• Korean Journal of Veterinary Research
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• v.59 no.3
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• pp.157-160
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• 2019

The production of rmtB-encoded 16S rRNA methylases has emerged as a novel mechanism promoting high-level resistance toward aminoglycosides in Gram-negative bacteria. Between 2015 and 2017, 636 distinct commensal Escherichia (E.) coli isolates were collected from different farms in South Korea to determine the prevalence and molecular characteristics of rmtB. The positive rates of rmtB between all the isolates and amikacin-resistant isolates were 1.1 and 100%, respectively. High-level aminoglycoside resistance could be transferred by conjugation from rmtB-positive donors to higher amikacin-resistance efficacies. This is the first report of 16S rRNA methylase-encoding genes in E. coli isolated from food-producing animals in Korea.

• Korean Journal of Food Science and Technology
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• v.42 no.4
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• pp.508-513
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• 2010

Ninety three strains (4.2%) of Vibrio parahaemolyticus were isolated from 2,239 samples of commercial marine products during 2006-2008 in Seoul, Korea. We examined 16 antimicrobial susceptibilities of 93 V. parahaemolyticus isolates. Antibiotic resistance of V. parahaemolyticus was most frequently observed to ampicillin (93.5%), followed by cephalothin (90.3%), streptomycin (87.1%), ticarcillin (55.9%), and amikacin (40.9%). Antibiotic susceptibility was most frequently observed to nalidixic acid, chloramphenicol and ampicillin/sulbactam (100%), followed by trimethoprim/sulfamethoxazole (98.9%), gentamicin and tetracycline (82.8%), and ceftriaxone (63.4%). In addition, the isolates also displayed intermediate resistance to kanamycin (79.6%), ciprofloxacin (64.5%), amikacin (47.3%) and cefoxitin (43.0%). All isolates were resistant to more than two drugs. The most prominent multiple drug resistance was 3 drug resistance (37.6%), followed by 4 drug (24.7%), 5 drug (17.2%), and 6 drug resistance (11.8%). The most prominent multiple drug resistance pattern was the cephalothin-streptomycin-ampicillin resistance pattern (22.6%), followed by cephalothinticarcillin-streptomycin-ampicillin (18.3%) and cephalothin-ticarcillin-streptomycin-ampicillin-amikacin (9.7%). Multiple drug resistance patterns of V. parahaemolyticus from marine products require continuous monitoring.

• Journal of Veterinary Clinics
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• v.21 no.1
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• pp.7-14
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• 2004

Bacteria that are resistant to several different groups of antibiotics have increased during the past few years. The importance of surveillance of antimicrobial resistance is now widely recognized. Unfortunately, this development has not been documented continuously in veterinary medicine in Korea. Therefore, the clinical prevalence and trend of antimicrobial susceptibility of aerobic isolates were investigated in this study. Total 121 isolates of aerobic bacteria were isolated from clinical specimens of dogs and cats at Veterinary Medical Teaching Hospital of Seoul National University from May 2001 to October 2002. Among them, the most common isolated species was Staphylococcus spp. (48 isolates), followed by E.coli (26 isolates), Enterococcus spp. (21 isolates), Klebsiella pneumoniae (9 isolates), Streptococcus spp. (6 isolates), Enterobacter cloacae (3 isolates), Pseudomonas aeruginosa (3 isolates), Corynebacterium xerosis (2 isolates), Chryseomonas spp. (2 isolates), and Providencia stuartii (1 isolate). The susceptibility of isolates to antibiotics was determined by the disk diffusion method. Gram-positive bacterial isolates were showed high susceptibilities to amikacin, amoxacillin/clavulanate, ceftazidime, and oxacillin, while Gram-negative bacterial isolates were showed high susceptibilities to amikacin and ceftazidime. Staphylococcus spp. were showed high susceptibilities to amikacin, amoxicillin/clavulanate, ceftazidime, cephalothin, and oxacillin. Streptococcus spp. and E.coli were showed high susceptibilities to amikacin and ceftazidime. Of the 48 staphylococci, seven Methicillin Resistant staphylococci were observed (14.6%), distributed among S. auricularis (1), S. hemolyticus (2), S. sciuri (1), S. saprophyticus (1), S. warneri (2) isolates. One strain of E.coli and one strain of Corynebacterium xerosis were resistant to all antibiotics tested. And, resistance trends between the you 2000 (from July 1999 to September 2000) and 2002 (from May 2001 to October 2002) were compared. Resistance to antibiotics was increased in both Gram-positive and Gram-negative bacterial isolates (p＜ 0.05). The resistance rates of Staphylococcus spp., E.coli and Klebsiella pneumoniae to all antibiotics tested were also increased (p＜0.05). This study investigated increasing resistance between the year 2000 and 2002 in Veterinary Medical Teaching Hospital of Seoul National University. Surveillance resistance is helpful to alert to veterinarian and select of appropriate therapy. Antimicrobial susceptibility surveillance of isolates should urgently be continued in veterinary medicine.

