• Korean Journal of Veterinary Research
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• v.40 no.2
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• pp.301-310
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• 2000

The antimicrobial susceptibility, genotypes of enterotoxins(LT, STa) and pili(K88, 987P), and plasmid profiles were investigated with 102 Escherichia coli isolated from piglets showing diarrhea in Korea. Almost of them were susceptible to ceftiofur(99%), cefquinone(97.1%). However they showed resistance to bacitracin(100%), streptomycin(98%), vancomycin(97%), trimethoprim/sulfamethoxazole(87.2%), tetracycline(84.3%) in antimicrobial susceptibility test. Moreover, all of the isolates demonstrated resistance to more than 2, and 78% of them were resistant to more than 8 of total 17 drugs. Multiplex PCRs for genotyping of enterotoxins(LT, STa) and pili(K88, 987P) were established with primers designed based on sequences from Genebank. Seventeen strains(16.6%) of the isolates had STa gene, 11 strains(10.8%) of them had both STa and LT genes, and 18 strains(17.8%) had K88 gene. But none of the isolates harbored a gene exclusively encoding LT. The gene encoding 987P pili was not found in all isolates. Fifty-four strains of 102 isolates(52.9%) had plasmid with various sizes ranging from 125kb to 1.1kb. Numbers of plasmid per isolates were also various, from 1 to 9. Distinctive relationship between plasmid profiles and genotypes of enterotoxins and pili in the isolates was not found. These results might provide the basic knowledge to establish strategies for the treatment and prevention of colibacillosis in piglets.

• Journal of Microbiology and Biotechnology
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• v.23 no.3
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• pp.430-435
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• 2013

Multidrug resistance, especially multidrug efflux mechanisms that extrude structurally unrelated cytotoxic compounds from the cell by multidrug transporters, is a serious problem and one of the main reasons for the failure of therapeutic treatment of infections by pathogenic microorganisms as well as of cancer cells. Streptococcus mutans is considered one of the primary causative agents of dental caries and periodontal disease, which comprise the most common oral diseases. A fragment of chromosomal DNA from S. mutans KCTC3065 was cloned using Escherichia coli KAM32 as host cells lacking major multidrug efflux pumps. Although E. coli KAM32 cells were very sensitive to many antimicrobial agents, the transformed cells harboring a recombinant plasmid became resistant to several structurally unrelated antimicrobial agents such as tetracycline, kanamycin, rhodamin 6G, ampicillin, acriflavine, ethidium bromide, and tetraphenylphosphonium chloride. This suggested that the cloned DNA fragment carries a gene encoding a multidrug efflux pump. Among 49 of the multidrug-resistant transformants, we report the functional gene cloning and characterization of the function of one multidrug efflux pump, namely MdeA from S. mutans, which was expressed in E. coli KAM32. Judging from the structural and biochemical properties, we concluded that MdeA is the first cloned and characterized multidrug efflux pump using the proton motive force as the energy for efflux drugs.

• Korean Journal of Clinical Laboratory Science
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• v.37 no.3
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• pp.155-163
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• 2005

The purpose of this study is to investigate the carrier rate of S. aureus in the community, antibiotic susceptibility patterns of the organism, detection of MRSA and mecA gene in MRSA. Identification and antibiotic resistance patterns of S. aureus and MRSA were done by MicroScan Panels. MRSA strain was confirmed by disk diffusion method using oxacillin disk. The mecA gene in MRSA was detected by PCR. Eighty-four strains (27.4%) of S. aureus were isolated from the nasal specimens of 307 university students in Busan in 2004. Sixty-eight strains (81.9%) of 83 S. aureus were resistant to penicllin, 16 strains(19.3%) to erythromycin, 15 strains (18.1%) to gentamicin, 12 strains (14.5%) to tetracycline, 6 strains (7.2%) to chloramphenicol, 3 strains (3.6%) to ofloxacin, 2 strains (2.4%) to cefepime, clindamycin, imipenem, meropenem, norfloxacin, respectively. One strain (1.2%) was resistant to ciprofloxacin, cefazolin, cefotaxime, cefuroxime, and oxacillin. And all the strains (100%) of 84 S. aureus were susceptible to amoxicilin/K clavulanate, ticarcillin/K clavulanate, trimethoprim/sulfamethoxazole, rifampin, syncroid, teicoplanin, and vancomycin. One strain of 84 S. aureus isolates was methicillin-resistant Staphylococcus aureus (MRSA). The mecA gene was detected from the MRSA strain.

