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Shukho Kim,1 Jung Hwa Woo,1 Nayeong Kim,1 Mi Hyun Kim,1 Se Yeon Kim,1 Joo Hee Son,1 Dong Chan Moon,2 Suk-Kyung Lim,2 Minsang Shin,1 Je Chul Lee1 1Department of Microbiology, School of Medicine, Kyungpook National University, Daegu, Republic of Korea; 2Bacterial Disease Division, Animal and Plant Quarantine Agency, Gimcheon-si, Gyeongsangbuk-do, Republic of KoreaCorrespondence: Je Chul LeeDepartment of Microbiology, School of Medicine, Kyungpook National University, 680 Gukchaebosang-ro, Jung-gu, Daegu 41944, Republic of KoreaTel +82-53-420-4844Fax +82-53-427-5664Email leejc@knu.ac.krPurpose: Colistin resistance in gram-negative bacteria from humans and livestock has been increasingly reported worldwide. The aim of this study was to investigate the underlying mechanisms of chromosome-mediated colistin resistance in Escherichia coli isolates from livestock in Korea.Materials and methods: Thirty mcr-1-negative isolates were selected from a collection of colistin-resistant E. coli isolates collected from livestock in 2005 and 2015 in Korea. Amino acid alterations in PmrAB, PhoPQ, MgrB, and PmrD were investigated. Colistin-resistant derivatives were produced by serial passage of colistin-susceptible E. coli isolates in colistin-containing media.Results: Thirty colistin-resistant mcr-negative E. coli isolates were classified into 26 sequence types. Twenty-two isolates carried diverse amino acid alterations in PmrB, PhoP, PhoQ, MgrB, and/or PmrD, whereas no mutation in any of these genes was found in the remaining eight isolates. Sixteen out of the 22 isolates shared a total of nine polymorphic positions that were found in colistin-susceptible E. coli strains. Colistin-resistant derivatives from two colistin-susceptible isolates showed the same genetic alterations that were observed in colistin-resistant clinical isolates.Conclusion: Our results suggest that the mechanism underlying chromosome-mediated colistin resistance remain to be discovered in E. coli. Selective pressure of colistin in vitro induced the same genetic mutations associated with colistin resistance in vivo. Efforts to reduce colistin consumption in livestock should be redoubled, to prevent the occurrence of colistin-resistant E. coli strains.Keywords: colistin resistance, two-component system, livestock, genetic mutation, mcr gene

Background/objectives: Bloodstream infection by carbapenem-resistant Acinetobacter baumannii (CRAB) is a serious clinical problem worldwide. To study its clonal relationship and genetic features, we report the draft genome sequence of CRAB strains isolated from human blood in South Korea., Methods: Among A. baumannii strains isolated from patients at nine general hospitals in 2020, 12 CRAB strains of different genotypes were selected. Genomic DNA was sequenced using a combination of Illumina MiSeq and Oxford Nanopore MinION platforms. Antimicrobial susceptibility testing was performed using the disk diffusion method. Antimicrobial resistance and virulence genes were investigated in silico using the Center for Genomic Epidemiology server and the Virulence Factors Database., Results: The multilocus sequence types of isolates included ST191, ST195, ST357, ST369, ST451, ST469, ST491, ST784, ST862, ST1933, ST2929, and a novel type, ST3326. The predominant sequence type, ST191, demonstrated close genetic relationships with several isolates, including ST469, ST369, ST195, ST784, ST491, and ST3326, with ST3326 classified as a subgroup of ST191. We found 18 antimicrobial resistance genes and one quaternary ammonium compound resistance gene. All examined strains harbored bla OXA-23 , which is associated with carbapenem resistance. While variations in antibiotic and disinfectant resistance genes were observed, all isolates exhibited similar virulence factors, with the exception of the biofilm and capsule production genes., Conclusions: This nationwide report of the draft genome sequence of patient-derived strains provides valuable insights into the genomic features associated with clonal relationships and antimicrobial resistance of CRAB in bloodstream infections.

Importance: Carbapenem-resistant Enterobacteriaceae are emerging as a global public health risk. Therefore, assessing the prevalence of carbapenem-resistant Escherichia coli (CRE) in both humans and animals is important., Objective: We aimed to ascertain the occurrence and characteristics of CRE isolated from companion animals, dogs and cats., Methods: E. coli strains were tested for antimicrobial susceptibility using the broth microdilution technique. Antimicrobial resistance genes were detected by polymerase chain reaction and sequencing analysis. The molecular characteristics of CRE were determined using multi-locus sequence typing, replicon typing, and pulsed-field gel electrophoresis (PFGE)., Results: In total, 13 CRE isolates (0.13%) were identified from dogs possessing bla NDM-5 along with β-lactamase genes, mostly bla CMY-2 (92.2%) and bla TEM-1 (53.8%). The commonly observed mutations were S83L and D87N in gyrA , S80I in parC , and S458A in parE . CRE carried non-beta-lactam resistance genes, with the majority being tet (B) (100%), sul (84.6%), and aac(3)-II (53.8%). Nine different PFGE patterns (P1-P9), IncX3-type plasmids (69.2%), and ST410 (84.6%) were predominantly detected., Conclusions and Relevance: This investigation provides significant insight into the prevalence and molecular characteristics of bla NDM-5 -carrying E. coli in dogs. The co-existence of bla NDM-5 and other antimicrobial resistance genes in E. coli potentially poses severe health hazards to humans., Competing Interests: The authors declare no conflicts of interest., (© 2024 The Korean Society of Veterinary Science.)

The occurrence of antimicrobial-resistant bacteria in companion animals poses public health hazards globally. This study aimed to evaluate the antimicrobial resistance profiles and patterns of commensal E. coli strains obtained from fecal samples of healthy dogs and cats in South Korea between 2020 and 2022. In total, 843 E. coli isolates (dogs, n = 637, and cats, n = 206) were assessed for susceptibility to 20 antimicrobials. The resistance rates of the most tested antimicrobials were significantly higher in dog than in cat isolates. Cefalexin (68.9%) demonstrated the highest resistance rates, followed by ampicillin (38.3%), tetracycline (23.1%), and cefazolin (18.7%). However, no or very low resistance (0-0.6%) to amikacin, imipenem, piperacillin, and colistin was found in both dog and cat isolates. Overall, 42.3% of the isolates exhibited multidrug resistance (MDR). MDR in isolates from dogs (34.9%) was significantly higher than in those from cats (20.9%). The main components of the resistance patterns were cefalexin and ampicillin in both dog and cat isolates. Additionally, MDR patterns in isolates from dogs (29.2%) and cats (16%) were shown to encompass five or more antimicrobials. Multidrug-resistant commensal E. coli could potentially be spread to humans or other animals through clonal or zoonotic transmission. Therefore, the incidence of antimicrobial resistance in companion animals highlights the urgent need to restrict antimicrobial resistance and ensure the prudent use of antimicrobials in Korea.

Enterococcus spp. are typically found in the gastrointestinal tracts of humans and animals. However, they have the potential to produce opportunistic infections that can be transmitted to humans or other animals, along with acquired antibiotic resistance. In this study, we aimed to investigate the antimicrobial resistance profiles of Enterococcus faecium and Enterococcus faecalis isolates obtained from companion animal dogs and cats in Korea during 2020-2022. The resistance rates in E. faecalis towards most of the tested antimicrobials were relatively higher than those in E. faecium isolated from dogs and cats. We found relatively higher resistance rates to tetracycline (65.2% vs. 75.2%) and erythromycin (39.5% vs. 49.6%) in E. faecalis isolated from cats compared to those from dogs. However, in E. faecium , the resistance rates towards tetracycline (35.6% vs. 31.5%) and erythromycin (40.3% vs. 35.2%) were comparatively higher for dog isolates than cats. No or very few E. faecium and E. faecalis isolates were found to be resistant to daptomycin, florfenicol, tigecycline, and quinupristin/dalfopristin. Multidrug resistance (MDR) was higher in E. faecalis recovered from cats (44%) and dogs (33.9%) than in E. faecium isolated from cats (24.1%) and dogs (20.5%). Moreover, MDR patterns in E. faecalis isolates from dogs (27.2%) and cats (35.2%) were shown to encompass five or more antimicrobials. However, E. faecium isolates from dogs (at 13.4%) and cats (at 14.8%) were resistant to five or more antimicrobials. Taken together, the prevalence of antimicrobial-resistant enterococci in companion animals presents a potential public health concern.

