• Korean Journal of Clinical Laboratory Science
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• v.45 no.1
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• pp.21-25
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• 2013

Acinetobacter baumannii is an aerobic, gram-negative and glucose-non-fermenting bacterium, which has emerged as a serious opportunistic pathogen. Many clinical microbiology laboratories use the Vitek 2 system for the routine antimicrobial susceptibility testing process, including testing on A. baumannii isolates. However, in case of amikacin, it is now recommended to perform additional antimicrobial susceptibility testing for A. baumannii strains due to the relatively lower minimum inhibitory concentration (MIC) in the Vitek 2 system compared to conventional reference methods. In our study, we assessed MIC for amikacin susceptibility testing of A. baumannii isolates in the Vitek 2 system, the agar dilution, Etest, and disk diffusion method. We collected 40 gentamicin-resistant, A. baumannii strains (amikacin MIC by Vitek 2:${\leq}2{\mu}g/mL$, 2 isolates; $4{\mu}g/mL$, 34 isolates; $8{\mu}g/mL$, 4 isolates) from a University hospital and compared the Vitek 2 system to other reference methods for testing susceptibility to amikacin. The Vitek 2 system showed major errors in all of the 40 isolates, yielding a low MIC. The results of our study strongly suggested that the Vitek 2 system was not a reliable method to test the MICs of gentamicin; ranging from ${\geq}16{\mu}g/mL$ for amikacin susceptibility. Other tests, such as agar dilution, Etest, or disk diffusion methods, should be paralleled to determine the MIC of amikacin in A. baumannii.

• Biomedical Science Letters
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• v.19 no.2
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• pp.132-141
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• 2013

Mycobacterium isolates were retrospectively identified, antibiotics susceptibility test results and basic clinical data were analyzed for the 715, excepted 308 in 1,023 specimens, from a mycobacterial laboratory at a tertiary care hospital from September 2002 to December 2008. Their male to female ratio was 1.12 to 1 (379 male, 336 female). The median age of study population was 47 years (range from 10 to 93 years). Distribution of Mycobacterium species was 90.1% of total were isolates Mycobacterium tuberculosis, and 9.9% of the total non-tuberculosis Mycobacterium isolated, and Among nontuberculosis Mycobacterium isolates, 60.6% were Mycobacterium avium complex, 14.1% were isolates Mycobacterium abscessus, and 12.7% were isolates Mycobacterium intracellulare. Among 526 Mycobacterium tuberculosis isolates, 81.7% isolates were susceptible to first line antibiotics, 18.3% were resistant to one or more antibiotics. Non-tuberculosis Mycobacterium isolates, all were resistant to two or more antibiotics. Multi-antibiotic resistant tuberculosis rate was show 10.2% of total specimens. Isolated Mycobacterium species, 19.2% were multi-antibiotic resistant tuberculosis, and the rate of nontuberculosis Mycobacterium resistant to isoniazid and rifampin was very highly 84.5%. Thus among acid fast bacilli culture positive cases, Mycobacterium tuberculosis and non-tuberculosis Mycobacterium were must exactly identification and antibiotic sensitivity test. It was considered to help to select of the antibiotic in preventive medicine.

• Mycobiology
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• v.48 no.2
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• pp.148-152
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• 2020

We investigated the antifungal susceptibilities and the cyp51 mutant strains among Aspergillus fumigatus clinical isolates obtained from 10 university hospitals in Korea. Of the 84 isolates examined, two itraconazole-resistant isolates were found with no amino acid substitution in the cyp51A/cyp51B genes. However, 19 (23.2%) azole-susceptible isolates harbored amino acid substitutions: Nine isolates harbored one to five mutations in cyp51A with high polymorphism, and 11 isolates exhibited the same Q42L mutation in cyp51B. Overall, a low azole resistance rate and high frequency of cyp51A/cyp51B amino acid substitutions were observed in the azole-susceptible A. fumigatus isolates in Korea.

