Wonkeun Song, Han-Sung Kim, Jae-Seok Kim, Hyun Soo Kim, Dong Hoon Shin, Saeam Shin, Min-Jeong Park
Ann Clin Microbiol 2016 December, 19(4): 83-87. Published on 20 December 2016.
Background: We evaluated the carbapenem inactivation method (CIM) compared with the modified Hodge test (MHT) for the detection of carbapenemase-producing Gram-negative bacilli.
Methods: A total of 61 isolates of carbapenemase-producing Enterobacteriaceae (CPE: 14 KPC, 7 GES- 5, 8 NDM-1, 9 VIM-2, 9 IMP-1, and 14 OXA-48-like), 34 isolates of metallo-β-lactamase (MBL)-producing Pseudomonas spp. (14 VIM-2 and 20 IMP-6), and 70 carbapenem-nonsusceptible carbapenemase-negative isolates were included. The CIM and MHT were performed for all of the isolates. To perform the CIM, a meropenem disk was incubated with a suspension of the isolate to be tested and then on Mueller-Hinton agar with the Escherichia coli ATCC 29522 strains. The absence of an inhibition zone indicates presence of a carbapenemase. The presence of a clearing zone indicates lack of a carbapenemase.
Results: The total sensitivity and specificity of CIM (96% sensitivity and 100% specificity) in carbapenem- nonsusceptible Enterobacteriaceae and Pseudomonas spp. were better than those of the MHT (77% sensitivity and 94% specificity). The interpretation of CIM results was easy, with no or ＜20 mm inhibition zones indicating positivity and ＞20 mm inhibition zones indicating negative carbapenemase activity.
Conclusion: The CIM had excellent sensitivity and specificity for detection of CPE and MBL-producing Pseudomonas spp., and a positive result was easily determined, unlike the MHT.
Jung Wook Kim, Gi Su Kang, Jae Il Yoo, Hwa Su Kim, Yeong Seon Lee, Jae-Yon Yu, Kwang-Jun Lee, Chan Park, Il-Hwan Kim
Ann Clin Microbiol 2016 December, 19(4): 88-96. Published on 20 December 2016.
Background: To investigate the national molecular epidemiology and resistance profiles of vancomycin- intermediate Staphylococcus aureus (VISA), we analyzed the characteristics of methicillin-resistant Staphylococcus aureus (MRSA) collected from clinical samples at tertiary or general hospitals participating in a nationwide surveillance program for VISA and vancomycin-resistant Staphylococcus aureus (VRSA) in Korea during an 12-week period in each year from 2007 to 2013.
Methods: VISA was defined by agar dilution, broth dilution and E-test methods with vancomycin minimum inhibitory concentrations of ＞2 μg/mL. All VISA isolates were characterized by multilocus sequence typing, staphylococcal cassette chromosome mec typing, spa typing, accessory gene regulator typing, Diversilab analysis, and antibiogram analysis.
Results: Of 109,345 MRSA isolates, 87,354 were screened and 426 isolates were identified as positive on brain heart infusion agar containing 4 μg/mL vancomycin (BHI-V4). Of 426 isolates, 76 isolates were identified as VISA. No VRSA isolates were detected among the isolates. Overall, a total of 6 genotypes were identified among VISA strains and the predominant clones were ST5-II-t2460, ST72-IV-t324, and ST239-III-t037 (44.7%, 15.8%, and 10.5%, respectively). Of note, ST72-IV-t324 clones are known to be a typical community-associated MRSA. ST239-III- t037 strains were more resistant to trimethoprim-sulfamethoxazole than any other type of strain. ST72- IV-t324 strains were susceptible to all of the antimicrobial agents tested except erythromycin and daptomycin. All of the VISA isolates were susceptible to linezolid and quinupristin-dalfopristin.
Conclusion: Although VRSA is still rare, continuous monitoring of VRSA occurrence is needed, as well as VISA prevalence, epidemic clonal shift, and antimicrobial resistance.
Young Ah Kim, Dokyun Kim, Dongeun Yong, Kyungwon Lee
Ann Clin Microbiol 2016 December, 19(4): 97-104. Published on 20 December 2016.
