Ji-Hyun Cho
Ann Clin Microbiol 2002 March, 5(1): 1-5. Published on 20 March 2002.
병원 검사실에서의 감염성 질환의 진단은, 검체의 배양에 의한 감염원 검출과 형태학적, 생화학적 및 대사상 특징이나 혈청학적 반응상과 같은 표현형 검사(phenotype test) 에 대부분 의존한다. 전통적인 표현형 검사는 1) 배양 조건이 까다로와 기존 방법에 의하여 배양이 불가능한 감염원 2) 장시간 소요 3) 배양조건에 의한 표현형의 변화 4) 다양한 유전자 및 유전자 조합에 의해 동일 표현형이 발현할 수 있다는 단점이 지적되고있다.
[in Korean]
Jeong Man Kim, Seok Hoon Jeong, Sang Hee Lee, Ji Hye Kim, Bit Na Kim, and Jong Chul Kim
Ann Clin Microbiol 2002 March, 5(1): 6-14. Published on 20 March 2002.
Background: Among Gram-negative pathogens in Korea, the incidence of resistance to thirdgeneration cephalosporins is becoming an ever-increasing problem. This study was designed to determine the prevalence of third-generation cephalosporins-resistant Escherichia coli and Klebsiella pneumoniae isolates from patients in a tertiary care hospital in Busan, Korea, and to characterize the mechanism of resistance.
Methods: A total of 710 E. coli and 237 K. pneumoniae non-duplicate isolates were collected from patients in Kosin Medical Center in 1999. Antimicrobial susceptibilities were tested by the disk diffusion method. Extended-spectrum β-lactamase (ESBL) production was determined by the double disk synergy test. MICs were determined by the agar dilution method. Searches for blaTEM , blaSHV , and blaCMY genes in cefotaxime-resistant or intermediate isolates were performed by PCR amplification. PCR products were used to determine the sequence of resistance genes by the dideoxy-chain termination method.
Results: Seven percent of E. coli and 25% of K. pneumoniae isolates were resistant to cefotaxime. Among the isolates with decreased susceptibility to cefotaxime, 69% (18/26) of E. coli and 80% (20/25) of K. pneumoniae isolates showed positive results in double disk synergy test. Banding patterns of PCR amplification showed that the blaTEM , blaSHV , and blaCMY genes were harboured by 71% (20/28), 86% (24/28) and 14% (4/28) of isolates with decreased susceptibility to cefotaxime, respectively. Seventy-one percent (20/28) of the isolates contained more than two types of βlactamase genes. Nucleotide sequence analysis of PCR products revealed that blaSHV-12 and blaTEM-1b were the dominant types of β-lactamase gene. In addition, we also identified blaTEM-52 , blaSHV-5 , and a new ESBL gene named blaTEM-17b .
Conclusions: Third-generation cephalosporins-resistant E. coli and K. pneumoniae are wide spread in Kosin Medical Center, Busan, Korea. Most of the isolates with decreased susceptibility to cefotaxime had blaTEM and/or blaSHV , and some isolates harboured blaCMY genes that may confer resistance against cephamycins. The spread of these β-lactamase genes could compromise the future usefulness of third-generation cephalosporins for the treatment of infections caused by E. coli and K. pneumoniae.
[in Korean]
Kyutaeg Yi, Jung Oak Kang, Kyung Suk Kim, and Tae Yeal Choi
Ann Clin Microbiol 2002 March, 5(1): 15-20. Published on 20 March 2002.
Background: Extended-spectrum β-lactamase (ESBL) producing Enterobacteriaceae are a serious problem worldwide because of their resistance to all β-lactam antibiotics, except carbapenem or cephamycin. To prevent erroneous selection of antibiotics for ESBL producers, the role of clinical microbiology laboratory in accurate detection of this organism is important. Several ESBL detection methods has been proposed, and recently ESBL detection could become possible without additional test using automated microbiology system was developed for used in which detect ESBL by comparing obtained AST results with the pooled data about species-resistance mechanisms. This study was designed to evaluate the abilities of VITEK 2 system (bioMerieux, Marcy l’Etoile, France) and it’s computer program, Advanced Expert System (AES) to detect ESBL-producing Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae).
