[Microbiological and epidemiological characteristics of vancomycin-dependent enterococci].

BACKGROUND: Vancomycin-dependent enterococci (VDE) are clinically equivalent to vancomycin-resistant enterococci (VRE), but more difficult to detect. This study was purposed to characterize VDE microbiologically and epidemiologically. METHODS: The patients from whom VDE were detected from April 2007 to March 2008 were investigated. For available isolates, minimal inhibitory concentrations (MICs) of and the levels of dependence on vancomycin and teicoplanin were measured by E test (AB Biodisk, Sweden), and a test for reversion of VDE to non-dependent VRE (NDVRE) and pulsed field gel electrophoresis (PFGE) were performed. Patients' demographic and clinical findings were reviewed via electronic medical records. RESULTS: VDE were recovered from 6 (2.2%) of 272 patients carrying VRE during this study period. All patients were already colonized or infected by VRE and treated with vancomycin for 13 to 107 days. VDE were isolated from pleural fluid (one), urine (four), and stool (one). All isolates carried vanA with vancomycin MICs of >256 microg/mL, but two of them had intermediate susceptibilities to teicoplanin. Because 4 VDE isolates were reverted to NDVRE with single passage, vancomycin dependence was measurable for only two isolates as equal and above 0.064 and 0.5 microg/mL respectively, and was reverted after 5 and 7 passages, respectively. Six VDE isolates showed no related clones in PFGE analysis, and 3 of 4 available pairs of initial VRE isolates and subsequent VDE isolates were identical clones. CONCLUSIONS: VDE were not rare and seemed to emerge independently from VRE with a prolonged use of vancomycin. Vancomycin-dependence was reverted within several passages.

[Evaluation of the MicroScan NegCombo panel Type 44 for detection of extended-spectrum beta-lactamase among clinical isolates of Escherichia coli, Klebsiella species, and Proteus mirabilis].

BACKGROUND: Accurate and rapid detection of extended-spectrum beta-lactamases (ESBLs) is important in guiding proper antimicrobial therapy for infected patients. We evaluated the performance of MicroScan NegCombo Type 44 panel (Dade Behring, USA), which was developed to confirm ESBL-producing Enterobacteriaceae using ceftazidime/clavulanate and cefotaxime/clavulanate. METHODS: From August 30 to September 20, 2007, 206 non-duplicate clinical isolates, including 106 Escherichia coli, 81 Klebsiella pneumoniae, 11 Klebsiella oxytoca, and 8 Proteus mirabilis were subcultured and tested with Type 32 and Type 44 panels. The results were compared with those of the CLSI phenotypic confirmatory test (CLSI-PCT) and disk approximation test (DAT). Isolates not susceptible to cefotetan or flagged as "Possible ESBL, unable to interpret confirm test (Possible ESBL)" on Type 44 panel were tested with boronic acid disks to confirm AmpC beta-lactamases (AmpC) production. RESULTS: Of the 206 isolates tested, 44 (21.4%) produced ESBL by CLSI-PCT or DAT, including 27 E. coli, 14 K. pneumoniae, 2 K. oxytoca, and 1 P. mirabilis. Thirty-eight isolates flagged as "Confirmed ESBL" on Type 44 panel were all confirmed as ESBL-producers. Of 14 K. pneumoniae flagged as "Possible ESBL", 6 were confirmed as ESBL and AmpC co-producers and 8 as AmpC-producers. CONCLUSIONS: Type 44 panel showed an excellent performance in detecting ESBL-producing E. coli, Klebsiella spp., and P. mirabilis. When flagged as "Confirmed ESBL", no other confirmatory test was necessary to report as ESBL; however, "Possible ESBL" required a differential test for AmpC production.

[Evaluation of combination of BACTEC mycobacteria growth indicator tube 960 system and Ogawa media for mycobacterial culture].