Background: The recovery of bacteria from blood can be affected by many factors. Standardization of blood culture methods is important for reliability. Herein, we aimed to investigate blood culture protocols in Korea.
Methods: We performed a multicenter survey with a questionnaire about blood culture practices, which was sent by email to directors and clinical physicians in charge of clinical microbiology laboratories in May 2014. Total data from 18 participating hospitals were analyzed to be used as current baseline data, which is necessary to optimize blood culture protocols.
Results: Many laboratories included recommended blood volume, which is a major factor for bacteria recovery rate. This varied across participating laboratories. For adults, blood sampling of 10 mL was recommended by 10 laboratories and 20 mL was recommended by 5 laboratories. For children who weighed 14-36 kg and less than 14 kg, blood sampling of 10 mL (n=8) and 5 mL (n=7) was recommended, respectively. For neonates, less than 1 mL was recommended by 12 laboratories.
Conclusion: Substantial variations in blood culture protocols were seen across participating clinical microbiology laboratories. Efforts to standardize this protocol should be undertaken.
[in Korean]
Won-Hee Choi, Jung-Hyun Byun, Sunjoo Kim
Ann Clin Microbiol 2016 December, 19(4): 105-109. Published on 20 December 2016.
Background: The spectrum of bacteria causing diarrhea is highly affected by geographic area, sanitation, travel, food consumption, and previous antibiotic use. A nationwide databank for stool cultures is undeveloped. The aim of our study was to investigate the current prevalence of gastroenteritis bacterial pathogens in Korea.
Methods: We requested microbiological data via questionnaire emails sent to 98 hospitals. The frequency of each pathogen was acquired from 32 institutes. Numbers of stool cultures performed ranged from 193 to 14,296 (mean 2,724, SD 3,261) in 2015.
Results: Among 86,744 requested stool specimens, 917 (1.06%, range 0-4.59%, 95% confidence interval 0.63-1.48%) were positive. Salmonella was most prevalent (59.0%), followed by Candida (12.4%), Campylobacter (4.8%), Staphylococcus aureus (4.0%), Vibrio (4.0%), and Pseudomonas aeruginosa (1.75). Yersinia (0.3%) and Shigella (0.2%) were rarely isolated.
Conclusion: As the positive rate of the stool cultures is very low (1.06%), more effort and concern should be provided to enhance the isolation of pathogens. Salmonella was the most prevalent pathogen and Campylobacter and Vibrio were relatively common pathogens causing bacterial gastroenteritis in Korea.
Won Seon Yu, Kyeong Min Lee, Kyu Jam Hwang
Ann Clin Microbiol 2016 December, 19(4): 110-120. Published on 20 December 2016.
Background: In this study, we compared various methods of taxonomic identification of Bacillus strains: biochemical methods, 16S rRNA gene sequencing, and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). We also developed a pathogen- isolate resource database, thus increasing the identification rate when using MALDI-TOF MS.
Methods: Thirty Bacillus strains were obtained from the NCCP (National Culture Collection for Pathogens) and were identified using the VITEK 2 system (bioMérieux, France), API kit (bioMérieux, France), 16S rRNA gene sequencing, and MALDI-TOF MS. The pathogenicity of Bacillus cereus was confirmed through the identification of virulent genes using a multiplex PCR, and both protein extraction for protein profiling in MALDI-TOF MS and repetitive-sequence fingerprinting were performed.
Results: The identification rates at the species level were 40%, 80%, and 76.3% for the VITEK 2 system (bioMérieux), 16S rRNA gene sequencing, and MALDI- TOF MS, respectively. When the major spectrum- profiling dendrogram was compared with the phylogenetic tree, which was constructed based on the 16S rRNA gene sequences and rep-PCR fingerprinting, the classifications were confirmed to be effective.
Conclusion: Identification of Bacillus strains using MALDI-TOF MS was more effective than that using the VITEK 2 system (bioMérieux), but was similar to that using 16S rRNA gene sequencing. Continual addition to a proteome-based database can result in increased identification rates for MALDI-TOF MS.
[in Korean]
For Authors
Publisher
Sponsors
