Emergence of salmonella enteritidis in the Caribbean: case control study in Trinidad and Tobago

OBJECTIVE: To determine the aetiology, sources and risk factors of Salmonella enteritidis (SE) infections in Trinidad and Tobago. METHODS: A prospective case control study of 46 cases and 92 age-and neighbourhood-matched controls was conducted between March 1998 and May 1999 to explore hypothesized risk factors for SE infections. A written questionnaire was administered through face-to-face interviews. Standard culture and serological laboratory methods were used to confirm SE isolates from food and clinical samples. Data were analyzed using Epi Info version 6.04 software. RESULTS: SE infection was associated with the consumption of shell eggs, particularly raw or undercooked eggs. There was a positive association between SE infection and the number of eggs consumed (p<0.001). Persons with SE infection were less likely than well controls to purchase refrigerated eggs and to refrigerate their eggs at home (p<0.001). SE isolates from 30/34 (88 percent) patients and from 9 implicated egg or egg-containing food samples were phage type (PT) 4. Thirty (65 percent) of 46 patients were hospitalised and 2 died. CONCLUSION: SE infection are sporadic and seasonal and are associated with eating raw-egg foods such as homemade eggnog and ice cream, cake batter and egg-containing beverages. PT 4 is the dominant phage type. Public health education programmes on the risks of eating raw or undercooked eggs, egg-traceback studies and on-farm testing of flocks for SE are needed to reduce the incidence of this infection.(AU)

Salmonellosis in Trinidad: evidence of transovarian transmission of salmonella in farm eggs

The aim of this study was to determine whether the contents of farm eggs in Trinidad are contaminated with Salmonella and if transovarian transmission occurs. 750 fresh eggs from 10 farms supplying 75 percent of the country's eggs were cultured for Salmonella. Salmonella was found on the egg shells' surface from all farms, and in the egg contents from three farms. Isolates were obtained from the cultures of the contents and shells of nine (1.2 percent) and 35 (4.66 percent) eggs, respectively (p<0.005). Serotypes found in the contents were S. enteritidis (0.8 percent; deduced to be contaminated by transovarian transmission) were S. typhimurium (0.4 percent); those isolated from the shells (contaminated by faecal transmission) were S. typhimurium (3.06 percent), S. enteritidis (0.67 percent), S. ohio (0.27 percent), S. cerro (0.27 percent) S. infantis (0.27 percent) and S. heidelberg (0.13 percent). This study provides the first evidence for Salmonella and more, importantly, S. enteritidis, in eggs in Trinidad. This is of major public health significance because S. enteritidis infected eggs appear normal and the organism is difficult to detect and control. The consumption of these eggs may increase the risk of Salmonella infection. Food safety practices, particularly the thorough cooking (>70 degree census) of all egg dishes and the refrigeration (<10 degree census) of shell eggs and egg dishes, are recommended.(AU)

Salmonellosis in Trinidad II: evidence for transovarian transmission in farm eggs - abstract

The aim of this study was to determine whether farm eggs (contents and shells) in Trinidad are contaminated with Salmonella and to demonstrate if transovarian transmission occurs in these eggs. A total of 750 fresh eggs from 10 farms were cultured for Salmonella. The United States FDA Bacteriological Analytical Manual's Official Standard culture methods for Salmonella were used. Salmonella and S. enteritidis were detected in 9 of the 750 pooled eggshells' cultures, which has not been previously demonstrated in Trinidad. The spectrum of Salmonella serotypes isolated from the pooled egg contents were S. enteritidis (0.8 percent) and S. typhimurium (0.4 percent), and that isolated from the pooled eggshells was S. typhimurium (3.06 percent), S. enteritidis (0.67 percent), S. ohio, S. cerro, S. infantis (0.27 percent each) and S. heidelberg (0.13 percent). Salmonella was found in the egg contents of only three farms, but on the eggshells' surface from all 10 farms. This variation in isolation rate was found to be related to farm management and quality control practices. The contamination of the egg contents with S. enteritidis was deduced to be by the transovarian transmission process whilst S. typhimurium contamination of the egg contents was through faecal transmission. This study provides the first hard evidence for Salmonella and more importantly, S. enteritidis contamination of eggs, and demonstated transovarian transmission of S. enteritidis in eggs. This is of major public health significance since such eggs can be of grade A quality and widely consumed by unsuspecting consumers, resulting in salmonellosis. (AU)