C. N. Moreira

Detecção de fatores de virulência e de resistência antimicrobiana em isolados produtores de toxina Shiga de ovinos

In order to detect virulence factors in Shiga toxin-producing Escherichia coli (STEC) isolates and investigate the antimicrobial resistance profile, rectal swabs were collected from healthy sheep of the races Santa Ines and Dorper. Of the 115 E. coli isolates obtained, 78.3% (90/115) were characterized as STEC, of which 52.2% (47/90) carried stx1 gene, 33.3% (30/90) stx2 and 14.5% (13/90) both genes. In search of virulence factors, 47.7% and 32.2% of the isolates carried the genes saa and cnf1. According to the analysis of the antimicrobial resistance profile, 83.3% (75/90) were resistant to at least one of the antibiotics tested. In phylogenetic classification grouped 24.4% (22/90) in group D (pathogenic), 32.2% (29/90) in group B1 (commensal) and 43.3% (39/90) in group A (commensal). The presence of several virulence factors as well as the high number of multiresistant isolates found in this study support the statement that sheep are potential carriers of pathogens threatening public health.

Escherichia coli enterohemorrágica O157: H7 em bovinos leiteiros saudáveis no Centro-Oeste do Brasil: ocorrência e caracterização molecular

Enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 represents the major Shiga toxin-producing E. coli (STEC) strain related to large outbreaks and severe diseases such as hemorrhagic colitis (HC) and the potentially lethal hemolytic uremic syndrome (HUS). The aim of this study was to report the occurrence and molecular characterization of O157:H7 isolates obtained by rectal swab from 52 healthy dairy cattle belonging to 21 farms in Mid-West of Brazil. Detection of 16SrRNA, stx1, stx2, rfbO157, fliCh7, eae, ehxA, saa, cnf1, chuA, yjaA and TSPE4.C2 genes was performed by PCR. The isolates were further characterized by serotyping. Two hundred and sixty E. coli isolates were obtained, of which 126 were characterized as STEC. Two isolates from the same cow were identified as serotype O157:H7. Both isolates presented the stx2, eae, ehxA, saa and cnf1 virulence factor genes and the chuA gene in the phylogenetic classification (virulent group D), suggesting that they were clones. The prevalence of O157:H7 was found to be 1.92% (1/52 animals), demonstrating that healthy dairy cattle from farms in the Mid-West of Brazil are an important reservoir for highly pathogenic E. coli O157:H7.

Serum γ-glutamyltransferase activity as an indicator of chronic liver injury in cattle with no clinical signs

This study aimed to determine the power of the serum aspartate aminotransferase (AST) and gamma-glutamyltransferasase (GGT) activities and of the albumin and cholesterol dosages for detecting hepatic histopathological injuries. A total of 220 healthy male Nelore cattle that had been extensively bred were evaluated. Blood and liver samples were collected on the day of slaughter for biochemical and histopathological tests. The results showed that the sensitivity to AST, GGT, albumin, and cholesterol tests were respectively 22.4%, 22.4%, 36%, and 37.2%. The specificity of AST, GGT, albumin, and cholesterol tests was respectively 78.8%, 90.4%, 75.6%, and 68.3%. In short, the detection of minor liver injuries through biochemical tests is limited; however, the high specificity of the GGT allows its use as an indicator of hepatic chronic injuries in cattle herds.