Mi Hee Jang, Go Eun Choi, Chulhun L. Chang, Yeong Dae Kim
Ann Clin Microbiol 2011 June, 14(2): 41-47. Published on 20 June 2011.
Molecular strain typing of Mycobacterium tuberculosis is important for the detection of outbreaks of tuberculosis and laboratory cross contamination, as well as the differentiation between re-infection and reactivation of tuberculosis. In the present review, the authors investigated the currently available typing methods for M. tuberculosis and the current status of strain distribution in Korea. IS6110-restriction fragment length polymorphism (RFLP), which is considered a standard method, is based on numbers and positions of the insertion sequence, IS6110. The method has an excellent discriminatory power with a considerable amount of worldwide data, although it is time-consuming and labor-intensive. Spoligotyping is based on the presence or absence of spacer sequences between direct repeat (DR) regions. PCR amplification allows for the possibility of application in the early suspicious stage. The data can be easily digitized; however, it shows identical profiles in Beijing family strains. Mycobacterial interspersed repetitive unit-variable number of tandem repeat (MIRU- VNTR) is another PCR-based genotyping method with a good discrimination power whose data can also be easily digitized. In Korea, the prevalence of Beijing family strains have been as high as 80 to 87%.
[in Korean]
Hee-Jung Kim, Nam Yong Lee, Sunjoo Kim, Jeong Hwan Shin, Mi-Na Kim, Eui-Chong Kim, Sun Hoi Koo, Nam Hee Ryoo, Jae-Seok Kim, Ji-Hyun Cho
Ann Clin Microbiol 2011 June, 14(2): 48-54. Published on 20 June 2011.
Background: Blood culture is important for determining the etiologic agents of bacteremia and fungemia. Analyses of blood culture results and antimicrobial susceptibility can provide clinicians with relevant information for the empirical treatment of patients. The present study was conducted to assess the frequencies and antimicrobial resistance patterns of clinically important microorganisms from nine hospitals.
Methods: Data including microbiological isolates and corresponding antimicrobial susceptibility test results were collected during 2009 from nine and five university hospitals, respectively. Microorganism identification was based on conventional methods. Antimicrobial susceptibility was tested using the VITEK II system or the Clinical and Laboratory Standards Institute disk diffusion method.
Results: Of 397,602 blood specimens cultured from nine hospitals, 34,708 (8.7%) were positive for microorganisms. Excluding coagulase-negative Staphylococci (CoNS), Escherichia coli was the most common isolate (13.5%), followed by Staphylococcus aureus (11.5%), Klebsiella pneumoniae (6.5%) and Enterococcus faecium (3.4%). The isolation rate of CoNS was 23.6%, while that of ceftazidime-resistant E. coli showed geographic differences ranging from 11% to 28%. Among the Gram-negative isolates, A. baumannii displayed the highest levels of resistance. The total isolation rate of the Candida species increased compared to the previous reported rate in Korea.
Conclusion: Among the isolates, CoNS was the most common, followed by E. coli and S. aureus. The gradual increase in the prevalence of extended-spectrum β-lactamase (ESBL) producers has contributed to the increase in multi-drug resistance among bacterial isolates from bloodstream infections.
Sangsun Hwang, Ki Jin Oh, In Ho Jang, Young Uh, Kap Jun Yoon, Hyo Youl Kim, Young Keun Kim
Ann Clin Microbiol 2011 June, 14(2): 55-59. Published on 20 June 2011.
Background: The AdvanSure TB/NTM real-time PCR kit (AdvanSure) was newly developed in Korea to detect Mycobacterium tuberculosis and nontuberculous mycobacteria (NTM) utilizing a specific primer and TaqMan probe targeting the IS6110 and rpoB genes which are unique to these species. The purpose of the present study was to evaluate the clinical utility of AdvanSure by comparing the results of acid-fast staining, mycobacteria culture, COBAS Amplicor MTB PCR (Amplicor), and AdvanSure.
Methods: A total of 182 specimens (105 respiratory and 77 nonrespiratory specimens) were obtained from 165 patients, and acid fast bacilli (AFB) staining, mycobacteria culture, and Amplicor were performed on all specimens. AdvanSure was also performed on the above specimens using the SLAN real-time PCR detection system. The sensitivity and specificity of AdvanSure were analyzed using AFB staining and culture.
Results: Of the 182 specimens, M. tuberculosis was detected in 43 specimens and NTM was detected in 12 specimens according to PCR and/or culture. The sensitivity and specificity of the AdvanSure based on AFB culture were 97.3% (36/37) and 95.5% (127/ 133) in M. tuberculosis and 75.0% (9/12) and 100% (0/133) in NTM, respectively.
Conclusion: AdvanSure could be useful for detecting M. tuberculosis and NTM in the clinical laboratory with high sensitivity and specificity.
[in Korean]
Hye Hyun Cho, Ji Youn Sung, Kye Chul Kwon, Jin Sook Lim, Sun Hoe Koo
Ann Clin Microbiol 2011 June, 14(2): 60-66. Published on 20 June 2011.
Background: Enterococcus faecium has emerged as an important nosocomial pathogen worldwide, and this trend has been associated with the dissemination of a genetic lineage designated clonal complex 17 (CC17). In the present study, characterization of the glycopeptide resistance mechanism, genetic relatedness, and pathogenicity in isolates of vancomycin-resistant E. faecium in the Chungcheong area were investigated.
Methods: A total of 37 consecutive, non-duplicate, vancomycin-resistant E. faecium were isolated at three university hospitals in the Chungcheong area. The mechanism of glycopeptide resistance and pathogenicity factors were studied using PCR, and the genetic relatedness was determined via multilocus sequence type and esp repeat profile analysis. Additionally, the quinolone resistance-determining regions of parC and gyrA were sequenced to identify mutations involved in ciprofloxacin resistance.
