Rifampin resistance in carbapenem-resistant Acinetobacter baumannii in Siriraj Hospital, Thailand.

There is a growing evidence on emergence of carbapenem-resistant Acinetobacter baumannii (CRAB) in Thailand and recent treatment guidelines recommend a combination therapy using carbapenem and/or polymyxin with rifampin. Rifampin would be added in a combination therapy. The susceptibility of this pathogen to rifampin is not known, so we studied the rifampin susceptibility and possible mechanisms of resistance used by CRAB. The disk diffusion test was performed on 111 clinical isolates using 5 microg rifampin disk following CLSI guidelines. The inhibition zone was interpreted based upon the recommendation for Staphylococcus aureus (inhibition zone < 20 mm = resistant). Polymerase chain reaction (PCR) using the primers specific for arr-2 encoding rifampin ADP-ribosyltransferase was performed in all isolates. The rpoB DNA sequences from two isolates, with or without arr-2, were compared. All isolates under study were rifampin resistant. Inhibition zone was < 14 mm for all isolates. The arr-2 was positive for 35 isolates (31.5%) and these isolates correlated with high level of resistance (inhibition zone < 10mm). The DNA sequences of rpoB genes in arr-2 negative isolate showed mutations L904S, P906R, K909N and M1262K that might have roles in rifampin resistance. Mutations of rpoB genes in some isolates and possession of arr-2 in class 1 integron element were mechanisms for rifampin resistance and these resistant determinants can disseminate through both vertical and horizontal gene transfer. Under this circumstance, it is not recommended to use rifampin in the treatment of carbapenem-resistant A. baumannii in Thailand.

Second-line drug susceptibilities of Thai multidrug-resistant Mycobacterium tuberculosis isolates.

The emergence of multidrug-resistant tuberculosis (MDR-TB) is increasing and is exacerbated by the human immunodeficiency virus (HIV) epidemic. The standard short-course regimen used for the treatment of tuberculosis is likely to be ineffective against MDR-TB, leading to the need for second-line drugs. In such situations, drug susceptibility testing (DST) is necessary to select an appropriate treatment regimen. In this study, DST of 99 MDR-TB strains isolated in Thailand was performed using a drug-impregnated disc method. The results showed that 94.95% of the strains were susceptible to amikacin and kanamycin, 90.91% to ciprofloxacin and ofloxacin, 85.86% to para-aminosalicylic acid, and 78.79% to ethionamide.

Characteristics of Clostridium difficile strains isolated from asymptomatic individuals and from diarrheal patients.

OBJECTIVES: To characterise genotypes of Clostridium difficile strains isolated from asymptomatic individuals and patients with diarrhea. METHODS: Fecal specimens from 235 asymptomatic infants <12 months, 76 asymptomatic children 1-11 years and 132 adult patients with antibiotic-associated and non-antibiotic-associated diarrhea obtained from Siriraj Hospital, Bangkok from October 1998 to April 1999 were examined for C. difficile by cycloserine-cefoxitin-fructose agar culture. The presence of the C. difficile toxin A gene was determined by specific PCR with the use of primers 5-(CCC AAT AGA AGA TTC AAT ATT AAG CTT)-3 and 5-(GGA AGA AAA GAA CTT CTG GCT CAC TCA GGT)-3. All C. difficile isolates were subsequently genotyped by pulsed-field gel electrophoresis (PFGE). RESULTS: The C. difficile strains were found in 28 (11.9%) asymptomatic infants, 16 (21.1%) asymptomatic children and 33 (25%) adult patients. In total, 14 PFGE types and eight subtypes designated as types A, B, C, D, E, F, G, H, I, J, K, L, M and N, and A1, A2, A3, A4, B1, B2, B3 and E1, respectively, were identified. Only two isolates from infants and 18 isolates from adult patients were toxin A gene positive by PCR. Both isolates of toxigenic C. difficile were from infants in the same ward and were PFGE type B. PFGE type A was the predominant type among all toxigenic isolates (12 of 18 isolates) from adult patients. The other PFGE types of toxigenic C. difficile found in adult patients were: type A1, one isolate; type B, four isolates; and type C, one isolate. Types B2 and D were identified in 38.5% and 46.2%, respectively, of the toxin A gene-negative isolates of C. difficile from infants. CONCLUSIONS: 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.

Nosocomial bloodstream infection in pediatric patients: Siriraj Hospital, Bangkok; 1996-1999.

A retrospective study on nosocomial bloodstream infection (NBSI) in pediatric patients hospitalized at Siriraj Hospital from January 1996 to December 1999 was performed. Of the 18,087 blood specimens sent for culture, 533 (3%) were positive for organisms after 72 hours of hospitalization and were defined as NBSI. The rate of NBSI detected in blood culture specimens was highest among neonates (5.2%). Gram-positive cocci and gram-negative rods caused NBSI in an equal proportion (46% and 44% respectively) and Candida caused 10 per cent of NBSI. Coagulase-negative staphylococci was the most common pathogen followed by K. pneumoniae and Enterobacter. Antibiogram showed that 15 of the 35 (43%) S. aureus identified were methicillin-resistant. Only 35-38 per cent of Enterobacteriaceae were sensitive to cefotaxime or ceftazidime. Cefoxitin was still effective against 95 per cent of K. pneumoniae. Compared with other third generation cephalosporins, combination of cefoperazone and betalactamase-inhibitor (sulbactam) possessed an increased in vitro efficacy against K. pneumoniae, Enterobacter, E. coli, Acinetobacter and non-fermentative gram-negative rods. Resistant rate of amikacin among all gram negative rods was 25-69 per cent. Ciprofloxacin sensitivity varied from 62-100 per cent among all gram-negative rods. Imipenem was excellent against all gram-negative rods with the sensitivity of 80-100 per cent. Epidemiological data of this study is important for the decision of the appropriate empirical antimicrobial treatment in our hospital.

