Il Kwon Bae, Seok Hoon Jeong, Kyungwon Lee
Ann Clin Microbiol 2012 March, 15(1): 1-8. Published on 20 March 2012.
Clinical isolates of Acinetobacter spp. in Korea exhibit higher antimicrobial resistance rates than in foreign countries and frequently show multi-drug resistance. Approximately 67% (272/405) of Acinetobacter baumannii isolates collected from 19 hospitals in Korea in 2008 exhibited intermediate susceptibility or resistance to imipenem and/or meropenem. The most important mechanisms in acquiring carbapenem resistance in A. baumannii in Korea are production of OXA-23 and overproduction of OXA-51, while that in non-baumannii Acinetobacter is the production of metallo-β-lactamases. All the carbapenem-resistant A. baumannii isolates were identified as clonal complex 92 and belonged to worldwide clone 2.
[in Korean]
Ki Ho Hong, Se-Ick Joo, Eui-Chong Kim, Sue Shin, Eun Youn Roh, Jong Hyun Yoon
Ann Clin Microbiol 2012 March, 15(1): 9-13. Published on 20 March 2012.
Background: Diagnosis of nontuberculous mycobacterium (NTM) is challenging, and clinical, radiological and microbiological criteria should be met. Traditionally, culture results on solid media have been reported semi-quantitatively, but no study exists regarding the clinical significance of low-colony count culture reports. The authors of the present study analyzed the clinical significance of low-colony count specimens of NTM with a greater than three-year follow-up period.
Methods: A total of 341 clinical isolates were evaluated among the isolates at Seoul National University Hospital and Seoul National University Borame Hospital from October 2005 to September 2006. Colony count less than 50 was considered a low-colony count specimen. Identifications of NTM from all the isolates were performed using a DNA chip (PCR reverse hybridization, LG Life Science, Korea). Clinical significance was analyzed by reviewing the medical records of patients with greater than three years of follow-up data after NTM isolation from respiratory samples.
Results: NTM lung disease was observed in 27.0% of the patients with low-colony count specimens among 167 patients with respiratory samples, and 70.4% of the patients were treated. The low-colony count patients had less NTM lung disease, longer incubation period, and less acid fast bacilli-positivity than patients with a colony count greater than 50.
Conclusion: The prevalence of NTM lung disease with a low-colony count specimen was greater than 25%. In a clinical setting, NTM lung disease should not be excluded only on the basis of a low-colony count.
[in Korean]
Hae-Sun Chung, Hyukmin Lee, Yangsoon Lee, Dongeun Yong, Seok Hoon Jeong, Bok-Kwon Lee, Suk-Chan Jung, Suk-Kyung Lim, Kyungwon Lee, Yunsop Chong
Ann Clin Microbiol 2012 March, 15(1): 14-20. Published on 20 March 2012.
Background: The emergence of non-typhoidal Salmonella (NTS) with decreased susceptibilities to fluoroquinolone, ampicillin, or ceftriaxone has been reported worldwide. However, current surveillance studies of resistance among NTS in Korea are limited. Thus, the antimicrobial susceptibilities; resistance mechanisms such as extended-spectrum β-lactamase (ESBL), plasmid-mediated AmpC β-lactamase (PABL), and plasmid-mediated quinolone resistance (PMQR); and molecular epidemiologic characteristics were investigated in the present study.
Methods: National Institute of Health and National Veterinary Research and Quarantine Service collected NTS strains from 219 clinical and 293 non-clinical specimens from 2006 to 2008. The antimicrobial susceptibilities were determined using the Clinical and Laboratory Standards Institute disk diffusion test. ESBL, PABL, and qnr genotyping were performed using PCR and nucleotide sequencing. Pulsed-field gel electrophoresis was used for the molecular epidemiologic study.
Results: The resistance to ampicillin in clinical and non-clinical NTS was 49% and 18 to 47%, respectively. The resistance rates to trimethoprim-sulfamethoxazole in clinical and non-clinical NTS were 8% and 0 to 41%, respectively. The rates to extended- spectrum cephalosporin were 0 to 1%. One CTX-M- 15-producing isolate and four CMY-2-producing isolates were detected. Notably, PFGE analysis showed four isolates carrying blaCMY-2, including one non-clinical strain had high clonality. Although the rate of ciprofloxacin resistance was very low, two qnrS1-carrying NTS strains were detected in non-clinical specimens.
Conclusion: The resistance rates to ampicillin in both clinical and non-clinical NTS were high, while those to trimethoprim-sulfamethoxazole varied depending on the specimen. NTS strains harboring CTX-M-15- type ESBL or CMY-2-type PABL were detected even though the resistance rates to cephalosporins were very low. Four NTS strains carrying the blaCMY-2- gene implied zoonotic infection. Continuous effort to minimize transfer of resistance genes in NTS is necessary.
[in Korean]
Hyekyung Kang, Sunjoo Kim
Ann Clin Microbiol 2012 March, 15(1): 21-26. Published on 20 March 2012.
Background: Previous antibiotic exposure may inhibit the growth of microorganisms in blood culture bottles. The authors investigated the frequency of previous antibiotic usage and analyzed the relationships among antibiotic usage, microbiological culture results and mortality of sepsis patients.
Methods: From April to May 2011, all blood cultures requested from inpatients were analyzed according to the admitted ward and antibiotic prescription records. The BacT/Alert 3D system (bioMerieux Inc.) was used with a standard bottle (SA, SN) for blood culture.