• YAKHAK HOEJI
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• v.33 no.2
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• pp.73-79
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• 1989

One hundred and sixteen strains of E. coli isolated from drainage in Seoul city in 1987 and 104 strains of E. coli isolated from stools of domestic animals in suburb of Seoul in 1987 were examined for susceptibilities to 10 antimicrobial agents by the agar dilution method. The susceptibilities of the two groups to each antimicrobial agent were compared and correlations in the antimicrobial susceptibility of the 220 strains of E. coli among the 10 antimicrobial agents were also analyzed. The frequency of resistance strains was highest to tetracycline with 77%, and followed by chloramphenicol, streptomycin, ampicillin, kanamycin and cephalosporin in the descreasing order, tanging from 62% to 10%. Strains resistant to tobramycin, nalidixic acid, gentamicin and amikacin occupied 3 strains, 2 strains, 2 strains and 1 strain respectively.

• Biomedical Science Letters
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• v.18 no.3
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• pp.299-306
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• 2012

Recently, the prevalence of 16S rRNA methylase conferring high-level resistance to aminoglycosides has been increasing in Gram-negative bacilli globally. We determined the prevalence and genotype of these methylase-producing bacteria, and characterized the co-resistance to ${\beta}$-lactam antibiotics and quinolone in Gram-negative clinical isolates collected in 2010 at a hospital in Korea. Among 65 amikacin-resistant isolates screened from 864 Gram-negative bacilli (GNB), 16S rRNA methylase genes were detected from 49 isolates, including Acinetobacter baumannii (43), Klebsiella pneumoniae (2), Proteus mirabilis (2) and Serratia marcescens (1), Empedobacter brevis (1). All of the 16S rRNA methylase genotype was armA and no variant sequences of amplified PCR products for armA were noted. The 16S rRNA methylase producing bacteria showed much higher resistance to aminoglycoside for Enterobacteriaceae and glucose non-fermenting (NF)-GNB and to imipenem for glucose NF-GNB, than the non-producing isolates. All of the 16S rRNA methylase producing Enterobacteriaceae had the extended-spectrum-${\beta}$-lactamase. In addition, two K. pneumoniae concurrently produced both plasmid-mediated AmpC ${\beta}$-lactamase and qnrB gene. All of the amikacin-resistant A. baumannii (43) co-harbored armA 16S rRNA methylase and $bla_{OXA-23}$ carbapenemase. In conclusion, 16S rRNA methylase producing bacteria were very prevalent among GNB in South Korea, and were commonly associated with co-resistance, including carbapenem and quinolone.

• Microbiology and Biotechnology Letters
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• v.49 no.4
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• pp.587-593
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• 2021

Infertility is a key issue affecting mood and behavior in men. Microorganisms are one of the primary etiological agents that may be associated with infertility. The objective of the present study was to identify bacterial causative agents from the semen of infertile subjects and determine the effect of bacterial infection on sperm quality, as well as determine the susceptibility of these bacteria to drugs. Forty semen samples from 30 infertile patients and 10 fertile individuals were collected. The pH, volume, motility, and concentration of semen were analyzed. The samples were processed and identified by biochemical testing using API identification kits. The antibiotic susceptibility pattern was determined using the disc diffusion method. Abnormal sperm quality was observed. The mean age of the individual and their sperm morphology, concentration, progressive motility, pH level, and pus cell content were 31.9 years, 2.7%, 10.4 million/ml, 27.3%, 8.3, and 5.7, respectively. Among the tested samples, oligoasthenozoospermia was found to show the highest occurrence, at 27/30 samples, followed by teratozoospermia, at 25/30 samples, and asthenozoospermia, at 22/30 samples. Of the tested infertile patients' sperm, 19, 6, and 5 isolates were identified as Escherichia coli, Klebsiella pneumonia, and Staphylococcus epidermidis, respectively. The results also revealed multi-drug resistance in the bacteria. Compared to that shown by the other tested antibiotics, amikacin showed higher activity against all isolated bacteria. However, the bacteria exhibited maximum resistance against gentamicin, cefotaxime, levofloxacin, and ampicillin. In conclusion, leukocytospermia and bacterial infections are possibly responsible for sperm abnormalities. Multi-drug resistant bacteria were detected. Gentamicin, cefotaxime, levofloxacin and ampicillin were shown the highest resistance, while amikacin was the most effective antimicrobial agent against the isolated bacteria.

