An outbreak of Salmonella enteritidis phage type 34a infection associated with a Chinese restaurant in Suffolk, United Kingdom

Salmonella food-poisoning outbreak linked to the National School Nutrition Programme, North West province, South Africa

Background

Salmonella enterica, with more than 2500 diverse typhoidal and non-typhoidal serotypes (NTS), are foodborne bacterial pathogens of global public health concern. NTS are the most commonly reported causes of foodborne acute gastroenteritis (AGE). Contaminated food products (meat, poultry, eggs and dairy) have been reported to be a source of more than 95% NTS infections. An outbreak of food poisoning occurred among schoolchildren exposed to food provided by the government-sponsored National School Nutrition Programme (NSNP) at a local public primary day school in North West province, South Africa. An epidemiological, environmental and microbiological investigation was conducted to establish the existence and extent of the outbreak, identify the source(s) and causative agent(s) and institute appropriate control and preventive measures.

Methods

An epidemiological investigation was conducted, including a review of the clinical records of the persons exposed, laboratory testing of the pathological specimens collected, environmental testing of the food samples and food preparation areas.

Results

A total of 164 children developed clinical symptoms of AGE following ingestion of processed maize meal, beans and vegetables. Salmonella enterica serovar Heidelberg (S. Heidelberg) was the causative agent for this AGE outbreak in 92.0% of the cases. The median duration of illness was 2 days with a case fatality rate (CFR) of 0.6%. The main food product that was contaminated was samp (processed maize meal) that had been poorly stored and prepared (53.4%).

Conclusion

A timeously-initiated epidemiological, environmental and microbiological an investigation led to the conclusion that the etiologic agent of this outbreak was S. Heidelberg, and the most probable food vehicle of transmission was cooked samp served to learners within the NSNP.

Risk factors for sporadic infection with Salmonella Infantis: a matched case-control study

This matched case-control study investigated the risk factors for sporadic Salmonella Infantis infection in 263 affected children and 263 age-, gender- and neighbourhood-matched controls. Information about exposure to potential risk factors was obtained via telephone interview and evaluated by conditional logistic regression analysis. Age groups ≤ 1 year (n=77) and >1 year (n = 186) were analysed separately. Of those aged ≤ 1 year, breastfeeding was a significant protective factor against infection [matched odds ratio (mOR) 0.24, 95% confidence interval (CI) 0.10-0.59, P < 0.01]. In the older group, consumption of eggs (mOR 1.87, 95% CI 1.00-3.49, P = 0.05) was a significant risk factor and thawing chicken in water (mOR 2.55, 95% CI 0.94-6.91, P = 0.07) was borderline risk factor, while consumption of carrots (mOR 0.46, 95% CI 0.26-0.83, P < 0.01), drinking tap water (mOR 0.44, 95% CI 0.22-0.85, P = 0.02), religious lifestyle (mOR 0.40, 95% CI 0.21-0.74, P < 0.01) and having a high number of children in the household (mOR 0.72, 95% CI 0.58-0.88, P < 0.01) were significant protective factors. Consumers should avoid eating undercooked eggs and food handlers should be educated regarding proper handling and cooking of eggs. Breastfeeding should be strongly encouraged by public health authorities. The public must be educated on stringent hygiene practices, especially proper cooking of eggs to reduce infection rates.

Salmonella enterica serovar Enteritidis phage type 4 outbreak associated with eggs in a large prison, London 2009: an investigation using cohort and case/non-case study methodology

In September 2009, an outbreak of Salmonella enterica serovar Enteritidis affected 327 of 1419 inmates at a London prison. We applied a cohort design using aggregated data from the kitchen about portions of food distributed, aligned this with individual food histories from 124 cases (18 confirmed, 106 probable) and deduced the exposures of those remaining well. Results showed that prisoners eating egg cress rolls were 26 times more likely to be ill [risk ratio 25.7, 95% confidence interval (CI) 15.5-42.8, P<0.001]. In a case/non-case multivariable analysis the adjusted odds ratio for egg cress rolls was 41.1 (95% CI 10.3-249.7, P<0.001). The epidemiological investigation was strengthened by environmental and microbiological investigations. This paper outlines an approach to investigations in large complex settings where aggregate data for exposures may be available, and led to the development of guidelines for the management of future gastrointestinal outbreaks in prison settings.

Survey on the microbiological quality of Chinese food preparations

The microbiological quality of 118 samples of traditional Chinese food from restaurants and take-away establishments in the provinces of Padua, Treviso, and Venice was examined (April-July, 2008). These food items included various ready-to-eat products. The microbiological quality of the majority of these food items was acceptable; only 12% of samples had values greater than or equal to 6 log CFU/g (eight items were salads) and 19% of samples had values greater than 500 CFU fecal coliforms/g (p < 0.01 to 0.001). The Aw lower values were in sauces (0.839), but were greater than 0.95 in other food sources. No pathogens, such as Salmonella spp. or Listeria monocytogenes, were detected, but Bacillus cereus and coagulase-positive Staphylococcus were both identified. Thus, although final heating reduces the levels of microorganisms present in foods, it does not inactivate any toxins produced by such organisms.

