Jongyoun Yi, Eui-Chong Kim
Ann Clin Microbiol 2010 March, 13(1): 1-6. Published on 20 March 2010.
Methicillin-resistant Staphylococcus aureus (MRSA) is a typical pathogen of nosocomial infection, and has recently emerged as an important community-acquired pathogen. MRSA is notorious as a multidrug- resistant organism. Its resistance to all β-lactams is mediated by PBP2a which is encoded by mecA, and it is also resistant to many antimicrobials of other classes due to frequently co-carrying resistance genes, which accounts for becoming a clinical and laboratory issue. This article reviews the microbiological characteristics, surveillance methods, and molecular epidemiology of MRSA.
[in Korean]
Young Kyung Yoon, Hee Sun Sim, Jeong Yeon Kim, Dae Won Park, Jang Wook Sohn, Byung Chul Chun, Min Ja Kim
Ann Clin Microbiol 2010 March, 13(1): 7-13. Published on 20 March 2010.
Background: Recently hepatitis A virus (HAV) infection has propagated among adults in Korea due to the epidemiologic shift in the age-specific HAV seroprevalence. There are apparently increase in symptomatic patients with severe diseases. This study aimed to investigate clinical and molecular characteristics related to acute kidney injury (AKI) occurrence in HAV infection.
Methods: A case-control study was conducted in a university hospital between February 2009 and July 2009. Clinical findings of non-fulminant HAV infection complicated with AKI (N=5) were compared to those without AKI (N=60). The complete sequence of the VP1 region (900 bp) was amplified from stool specimens by the RT-PCR to determine HAV genotypes and genetic variations between the two groups.
Results: Among 65 patients with non-fulminant HAV infections, 5 patients (7.7%) developed AKI. In multivariate analyses, higher level of C-reactive protein was independently associated with AKI occurrence in non-fulminant HAV infections [odds ratios=1.094, 95% confidence interval=1.011−1.183]. HAV RNA was detected in 57 (86.4%) patients: 53 strains (93.0%) showed genotype IIIA and 4 strains presented genotype IA. All HAV isolates from the AKI patients belonged to the genotype IIIA and shared the identical sequences with those from the non-AKI patients.
Conclusion: This study indicates that higher level of C-reactive protein is associated with AKI occurrence in non-fulminant HAV infections. There were no specific nucleotide or amino acid substitutions in the VP1 region associated with AKI occurrence.
[in Korean]
In-Suk Kim, Eun-Ha Koh, Sunjoo Kim, Kook Young Maeng, Hyun Ju Jung
Ann Clin Microbiol 2010 March, 13(1): 14-18. Published on 20 March 2010.
Background: The Streptococcus pneumoniae urinary antigen test (SPUAT) (Binax Now, USA) was developed for detecting polysaccharide C in urine samples for rapid diagnosis of pneumococcal pneumonia, the most common cause of community-acquired pneumonia (CAP). To validate positive results of these tests, we retrospectively investigated all positive results obtained from the emergency room of a Korean university hospital among patients with suspected CAP.
Methods: One hundred twenty-three positive SPUAT results were abstracted and analyzed from the authors’ laboratory information system among the SPUAT results performed from 1,143 pneumonic patients admitted from the emergency room of a university hospital between 2007 and 2008. Medical records, including conventional microbiologic analysis results, were reviewed in detail for all positive test results.
Results: Among 123 patients with the positive SPUAT results, 24 patients were excluded due to hospitalization history during the preceding month. Nine of 99 patients (9.1%) with suspected CAP had confirmed pneumococcal pneumonia upon conventional sputum or blood culture. Thirty-five positive results (35.4%) showed other microorganisms upon conventional methods, which might be due to possible cross-reactivity. Among those, 23 positive results were considered bacterial pneumonic agents, and 12 positive results were regarded as urinary tract infection strains or contaminating agents. Fifty-five positive SPUAT results (55.6%) showed negative conventional microbiologic growth, and some positive SPUAT results might be caused by true pneumococcal infection although without cultural evidence.
Conclusion: Our retrospective study demonstrated that a positive SPUAT result typically does not agree well with conventional culture methods, suggesting that the value of a positive SPUAT result in etiology determination may be limited under practical conditions in a university hospital.
Hyukmin Lee, Eun-Mi Koh, Chang Ki Kim, Jong Hwa Yum, Kyungwon Lee, Yunsop Chong
Ann Clin Microbiol 2010 March, 13(1): 19-26. Published on 20 March 2010.