• Journal of Korean Society on Water Environment
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• v.28 no.6
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• pp.911-916
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• 2012

Recently, antibiotic resistant genes (ARGs) in the environment are emerging as pollutants, since these genetic contaminants can eventually be transferred to human pathogens. The aim of this study was to develop the experimental model of antibiotic resistant gene (ARG) plasmid transfer as a function of various environmental conditions. For this purpose, the multi drug resistant plasmid pB10, which is known to be originally isolated from a wastewater treatment plant, was selected as a model transfer plasmid and Escherichia coli $DH5{\alpha}$ containing pB10 was used as a model donor. Pseudomonas aeruginosa, an opportunistic pathogen, was selected as the recipient for the conjugation experiment. When the donor and recipient were exposed to various stressors including antibiotics and heavy metal as a function of the concentrations (10, 100 and, 1000 ppb), statistically increased plasmid transfer rate was observed at a concentration of 10 ppb of tetracycline and sulfamethoxazole compared to control (no antibiotic exposure). Accordingly, the developed experimental ARG model by various stressor is a promising tool for evaluating the dissemination of ARGs by micro-contaminants in aquatic environment.

• Biomedical Science Letters
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• v.5 no.1
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• pp.17-26
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• 1999

To evaluate the spreading possibilities of the marRAB mutation of E. coli Mar mutant among gram-negative bacilli, chromosomal marRAB mutations of Mar mutants were transduced by $\lambda$placMu9 into pUC19 (Lac$^{+}$, Ap$^{r}$) cloning site in another strains of E. coli or onto the chrmosome of S. typhimurium and P. aeruginosa, selected for transduction by Mar phenotype, Lac$^{-}$, or Ap$^{r}$, and tested for their antimicrobial resistance with or without addition of salicylate (SAL). Compared with wild type strains of JM109, NM522, harboring pUC19 or not, respectively, all strains of JM109 or NM522 carrying pUC19::marRAB mutation showed higher levels of antimicrobial resistance and SAL induction of Mar phenotype than those of wild type. However, in contrast to the original Mar mutants, there were some tendencies of decreased antimicrobial resistance of JM109 or NM522 harboring pUC19::marRAB mutation with SAL induction against chlorarnphenicol (Cm) and tetracycline (Tc), or Tc and ciprofloxacin (Cp), respectively. Almost the same results, as shown as the cases of E. coli JM109 or NM522, were obtained from all transductants of S. typhimurium and P. aeruginosa, except Cp, against which increased antimicrobial resistance with SAL induction was shown. This study, employed the methods of transformation or transduction among intercellular gene transfer methods between gram-negative bacteria, shows the evidences that suggest indirectly the spreading possibilities of marRAB mutation among gram-negative bacilli.

• Korean Journal of Veterinary Service
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• v.45 no.3
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• pp.171-180
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• 2022

