Gouws, Anne-Marie

Hoyland, Greta

Keddy, Karen Helena

Smith, Anthony Marius

Sooka, Arvinda

South African Medical Journal (SAMJ)

1272Outbreaks of food-borne disease – a common occurrence but rarely reportedAnthony M Smith, Anne-Marie Gouws, Greta Hoyland, Arvinda Sooka, Karen H Keddy, for the Group for Enteric, Respiratory and Meningeal Disease Surveillance in South Africa (GERMS-SA)To the Editor: Salmonella infections are among the most prevalent recognised communicable diseases caused by bacteria, and a major cause of food poisoning throughout the world. The Enteric Diseases Reference Unit (EDRU) of the National Institute for Communicable Diseases (NICD) is a reference centre in South Africa (SA) for various enteric pathogens including Salmonella, and participates in national laboratory-based surveillance for Salmonella. Isolates are voluntarily submitted to the EDRU from ~120 clinical microbiology laboratories covering all provinces across the country. We report an outbreak of food-borne disease among schoolteachers at Rob Ferreira High School in White River, Mpumalanga, in December 2006, which occurred after eating food prepared by the school kitchen. The causative agent was identified as S. enterica serotype Virchow (Salmonella Virchow). Twenty-two bacterial isolates were obtained for analysis following culture from patients’ rectal swabs. All isolates were susceptible to ampicillin, augmentin, trimethoprim, sulfamethoxazole, chloramphenicol, streptomycin, tetracycline, kanamycin, imipenem, nalidixic acid, ciprofloxacin, ceftriaxone and ceftazidime. Pulsed-field gel electrophoresis (PFGE) analysis of XbaI digested genomic DNA of bacteria revealed an identical pattern for all 22 outbreak strains which, together with identical antimicrobial susceptibility profiles for all isolates, determined that the outbreak was caused by a single strain of bacterium.Isolates of S. enterica serotype Virchow is an uncommon serotype in the SA human population, accounting for only 25 of the 4 966 Salmonella isolates received by the EDRU from 2003 to 2005. In 2006, the EDRU received only 8 Salmonella Virchow isolates, on top of the 22 isolates associated with the outbreak of food-borne disease. To the best of our knowledge, no published data have previously reported food-borne disease outbreaks associated with Salmonella Virchow in SA. However, there have been several reports worldwide.1-4 Contaminated semi-dried tomatoes and fresh garlic were found associated with Salmonella Virchow food poisoning, the patients presenting with bloody diarrhoea and in some cases with bacteraemia.4 Given the burden of HIV disease in SA, this is highly significant as Salmonella causes invasive disease in this group of individuals. Unfortunately, with regard to this report, we have no information of the meal prepared by the school kitchen and no particular foodstuff could be implicated since all the food was eaten and none remained for analysis.Outbreaks of food-borne disease in humans are common in SA, but rarely reported. Any food poisoning incident involving ≥2 people is notifiable and should be reported to the relevant health authorities. However, as is the case in most countries worldwide, food-borne disease is markedly underreported. Outbreaks of food-borne disease should be thoroughly investigated. Clinical specimens and food samples should be taken and investigated. Patients and unaffected individuals should be questioned as to what was eaten, to highlight the foodstuffs that may have been responsible for the outbreak.5 South Africa will host the Soccer World Cup in 2010, and medical practitioners must be aware of public health risks, including food-borne disease. Improved understanding of the burden of illness due to food-borne infections, the aetiological agents and the implicated foodstuffs will assist in preventing future outbreaks.This work was financially supported by the National Health Laboratory Service. We thank the Epidemiology Unit of the NICD for notifying us of this outbreak.References1.  Weill FX, Lailler R, Praud K, et al. Emergence of extended-spectrum-beta-lactamase (CTX-M-9)-producing multiresistant strains of Salmonella enterica serotype Virchow in poultry and humans in France. J Clin Microbiol 2004; 42(12): 5767-5773.2.  Vaeteewootacharn K, Sutra S, Vaeteewootacharn S, et al. Salmonellosis and the food chain in Khon Kaen, northeastern Thailand. Southeast Asian J Trop Med Public Health 2005; 36(1): 123-129.3.  Singh BR, Singh M, Singh P, Babu N, Chandra M, Agarwal RK. Prevalence of multidrug-resistant Salmonella on ready-to-eat betel leaves (Paan) and in water used for soaking betel leaves in North Indian cities. J Food Prot 2006; 69(2): 288-292.4.  Bennett CM, Dalton C, Beers-Deeble M, et al. Fresh garlic: a possible vehicle for Salmonella Virchow. Epidemiol Infect 2003; 131(3): 1041-1048.5.  Centers for Disease Control and Prevention (CDC). Foodborne Illness - 25 October 2005. http://www.cdc.gov/ncidod/dbmd/diseaseinfo/foodborneinfections_g.htm#howinvestigated (last accessed 31 May 2007).Enteric Diseases Reference Unit, National Institute for Communicable Diseases and University of the Witwatersrand, Private Bag X4, Sandringham, JohannesburgKaren H Keddy, MB BCh, BSc (Med), FCPath (SA), MMed, DTM&HAnthony M Smith, BSc Hons, PhDArvinda Sooka, National Higher Diploma (Medical Technology), MScDepartments of Health and Social Services, Nelspruit, MpumalangaAnne-Marie Gouws, National Diploma (Nursing)National Health Laboratory Service, Rob Ferreira Hospital, Nelspruit, MpumalangaGreta Hoyland, National Diploma (Medical Technology)SCIENTIFIC LETTERSCorresponding author: A Smith (anthonys@nicd.ac.za)December 2007, Vol. 97, No. 12  SAMJPg 1272.indd   1272 11/27/07   3:47:36 PM

Outbreaks of food-borne disease: A common occurrence but rarely reported

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Outbreaks of food-borne disease: A common occurrence but rarely reported

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