The production of β-lactamase by nontyphoidal Salmonella has become a public health issue throughout the world. In this study, we aimed to investigate the antimicrobial resistance profiles and molecular characteristics of β-lactamase-producing Salmonella enterica serovar Albany isolates. A total of 434 Salmonella Albany were obtained from feces and carcasses of healthy and diseased food-producing animals [cattle ( n  = 2), pigs ( n  = 3), chickens ( n  = 391), and ducks ( n  = 38)] during 2013-2020. Among the 434 Salmonella Albany isolates, 3.7% showed resistance to cefoxitin, and all the cefoxitin-resistant isolates were obtained from chickens. Moreover, Salmonella Albany isolates demonstrated high resistance to nalidixic acid (99.3%), trimethoprim/sulfamethoxazole (97.9%), ampicillin (86.6%), chloramphenicol (86.6%), and tetracycline (85.7%), as well as higher rates of multidrug resistance were detected in cefoxitin-resistant isolates compared to cefoxitin-susceptible isolates. All cefoxitin-resistant isolates harbored CMY-2-type β-lactamase and belonged to seven different pulsotypes, with type IV-b (43.75%) and IV-a (25%) making up the majority. In addition, genes encoding cefoxitin resistant of all bla CMY-2 -harboring Salmonella Albany isolates were horizontally transmitted to a recipient Escherichia coli J53 by conjugation. Furthermore, 93.75% (15/16) of conjugative plasmids harboring bla CMY-2 genes belong to ST12/CC12-IncI1. Genetic characteristics of transmitted bla CMY-2 genes were associated with IS Ecp1 , which can play an essential role in the effective mobilization and expression of these genes. Salmonella Albany containing bla CMY-2 in chickens can potentially be transferred to humans. Therefore, it is necessary to restrict antibiotic use and conduct continuous monitoring and analysis of resistant bacteria in the poultry industry.

Background and Objectives : Practitioners of martial arts such as Taekwondo are likelier to experience back pain during training or competition. As the back pain of taekwondo athletes shows various symptoms depending on the athlete's characteristics, such as technique and movement, a case study was conducted to verify the intervention effect suitable for individual traits. We examined the effects of a complex pain control program on pain, mechanosensitivity, and physical function in a Taekwondo athlete with recurrent low back pain (LBP). Materials and Methods : A Taekwondo athlete with LBP was recruited from D University, Busan. The intervention program was performed for 45 min twice a week for 3 weeks, and the patient was followed up with after 2 weeks. The numerical rating pain scale (NRPS), pain pressure threshold, mechanosensitivity, and Oswestry Disability Index (ODI) scores were measured before and after the intervention. Therapeutic massage and nerve stimulation therapy were performed. Lumbar flexion, extension, and rotation were performed in the movement control exercise group, whereas the sliding technique, a neurodynamic technique of the tibial nerve, was applied in the neurodynamic technique group. This effect was verified by comparing the average measured values before and after the intervention. Results : Pain (NRPS) and mechanosensitivity reduced, range of motion and tactile discrimination abilities improved, and physical function (ODI) improved. The effect of the improved intervention lasted 2 weeks. Conclusions: These results indicate that application of complex pain control programs considering the four aspects of pain mechanisms for 3 weeks can be an effective intervention in Taekwondo athletes with recurrent LBP.

Overall, 836 Escherichia coli isolates (695 isolates from dogs and 141 from cats) were recovered from the diarrhea, skin/ear, urine, and genitals of dogs and cats between 2018 and 2019. Cefovecin and enrofloxacin resistance were noted in 17.1% and 21.2% of E. coli isolates, respectively. The cefovecin and enrofloxacin resistance rates were higher in dog isolates (18.1% and 22.9%) compared with the rates in cat isolates (12.1%, 12.8%). Interestingly, resistance to both antimicrobials was noted in 10.8% (90/836) of the isolates, predominantly in isolates from dogs. bla CTX-M-14 , bla CTX-M-15 , and bla CMY-2 were the most frequent extended-spectrum β-lactamase/plasmid-mediated AmpC β-lactamase (ESBL/AmpC)- gene types. The co-existence of bla CTX-M and bla CMY-2 was noted in six E. coli isolates from dogs. Sequencing analysis demonstrated that S83L and D87N in gyrA and S80I in parC were the most frequent point mutations in the quinolone resistance-determining regions of the cefovecin and enrofloxacin-resistant isolates. A total of 11 isolates from dogs carried the plasmid-mediated quinolone resistance genes (six aac(6')-Ib-cr , four qnrS , and one qnrB ), while only two cat isolates carried the qnrS gene. Multilocus sequence typing of the cefovecin and enrofloxacin-resistant isolates revealed that sequence type (ST)131 E. coli carrying bla CTX-M-14 and bla CTX-M-15 genes and ST405 E. coli carrying bla CMY-2 gene were predominant among the isolated E. coli strains. The majority of the ESBL/AmpC-producing isolates displayed diverse pulsed-field gel electrophoresis profiles. This study demonstrated that third-generation cephalosporin- and fluoroquinolone-resistant E. coli were widely distributed in companion animals. The detection of the pandemic ST131 clone carrying bla CTX-M - 14/15 in companion animals presented a public health threat.

Antimicrobial-resistant bacteria isolated from food animals pose a major health threat to the public on this planet. This study aimed to determine the susceptibility profiles of Escherichia coli isolated from cattle and pig fecal samples and investigate the molecular characteristics of extended-spectrum β-lactamase (ESBL)-producing E. coli using gene identification, conjugation, and Southern blot approach. Overall 293 E. coli were recovered from cattle (120 isolates) and pigs (173 isolates) in 7 provinces of Korea during 2017-2018. Ampicillin, chloramphenicol, streptomycin, and sulfisoxazole resistance rates were the highest in pigs' isolates (>60%, p  ≤ 0.001) compared to that in cattle (3-39%). Multidrug resistance (MDR) was higher in pig isolates (73%) than in cattle (31%), and the MDR profile usually includes streptomycin, sulfisoxazole, and tetracycline. Resistance to critically important antimicrobials such as ceftiofur, colistin, and ciprofloxacin was higher in weaners than those from finishers in pigs. The qnrS gene was detected in 13% of the pig isolates. Eight isolates from pigs and one isolate from cattle were identified as ESBL-producers and ESBL genes belonged to bla CTX-M-55 ( n  = 4), bla CTX-M-14 ( n  = 3), and bla CTX-M-65 ( n  = 2). Notably, the bla CTX-M-65 and qnrS1 genes were found to be carried together in an identical plasmid (IncHI2) in two isolates from finisher pigs. The bla CTX-M -carrying isolates belonged to phylogenetic groups B1 ( n  = 4), B2 ( n  = 2), A ( n  = 2), and D ( n  = 1). The bla CTX-M genes and non-β-lactam resistance traits were transferred to the E. coli J53 recipient from seven bla CTX-M -positive strains isolated from pigs. The bla CTX-M genes belonged to the IncI1α, IncFII, and IncHI2 plasmids and are also associated with the IS Ecp1 , IS 26 , IS 903 , and orf477 elements. These findings suggested the possibility of bla CTX-M -carrying E. coli transmission to humans through direct contact with cattle and pigs or contamination of food products.