The aim of this study was to investigate the prevalence of antimicrobial resistance and virulence factors in staphylococci isolated from canine otitis externa. A total 295 causative microorganisms were isolated. The most common isolated species were Staphylococcus (S) pseudintermedius (94 isolates) followed by Pseudomonas aeruginosa (60 isolates), S. schleiferi (25 isolates), Escherichia coli (23 isolates) and Proteus mirabilis (20 isolates). Staphylococci isolates were showed high resistance to penicillin (78.6%), erythromycin (55.9%), tetracycline (52.4%), clindamycin (51.7%) and ciprofloxacin (42.8%). Of the 145 staphylococci isolates, 49 (33.8%) methicillin-resistant staphylococci (MRS) were observed, distributed among S. pseudintermedius (n=34), S. schleiferi (n=6), S. epidermis (n=4), S. hominis (n=2), S. aureus, S. caprae and S. saprophyticus (n=1, respectively). Forty-three (87.8%) of 49 MRS and 10 (10.4%) of 96 methicillin-susceptibility staphylococci harbored mecA gene. About 80% of MRS were multidrug-resistant with resistance to at least one antibiotic in three or more antibiotic classes. Resistance genes blaZ (93/114, 81.5%), ermB (35/81, 43.2%), ermC (3/81, 3.7%), aacA-aphD (50/54, 92.5%), tetM (69/76, 90.7%) and tetK (6/76, 7.8%) were detected among resistant isolates. Virulence factors genes lukF and lukS were found in 100%(145/145) and 43.4%(63/145), respectively. Genes encoding ermA, eta, etb and tsst were not detected. To the best of our knowledge, this is the first study which investigated for the presence of genes encoding antimicrobial resistance and staphylococcal toxins in staphylococci isolated from canine otitis externa. A continuous monitoring and surveillance program to prevent antimicrobial resistance in companion animals is demanded.

• Biomedical Science Letters
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• v.11 no.4
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• pp.525-531
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• 2005

Staphylococcus aureus is a major cause of nosocomial infections and is one of the most commonly isolated bacterial species in the hospital and continues to be an important pathogen in both community and hospital-acquired infection. Methicillin resistant S. aureus (MRSA), which is associated with hospitals is now being isolated in the community. The purpose of this study is to investigate the carrier rate of S. aureus in the community, antibiotic resistance patterns of the organism, detection of MRSA and mecA gene in MRSA. Ninety strains $(46.4\%)$ of S. aureus were isolated from the nasal specimens of 194 elementary school students. Eighty-nine strains $(98.9\%)$ of 90 S. aureus were resistant to penicilin, 36 strains $(40.0\%)$ to erythromycin, 14 strains $(15.6\%)$ to fusidic acid, 11 strains $(12.2\%)$ to gentamycin, 9 strains $(10.0\%)$ to tobramycin, 5 strains $(5.6\%)$ to oxacillin, 4 strains $(4.4\%)$ to clindamycin, 2 strains $(2.2\%)$ to tetracycline, 1 strains $(1.1\%)$ to fosfomycin. None of $90(0\%)$ S. aureus isolates was resistant to ciprpfloxacin, trimethoprim/sulfamethoxazole, levofloxacin, linezolid, moxifloxacin, nitrofurantoin, norfloxacin, rifampicin, quinupristin/dalfopristin, teicoplanin, and vancomycin. Five strains $(5.6\%)$ of 90 S. aureus isolates were MRSA. The mecA gene was detected from five MRSA strains by PCR.

• Journal of Microbiology and Biotechnology
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• v.19 no.10
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• pp.1265-1270
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• 2009

The objectives of this study were to determine the antibiotypes, SCCmec subtypes, PVL carriage, and genetic diversity of MRSA strains from a tertiary hospital. Sixty-six MRSA strains were selected randomly (2003, 2004, and 2007) and tested for the Panton-Valentine leukocidin gene, mecA gene, and SCCmec type via a PCR. The antibiograms were determined using a standard disc diffusion method, and the genetic diversity of the isolates was determined by PFGE. Thirty-four antibiograms were obtained, with 55% of the 66 strains exhibiting resistance to more than 4 antimicrobials. All the isolates remained susceptible to vancomycin, and low resistance rates were noted for fusidic acid (11%), rifampicin (11%), and clindamycin acid (19%). The MRSA isolates that were multisensitive (n=12) were SCCmec type IV, whereas the rest (multiresistant) were SCCmec type III. Only two isolates (SCCmec type IV) tested positive for PVL, whereas all the isolates were mecA-positive. The PFGE was very discriminative and subtyped the 66 isolates into 55 pulsotypes (F=0.31-1.0). The multisensitive isolates were distinctly different from the multidrug-resistant MRSA. In conclusion, no vancomycin-resistant isolate was observed. The Malaysian MDR MRSA isolates were mostly SCCmec type III and negative for PVL. These strains were genetically distinct from the SCCmec type IV strains, which were sensitive to SXT, tetracycline, and erythromycin. Only two strains were SCCmec IV and PVL-positive. The infections in the hospital concerned were probably caused by multiple subtypes of MRSA.