• Journal of Microbiology and Biotechnology
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• v.11 no.1
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• pp.50-55
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• 2001

Different polluted water samples were collected from a wastewater treatment plant, agricultural drainage canals, the River Nile, and irrigation canals. The samples were examined for the enumeration of Pseudomonas aeruginosa in the Sohag area, Egypt over a period of one year. A total of 240 isolates were collected and tested for their resistance to 12 common antibiotics and 6 heavy metals. The isolates were found to be less resistant to norfloxacin(1.7%), ofloxacin(4.6%), amikacin(9.6%), tobramycin (10.4), carbenicillin (15.4), and gentamycin (41.3%), yet more sensitive to rifampicin (75%), kanamycin (89.6%), ampicillin (90.8%), chloramphenicol (91.7%), streptomycin (92.9%), and tetracyclin(96.3%). In contrast, 7.1%, 12.9%, 25.4%, and 53.7% of the isolates were resistant to lead, cadmium, mercury, and zinc, respectively. None of the isolates had developed a resistance to silver or molybdenum. The high frequency of metal-antibiotic double resistance existed between lead and amikacin (56.5%), cadmium and ofloxacin (72.7%), zinc and norfloxacin (100%), and mercury and carbenicillin (94.6%). The high occurrence of antibiotic-resistant bacteria in natural water could be related to the widespread use of antibiotics, with possible public health hazard.

• YAKHAK HOEJI
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• v.30 no.2
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• pp.55-61
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• 1986

A total of 130 of Staphylococcus strains isolated from various clinical specimens of admitted patients of a university hospital with systemic or severe cases of infection. All of these were tested for the antimicrobial susceptibility to 11 drugs of common use. The hospital strains isolated showed higher frequency of resistance against four drugs including gentamicin, penicillin, erythromycin, kanamycin but amikacin, cephalothin, streptomycin were effective. And also 47.7% of methicillin-resistant Staphylococcus were isolated from the clinical patients. However, isolated Escherichia coli strains showed higher frequency of resistance, but two drugs, tobramycin and gentamicin were effective to them.

• The Journal of the Korean Society for Microbiology
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• v.21 no.1
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• pp.33-45
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• 1986

On hundred and forty stains of shigella cultures isolated from the twelve hygiene laboratories of cities and provincial general hospital laboratories in 1983 were tested for their resistance to thirteen antimicrobial drugs and their R-plasmid transfer. Antimicrobial drugs were used amikacin, ampicillin, cephalothin, chloramphenicol, gentamicin, kanamycin, nalidixic acid, rifampicin, streptamycin, tetracycline, tobramycin, cefoperazone and piperacillin. All strains were resistant to one or more of thirteen antimicrobial drugs but 94.3% were susceptible to amikacin, gentamicin and tobramycin of total isolated. The most strains commonly found resistance was to chloramphenicol (94%) followed by streptamycin (93%), tetracyline (92%) piperacillin (90%) ampicillin (83%), cefoperazone (42%), nalidixic acid (14%), cephalothin (17%), rifampicin (22%) and kanamycin (6%), sixty percent of strains among 140 were resistance to ampicillin, chloramphenicol, streptomycin, tetracycline at the same time. The transfer of drug resistance by conjugation was tested and ninety four strains (94.3%) were resistant to one or more drugs were found to transfer their drug resistance of E. coli. percentage of transfer frequency by conjugation was one strains (54%), the transfer frequency of drug resistance varied by donor strains and recipients, but not by selecting drugs. Resistance to nalidixic acid was not transferred by conjugation to recipients. Percentage of plasmid curing after the treatment of acriflavine, acridine orange was about 8%. Among strains cured two strains were tested compare original strains with them in biochemical properties in arginine dihydrolase and arabinose fermentation reaction. It was found to growth curves of No.2 shigella flexneri, serotype 1b, and its derivatives cured with acriflavine in $M{\ddot{u}}ller$ Hinton broth medium (pH 7.4, $38^{\circ}C$) by temperature Gradient Biophoto Recorder TN-1120 (Tokyo, Japan).

• Tuberculosis and Respiratory Diseases
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• v.86 no.1
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• pp.47-56
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• 2023

Background: There is a global increase in isolation of nontuberculous mycobacteria (NTM). The aim of the study was to analyze longitudinal trends of NTM identification and pattern of antimicrobial susceptibility testing. Methods: NTM recovery rates, distribution of NTM species identification, and antimicrobial susceptibility pattern of NTM at Pusan National University Yangsan Hospital between January 2016 and December 2020 were retrospectively analyzed. Results: A total of 52,456 specimens from 21,264 patients were submitted for mycobacterial culture, of which 2,521 from 1,410 patients were NTM positive over five years (January 2016 to December 2020). NTM isolation showed an increasing trend from 2016 to 2020 (p<0.001, test for trend) mainly caused by Mycobacterium avium complex. The vast majority of M. avium complex were susceptible to key agents clarithromycin and amikacin. For Mycobacterium kansasii, resistance to rifampin and clarithromycin is rare. Amikacin was the most effective drug against Mycobacterium abscessus subspecies abscessus and Mycobacterium subspecies massiliense. Most of M. subspecies massiliense were susceptible to clarithromycin, while the majority of M. abscessus subspecies abscessus were resistant to clarithromycin (p<0.001). Conclusion: There was an increasing trend of NTM isolation in our hospital. Resistance to key drugs was uncommon for most NTM species except for M. abscessus subspecies abscessus against clarithromycin.