• Korean Journal of Veterinary Service
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• v.35 no.2
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• pp.99-104
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• 2012

Otitis externa (OE) is a frequent disease in the ear canals of dogs. To identify the pathogens causing OE in dogs and to determine their antimicrobial resistances, specimens were collected from animal hospitals in Daejeon. The isolates were examined by morphological and biochemical tests, 16S rRNA analysis and antimicrobial susceptibility tests. We analyzed correlation between the isolated pathogens and external factors of dogs such as breed, age, gender, ear mite, hair in ears and experience with antibiotic therapy. Thirty three strains of bacteria were isolated from 26 of the 68 heads of dogs with OE. The most isolated bacteria were Enterococcus faecalis (E. faecalis) followed by Staphylococcus aureus (Sta. aureus), Sta. pseudointermedius, E. faecium, E. avium and Streptococcus canis (Strep. canis) in order of frequency of occurrence. Isolation frequency of Enterococcus spp. and Staphylococcus spp. were 51.5% and 45.5%, respectively. E. faecalis and E. faecium isolates showed VanB phenotype, which is resistant to vancomycin but sensitive to teicoplanin were 58% and 25%, respectively. Nine isolates among total twelve isolates of E. faecalis were isolated from the dogs treated with antibiotics. There was no methicillin-resistant Sta. aureus (MRSA), but were MR-Sta. pseudointermedius (MRSP) (57.1%) and vancomycin-resistant (VR)-Sta. pseudointermedius (14.3%) (VRSP) showing VanB phenotype. However, vanA, vanB and vanC genes were not detected in VR isolates from the dogs. Taken together, VR-Enterococcus spp. (VRE) is one of the major pathogens in domestic animals, as well as community-and hospital-acquired infection.

• Biomedical Science Letters
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• v.25 no.3
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• pp.275-281
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• 2019

This study was performed to characterize the chromosomal metallo-${\beta}$-lactamases (MBLs) of Chryseobacterium indologenes isolated from Korea and to propose a clustering method of IND MBLs based on their amino acid similarities. Chromosomal MBL genes were amplified by PCR from 31 clinical isolates of E. indologenes. Nucleotide sequencing was performed by the dideoxy chain termination method using these PCR products. Antimicrobial susceptibilities were determined by the agar dilution method. PCR experiments showed that all 31 E. indologenes isolates contained all $bla_{IND}$ genes. DNA sequence analysis revealed that E. indologenes isolates possessed ten types of $bla_{IND}$ gene, including seven novel variants ($bla_{IND-8}$ to $bla_{IND-14}$). The most common combination of MBL was IND-2 (n = 18). Minimum inhibitory concentrations of imipenem and meropenem for the isolates harboring novel IND MBLs were ${\geq}16{\mu}g/mL$. IND MBLs were grouped in three clusters, based on amino acid similarities.

• Journal of Microbiology
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• v.45 no.4
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• pp.358-363
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• 2007

Multi-drug resistant Pseudomonas aeruginosa has been implicated in a variety of serious therapeutic problems in clinical environments. Among the 968 P. aeruginosa isolates obtained from two hospitals in Daegu, Korea, we acquired 17 isolates that were resistant to all available tested antimicrobial agents, with the exception of colistin (colistin-only sensitive). We characterized the antimicrobial susceptibilities, $metallo-{\beta}-lactamases$, and epidemiological relatedness among the colistin-only sensitive P. aeruginosa isolates. All colistin-only sensitive isolates were positive in the modified Hodge test and imipenem-EDTA synergy test, thereby indicating the production of $metallo-{\beta}-lactamases$. 11 isolates from the secondary hospital and six isolates from the tertiary teaching hospital harbored $bla_{VIM-2}$ and $bla_{IMP-1}$, respectively. The pulsed-field gel electrophoretic analysis of the SpeI-digested DNA from P. aeruginosa isolates indicated that two different clones of colistin-only sensitive P. aeruginosa originated from each hospital, and had spread within the hospital environment. Overall, colistin-only sensitive P. aeruginosa was detected in Korea for the first time, but no pan-drug resistant bacteria were identified. Nationwide surveillance is required in order to monitor the emergence of colistin-only sensitive or pan-drug resistant bacteria.

• Microbiology and Biotechnology Letters
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• v.50 no.4
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• pp.488-500
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• 2022

