CITATION: Horwitz, B. M., Finlayson, M. H. & Brede, H. D. 1974. Prevention of food poisoning in hospital patients. South African Medical Journal, 48(26):1109-1111.The original publication is available at http://www.samj.org.zaBacteriological investigations of raw and cooked foods and of food handlers in abattoirs, food factories and hospital kitchens show that they are potential sources of food poisoning organisms. The use of reheated (reconstituted) frozen foods is recommended as an ideal means of preventing food poisoning among hospital patients.http://archive.samj.org.za/index.php?path=%2F1974+VOL+XLVIII+Jan-Jun%2FArticles%2F06+JunePublisher’s versio

Brede, H. D.

Finlayson, M. H.

Horwitz, B. M.

Stellenbosch University SUNScholar Repository

1 Junie 1974 S.-A. MEDIESE TYDSKRIF 1109Prevention of Food Poisoning in Hospital PatientsB. M. HORWITZ, M. H. FINLAYSON, H. D. BREDESUMMARYBacteriological investigations of raw and cooked foodsand of food handlers in abattoirs, food factories andhospital kitchens show that they are potential sources offood poisoning organisms. The use of reheated (recon-stituted) frozen foods is recommended as an ideal meansof preventing food poisoning among hospital patients.S. Afr. Med. J., 48, 1109 (1974).A number of food poisoning outbreaks in hospitals havebeen recorded in South Africa:-' In order to prevent suchoutbreaks in the Tygerberg Hospital a comprehensive in-vestigation into all possible sources of food poisoning hasbeen carried out. The investigation covered the bacterio-logical testing of all raw food supplied to the hospital, thesame food after normal cooking, and after subsequentfreezing and 'reconstitution' by reheating. In addition, testswere carried out on abattoir, food factory and kitchenpersonnel.Bacteriological testing was confined to identifying thepathogenic bacteria present in each sample. Only th0seorganisms recognised as being the cause of food poisoningare referred to.MATERIALS AND METHODSRaw FoodsThe types of food, the number of specimens examinedand the organisms isolated, are shown in Table I.The heaviest contamination occurred in the beef carcassesand beef portions.Department of -Medical Microbiology, University of Stellen-bosch and Tygerberg Hospital, Tiervlei, CPB. M. HORWlTZM. H. FINLAYSONH.D.BREDEDate received: 14 January 1974.Beef carcasses: 5,8% of specimens from beef carcassesgave a growth of Salmonella, and 6,2 0 0 Cl. welchii.The Salmonella strains were: S. muenchell 2; S. reading2; S. sandiego I; S. johannesburg 4; Salmonella group 0I; Salmonella group G 1; and Salmonella group H 1.Beef portions: These showed a high degree of infectionwith food poisoning organisms. The possibility of themeat becoming infected with these - organisms duringtransport from the abattoir, subsequent handling, andcutting up in the butcher's shop must be considered.A single inspection of the premises of one of thishospital's meat contractors, where swabs were taken fromequipment, etc., showed the presence of Cl. welchii andpathogenic E. coli on the butcher's block, bandsaws, andthe overalls and hands; Cl. welchii on the scale. andStaph. ai/reus and pathogenic E. coli on the knife.In addition, a survey of the corned beef pickling barre;sin the Divisional Council area of the Cape revealed thatof 119 samples taken, 3 were positive for Salmonella;10 for Cl. welchii; and 3 for Sraph. aureus. The extent ofthe contamination of other raw foods with food poisoningorganisms is shown in Table 1.Food Handlers in the Abattoir, Food Factory andHospital KitchensStool samples and swabs from throats, hands andclothing were examined. The findings are shown in Tablen. It appears very likely that some of the organisms foundon the meat supplied were derived from human sources.From Table TI it is evident that there is a dailyintroduction via raw food into the hospital kitchens ofpathogenic organisms which are capable of giving rise tofood poisoning.Thorough heating for a sufficient length of time shoulddestroy all