Infection of less virulent Helicobacter pylori strains in asymptomatic healthy individuals in Thailand as a potential contributing factor to the Asian enigma.

In Thailand, gastric cancer incidence is considerably low despite the high prevalence of Helicobacter pylori infection. We investigated the prevalence of H. pylori infection and the genotypes of cagA by using 179 stool specimens obtained from asymptomatic Thai individuals. In this study, the prevalence of H. pylori infection was 43.6%, and the detection rate of cagA-positive strains was 43.5%. In addition, the proportion of the highly virulent East-Asian type of cagA was 7.2%. These results indicate that the low prevalence of cagA-positive H. pylori strain as well as the low prevalence of East-Asian genotype cagA-positive strains may contribute to the low gastric cancer incidence.

Antimicrobial susceptibility of enterococci in Thailand from 2000 to 2005.

OBJECTIVE: To determine the trends of antimicrobial susceptibility of enterococci in Thailand from 2000 to 2005. MATERIAL AND METHOD: All enterococcal isolates from sterile site obtained from 28 hospitals in Thailand from 2000 to 2005 were tested for their susceptibility to ampicillin, high-level gentamicin, and vancomycin by the disk diffusion (Kirby Bauer) method. The relevant data were collected and analyzed by WHONET software program supported by the World Health Organization. RESULTS: Enterococcus faecalis (47%) and E. faecium (23%) were the two most frequent enterococcal isolates. There was no trend of increasing resistance to ampicillin, high level gentamicin, and vancomycin among E. faecalis isolates during the study period. There was a trend of an increasing resistance to ampicillin and high-level gentamicin among E. faecium isolates. Among E. faecium, the rates of vancomycin resistance were very low, ranging from 0.5% to 1.9%, and there was no trend of increasing rates of resistance. CONCLUSION: In the present study, there is a trend of decreasing susceptibility to ampicillin and high-level gentamicin in E. faecium. In contrast, there is no trend of increasing resistance to vancomycin. This would have effects on selection of empirical antimicrobial treatment on enterococcal infections especially a decision to use ampicillin or gentamicin.

Serotypes, antimicrobial susceptibility, and gyr A gene mutation of Campylobacter jejuni isolates from humans and chickens in Thailand.

In Thailand, 51% (36/70) Campylobacter jejuni isolates from humans and 68% (47/69) isolates from poultry were classified into 10 Penner serotypes (serotype B, C, R, E, G, A, K, D, I, and L) and 9 serotypes (serotype A, C, I, K, B, E, S, D, and L), respectively. The rate of antimicrobial drug resistance to nalidixic acid, ciprofloxacin, ampicillin, tetracycline, and erythromycin shown by human isolates were 96%, 96%, 29%, 57%, and 14%, while that shown by poultry isolates were 77%, 77%, 22%, 26%, and 17%, respectively. All quinolone-resistant strains contained a mutation in the gyrA gene (T(86)-->I(86)), suggesting that the strains were already widespread in Thailand.

Serotypes and antimicrobial resistance of streptococcus pneumoniae in Thailand 2002-2004.

Information on pneumococcal isolates is limited in Asia. Among children younger than 5 years in rural Thailand, nasopharyngeal colonization was 60%, and 55% of carried and 62% of invasive isolates were serotypes in the 7-valent pneumococcal conjugate vaccine. Nonsusceptibility was common among the serotypes included in the vaccine. Pneumococcal conjugate vaccine might be a useful prevention tool in Thailand.

Antimicrobial resistance among Clostridium perfringens isolated from various sources in Thailand.

Antimicrobial resistance among Clostnridium perfringens isolated from feces of humans and pigs, food and other environmental sources was examined by testing of 201 PCR-confirmed strains for resistance to 7 antimicrobial agents. The minimal inhibitory concentrations (MICs) were determined by the agar dilution method. Overall, C. perfringens showed the highest resistance to tetracycline (56.2%), followed by imipenem (24.9%), metronidazole (9.5%), penicillin G (9%), vancomycin (4.5%), chloramphenicol (3%) and ceftriaxone (1%). The majority of the isolated strains from pig feces (77.8%), environment (72.7%), human feces (44.9%) and food (28%) showed resistance to tetracycline. Strains isolated from human feces only showed low resistance to ceftriaxone (2.5%) and vancomycin (10.1%). Penicillin G had high activity, with overall MIC50 and MIC90 of 0.06 and 1.0 microg/ml, respectively, and low rate of resistance (10-12% for strains isolated from humans, animals and food). Among 62.7% of antimicrobial resistant strains, 39.3% were resistant to a single drug and 23.4% were multiple-drug resistant (MDR). Of overall 47 MDR strains, 63.8% were derived from human feces and were resistant to two to six drugs.

Serotypes and antimicrobial resistance of Campylobacter jejuni isolated from humans and animals in Thailand.

We investigated the serotypes, distributions, and antimicrobial resistance of Campylobacter jejuni isolates from humans and animals as a source of infection in poultry between 2002 and 2003. A total of 50 C. jejuni isolates from humans and 29 C. jejuni isolates from poultry were studied for serotype using the Penner serotyping scheme and the drug susceptibilities of the isolates which were determined for 7 antimicrobial drugs using the disk diffusion method. Serotype B (10%), serotype E (8%) and serotype R (8%) were found in humans isolates, while serotype A (27%) was most freguently isolated from poultry, followed by serotype K (21%) and serotype C (13%). Resistance in human isolates to cephalothin was high (100%). Resistance to trimethoprim/sulfamethoxazole, ciprofloxacin, and nalidixic acid were observed in 90, 82 and 78% of isolates, respectively. Most of the isolates (88%) were susceptible to erythromycin. High levels of resistance to drugs (ciprofloxacin and nalidixic acid) were observed in the isolates from poultry. These results indicate the importance of poultry as a reservoir of C. jejuni infection in Thailand is limited. In addition, a high proportion of the isolates were resistant to antimicrobial drugs, particularly the quinolone group.