M. Ansaruzzaman

Large epidemic of cholera-like disease in Bangladesh caused by Vibrio cholerae 0139 synonym Bengal

Abstract Epidemics of cholera caused by Vibrio cholerae 01 occur regularly in Bangladesh, but until lately V cholerae non-01 has been associated only with sporadic cases of diarrhoeal disease in many parts of the world, including Bangladesh. We describe a large epidemic of cholera-like disease in Bangladesh that is due to a V cholerae non-01. The epidemic began in December, 1992, in southern Bangladesh and spread throughout the country. By the end of March 107 297 cases of diarrhoea and 1473 deaths had been reported. The disease is indistinguishable from cholera in clinical features and response to treatment, but most of the cases are in adults, which suggests that the population has no previous immunological experience of the organism. At two centres 375 (40%) of 938 and 236 (48%) of 492 rectal swabs were positive for V cholerae non-01, as were 5 of 54 surface water samples. 55 isolates of V cholerae non-01 were studied in detail. They resembled El Tor vibrios in being resistant to polymyxin B and positive for agglutination of chicken erythrocytes. The strain did not belong to any of the 138 known V cholerae serogroups; so a new serogroup 0139, with the suggested name Bengal, is proposed. All the isolates studied produced large amounts of an enterotoxin apparently identical to cholera toxin. This strain seems to have pandemic potential. It is important that other countries in southeast Asia are aware of the strains potential to cause severe morbidity and mortality.

Sharing of virulence-associated properties at the phenotypic and genetic levels between enteropathogenic Escherichia coli and Hafnia alvei

Seven strains of Hafnia alvei isolated from diarrhoeal stools of children resembled enteropathogenic Escherichia coli (EPEC) in that they produced attaching-effacing (AE) lesions in rabbit ileal loops and fluorescent actin staining in infected HEp-2 cells. In addition, a DNA probe from a chromosomal gene required by EPEC to produce AE lesions, hybridised to chromosomal DNA from all seven H. alvei strains. These findings indicate that there is a sharing of virulence-associated properties at the phenotypic and genetic levels by H. alvei and EPEC. H. alvei strains with these properties should be considered diarrhoeagenic.

Prevalence of the Pandemic Genotype of Vibrio parahaemolyticus in Dhaka, Bangladesh, and Significance of Its Distribution across Different Serotypes

ABSTRACT Sixty-six strains of Vibrio parahaemolyticus belonging to 14 serotypes were isolated from hospitalized patients in Dhaka, Bangladesh, from January 1998 to December 2000. Among these, 48 strains belonging to four serotypes had the pandemic genotype and possessed the tdh gene. A marker (open reading frame ORF8) for a filamentous phage previously thought to correspond to the pandemic genotype was found to have a poor correlation with the pandemic genotype.

Pandemic Serovars (O3:K6 and O4:K68) of Vibrio parahaemolyticus Associated with Diarrhea in Mozambique: Spread of the Pandemic into the African Continent

ABSTRACT Forty-two episodes of Vibrio parahaemolyticus infections were detected in Beira, Mozambique, from January to May 2004. The majority of the isolates (81%) belonged to the pandemic serovars (O3:K6 and O4:K68) of V. parahaemolyticus. The pandemic serovars were positive by group-specific PCR (GS-PCR) and a PCR specific for open reading frame ORF8 (ORF8-PCR), which are molecular markers of the pandemic clone, and were positive for tdh but negative for trh. The remaining 19% of the strains also possessed the tdh gene but were GS-PCR and ORF8-PCR negative and did not belong to the pandemic serovars. Patients with V. parahaemolyticus infection were older (mean age, 27 years) than patients infected by other diarrheal agents (mean age, 21 years). Ten percent of diarrhea patients from whom no V. parahaemolyticus was cultured were severely dehydrated, but none of the V. parahaemolyticus cases were severely dehydrated. This is the first report of the isolation of pandemic strains of V. parahaemolyticus in sub-Saharan Africa and clearly indicates that the pandemic of V. parahaemolyticus has spread into the African continent.

Diverse CTX Phages among Toxigenic Vibrio cholerae O1 and O139 Strains Isolated between 1994 and 2002 in an Area Where Cholera is Endemic in Bangladesh

ABSTRACT PCR surveillance of the rstR genes of CTX phages in Vibrio cholerae O1 and O139 showed no relationship between the incidence of disease and changes in the rstR but showed variations in their presence in O1 and O139 strains and the occurrence of multiple types in a few strains.

Phenotypic and genotypic characterization of provisional serotype Shigella flexneri 1c and clonal relationships with 1a and 1b strains isolated in Bangladesh.