Results: Of 900 inpatients, 48% had been receiving antimicrobial agents when blood cultures were ordered. This group had a significantly higher mortality rate (36.2%) compared to the patients who had not received antibiotics (11.1%). Gram-negative rod bacteremia (37.1%) and candidemia (100%) resulted in a significantly higher mortality rate compared to Gram- positive cocci bacteremia (16.4%). In the analysis of 21 cases resulting in death, 15 (71.4%) patients died before or on the date when blood culture results were reported.
Conclusion: Patients who receive antibiotics prior to blood collection may be at a higher risk for mortality. In the present study, Gram-negative rod bacteremia and candidemia cases showed a rapid progression of sepsis as indicated by Gram staining and thus should be regarded seriously.
Seung Bok Hong, Bo Ra Son, Kyeong Seob Shin
Ann Clin Microbiol 2012 March, 15(1): 27-31. Published on 20 March 2012.
Background: This study compared three non-molecular methods for the detection of methicillin-resistance directly from blood cultures containing Staphylococcus aureus: penicillin-binding protein (PBP) 2a latex agglutination (LA), PBP2a immunochromatographic assay (ICA) and MRSA chromogenic medium (CM).
Methods: Fifty methicillin-resistant S. aureus (MRSA) and 50 methicillin-susceptible S. aureus (MSSA) were seeded into blood-culture bottles. When isolates returned a positive signal, 5 mL of culture was added to serum separator tubes and centrifuged at 1,300 g for 10 min. The pellets were then used as the inoculum for the PBP2a LA, MRSA-CM and PBP2a ICA. The pure colony was used for PBP2a LA test, additionally.
Results: The respective sensitivities and specificities were 98 and 100% for PBP2a ICA, and 100 and 100% for MRSA-CM in direct detection of MRSA from positive blood culture. The results of PBP2a LA test using pure colony were entirely compatible with those by mecA gene PCR but the PBP2a LA test using the pellets directly isolated from positive blood culture showed sometimes ambiguous agglutination; its sensitivity and specificity were 78 and 100%, if ambiguous results were scored as negative, and were 90 and 92%, if ambiguous results were scored as positive, respectively.
Conclusion: For direct detection of MRSA in positive blood culture, MRSA-CM and PBP2a ICA provided excellent results. The PBP2a LA test using pure colony also gave excellent results but the PBP2a LA test by the direct method using pellet of positive blood culture was slightly less sensitive than the other two methods.
[in Korean]
Kyutaeg Lee, Woo Jin Kim, Dong Lyul Kim, Jae Hyang Kim, Moo Sang Chong
Ann Clin Microbiol 2012 March, 15(1): 32-36. Published on 20 March 2012.
Background: Mycoplasma pneumoniae (MP) is a major cause of community-acquired pneumonia in children. Currently, no study exists regarding the frequency of the mycoplasmal antibody on Jeju Island. The aim of the present study was to investigate the frequency of mycoplasmal antibody among children living on Jeju Island.
Methods: From March 2009 to February 2011, the frequency of mycoplasmal antibody among 1580 pediatric (＜10 years old) patients who were tested for the mycoplasmal antibody titer in Cheju Halla Hospital were retrospectively investigated. The authors also analyzed the positive rates according to age, sex, and season.
Results: The frequency of mycoplasmal antibody titers were 69.4% for an antibody titer ＞1：40, 20.8% in an antibody titer ＞1：320, and 10.7% in an antibody titer ＞1：640. The positive rates of each antibody titer were lowest in children under the age of 6 months, and the positive rates increased gradually with age until 4 years, where the frequency showed a “plateau.” There were minor cyclic increases of positive rate (＞1：320, ＞1：640) every three months from August 2009 to June 2010, and there was a major increase of positive rate (＞1：320, ＞1：640) from July 2010 to January 2011. However, there was no positive rate cyclic pattern of mycoplasmal antibody in the lower titer (＞1：40) patients.
Conclusion: The frequency of mycoplasmal antibody titer is lowest under the age of 6 months. The positive rates rise gradually with age until the age of 4 years. The present study showed minor peaks of mycoplasmal antibody titer every three months and a major peak of mycoplasmal antibody titer. The results can be helpful for the interpretation and diagnosis of MP among pediatric patients on Jeju Island.
[in Korean]
Hyekyung Kang, Seong Chun Kim, Sunjoo Kim
Ann Clin Microbiol 2012 March, 15(1): 37-42. Published on 20 March 2012.
Background: Reducing skin contamination rate and improving the positive rate in blood culture is essential for the correct diagnosis and management of sepsis. Chlorhexidine-alcohol was compared with povidone-iodine for the efficiency of disinfection. Positive rates were compared between the collection of 10 mL and 20 mL of blood per sample.
Methods: The study population included adult patients ≥ 18 years old requested for blood culture in the Emergency Department. Povidone-iodine (10%) was used for antiseptic skin preparation from March to June 2011, and 0.5% chlorhexidine-alcohol from July to October 2011. The standard for blood collection was 10 mL in the first period and 20 mL in the second period. The dedicated phlebotomists had been educated on the optimal skin preparation and sample collection.
Results: After 10% povidone-iodine application, 31 of 2,755 samples (1.1%) were considered to be contaminated; whereas, a total of 60 of 3,064 samples (2.0%) were contaminated (P=0.011) after application of 0.5% chlorhexidine-alcohol. The positive rate of blood culture was 12.5% (345/2,755) in the first period versus 17.1% (524/3,064) in the second period (P＜0.001).
Conclusion: Both disinfectants appeared acceptable for skin preparation for blood culture collection, although chlorhexidine-alcohol had a higher contamination rate than povidone-iodine. The positive rate of blood culture was in accordance with the amount of sample collected. Continuous education and monitoring are needed for the proper collection and management of blood culture.
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