Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology


Weeks in Review


Weeks to Publication
Indexed in KCI, KoreaMed, Synapse, DOAJ
Open Access, Peer Reviewed
pISSN 2288-0585 eISSN 2288-6850

October, 2008. Vol. 11 No. 2.

Review article

Resistance Mechanism and Epidemiology of Vancomycin-resistant Enterococci

Wee Gyo Lee

Ann Clin Microbiol 2008 October, 11(2): 71-77. Published on 20 October 2008.

Since vancomycin-resistant enterococci (VRE) were first isolated in Europe, rates of VRE colonization and infection have risen steadily. Today VRE have emerged as important nosocomial pathogens worldwide; hence, it is crucial to understand the underlying mechanism in the spreading of VRE. This article reviews the mechanism of resistance to vancomycin and global epidemiology of VRE, as well as the current molecular techniques that are being applied to the epidemiological studies of VRE.

[in Korean]

Original article

Distributions of Macrolide-Lincosamide-Streptogramin B Resistance Phenotypes in Clinical Isolates of Staphylococi

Young Uh, Gyu Yul Hwang, Ih Ho Jang, Ohgun Kwon, Kap Jun Yoon, Hyo Youl Kim

Ann Clin Microbiol 2008 October, 11(2): 78-83. Published on 20 October 2008.

Background: Increased resistance rates to macrolide-lincosamide-streptogramin B (MLSB) antibiotics among clinical isolates of staphylococci are considered as a consequence of an expanded use of these antibiotics in the treatment of Gram-positive infections. The proportion of MLSB resistance phenotypes of staphylococci is quite different by geographical variations and study periods. The aim of the present study was to determine the distribution of MLSB resistance phenotypes among clinical isolates of staphylococci in a university hospital.

Methods: The MLSB resistance phenotypes of clinical isolates of staphylococci were investigated by the double-disk diffusion test using erythromycin and clindamycin disks.

Results: Of 7,916 isolates, 55.7% exhibited a constitutive resistance phenotype (cMLSB) whereas 8.1% expressed an inducible resistance phenotype (iMLSB). Among 3,419 coagulase-negative staphylococci (CNS), 32.6% and 10.0% exhibited cMLSB and iMLSB resistance phenotypes, respectively. Of 4,497 Staphylococcus aureus isolates, 73.1% and 6.8% were cMLSB and iMLSB resistance phenotypes, respectively. cMLSB was detected among 90.2% of methicillin-resistant S. aureus (MRSA), 46.5% of methicillin-resistant CNS (MRCNS), 3.2% of methicillin-susceptible CNS (MSCNS), and 2.2% of methicillin-susceptible S. aureus (MSSA). iMLSB was detected among 16.5% of MSSA, 11.5% of MRCNS, 6.7% of MSCNS, and 4.4% of MRSA.

Conclusion: MLSBresistance was more prevalent among S. aureus isolates than CNS strains. Although cMLSB was the most frequently detected resistance phenotype among the total staphylococcal isolates, methicillin-susceptible strains exhibited somewhat higher iMLSB resistance rates compared with methicillin-resistant strains.

[in Korean]

Original article

Multicenter Study for the Frequency of 23S rRNA Point Mutations Associated with Clarithromycin Resistance in Helicobacter pylori in Korea

Hae Kyung Lee, Hiun Suk Chae, Jung Oak Kang, Mi-Kyung Lee, Heungsup Sung, Mi-Na Kim, Jongwook Lee, Miae Lee, Ki-Nam Shim

Ann Clin Microbiol 2008 October, 11(2): 84-89. Published on 20 October 2008.

Background: Clarithromycin resistance in Helicobacter pylori is a major cause of eradication therapy failure. The objective of this study was to determine the frequency and type of mutations in the 23S rRNA gene in Korea, which are associated with clarithromycin resistance. 

Methods: From January 2008 to March 2008, 353 gastric biopsy specimens were collected from five university hospitals in Seoul and Kyunggido. H. pylori infection was defined as showing a positive result in at least one of the following three tests: a microaerophilic culture, a CLO test, and a Giemsa/silver stain. The frequencies of A2143G, A2142G, and the wild type of 23S rRNA and the presence of H. pylori were determined by Seeplex ClaR-H. pylori PCR (Seegene Inc., Seoul, Korea). Twenty-nine culture isolates were tested for susceptibility to clarithromycin by E-test (AB Biodisk, Solna, Sweden) or the CLSI (Clinical and Laboratory Standards Institute) disk diffusion test. 

Results: From 176 H. pylori PCR-positive specimens, 23S rRNA gene mutations were detected in 38 isolates (21.6%), including 27 isolates of A2143G and 11 isolates of A2142G. Total mutation rates varied from 15.8% to 31.3% with the frequency of A2143G mutation alone varying from 8.5% to 25.0% among the five hospitals studied. There were 10 clarithromycin-resistant isolates found by susceptibility test and they were all positive for A2143G mutation. But, 3 of the 19 susceptible isolates were also positive for either A2143G or A2142G mutation. 

