Eui-Chong Kim, Eun-Ha Koh, Sunjoo Kim, Jung-Oak Kang, Jae-Seok Kim, Jeong Hwan Shin, Nam Yong Lee, Joseph Jeong, Ji-Hyun Cho, Chulhun L. Chang, Young Ree Kim
Ann Clin Microbiol 2011 September, 14(3): 85-90. Published on 20 September 2011.
Background: Group A Streptococcus (GAS) is responsible for a wide spectrum of human diseases. We investigated the distribution of emm types and antibiotic resistance rates of GAS from clinical specimens in several Korean medical centers.
Methods: A total of 192 strains of GAS from throat, blood, and other specimens collected in Seoul, Busan, Ulsan, Iksan, and Jeju were studied in 2008- 2009. The emm genotypes were identified using PCR and sequencing. Antimicrobial susceptibility testing was performed by disk diffusion method. Phenotypes of macrolide resistance were evaluated, and macrolide resistance genes were determined by PCR.
Results: The emm89 (33.9%) was most frequently detected, followed by emm1 (12.5%), emm12 (8.3%), emm4 (7.8%), and emm75 (7.3%). The distribution of emm types did not show a close relation to the type of specimen and was different for each area. The resistance rates to erythromycin (ERY) and clindamycin (CLI) were 4.6% and 3.7%, respectively. Among the nine ERY-resistant strains, the rate of constitutive resistance was 88.9%, compared with 11.1% for the M phenotype. Five of the ERY-resistant strains were emm28.
Conclusion: This multicenter study reveals heterogenous emm genotypes by geographic area. Rates of resistance to ERY and CLI were low, and most of the ERY-resistant strains showed a constitutive macrolide-lincosamide-streptogramin B (cMLSB) phenotype.
Jeong Hwan Shin, Sae Am Song, Mi-na Kim, Sunjoo Kim
Ann Clin Microbiol 2011 September, 14(3): 91-96. Published on 20 September 2011.
Background: Although many laboratories use automated blood culture systems, adequate skin disinfection and optimal blood volume are still critical for successful culture. The authors undertook a nationwide survey to understand the current situation and problems of blood culture in Korea.
Methods: A survey of blood culture was performed in March and April 2010, including disinfectants, blood collection intervals, and recommended blood volumes. The laboratory physicians described the storage condition of culture bottles before delivery to the equipment. For quality control, the positive rate and skin contamination rate were studied.
Results: Replies to the survey were collected from 74 Korean hospitals. Povidone iodine after either isopropyl alcohol or ethanol application was the most common means of skin disinfection. Sampling of a second set of cultures was performed simultaneously in 38% of hospitals and after a 30-min interval in 50%. The recommended blood volume was 10 mL in most cases (69%), but was 20 mL in 24% of cases. The bottles were stored at 37oC before installation in 23% of cases and at room temperature in 16%, whereas 57% were placed directly in the equipment during the night shift. Positive rates ranged 8-10% in 32% of hospitals, 5-8% in 23%, and ＜5% in 12%. Skin contamination rates were 2-3% in 32% of hospitals, 1-2% in 27%, and ＞3% in 13%.
Conclusion: Skin disinfection methods were rather variable. Sampling interval, blood volume, and storage of bottles should be standardized. More than 10% of the hospitals require quality improvement in terms of positive rate and skin contamination rates.
Hye Young Yun, Han-Sung Kim, Young Kyung Lee, Hee Jung Kang, Jae-Seok Kim, Wonkeun Song, Kyu Man Lee
Ann Clin Microbiol 2011 September, 14(3): 97-102. Published on 20 September 2011.
Background: The inhibition rates for nucleic acid tests of Mycobacterium tuberculosis have been reported to range from less than 1% to more than 10%. Specimen dilution, boiling, addition of bovine serum albumin (BSA), and a silica membrane can be used to override amplification inhibitors in nucleic acid tests of M. tuberculosis. The inhibition rate for real-time PCR of M. tuberculosis (COBAS TaqMan MTB test; Roche Diagnostics, Manheim, Germany) and effective strategies to override PCR inhibitors were investigated in this study.
Methods: The inhibition rate for COBAS TaqMan MTB test was investigated in 980 clinical specimens. The effectiveness of PCR inhibitor removal by repeated run, dilution, boiling, addition of BSA, and use of silica membrane were evaluated in the inhibited specimens.