BACKGROUND: The combined use of liquid media and solid media is recommended for mycobacterial culture. We evaluated diagnostic performance of combination of BACTEC Mycobacteria Growth Indicator Tube (MGIT; Becton Dickinson, USA) and 2% Ogawa media (Korean Institute of Tuberculosis, Korea) for recovery of mycobacteria. METHODS: In September 2007, 1,764 specimens from 1,059 patients were cultured with MGIT and Ogawa. Acid fast bacilli (AFB) smear was fluorochrome-stained. The isolates were identified into Mycobacterium tuberculosis (MTB) and nontuberculous mycobacteria (NTM) with PCR using Seeplex TB Detection Kit (Seegene, Korea). Recovery rate, time to detection (TTD), contamination rate, mixed growth rate and species distribution were analyzed. RESULTS: Two hundred thirty-five specimens (13.3%) from 165 patients (15.6%) were positive for mycobacterial culture. Recovery rates of mycobacteria from the group using both media, MGIT only, and Ogawa only were 13.3%, 12.1%, and 7.8%, respectively. While MGIT recovered 98.9% of MTB and 79.7% of NTM, Ogawa recovered 65.9% of MTB and 54.1% of NTM. TTDs of total mycobacteria/MTB/NTM in MGIT and Ogawa were 10.6/11.4/9.7 days and 31/29/33 days, respectively. MGIT TTDs of total mycobacteria/MTB/NTM from AFB-positive specimens were significantly shorter than those of AFB-negative specimens; 8.2/9.5/4.4 days vs 11.6/12.7/10.7 days. Contamination and mixed growth rate of MGIT were 9.6% and 3.7%. Primary culture of Ogawa recovered 1 MTB and 1 NTM among the 170 MGIT-contaminated specimens and 38 mycobacteria among 66 specimens that showed mixed cultures of MGIT. CONCLUSIONS: MGIT warrants sensitive and rapid isolation of mycobacteria. However, the combination of MGIT and Ogawa is more desirable to recover mycobacteria in the case of contaminations or mixed cultures.

[Evaluation of the OC-SENSOR neo system for testing fecal occult blood].

BACKGROUND: Fecal occult blood tests (FOBTs) have been widely used as a means of colorectal cancer screening. Automated FOBTs using immunologic principles have the advantages such as quantitation, high specificity, and high throughput. We evaluated a newly-introduced automated FOBT analyzer, OC-SENSOR neo (OC neo) (Eiken Chemical Co., Japan). METHODS: The precision, linearity, and carry-over rate of OC neo were assessed with specimens prepared in accordance with the guidelines of CLSI. We performed a parallel test between OC neo and OC-SENSOR I (OC I) (Eiken Chemical Co.) using 300 consecutive stool specimens and 60 OC I-positive specimens. The results were analyzed with SPSS version 13.0 (SPSS Inc., USA). RESULTS: The coefficients of variation (CV) of within-run, between-run, and between-day using OCControl L (Eiken Chemical Co.) of ca. 150 ng/mL were 3.5-7.8%, 4.5-8.8% and 4.9-5.0%, respectively. The linear regression coefficient and carry-over rate with the range of 67.8-939.4 ng/mL were 0.9998 (P<0.001), and 0.1%, respectively. Correlation coefficient between OC neo and OC I was R2=0.954 (P<0.001) for 60 OC I-positive specimens. The positive and negative interpretations of 300 consecutive specimens by OC neo were completely consistent with those of OC I. CONCLUSIONS: Because OC neo showed an excellent performance and a good correlation with OC I, OC neo warrants to be a reliable quantitative FOBT system for high volume laboratories.

[Development of Secondary Order System for Laboratory Tests without Additional Blood Sampling.].

BACKGROUND: Additional tests ordered by doctors after checking abnormal routine test results for inpatients are usually delayed for one day or more, which in turn delays diagnostic and therapeutic procedures and prolongs length of stay (LOS) for the patients. We at Department of Laboratory Medicine, Asan Medical Center (AMC), established a "secondary order system for laboratory tests without additional blood sampling" to improve the conventional reflexive tests. METHODS: Oracle 8.0 (Oracle Co., Belmont, CA, USA) was used for data base software and Powerbuilder (Powersoft, Burlington, UK) for client development tool. Specimens subjected to "reflexive tests by doctors without additional blood sampling" were SST tubes for routine chemistry and EDTA for routine hematology requested in the morning of additional requests of the laboratory tests. RESULTS: Programs of registration and request for "reflexive tests by doctors without additional blood sampling" and bar code printing were developed for clinicians to check the routine test results and to order additional tests, if necessary, and for laboratory to perform the requested tests using the same samples used for routine chemistry and hematology tests in the morning. Additionally requested tests were done by finding the SST and EDTA samples, putting newly printed bar code, and processing them as usual. In February 2004, right after introducing reflexive tests by doctors without additional blood sampling, 75 additional requests were made for 50 patients, but they increased gradually up to 1,020 tests for 698 patients in December 2004. In 2005, the monthly average number of tests was 1,035 for 742 patients. CONCLUSIONS: The reflexive tests by doctors without additional blood sampling developed at AMC helped establish a rapid reporting of test results, which in turn reduced LOS related to laboratory. It also increased patient satisfactory indices by reducing repeated blood sampling and would also contribute to the financial health of the hospital.