ABSTRACT
BACKGROUND: Commercial diagnostics are commonly used to identify gram-positive bacteria. Errors have been reported mostly at the species level. We have found certain phenotypic criteria used in API systems which significantly misidentify Leuconostoc, an emerging human pathogen, at the genus level. We also attempt to find practical, conventional phenotypic assays for accurate identification of this group of bacteria. METHODS: Clinical isolates of catalase-negative, gram-positive coccoid or coccobacillary bacteria with non-beta hemolysis in our institute during 1997-2004 were subject to an identification aid by API 20 STREP, following the instruction manual, as an aid to conventional phenotypic tests. Those identified as Leuconostoc by API 20 STREP were re-examined by the same kit and also by API 50 CHL according to the instruction manuals, by our Leuconostoc conventional phenotypic assays, by Leuconostoc- and Lactobacillus-specific PCR's, and, where possible, by 16S rDNA sequence analysis. In addition, catalase-negative gram-positive isolates during 2005-2006 which were resistant to vancomycin at high levels were also evaluated by the same phenotypic and genotypic assays. RESULTS: Out of several thousands of clinical gram-positive isolates, 26 catalase negative gram-positive isolates initially identified as Leuconostoc by API 20 STREP and 7 vancomycin-resistant gram-positive catalase-negative bacteria entered the study. 11 out of the 26 isolates and all the 7 isolates were identified as Leuconostoc by API 20 STREP. Only 5 isolates, however, were confirmed by both genotypic and all defined conventional phenotypic criteria. API 50 CHL also failed to reliably provide accurate identification of Leuconostoc. We have identified key problem tests in API 20 STREP leading to misidentification of the bacteria. A simple, conventional set of phenotypic tests for Leuconostoc identification is proposed. CONCLUSION: The current API systems cannot accurately identify Leuconostoc. Identification of vancomycin-resistant, catalase-negative gram-positive bacteria should be performed by a few practical phenotypic assays, with assistance of genotypic assays where available.
Subject(s)
Bacterial Typing Techniques/methods , Gram-Positive Bacteria/classification , Leuconostoc/classification , Genotype , Gram-Positive Bacteria/isolation & purification , Gram-Positive Bacteria/metabolism , Humans , Leuconostoc/genetics , Leuconostoc/isolation & purification , Leuconostoc/metabolism , Phenotype , Reproducibility of Results , Vancomycin/pharmacologySubject(s)
Anti-Infective Agents/pharmacology , Bacteremia/microbiology , Salmonella Infections/microbiology , Salmonella enterica/drug effects , Bacteremia/epidemiology , Ceftriaxone/pharmacology , Ciprofloxacin/pharmacology , Drug Resistance, Bacterial , Humans , Microbial Sensitivity Tests , Nalidixic Acid/pharmacology , Pilot Projects , Salmonella Infections/epidemiology , Sentinel Surveillance , Thailand/epidemiologyABSTRACT
BACKGROUND: Urinary tract infection (UTI) is common in spinal cord injured patients. The authors investigated the epidemiology of bacteria associated with UTI to select an appropriate antibiotic for empirical treatment of UTI before obtaining a bacterial culture. OBJECTIVE: To determine the prevalence, as well as the causative bacteria and their susceptibility pattern of urinary tract infection in spinal cord injured patients hospitalized to the Rehabilitation Center, Thai Red Cross Society, Samutprakarn, Thailand from January 2001 to December 2005. MATERIAL AND METHOD: A retrospective chart review of 76 spinal cord injured patients. RESULTS: Of all spinal cord injured patients, there were 50 males and 26 females, with the average age of 44.70 years. The average length of hospitalization was 104.5 days. 71.2% of the patients needed intermittent catheterization for bladder drainage, and only 2.7% had suprapubic cystostomy. None of patient had indwelling catheterization. Forty-six patients had 68 episodes of UTI (60.52%). Eighteen patients had recurrent UTI (14 patients had two episodes and four patients had three episodes). E. coli was the most common isolated pathogen (74.36%) followed by K. pneumoniae (12.82%), E. faecalis (5%) and P. mirabilis (5%). Most gram-negative pathogens were susceptible to amikacin and third generation cephalosporins. The susceptibility of these organisms to cotrimoxazole, amoxicillin/clavulanate, and ciprofloxacin were in the range of 34.6-60.0%, 44.0-50.0% and 25.9-50.0%, respectively. CONCLUSION: Urinary tract infections were commonly observed among spinal cord injured patients in the presented institution. E. coli was the most common isolated pathogen. Surprisingly, most gram-negative pathogens were resistant to cotrimoxazole, amoxicillin/clavulanate, and ciprofloxacin. An antibiotic of choice for UTI in our patients should be aminoglycoside or third generation cephalosporins.
