Jayoung Kim, Sung-il Cho, Yong-Kyun Kim, Yeon-Joon Park
Ann Clin Microbiol 2015 March, 18(1): 1-6. Published on 20 March 2015.
Background: Most clinical microbiology laboratories in Korea have difficulty in following the recommendations of the clinical procedure handbook for culture of body fluid and wound/abscess specimens. We evaluated the usefulness of MacConkey (MAC) and colistin-nalidixic acid blood agar (CNA) for the isolation of pathogens from these specimens.
Methods: A total of 1,508 clinical specimens [144 peritoneal fluid, 241 body fluids (19 bile, 70 joint fluid, 6 pericardial fluid, 104 pleural fluid, and other fluids in 42 cases) and 1,123 wound/abscess] were inoculated onto basic media [Blood agar plate (BAP), chocolate agar or BAP with streaking of Staphylococcus aureus] and simultaneously inoculated onto MAC and CNA. The pathogens isolated by basic media and by additional use of MAC and/or CNA were compared.
Results: With basic media, 885 isolates from 588 specimens were detected, and by additional use of MAC and CNA, an additional 27 isolates from 24 specimens and an additional 128 isolates from 112 specimens were isolated, respectively. Compared to the basic media, by adding MAC, an additional 233.3%, 38.5% and 4.5% of gram-negative bacteria were isolated from peritoneal fluids, body fluid and wound/abscess, respectively, and by adding CNA, an additional 106.7%, 45.0%, and 20.7% of gram-positive bacteria/yeast were isolated, respectively. The isolates detected by additional use of MAC were mainly Enterobacteriaceae (77.0%), and those detected by CNA were S. aureus (21.1%), Coagulase-negative Staphylococcus spp. (20.3%), Enterococcus spp. (16.4%), Streptococcus spp. (10.2%) and yeasts (16.4%).
Conclusion: For peritoneal fluid and body fluid specimens, additional use of MAC plus CNA seems necessary for detection of pathogens. For wound/abscess, additional use of CNA will be cost effective.
[in Korean]
Soo-Kyung Kim, Hyun-Ki Kim, Young Jin Ko, Heungsup Sung, Mi-Na Kim
Ann Clin Microbiol 2015 March, 18(1): 7-13. Published on 20 March 2015.
Background: The diagnosis of catheter-related bloodstream infection (CRBSI) should demonstrate catheter colonization of the same organism as the isolate from peripheral blood cultures, by catheter tip culture or by differential time to positivity (DTP) of catheter- drawn blood cultures versus peripheral blood cultures. The purpose of this study was to compare the sonication and the roll-plate methods of catheter tip culture.
Methods: One hundred and sixty-one catheter tips from 122 patients were submitted for catheter tip culture. Distal segments of the catheter were first inoculated using a roll-plate, and then inoculated by sonication. Sonication was performed using a BactoSonic device (Bandelin GmbH, Germany). A total of 1,018 sets of blood cultures from 7 days before to 1 day after catheter removal were analyzed for isolated organisms and DTP. Cutoffs of catheter colonization were ≥15 CFU for the roll-plate method, ≥100 CFU for sonication, and ≥2 h for DTP.
Results: Twenty-four catheter tips (14.9%) showed colonization with at least one of the two methods: 21 (13.0%) with the roll-plate method and 22 (13.7%) with sonication. The positivity rates for the two methods showed no significant difference, and the concordance rate for the two methods was 96.9% (k=0.866, P＜0.001). Blood culture was positive in 56 episodes in 44 patients, and 14 episodes of CRBSI were diagnosed in 12 patients: 10 by tip culture (two by sonication only) and 8 by DTP. Of the 122 specimens that were negative according to both methods, 4 were from the episodes of CRBSI diagnosed by DTP.
Conclusion: Roll-plate and sonication methods are comparable in diagnostic sensitivity for catheter colonization. The roll-plate and sonication catheter tip culture methods and DTP are complementary for diagnosis of CRBSI.
[in Korean]
Tae Sang Oh, You Sun Nam, Young Jin Kim, Hyung-seok Yang, Min-young Lee, Hyun Jung Gu, Hee Joo Lee
Ann Clin Microbiol 2015 March, 18(1): 14-19. Published on 20 March 2015.
Background: Blood culture remains the definitive method for diagnosing bacteremia and fungemia. In this study, we investigated the incidence of bacterial and fungal infections along with the trends in antimicrobial susceptibility in blood cultures collected from 2008 to 2013.
Methods: We performed a retrospective analysis of blood cultures performed at Kyung Hee University Hospital, Seoul, South Korea, between 2008 and 2013 to determine the bacterial and fungal species isolated, and their antimicrobial susceptibilities. Additional analyses were performed comparing these results to that of a prior study examining blood cultures collected from 2003-2007.
