• Korean Journal of Veterinary Service
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• v.32 no.1
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• pp.93-102
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• 2009

In this study, antimicrobial resistance of E. coli isolated from domestic beef on sale in Busan and Gyeongnam province was investigated from March to October 2008. A total of 400 beef samples were collected for the monitoring of antimicrobial resistance, and 39 (9.8%) strains of E. coli were isolated. Antimicrobial resistance test was carried out by agar disc diffusion method with 17 antimicrobials. In general, E. coli isolates showed the highest antimicrobial resistance to tetracycline (85.3%), followed by doxycycline (76.5%), streptomycin (61.8%) and sulfamethoxazole/trimethoprim (61.8%). Then they showed higher resistance to several antimicrobials like kanamycin and neomycin (55.9%). However, They had low antimicrobial resistance to amikacin (8.8%), amoxicillin/clavulanic acid (2.9%). Of 39 isolates, 31 (79.5%) were resistant to more than 2 antimicrobials. Among 17 antimicrobials examined, tetracyclines were the most resistant, followed by aminoglycosides, sulfonamides. The resistance was seemed to be correlated to amounts of antimicrobial use. In the result of this study, we suggest that there be need to regulate the abuse of antimicrobial on food-producing animals in Korea because the concern on antimicrobial resistant is gradually increased worldwide.

• Korean Journal of Veterinary Research
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• v.56 no.2
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• pp.91-95
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• 2016

This study was conducted to investigate the prevalence and antimicrobial resistance of Salmonella spp. and Escherichia (E.) coli isolated from ducks in Korea. A total of 400 cecal content samples were collected from 40 duck farms in Korea. Isolated Salmonella spp. and E. coli strains were 83 and 364 of the 400 cecal samples, respectively. The most prevalent serotype among the 83 Salmonella isolates was Salmonella Typhimurium (51 isolates: 61.45%). Resistance to the tested antimicrobial agents by Salmonella isolates was low except for erythromycin, while the resistance of the E. coli isolates to the other tested antimicrobial agents was high and 90.9% (331/364) of E. coli isolates showed multi-antimicrobial resistance. Antimicrobial resistance in duck zoonotic pathogens should be of concern to the Korean duck industry, as these pathogens exhibit a high rate of antimicrobial resistance and pose a potential hazard to public health.

• Journal of Microbiology and Biotechnology
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• v.20 no.3
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• pp.637-642
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• 2010

We investigated the prevalence and the molecular characteristics of vancomycin-intermediate Staphylococcus aureus (VISA) among methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from clinical samples at tertiary or general hospitals participating in a nationwide surveillance program for VISA and vancomycin-resistant Staphylococcus aureus (VRSA) in Korea during an 8-week period in each year from 2001 to 2006. Of 41,639 MRSAs isolated, 37,856 were screened and 169 grew on brain heart infusion agar supplemented with 4 ${\mu}g/ml$ vancomycin. A vancomycin MIC of 4 ${\mu}g/ml$ was confirmed for 33 VISA isolates of the 169 isolates. Eighteen of the 33 isolates were classified as hetero-VISA (hVISA) by the population analysis profile (PAP) method. All VISA isolates were susceptible to linezolid, tigecycline, and quinupristin-dalfopristin. Most VISA isolates (MIC 4 ${\mu}g/ml$) showed a PFGE C pattern with sec, seg, and sei enterotoxin genes, including ST5-SCCmec type II, or a PFGE A pattern with sea, including ST239-SCCmec type III.

• Korean Journal of Veterinary Service
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• v.42 no.4
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• pp.251-255
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• 2019

Wildlife is a bio-indicator of environmental pollution by antimicrobial resistant bacteria or genes, however, there is no information on antimicrobial resistance in wildlife-origin bacteria. This study aimed to investigate the normal microbiota of staphylococci and their antimicrobial resistance in wildlife that did not take any antimicrobials. After sampling and bacterial isolation/identification, antimicrobial resistance profiles were examined by broth microdilution test, Kirby-Bauer disc diffusion test and mecA genetargeted PCR. Of 90 isolates from wildlife, 83 were coagulase-negative staphylococci while only 7 were coagulase-positive staphylococci. Methicillin-resistance was found in 63 (70%) isolates and 35 of 90 (38.9%) isolates were multidrug-resistant staphylococci. When considering that all of the animals did not take any medication or contacted any medical device before the sampling, the results indicate significantly high prevalence of antimicrobial resistance in wild environments. Further study would be necessary to investigate the transmission route of antimicrobial resistance.

