Vibriocidal titre in cholera cases and contacts: its value in assessing endemicity of or susceptibility to cholera.

Vibriocidal antibody titre in excess of 1:40 occurred within two weeks of cholera infection, both in severe hospitalized cases, contact cases and in asymptomatic infected contacts. These levels, considered to be indicative of protection, persisted for six months or longer in more than half of the subjects irrespective of presence and severity of symptoms. Approximately 40% of infected family contacts had similar titres implying recent infection and subsequent protection. The use of antibiotics to treat acute cases, and whether infection was due to antibiotic resistant or sensitive Vibrio cholerae had no effect on the response of vibriocidal titre. Endemicity of cholera was higher than previously observed in Dhaka. Screening populations to obtain positive titre rates permits retrospective assessment of cholera infection and provides an indicator of future susceptibility.

Epidemiological differences between cholera due to multiple antibiotic resistant and multiple antibiotic sensitive Vibrio cholerae infection.

The appearance of cholera caused by multiply antibiotic resistant Vibrio cholerae in Bangladesh provided an opportunity to compare epidemiological features of infection caused by resistant and by sensitive V. cholerae. A prospective study was carried out using 46 families of hospital in-patient cholera cases due to resistant V. cholerae and 11 families of hospital cases due to sensitive V. cholerae and nine cases of cholera due to resistant and six cases due to sensitive V. cholerae detected in the neighbourhoods of hospital patients. All families were visited daily during ten days for cultures of rectal swabs, samples of domestic water and for history of diarrhoea. The results showed no significant difference in secondary infection and case rates in contacts of hospital cholera cases due to resistant and sensitive V. cholerae. However, the secondary infection rate (57%) in contacts of cases due to resistant V. cholerae detected from the neighbourhoods of hospital cases was significantly higher (p less than 0.05), than in the neighbourhood case-contacts (29%) of cases due to sensitive V. cholerae. The mean duration of diarrhoea in untreated resistant V. cholerae cases who were contacts of hospital cases (3.3 days) was significantly longer (p less than 0.05) than that of untreated sensitive V. cholerae (2.2 days). Higher isolation rates of V. cholerae were obtained from water sources used by cholera cases due to resistant V. cholerae, than from sources used by cases due to sensitive V. cholerae, but the differences were not statistically significant (p greater than 0.05). The study suggests that resistant V. cholerae poses an additional threat through a higher secondary infection rate and by causing illnesses of longer duration.

Presence of colonization factor antigens on fresh isolates of fecal Escherichia coli: a prospective study.

In Dhaka, Bangladesh, fresh isolates of Escherichia coli from 197 patients with diarrhea were investigated for production of enterotoxin and possession of colonization factor antigen (CFA) I or II. Enterotoxigenic E. coli (ETEC) was isolated from 34% of the patients, and of the 67 enterotoxin-positive strains, 75% carried CFAs. Among 68 healthy control persons no strains positive for both enterotoxin and CFA were found. The CFAs in general were restricted to certain serotypes of E. coli. In a subgroup of patients, part of an ongoing surveillance study, mixed infection was seen in 23% of those from whom recognized pathogens were identified. There was a tendency to more severe dehydration when the two virulence factors, enterotoxin and CFA, were simultaneously present.

Changes in the trend of shigellosis in Dhaka: family study on secondary infection, clinical manifestation and sensitivity pattern: 1980.

The incidence of shigellosis and the death rate have increased and the resistance of shigellae to antibiotics has changed in Dhaka during our experiences. In 1980, we investigated the secondary infection and case rates, infection to case ratio, duration of illness, excretion of shigellae and antibiotic sensitivity pattern in 100 families with cases of shigellosis, culturing rectal swabs obtained by home visits for a 10-day period. Standard methods were used for culture and sensitivity tests. The over-all secondary infection rate in contacts was 27.3% and the case rate 10.7%. The rates were higher for Shigella flexneri than for Sh. dysenteriae. When the index cases were nought to four years old the secondary infection and case rates were higher than when index cases were older. Contacts aged nought to four years had highest attack rates. The average duration of excretion of Sh. flexneri was 4.5 and Sh. dysenteriae 2.6 days. Illness was one day longer for Sh. dysenteriae than for Sh. flexneri. Cases of shigellosis in hospital had higher rates of fever and blood in stool than those who were not in-patients. 40% of Sh. dysenteriae and 14% of Sh. flexneri were sensitive to tetracycline, 0 to 5% to streptomycin and 100% to sulphamethoxazole, trimethoprim and gentamicin. Incidence of Sh. flexneri had increased in 1980 but that of Sh. dysenteriae remained the same as in 1973 although Sh. dysenteriae type 1 appeared to be less infective in 1980 than in 1973.