In this study, the combined use of a Bayesian mixing model (BMM), numerical model (random walk particle tracking-RWPT), and environmental tracers (δ 18 O-δD, 3 H, and CFC) was applied to elucidate the probabilistic contribution of the recharge sources, flow path, and residence time of groundwater across the mountainous area of Jeju Island, South Korea. Especially, the BMM ability to estimate the variable recharge contributions to the aquifer by different elevations and seasons was investigated. The δ 18 O-δD isotopes showed that groundwater in the study area was primarily fed by precipitation during the wet season, and the BMM estimated that wet season recharge contributed to approximately 64% of the total. The BMM-based probabilistic estimation of recharge sources revealed a mixed contribution of source waters from different elevations. A notable difference in recharge flow path was observed between highland (>450 masl) and lowland (<400 masl) wells, where the inflow of source water from the regional flow was dominant in the former and both regional and local recharges served as significant groundwater sources in the latter. Evidence from age tracers ( 3 H and CFC-12) also supported different recharge mechanisms between highland and lowland wells. A reasonable match between the BMM- and RWPT-derived recharge contributions (RMSE 0.02-0.06) was achieved within the uncertainty ranges, with RWPT being particularly useful for capturing different flow paths between highland and lowland wells. The dynamics revealed here provide important information for establishing an improved and informed groundwater management plan for the mountainous area of Jeju Island. Ultimately, this study highlights the advantageous integrated analysis of BMM, RWPT, and environmental tracer analyses to enhance the reliability of recharge area estimation and increase the collective understanding of complex hydrogeological systems in mountainous areas., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

Extended-spectrum β-lactamase (ESBL)-producing Salmonella enterica serovar Enteritidis has emerged as a public health concern. The main objectives of this study were therefore to determine the antimicrobial susceptibility profiles of Salmonella Enteritidis and to investigate the molecular characteristics of identified ESBL-producing isolates. In the study, 237 Salmonella Enteritidis isolates (232 isolates from chickens, 4 from cattle, and 1 from a pig) were recovered from carcasses and fecal samples of healthy and diseased food animals between 2010 and 2017. Ceftiofur resistance was noted only in chicken isolates (43%, 102/237), with the highest in healthy chickens and their carcasses (48.3%, 83/172) compared with that in diseased chickens (31.7%, 19/60). All of the ceftiofur-resistant isolates exhibited resistance to multiple antimicrobials. Indeed, a relatively higher percentage of ceftiofur-resistant isolates demonstrated resistance to the tested aminoglycosides and tetracycline compared with the ceftiofur-susceptible strains. In this study, bla CTX-M-15 was the only ESBL gene detected in all of the ceftiofur-resistant isolates. The bla CTX-M-15 -carrying isolates belonged to 11 different pulsotypes. The bla CTX-M-15 gene was transferred from 20.6% (21/102) of the bla CTX-M-15 -harboring isolates to a recipient Escherichia coli J53. The coexistence of IncHI2/ST2 and IncFIIs/ST1 plasmids was noted in the majority (81.8%, 18/22) of the transconjugants. E. coli J53 transconjugants carrying bla CTX-M-15 gene showed distinct genetic environments, predominantly IS Ecp1 - bla CTX-M-15 - orf477 (15/21, 71.4%). This study demonstrated that healthy chickens and their carcasses act as reservoirs of bla CTX-M-15 -carrying Salmonella Enteritidis that can potentially be transmitted to humans.

The emergence of bacterial infections in companion animals is a growing concern as humans can also be infected through the transmission of pathogenic bacteria. Because there have been few studies conducted on companion animals, the extent and significance of prevalence in veterinary practices remain unknown. This is the first nationwide surveillance report aimed at elucidating the prevalence pattern and associated infections of isolated bacteria from dogs in Korea. Bacterial isolates were collected from seven different laboratories participating in the Korean Veterinary Antimicrobial Resistance Monitoring System from 2018 to 2019. The samples were obtained from the diarrheal stool, skin/ear, urine, and respiratory samples of veterinary hospital-visited dogs. Isolation and identification of bacterial species was carried out using a bacterial culture approach and then confirmed with matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF) and polymerase chain reaction (PCR). Out of 3135 isolates in dogs, 1085, 1761, 171, and 118 were extracted from diarrheal stool, skin/ear, urine, and respiratory samples, respectively. The overall prevalence of bacteria was higher among two age groups (1-5 and 6-10 years) with a 66.5 percent prevalence. This study showed that Escherichia coli was the most prevalent species among isolated bacterial species of diarrheal and urine origin, whereas Staphylococcus pseudintermedius was the most prevalent among skin and respiratory sample isolates. The data on the prevalence of bacteria for each dog specimen could provide basic information to estimate the extent of bacterial infection and antimicrobial resistance development and to guide veterinarians in therapeutic decisions in clinical practices throughout Korea.

Bacterial infections are a significant cause of illness and death in different animals. However, these bacterial infections could be a source of human disease or illness if these pathogenic bacteria are present in companion animals. This study aimed to investigate the prevalence of pathogenic bacteria associated with different site infections in cats in the Republic of Korea. For this purpose, samples were collected from the skin/ear, urine, respiratory, and diarrheal stool origins of cats obtained between 2018 and 2019 from seven different laboratories and centers participating in the Korean Veterinary Antimicrobial Resistance Monitoring System. These samples were subjected to analysis for the identification and isolation of associated bacterial species using a bacterial culture approach. A total of 609 isolates were identified in four different cat samples. Among them, 267, 184, 57, and 101 were extracted from diarrheal stool, skin, urine, and respiratory samples, respectively. The findings of this study showed that Escherichia coli was the most prevalent species among isolated bacterial species of diarrheal stool and urine origin. Staphylococcus felis and Pasteurella multocida were most prevalent in the skin and respiratory tract, respectively. However, there was no significant difference in bacterial distribution among the different age groups in all samples. This is the first nationwide surveillance report that associates bacterial prevalence with their site of origin and helps in the prevention of bacterial infections in cats. Moreover, the pattern of bacterial prevalence could provide sufficient guidance for the selection of empirical antimicrobial therapy against infections in cats.

Antimicrobial-resistant bacteria in food animals pose a major public health threat worldwide. In this study, we aimed to assess the antimicrobial resistance profiles and resistance trends of commensal Escherichia coli isolated from the feces of healthy cattle, pigs, and chickens in South Korea during 2010 and 2020. A total of 7237 E. coli isolates (2733 cattle, 2542 pig, and 1962 chicken isolates) were tested for susceptibility towards 12 antimicrobials. About 48%, 90%, and 97% of cattle, pig, and chicken isolates, respectively, were resistant to one or more antimicrobial agents. Cattle isolates presented low resistance (<15%) to most of the tested antimicrobials. In contrast, chicken and pig isolates demonstrated a relatively high (>45%) resistance rate to ampicillin, chloramphenicol, streptomycin, and tetracycline. We observed high ciprofloxacin and nalidixic acid resistance rates in chicken (76.1% and 88.6%, respectively), isolates in pig (12.7% and 26.7%, respectively) and cattle (2.7% and 8.2%, respectively) isolates. Notably, a very small proportion of isolates (<5%) from cattle, chickens, and pigs demonstrated resistance to amoxicillin/clavulanic acid, cefoxitin, and colistin. We identified ceftiofur resistance in a small proportion of chicken (8.8%), pig (3.7%), and cattle (0.7%) isolates. We noted an increasing but fluctuating trend of ampicillin, amoxicillin/clavulanic acid, ceftiofur, cefoxitin, chloramphenicol, ciprofloxacin, and streptomycin resistance in pig isolates. Similarly, the ampicillin, ceftiofur, and chloramphenicol resistance rates were increased but fluctuated through time in chicken isolates. Overall, 56% of the isolates showed multidrug-resistant (MDR). The proportion of MDR isolates was low in cattle (17.1%); however, this proportion was high in chickens (87.1%) and pigs (73.7%). Most of the resistance patterns included streptomycin and tetracycline in pigs and cattle, and ciprofloxacin and nalidixic acid in chickens. In conclusion, this study showed high resistance of commensal E. coli isolated from major food animals in Korea to commonly used antimicrobials including critically important antimicrobials. These bacteria could not only be a resistance reservoir but also could have potential to spread this resistance through gene transfer to pathogenic bacteria. Thus, the high prevalence of antimicrobial resistance in food animals highlights the urgent need for measures to restrict and ensure the prudent use of antimicrobials in Korea.