vegetative forms of bacteria even in heavily in-fected food. Samples of food cultured immediately aftercooking showed, in some instances, that either the tempera-ture reached, or the length of time the food was heated,was insufficient to destroy all pathogenic organisms present.TAaLE I. ORGANISMS FOUND IN RAW FOODSIII.EQ) U> C Q)U> C C Q) '0 ClU> alal 0 0 .:£ Q)- ~ ~:e t:: u - ~ m u U> ~Q) Q) 0 C :JQ)'"Q) 0 :J .J::. Q) Q)'"en!Xl u !Xl Cl.. ~ 0 !Xl Cl.. ~ E Cl) u:::No. of specimens 207 197 64 102 62 48 16 22 60Salmonella 12 13 5 1 1 1Cl. welchii 13 23 2 2 1Pathogenic E. coli 23 2 6 3 1Staph. aureus 3 3 2 4 2U>~.0alQ)ClQ)>50391110 S.A. MEDICAL JOURNAL 1 June 1974TABLE 11. ORGANISMS FOUND IN ABATTOIR, FOODFACTORY AND HOSPITAL KITCHEN WORKERSAlternatively, the cooked food may have become infectedby a handler in the kitchen directly or indirectlythrough infected utensils. The presence of pathogenicbacteria or their toxins has been borne out by a numberof small outbreaks of food poisoning (6 in all) amongthis hospital's staff during the period 1970 - 1973. Threeof these outbreaks were due to Staph. aureus and threepossibly to Cl. welchii.The results of the bacteriological tests carried out onsamples of the various cooked foods are shown IIITable Ill.From these results it would appear that Staph. aurellS,Cl. welchii and E. coli are the organisms most likely tocause food poisoning. While Staph. aureus is killed byheating for 12 minutes at 65°C4 and can survive cookingin the interior of a large amount of food where thistemperature was not reached, its enterotoxins are destroyedonly after 30 minutes' heating at 100°C. The survival ofNose Stools andswabs rectal swabsNo. of specimensStaph. aureusE. coli serotype-{)142/B-026/B6-0125/B15-0112/Bll-086/Bl1-0112/K66-0124/K72-0114/B-086/B7Salmonella group ESalmonella group JSalmonella group CSalmonella group ZSalmonella typhimuriumShigella flexneriShigella sonneiThroatswabs5781124971415641141111113173132Cl. welchii through its heat-resistant spores, is readilyunderstood. The last 3 small outbreaks among staff atthis hospital were possibly due to this organism. In onlyone case was left-over food available for investigation, andCl. welchii was isolated from the meat and the gravy.In the other two outbreaks no left-over food or useddishes were available, but the symptoms suggest contami-nation with these organisms, or their toxins. Entero-pathogenic E. coli have long been recognised as a causeof gastro-enteritis, particularly in infants.MEmODS OF PREVENTIONIn 1972 an experimental kitchen for the preparation offrozen foods was introduced at Conradie Hospital, Pine-lands, to investigate its operation under South Africanconditions. The bacteriological investigations of boththe raw and cooked foods were carried out by us. Most ofthe results obtained are incorporated in the tables.The frozen food was held long enough for these investi-gations to be completed before the food was issued.Basically, the system employed is that immediatelyafter cooking the food is placed in disposable coveredaluminium trays, and when cool, frozen in liquid nitrogento approximately -25°C and then stored in a freezer.After freezing, sample trays of the food are heated ininfra-red ray ovens to 80°C for from 20 minutes to 1 hour.depending on the type of food and the size of the container.Samples are then taken for bacteriological culture. Ifsatisfactory, the batch of food is marked as being suitablefor issue to the hospital wards. If pathogenic organismsare found, further bacteriological tests are carried out.lt still unsatisfactory, the batch is condemned. Food forthe wards is issued frozen in trays (4 - 10 portions per tray)from the central kitchen to accessory ward kitchens.Here food is heated in infra-red ray ovens to 80°C andthen served onto plates. All left-overs are discarded.In addition to the above, the following precautions aretaken:1. All food handlers (kitchen staff, and ward-kitchenstaff) are tested regularly every 3 months-both throatswabs and faeces samples are taken.TABLE Ill. ORGANISMS FOUND IN COOKED FOODSNo. of specimensStaph. aureusE. coli group IE. coli serotype 0 127E. coli serotype 0 55E. coli serotype 0 114/BE. coli serotype 0 128/812Sh. boydliSalmonella group 8Salmonella group CCl. welchiien~ cC .0 Clc <Il co e c.....0 ~ 3: "t co Il:l.... ~ 0.c () () "<Il :; .... :c 1Il Ol c "1Il 0 en U5 1Il co :::Jco L Cl- U LL > L L Cl-368 114 114 206 334 . 