Results: Inhibitory substances were present in 4.1% of specimens (40/980). Among 40 inhibited specimens, inhibitory substances were removed in 12 (30%), 30 (75%), 27 (67.5%), 25 (62.5%) and 12 (30%) specimens with repeated run, dilution, addition of RBS, boiling and use of silica membrane, respectively.
Conclusion: The overall inhibition rate for the COBAS TaqMan MTB test was 4.1%. Dilution, boiling and addition of BSA were shown to be more effective than repeated run and use of silica membrane for removal of PCR inhibitors. A combination of two methods might be useful and should be studied in the future.
[in Korean]
Hye-young Wang, Hyunwoo Jin, Hyeeun Bang, Yeon-Im Choi, Eun-mi Park, Won-jung Koh, Hyeyoung Lee
Ann Clin Microbiol 2011 September, 14(3): 103-109. Published on 20 September 2011.
Background: The differentiation of Mycobacterium tuberculosis (MTB) from nontuberculous mycobacteria (NTM) is of primary importance for infection control and choice of antimicrobial therapy. The diagnosis of diseases caused by NTM is difficult because NTM are prevalent in the environment and have fastidious properties. In this study, we evaluated the real-time PCR-based MTB/NTM detection kit for its usefulness in discrimination of MTB and NTM species.
Methods: A total of 155 sputum specimens whose AFB staining smear and culture were positive were used for this study. Among them, 59 and 96 samples had been identified as MTB and NTM, respectively. DNA obtained from sputum specimens was subjected to analysis with MolecuTech Real MTB-IDⓇ (M&D, Korea) real-time PCR-based MTB/NTM detection kit. Subsequently, the results of MolecuTech Real MTB- IDⓇ were compared with AFB staining smear and culture results.
Results: The positive rate of MolecuTech Real MTB- IDⓇ to detect MTB and NTM was 98.3% (58/59) and 97.9 (94/96), respectively, using sputum specimens.
Conclusion: For detection of MTB/NTM, the sensitivity and specificity of MolecuTech Real MTB-IDⓇ were comparable to those of conventional methods. Therefore, this study suggests the usefulness of real-time PCR-based MolecuTech Real MTB-IDⓇ for rapid detection of MTB/NTM from direct specimens.
[in Korean]
Hye-young Wang, Hyunwoo Jin, Hyeeun Bang, Yeon-Im Choi, Eun-mi Park, Won-jung Koh, Hyeyoung Lee
Ann Clin Microbiol 2011 September, 14(3): 110-114. Published on 20 September 2011.
Campylobacter jejuni is one of the important bacterial pathogens causing entero-invasive diarrhea; however, C. jejuni infection is rarely complicated by bacteremia or extra-intestinal localization. In the domestic literature, the majority of the relevant reports have focused on Campylobacter fetus, which causes bacteremia more frequently than enteritis, but there are no reports of C. jejuni bacteremia in Korea. We present the case of a 13-year-old girl who presented with abdominal pain. Blood cultures revealed curved Gram-negative bacilli and small, mucoid, gray colonies on blood agar plates at 37oC. Biochemical tests showed oxidase-positive colonies. To confirm the species, 16S rRNA sequence analysis was performed. The isolate exhibited 99.7% homology to C. jejuni subsp. jejuni. The patient was treated with third-generation cephalosporin and aminoglycoside and had negative blood cultures after three days of treatment. She fully recovered within four days with no complications.
Yong Hyun Kim, Eun-Mi Koh, Yong-Wha Lee, You Kyoung Lee, Hee Bong Shin, Kyungwon Lee
Ann Clin Microbiol 2011 September, 14(3): 115-117. Published on 20 September 2011.
Brevundimonas diminuta is a lactose non-fermenting Gram-negative rod associated with infection in immunocompromised patients. In three patients from two general wards, B. diminuta was isolated in blood culture sample. The clinical features of the patients did not coincide with the blood culture result, and pseudo-outbreak was suspected. These isolated were biochemically identified as Brevundimonas diminuta, and 16S rRNA sequencing confirmed their identification. The PFGE result showed a single pattern, and their clonality was assumed.
[in Korean]
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