E coli O157:H7 infection causes a wide spectrum of disease ranging from asymptomatic carriage to severe disease leading to death. Typical disease includes a non-bloody diarrhoea, haemorrhagic colitis, HUS and thrombotic thrombocytopaenic purpura. While the incubation period is commonly 3-4 days, it can range from one to eight days. In this article the author describes the epidemiology, the clinical features and the microbiology of the infection, whilst giving a short view of the local situation.peer-reviewe

Cuschieri, Paul

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1 7 Maltese l\1edi<:al Journal . llJlJ6: 8 (2): 7-lJ All rights reserved Escherichia coli 0157:H7 in Malta P. Cuschieri Cf}!TI'SJ!OlldI'IICI': Or P. Cuschieri, Bacteriology Laboratory, Department of Pathology, St Luke's Hospital, Gwardamangia. ......, Epidemiology E coli 0157:H7 was first recognized as a human pathogen in 1982, when it was associated with two separate outbreaks of haemorrhagic colitis in the USA 1. Both outbreaks were linked to consumption of hamburgers. Since then, E coli 0157:H7 has emerged as a leading food-borne pathogen, particularly in North America 2 where its household name (,hamburger disease') underlines the important association of ground beef with the condition. Of particular public health concern are the serious c<?mplicarions of infection, namely haemorrhagic colitis and the haemolytic uraemic syndrome (HUS); the high frequency of secondary person-to-person transmission; the very low (possibly less than 100 organisms) infecting dose 3.4 and the established reservoir of the pathogen in cattle, In one review, I % of healthy cattle were intestinally colonised with E coli 0157 :H7 5. Ground beef is the most common vehicle for E coli 0157 :H7 transmission in investigated outbreaks in the USA 6. Infection through contaminated beef can occur if it is insufficiently cooked (internal temperature less than 68 0 C, or visibly uncooked with oozing blood inside), or if such meat contaminates ready-to-eat food. Beef may be contaminated during slaughter, and the process of grinding beef may transfer pathogens from the surface to the deep layers of meat. Since multiple carcases may be involved in one ground beef production, a small proportion of infected .animals in the 'pool' can cause widespread contamination. Other less common vehicles of infection described include vegetables, unpasteurized cow's milk, unpasteurized apple cider, yoghurt, mayonnaise and unchlorinated drinking water. Swimming in contaminated lake water and contact with raw cow manure have also been implicated 7, Person-to-person transmission has been an important mode of spread in day care centres 4,8, It was responsible for an outbreak in ' a nursing home in Canada 9, and was the mode of transmission to staff in an outbreak in institutions for the mentally subnormal 10 . A nurse caring for a child with HUS was infected by direct contact with the patient 11. Risk factors for infection include extremes of age 5, antimicrobial therapy administered early 8,'.1 and previous gastrectomy 8, Occupational exposure to cattle, to minced beef and to microbiological specimens and cultures in laboratories are also known hazards 12.13,14.15 . Clinical features E coli 0157:H7 infection causes a wide spectrum of disease ranging from asymptomatic carriage to severe disease leading to death. Typical disease includes a non­bloody diarrhoea, haemorrhagic colitis, HUS and thrombotic thrombocytopaenic purpura 16 . While the incubation period is commonly 3-4 days, it can range from one to eight days 17,18,19. Infections caused by E coli 0157:H7 have been reported in many countries, and in many of them incidence appears to be increasing 20. The recent large outbreak of EHEC in Sakai City, Japan generated wide press interest: between 12 July and 16 August 1996, 6561 persons were affected, mostly schoolchildren (96%). Ninety-two developed HUS and one died . Meanwhile, by 13 August , more than 9,200 individuals with EHEC were reported throughout the country , with nine associated deaths 21. Microbiology E coli 0157:H7 belongs to the