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.

These results revealed the occurrence of three distinct clusters from different wards in Siriraj Hospital. The toxigenic C. difficile of PFGE type A and related subtypes was a predominant infective clone in adult patients, whereas non-toxigenic C. difficile types B2 and D were encountered in asymptomatic infants. This information can be useful in epidemiologic investigations.

SummaryA case control study was conducted to determine the risk factors of non-typhoidal Salmonella bacteraemia. Eighty adult patients with non-typhoidal Salmonella bacteraemia admitted to Siriraj Hospital from January to December 1993 served as the cases. The controls comprised 3 groups: group I , 80 adult in-patients with Escherichia coli bacteraemia; group 2, 80 adult in-patients who did not have bacteraemia and had been admitted to the hospital during the same period as the cases; group 3, 80 in-patients who did not have Salmonella bacteraemia and matched the cases in terms of gender, age, hospital services and admission date. AIDS and corticosteroid use were the major risk factors for acquiring non-typhoidal Salmonella bacteraemia with an odds ratio of 7.27 to 12.31 (95% confidence interval of 3.39 to 29.40). Almost all patients with non-typhoidal Salmonella bacteraemia presented with a fever for a median duration of 7 days. AIDS patients usually had concomitant opportunistic infections. Salmonella group D was the most common serogroup. Most patients were treated with co-trimoxazole, quinolones, ceftriaxone and ampicillin. Localized suppurative complications were observed in 14% of the patients; the overall mortality rate was 36.3%, 12% of whom died prior to receiving appropriate antibiotics for Salmonella.keywords non-typhoidal Salmonella bacteraemia

To determine whether intact pks15/1 is unique to the W-Beijing family, we investigated 147 Mycobacterium tuberculosis strains with different IS6110 genotypes. Intact pks15/1 was found in 87.8% of cerebrospinal fluid and 84.9% of sputum isolates. It was found not only in W-Beijing strains (≈97%) but also in other genotypes (38.5%–100%).

BACKGROUND: Class 1 integron element is innate to most of the multidrug resistant Acinetobacter baumannii and its spread is common among international clones worldwide. The aim of this study was to document the presence of blaVEB-1 harboring class 1 integron element and its gene cassettes in Thai A. baumannii in relation to A. baumannii European clone I, AYE strain. MATERIALS AND METHODS: Thirty seven carbapenem resistant A. baumannii isolates identified in routine microbiology laboratory of Siriraj Hospital, Bangkok were studied. The dot blot hybridization was performed to detect class 1 integron element integrase gene. PCR was used to amplify blaVEB-1, arr2, cmlA, blaOXA-10 resistance cassettes, and variable region of class 1 integron element. blaVEB-1 gene was localized by southern blot hybridization. RESULTS: The prevalence of class 1 integron element was 86.48% in the isolates studied. The blaVEB-1 was present in 7 isolates however the location of blaVEB-1 gene was different in different isolate. Four isolates (Ab03-168, Ab04-28, Ab08-20, and Ab08-22) harbored calss 1 integron element variable region sized 5.5 kb as described in strain AYE. However, blaVEB-1 was only amplified from Ab03-168. The cassette organization in this isolate was 5’CS-aadB-blaVEB-1-arr2-cmlA-blaOXA- 10-aadA1-3’CS. The class 1 integron element similar to the element identified in genomic resistance island, AbaRI of European clone I, AYE was identified in Thai A. baumannii. CONCLUSIONS: blaVEB-1 harboring class 1 integron element with minor cassette variation was identified in Thai A. baumanni isolate which might suggest the spread of this resistant cassette or the spread of the European clone I in Thailand. Monitoring of the global spread of multi-resistant A. baumannii is mandatory to control the spread of resistant genes and this multi-resistant pathogen. DOI: http://dx.doi.org/10.3126/ijim.v1i1.6715Int J Infect Microbiol 2012;1(1):24-28