Treatment of infectious diseases caused by carbapenem-resistant Pseudomonas aeruginosa is becoming a greater challenge. This study aimed to identify the imipenem resistance mechanism in P. aeruginosa isolated from a dog. Minimum Inhibitory Concentration (MIC) was determined by the broth microdilution method according to the Clinical and Laboratory Standards Institute recommendations. We performed polymerase chain reaction and whole-genome sequencing to detect carbapenem resistance genes. Genomic DNA of P. aeruginosa K19PSE24 was sequenced via the combined analysis of 20-kb PacBio SMRTbell and PacBio RS II. Peptide-Peptide Nucleic Acid conjugates (P-PNAs) targeting the translation initiation region of bla OXA-913 were synthesized. The isolate (K19PSE24) was resistant to imipenem and piperacillin/tazobactam yet was susceptible to most of the tested antimicrobials. Whole-genome sequencing revealed that the K19PSE24 genome comprised a single contig amounting to 6,815,777 base pairs, with 65 tRNA and 12 rRNA genes. K19PSE24 belonged to sequence type 313 and carried the genes aph(3)-IIb , fosA , catB7 , crpP , and bla OXA-913 (an allele deposited in GenBank but not described in the literature). K19PSE24 also carried genes encoding for virulence factors (exoenzyme T, exotoxin A, and elastase B) that are associated with adhesion, invasion, and tissue lysis. Nevertheless, we did not detect any of the previously reported carbapenem resistance genes. This is the first report of the bla OXA-913 gene in imipenem-resistant P. aeruginosa in the literature. Notably, no viable colonies were found after co-treatment with imipenem (2 µg/mL) and either of the P-PNAs (12.5 µM or 25 µM). The imipenem resistance in K19PSE24 was primarily due to bla OXA-913 gene carriage.

Contamination of meat with antimicrobial-resistant bacteria represents a major public health threat worldwide. In this study, we determined the antimicrobial resistance profiles and resistance trends of Staphylococcus aureus isolated from major food animal carcasses (408 cattle, 1196 pig, and 1312 chicken carcass isolates) in Korea from 2010 to 2018. Approximately 75%, 92%, and 77% of cattle, pig, and chicken carcass isolates, respectively, were resistant to at least one antimicrobial agent. Resistance to penicillin (62.1%) was the highest, followed by resistance to tetracycline (42.1%) and erythromycin (28.2%). About 30% of pig and chicken isolates were resistant to ciprofloxacin. We observed linezolid resistance only in pig isolates (2.3%). However, all S. aureus isolates were sensitive to rifampin and vancomycin. We noted an increasing but fluctuating trend of kanamycin and penicillin resistance in cattle isolates. Similarly, the chloramphenicol, ciprofloxacin, tetracycline, and trimethoprim resistance rates were increased but fluctuated through time in pig isolates. Methicillin-resistant S. aureus (MRSA) accounted for 5%, 8%, and 9% of the cattle, pig, and chicken isolates, respectively. The MRSA strains exhibited significantly high resistance rates to most of the tested antimicrobials, including ciprofloxacin, erythromycin, and tetracycline compared with methicillin-susceptible S. aureus (MSSA) strains. Notably, a relatively high percentage of MRSA strains (5.2%) recovered from pig carcasses were resistant to linezolid compared with MSSA strains (2.1%). In addition, almost 37% of the isolates were multi-drug resistant. S. aureus isolates recovered from major food animal carcasses in Korea exhibited resistance to clinically important antimicrobials, posing a public health risk.

We identified 1218 Campylobacter &nbsp; coli isolates from fecal and carcass samples of pigs ( n = 643) and chickens ( n = 575) between 2010 and 2018. About 99% of the isolates were resistant to at least one antimicrobial agent. The isolates exhibited high resistance rates (>75%) to ciprofloxacin, nalidixic acid, and tetracycline. Azithromycin and erythromycin resistance rates were the highest in isolates from pigs (39.7% and 39.2%, respectively) compared to those of chickens (15.8% and 16.3%, respectively). Additionally, a low-to-moderate proportion of the isolates were resistant to florfenicol, gentamicin, clindamycin, and telithromycin. Multidrug resistance (MDR) was found in 83.1% of the isolates, and profiles of MDR usually included ciprofloxacin, nalidixic acid, and tetracycline. We found point mutation (A2075G) in domain V of the 23S rRNA gene in the majority of erythromycin-resistant isolates. Multilocus sequence typing of 137 erythromycin-resistant C . coli isolates revealed 37 previously reported sequence types (STs) and 8 novel STs. M192I, A103VI, and G74A substitutions were frequently noted in the ribosomal proteins L4 or L22. Further, we identified a considerable proportion (>90%) of erythromycin-resistant isolates carrying virulence factor genes: flaA , cadF , ceuE , and VirB . The prudent use of antimicrobials and regular microbiological investigation in food animals will be vital in limiting the public health hazards of C . coli in Korea.

Intestinal commensal bacteria are considered good indicators for monitoring antimicrobial resistance. We investigated the antimicrobial resistance profiles and resistance trends of Enterococcus faecium and Enterococcus faecalis isolated from food animals in Korea between 2010 and 2019. E. faecium and E. faecalis, isolated from chickens and pigs, respectively, presented a relatively high resistance rate to most of the tested antimicrobials. We observed high ciprofloxacin (67.9%), tetracycline (61.7%), erythromycin (59.5%), and tylosin (53.0%) resistance in E. faecium isolated from chickens. Similarly, more than half of the E. faecalis isolates from pigs and chickens were resistant to erythromycin, tetracycline and tylosin. Notably, we observed ampicillin, daptomycin, tigecycline and linezolid resistance in a relatively small proportion of enterococcal isolates. Additionally, the enterococcal strains exhibited an increasing but fluctuating resistance trend ( p < 0.05) to some of the tested antimicrobials including daptomycin and/or linezolid. E. faecalis showed higher Multidrug resistance (MDR) rates than E. faecium in cattle (19.7% vs. 8.6%, respectively) and pigs (63.6% vs. 15.6%, respectively), whereas a comparable MDR rate (≈60.0%) was noted in E. faecium and E. faecalis isolated from chickens. Collectively, the presence of antimicrobial-resistant Enterococcus in food animals poses a potential risk to public health.

The emergence of extended-spectrum cephalosporin (ESC)-resistant Gram-negative bacteria is of great concern in both human and veterinary medicine. The aim of this study was to investigate ESC-resistant bacterial isolates from companion animals in South Korea between 2017 and 2019. Isolates with ESC resistance genes, which were identified by PCR, were assessed for genetic relatedness by multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). In total, 91 ESC-resistant Escherichia coli, Klebsiella spp., Serratia spp., and Enterobacter cloacae isolates harbored the bla TEM gene. Among other ESC resistance genes, bla CTX-M-15 , bla CIT , and bla CTX-M-55 were predominantly detected in E. coli isolates, whereas bla SHV and bla DHA were more frequently detected in Klebsiella pneumoniae isolates. In addition, all bla EBC -positive isolates were classified as E. cloacae . From the MLST results, bla CTX-M-9 -carrying ST131, bla CIT -carrying ST405, and bla CTX-M-1 -carrying ST3285 strains were dominant among E. coli isolates. ST273 and ST275 strains harboring bla SHV were frequently detected in K. pneumoniae isolates. Various sequence types were obtained in E. cloacae and Klebsiella oxytoca isolates. All isolates demonstrated unique PFGE profiles (<57-98% similarity) and were unlikely to be derived from a single clone. The present study reveals the presence and wide genetic distribution of ESC-resistant bacterial species in South Korean companion animals.

