Risk factors associated with typhoid fever in Son La province, northern Vietnam

Between July and December 2002, we undertook a hospital-based case-control study to identify risk factors associated with typhoid fever in Son La province, northern Vietnam. Among 617 suspected cases, 90 cases of typhoid fever were confirmed by blood or stool culture. One hundred and eighty controls (neighbours of typhoid cases matched for gender and age) were chosen. Participants were interviewed at home using a standardized questionnaire. Seventy-five per cent of cases were aged 10-44 years. No cases in patients aged less than 5 years were recorded in this study. In a conditional logistic regression analysis recent contact with a typhoid patient (OR = 3.3, 95% CI 1.7-6.2, P < 0.001), no education (OR = 2.0, 95% CI 1.0-3.7, P = 0.03) and drinking untreated water (OR = 3.9, 95% CI 2.0-7.5, P < 0.001) were independently associated with typhoid fever. Improving quality of drinking water must be a priority and health education strategies targeted at individuals with no schooling, and contacts of patients, would be expected to decrease the burden of typhoid fever.

Drug susceptibility and its genetic basis in epidemic Vibrio cholerae O1 in Vietnam

The drug susceptibility and genes responsible for the drug resistance of Vibrio cholerae O1 isolated in Vietnam in 1995, 2000 and 2002 were studied. The strains isolated in 1995 were resistant to streptomycin and harboured the class I integron which contained the aadA1 gene responsible for streptomycin resistance. The strains isolated in 2000 were devoid of a class I integron but were multiple-drug resistant and harboured SXT constin, with several drug-resistant genes. The genes responsible for streptomycin resistance were strA and strB. The strains isolated in 2002 were sensitive to all drugs examined, and the organisms were devoid of both class I integron and SXT constin. Cholera outbreaks in the three periods examined (1995, 2000 and 2002) were apparently due to different categories of V. cholerae O1.

Age-related prevalence of Shigella and Salmonella antibodies and their association with diarrhoeal diseases in Peruvian children

Shigella and Salmonella antibodies in relation to diarrhoea were studied in a cohort of 413 children between 2 and 27 months of age in peri-urban Lima, Peru. Blood samples were obtained at 2, 3 and 12 months of age. Antibody titres against lipopolysaccharide from Shigella flexneri serotype Y, Shigella dysenteriae serotype 1, Shigella sonnei, Salmonella serogroups AO, BO, DO, and Shigella Ipa and Salmonella typhi Vi antigens were measured by enzyme immunoassay. IgG titres against S. flexneri and Shigella Ipa were higher at 2 than at 3 or 12 months of age (p=0.001), while the changes in IgG titres against S. dysenteriae, S. sonnei and Salmonella were not pronounced. IgA and IgM titres against S. flexneri, Shigella Ipa, S. dysenteriae, S. sonnei and Salmonella were significantly higher at 12 than at 2 or 3 months of age (p=0.001). Stool samples were obtained from children in 64% of all diarrhoeal episodes. Shigella spp. were isolated from 20% of the children during the first 2 y of life and Salmonella in 3%. Most isolates were from children at 13-24 months of age (78%). IgG antibodies at 12 months of age did not protect against shigellosis during the second year of life.

Safety and immunogenicity study of the auxotrophic Shigella flexneri 2a vaccine SFL1070 with a deleted aroD gene in adult Swedish volunteers

The live auxotrophic Shigella flexneri 2a vaccine strain SFL1070 with a deleted aroD gene was given orally to 37 adult Swedish volunteers who received three doses within 5 days. Each dose comprised 1 x 10(5) (n = 9), 1 x 10(7) (n = 10), 1 x 10(8) (n = 9) or 1 x 10(9) (n = 9) c.f.u. S. flexneri SFL1070. One volunteer vaccinated with 1 x 10(7) and three vaccinated with 1 x 10(8) c.f.u. reported mild gastrointestinal symptoms after the first dose. Vaccination with 1 x 10(9) c.f.u. caused abdominal pain and watery diarrhoea in four volunteers who all recovered spontaneously within 72 h. S. flexneri SFL1070 was not recovered from volunteers given 1 x 10(5) c.f.u., but was shed in faeces by six volunteers vaccinated with 1 x 10(7), by all nine vaccinated with 1 x 10(8), and by seven volunteers vaccinated with 1 x 10(9) c.f.u. The mean excretion time was 2.6 (range 0-4) days in the 1 x 10(8) and the 1 x 10(9) groups. Serum antibody responses against either S. flexneri 2a and Y lipopolysaccharides (LPSs) or Shigella invasion plasmid antigens (Ipa) were seen in eight volunteers vaccinated with 1 x 10(9) (p < 0.01 to p < 0.05 for mean relative titres of IgA and IgG against S. flexneri 2a and Y LPSs), in four vaccinated with 1 x 10(8), and in two and one volunteers each vaccinated with 1 x 10(7) and 1 x 10(5) c.f.u. of S. flexneri SFL1070. Intestinal sIgA responses to the same antigens were elicited in all volunteers in the 1 x 10(9) and the 1 x 10(8) groups, and in six and one volunteers vaccinated with 1 x 10(7) and 1 x 10(5) c.f.u., respectively. The sIgA responses against S. flexneri 2a and Y LPSs were significant in all but the 1 x 10(5) group (p < 0.01 to p < 0.05). Significant antibody-secreting cell (ASC) responses specific to S. flexneri 2a LPS were seen in peripheral blood from eight volunteers each in the 1 x 10(9) and 1 x 10(8) groups and from five volunteers vaccinated with 1 x 10(7) c.f.u. (p < 0.01 to p < 0.05). The number of volunteers showing anti-Shigella Ipa ASC responses in these groups were five (p < 0.01 to p < 0.05), three and one, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Penetration of cefamandole, cephalothin, and desacetylcephalothin into fibrin clots

The conversion of cephalothin into a less active metabolite (desacetylcephalothin) might influence its distribution in tissues. An experimental rabbit model devised to determine concentrations of antibiotics in subcutaneous fibrin clots was used in this study. Groups of five to six animals received 100-mg/kg intravenous injections of either cefamandole or cephalothin. One hour after the injection, the concentration of cefamandole in serum was 20 times higher than that of cephalothin. Whereas cephalothin was undetectable at 4 h, cefamandole was still detectable at the end of the experiment. The half-lives of cephalothin and cefamandole in serum were 16 and 27 min, respectively. The concentration of cefamandole found in fibrin clots was severalfold higher than that of cephalothin. The half-life of cefamandole in clots (81 min) was superior to that of cephalothin (38 min). Although concentrations of both antibiotics were higher in serum than in clots at 1 h, the concentrations of these drugs in the clots persisted at higher levels throughout the next 5 h of the experiment. The extent of binding of cefamandole (87%) to rabbit serum was greater than that of cephalothin (50%). At least 55% of cephalothin was metabolized in vivo into its less active metabolite desacetylcephalothin. This metabolite was found in higher proportion in the serum (75%) than in the clots (55%). Whereas only 12% of the free (unbound) cephalothin reached the clots, 78% of the free cefamandole was found in the clots. This lower level of penetration of unbound cephalothin might be explained by the short half-life of this antibiotic, not permitting equilibrium to occur.