Background: Blood culture is essential for diagnosis of sepsis. However, usually the available blood volume is not sufficient to meet the guidelines. Thus, periodic monitoring and feedback are essential to iBackground: Recently a novel plasmid-mediated resistant mechanism that conferred high-level resistance to aminoglycoside via methylation of 16S rRNA was reported. The aims of this study were to determine the prevalence of the 16S rRNA methylase genes and to characterize the coresistance to other antibiotics in Gram-negative bacilli.
Methods: Consecutive non-duplicate Gram-negative bacilli were isolated from clinical specimens at a Korean secondary- and tertiary-care hospital from July 2006 to June 2007. The antimicrobial susceptibility was tested by the CLSI agar dilution method,and PCR was performed to detect the 16S rRNA methylase genes in the arbekacin-resistant isolates.
Results: In Gram-negative bacilli, the proportions of 16S rRNA methylase gene-positive isolates were 5% (75/1,471) in the secondary-carehospital and 4% (48/1,251) in the tertiary-care hospital, and the positive rates by species were 1% Escherichiae coli 16% (10/1,062), Klebsiella pneumoniae 16% (75/ 460), K. oxytoca 2% (1/44), Citrobacter spp. 9% (7/ 82), Enterobacter spp. 2% (4/181), Serratia marcescens 6% (6/100), Proteus miriabilis 4% (2/57), Achromobacter xylosoxidans 20% (1/5), Pseudomonas aeruginosa ＜1% (1/505), Acinetobacter spp. 10% (11/ 112), and Stenotrophomonas maltophilia 2% (1/66), respectively. Among 16S rRNA methylase-positive isolates from secondary- and tertiary-care hospitals,93% (70/75) and 90% (43/48), respectively, were armA positive, and others, except one rmtA positive isolate, were positive for the rmtB gene, according to PCR results. The rates of ESBL-positive and cefoxitin-resistant K. pneumoniae were 59% and 92%, respectively. In addition, 91% of 16S rRNA methylase-producing K. pneumoniae were positive for qnrB. There were no MBL producers among 16S rRNA methylase-producing Pseudomonas and Acinetobacter species.
Conclusion: The novel aminoglycoside-resistant mechanisms involving16S rRNA methylase were prevalent and widely distributed among Gram-negative bacilli in Korea, and other resistance mechanisms were commonly associated with 16S rRNA methylase- mediated resistance in Korea.
[in Korean]
Kyoung Ho Roh, Chang-Ki Kim, Jong Hwa Yum, Dongeun Yong, Seok Hoon Jeong, Chae Seung Lim, Chang Kyu Lee, Yunjung Cho, Kyungwon Lee, Yunsop Chong
Ann Clin Microbiol 2010 March, 13(1): 27-33. Published on 20 March 2010.
Background: Increasing numbers of Acinetobacter spp. resistant to multiple drugs, including carbapenem, has been a serious problem. The aims of this study were to determine carbapenem resistance patterns and mechanisms, as well as to study the molecular epidemiology of Acinetobacter spp.
Methods: Clinical isolates of Acinetobacter spp. were collected from May to November in 2006. Antimicrobial susceptibility testing was performed using CLSI disk diffusion and agar dilution methods. Metallo-β- lactamase- and OXA carbapenemase-producing isolates were detected by PCR. Carbapenem resistance and hydrolytic activities were compared according to OXA type and presence of ISAba1. Pulsed-field gel electrophoresis (PFGE) was performed to determine the epidemiologic features.
Results: The imipenem non-susceptible rates were variable from 10% to 67%. Among 151 isolates carrying blaOXA-51-like, 75 isolates carried both blaOXA-51-like and ISAba1, and 25 isolates had both blaOXA-51-like, blaOXA-23-like, and ISAba1. Carbapenem MICs of both blaOXA-51-like and ISAba1-carrying isolates were higher than those with blaOXA-51-like only. Carbapenem MICs of blaOXA-23-like-carrying isolates were higher than those with both blaOXA-51-like and ISAba1. Both blaOXA-51-like and ISAba1-carrying isolates and blaOXA-51-like, blaOXA-23-like, and ISAba1-carrying isolates demonstrated higher hydrolysis activities in oxacillin and carbapenems. Most of the tested isolates were susceptible to tigecycline, and all of them were susceptible to colistin. Pulsed-field gel electrophoresis suggested that there had been several outbreaks of bblaOXA-23-like and blaOXA-51-like-positive strains.
Conclusion: Carbapenem non-susceptible Acinetobacter isolates and OXA carbapenemase-producing isolates were prevalent. Dissemination of blaOXA-harboring isolates may make it difficult to treat infections due to carbapenem-resistant Acinetobacter spp. Further surveillance studies are required to prevent the spread of carbapenem resistance.