Objectives: Human infection by ciprofloxacin-resistant Salmonella enterica serovar Kentucky sequence type 198 (ST198) has been reported in the USA, Europe and Korea. In this study, we report the complete genome sequence of the first Salmonella Kentucky ST198 strain isolated from a chicken carcass in South Korea., Methods: The recovered Salmonella Kentucky, designated as K13SK002, was isolated from a chicken carcass in 2013. Genomic DNA was sequenced using a combination of 20-kb PacBio SMRTbell library and PacBio RS II. Antimicrobial susceptibility testing was performed and minimum inhibitory concentration (MIC) values were determined. Antimicrobial resistance and virulence genes were investigated in silico using ResFinder and VirulenceFinder tools, respectively, available at the Center for Genomic Epidemiology server., Results: The genome of K13SK002 consists of contiguous sequences (contigs) with a total length of 4 847 849 bp and a GC content of 52.20%. We detected a total of 4352 protein-coding sequences, 85 tRNA genes and 22 rRNA genes. MICs for ampicillin, ciprofloxacin, gentamicin, streptomycin, sulfisoxazole and tetracycline were 64, 16, 16, 64, >256 and 128 μg/mL, respectively. We found six antimicrobial resistance genes, however no plasmids and genes associated with adherence, toxins and exoenzyme were found. Ciprofloxacin-resistant Salmonella Kentucky K13SK002 was found to have mutations in DNA gyrase A (S83F and D87Y)., Conclusion: This is the first report of the complete genome sequence of a Salmonella Kentucky ST198 strain isolated from a chicken carcass in South Korea. This genome sequence provides useful information on the genomic features associated with virulence and antimicrobial resistance in Salmonella Kentucky ST198., (Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Objectives: Salmonella enterica Indiana ST17 strain (K16SI097), exclusively found in China, was first isolated in 2016 in Korea from a chicken carcass. This strain contains multidrug-resistant genes, and is particularly resistant to ciprofloxacin (64 μg/mL). In this study, we aimed to elucidate the genomic relationship and compare antimicrobial resistance factors between Korean chicken-derived and Chinese clones of S. Indiana ST17., Methods: The genomic DNA of S. enterica Indiana K16SI097 was sequenced via the combined analysis of 20-kb PacBio SMRTbell library and PacBio RS II. Antimicrobial resistance genes were analysed by the Center for Genomic Epidemiology (http://www.genomicepidemiology.org/). Chromosomal and plasmid DNA of the Korean and Chinese strains were compared., Results: The K16SI097 genome comprises two contiguous sequences (contigs) amounting to 4 731 335 base pairs with a 51.85% GC content. In total, 4574 protein-coding regions, 84 tRNA genes, and 22 rRNA genes were detected. Among the annotated contigs, 14 antimicrobial resistance genes were detected; DNA gyrase and topoisomerase IV contained mutations. Moreover, chromosomal DNA of K16SI097 and of the published Chinese strain displayed 99.9% similarity. Furthermore, plasmids displayed similar sizes, sequences, and structures., Conclusions: This is the first report on the complete genome sequence of the high-level ciprofloxacin-resistant S. enterica Indiana ST17 strain isolated in Korea. This genome sequence will help us understand the ST17 strain lineage and its features such as antimicrobial resistance., (Copyright © 2021. Published by Elsevier Ltd.)

Colistin is considered the last resort for the treatment of multi-drug resistant Gram-negative bacterial infections. We studied colistin resistance and the mcr-1 gene carriage in Salmonella isolates recovered from food animals in South Korea between 2010 and 2018. Colistin resistance was found in 277 isolates, predominantly in Salmonella Enteritidis (57.1%) and Salmonella Gallinarum (41.9%). However, the mcr-1 gene was identified in only one colistin-resistant Salmonella Typhimurium (MIC = 16 µg/mL) isolated from a healthy pig. The mcr-1 carrying isolate presented additional resistance to multiple antimicrobials. The strain belonged to sequence type (ST)19 and carried various virulence factor genes that are associated with adhesion and invasion of Salmonella into intestinal epithelial cells, as well as its survival in macrophages. The mcr-1 gene was identified on an IncI2 plasmid and it was also transferred to the E . coli J53 recipient strain. The mcr - 1 -carrying plasmid (pK18JST013) in this study was closely related to that previously reported in S . Indiana (pCFSA664-3) from chicken in China. This is the first report of mcr-1 carrying S . Typhimurium in South Korea. The finding indicates the importance of regular screening for the presence of the mcr - 1 gene in S . Typhimurium in food animals to prevent the spread to humans.

Staphylococcus aureus is among the most common zoonotic pathogens that cause foodborne illnesses worldwide. The main objectives of the current study were therefore to determine the antimicrobial susceptibility profiles of S. aureus isolated from goats in Korea and to investigate the molecular characteristics of identified methicillin-resistant S. aureus (MRSA). In the study, 481 S. aureus isolates (431 from the nasal cavity and 50 from carcass) were recovered from 1146 carcasses and nasal swabs between July 2018 and January 2019. Approximately 82% and 72.6% of nasal and carcass isolates, respectively, were resistant to at least one antimicrobial agent, with the highest rate of resistance to penicillin, followed by resistance to chloramphenicol and tetracycline. Relatively small proportions of the isolates were resistant to cefoxitin, clindamycin, and erythromycin. However, all S. aureus isolates were sensitive to linezolid, rifampin, and vancomycin. Six MRSA isolates were obtained, three each from the nasal cavity and carcass. MRSA isolates were of two sequence types (ST) (ST72 and ST398), three spa types (t664, t324, and t571), and two SCCmec types (IV and V). The ST72 MRSA isolates had identical PFGE profiles. In addition, ST72 MRSA-SCCmec IV isolates carried at least six staphylococcal leukotoxin- and enterotoxin-encoding genes (lukED, seg, sei, sem, sen, seo, and seq). The remaining ST398 isolate carried only the lukED gene and was additionally resistant to eight non-β-lactam antibiotics. To the best of our knowledge, this is the first report of MRSA from goats in Korea. There is a possibility of transmission of MRSA from goat to human or contamination of food products. Therefore, regular microbiological investigation in goats, farms, and slaughterhouses is critical to determine the existence of virulent and multi-drug resistant (MDR) S. aureus and to implement preventive strategies., (Copyright © 2020 Elsevier B.V. All rights reserved.)

We identified 199 Staphylococcus aureus isolates from quarter milk samples of 1,289 dairy cattle between 2014 and 2018. About 66% of the isolates were resistant to at least 1 antimicrobial agent; the highest rate of resistance was to penicillin, followed by resistance to ampicillin, erythromycin, and sulfadimethoxine. We obtained 30 methicillin-resistant S. aureus (MRSA) strains from 6 farms in 3 provinces. The MRSA strains exhibited a significantly higher resistance rate to most of the tested antimicrobials than the oxacillin-susceptible strains. The MRSA strains represented 5 genotypes: ST72-t324-SCCmec IV (n = 14), ST30-t1752-SCCmec IV (n = 8), ST188-t189-SCCmec NT (n = 6), ST188-t2284-SCCmec NT (n = 1), and NT-NT-SCCmec IV (n = 1). One of the ST188 MRSA strains represented a novel staphylococcal protein A (spa) type (t2284). In addition, 7 of the 8 ST30 MRSA strains were Panton-Valentine leukocidin (PVL)-positive and carried various staphylococcal enterotoxin encoding genes. This is the first report of PVL-positive ST30 MRSA-t1752-SCCmec IV from bovine mastitis in Korea. All of ST72-t324-SCCmec IV MRSA strains carried staphylococcal enterotoxin and leukotoxin encoding genes. They were also sensitive to most of the tested non-β-lactam antimicrobials. In contrast, ST188-t189 MRSA strains were resistant to multiple antimicrobials and predominantly carried the leukotoxin encoding gene. Taken together, these findings may indicate that dairy cows could be a major source for spreading MRSA strains, and contaminated milk could be a vehicle for transmission. Suitable hygienic measures should be established in dairy farms and processing plants to limit the likelihood of introducing MRSA into the food chain., (Copyright © 2021 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Food-producing animals are considered a leading source of human Salmonella infections in Korea. However, there is a lack of comprehensive and up-to-date data regarding the diversity and resistance profiles of Salmonella serotypes in these animals. Therefore, this study aimed to determine the distribution and antimicrobial resistance profiles of Salmonella serotypes isolated from cattle, pigs, and chickens in Korea between 2010 and 2018. A total of 3018 Salmonella isolates were obtained from 16 laboratories/centers participating in the Korean Veterinary Antimicrobial Resistance Monitoring System. Salmonella serotypes were identified from the following isolates: 179 cattle (17 serotypes), 959 pig (45 serotypes), and 1880 chicken (64 serotypes). The most frequent serotypes in cattle (Typhimurium, Salmonella 4,[5],12:i:-, and Schwarzengrund), pigs (Typhimurium, Rissen, and S. 4,[5],12:i:-), and chickens (Enteritidis, Albany, Virchow, and Montevideo) accounted for more than 50% of the total serotypes in the respective animal species. To the best of our knowledge, Salmonella 4,[5],12:i:- has not been identified in cattle in Korea to date. More than 80% of the isolates demonstrated resistance to at least one antimicrobial agent. Multidrug-resistance was found in almost half of the serotypes; the highest proportion in cattle (59.2%), followed by pigs (53.4%), and chickens (45.7%). Significant proportions of the serotypes were resistant to ampicillin, streptomycin, and tetracycline. Ceftiofur and ciprofloxacin resistance rates were the highest in Salmonella isolated from chickens (17.1% and 4.1%, respectively) and cattle (10.1% and 3.9%, respectively) compared to that in pigs. Among the frequent serotypes, Albany demonstrated the highest resistance rate (>90%) to five different antimicrobials. Alarmingly, some Salmonella serotypes that are frequently associated with human infections demonstrated a trend of increasing resistance to critically important antibiotics, including 3rd generation cephalosporins and quinolones. Collectively, the presence of antibiotic-resistant Salmonella in food-producing animals poses a potential risk to public health., (Copyright © 2020. Published by Elsevier B.V.)

