Cattle as a possible source of verocytotoxin-producingEscherichia coliO157 infections in man

Abstract

SUMMARYIn May-June 1992 cases of infection with verocytotoxin-producing (VT+) Escherichia coli 0157 in South Yorkshire could have been associated with prior consumption of beef from a local abattoir. During investigation of the abattoir, bovine rectal swabs and samples of meat and surface swabs from beef carcasses were examined for E. coli 0157, isolates of which were tested for toxigenicity, plasmid content and phage type. E. coli 0157 was isolated from 84 (4%) of 2103 bovine rectal swabs; of these 84, 78 (93%) were VT', the most common phage types being 2 and 8, the types implicated in the cluster of human cases. Positive cattle were from diverse sources within England. E. coli 0157 was isolated from 7 (30%) of 23 carcasses of rectal swab-positive cattle and from 2 (8%) of 25 carcasses of rectal swab-negative cattle. The study has shown that cattle may be a reservoir of VT+ E. coli 0157, and that contamination of carcasses during slaughter and processing may be how beef and beef products become contaminated and thereby transmit the organism to man.

Immunomagnetic separation as a sensitive method for isolatingEscherichia coliO157 from food samples

“…Strains of E. coli 0157 were isolated in a previous study [4] and were selected to include those of various phage types, H antigen types, and toxin genotypes (Table 1). Media used were buffered peptone water (CM509, Oxoid, Basingstoke) unmodified (BPW) or supplemented with vancomycin 8 mg/l, cefixime 0 05 mg/l and cefsulodin 10 mg/l (BPW-VCC [4]); nutrient broth (No.…”

“…Media used were buffered peptone water (CM509, Oxoid, Basingstoke) unmodified (BPW) or supplemented with vancomycin 8 mg/l, cefixime 0 05 mg/l and cefsulodin 10 mg/l (BPW-VCC [4]); nutrient broth (No. 2, Oxoid, Basingstoke); sorbitol MacConkey agar (CM813, Oxoid, Basingstoke) unmodified (SMAC) or supplemented with cefixime 0 05 mg/l and potassium tellurite 2-5 mg/l (CT-SMAC [8]); and plate count agar (LAB 149, Lab M, Bury).…”

“…Twelve different strains of E. coli 0157 previously isolated from bovine faeces or beef carcass meat [4] (Table 1) were each grown overnight at 37 'C in nutrient broth and c.f.u./ml were estimated as above. Dilutions of each of the broth cultures were prepared in nutrient broth and added to 10 g portions of minced beef, previously thawed and at 4°C, to give samples containing approximately 20 E. coli 0157 per 10 g; an uninoculated 10 g portion of beef was used as a control.…”

“…In N. America, beef, beef products and untreated milk have been suggested as possible sources of VTEC infection for man [1,2]. In the UK, verocytotoxinproducing (VT') E. coli 0157, the most common serogroup associated with illness in man, have been isolated from cattle [3][4][5] but the organism has been isolated only rarely from food [4,5] and its epidemiology therefore remains unclear. In view of the potential severity of infections caused by VT' E. coli 0157 it is essential that the most sensitive methods available are used in studies designed to elucidate further the reservoirs of the organism and routes of transmission of the organism to man.…”

“…Improvements to sorbitol MacConkey medium [7,8] have resulted in increased sensitivity of isolation of E. coli 0157 from faecal samples, and enrichment culture in buffered peptone water with vancomycin, cefsulodin and cefixime has been effective for isolating the organism from carcass meat samples [4]. However, the detection of E. coli 0157 present in low numbers in environmental samples is a problem due to the low sensitivity of enrichment and direct culture methods currently available.…”