enterohaemorrhagic (EHEC) subgroup. It produces two distinct lysogenic, bacteriophage-encoded toxins that inhibit protein­synthesis and are active against cultures of Vero and HeLa cells. These Shiga-like toxins have been called verotoxin I (VTI) and verotoxin 2 (VT2). Isolates of human origin most commonly produce either VT2 or both VTI and VT2. Over 62 different phage types have been recognised. Other less common EHEC serotypes causing disease in man include 026:H 11, 0111 :H8 and 0104:H21. The detection of E coli 0157:H7 in stools by using an appropriate selective and differential medium is a relatively straightforward and inexpensive procedure . Moreover, the labour involved in the review of plates is minimal. The toxin/s can also be detected directly from the stools by enzyme-linked immunosorbent assay techniq ues . Other laboratory diagnostic strategies are also available. Irrespective of the method used, early collection of faecal specimens for detecting E coli 0157 :H7 is imperative. A positive culture is to be expected in 100% specimens collected within two days of onset of symptoms: this proportion drops to 33 % if the sample is taken seven days or more from onset 22. Antibiotic therapy of E coli 0157 :H7 infection is not usually recommended since it is generally ineffective and may even result in a worsening of the condition due to further release of toxin from killed intracolonic bacteria23 . Subinhibitory concentrations of cotrim oxazole 9 Escherichia coli 0157: H7 in Malta -have been shown to increase the production of Shiga-like toxin in vitro 24. The prophylactic use of antibiotics is contraindicated; indeed this has been identified as a risk factor for the development of the condition 10.12 Orally administered toxin-binding resins and antitoxin gIven intravenously 25 seem to hold more promise. The local situation . Plans to introduce laboratory diagnostic facilities for E coli 0157:H7 at St Luke's Hospital were made in 1993, and the service was eventually introduced in September 1994. Thanks to the introduction of this new diagnostic service, SLH Bacteriology Laboratory joined the European VTEC Club in 1994. The Club promotes communication amongst various groups throughout Europe studying EHEC infection. It is currently the policy to screen routinely all stool specimens submitted for culture. All isolates of E coli 0157:H7 are referred to the Public Health Laboratory in Valletta for phage typing and toxigenicity tests. So far, two patients have been diagnosed with E coli 0157:H7 infection, while a third clinically suggestive case could not be confil111ed bacteriologically, possibly due to late submission of the stool specimen. The first two cases are the subject of an article in this issue 26. Acknowledgements To all un mentioned staff at SLH Bacteriology Laboratory, the Department of Public Health and Public Heal th Laboratory. References I. 	 Riley LW, Remis RS, Helgerson SD et al. Haemorrhagic colitis associated with a rare Escherichia serotype. New Engl J Med 1982; 308:681-685. 2. 	 Borg T. A study on Escherichia coli 0157:H7 in the Maltese Islands. Reproduced from various sources. Univ of Malta. 1996: 49. 3. 	 Ratnam S, March SB, Spiague WD, Severs D, Sullivan RM. Are humans a source of E coli 0157:H7, the agent of haemorrhagic colitis? (letter). New Engl J Med 1986; 315:1612-1613. 4. 	 Spika JS, Parsons JE, Nordenberg D, Wells JG, Gunn RA, Blake PA. Haemolytic uraemic syndrome and diarrhoea associated with Escherichia coli 0157:H7 in a day-care centre. J ofPed 1986; 109:287-291. 5. 	 Griffin PM, Tauxe RV. The epidemiology of infections caused by E coli 0157: H7, other enterohaemorrhagic E coli and the associated haemolytic uraemic syndrome. Epidemiol Rev 1991; 13 :60-98. 6. 	 Cannon M, Thomas H, Sellers W et al. Outbreak of E coli 0157:H7 Infection - Georgia and Tennessee, June 1995. MMWRI996; 45(12):250-51. 7. 	 Tarr PI. E coli OI57:H7: Clinical, diagnostic and epidemiological aspects of human clinical infectious diseases. 1985; 20:6. 8. 	 Belongia EA, Osterholm MT, Soler JT, Ammend DA, Braun JE, MacDonald KL. Transmission of E coli 0157:H7 in Minnesota child day-care facilities. JAMA 1993; 269:883-888. 