An outbreak of multidrug-resistant Salmonella enterica subsp. enterica serotype Typhimurium, DT104L linked to dried anchovy in Singapore.

Multidrug-resistant Salmonella enterica subsp. enterica serotype Typhimurium DT104L was first reported in Singapore from mid-July to mid-October 2000. Salmonella strains isolated from clinical laboratories were submitted to a reference laboratory for serotyping, phage-typing and pulsed-field gel electrophoresis (PFGE) using XbaI restriction endonuclease. An epidemiological investigation was conducted to determine the source of infection and mode of transmission using a structured questionnaire. A total of 33 cases involving mainly infants and toddlers were detected in the 3-month long outbreak. The outbreak strain was of the R-type ACGSTSu, i.e. resistant to ampicillin, chloramphenicol, gentamicin, streptomycin, tetracycline and sulphonamide. PFGE showed all isolates had an indistinguishable pattern, indicating a common source of infection. Consumption of imported dried anchovy was found to be the vehicle of transmission after adjusting for all confounding variables in the case-control study using stepwise logistic regression (OR 25.6; 95% CI 3.9-167.9; P = 0.001). Imported dried seafood should be properly processed, packed, labelled, and thoroughly cooked to prevent transmission of multidrug-resistant S. Typhimurium.

Blood lead levels of a population group not occupationally exposed to lead in Singapore.

A survey was conducted between 1995 and 1997 to assess the impact of introduction of unleaded petrol and other public health measures on the blood lead level of the population. The geometric mean blood lead level of 269 government employees as determined by graphite furnace atomic absorption spectroscopy, was 66.0 microg/l, much lower than that recorded before introduction of lead-free petrol. Using multiple regression analysis, factors significantly associated with blood lead levels were: exposure to traffic, age (>50 years) and active smoking. Passive smoking, exposure to recent paint work, consumption of alcohol and traditional medicine were found not to be significantly associated with the blood lead level.

A shipyard outbreak of salmonellosis traced to contaminated fruits and vegetables.

A large outbreak of food poisoning occurred in September 1996 and involved at least 116 workers at a shipyard in Jurong. Salmonella weltevreden was isolated from the stool specimens of 24 hospitalised cases and three food handlers, giving a total of 27 bacteriologically confirmed cases (25 symptomatic and two asymptomatic) in this outbreak. Based on a case-control analysis, a number of food items consumed on 23 and 24 September 1996 were implicated in the outbreak, viz. a vegetable dish (P < 0.01), watermelon juice (P < 0.01) and cut watermelon (P < 0.001), papaya (P < 0.001) and pineapple (P < 0.05). The median incubation period was 38 hours and the median duration of illness was two days. Four samples of cut fruits obtained from a food stall at the canteen were found to be positive for Salmonella weltevreden. (The antibiogram of all the strains isolated from food samples and stool cultures was similar, consistent with a common source of infection.) Extensive investigation suggested that contamination may have occurred through unauthorised use of industrial water for washing the fresh produce. Early recognition of the outbreak and prompt implementation of control measures prevented further spread of infection.

A nationwide outbreak of coconut-associated paratyphoid A fever in Singapore.

A large outbreak of 167 cases of paratyphoid A was reported in Singapore during the period 15 February to 4 May 1996. Cases were distributed all over the country and no specific food establishment was implicated. The attack rate was highest among the Indian ethnic group between the ages of 25 and 34 years. A case-control study showed that consumption of a variety of food items in which imported deshelled coconut was used as an ingredient was statistically significantly associated with the illness (P < 0.001). As soon as the vehicle of transmission was suspected, the import of deshelled coconut was banned. No further cases were reported four weeks after the ban. The outbreak highlighted the need to maintain a high degree of vigilance against the introduction of infectious diseases through imported food.