Some Characteristics of Pathogenic E. Coli Strains

Abstract

SUMMARY Escherichia coli strains isolated from pericardial lesions or blood of diseased chickens (317 strains) and turkeys (181 strains) and from cloacae of apparently normal chickens (88 strains) from healthy flocks were examined serologically. Among 498 strains isolated from clinical material, 61.9% were found to belong to one or another of the three serological groups, 078:K80 (which comprised 35.6% of isolates from chickens and 25.9% from turkeys), 01:K1 and 02:K1. Only 25% of isolates from healthy chickens could be placed into any of the above PK groups. Most (92%) of the strains isolated from clinical material caused septicemia and death by oral inoculation in one-day-old chicks. All the strains were non-haemolytic; a higher proportion of strains isolated from clinical material than those from healthy chicks produced colicines; the proportion of lysogenic strains was similar in both groups of isolates. Most of the strains (99.2%) isolated from diseased birds and 75% of those from healthy chickens were found to be resistant to one or more of the anti-bacterial drugs tested. Twenty-four patterns of resistance were noted, of which multiple resistance to sulphonamide, streptomycin, oxytetracycline, chloramphenicol was the most common. The percentage of isolates from clinical material found to be resistant to sulphonamide (300 μg), oxytetracycline (50 μg), streptomycin (25 μg), chloramphenicol (50 μg), furazolidone (15 μg), ampicillin (25 μg) and neomycin (30 μg) was 90.6, 90.6, 64.8, 54.4, 45.4, 17.6 and 15.5 respectively. The corresponding figures for resistant strains from healthy chickens were 65.9, 19.3, 42.1, 2.3, 10.2, 4.5 and 0 respectively. None of the strains from healthy chickens and only four isolates from diseased birds showed resistance to nalidixic acid. The incidence of transferable drug resistance was higher among strains from clinical material than those from healthy birds. More than half of the resistant strains of the former isolates possessed the transfer factor and were able to transfer their resistance to a recipient strain in vitro .