Virulence properties and antimicrobial susceptibility of Shiga toxin-producing Escherichia coli strains isolated from healthy cattle from Paraná State, Brazil.
The presence of Shiga toxin-producing Escherichia coli (STEC) strains in feces samples of cattle was determined using the cytotoxicity assay on Vero cells and a screening PCR system to detect stx genes. The STEC isolates were serotyped, tested for antimicrobial susceptibility, and analyzed for virulence genes using multiplex PCR. The verocytotoxin-producing E. coli - reverse passive latex agglutination (VTEC-RPLA) assay was also used to detect Shiga toxin production. The frequency of cattle shedding STEC was 36%. The isolates belonged to 33 different serotypes, of which O10:H42, O98:H41, and O159:H21 had not previously been associated with STEC. The most frequent serotypes were ONT:H7 (10%), O22:H8 (7%), O22:H16 (7%), and ONT:H21 (7%). Most of the strains (96%) were susceptible to all antimicrobial agents tested. Shiga toxin was detected by the VTEC-RPLA assay in most (89%) of the STEC strains. The frequency of virulence markers was as follows: stx1, 10%; stx2, 43%; stx1 plus stx2, 47%; ehxA, 44%; eae, 1%; and saa, 38%. Several strains belong to serotypes associated with human disease, and most of them carried a stx2-type gene, suggesting that they represent a risk to human health. The screening PCR assay showed fewer false-negative results for STEC than the Vero-cell assay and is suitable for laboratory routine.
Pigatto
Caroline P
CP
Department of Veterinary Medicine, Federal University of Paraná, Brazil.
Schocken-Iturrino
Ruben P
RP
Souza
Emanuel M
EM
Pedrosa
Fábio O
FO
Comarella
Larissa
L
Irino
Kinue
K
Kato
Maria Aidê M F
MA
Farah
Sônia M S S
SM
Warth
José F
JF
Fadel-Picheth
Cyntia M T
CM
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015373:Bacterial Typing Techniques; D001938:Brazil; D002417:Cattle / Q000382:microbiology*; D002522:Chlorocebus aethiops; D005243:Feces / Q000382:microbiology; D022603:Shiga Toxins / Q000235:genetics / Q000378:metabolism*; D054323:Shiga-Toxigenic Escherichia coli / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*; D014709:Vero Cells; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D022603:Shiga Toxins; D037521:Virulence Factors