Prevalence and antimicrobial susceptibility of salmonellae isolates from reptiles in Taiwan

Pets, including reptiles, have been shown to be a source of Salmonella infection in humans. Due to increasing popularity and variety of exotic reptiles as pets in recent years, more human clinical cases of reptile-associated Salmonella infection have been identified. However, limited information is available with regard to serotypes in different reptiles (turtles, snakes, and lizards) and antimicrobial resistance of Salmonella in pet reptiles. The current study was thus conducted to determine the prevalence of Salmonella colonization in pet reptiles. Salmonella organisms were isolated from 30.9% of 476 reptiles investigated. The isolation prevalences were 69.7% (23/33), 62.8% (27/43), and 24.3% (97/400) in snakes, lizards, and turtles, respectively. A total of 44 different Salmonella serovars were identified. Compared with S. Heron, Bredeney, Treforest, and 4,[5],12:i:-, S. Typhimurium isolates were resistant to many antimicrobials tested, and notably 61.1% of the isolates were resistant to cephalothin. The results indicated that raising reptiles as pets could be a possible source of Salmonella infection in humans, particularly zoonotic Salmonella serovars such as S. Typhimurium that may be resistant to antimicrobials.

A comparison of two PCR-based typing methods with pulsed-field gel electrophoresis in Salmonella enterica serovar Enteritidis

Two novel molecular typing methods, multiple-locus variable-number tandem repeats (VNTR) analysis (MLVA) and multiple amplification of phage loci typing (MAPLT), were compared with pulsed-field gel electrophoresis (PFGE) for the discrimination of 128 Salmonella enterica serovar Enteritidis (S. Enteritidis) isolates. Selected epidemiologically unrelated isolates represented a cross-section of phage types routinely isolated in Australia and included 28 isolates that could not be assigned a phage type. Targeting 5 previously described loci, MLVA generated 61 different profiles with a Simpson index of diversity of DI=0.968. MLVA locus STTR-5 proved to be the most diverse with 11 different alleles detected with a Nei's diversity index value of D=0.769. Using 8 MAPLT primers previously developed for S. Typhimurium produced 36 different profiles with a DI value of 0.948. By contrast, PFGE only generated 13 different pulsed-field patterns, DI=0.873. Within each phage type there was variation in the extent to which either molecular method was able to discriminate the S. Enteritidis isolates. MAPLT provided more discrimination in terms of the number of profiles and DI value for phage type 1 and the untypable strains while MLVA was more discriminatory for phage types 14var and 26. There was a general lack of concordance of either molecular assay to phage type. These results suggest that both MAPLT and MLVA have excellent potential as tools for epidemiological studies of S. Enteritidis.

Phage Therapy - Everything Old is New Again

The study of bacterial viruses (bacteriophages or phages) proved pivotal in the nascence of the disciplines of molecular biology and microbial genetics, providing important information on the central processes of the bacterial cell (DNA replication, transcription and translation) and on how DNA can be transferred from one cell to another. As a result of the pioneering genetics studies and modern genomics, it is now known that phages have contributed to the evolution of the microbial cell and to its pathogenic potential. Because of their ability to transmit genes, phages have been exploited to develop cloning vector systems. They also provide a plethora of enzymes for the modern molecular biologist. Until the introduction of antibiotics, phages were used to treat bacterial infections (with variable success). Western science is now having to re-evaluate the application of phage therapy - a therapeutic modality that never went out of vogue in Eastern Europe - because of the emergence of an alarming number of antibiotic-resistant bacteria. The present article introduces the reader to phage biology, and the benefits and pitfalls of phage therapy in humans and animals.

Outbreak of multidrug-resistant Salmonella typhimurium associated with ground beef served at a school potluck

An outbreak of gastroenteritis occurred among at least 47 persons attending a school potluck. Illness was associated with consumption of ground beef (estimated odds ratio, 16.3; 95% confidence interval, 2.2 to 338.3). Salmonella Typhimurium isolated from infected individuals and the implicated ground beef revealed identical pulsed-field gel electrophoresis patterns and was multidrug resistant. The implicated ground beef was improperly handled during the cooking process and stored above the U.S. Food and Drug Administration cooling temperature standard for >15 h before being served. This outbreak demonstrates the limitations of food safety regulations in settings where foods are prepared in the home environment for communal potlucks, bake sales, or other such gatherings held at schools, churches, or other institutions. Public health authorities should encourage school and other institutional administrators to develop policies that require dissemination of safe food preparation guidelines to prospective food handlers when such events are scheduled.