Trends of Viral Respiratory Pathogens Detected in Pediatric Patients, 1996 Through 2001 / 대한임상미생물학회지

BACKGROUND: Acute lower respiratory tract infections are common causes of hospitalization in children and viruses are major causative agents. The causative viruses are known to be variable by age, region, or year. We investigated the recent 5-year epidemics of respiratory viruses for pediatric patients in two university hospitals in Korea. MATERIALS AND METHODS: From July 1996 through June 2001, viral agents were detected for the 2,317 pediatric patients who were hospitalized with acute respiratory tract infection in Hanyang University Hospital and Hanyang University Guri Hospital. We obtained nasopharyngeal aspirates on the day of admission and detected the viruses by indirect immunofluorescent staining method (Respiratory panel I viral Screening & Identification Kit, Light Diagnostics, Chemicon, Temecula, CA, USA). RESULTS: The causative viral agents were detected in 737(31.76%) patients. They were respiratory syncytial virus of 53.6%, influenza A virus 38.6%, adenovirus 5.5%, influenza B virus 1.9%, and parainfluenzavirus 0.4%. The epidemics of RSV were found during winter, but the epidemics of influenza A were found more frequently in spring, which had tendency of following the epidemic of RSV. Adenovirus was detected sporadically throughout year. RSV was found more frequently in patient with bronchiolitis and pneumonia and also found more frequently in patient less than 6 month of age. Influenza A and adenovirus were in patients of pneumonia and in more frequently in patient one to two year of age. CONCLUSION: Viruses were the leading causative agents of acute lower respiratory tract infections in pediatric patients. RSV was the most important causative agent. Influenza A virus was the second frequent viral agent and detection rate was higher than other reports. The detection rate of parainfluenza virus was lower than other reports from Korea or from abroad.

Evaluation of the VITEK 2 Advanced Expert System to Detect Extended- Spectrum beta-Lactamase Production in Klebsiella Pneumoniae and Escherichia Coli / 대한임상미생물학회지

BACKGROUND: Extended-spectrum beta-lactamase (ESBL) producing Enterobacteriaceae are a serious problem worldwide because of their resistance to all beta-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.