9. 	 Carter AO, Borczk AA, Carlson JAK et al. A severe outbreak of E coli 0157: H7 - associated haemorrhagic colitis in a nursing home. New Engl J Med 1987; 317:1496-1500. 10. 	 Pavia AT. Nichols CR, Green DP et al. Haemolytic uraemic syndrome during an outbreak of E coli 0157:H7 infections in institutions for mentally retarded persons. Clinical and epidemiological observations. J of Paed 1990; 116:544-55 I. 11. 	 Kannali MA, Arbus GS, Petric M, Patrick ML, Roscoe M, Shaw J. Hospital acquired E coli 0157:H7 associated with haemolytic uraemic syndrome in a nurse (letter) . Lancet 1988; 1 :526. 12. 	 Ostroff SM, Kobayashi JM, Lewis JH. Infections WIth E coli 0157:H7 in Washington State: the first year of state­wide disease surveillance. JAMA 1989; 262:355-359. 13. 	 Renwick SA, Wilson 18, Clarke RC et al. Evidence of direct transmission of E coli 0157:H7 infection between calves and a human. J of Infec Dis 1993; 168:792-793. 14. 	 Booth L, Rowe B. Possible occupational aquisition of Escherichia coli 0157 infection. Lancet 1993; 342: 1298­1299. 15. 	 Burnens AP, Zbinden R, Kaempf L, Heinzer I, Nicolet J. A case of laboratory acquired infection with Escherichia coli 0157:H7. Zentralb Baktereol. 1993; 279:512-517. 16. 	 Griffin PM, Ostroff SM, Tauxe RV et al. Illnesses associated with E coli 0157:H7 infections: a broad clinical spectrum. Annals of Int Med 1988; 109:705-712. 17. 	 Ostroff SM, Griffin PM, Tauxe RV et al. A state-wide outbreak of E coli 0157:H7 infections in Washington State. Am J of Epidemiol 1990; 132:239-247. 18. 	 Ryan CA, Tauxe RV, Hosek GW et al. E coli 0157:H7 diarrhoea in a nursing home: clinical, epidemiological and pathological findings. J of Infect Dis 1986; 154:631­638. 19. 	 Salmon RL, Farell ID, Hutchison JGP et al. A christening party outbreak of haemorrhagic colitis and HUS associated with E coli OI57:H7. Epidemiol & Infect 1989; 103:249-254. 20. 	 Report of WHO Working Group Meeting on Shiga-Like Toxin Producing Escherichia coli (SL TEC) with emphasis of Zoonotic Aspects. Bergamo. Italy. I July 1994. WHO 1995. 21. 	 WHO Surveillance Programme for Control of Foodborne Infections and Intoxications. Large EHEC outbreak in Japan. Newsletter No 49/50. Sept 1996. 22. 	 Tarr PI, Neill NA, Clausen CR, Watkens SL, Christie DL, Hickman RO. Escherichia coli 0157:H7 and the haemolytic uraemic syndrome: inlportance of early cultures in establishing the aetiology. J of Infect Dis 1990; 162:553-556. 23. 	 Waltenspiel IN, Ashkenazi S, Morrow AL, Clearly TG. Effect of subinhibitory concentration of antibodies on extracellular Shiga-like toxin I. Infection 1992; 20:25­29. 24. 	 Karch H, Stockbine NA and O'Brien AD. Growth of Escherichia coli 0157:H7 in the presence of trimethoprim-sulphamethoxazole facilitates detection of Shiga-like toxin producing strains by colony blot assay. FEMS Microbiol Lett 1986; 35:141-145. 25. 	 Griffin PM. Escherichia coli 0157:H7 and other enterohaemorrhagic Escherichia coli. In Blaser MJ, Smith PD, Raudin 11, Greenberg HB and Guerrant RL (eds). Infections of the gastro-intestinal tract. New York: Rowen Press. p739-76I. 26. 	 Cuschieri P, Falzon D, Borg T, Stokes N. Escherichia coli 0157:H7 in Malta for the first time. MMJ 1996; 8 (2): 33-34. The copyright of this article belongs to the Editorial Board of the Malta Medical Journal. The Malta Medical Journal’s rights in respect of this work are as defined by the Copyright Act (Chapter 415) of the Laws of Malta or as modified by any successive legislation. Users may access this full-text article and can make use of the information contained in accordance with the Copyright Act provided that the author must be properly acknowledged.  Further distribution or reproduction in any format is prohibited without the prior permission of the copyright holder. This article has been reproduced with the authorization of the editor of the Malta Medical Journal (Ref. No 000001)  

Escherichia coli O157:H7 in Malta

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Escherichia coli O157:H7 in Malta

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