[in Korean]
Younhee Park, Hee Bong Shin, Chang Ki Kim, Kyoung Ho Roh, Jong Hwa Yum, Dongeun Yong, Seok Hoon Jeong, Kyungwon Lee
Ann Clin Microbiol 2010 March, 13(1): 34-39. Published on 20 March 2010.
Background: Accurate and rapid identification of pathogens is one of the most important tasks of the clinical microbiology laboratory, and, in cases of rare pathogens, the identification is difficult and time-consuming upon the use of conventional methods alone. Herein, we will report our molecular work involving the identification of bacteria and fungi.
Methods: Sixty bacterial isolates had been collected from November 2004 to May 2007, and 15 fungal isolates had been collected from September 2005 to May 2007. Species identifications were performed using sequence analyses of the 16S rRNA region of bacteria and the internal transcribed spacer (ITS) region of fungi. The data were compared with those of GenBank (http://www.ncbi.nlm.nih.gov/) or EMBL (http:// www.ebi.ac.uk/embl/).
Results: Sixty bacterial isolates included: 23 isolates with genus information (group 1), 17 isolates (group 2) that were too fastidious for genus or species identification, 16 isolates (group 3) with results from identification kits having low confidence, and 4 isolates (group 4) with odd antibiograms according to the species. In 58 of 60 isolates, identification of the genus or species could be obtained using molecular genetic methods. Thirty-eight isolates (63%) and 20 (33%) of 58 isolates could be identified at the species and genus levels, repectively. Among the total of 15 fungal isolates, 11 (73%) and 4 (27%) isolates were identified at the species and genus levels, respectively.
Conclusion: 16S rRNA and ITS sequencing analyses are very useful for identifying the species or genus of a pathogenic microorganism in the clinical microbiology laboratory.
[in Korean]
Chae Lim Jung, Mi Ae Lee, Wha Soon Chung
Ann Clin Microbiol 2010 March, 13(1): 40-46. Published on 20 March 2010.
Background: Community-acquired pneumonia (CAP) is a major infectious disease with significant morbidity and mortality worldwide. Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila, and Bordetella pertussis are common pathogens of CAP; however, the conventional methods used to detect these agents, including culturing, lack sensitivity and are time-consuming. We evaluated a recently developed multiplex PCR assay which can test these agents simultaneously.
Methods: One hundred patients with pneumonia and 99 healthy adults were tested using the Seeplex Pneumobacter ACE Detection assay (Seegene, Inc., Seoul, Korea). Culture and urinary antigen tests were also performed.
Results: In patients with pneumonia, the positive detection rates of PCR for S. pneumoniae and H. influenzae were 52.0% (52/100) and 30.0% (30/100), respectively, those of M. pneumoniae and L. pneumophila were 2.0% (2/100) and 1.0% (1/100), respectively, and B. pertussis and C. pneumoniae were not detected. In healthy adults, the detection rates of S. pneumoniae and H. influenzae revealed similar results, 53.5% (53/101) and 40.4% (40/101), respectively, and the other four pathogens were not detected. The sensitivity and specificity of PCR for S. pneumoniae in pneumonia patients were 100% (95% confidence interval [CI], 87.9∼100%) and 65.7% (95% CI, 55.2∼76.5%), respectively, according to the urinary antigen test and cultures of the respiratory samples and blood.
Conclusion: Differentiating S. pneumoniae and H. influenzae colonization from infection was difficult using the PCR assay. Therefore, the use of this assay is inappropriate for the diagnosis of pneumonia due to these agents, although multiplex PCR assay would be useful for the detection of M. pneumoniae and L. pneumophila.
[in Korean]
Mi Ae Jang, Min Jung Song, Jang Ho Lee, Nam Yong Lee
Ann Clin Microbiol 2010 March, 13(1): 47-50. Published on 20 March 2010.
Mycoplasma hominis is a commensal organism in the genitourinary tract. Extragenital infections by M. hominis are rare, and its occurrence is usually limited to immunocompromised patients. Here we report two patients with extragenital infection by M. hominis. The first patient, a woman with angioimmunoblastic T cell lymphoma, underwent autologous peripheral blood stem cell transplantation. The second patient, a woman with endometrial cancer, received laparoscopically-assisted vaginal hysterectomy. They both presented with septic symptoms, including fever, and M. hominis was isolated from pleural effusion and ascitic fluid, respectively. We are reporting these two cases of extragenital infection by M. hominis with a literature review to emphasize that the rapid isolation of M. hominis with early treatment can lead to a better prognosis.
[in Korean]
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