• Korean Journal of Environmental Agriculture
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• v.41 no.4
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• pp.335-343
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• 2022

BACKGROUND: Antibiotics used in animal husbandry for disease prevention and treatment have resulted in the rapid progression of antibiotic resistant bacteria which can be introduced into the environment through livestock feces/manure, disseminating antibiotic resistant genes (ARGs). In this study, fecal samples were collected from the livestock farms located in Jeju Island to investigate the relationship between microbial communities and ARGs. METHODS AND RESULTS: Illumina MiSeq sequencing was applied to characterize microbial communities within each fecal sample. Using quantitative PCR (qPCR), ten ARGs encoding tetracycline resistance (tetB, tetM), sulfonamide resistance (sul1, sul2), fluoroquinolone resistance (qnrD, qnrS), fluoroquinolone and aminoglycoside resistance (aac(6')-Ib), beta-lactam resistance (bla_TEM, bla_CTX-M), macrolide resistance (ermC), a class 1 integronsintegrase gene (intI1), and a class 2 integrons-integrase gene (intI2) were quantified. The results showed that Firmicutes and Bacteroidetes were dominant in human, cow, horse, and pig groups, while Firmicutes and Actinobacteria were dominant in chicken group. Among ARGs, tetM was detected with the highest number of copies, followed by sul1 and sul2. Most of the genera belonging to Firmicutes showed positive correlations with ARGs and integron genes. There were 97, 34, 31, 25, and 22 genera in chicken, cow, pig, human, and horse respectively which showed positive correlations with ARGs and integron genes. In network analysis, we identified diversity of microbial communities which correlated with ARGs and integron genes. CONCLUSION(S): In this study, antibiotic resistance patterns in human and livestock fecal samples were identified. The abundance of ARGs and integron genes detected in the samples were associated with the amount of antibiotics commonly used for human and livestocks. We found diverse microbial communities associated with antibiotics resistance genes in different hosts, suggesting that antibiotics resistance can disseminate across environments through various routes. Identifying the routes of ARG dissemination in the environment would be the first step to overcome the challenge of antibiotic resistance in the future.

• Food Science of Animal Resources
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• v.37 no.2
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• pp.175-180
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• 2017

The objectives of this study were: i) to detect the presence of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) in raw milk, cheese, beef minced meat, and chicken meat samples; ii) to evaluate the antimicrobial susceptibility of the isolates; and iii) to determine clonal relation among the isolates by using pulsed-field gel electrophoresis (PFGE) method. Therefore, a total of 160 food samples were randomly collected between August 2014 and May 2015 in Hatay province, located in the southern Turkey. Twenty (12.5%) of the samples were found to be contaminated with S. aureus. A total of 40 isolates from the 20 positive samples were confirmed to be S. aureus by multiplex PCR based on 16S rRNA and nuc gene. The mec A gene was not detected in any of the S. aureus strains. In the present study, 39 out of 40 (97.5%) isolates were found to be resistant to one or more antibiotics. All of isolates were susceptible to gentamicin, oxacillin, and vancomycin. The highest resistance rate was detected in penicillin (95%) and ampicillin (92.5%), followed by tetracycline (30%), erythromycin (20%), ciprofloxacin (12.5%). Nine major patterns were determined by PFGE. In 6 of these patterns, thirty-six strains (90%) had identical PFGE profiles.