Chertsak Dhiraputra

First report of methicillin-resistant Staphylococcus aureus with reduced susceptibility to vancomycin in Thailand.

ABSTRACT To investigate whether there are methicillin-resistantStaphylococcus 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 (MIC50 and MIC90, respectively) were 0.5 and 1 μg/ml, respectively, with a range of 0.25 to 2 μg/ml. For teicoplanin, MIC50 and MIC90 were 2 μg/ml, with a range of 0.5 to 4 μg/ml. However, one-point population analysis identified three MRSA strains, MR135, MR187, and MR209, which contained subpopulations of cells that could grow in 4 μg 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 μg/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.

Non-typhoidal Salmonella bacteraemia: clinical features and risk factors

A 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 1, 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.

Intact pks15/1 in Non–W-Beijing Mycobacterium tuberculosis Isolates

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%).

Severe pneumococcal infection at a Thai hospital.

OBJECTIVES To determine clinical manifestations, prognostic factors, and therapeutic outcomes of severe pneumococcal infection. METHODS Hospitalized patients with specimens cultured positive for Streptococcus pneumoniae were identified retrospectively by reviewing hospital records from 1992 to May 1998 at Siriraj Hospital. RESULTS Of 205 evaluable cases, 130 (63.4%) patients were male. Nineteen (9.3%) patients were less than 2 years old, 29 (14.1%) were between 2 and 13 years, 99 (48.3%) were between 14 and 60 years, and 58 (28.3%) were over 60 years of age. From 1992 to 1997, the average admission rate was highest (36.4%) between January and March (range = 20-45%). Average admission rates during other periods ranged from 20.0% to 23.1%. Pneumonia (50.7%) and acute exacerbation of chronic obstructive pulmonary disease or infected bronchiectasis or bronchopneumonia (21.0%) were the most frequent diagnoses, followed by meningitis (14.6%) and primary sepsis without localized lesion (8. 3%). The mortality rate during the first 7 days of hospitalization was 28.8%, and thereafter, 11.7%. The odds ratios (95% CI) of old age, congestive heart failure, and alcoholism for death were 3.4 (1. 4-8.2), 8.6 (0.97-76.1), and 8.0 (3.1-20.9), respectively. For pneumonitis only, mortality rates among alcoholic and nonalcoholic patients were 76.9% and 39.6%, respectively (P = 0.025). CONCLUSIONS Patients who were alcoholic, over 60 years of age, or had congestive heart failure were vulnerable to severe pneumococcal infection with significant mortality, in spite of proper selection of empirical antimicrobials. Diabetes mellitus and multiple myeloma also contributed to late mortality after 7 days of hospitalization.