We aimed to investigate the presence of the phenicol-oxazolidinone resistance gene poxtA in linezolid-resistant enterococci from food-producing animals and analyze its molecular characteristics. We collected 3941 Enterococcus faecium and 5088 E. faecalis isolates from all provinces of South Korea from 2008 to 2018. We found linezolid resistance in 0.79% (94/3941) of E. faecium and 1.22% (62/5088) of E. faecalis isolates. Overall, 23.1% (36/156) of the linezolid-resistant isolates had the poxtA gene, including 31 E. faecium and five E. faecalis isolates. The poxtA -positive enterococci were mainly isolated from chicken (86.1%; 26/36). Fifteen poxtA -harboring isolates co-carried another linezolid-resistance gene, optrA . Eight E. faecium isolates had an N130K mutation in the ribosomal protein L4, while no mutations were observed in E. faecalis isolates. The poxtA gene was transferred into 10 enterococci by conjugation. Multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) analysis indicated that poxtA -carrying isolates were heterogeneous. Three E. faecium isolates belonged to CC17 (ST32, ST121, and ST491). To our knowledge, this is the first report on the poxtA gene in Korea. Prudent use of antimicrobials and active surveillance on antimicrobial resistance are urgently needed to reduce the risk of dissemination of the linezolid-resistant isolates in humans and animals.

We studied the presence of the mobile colistin resistance gene mcr - 1 in Escherichia coli isolates recovered from fecal and urine samples of companion animals, that were collected from South Korea in 2018 and 2019. The mcr - 1 gene was detected in one colistin-resistant E . coli isolated from a diarrheic dog. The isolate exhibited additional resistance to multiple antimicrobials, including fluoroquinolones and third-generation cephalosporins. The mcr - 1 carrying isolate belonged to ST160. The pulsed-field gel electrophoresis pattern of our strain differed from those ST160 E . coli strains previously identified from chickens in Korea. The mcr-1 gene was identified in the IncI2 plasmid. It was also transferred to E. coli J53 recipient strain, with a conjugation efficiency of 2.8 × 10 -4 . Average nucleotide identity analysis demonstrated that the mcr - 1 -carrying plasmid in this study was closely related to those from patients in Korea. To the best of our knowledge, this is the first report of mcr -1 carrying E. coli from a companion animal in South Korea. Our findings support One Health approach is necessary to prevent the dissemination of this high-risk gene.

Altogether, 2547 Staphylococcus aureus isolated from cattle ( n = 382), pig ( n = 1077), and chicken carcasses ( n = 1088) during 2010-2017 were investigated for linezolid resistance and were further characterized using molecular methods. We identified linezolid resistance in only 2.3% of pig carcass isolates. The linezolid-resistant (LR) isolates presented resistance to multiple antimicrobials, including chloramphenicol, clindamycin, and tiamulin. Molecular investigation exhibited no mutations in the 23S ribosomal RNA. Nevertheless, we found mutations in ribosomal proteins rplC (G121A) and rplD (C353T) in one and seven LR strains, respectively. All the LR isolates carried the multi-resistance gene cfr , and six of them co-carried the mecA gene. Additionally, all the LR isolates co-carried the phenicol exporter gene, fexA , and presented a high level of chloramphenicol resistance. LR S. aureus isolates represented 10 genotypes, including major genotypes ST433-t318, ST541-t034, ST5-t002, and ST9-t337. Staphylococcal enterotoxin and leukotoxin-encoding genes, alone or in combination, were detected in 68% of LR isolates. Isolates from different farms presented identical or different pulsed-field gel electrophoresis patterns. Collectively, toxigenic and LR S. aureus strains pose a crisis for public health. This study is the first to describe the mechanism of linezolid resistance in S. aureus isolated from food animal products in Korea.

We examined the prevalence and molecular characteristics of mcr-3 carrying colistin-resistant Escherichia coli among cattle, pig, and chicken isolates in South Korea. Among a total of 185 colistin-resistant E. coli isolates determined in this study (47 from cattle, 90 from pigs, and 48 from chicken), PCR amplification detected mcr - 3 genes in 17 isolates predominantly from diseased pigs. The mcr - 3 genes were characterized as mcr-3.1 in 15 isolates and mcr - 3.5 in 2 isolates. The mcr-3 gene was transferred to the E. coli J53 recipient strain from more than 50% of the mcr - 3 -carrying isolates. The mcr - 3. 1 and mcr - 3.5 genes were identified predominantly in IncHI2 and IncP plasmids, respectively. Multi-locus sequence typing analysis revealed eight previously reported sequence types (ST), including ST1, ST10, and ST42. We identified isolates with similar pulsed-field gel electrophoresis patterns from diseased pigs in three farms. Besides, the isolates carried various virulence factors and demonstrated resistance to multiple antimicrobials, including β-lactams and quinolones. Further, the mcr - 3.5 encodes three amino acid substitutions compared with mcr - 3. 1. To the best of our knowledge, this is the first report of pathogenic E. coli carrying mcr - 3.5 in South Korea, which implies that mcr - 3 variants may have already been widely spread in the pig industry.

We aimed to identify and characterize extended-spectrum β-lactamase (ESBL)-and/or plasmid-mediated AmpC β-lactamase (pAmpC)-producing Escherichia coli isolated from healthy broiler chickens slaughtered for human consumption in Korea. A total of 332 E. coli isolates were identified from 339 cloacal swabs in 2019. More than 90% of the isolates were resistant to multiple antimicrobials. ESBL/pAmpC-production was noted in 14% (46/332) of the isolates. Six of the CTX-M-β-lactamase-producing isolates were found to co-harbor at least one plasmid-mediated quinolone resistance gene. We observed the co-existence of bla CMY-2 and mcr-1 genes in the same isolate for the first time in Korea. Phylogenetic analysis demonstrated that the majority of bla CMY-2 -carrying isolates belonged to subgroup D. Conjugation confirmed the transferability of bla CTX-M and bla CMY-2 genes, as well as non-β-lactam resistance traits from 60.9% (28/46) of the ESBL/pAmpC-producing isolates to a recipient E. coli J53. The ISECP , IS903 , and orf477 elements were detected in the upstream or downstream regions. The bla CTX-M and bla CMY-2 genes mainly belonged to the IncI1, IncHI2, and/or IncFII plasmids. Additionally, the majority of ESBL/pAmpC-producing isolates exhibited heterogeneous PFGE profiles. This study showed that healthy chickens act as reservoirs of ESBL/pAmpC-producing E. coli that can potentially be transmitted to humans.