Methods: A total 54 isolates of ESBL-positive (12 strains of E. coli, 42 strains of K. pneumoniae) and 33 ESBL-negative gram-negative isolates (21 of E. coli, 12 of K. pneumoniae) from hopitalized patients of Hanyang university Kuri hospital were evaluated. ESBL detection was done first by screening and confirmatory disk diffusion method recommended by NCCLS. Next, double disk synergy (DDS) test was performed. And also antimicrobial susceptibility of each isolate was determined with the VITEK 2 system and the results were analyzed with the expert system, AES.
Results: All the 54 ESBL-positive isolates by the NCCLS confirmatory test, demonstrated ESBL positive by both DDS test and VITEK 2 AES. Also all the 33 ESBL-negatives by the NCCLS confirmatory test, demonstrated ESBL negative by ESBL-negative isolates were confirmed as ESBL negative both DDS test and VITEK 2 AES. The sensitivities of ceftazidime and cefotaxime disks used in disk diffusion confirmatory test recommended by NCCLS were 92.6%, 81.5% respectively. The specificities were 100% in both disks. VITEK 2 AES predicted ESBLs as “ESBL”phenotype of 85.2% and as “ESBL+impermeability”phenotype of 14.8% according to resistance mechanisms. The 6 strains of K. pneumoniae revealing “ESBL+impermeability”phenotype were all resistant to cefoxitin, but 2 strains of E. coli demonstrating “ESBL+impermeability”phenotype was susceptible to cefoxitin.
Conclusion: These results suggest that the VITEK 2 AES can identify ESBL accurately at least for K. pneumoniae and E. coli without additional confirmatory test. Also, AES can predict resistance mechanisms of ESBL, which is difficult to detect by routine AST results. Additional study is needed to reveal the molecular mechanism of the “ESBL+impermeability”phenotype.
[in Korean]
Won keun Song, Chang Hee Oh, Seung Joo Kim, Tae Jae Lee, Min-Jeong Park, Dong Hoon Shin, Sung Ha Kang, and Kyu Man Lee
Ann Clin Microbiol 2002 March, 5(1): 21-25. Published on 20 March 2002.
Background: Six babies infected with Staphylococcus aureus occurred in a neonatal intensive care unit (NICU) over a period of 2 months, which was successfully controlled with the aid of molecular typing of the isolates.
Methods: We examined the staphylococcal toxins, mecA and tst gene PCR, and repetitive-element PCR (rep-PCR) typing in S. aureus isolated from the clinical specimens of infected babies, nasal swabs of the patients and medical personnels in a NICU, and environmental equipments.
Results: Among all S. aureus isolates tested, they were toxic shock syndrome toxin 1 (TSST-1)producing methicillin-resistant S. aureus (MRSA) who have mecA and tst gene, and one identical repPCR pattern all, except 3 MRSA isolated from the nasal swabs of 2 non-infected patients and 1 medical personnel.
Conclusions: It was demonstrated that TSST-1 producing MRSA became epidemic in the NICU as a result of the spread of a single clone.
[in Korean]
Young Uh, Hyun Mi Cho, In Ho Jang, Kap Jun Yoon, and Dong Min Seo
Ann Clin Microbiol 2002 March, 5(1): 26-34. Published on 20 March 2002.
Background: The accurate and rapid identification (ID) of nonfermentative gram-negative bacilli (NFB) is essential for diagnostic and therapeutic purposes and for epidemiologic studies of hospital infections. Commercial identification systems of NFB are easy to use but too expensive. The aim of the study was to develop a simple system for the identification of NFB species which are frequently isolated from clinical specimens.
Methods: Eighteen biochemical tests used in NFB microplate ID system were pyocyanin in Tech media; pyoverdin in Flo media; glucose fermentation, acid formation from glucose, maltose, lactose, sucrose, and mannitol in oxidation-fermentation media; Nitrate and nitrite reduction in nitrate media; ornithine decarboxylase, lysine decarboxylase, and arginine dihydrolase in Moeller decarboxylase media; acetamide, urease, citrate, 42℃growth, and oxidase test. For the establishment of NFB’s biochemical data in microplate ID system, 175 consecutive isolates of NFB from clinical specimens isolated during the period of April 2000 were simultaneously tested by microplate method and API 32GN.
Results: Ninety-two percent of clinical isolates of NFB were identified to the species level by NFB microplate ID system.
Conclusions: The NFB microplate ID system is simple to use, rapid and economical. Further modification are needed to improve the accuracy and identification rate of NFB isolates.
