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Journal of Clinical Microbiology, 11 1997, 2953-2957, Vol 35, No. 11
JE Blanco, M Blanco, A Mora and J Blanco
Since the mechanism of virulence of Escherichia coli strains pathogenic to
birds is not fully understood, the prevalence of toxic factors produced by
E. coli strains pathogenic to other animals was investigated. A total of
625 E. coli strains isolated from visceral organs of chickens with
colisepticemia and from feces of healthy chickens in Spain were tested for
production of enterotoxins (heat labile [LT] and heat stable [STa]),
verotoxins (VT1, VT2, and VT2v), cytotoxic necrotizing factors (CNF1 and
CNF2), alpha-hemolysin (Hly), enterohemolysin (EntHly), colicin V (Col V)
and other types of colicins, and necrotic and lethal activities. Only 45
(7%) of avian E. coli strains were toxigenic: 20 strains produced a
cytotoxic response in HeLa but not in Vero cells, indicating the production
of a cytotoxin not related to the VTs; 16 were EntHly+; 5 produced a new
cytotonic product that causes the appearance of whitish vacuola in Vero and
HeLa cells; 3 synthesized soluble factors that cause lethal activity in
mice; and 1 elaborated LT. None of 625 avian E. coli strains was positive
for production of VTs or CNFs. In contrast, colicinogenicity occurred in
335 (73%) of the 458 septicemic strains and 97 (58%) of 167 fecal isolates
(P < 0.01), and this property was correlated with in vivo pathogenicity
of strains. Thus, 80% (P < 0.001) and 66% (P < 0.001) of strains
producing Col V and other types of colicins were characterized as being of
high pathogenicity, whereas only 15% of the noncolicinogenic strains were
classified as highly pathogenic. Our results clearly support the special
pathogenicity theory, because 60% of the E. coli strains belonging to 18
serogroups (O1, O2, O5, O8, O12, O14, O15, O18, O20, O53, O78, O81, O83,
O102, O103, O115, O116, and O132) most frequently identified among clinical
septicemic strains were classified as highly pathogenic in in vivo assays,
whereas only 24% of the strains with O serogroups less prevalent among
diseased chickens were considered highly pathogenic (P < 0.01).
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Production of toxins (enterotoxins, verotoxins, and necrotoxins) and colicins by Escherichia coli strains isolated from septicemic and healthy chickens: relationship with in vivo pathogenicity [In Process Citation]
Departamento de Microbiologia y Parasitologia, Facultad de Veterinaria, Universidad de Santiago de Compostela, Lugo, Spain.
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