216 346 108 192 379 1 2 4 2 7 6 1 12 1 1 2 1 21 2 1 24t4I Junie 1974 S.-A. MEDIESE TYDSKRIF llIl2. The siaff are lectured on food hygiene and theabsolute necessiiy for the clean handling of food.3. The central kitchen used for ihe produciion offrozen foods and the ward kitchens for ihe feeding ofpatienis are supervised by qualified dietitians who areresponsible for the enforcement of hygienic handling ofall food.4. Use is made of the agar syringe modification' of theTen Cate agar sausage technique, to check on the efficacyof cleaning of all utensils and working surfaces and asa means of demonstrating to the staff the absolutenecessiiy of good hygiene.5. Random samples of raw foods and of all cookedfoods are taken daily for bacteriological control.DISCUSSIONThere is no doubt that the feeding of heated bacterio-logically satisfactory frozen foods immediately afterheating, is a practical and effective means of preventingfood poisoning. It allows for sufficient time to carry outall the bacteriological tests before use. As the frozen foodis heated for a short time to a high temperature (80°C),and then fed almost immediately, very little time is givenfor multiplication of any pathogenic coniaminants. Thusthe danger from the human carrier is virtually eliminated.It is a rule in this hospital that all left-avers arediscarded.The success of this method has so far been borne outin practice. Since its institution no outbreaks of foodpoisoning have occurred in the wards. In those sectionsof the hospital using food prepared by conventional15--------methods of cooking and direct feeding after cooking, anumber of small food-poisoning outbreaks have occurred.In the two kitchens supplying conventional food, theprecautions taken are the same as those described forthe central kitchen, except that the food is not frozen andthen reheated before use. The possibility of infectionof food by the human carrier, either directly or indirectly,and the multiplication of the contaminating organismswhile the food is kept warm during serving, is thus noteliminated. Unlike the wards, where each container holdsonly 4 - 10 portions, the containers here are large andhold approximately 20 - 40 portions. When there is a delaysome of the food may be held for more than an hour.No containers are re-used until thoroughly cleansed, butwith the type of labour available this system could breakdown. Every attempt is made while serving to keep thefood at a high temperature (approximately 800C), butconstant supervision is necessary to enforce this.The major objection to the use of the frozen foodsystem is that it is more expensive due to the costs addedby rapid freezing, freezing rooms, reheating, and disposablecontainers' The cost of hospitalisation of a patient inthis hospital is estimated at ± R30jday. The additionalperiod in hospital following an attack of food poisoningis usually about 2 days. In our opinion the extra costof the frozen food system is more ihan offset by theelimination of food poisoning among patients.REFERE CESI. Le Riche, H. and Dunsian, T. (1953): S. Afr. Med. J., 27, !l02.2. Finlayson, M. H. (1943): Ibid., 17, 173.3. Cooper, E. D. (1959): Ibid., 33, 542. .4. Grady, G. F. and Keusch, G. T. (1971): New Engl. J. Med., 285, 831.5. Millcross, 1. (1973): Royal Society of Health Journal, 93. 133.6. Horwitz, B. M. (1974): S. Afr. Med. J., 48, 271.

Prevention of food poisoning in hospital patients

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Prevention of food poisoning in hospital patients

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