ABSTRACT The serotypes of 144 strains of Shigella flexneri serotype 1 (serotypes 1a, 1b, and 1c) isolated from patients attending the Dhaka treatment center of the International Centre for Diarrhoeal Disease Research, Bangladesh, between 1997 and 2001 were serologically confirmed by using commercially available antisera and a panel of monoclonal antibodies specific for S. flexneri group and type factor antigen (MASF). Among serotype 1 isolates, the prevalence of provisional serotype S. flexneri 1c increased from 0 to 56% from 1978 to 2001 in Bangladesh. Detailed biochemical studies revealed that none of the strains of serotype 1 produced indole, while all the strains fermented mannose, mannitol, and trehalose. Twenty percent of the serotype 1c and all the serotype 1a strains fermented maltose and 53% of the serotype 1c strains and 60% of the serotype 1a strains fermented arabinose, whereas all serotype 1b strains were negative for fermentation of these sugars. Only 18% of serotype 1b strains were resistant to nalidixic acid, and most of the serotype 1c and 1b strains were resistant to ampicillin, tetracycline, and trimethoprim-sulfamethoxazole. All the strains of serotypes 1a and 1b and about 88% of the serotype 1c strains were found to be invasive by the Sereny test, had a 140-MDa plasmid, and had Congo red absorption ability. Plasmid profile analysis showed that 26% of the strains of serotype 1 contained identical patterns. Most of the serotype 1c strains (72%) had the 1.6-MDa plasmid, which was not found in either serotype 1a or 1b strains. A self-transmissible middle-range plasmid (35 to 80 MDa) was found in some strains carrying the multiple-antibiotic-resistance gene. Pulsed-field gel electrophoresis analysis yielded three types (types A, B, and C) with numerous subtypes among the serotype 1c strains, whereas serotypes 1b and 1a yielded only one type for each serotype, and those types were related to the types for serotype 1c strains. Ribotyping analysis yielded three patterns for serotype 1c strains and one pattern each for serotype 1a and 1b strains which were similar to the patterns for the serotype 1c strains. Overall analysis of the results concluded that subserotype 1c is closely related to serotypes 1a and 1b. Furthermore, the high rate of prevalence of serotype 1c necessitates the commercial production of antibody against this subserotype to allow the determination of the actual burden of shigellosis caused by provisional serotype 1c.

Multiply antibiotic-resistant Vibrio cholerae O1 biotype El Tor strains emerge during cholera outbreaks in Zambia.

Antibiotic resistance data, made available from laboratory records during eight cholera outbreaks between 1990 and 2004 showed Vibrio cholerae serogroup O1 to have a low level of resistance (2-3%) to tetracycline during 1990-1991. Resistance increased for tetracycline (95%), chloramphenicol (78%), doxycycline (70%) and trimethoprim-sulphamethoxazole (97%) in subsequent outbreaks. A significant drop in resistance to tetracycline and chloramphenicol followed the adoption of a national policy to replace tetracycline with erythromycin for treating cholera. Sixty-nine strains from cholera outbreaks in Zambia between 1996 and 2004, were examined for antibiotic resistance and basic molecular traits. A 140 MDa conjugative, multidrug-resistant plasmid was found to encode tetracycline resistance in strains from 1996/1997 whereas strains from 2003/2004 were resistant to furazolidone, but susceptible to tetracycline, and lacked this plasmid. PCR revealed 25 of 27 strains from 1996/1997 harboured the intl1 class 1 integron but lacked SXT, a conjugative transposon element. Similar screening of 42 strains from 2003/2004 revealed all carried SXT but not the intl1 class 1 integron. All 69 strains, except two, one lacking ctxA and the other rstR and thus presumably truncated in the CTX prophage region, were positive for important epidemic markers namely rfbO1, ctxA, rstR2, and tcpA of El Tor biotype. Effective cholera management is dependent on updated reports on culture and sensitivity to inform the choice of antibiotic. Since the emergence of antibiotic resistance may significantly influence strategies for controlling cholera, continuous monitoring of epidemic strains is crucial.

Altering Trends in the Dominance of Shigella flexneri Serotypes and Emergence of Serologically Atypical S. flexneri Strains in Dhaka, Bangladesh

ABSTRACT Of 469 recently isolated Shigella flexneri strains, 452 agglutinated with Shigella flexneri-specific monoclonal antibodies. Of these, 396 could be assigned to 10 of the currently recognized 15 serotypes, with S. flexneri 2b dominating (23.2%). Of the 56 untypeable strains which showed invasive properties, 17 were serologically atypical and the remaining 39 belonged to a new serotype.

Field evaluation of a rapid immunochromatographic dipstick test for the diagnosis of cholera in a high-risk population

BackgroundEarly detection of cholera outbreaks is crucial for the implementation of the most appropriate control strategies.MethodsThe performance of an immunochromatographic dipstick test (Institute Pasteur, Paris, France) specific for Vibrio cholerae O1 was evaluated in a prospective study in Beira, Mozambique, during the 2004 cholera season (January-May). Fecal specimens were collected from 391 patients with acute watery nonbloody diarrhea and tested by dipstick and conventional culture.ResultsThe overall sensitivity and specificity of the rapid test compared to culture were 95% (95% confidence interval [CI]: 91%–99%) and 89% (95% CI: 86%–93%), respectively. After stratification by type of sample (rectal swab/bulk stool) and severity of diarrhea, the sensitivity ranged between 85% and 98% and specificity between 77% and 97%.ConclusionThis one-step dipstick test performed well in the diagnosis of V. cholerae O1 in a setting with seasonal outbreaks where rapid tests are most urgently needed.

Multilocus variable-number tandem repeat analysis of Vibrio cholerae O1 El Tor strains harbouring classical toxin B

Atypical Vibrio cholerae O1 strains - hybrid strains (strains that cannot be classified either as El Tor or classical biotype) and altered strains (El Tor biotype strains that produce classical cholera toxin) - are currently prevalent in Asia and Africa. A total of 74 hybrid and altered strains that harboured classical cholera toxin were investigated by multilocus variable-number tandem repeat analysis (MLVA). The results showed that the hybrid/altered strains could be categorized into three groups and that they were distant from the El Tor strain responsible for the seventh cholera pandemic. Hybrid/altered strains with a tandem repeat of the classical CTX prophage on the small chromosome were divided into two MLVA groups (group I: Mozambique/Bangladesh group; group III: Vietnam group), and altered strains with the RS1-CTX prophage containing the El Tor type rstR and classical ctxB on the large chromosome were placed in two MLVA groups (group II: India/Bangladesh group; group III: India/Vietnam group).