Hae-Sun Chung, Yangsoon Lee, Eun Suk Park, Dong Suk Lee, Eun Jin Ha, Myungsook Kim, Dongeun Yong, Seok Hoon Jeong, Kyungwon Lee, Yunsop Chong
Ann Clin Microbiol 2014 June, 17(2): 29-34. Published on 20 June 2014.
Background: Acinetobacter spp. is an important nosocomial pathogen for which increasing resistance to multiple antimicrobial agents has been observed. Prevalence of multidrug-resistant (MDR) Acinetobacter spp. in the intensive care unit (ICU) at a teaching hospital in Korea started to increase in 2008. The aim of this study was to determine the source of pathogen spread and to characterize the emerging strains at an early stage of outbreak.
Methods: Samples from respiratory instruments and fomites in the ICUs, as well as from the healthcare workers, were cultured to identify the sources of MDR Acinetobacter spp. Antimicrobial susceptibility was determined by the CLSI disk diffusion method. Pulsed field gel electrophoresis (PFGE) was performed for clinical and environmental isolates in order to determine clonality. Carbapenemase genes were detected by multiplex PCR. Infection control measures including peer-monitoring of hand washing, environmental cleaning and standard precautions were enforced.
Results: Among the samples from the ICU tools (105) and healthcare worker’s hands (44), 31 (30%) and 2 (5%) respective samples yielded MDR Acinetobacter spp. Among the environmental samples, 90% were from respiratory-related equipment. The majority of clinical and environmental MDR Acinetobacter spp. (44/55) belonged to the pulsotype A. baumannii and carried both blaOXA-51-like and blaOXA-23-like genes. Even though infection-control measures were enforced, prevalence of MDR Acinetobacter spp. continues to increase.
Conclusion: An outbreak of MDR Acinetobacter spp. in a Korean hospital was caused by A. baumannii carrying the blaOXA-23-gene and was correlated with contaminated respiratory-related instruments in the ICUs. More intensive measures for nosocomial infection control are needed for successful prevention of Acinetobacter spread in hospitals.
Sae Am Song, Ji Hyun Kim, Jeong Hwan Shin, Si Hyun Kim, Nam Yong Lee, Mi-Na Kim, Sunjoo Kim
Ann Clin Microbiol 2014 June, 17(2): 35-41. Published on 20 June 2014.
Background: Blood culture for diagnosis of bacteremia and fungemia comprises aerobic and anaerobic cultures. The clinical utility of routine anaerobic blood culture has been questioned for a long time and was evaluated in this study.
Methods: A total of 9,028 positive blood cultures were collected from adults at four university-affiliated hospitals. We recorded the species distribution according to growth in aerobic or anaerobic culture.
Results: Among the 9,028 positive results, 3,239 cases (35.9%) occurred in aerobic culture, 1,543 cases (17.1%) in anaerobic culture and 4,246 cases (47.0%) in both cultures. The species grown only in the anaerobic cultures consisted of 81.4% facultative anaerobes, 2.0% strict anaerobes, 8.5% strict aerobes, and 8.1% yeasts.
Conclusion: Routine use of paired aerobic/anaerobic blood culture is essential because a considerable number of facultative anaerobes and yeasts grow only in anaerobic blood culture. Strict aerobes and fungi were more commonly isolated in the anaerobic bottles than were strict anaerobes.
[in Korean]
Ji-Young Jeong, Seon-Heui Lee, Sunyoung Jang
Ann Clin Microbiol 2014 June, 17(2): 42-49. Published on 20 June 2014.
Background: The purpose of this study was to evaluate the effectiveness of Xpert MTB/RIF (Cepheid, USA) in the detection of Mycobacterium tuberculosis and to determine rifampin resistance.
Methods: The literature review covered the period from 16 August 2011 to 1 October 2011, and eight domestic databases and foreign databases including Ovid-Medline, Embase, and Cochrane Library were used. Key words, such as ‘Rifampin, Polymerase Chain Reaction,’ ‘GeneXpert’ and ‘Xpert MTB-RIF’ were used to search a total of 1,385 documents. The SIGN (Scottish Intercollegiate Guidelines Network) tool was used to evaluate the quality of the 20 selected studies.
Results: Test accuracy for the detection of M. tuberculosis was assessed on the basis of 20 studies using the M. tuberculosis culture test as the reference standard. The acid-fast bacteria smearing test had a sensitivity in the range of 0.69-1.00, specificity in the range of 0.72-1.00 and test accuracy in the range of 0.75-1.00. Test accuracy regarding rifampin resistance was assessed on the basis of 17 studies. Using an anti-tuberculosis agent sensitivity test as the reference standard, the sensitivity, specificity and test accuracy of real-time, nested PCR were in the ranges of 0.75-1.00, 0.96-1.00 and 0.95-1.00, respectively.
Conclusion: Xpert MTB/RIF is a useful test for patients suspected of having rifampin-resistant tuberculosis.