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

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 (MIC50 and MIC(90), respectively) were 0.5 and 1 microg/ml, respectively, with a range of 0.25 to 2 microg/ml. For teicoplanin, MIC50 and MIC90 were 2 microg/ml, with a range of 0.5 to 4 microg/ml. However, one-point population analysis identified three MRSA strains, MR135, MR187, and MR209, which contained subpopulations of cells that could grow in 4 microg of vancomycin per ml. The proportions of the subpopulations were 2 x 10(-4), 1.5 x 10(-6), and 4 x 10(-7), respectively. The subsequent performance of a complete population analysis and testing for the emergence of mutants with reduced susceptibility to vancomycin (MIC > or = 8 microg/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.

Evaluation of susceptibility status of invasive pneumococcal isolates to various antibiotics and risk factors associated with invasive penicillin-nonsusceptible pneumococcal infection: Bangkok 1997-1998.

The antibiotic susceptibility pattern of Streptococcus pneumoniae isolated from specimens of invasive infections was examined at Siriraj Hospital, a tertiary care center in Bangkok, during December 1996 April 1998. The percentage of S. pneumoniae isolates intermediate and resistant to various antibiotics were: penicillin, 25% and 21%; amoxicillin-clavulanate, 24% and 0%; cefuroxime, 6% and 36%; cefotaxime, 6% and 1.4%; ceftibuten, 5% and 42%; imipenem 22% and 0%; co-trimoxazole, 6% and 41%; chloramphenicol, 2% and 26%; erythromycin, 12% and 16%; azithromycin, 0% and 30%; and roxithromycin 0% and 33%. Most of the penicillin-nonsusceptible S. pneumoniae (PNSP) were also nonsusceptible to other antibiotics except cefotaxime, and imipenem. The isolates from respiratory specimens have a higher rate of resistance to all antimicrobial agents with a significant rise in MIC50 of beta-lactam antibiotics. There was no difference in the outcome of infections caused by penicillin-susceptible and -nonsuscetible S. pneumoniae. The only identifiable risk factor associated with PNSP infection was prior use of antibiotic within 3 weeks.

Comparison of BACTEC automated blood culture system and conventional system in hospitalized pediatric patients.

A prospective study in pediatric patients compared the BACTEC system, an automated blood culture system using Bactec Ped Plus/F broth media, with the conventional system using Brain Heart Infusion broth media. Each single blood sample drawn for culture from hospitalized children was evaluated by both systems simultaneously. Of 244 pairs of blood samples, 44 (18%) were positive for microorganisms. Of these isolates, 24 (55%) were detected by both systems, 10 (23%) were detected by the BACTEC system only, and 10 (23%) were detected by the conventional system only. The mean turn around time of the BACTEC system (0.56 +/- 0.34, range 0.08-1.55 days) was significantly shorter than that of the conventional system (3.36 +/- 2.72, range 1-7 days, p < 0.001). Seven isolates strongly suspected to be due to contaminants grew out after 5 days of incubation and were detected by the conventional system only. In this study the BACTEC system and the conventional system were equally effective in detecting microorganisms in the patients' blood samples even if antibiotic therapy had been previously administered. However, the results from the BACTEC system were available much sooner and less likely to be contaminants.

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.

Bacterial pathogens (non-Mycobacterium) from sputum culture and antimicrobial susceptibility.

Sputum culture of patients at Siriraj Hospital, Bangkok was 49.84% positive for bacterial pathogens in 1994 and 40.95% in 1995. The average incidence of gram-negative rods was 3.11 fold more than the combination of gram-positive cocci and gram-negative cocci. The most common gram-negative rod was Pseudomonas aeruginosa, followed by either Klebsiella pneumoniae or Acinetobacter anitratus depending on year. The most common coccus was Staphylococcus aureus. From both years, the number of Haemophilus influenzae, Streptococcus pneumoniae, Burkholderia pseudomallei and Nocardia spp isolated were 122, 93, 13 and 11 strains respectively. For antimicrobial susceptibility, P. aeruginosa was sensitive to ceftazidime, imipenem, gentamicin, amikacin, netilmicin, ciprofloxacin (range 56-89%). S. aureus (MSSA) was sensitive to common used drugs. S. aureus (MRSA) was sensitive to co-trimoxazole, fosfomycin, vancomycin (range 57-100%) and resistant to most drugs.

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.

Helicobacter pylori: a comparison of CLO test and Giemsa's stain with culture in dyspeptic patients.

The prevalence of H.pylori in Thailand is high compared with Western countries and is the same as in China. We suggest either rapid urease test (CLO test) or Giemsa stain to be a rapid, reliable and convenient detection method for H.pylori and is also suitable for use in follow-up studies by gastroenterologists.

Advantage of Sandiford's counterstain in detection of Gram negative bacteria in clinical specimens.

Confirmation of bacterial in clinical specimens using Gram's stain with the Sandiford's modification was found to be more useful, especially when Gram-negative bacteria with other forms coexisted, than ordinary Gram's stain. It was useful for staining histopathological specimens also. We believe that this method deserves wider recognition and should be used as a standard procedure in laboratories.