• Korean Journal of Veterinary Service
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• v.31 no.1
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• pp.17-29
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• 2008

In this study, antimicrobial resistance of E coli isolated from domestic beef on sale in Busan and Gyeongnam province was investigated from March to October 2007. A total of 600 beef samples were collected for the monitoring of antimicrobial resistance, and 92 (15.3%) strains of E coli were isolated. Antimicrobial resistance test was carried out by agar disc diffusion method with 17 antimicrobials. In general, E coli isolates showed the highest antimicrobial resistance to doxycycline (73.9%), followed by tetracycline (70.7%) andcefazolin (63.0%). Then they showed higher resistance to several antimicrobials like norfloxacin (48.9%). However, They had low antimicrobial resistance to amikacin (4.3%), colistin (1.1%). Of 92 isolates, 82 (89.1%) were resistant to more than 2 antimicrobials. Among 17 antimicrobials examined, tetracyclines were the most resistant, followed by cephalosporins, quinolone. The resistance was seemed to be correlated to amounts of antimicrobial use. In the result of this study, we suggest that there be need to regulate the abuse of antimicrobial on food-producing animals in Korea because the concern on antimicrobial resistant is gradually increased worldwide.

• Journal of Microbiology and Biotechnology
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• v.31 no.5
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• pp.733-739
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• 2021

Acinetobacter strains are widely present in the environment. Some antimicrobial-resistant strains of this genus have been implicated in infections acquired in hospitals. Genetic similarities have been reported between Acinetobacter strains in nosocomial infections and those isolated from foods. However, the antimicrobial resistance of Acinetobacter strains in foods, such as meat, remains unclear. This study initially aimed to isolate Campylobacter strains; instead, strains of the genus Acinetobacter were isolated from meat products, and their antimicrobial resistance was investigated. In total, 58 Acinetobacter strains were isolated from 381 meat samples. Of these, 32 strains (38.6%) were from beef, 22 (26.5%) from pork, and 4 (4.8%) from duck meat. Antimicrobial susceptibility tests revealed that 12 strains were resistant to more than one antimicrobial agent, whereas two strains were multidrug-resistant; both strains were resistant to colistin. Cephalosporin antimicrobials showed high minimal inhibitory concentration against Acinetobacter strains. Resfinder analysis showed that one colistin-resistant strain carried mcr-4.3; this plasmid type was not confirmed, even when analyzed with PlasmidFinder. Analysis of the contig harboring mcr-4.3 using BLAST confirmed that this contig was related to mcr-4.3 of Acinetobacter baumannii. The increase in antimicrobial resistance in food production environments increases the resistance rate of Acinetobacter strains present in meat, inhibits the isolation of Campylobacter strains, and acts as a medium for the transmission of antimicrobial resistance in the environment. Therefore, further investigations are warranted to prevent the spread of antimicrobial resistance in food products.

• Korean Journal of Veterinary Research
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• v.48 no.3
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• pp.275-285
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• 2008

Antimicrobial drugs are widely used in poultry industry as growth promoters or to control infectious diseases. However, this practice is reported to have caused high resistance to antimicrobial drugs in normal chicken flora and pathogens. Antimicrobial resistance to Escherichia coli (E. coli) from chicken has been mainly reported in normal flora, but rare in pathogenic organism in Korea, recently. Therefore, this study was conducted to investigate prevalence of antimicrobials resistance, transfer of R plasmid, and association between antimicrobial drug resistance and O serotype of 203 pathogenic E. coli from poultry in Korea during the period from April 2003 to December 2005. These isolates showed a high resistance to tetracycline (Tc, 93.6%), nalidixic acid (Na, 92.6%), streptomycin (Sm, 81.8%), ampicillin (Ap, 77.3%), ciprofloxacin (Ci, 70.9%), sulfisoxazole (Su, 66.5%), and trimethoprim (Tp, 58.1%). Two hundred-one (99.0%) of the isolates were resistant to one or more drugs. They showed 57 different resistant patterns, and the most prevalent resistant pattern among them was Tc, Sin, Su, Ap, Tp, Ci, Na. Sixty-eight (33.8%) of the isolates transferred all or a part of their antimicrobial resistant pattern to the recipient strain by R plasmid. The most common antimicrobial resistant pattern was Tc, Sm, Su, Ap, Tp, Ci, Na in serotype O78, O88 and O15, respectively. These results exhibit high individual and multiple resistance to antimicrobials of pathogenic E. coli from poultry in Korea. They also suggest the needs for surveillance to monitor antimicrobial resistance in pathogenic bacteria that can be potentially transmitted to humans from food animals and to regulate the abuse of antimicrobials on food-producing animals in Korea.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2000.04a
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• pp.3-6
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• 2000

