Discriminatory powers of molecular typing techniques for methicillin-resistant Staphylococcus aureus in a university hospital, Thailand.

Discriminatory powers of various molecular techniques were evaluated for typing of methicillin-resistant Staphylococcus aureus (MRSA) isolated in Siriraj Hospital, Bangkok, Thailand. Thirty MRSA isolates were randomly selected in this study. They were characterized by pulsed-field gel electrophoresis, Clal-mecA and Clal-Tn554 polymorphisms, ribotyping, and PCR-based methods including SCCmec typing, spa and coa gene polymorphism, and repeat units in hypervariable region downstream of mecA. Individual molecular typing technique distinguished those MRSA isolates into 2 to 5 types. Eleven genetic backgrounds of MRSA isolates were elucidated by combination of typing methods with trimethoprim/sulfamethoxazole (TMP/SXT) susceptibility. Combination of all typing methods including TMP/SXT susceptibility yielded a discriminatory index of 0.94. Combination of PCR-based methods and TMP/SXT susceptibility, with the discriminatory index of 0.89, is a practical typing approach suitable for rapid epidemiological investigation of MRSA isolates in a hospital setting.

Detection of Clostridium difficile toxin A and B genes from stool samples of Thai diarrheal patients by polymerase chain reaction technique.

The prevalence of Clostridium difficile isolated from stools of Thai adult patients with suspected antibiotic-associated diarrhea (AAD) was 18.64 per cent. The recovery rate of toxin genes (tcdA and tcdB) by polymerase chain reaction (PCR) from stool samples yielded almost the same compared to the recovery rate of the toxin detection by enzyme immunoassay (EIA), which were 44.9 per cent and 46.7 per cent, respectively. Correlation of toxin gene detection by PCR and toxin detection by EIA was 90.6 per cent. All but one stool sample, the tcdA gene was detected together with the tcdB gene. Both genes were always detected together from tox gene-positive strains. Although, there were some discrepancy results for certain samples, the direct PCR-based-detection of C. difficile tox genes in stool samples seems to be the appropriate method for the diagnosis of C. difficile diarrhea. The PCR assay should be a recommended technique to be used routinely in laboratories. Further optimization of the technique to increase the sensitivity of the PCR assays is still needed. However, a quantitative isolation of the organism from stools of suspected antibiotic-associated diarrhea (AAD) or antibiotic-associated colitis (AAC) patients may give some evidence for clinicians in hospitals who cannot perform PCR-based or EIA-based techniques, since 48.6 per cent of the isolates were demonstrated as toxigenic strains.