Introduction and spread of multi-resistant Shigella dysenteriae I in Thailand

Outbreaks of Shigella dysenteriae I occurred in northeastern Thailand in the fall of 1986 and again in the spring and fall of 1987 for the first time in over 20 years. The epidemic strain of S. dysenteriae I was resistant to tetracycline, streptomycin, chloramphenicol, and trimethoprim-sulfamethoxazole, but susceptible to ampicillin. Trimethoprim resistance was chromosomally encoded by type I dihydrofolate reductase. In Ubon Province, where 10,000 cases of dysentery were reported, there were 3-5 cases of dysentery per 1,000 residents during the peak months, with 2-5 hospitalizations per 100 cases of reported dysentery. There were 2 deaths among 101 hospitalized, culture-confirmed cases. The overall case-fatality rate among reported cases of dysentery in this province was 0.9%. In contrast to S. flexneri infections, which occurred predominantly among children less than 5 years old, S. dysenteriae I infections occurred in all age groups. The large number of susceptibles appeared to be important in allowing rapid spread of S. dysenteriae I. In 1 village, 46% of 434 villagers reported dysentery; S. dysenteriae I was isolated from 24 out of 81 (30%) individuals cultured. Based on the prevalence of IgG antibody to S. dysenteriae I lipopolysaccharide, it was estimated that 76% of the villagers had been infected.     

Antimicrobial susceptibility and characterization of outer membrane proteins of Haemophilus ducreyi isolated in Thailand.

The identity of each of 239 yeasts, encompassing 9 genera and 30 species, was determined with the Quantum II and API 20C identification systems. With API 20C results accepted as being correct, Quantum II proved to be 92% accurate in identification of common isolates, e.g., Candida albicans and Torulopsis glabrata, but only 73% effective with less frequently encountered yeasts, e.g., Trichosporon beigelii and Rhodotorula glutinis. Overall, Quantum II was 86% as accurate as API 20C for the yeast isolates tested. In addition, physical problems were encountered in inoculation of Quantum II cartridges and in the automated reading of some biochemical tests. We conclude that Quantum II is not yet suitable for routine identification of clinical yeast isolates.     

Serological response to plasmid-encoded antigens in children and adults with shigellosis

The immunological response to plasmid-encoded antigens of virulent Shigella was determined in Thai children less than 4 yr of age and in Thai adults by immunoblot analysis and ELISA. Forty-two percent (8/19) of Thai children and 4% (1/22) of Thai adults with shigellosis developed a greater than or equal to 4-fold rise in IgG antibody titer to water-extracted antigens of Shigella flexneri M90T by ELISA (p = 0.006). Two children and one lactating mother with shigellosis developed a 4-fold rise in serum IgA antibody titers to water-extracted antigens of M90T. The results of the ELISA were confirmed by immunoblot analysis in all of the 41 paired sera examined. Five patients developed IgA, and four developed IgM, antibodies as detected by immunoblot analysis, that were not detected by ELISA. The reciprocal log2 geometric mean titers of antibodies to plasmid-encoded antigens in acute sera was higher in Thai adults than Thai children: IgG 7,265 versus 1,659; IgM 879 versus 480; and IgA 662 versus 60 (p less than 0.001). Thai adults had high titers of antibodies to plasmid-encoded antigens in their acute sera, but were susceptible to Shigella infections, although they were historically less susceptible than Thai children.     

Sero-epidemiological survey of Rickettsia tsutsugamushi infection in a rural Thai village

A sero-epidemiological survey of a rural Thai village demonstrated a 77% prevalence of antibody against Rickettsia tsutsugamushi in adults. Acquisition of antibody occurred very early in life, especially in females, but the prevalence of antibody in the adult population showed no statistically significant sexual distinction. Antibody against all three prototype strains was present in Thailand but antibody titres did not vary by strain type or the age of the individual.     

New paper enzyme-linked immunosorbent technique compared with microimmunofluorescence for detection of human serum antibodies to Rickettsia tsutsugamushi

A new paper enzyme-linked immunosorbent assay was developed for the screening and titration of human serum antibodies against the scrub typhus rickettsia, Rickettsia tsutsugamushi. The objetive was to provide a relatively simple method for antibody screening which required neither sophisticated laboratory equipment nor a high degree of technological skill. The technique develops an enzyme product from filter paper saturated with a 5-aminosalicylic acid substrate and enzymatically reacted with a commerically available anti-human immunoglobulin G peroxidase conjugate. The product of the enzymatic reaction can be interpreted visually. Comparison of 351 human sera tested by the immunofluorescent and paper enzyme-linked immunosorbent assays against a three-antigen pool of the Karp, Kato, and Gilliam strains of R. tsutsugamushi demonstrated an agreement of 96%. The sensitivity of the paper enzyme-linked immunosorbent assay as compared to immunofluorescence was 98.2%, and the specificity was 94.4%.     

Non-O1 Vibrio cholerae in Thailand: homology with cloned cholera toxin genes.

We examined 281 non-O1 Vibrio cholerae isolates from Thailand for homology with genes coding for cholera toxin. Five isolates from environmental sources were homologous with the cholera toxin gene probe and produced both the A and B subunits of cholera toxin.