Global dissemination of non-typhoidal Salmonella producing extended-spectrum β-lactamase (ESBL) is a public-health concern. Recently, the prevalence of Salmonella spp. resistant to third-generation cephalosporins has been increasing in food-producing animals in Korea. In this study, we investigated resistance mechanisms and molecular characteristics of S. Virchow isolates resistant to extended-spectrum cephalosporins (ESCs). We obtained 265 S. Virchow isolates from fecal and carcasses samples of cattle (n = 2), pigs (n = 7), and chickens (n = 256) during 2010-2017, and observed high ESC-resistance (63.8%, 169/265); most of the resistant isolates (96.4%) were obtained from chickens. ESC-resistant S. Virchow isolates (n = 169) showed significantly higher resistance rates to other antimicrobials (especially aminoglycosides and tetracycline, p-value <0.0001), as well as prevalence of multidrug resistance, than did ESC-susceptible S. Virchow isolates (n = 96). All ESC-resistant S. Virchow produced CTX-M-15-type ESBL (n = 147) and/or CMY-2-type AmpC β-lactamase (n = 23). ESC-resistant S. Virchow represented seven pulsotypes, predominantly composed of type II (58.6%) and III (26.0%), detected in 69 farms in 10 provinces, and 33 farms in 7 provinces, respectively. Genes encoding ESC-resistance were horizontally transferred by conjugation to recipient E. coli J53; this was demonstrated in 28.8% (42/146) of bla CTX-M-15 -positive isolates and in 50.0% (11/22) of bla CMY-2 -positive isolates. All conjugative plasmids carrying bla CTX-M-15 and bla CMY-2 genes belonged to ST2-IncHI2 and ST12/CC12-IncI1, respectively. Genetic features of transferred bla genes were involved with ISEcp1 in both bla CTX-M-15 and bla CMY-2 ; ISEcp1 plays a critical role in the efficient capture, expression, and mobilization of bla genes. In addition to bla CTX-M-15 genes, resistance markers to aminoglycosides and/or tetracycline were co-transferred to recipient E. coli J53. Our results show a high prevalence of ESBL-producing S. Virchow in chickens and chicken carcasses. Specific bla CTX-M-15 and bla CMY-2 -carrying S. Virchow clones and plasmids were predominant in food-producing animals nationwide. Restriction of antimicrobial use and proper biosecurity practices at the farm level should be urgently implemented in the poultry industry., Competing Interests: Declaration of competing interest Not applicable., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Antibiotics administered to farm animals have led to increasing prevalence of resistance genes in different microbiomes and environments. While antibiotic treatments help cure infectious diseases in farm animals, the possibility of spreading antibiotic resistance genes into the environment and human microbiomes raises significant concerns. Through long-term evolution, antibiotic resistance genes have mutated, thereby complicating the resistance problems., Results: In this study, we performed deep sequencing of the gut microbiomes of 36 swine and 41 cattle in Korean farms, and metagenomic analysis to understand the diversity and prevalence of antibiotic resistance genes. We found that aminoglycoside, β-lactam, lincosamide, streptogramin, and tetracycline were the prevalent resistance determinants in both swine and cattle. Tetracycline resistance was abundant and prevalent in cattle and swine. Specifically, tetQ, tetW, tetO, tet32, and tet44 were the 5 most abundant and prevalent tetracycline resistance genes. Their prevalence was almost 100% in swine and cattle. While tetQ was similarly abundant in both swine and cattle, tetW was more abundant in swine than in cattle. Aminoglycoside was the second highest abundant resistance determinant in swine, but not in cattle. In particular, ANT(6) and APH(3'') were the dominant resistance gene families in swine. β-lactam was also an abundant resistance determinant in both swine and cattle. Cfx was the major contributing gene family conferring resistance against β-lactams., Conclusions: Antibiotic resistome was more pervasive in swine than in cattle. Specifically, prevalent antibiotic resistance genes (prevalence >50%) were found more in swine than in cattle. Genomic investigation of specific resistance genes from the gut microbiomes of swine and cattle in this study should provide opportunities to better understand the exchange of antibiotic resistance genes in farm animals., (© The Author(s) 2020. Published by Oxford University Press.)

The increasing prevalence of antimicrobial resistance and the laborious development of novel antimicrobial agents have limited the options for effective antimicrobial therapy. The combination of previously used antimicrobial agents represents an alternative therapy for multidrug-resistant (MDR) pathogens. The objective of this study was to investigate the synergistic effect of a florfenicol (FFL)-based combination with other antimicrobial agents against MDR Escherichia coli isolates from livestock using checkerboard assays and murine infection models. The FFL/amikacin (AMK) and FFL/gentamicin (GEN) combinations showed synergy against 10/11 and 6/11 MDR E. coli isolates in vitro, respectively. The combination of FFL with aminoglycosides (AMK or GEN) exhibited a better synergistic effect against MDR E. coli isolates than the cephalothin (CEF)/GEN or FFL/CEF combinations. The combination of FFL with AMK or GEN could reduce the emergence of resistant mutants in vitro. The FFL/AMK combination showed a higher survival rate of mice infected with MDR E. coli isolates than FFL or AMK alone. In summary, the combination of FFL with aminoglycosides (AMK or GEN) is highly effective against MDR E. coli isolates both in vitro and in vivo. Our findings may contribute to the discovery of an effective combination regimen against MDR E. coli infections in veterinary medicine.

Background: Antimicrobial resistance is becoming increasingly important in both human and veterinary medicine. According to the One Health concept, an important step is to monitor the resistance patterns of pathogenic bacteria. In this study, the antimicrobial susceptibility patterns and trends of bacteria isolated from stray cats, hospital-admitted cats, and veterinary staff in South Korea between 2017 and 2018 were investigated., Results: The minimum inhibitory concentrations of different antibiotics for Staphylococcus spp., Enterobacteriaceae, and Enterococcus spp. were determined to establish representatives of different antibiotic classes relevant for treatment or surveillance. For Coagulase-positive and Coagulase-negative Staphylococci, resistance to fluoroquinolones was below 13%, but resistance to ampicillin and penicillin was high (20-88%). A total of 9.5, 12.1, and 40.3% of staphylococcal isolates from stray cats, hospital-admitted cats, and veterinary staff, respectively, were confirmed to be mecA positive. For Enterobacteriaceae, resistance to carbapenems, fluoroquinolones, and 3rd generation cephalosporins was low (0-11.1%). The Enterococcus spp. isolates showed no resistance to vancomycin. The antimicrobial resistance rates of the Staphylococcus spp. and Enterobacteriaceae isolates from stray cats were usually lower than those of isolates from hospital-admitted cats and veterinary staff, but the Enterococcus spp. isolates revealed the opposite. Thus, the antimicrobial resistance varied across bacterial species according to the source from which they were isolated., Conclusions: Resistance to critically important compounds were low. However, the presence of antimicrobial resistance in cat isolates is of both public health and animal health concern.

Ducks are potential carriers of pathogenic bacteria, which are capable of transmitting zoonotic diseases to humans. The global spread of Enterobacteriaceae carrying extended-spectrum β-lactamase (ESBL) genes is a public health concern. This study investigated the prevalence of antimicrobial resistance in Escherichia coli isolated from ducks in Korea and described the molecular characteristics of the ESBLs they produced. A total of 146 E. coli isolates from 404 duck fecal and carcass samples in 85 duck farms were tested for antimicrobial resistance using the broth dilution method and were further characterized using molecular methods. We observed high resistance rates to tetracycline, trimethoprim/sulfamethoxazole, nalidixic acid, ampicillin, and ciprofloxacin. In total, six ceftiofur-resistant isolates (4.1%) were observed, which produced CTX-M-55 ( n  = 3) or CTX-M-65 β-lactamase ( n  = 3). All CTX-M-producing E. coli isolates were also resistant to ciprofloxacin, with mutations in the quinolone resistance determining region of GyrA (S83L with or without D87N) and ParC (S80I), and three CTX-M-producing E. coli isolates carried plasmid-mediated quinolone resistance (PMQR) genes, qepA ( n  = 1), qnrS , and acc ( 6' ) -Ib-cr ( n  = 2). The transfer of bla CTX-M genes was observed in one isolate mediated by IncF-family plasmids but not in the co-resistant isolates carrying both bla CTX-M and PMQR genes. Pulsed-field gel electrophoresis and multilocus sequence typing demonstrated that CTX-M-producing isolates were heterogeneous; however, identical isolates were found in different farms and slaughterhouses. This study presents baseline data on antimicrobial resistance of E. coli derived from duck samples and is the first report of CTX-M-55 and CTX-M-65 β-lactamase-producing E. coli isolated from ducks in Korea. The dissemination of ESBL-producing E. coli poses a potential risk to public health and therefore should be monitored.