Conclusion: In Korea, the overall frequency of clarithromycin-resistant H. pylori was 21.6%; however, the type and frequency of the 23S rRNA mutations varied from hospital to hospital. 

[in Korean]

Original article

Detection of CTX-M-Type Extended-Spectrum β-Lactamase in Clinical Isolates of Chromosomal AmpC β-Lactamase-Producing Enterobacteriaceae from Korea and Their Molecular Characteristics

Chang-Ki Kim, Jong Hwa Yum, Dongeun Yong, Seok Hoon Jeong, Kyungwon Lee, Yunsop Chong

Ann Clin Microbiol 2008 October, 11(2): 90-97. Published on 20 October 2008.

Background: Clinical isolates of AmpC β-lactamase- producing Enterobacteriaceae were evaluated to determine the prevalence of CTX-M extended-spectrum β-lactamases (ESBLs) and their genetic environments.

Methods: A total of 250 non-duplicate isolates of Eneterobacter aerogenes, E. cloacaeCitrobacter freundiiSerratia marcescens and Morganella morganii were collected at a Korean hospital. ESBL production was determined by double disk synergy test. For ESBL producers, bla genes were sequenced and blaCTX-Menvironment was characterized by PCR mapping and sequencing.

Results: Among the 250 isolates 29 (11.6%) produced ESBL, and 14 of the 29 isolates produced CTX-M ESBLs, including CTX-M-9 by 8 isolates, CTX-M-3 by 4 isolates, CTX-M-12 by 1 isolate, and CTX-M-14 by 1 isolate. ISEcp1 was present upstream of blaCTX-M-3, 12, and 14. Three of the four CTX- M-3 producers had the same genetic environment (pemK-ISEcp1-blaCTX-M-3-orf477-mucA). An IS903-like element was found downstream of blaCTX-M-14. ISCR1 was identified upstream of blaCTX-M-9 and ISCR1 and blaCTX-M-9 were located on sul1-type class 1 integron. The variable region between the 5’-CS and the first 3’-CS contained dfrA16 and aadA2. Its structure was similar to that of In60, but our isolates did not have IS3000 or second 3’-CS.

Conclusion: CXT-M type ESBL was prevalent in AmpC β-lactamase-producing Enterobacteriaceae, particularly E. cloacaeblaCTX-Mgenes were associated with ISEcp1 or ISCR1. This is the first report on the genetic environment of blaCTX-M in Korean isolates.

[in Korean]

Original article

Characteristics of Acquired β-lactamase Gene in Clinical Isolates of Multidrug-resistant Pseudomonas aeruginosa

Sun Yang Chung, Ji Youn Sung, Kye Chul Kwon, Jong Woo Park, Chi Seon Ko, So Youn Shin, Jeong Hoon Song, Sun Hoe Koo

Ann Clin Microbiol 2008 October, 11(2): 98-106. Published on 20 October 2008.

Background: Recently, there have been reports of infections with multidrug-resistant Pseudomonas aeruginosa. To determine the mechanism of the resistance, we investigated the prevalence of Ambler class A and D β-lactamases, their extended-spectrum derivatives, and class B and D carbapenemase in multidrug-resistant P. aeruginosa isolates.

Methods: During the period of March 2006 to May 2007, clinical isolates of multidrug-resistant P. aeruginosa were collected from patients in Chungnam National University Hospital, Daejeon, Korea. Inhibitor-potentiated disk diffusion tests were used for the screening of metallo-β-lactamase (MBL) production. PCR and DNA sequencing were conducted for the detection of β-lactamase genes. We also employed the enterobacterial repetitive intergenic consensus (ERIC)- PCR method for an epidemiologic study.

Results: A total of 37 consecutive, non-duplicate, multidrug-resistant P. aeruginosa were isolated. Twenty- nine of 37 isolates harbored blaOXA-10 (56.8%), blaOXA-2 (18.9%), and blaOXA-1 (5.4%). Only one isolate produced IMP-1, and it also harbored blaOXA-1. None harbored Ambler class A β-lactamase or class D carbapenemase. The strains producing OXA type β-lactamases showed a significantly higher resistance to aminoglycoside compared to non-producers. The ERIC-PCR pattern of the 19 OXA-10 producing strains indicated that the isolates were closely related in terms of clonality.

Conclusion: OXA type β-lactamases are the most prevalent among the acquired β-lactamases produced by multidrug-resistant P. aeruginosa isolated at a university hospital in Chungcheong Province. Besides β-lactam antibiotics, the strains harboring OXA type β-lactamase showed a significantly higher resistance to aminoglycoside and qunolone.