Results: Of the 102,257 specimens collected, 8,452 (8.3%) were culture positive, with Staphylococcus epidermidis being the most common species isolated (17.3%), followed by Escherichia coli (16.9%), Staphylococcus aureus (8.1%), and Klebsiella pneumoniae (6.5%). Fungal species accounted for 3.7% of all isolates. Methicillin resistance was seen in 54.3% of S. aureus isolates. The frequencies of extended-spectrum β-lactamase (ESBL)-producing E. coli and K. pneumoniae were 13.1% and 10.3%; imipenem resistance was seen in 19.5% of Pseudomonas aeruginosa isolates.
Conclusion: Although the number of blood specimens analyzed increased steadily over the course of this study, the rate of positive blood cultures declined. The most common microorganisms isolated were coagulase-negative staphylococci, E. coli, S. aureus, and K. pneumoniae, consistent with our prior analysis. This analysis of blood culture isolate frequencies and antibiotic susceptibilities can be used to inform antibiotic therapy decisions.
Gyun Cheol Park, Sook Jin Jang, Min Jung Lee, Joong-Ki Kook, Min Jung Kim, Young Sook Kim, Nam Woong Yang, Hye Soo Lee, Seong Ho Kang, Geon Park, Dae Soo Moon
Ann Clin Microbiol 2015 March, 18(1): 20-26. Published on 20 March 2015.
Background: Recently, genotypic identification of anaerobes is emerging as an alternative to the phenotypic method. In this study, we evaluated the performance of Vitek 2, API 20A and 16s rRNA gene sequencing for the identification of anaerobic bacteria.
Methods: A total of 35 anaerobe reference strains were identified using Vitek 2, API 20A and 16s rRNA gene sequencing. We evaluated the performance of three methods on the basis of the accurate identification rates.
Results: The Vitek 2, API 20A and 16s rRNA gene sequencing identified 54.3, 15.4, and 94.3% of test strains correctly at the species level and identified 77.1, 42.3, and 100% at the genus level, respectively. Results of the McNemar’s test showed that there was a significant difference between each of the three identification methods in species level identification (P value＜0.05).
Conclusion: 16s rRNA gene sequencing showed better performance than Vitek 2 or API 20A for anaerobic bacteria. Considering its excellent performance, 16s rRNA gene sequencing may be useful for accurate identification of anaerobic bacteria that cannot be correctly identified by phenotypic methods.
[in Korean]
Sholhui Park, Miae Lee, Hae-Sun Chung
Ann Clin Microbiol 2015 March, 18(1): 27-32. Published on 20 March 2015.
Background: For early diagnosis and treatment of influenza, rapid influenza diagnostic tests are commonly used. We evaluated the performance of the BD Veritor System for Rapid Detection of Flu A＋B (BD Veritor System; BD Diagnostics, USA) compared to multiplex real-time RT-PCR.
Methods: A total of 3,213 nasal and nasopharyngeal swab specimens in transport media from patients with influenza-like symptoms were tested with the BD Veritor System from December 2013 to April 2014. The sensitivity and specificity of 127 specimens were determined simultaneously using multiplex real-time RT- PCR with the AdvanSure RV real-time PCR (AdvanSure PCR; LG Life Sciences, Korea).
Results: Influenza viruses were detected in 41.3% (1,327/3,213) of all specimens tested using the BD Veritor System. Of the 127 specimens, 27 influenza A and 17 influenza B viruses were identified by the AvanSure PCR. The sensitivity and specificity of the BD Veritor System relative to the AdvanSure PCR was 85.2% and 99.0% for influenza A, and 58.8% and 99.1% for influenza B. Of the 190 specimens that tested negative using the BD Veritor System, the AdvanSure PCR detected influenza A and influenza B in 19 and 13 specimens, respectively. The mean threshold cycle (Ct) values of the antigen positive specimens were lower than those of the antigen negative specimens.
Conclusion: The BD Veritor System showed excellent specificity for both influenza types and good sensitivity for influenza A. However, the system was less sensitive for influenza B compared to multiplex real-time RT-PCR. For accurate diagnosis of false negative specimens, a molecular diagnostic test should be performed. The BD Veritor system could be a useful tool for screening and early diagnosis of influenza.
[in Korean]
Sung-Gyun Park, Kyoung-Bo Kim, Wonmok Lee, Jung-Sook Ha, Namhee Ryoo, Dong-Seok Jeon, Jae-Ryong Kim, Hyun-Ah Kim, Seong-Yeol Ryu
Ann Clin Microbiol 2015 March, 18(1): 33-36. Published on 20 March 2015.
A 73-year-old man visited our hospital because of pain with swelling and redness on the right foot dorsum. He was diagnosed with liver cirrhosis and nodular hepatic cellular carcinoma. Lower extremity CT scan and MRI showed abscess formation in the right foot dorsum. Gram-negative cocci were recovered from the culture of drained pus at the site and identified as Neisseria skkuensis by 16S rRNA gene sequencing. Here, we report the first case of cellulitis due to N. skkuensis and provide a literature review.
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