Coagulase-negative staphylococci (CNS) are one of the most common bovine mastitis pathogens found worldwide. In this study, we investigated the prevalence and distribution of CNS species in mastitis milk samples and further characterized the methicillin-resistant (MR) CNS. A total of 311 CNS were isolated from 3,692 quarter milk samples from 1,373 dairy cattle at 81 farms between 2013 and 2017. Further evaluation of the CNS isolates revealed 14 CNS species among the samples and 3 predominant species-namely, Staphylococcus chromogenes, Staphylococcus simulans, and Staphylococcus epidermidis. Resistance was higher in S. epidermidis than in other CNS species except for resistance against oxacillin in Staphylococcus sciuri. Resistance to β-lactams was the most common in all CNS species (8.4% in ampicillin, 21.2% in oxacillin, and 13.5% in penicillin). Conversely, only minimal resistance to cephalothin, ceftiofur, and pirlimycin/novobiocin was found. Twenty-one isolates from 4 species were mecA-carrying MRCNS strains, including 18 S. epidermidis and 1 each of S. sciuri, Staphylococcus equorum, and Staphylococcus hominis. The majority of the mecA-carrying MRCNS isolates were produced in the biofilm. Furthermore, multidrug-resistant sequence type 179 isolate produced the strongest biofilm. Seven genotypes were detected in the 18 MR S. epidermidis strains, the most predominant of which persisted on a farm for 2 yr. Our findings for the antimicrobial susceptibility profiles and genotypic characterization of the MRCNS isolates could provide valuable information for controlling the spread of resistance and the selection of appropriate antimicrobial therapies for mastitis in the future. Further, strategic antibiotic use for mastitis treatment and hygienic management practices aimed at the prevention of the growth of resistant bacteria are urgently needed on dairy farms., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Pasteurella multocida causes single or complex respiratory disease in pigs. Although antimicrobial therapy is the most effective treatment for porcine respiratory disease, P. multocida shows increased antimicrobial resistance in Korea. Therefore, we aimed to investigate the phenotypic and genotypic characterization of tetracycline-resistant P. multocida. Thirty-seven of 454 P. multocida isolates from South Korea between 2010 and 2016 were selected. Four tet genes [tet(B) (78.4%), tet(H) (16.2%), tet(C) (5.4%), and tet(O) (2.7%)] were observed. This is the first report of tet(C) in P. multocida. Various virulence factors were observed in both tetracycline-resistant and -susceptible P. multocida isolates. Genes encoding pmHAS and pfhA were more prevalent in tetracycline-resistant than in tetracycline-susceptible isolates. Some virulence factors exhibited association with serogroups. tadD and sodA were common in serogroup A, while hsf-l was significantly associated with serogroup D (p < 0.01). Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) results showed the genetic diversity of tetracycline-resistant P. multocida. MLST showed six different sequence types (ST), with clonal complex 13 encompassing 56.8% of the strains. PFGE was more efficient in differentiating the isolates, and 29 PFGE patterns of the strains were observed. By combining these methods, identical STs and PFGE patterns were observed in isolates from different farms, suggesting that transmission of antimicrobial-resistant P. multocida strains between farms might occur in a geographically discrete population. In future, epidemiological approaches and development of effective vaccines should focus on the major clonal lineages carrying the important virulence factors and frequently observed resistance genes to prevent the transmission and control the disease., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In this study, we investigated the prevalence and characteristics of methicillin-resistant Staphylococcus aureus (MRSA) isolates from pigs and pig farmers in Korea. A total of 1245 nasal swabs were collected from pigs and farmers at 53 pig farms in nine provinces from 2012 to 2016. The prevalence of MRSA was 7.9% (88/1119) in pigs and 16.7% (21/126) in farmers. Among 119 farmers working on conventional farms, 21 (17.6%) tested positive for MRSA. However, no MRSA was detected in either pigs or farmers at four organic farms. The individual pig-level prevalence of MRSA differed between age groups, with the percentage of positive samples being highest in weaners (17.3%), followed by growers (9.0%), piglets (6.5%), finishers (4.4%), and sows (0%). Two different lineages of MRSA were detected among the 109 isolates from pigs and farmers: (1) livestock-associated types of MRSA belonging to 27 isolates of ST541-t034-V, 24 isolates of ST398-t571-V, 17 isolates of ST398-t034 variant (G420A)-V, and one isolate of ST541-t8588-V; and (2) community-associated types of MRSA belonging to 21 isolates of ST188-t189-IV, 14 isolates of ST72-t324-IV, three isolates of ST72-t664-IV, one isolate of ST72-t148-IV, and one isolate of ST72-t5440-IV. Identical genotypes were detected in both pigs and farmers at six farms. New MRSA clones were isolated from pigs (ST398-t034 (G420A)-V, ST188-t189-IV, and ST398-t571-V) and pig farmers (ST541-t8588-V and ST72-t5440-IV). The prevalence of MRSA was also correlated with antibiotic usage, and the clones showed diversification between pigs and farmers. Ultimately, the increased frequency and diversification of livestock-associated MRSA could be a potential threat to public health in Korea. To our knowledge, this is the first study to report the prevalence and characteristics of MRSA in pigs and pig farmers in Korea.

The heavy use or abuse of antimicrobials in food animals has caused an increase in antimicrobial resistance in enterococci of animal origin, which could get transmitted to those of human origin via the food chain. Since duck meat consumption has been on the rise in Korea, we conducted this study to provide information about the antimicrobial resistance of the enterococci obtained from healthy ducks and their carcasses. A total of 82 Enterococcus faecium and 174 E. faecalis isolated from duck fecal and carcass samples were investigated for antimicrobial resistance to 16 agents, using broth dilution method, and were further characterized using molecular methods. Most of E. faecium (84.1%) and E. faecalis (87.9%) isolates were resistant to one or more antimicrobials. Multi-drug resistant (MDR) isolates were observed in both E. faecium (40.2%) and E. faecalis (33.9%) with high frequencies. High rate of resistance was observed for tetracycline, ciprofloxacin, chloramphenicol, and erythromycin in both E. faecium and E. faecalis. Resistance to gentamicin, vancomycin, and daptomycin, in both E. faecium and E. faecalis, was, if at all, very rare. However, linezolid resistance was observed in nine E. faecium (11.0%) and one E. faecalis (0.6%). All, but one, Linezolid resistant (LR) isolates were also resistant to chloramphenicol and florfenicol. The novel transferable oxazolidinone and phenicol resistant gene, optrA, was found in six E. faecium isolates. All of them co-carried phenicol exporter gene fexA. None of the LR isolates had mutation in the 23S ribosomal RNA and in the ribosomal protein L3. Six LR E. faecium isolates had Asn130Lys mutation in the ribosomal protein L4, of which five also carried optrA gene. None of the isolates carried the multi-resistance gene cfr. Transfer of oxazolidinone and phenicol resistance was observed in five among the 10 LR isolates; two of them had optrA and fexA genes. Multi-drug resistant Enterococcus that also carried the resistance gene to a last-resort antimicrobial is a major concern for public health. Thus, to prevent the introduction of last-resort antimicrobial resistance into food chain, continuous surveillance of antimicrobial resistance in duck is imperative., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Bovine mastitis caused by Prototheca has been reported globally, and its incidence is increasing in dairy herds. The present study aimed to investigate the occurrence of Prototheca and persistence of Prototheca zopfii strains in Korean dairy herds. A total of 187 (7.5%) P. zopfii strains were isolated from 2,508 quarter milk samples collected from 50 dairy farms throughout Korea from 2015 to 2017. Prototheca zopfii was isolated from one farm among the 50 farms over the 3-yr period. The P. zopfii isolates belonged to genotype 2. Overall, Prototheca-positive quarter milk samples showed high somatic cell counts with an average value of log 6.48 ± 6.54 cells/mL. Prototheca zopfii was found to be persistent in an infected farm over a 2-yr period. To the best of our knowledge, this is the first report on the presence and persistence of protothecal mastitis caused by P. zopfii genotype 2 in a Korean dairy herd. This disease leads to a significant increase in somatic cell counts in milk, which persists for more than 1 yr in the affected cow udder. These results suggest that P. zopfii could pose a serious risk to dairy herds. Thus, strict surveillance for protothecal mastitis is urgently needed and sanitary conditions regarding the environment and milk collection are essential because of the lack of effective treatment options., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)