[in Korean]
Oh-Geun Kweon, Jin Seok Kim, Gou-Ok Kim, Chang-Il Lee, Kwang-Hyeon Jeong, Junyoung Kim
Ann Clin Microbiol 2014 June, 17(2): 50-57. Published on 20 June 2014.
Background: Extended-spectrum cephalosporins and fluoroquinolones are important antimicrobials for treating invasive salmonellosis, and emerging resistance to these antimicrobials is of paramount concern.
Methods: A total of 30 Salmonella spp. clinical isolates recovered in Gyeongsangbuk-do from 2012 to 2013 were characterized using antibiotic resistance profiles and pulsed-field gel electrophoresis (PFGE).
Results: A high prevalence of multidrug-resistant isolates, mainly showing an ampicillin, nalidixic acid, chloramphenicol resistance pattern, was observed. Four extended-spectrum β-lactamase (ESBL)-producing isolates (3 CTX-M-15 isolates and 1 CTX-M-27 isolate) were found. The blaCTX-M-27 gene was carried by an IncF conjugative plasmid in the S. Infantis isolate. The blaCTX-M-15 gene were carried by an IncF (2 isolates) or IncHI2 (1 isolate) conjugative plasmid in S. Enteritidis. In addition, a single mutation of GyrA, Ser83Thr (1 isolates), Asp87Tyr (9 isolates), Asp87Gly (4 isolates), and Asp87Leu (3 isolates), was detected in nalidixic acid-resistant Salmonella spp. isolates. XbaI PFGE analysis of all isolates revealed more than 19 different pulsotypes. The most common S. Enteritidis PFGE pattern (SEGX01.003) was associated with a larger number of cases of invasive salmonellosis than all other patterns.
Conclusion: The information from our study can assist in source attribution, outbreak investigations, and tailoring of interventions to maximize disease prevention.
[in Korean]
Young Uh, In Ho Jang, Soon Deok Park, Kab Seung Kim, Dong Min Seo, Kap Jun Yoon, Hee Kyoung Choi, Young Keun Kim, Hyo Youl Kim
Ann Clin Microbiol 2014 June, 17(2): 58-64. Published on 20 June 2014.
Background: The false positive signals of a continuous monitoring blood culture system (CMBCS) increase the reporting time and laboratory cost. This study aimed to determine the highly relevant variables that discriminate false positive signals from true positive signals in a CMBCS.
Methods: Among 184,363 blood culture sets (aerobic and anaerobic), the signal-positive samples according to a BACTEC FX system (Plus Aerobic/F, BDA; Plus Anaerobic/F, BDN) and BacT/Alert 3D system (Standard Aerobic, BSA; Standard Anaerobic, BSN) between April 2010 and November 2013 were classified into two groups: false positive or true positive signals. The data of 15 parameters between the two groups were then statistically compared.
Results: Among total blood cultures, the positive rates of CMBCS signals according to BDA, BDN, BSA, and BSN were 4.9%, 2.8%, 3.8%, and 3.2%, respectively. The false positive rates of CMBCS signals according to BDA, BDN, BSA, and BSN were 0.6%, 0.1%, 0.1%, and 0.1%, respectively. The blood volume, detection time, time interval between admission and test, C-reactive protein concentration, leukocyte count, delta neutrophil index, and mean peroxidase index showed statistically significant differences between the two groups.
Conclusion: There were no variables with diagnostic sensitivity and specificity for discriminating the two groups. Therefore, analysis of bacterial growth curves produced by CMBCS is needed for early and effective detection of false positive signals.
[in Korean]
Sun Young Cho, You Sun Nam, Hyung-Seok Yang, Yun Soo Soh, Min Jin Kim, Hee Joo Lee
Ann Clin Microbiol 2014 June, 17(2): 65-68. Published on 20 June 2014.
The efflux pump system has been suggested as an important mechanism in the drug resistance of Mycobacterium tuberculosis (MTB). In this study, molecular analysis of five genes in the efflux pump system of MTB isolates from Korean patients was performed in order to identify appropriate molecular targets. In this study, 35 culture-positive specimens were included. PCR was performed for five efflux genes, mmpL7, efpA, mmr, p55 and tap-like gene. In the 35 clinical isolates, molecular analysis of five kinds of efflux pump genes was performed. Only one clinical isolate showed negative PCR results for all five efflux pump genes. All the rest 34 isolates presented concurrent positive results for the five efflux pump genes. In the near future, gene expression study with quantitative PCR should be performed using these genes.
Mi-Soon Han, Myungsook Kim, Yangsoon Lee, Dongeun Yong, Kyungwon Lee
Ann Clin Microbiol 2014 June, 17(2): 69-72. Published on 20 June 2014.
Campylobacter jejuni commonly causes bacterial enteritis but rarely causes extraintestinal infection including bacteremia. We isolated C. jejuni from the blood culture of a 20-year-old man presenting with fever and headache and also from the blood culture of a 23-year-old man suffering abdominal pain and diarrhea. This organism grew in anaerobic culture, showed curved Gram-negative bacilli by Gram stain, and was identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS).
[in Korean]
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