[in Korean]
Jae-Kyoo Lee, Kwang-Yup Kim, Myoung-Sook Koo, Dong-Eun Yong, and Eui-Chong Kim
Ann Clin Microbiol 2002 March, 5(1): 35-41. Published on 20 March 2002.
Background: Campylobacter is the most common bacterial cause of food-borne infection in developed countries, and handling or eating of contaminated poultry products was reported as the major cause of human campylobacteriosis in sporadic cases. This study was performed to investigate the prevalence of Campylobacter in patients with diarrhea and raw chickens of grocery, and identify the species by multiplex PCR and determine the genotypes of isolates by SmaI pulsedfield gel electrophoresis(PFGE) profiles.
Methods: Eight hundred and fifty six stool specimens obtained from 773 hospitalized patients with diarrhea and 16 raw chickens purchased from grocery were tested. Karmali’s charcoal based selective medium and Campylobacter enrichment broth were used for isolation of Campylobacter from patients and chicken, respectively. And membrane filter method with sheep blood agar was also used in both two cases. Isolates were indentified with PCR, PCR-RFLP, and biochemical test. And genotypes were determined with SmaI PFGE profile analysis.
Results: A total of 13 Campylobacter strains(1.7%) were isolated from 856 stool specimens of 773 patients with diarrhea, nine isolates were C. jejuni and four were C. coli. All of 16 raw chickens were contaminated with Campylobacter spp., and both of C. jejuni and C. coli were detected from eight chickens. From the SmaI-digested PFGE profile analysis of nine C. jejuni strains and four C. coli strains isolated from patients, eight types and four types of PFGE profile were obtained, respectively. And 15 types and seven types of PFGE profile were obtained from 23 of C. jejuni and 11 of C. coli which strains were isolated from chicken samples, respectively. The several isolates showing the different PFGE patterns were detected in the same chicken. Three PFGE patterns of C. jejuni isolated from patients were observed in the chickens. One type of C. coli PFGE profiles of the patient’s isolates were the same as that of chicken.
Conclusions: The prevalence of Campylobacter infection is not high compared to the other countries, but most of raw chickens are contaminated with Campylobacter spp. Several genotypes of C. jejuni and C. coli are contaminated in the single chicken. The PFGE patterns of some human isolates are the same as those of chicken so that human infection may be originated from the chicken. But the reason of low infection rate in human in spite of the very high contamination rate of chicken should be clarified in the near future.
[in Korean]
Young Uh, Soon Duk Park, Hyun Mi Cho, Hyeun Gyeo Lee, An Suk Jeoung, Mi Kyung Lee, and Kap Jun Yoon
Ann Clin Microbiol 2002 March, 5(1): 42-46. Published on 20 March 2002.
Background: The test for hippurate hydrolysis is critical for differentiation of C. jejuni and other thermophilic Campylobacter species. So, we evaluated the disk method for detection of hippurate hydrolysis by C. jejuni.
Methods: Twenty-eight Campylobacter species isolated from stool culture were simultaneously tested with disk method for detection of hippurate hydrolysis and polymerase chain reaction (PCR) for hippuricase specific gene. Disk method was tested with difference in incubation time (2 hours vs. 4 hours), hippurate concentration (1%, 2%, and 4%), amount of ninhydrin (50 μL vs. 100 μL), and inoculation method (colony vs. suspension of organism adjusted by turbidity), finally, 24 types of disk methods were performed.
Results: By using hippuricase PCR method as the reference for the detection of hippurate hydrolysis, the disk method showed a sensitivity of 91.7% and a specificity of 100% when two kinds of disk methods were simultaneously performed.
Conclusions: The disk method for detection of hippurate hydrolysis is simple to use and require fewer cells than the tube method do, and should be useful as a routine diagnostic test in clinical laboratory for rapid identification of C. jejuni.
[in Korean]
Youn Mi Choi
Ann Clin Microbiol 2002 March, 5(1): 47-51. Published on 20 March 2002.
Background:Multidrug resistant tuberculosis (MDRTB) strains rely on the prompt availability of drug susceptibility test results. We evaluated the reliability and turnaround time of MGIT 960 system, automated version of the MGIT, for antimicrobial susceptibility test of Mycobacteria tuberculosis.
Methods:Ninety six isolates have been tested for susceptibility to isoniazid (INH), rifampin (RIF), ethambutol (EMB) and streptomycin (SM). Results were compared with those obtained by traditional solid media (absolute concentration method, indirect method).
