp. enterica Cerro infection can be persistent in a milking herd. [ABSTRACT FROM AUTHOR]