Most fungal infections by opportunistic yeast pathogens such as Candida spp. are the major causes of morbidity and mortality in patients with lowered immune. Previous studies have reported that some strains of Candida secret secondary metabolites play an important role in the decreasing of immunity in the infected patient. In this study, 110 Candida spp. were isolated from different clinical specimens from Baghdad hospitals. Candida isolates were identified by conventional methods, they were processed for Candida speciation on CHROMagar. The results of identification were confirmed by internal transcribed spacer (ITS) sequencing. Phylogenetic trees were analyzed with reference strains deposited in GenBank. Antifungal susceptibility testing was evaluated by the disc diffusion method and performed as recommended by the Clinical and Laboratory Standard Institute (CLSI) M44-A document. Candida isolates investigated produce secondary metabolites gliotoxin with HPLC technique and quantification. Out of 110 Candida isolates, C. albicans (66.36%) was the most frequent isolate, followed by the isolates of C. tropicalis (10.9%) and C. glabrata (6.36%) respectively. Concerning the antifungal susceptibility test, Candida isolates showed a high level of susceptibility to Miconazole (70.9%), Itraconazole (68.2%), and Nystatine (64.5%). The ability of obtained isolates of Candida spp. to produce gliotoxin on RPMI medium was investigated, only 28 isolates had the ability to secret this toxin in culture filtrates. The highest concentrations were detected in C. albicans (1.048 ㎍/ml). Gliotoxin productivity of other Candida species was significantly lower. The retention time for gliotoxin was approximately 5.08 min.

• Clinical and Experimental Pediatrics
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• v.56 no.8
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• pp.332-337
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• 2013

Purpose: To identify the frequency of bacterial isolates in early-onset neonatal sepsis (EONS) and their antimicrobial resistance pattern. Methods: A retrospective study of EONS was conducted at the Beni Suef University Hospital from September 2008 to September 2012. A case of EONS was defined as an infant who had clinical signs of infection or who was born to a mother with risk factors for infection, and in whom blood culture obtained within 72 hours of life grew a bacterial pathogen. Results: Of 673 neonates screened, there were 138 positive blood cultures (20.5%) (confirmed EONS). Of the recovered isolates, 86.2% were gram-negative pathogens. Klebsiella pneumoniae (42.8%), Enterobacter cloacae (22.5%), and Escherichia coli (13.8%) were the commonest isolated organisms. The most common gram-positive microorganism was Staphylococcus aureus accounting for only 12 isolates (8.7%). All Klebsiella isolates and 93% of Enterobacter isolates were resistant to ampicillin. Gram-negative pathogens had the maximum overall sensitivity to imipenem, cefepime, and ciprofloxacin; whereas, gram-positive isolates were most susceptible to vancomycin, imipenem, and piperacillin. Conclusion: K. pneumoniae was the predominant causative bacteria of EONS followed by E. cloacae and E. coli. There was a high resistance to ampicillin. Imipenem had the maximum overall activity against the causative bacteria. Continuous surveillance is needed to monitor the changing epidemiology of pathogens and antibiotic sensitivity.

• Biomolecules & Therapeutics
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• v.1 no.2
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• pp.177-182
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• 1993

From 84 clinical isolates of Staphylococcus species, ten strains showing inducible resistance to MLS antibiotics were selected by disk agar diffusion method. Colony hybridization was executed using two MLS inducible resistance genes, ermA and ermC, previously identified from S. aureus as probes. S. hemolyticus 401 and S. epidermidis 542 whose genes were not homologous to those probes were finally selected. It was determined that the resistance genes of S. hemolyticus 401 and S. epidermidis 542 were not homologous to ermA, ermC and ermAM by Southern hybridization. S. epidermidis 542 had a plasmid DNA. To know if the plasmid may have genes related to inducible resistance, it was attempted to transform B. subtilis BR151 and S. aureus RN4220 with the plasmid prepared from S. epidermidis 542. It was shown that the gene related to inducible resistance to MLS antibiotics did not exist in this plasmid. These results indicate that two clinical isolates of S. hemolyticus 401 and S. epidermidis 542 had novel genes which were not homologous to MLS resistance genes identified previously. It was assumed that these genes may exist in chromosomal DNA.

• The Journal of the Korean Society for Microbiology
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• v.22 no.1
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• pp.55-59
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• 1987

Salmonella typhi infection, which was the most frequent enteric infection in Korea, has been decreasing, while the infection of other serogroups of Salmonella has been increasing since the later part of 1970s. In 1986, the number of serogroup B isolated by us increased to 46, which corresponds 21.1% of all enteropathogenic bacteria isolated from stool specimens. Salmonella isolates resistant to antimicrobial agents were extremly rare in Korea, in the 1970s. However, 7 of 13 serogroup B isolates showed resistance to ampicillin or to chloramphenicol in 1984. Among the serogroup B isolates in 1986, 71.7% and 69.6% were resistant to ampicillin and to chloramphenicol respectively. The minimum inhibitory concentrations of ampicillin and chloramphenicol against these isolates were >$128\;{\mu}g/ml$ and $128\;{\mu}g/ml$ respectively.