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To investigate whether there are methicillin-resistant Staphylococcus aureus (MRSA) strains with reduced susceptibility to vancomycin in Thailand, a total of 155 MRSA strains isolated from patients hospitalized between 1988 and 1999 in university hospitals in Thailand were tested for glycopeptide susceptibility. All the strains were classified as susceptible to vancomycin and teicoplanin when judged by NCCLS criteria for glycopeptide susceptibility using the agar dilution MIC determination. Vancomycin MICs at which 50 and 90% of the isolates tested were inhibited (MIC 50 and MIC 90 , respectively) were 0.5 and 1 g/ml, respectively, with a range of 0.25 to 2 g/ml. For teicoplanin, MIC 50 and MIC 90 were 2 g/ml, with a range of 0.5 to 4 g/ml. However, one-point population analysis identified three MRSA strains, MR135, MR187, and MR209, which contained subpopulations of cells that could grow in 4 g of vancomycin per ml. The proportions of the subpopulations were 2 ؋ 10 ؊4 , 1.5 ؋ 10 ؊6, and 4 ؋ 10 ؊7 , respectively. The subsequent performance of a complete population analysis and testing for the emergence of mutants with reduced susceptibility to vancomycin (MIC > 8 g/ml) confirmed that these strains were heterogeneously resistant to vancomycin. Two of these strains caused infection that was refractory to vancomycin therapy. Pulsed-field gel electrophoresis showed that the two strains had identical SmaI macrorestriction patterns and that they were one of the common types of MRSA isolated in the hospital. This is the first report of heterogeneous resistance to vancomycin in Thailand and an early warning for the possible emergence of vancomycin resistance in S. aureus in Southeast Asia.

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Burkholderia pseudomallei is isolated frequently from the soil in regions where the disease melioidosis occurs. However, recent surveys in Thailand have shown that the frequency of isolation of the organism from soil samples is not directly related to the incidence of melioidosis in an area. To determine whether strain populations of B. pseudomallei prevalent in soil are gentypically related to strains causing clinical disease, rFWA Bam HI restriction fragment length polymorphisms (RFLP) of 139 soil environmental isolates and 228 human isolates were compared. Two groups of ribotype patterns were found. Group I comprised 37 different ribotype patterns which were characterised by five to eight hybridisation bands of 2.8-> 23 kb. All of these ribotypes were identified among the clinical isolates, and 18 of them were also found in 59 environmental isolates. Group I1 was represented by 12 ribotypes found only in environmental strains. These ribotype patterns comprised one to five bands in the size range 9-> 23 kb. All but one of the 73 isolates in this group grew on a minimal medium supplemented with L-arabinose. In contrast, only 3% of the 66 isolates from the environment with group I ribotype patterns could utilise this sugar as their sole energy source. These findings suggest that B. pseudomallei strains that utilise arabinose constitute a population that is genetically distinct from other environmental and clinical strains.

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SUMMARY:Monitoring the antibiotic susceptibility pattern of Salmonella enterica serovar Typhi (S. Typhi) is important for efficiently managing cases of typhoid fever. In this study, the antimicrobial susceptibility patterns of 114 S. Typhi isolates, which were collected from a university hospital in Nepal during July 2009-December 2010, were investigated by disc diffusion assays. All of the S. Typhi isolates were sensitive to amoxycillin-clavulanic acid. More than 95z of the isolates were sensitive to chloramphenicol, ceftazidime, ceftriaxone, and cotrimoxazole. In addition, 1.7z of the studied isolates showed multiple drug resistance patterns. Of the 40 S. Typhi isolates, 32 strains (80z) showed nalidixic acid (NA) resistance with decreased susceptibility to ciprofloxacin (CIP). Importantly, we found the simultaneous presence of NA resistance and decreased susceptibility to CIP, suggesting that the resistance to NA is a reliable indicator of decreased CIP susceptibility (sensitivity, 97.5z; specificity, 100.0z). Furthermore, the sequencing of NA-resistant S. Typhi isolates showed a predominant amino acid alteration in the quinolone resistance-determining region (QRDR) of gyrA gene at position 83 from SerªPhe. Two isolates with resistance to both CIP and NA had a double-mutation (Ser83ªPhe and Asp87ªAsn) in the QRDR of the gyrA gene, of which one had an additional amino acid mutation (Ser80ªIlu) in the QRDR of the parC gene.

A Burkholderia pseudomallei-like organism has recently been identified among some soil isolates of B. pseudomallei in an area with endemic melioidosis. This organism is almost identical to B. pseudomallei in terms of morphological and biochemical profiles, except that it differs in ability to assimilate l-arabinose. These Ara+isolates are also less virulent than the Ara− isolates in animal models. In addition, clinical isolates of B. pseudomallei available to date are almost exclusively Ara−. These features suggested that these two organisms may belong to distinctive species. In this study, the 16S rRNA-encoding genes from five clinical (four Ara− and one Ara+) and nine soil isolates (five Ara− and four Ara+) of B. pseudomallei were sequenced. The nucleotide sequences and phylogenetic analysis indicated that the 16S rRNA-encoding gene of the Ara+ biotype was similar to but distinctively different from that of the Ara− soil isolates, which were identical to the classical clinical isolates ofB. pseudomallei. The nucleotide sequence differences in the 16S rRNA-encoding gene appeared to be specific for the Ara+or Ara− biotypes. The differences were, however, not sufficient for classification into a new species within the genusBurkholderia. A simple and rapid multiplex PCR procedure was developed to discriminate between Ara− and Ara+ B. pseudomallei isolates. This new method could also be incorporated into our previously reported nested PCR system for detecting B. pseudomallei in clinical specimens.