[in Korean]

Original article

Evaluation of the VIDAS CDAB Kits for the Detection of the Clostridium difficile Toxins A and B

Jung Oak Kang, Bo-Moon Shin, Dongsoo Han, Tae Yeal Choi

Ann Clin Microbiol 2008 October, 11(2): 107-111. Published on 20 October 2008.

Background: Since the emergence of variant Clostridium difficile strains that fail to produce detectable toxin A, diagnostic kits targeted to detect toxin A only showed a considerable rate of false negative results. The aim of this study was to evaluate a toxins A and B (toxins A/B) detection kit recently marketed in Korea, and to compare toxin positive rates before and after introduction of the new kit.

Methods: The results of 5,783 toxin A assays performed during the 7-year period from 2001 through 2007 were analyzed and compared them to the toxins A/B assay data of 519 samples obtained from January to June 2008 in a university hospital. An enzyme-linked fluorescent immunoassay for toxins A/B (VIDAS C. difficile Toxin A & B, bioMerieux SA, France: VIDAS CDAB) and PCR for toxin genes A/B were performed directly in 102 stool samples from hospitalized patients.

Results: The positive rates of toxin A assays tended downward annually from 2001 to 2007 (16.3%, 17.8%, 13.9%, 11.4%, 13.8%, 8.2%, and 5.8%, respectively), but increased to 12.1% in 2008 after changing to the toxin A/B detection kit. The concordant rate of the VIDAS CDAB kit with the PCR method was 82.4%. Compared to the PCR method, the sensitivity and specificity of the toxin A/B kit were 60.7% and 90.5% respectively.

Conclusion: Testing kits for C. difficile toxin A only could result in a misdiagnosis more frequently than the testing kit for toxins A/B. The sensitivity of the newly launched toxin A/B detection kit from bioMerieux SA needs to be improved, but it showed a good specificity.

[in Korean]

Original article

Evaluation of Rapid Assay (Tox A/B Quik Chek) for the Detection of Clostridium difficile Toxins A and B

Sue Jung Kim, Heejung Kim, Myung Sook Kim, Eunmi Koh, Chang-Ki Kim, Seok Hoon Jeong, Yunsop Chong, Kyungwon Lee

Ann Clin Microbiol 2008 October, 11(2): 112-116. Published on 20 October 2008.

Background: Toxin immunoassay is widely used for rapid diagnosis of Clostridium difficile-associated diarrhea. The aim of this study was to evaluate the performance of Tox A/B Quik Chek test (TECHLAB, Blacksburg, VA, USA) compared to toxigenic culture.

Methods: From September 2006 to August 2007, 959 stools were examined by Tox A/B Quik Chek test and toxigenic culture (C. difficile culture plus tcdB PCR using colonies obtained from culture).

Results: Compared to the results of toxigenic culture, the sensitivity and specificity of Tox A/B Quik Chek test were 47.5% and 97.5%, respectively.

Conclusion: The sensitivity of Tox A/B Quik Chek test was not high, but the specificity was high. Although Tox A/B Quik Chek test alone is not sufficient to diagnose Clostridium difficile-associated diarrhea, it may aid rapid diagnosis, early treatment and prevention of nosocomial spread of the infection, if supplemented by C. difficile culture or tissue culture cytotoxin assay.

[in Korean]

Original article

Biocidal Effect of a Sanitizer/Disinfectant, Foodsafe, against Bacteria, Yeast, and Mycobacteria

Tae Youn Choi

Ann Clin Microbiol 2008 October, 11(2): 117-122. Published on 20 October 2008.

Background: Sanitizers and disinfectants are essential for hygienic control to prevent food poisoning. We evaluated the biocidal activity of a chlorine-based sanitizer/disinfectant, Foodsafe (Neochemical, Paju, Korea), against bacteria, yeasts, and mycobacteria. 

Methods: Clinical isolates and reference ATCC strains were exposed to the sanitizer/disinfectant solution (HOCl 100 ppm) prepared with Safefood tablets for various periods (0.5, 1, 2, 5, 10, 30, and 60 min). After the exposure the mixture of microorganisms and Safefood solution was inoculated into tryptic soy broth and onto tryptic soy agar or Sabouraud dextrose agar and cultured at 35oC. 

Results: All strains of bacteria, yeasts, mycobacteria, and vegetative form of Bacillus subtilis were killed within 2 min of an exposure to Foodsafe (100 ppm of HOCl) under both clean and dirty conditions. But, the spore form of B. subtilis was not killed even after 60 min. 

Conclusion: It may be recommended that Foodsafe can be used as an effective sanitizer/disinfectant for food hygienic control and an intermediate-level disinfectant for hospital infection control.