Results: Two genotypes of VRE were confirmed: VanA- phenotype vanA genotype VRE (25 isolates) and VanB-phenotype vanA genotype VRE (12 isolates). MLST analysis revealed five sequence types. A significant result was that ST414 and CNS4 (4-1- 1-1-1-1-1) were considered as belonging to CC17. The esp and hyl genes were found in 100% and 86.4% of the isolates, respectively. A total of 37 isolates showed genetic mutations in parC and gyrA.
Conclusion: All isolated strains in the present study belonged to one of the CC17 genotypes including ST414 and CNS4 (4-1-1-1-1-1-1), which were not previously detected in Korea. The combination of MLST and the esp gene repeat profiles can be useful for genetic characterization of VREF isolates with regard to the evolutionary process and epidemiology of the clones.
Hye Won Jeong, Bo Ra Son, Dong Ick Shin, Donghee Ryu, Seung Bok Hong, Kyudong Han, Kyeong Seob Shin
Ann Clin Microbiol 2011 June, 14(2): 67-73. Published on 20 June 2011.
Background: In the present study, the resistance mechanisms against carbapenems and aminoglycosides for 23 strains of multi-drug-resistant Acinetobacter baumannii isolated at a university hospital were investigated.
Methods: The minimal inhibitory concentrations (MICs) were determined via broth microdilution or Etest. The genes encoding OXA-type carbapenemases and 16S rRNA methylase were identified using multiplex PCR, and the amplified products were sequenced. Conjugation experiments were conducted, and an epidemiologic study was performed using enterobacterial repetitive intergenic consensus (ERIC)-PCR.
Results: In the isolates, the MICs of the tested aminoglycosides, including arbekacin, were ＞1024 μg/ mL; the MICs of aztreonam, cefepime, ceftazidime, and ciprofloxacin ranged from 64 to 128 μg/mL; and the MICs of carbapenem ranged from 32 to 64 μg/ mL, as determined through the broth microdilution test. According to the E-test, the MICs of ampicillin/ sulbactam and colistin were 8 and 0.25 to 0.38 μg/ mL, respectively. Sequence analysis confirmed that all of the isolates expressed carbapenemases OXA- 23 and OXA-66, as well as armA 16S rRNA methylase. In addition, ISAba1 was identified upstream of the gene encoding OXA-23. OXA-23 and armA were not transferred to Escherichia coli J53 cells in the transconjugation experiments. ERIC-PCR molecular fingerprinting produced a single pattern in all cases.
Conclusion: The co-production of OXA-23 and armA 16S rRNA methylase may be attributed to the multi- drug resistance of the A. baumannii isolates in the present study. Stricter surveillance and more rapid detection are necessary to prevent the spread of this type of resistance in the future.
Hee Jin Huh, Eu Suk Kim, Seok Lae Chae
Ann Clin Microbiol 2011 June, 14(2): 74-78. Published on 20 June 2011.
Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a major nasocomial pathogen. The active surveillance of MRSA is essential to limit its transmission. The BD GeneOhm MRSA real-time PCR assay (Becton Dickinson Diagnostics, San Diego, USA) has been recently developed and used for same-day MRSA detection directly from nasal swab specimens. The authors of the present study compared GeneOhm MRSA PCR with culture methods to evaluate its diagnostic performance for MRSA active surveillance.
Methods: The present study was conducted on patients admitted to the ICU for six months. A total of 371 nasal swab specimens were obtained from patients at admission day and at the seven-day follow-up. The swab was streaked onto culture media, and presumptive S. aureus colonies were confirmed as MRSA using the BD Phoenix automated microbiology system (Becton Dickinson Diagnostic Systems, Sparks, USA). In addition, GeneOhm MRSA PCR was performed. For discrepant results between GeneOhm MRSA PCR and culture, the enrichment broth culture method was performed.
Results: There were 34 samples with discrepant results between the GeneOhm MRSA PCR and culture. The overall agreement was 90.7%. For the detection of MRSA, the GeneOhm MRSA PCR was 96.8% sensitive and 86.3% specific, with positive and negative predictive values of 83.9% and 97.3%, respectively.
Conclusion: Identification of MRSA-colonized patients was achieved in as little as two hours, and the high negative predictive value of GeneOhm MRSA PCR suggests that the assay is a rapid method for the identification of persons who are not colonized with MRSA. However, due to the low positive predictive value, GeneOhm MRSA PCR combined with enrichment culture in cases of positive GeneOhm MRSA PCR is potentially useful for active MRSA surveillance activities.
[in Korean]
Young In Kim, Kyoung Un Park, Il Joong Park, Seo-Jin Park, Wee Gyo Lee
Ann Clin Microbiol 2011 June, 14(2): 79-82. Published on 20 June 2011.
Listeria grayi is a catalase-positive, non-spore forming, and glucose-fermenting Gram-positive rod. L. grayi is widely distributed in environments such as soil, water and fresh food. Human infection by L. grayi is very rare, and there have been no cases reported in Korea, and only two cases worldwide. Dermabacter hominis is a relatively new species belonging to the coryneform bacteria and is a component of the normal human skin flora. D. hominis is a non-motile, glucose-fermenting, Gram-positive rod that has similar biochemical characteristics to L. grayi. The authors of the present study report a case initially misidentified as L. grayi via a traditional morphological and biochemical identification method but that was subsequently confirmed as D. hominis using sequence analysis of 16S rRNA.
[in Korean]
For Authors
Publisher
Sponsors
