Hybrid & El Tor variant biotypes of Vibrio cholerae O1 in Thailand.

Background & objectives: El Tor Vibrio cholerae O1 carrying ctxBC trait, so-called El Tor variant that causes more severe symptoms than the prototype El Tor strain, first detected in Bangladesh was later shown to have emerged in India in 1992. Subsequently, similar V. cholerae strains were isolated in other countries in Asia and Africa. Thus, it was of interest to investigate the characteristics of V. cholerae O1 strains isolated chronologically (from 1986 to 2009) in Thailand. Methods: A total of 330 V. cholerae O1 Thailand strains from hospitalized patients with cholera isolated during 1986 to 2009 were subjected to conventional biotyping i.e., susceptibility to polymyxin B, chicken erythrocyte agglutination (CCA) and Voges-Proskauer (VP) test. The presence of ctxA, ctxB, zot, ace, toxR, tcpAC, tcpAE, hlyAC and hlyAE were examined by PCR. Mismatch amplification mutation assay (MAMA) - and conventional- PCRs were used for differentiating ctxB and rstR alleles. Results: All 330 strains carried the El Tor virulence gene signature. Among these, 266 strains were typical El Tor (resistant to 50 units of polymyxin B and positive for CCA and VP test) while 64 had mixed classical and El Tor phenotypes (hybrid biotype). Combined MAMA-PCR and the conventional biotyping methods revealed that 36 strains of 1986-1992 were either typical El Tor, hybrid, El Tor variant or unclassified biotype. The hybrid strains were present during 1986-2004. El Tor variant strains were found in 1992, the same year when the typical El Tor strains disappeared. All 294 strains of 1993-2009 carried ctxBC ; 237 were El Tor variant and 57 were hybrid. Interpretation & conclusions: In Thailand, hybrid V. cholerae O1 (mixed biotypes), was found since 1986. Circulating strains, however, are predominantly El Tor variant (El Tor biotype with ctxBC).

Genetic variations in Aeromonas hydrophila isolates from clinical and environmental sources in Thailand.

Aeromonas hydrophila, a widely distributed human pathogen causing a variety of diseases, can be isolated from clinical and environmental sources. Analysis in Thailand of 110 isolates of Aeromonas hydrophila by randomly amplified polymorphic DNA-PCR (RAPD-PCR) revealed one specific RAPD pattern group (G) that was associated only with strains from environmental sources. Cytotoxic activity, adhesion to epithelial cells and exoenzyme secretions of A. hydrophila were also investigated. A comparison of isolates with pattern group G with a set of isolates derived from human blood showed low induction of cytotoxicity from those with RAPD pattern group G suggesting low virulence of these strains.

Bacterial causes of AIDS-associated diarrhea in Thailand.

The incidence of bacterial diarrhea in AIDS patients has increased steadily and has led to enormous medical and public health problems. In this study, the clinical data together with 350 rectal swab samples each from AIDS patients with diarrhea (APD) and non-AIDS patients with diarrhea (NAPD), were collected and examined for bacterial enteropathogens at the Bamrasnaradura Infectious Diseases Hospital (BIDH), Nonthaburi, Thailand from May to December 1996. Patients were matched by age and sex. The majority of these patients were male (79%, 554/700), aged between 15 and 34 years (70.9%). The study found that the isolation rates of bacterial enteropathogens causing diarrhea in APD (18%, 62/350) were considerably lower than those in NAPD (43%, 152/350) (p<0.05). The infection rate with Salmonella group B (19.7%, 12/61) in APD was found to be significantly higher than that in NAPD (14.3%, 2/14) (p<0.05). Vibrio parahaemolyticus (53.3%, 81/152), Plesiomonas shigelloides (27%, 41/152), Aeromonas spp (19.1%, 29/152) and V. cholerae O1 (15.1%, 23/152), were more frequently detected in NAPD than in APD (p<0.05). Only nine Escherichia coli strains were isolated from APD, of which six were enteroinvasive E. coli, two enterotoxigenic E. coli and one enterohemorrhagic E. coli (non O157) possessing both vtl and vt2. No V. cholerae strains were detected in APD. The least effective antibiotics were ampicillin, tetracycline and cotrimoxazole. Antibiotic resistant patterns of the isolated organisms were similar from both groups. The results from this study might be useful in Thailand in the diagnosis and management of clinical cases of bacterial diarrhea, especially APD.

Comparison of the efficacy of ceftibuten and norfloxacin in the treatment of acute gastrointestinal infection in children.