[in Korean]

Original article

Epidemiological Investigation of an Outbreak of Escherichia coli Infections in Neonatal Intensive Care Unit of a University Hospital

Hye Ryong Oh, Dae Soo Moon, Sook Jin Jang, Xue Min Li, Dong Min Kim, Sang Gi Park, Geon Park, Young Jin Park

Ann Clin Microbiol 2008 October, 11(2): 123-128. Published on 20 October 2008.

Background: In July 2007, three neonates in the neonatal intensive care unit (NICU) of Chosun University Hospital expired due to Escherichia coli sepsis. An E. coli outbreak was suspected. 

Methods: To investigate the outbreak, environmental cultures were taken from NICU. We performed repetitive extragenic palindromic (rep)-PCR to compare genotypes of the three isolates from the cases and one environmental strain of E. coli. A case-control study was done in order to identify risk factors for the infection. 

Results: In July 2007, the attack rate of E. coli was 11.1%, which was higher than the basal rate. All the three E. coli isolates from the cases presented the same antimicrobial susceptibility pattern whereas other E. coli isolated from non-outbreak period presented different patterns. Among environmental cultures, only one specimen collected from the surface of a bathtub for neonates was culture positive for E. coli. Three strains of the cases and one environmental strain of E. coli showed the same rep-PCR pattern, while control strains showed different patterns. No statistically significant difference in risk factors was found between the case and control groups in the case-control study. 

Conclusion: The result of rep-PCR assay showed that the outbreak had originated from a single clone of E. coli. But we could not identify risk factors for the infection. The attack rate of E. coli in NICU returned to the basal level after implement of the infection control measures such as disinfection of NICU environment and equipments, thorough hand washing, and education of health care workers.

[in Korean]

Case report

A Fatal Case of Infective Endocarditis Caused by Community-Associated Methicillin-Resistant Staphylococcus aureus ST72 in Korea

Seong-Ho Choi, Jin-Won Chung

Ann Clin Microbiol 2008 October, 11(2): 129-131. Published on 20 October 2008.

The advent of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has been a worldwide threat to public health for the past decade. We report a fatal case of infective endocarditis caused by a non-USA300, Panton-Valentine leukocidin toxin-negative CA-MRSA clone. This is a serious case of CA-MRSA infection caused by a sequence type (ST) 72 clone, which is one of the common CA-MRSA clones circulating in Korea where serious CA-MRSA infections have been rare. 

Case report

A Case of Indophenol Oxidase-positive Stenotrophomonas maltophilia Isolated from Urine in a Patient with Acute Lymphoblastic Leukemia

Seungok Lee, Bin Cho, Su-Mi Choi, Kyoung Sil Park, Myungshin Kim

Ann Clin Microbiol 2008 October, 11(2): 132-135. Published on 20 October 2008.

Stenotrophomonas maltophilia is a motile, non-fermentative, gram-negative rod. It is one of the important nosocomial pathogens associated with substantial morbidity and mortality such as pneumonia and bacteremia in immunocompromised patients. It should be carefully examined in the course of identification because it is frequently isolated together with other non-fermentative, gram-negative rods from clinical specimens. We report an isolate of S. maltophilia showing an oxidase-positive reaction, which is very rare for the species.

[in Korean]

Case report

A Strain of Nocardia cyriacigeorgica Isolated from a Patient with Pulmonary Infection

Hye Ryong Oh, Young Sook Kim, Sook Jin Jang, Xue Min Li, Won Yong Kim, Geon Park, Dae Soo Moon, Young Jin Park

Ann Clin Microbiol 2008 October, 11(2): 136-140. Published on 20 October 2008.

Nocardia cyriacigeorgica is an aerobic gram-positive rod that has mostly been reported as an opportunistic pathogen. Since molecular methodologies were introduced to identify species, infections caused by N. cyriacigeorgica have been reported. The patient was a 51-year-old woman with aplastic anemia, systemic lupus erythematosus, and disseminated tuberculosis, who was admitted to Chosun University Hospital with a history of fever and productive cough. During her hospitalization, sputum cultures were taken and a bacterium suspicious of acitinomycetes grew five times. It was a gram-positive rod that was also partially acid-fast on modified Kinyoun stain and resistant to lysozyme. After 24 h of incubation, cultures of the sputum onto sheep’s blood agar plates (BAP) demonstrated rough, chalky, and white colonies with a characteristic earthy odor. Based on the above results, the presumptive identification of Nocardia species was made. To identify species of this isolate, 16S rRNA gene sequence analysis was taken and showed 99.9% homology to N. cyriacigeorgica DSM44484T. The results of biochemical tests were compatible with other reports of N. cyriacigeorgica. As a result, this isolate was identified as N. cyriacigeorgica. Herein, we present a first report of N. cyriacigeorgica isolated from a patient with pulmonary infection in Korea. 

[in Korean]