Prevalence and characteristics of Escherichia coli serotype O157:H7 and other verotoxin-producing E. coli in healthy cattle.
From February to July of 1994, 328 faecal samples from 32 herds were collected and verotoxin-producing Escherichia coli (VTEC) found on 84% of the farms. The proportion of animals infected varied from 0-63%. VTEC were recovered from 52 (20%) of 257 cows and from 16 (23%) of 71 calves. Although the VTEC belonged to 25 different serogroups, 7 (O8, O20, O22, O77, O113, O126 and O162) accounted for 46% of strains. Nearly 45% of the strains. Nearly 45% of the 83 bovine VTEC strains belonged to serogroups associated with haemorrhagic colitis and haemolytic uraemic syndrome in humans. However, only 2 (2%) of 83 VTEC strains isolated from cattle belonged to enterohaemorrhagic E. coli (EHEC) serotypes (O26:H11 and O157:H7), and only 8 (10%) were positive for the attaching and effacing E. coli (eae) gene sequence. Polymerase chain reaction (PCR) showed that 17 (20%) of VTEC strains carried VT1 genes, 43 (52%) possessed VT2 genes, and 23 (28%) carried both VT1 and VT2 genes. Characterization of VTEC isolates revelated a heterogeneous population in terms of serogroup and toxin type in the positive herds. This study confirms that healthy cattle are a reservoir of VTEC, but, the absence of eae genes in most bovine VTEC strains suggests that they may be less virulent for humans than eae-positive EHEC.
Blanco
M
M
Departmento de Microbiologia y Parasitologia, Facultad de Veterinaria, Universidad de Santiago de Compostela, Lugo, Spain.
Blanco
J E
JE
Blanco
J
J
Gonzalez
E A
EA
Mora
A
A
Prado
C
C
Fernández
L
L
Rio
M
M
Ramos
J
J
Alonso
M P
MP
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000382:microbiology*; D004197:Disease Reservoirs; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000145:classification* / Q000235:genetics; D005243:Feces / Q000382:microbiology; D011159:Population Surveillance; D015995:Prevalence; D012703:Serotyping; D013030:Spain / Q000453:epidemiology