A prospective randomized study was conducted at an infectious disease hospital in Thailand. Ceftibuten was compared with norfloxacin, both given orally for five days for treatment of acute gastroenteritis in children. One hundred and seventy cases were included in the study. Eighty-eight cases were treated with ceftibuten and eighty-two cases with norfloxacin. The baseline characteristics of the patients in both treatment groups were similar. The results showed that mean durations of diarrhea in the ceftibuten and norfloxacin groups were 2.48 days and 2.29 days, respectively, but there was no statistically significant difference between the two groups (p > 0.05). There were Salmonella spp and Shigella spp isolated in both treatment groups and all were susceptible to both antibiotics. The mean durations of Salmonella diarrhea in the ceftibuten and norfloxacin groups were 2.7 and 2.2 days, respectively, while those of Shigella diarrhea were 2.3 days and 2.0 days, respectively. There were no statistically significant differences in either comparison (p > 0.05). Neither complications nor clinical relapses were observed after both antibiotics' treatment.

Comparison of the efficacy of tetracycline and norfloxacin in the treatment of acute severe watery diarrhea.

Antibiotic treatment appears to shorten the duration of diarrhea and eradicate Vibrio cholerae. The objective of this study was to compare the efficacy of tetracycline with norfloxacin therapy in patients (adults and children) with acute severe watery diarrhea caused by VC 01 and VC 0139. Patients (adults and children) with acute severe watery diarrhea admitted to Bamrasnaradura Infectious Disease Hospital, Thailand were randomized to receive either tetracycline (500 mg qid in adults and 12.5 mg/kg qid in children) or norfloxacin (400 mg bid in adults and 7.5 mg/kg bid in children) for 3 days each. The duration of diarrhea and the fecal shedding were comparable between two groups. Thirteen cases were treated with tetracycline and twelve cases with norfloxacin. The results showed the mean duration of diarrhea in tetracycline-treated and norfloxacin-treated groups were 1.31 and 1.25 days, respectively. The mean fecal shedding in tetracycline-treated and norfloxacin-treated group were 1.38 and 1.33 days, respectively. However, there were no statistically significant differences between two groups of both comparisons (p > 0.05). All isolates (VC 01 and VC 0139) in this study were susceptible to both antibiotics. Tetracycline therapy is as good as norfloxacin therapy for quick recovery and time for bacterial eradication in patients with acute severe watery diarrhea caused by Vibrio cholerae. Children aged less than 8 years should not use tetracycline therapy because of its toxic effects.

Nontyphoidal Salmonella diarrhea in Thai children: a study at Bamrasnaradura Hospital, Nonthaburi, Thailand.

From July 1, 1994 to June 30, 1996, 394 children with Nontyphoidal Salmonella diarrhea were studied at Bamrasnaradura Infectious Disease Hospital in Thailand. The ages ranged from 1 month to 12 years (mean, 1.4 years). Eighty-seven per cent of patients were in the first 2 years of life. Diarrhea, mostly acute with watery stool and fever were the most common presenting symptoms. The duration of diarrhea ranged from 1 to 20 days (mean, 5.2 days). Salmonella group B was the most common serogroup (56.1%). Most isolates were multiresistant strains, however, they were all sensitive to norfloxacin. Four (1%) patients were HIV-infected. Pneumonia found in 2 patients (0.5%) and septicemia in 1 patient (0.3%). None of the patients died. We conclude that nontyphoidal Salmonella diarrhea in children is still endemic in Thailand, especially among infants and high multidrug resistance occurs.

Cryptosporidiosis in HIV infected patients in Thailand.

Diarrhea, mostly chronic diarrhea and weight loss are common in patients with AIDS. Cryptosporidium had been identified as responsible for chronic, debilitating secretory diarrhea in HIV infected patients. We performed a retrospective study of the prevalence, clinical features and laboratory findings of cryptosporidiosis in HIV infected patients (adults and children), in the period of 6 years from January 1988 to December 1993 at Bamrasnaradura Hospital in Nonthaburi, Thailand. In this study, Cryptosporidium was found in 22 (8.8%) by detection in stool specimens of 250 HIV infected patients with diarrhea and was found throughout the year. The prevalence rates of cryptosporidiosis in this study among children and adults were 19% and 7.9%, respectively. The common features were chronic diarrhea (84.6%), mostly watery diarrhea and weight loss/malnutrition (100%). A few fecal leukocytes were found in 15.4%.