Results:There was no statistically significant difference between the susceptibility testing results of the two methods except for EMB. Discrepant results were obtained for 8 isolates (8.3%) with INH, for 3 isolates (3.1%) with RIF, for 13 isolates (13.5%) with EMB, for 10 isolates (10.4%) with SM. Using the indirect method as the gold standard, the sensitivity of INH, RIF, EMB and SM susceptibility testing by the MGIT system were 94.1%, 98.8%, 86.7% and 90.0%, respectively. The specificity were 85.7%, for INH and RIF and 83.3%, for EMB and SM. Turnaround times were significant shorter in MGIT (average 12 days) than in solid media (average 57 days) (P < 0.05)
Conclusions:These data demonstrate that the MGIT system is accurate and rapid for INH, RIF and SM susceptibility test of M. tuberculosis, but EMB susceptibility testing requires further evaluation.
[in Korean]
Tai Yeal Choi, Myoung-Hee Ahn, Seo Eun Ha, Han Kyu Choi, and Jae-Sook Ryu
Ann Clin Microbiol 2002 March, 5(1): 52-58. Published on 20 March 2002.
Background: ELISA test is commonly used for diagnosis of parasite infection. This experiment was performed for detecting positive sera against Clonorchis sinensis, Paragonimus westermani, cysticercus, sparganum, Aisakis larvae, Toxoplasma gondii and Trichomonas vaginalis in patient’s sera with ELISA and Western blot analysis.
Methods: Two hundred sera were collected from clinical laboratory of Hanyang University Hospital(Seoul, Kuri). Antigens of parasites were prepared from rabbit (C. sinensis), dog (P. westermani), hog (cysticercus, from Yonsei University), patient (sparganum), mackerel (Anisakis larvae), mouse (T. gondii), cultivation in Trypticase-Yeast extract-Maltose medium (T. vaginalis). ELISA and Western blot was conducted with several parasite antigens and patient’s sera.
Results: Positive antibody titers of P. westermani, Anisakis, C. sinensis were observed 12.7%, 11.0%, and 7.0% of patient’s sera, respectively. Nineteen sera among 200 patients showed cross reactions with other parasites. On Western blot, there were several antigenic bands with patient’s sera, i.e., 3/5 sera of C. sinensis, 2/2 sera of P. westermani, 1/4 sera of sparganum, and 0/4 sera of cysticercus.
Coclusions: ELISA is a convenient method for detecting parasite infections. But purification of antigens is necessary and Western blot analysis may reduce the false positive reactions of infection.
[in Korean]
Seungok Lee, Jung-Joon Park, Eun-Jee Oh, Yeon-Joon Park, and Byung Kee Kim
Ann Clin Microbiol 2002 March, 5(1): 59-61. Published on 20 March 2002.
Streptococcus pneumoniae is the most common cause of community-acquired pneumonia in adults and an important agent in other infections, including meningitis, otitis media, and conjunctivitis, etc. The optochin susceptibility test is the most widely used method to discriminate S. pneumoniae from other streptococci. However, 0.8-1.5% of S. pneumoniae contain optochin resistant population. Recently, we experienced three cases of variants of S. pneumoniae with decreased susceptibility to optochin. Equivocal optochin disk test should be confirmed by bile solubility, agglutination test, or DNA probe test.
[in Korean]
Young Uh, Hyeun Gyeo Lee, Gyu Yel Hwang, Kap Jun Yoon, Soo Young Yoo, Baik Soon Koo, and Hyo Youl Kim
Ann Clin Microbiol 2002 March, 5(1): 62-67. Published on 20 March 2002.
Although Leuconostoc species with intrinsic high-level vancomycin resistance have rarely been isolated from clinical specimens, this organism may cause serious invasive infections such as bacteremia and meningitis in immunocompromised hosts or patients with a wide spectrum of underlying diseases including alcoholic liver diseases and gastrointestinal diseases. Predisposing factors of Leuconostoc bacteremia include intravenous or enteral feeding catheters, other invasive access devices such as tracheostomy, gastrostomy or endotracheal tubes, and previous antimicrobial treatment. This low prevalence may be due, in part, to the inability of automated systems to recognize this organism. It is important that all Leuconostoc isolates obtained from clinical specimens that are related to serious infections should be identified to species level for appropriate antibiotic therapy. We report two cases of Leuconostoc bacteremia occurring in a 65-year-old male with variceal bleeding, and in a 5 month child with ileostomy receiving total parenteral nutrition therapy.
[in Korean]
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