Antimicrobial resistance has been a well-recognized problem ever since the introduction of penicillin into clinical use. History of antimicrobial development can be categorized based on the major antibiotics that had been developed against emerging resistant $pathogens^1$. In the first period from 1940 to 1960, penicillin was a dominating antibiotic called as a "magic bullet", although S.aureus armed with penicillinase led antimicrobial era to the second period in 1960s and 1970s. The second stage was characterized by broad-spectrum penicillins and early generation cephalosporins. During this period, nosocomial infections due to gram-negative bacilli became more prevalent, while those caused by S.aureus declined. A variety of new antimicrobial agents with distinct mechanism of action including new generation cephalosporins, monobactams, carbapenems, ${\beta}$-lactamase inhibitors, and quinolones characterized the third period from 1980s to 1990s. However, extensive use of wide variety of antibiotics in the community and hospitals has fueled the crisis in emerging antimicrobial resistance. Newly appeared drug-resistant Streptococcus pneumoniae (DRSP), vancomycin-resistant enterococci (VRE), extended-spectrum ${\beta}$-lactamase-producing Klebsiella, and VRSA have posed a serious threat in many parts of the world. Given the recent epidemiology of antimicrobial resistance and its clinical impact, there is no greater challenge related to emerging infections than the emergence of antibiotic resistance. Problems of antimicrobial resistance can be amplified by the fact that resistant clones or genes can spread within or between the species as well as to geographically distant areas which leads to a global concern$^2$. Antimicrobial resistance is primarily generated and promoted by increased use of antimicrobial agents. Unfortunately, as many as 50 % of prescriptions for antibiotics are reported to be inappropriate$^3$. Injudicious use of antibiotics even for viral upper respiratory infections is a universal phenomenon in every part of the world. The use of large quantities of antibiotics in the animal health industry and farming is another major factor contributing to selection of antibiotic resistance. In addition to these background factors, the tremendous increase in the immunocompromised hosts, popular use of invasive medical interventions, and increase in travel and mixing of human populations are contributing to the resurgence and spread of antimicrobial resistance$^4$. Antimicrobial resistance has critical impact on modem medicine both in clinical and economic aspect. Patients with previously treatable infections may have fatal outcome due to therapeutic failure that is unusual event no more. The potential economic impact of antimicrobial resistance is actually uncountable. With the increase in the problems of resistant organisms in the 21st century, however, additional health care costs for this problem must be enormously increasing.

• Animal Bioscience
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• v.35 no.1
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• pp.138-146
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• 2022

Objective: The objective of the current study was to investigate the influences of conventional (CO) and deep litter (DE) systems on antimicrobial resistance in fecal Escherichia coli (E. coli). Methods: A cross-sectional study was carried out to detect antimicrobial resistance to E. coli in swine fecal samples in CO and DE systems located in western and northeastern Thailand. Individual rectal swab samples were taken only from healthy pigs. A total of 215 individual and healthy pigs were randomly selected for isolation and antimicrobial susceptibility test of E. coli by the disc diffusion method. The test panel included amoxicillin (AMX), colistin, doxycycline (DOX), enrofloxacin, gentamicin (GEN), kanamycin, neomycin (NEO), and trimethoprim-sulfamethoxazole (SXT). Results: There were significant (p<0.05) lower resistance levels for GEN, NEO, and SXT in the DE farms compared to those in the CO farms. There was a lower number of antimicrobial resistance agents (p<0.001) in the DE farms compared to those in the CO farms. This result was consistent with those in western (p<0.01) and northeastern (p<0.01) Thailand. Overall, antibiograms of AMX-SXT and AMX-DOX-SXT were found in the CO (19.09% and 20.91%, respectively) and the DE (16.19% and 24.76%, respectively) farms. No antimicrobial resistance (5.71%) was found and AMX (13.33%) resistant pigs in the DE farms, whereas the pattern of AMX-GEN-SXT (6.36%) and AMX-DOX-GEN-SXT (11.82%) resistant pigs was found in the CO farms. Conclusion: The DE system for pig farming was superior to conventional pig farming by lowering the resistance level of fecal E. coli to GEN, NEO, and SXT, with decreasing the number of antimicrobial resistance agents and inducing a small proportion of pigs to be free from antimicrobial resistance.

• Korean Journal of Veterinary Research
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• v.54 no.3
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• pp.131-137
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• 2014

The purpose of present study was to investigate the antimicrobial resistance in Escherichia coli isolated from healthy animals in all provinces of the Republic of Korea. A total of 2,085 E. coli strains isolated from 11,336 fecal samples of healthy animals during 2010-2012 were examined for antimicrobial resistance. Comparison of average resistance rate through the years revealed that tetracycline (47.0% and 76.1%) and streptomycin resistance (42.6% and 64.6%) was most frequently observed in cattle and pigs, respectively. Whereas, in chicken isolates, resistance against nalidixic acid (90.9%) was highest among the antimicrobials tested. Percentage of E. coli that showed multidrug resistance (resistance against ${\geq}$ three subclasses of antimicrobial agents) was 17.6% (151/860) in cattle, 69.4% (506/729) in pigs, and 86.1% (427/496) in chickens. Overall, the rates of resistance are apparently different between animal species and, in particular, resistance was less prevalent in cattle than in pigs and chickens. In conclusion, this study showed higher prevalence of resistance in commensal E. coli strains to antimicrobial agents in Korean livestock and highlighted the urgent need for measures to regulate the abuse of antimicrobial agents.