Identificação de fatores de virulência de isolados de Escherichia coli oriundos de fezes de bezerros na região Sul do Brasil
Vargas Júnior, Sergio FariasCunha, Rodrigo CasqueroPereira, Daniela Isabel BrayerBotton, Sônia de ÁvilaLadeira, Silvia Regina LealLucia Júnior, ThomazSallis, Eliza Simone Viegas
Background: Escherichia coli (E. coli) is an enteropathogen that commonly causes diarrhea in calves. However, not all E. coli isolates are pathogenic. The aim of this study was to identify E. coli virulence factors derived from fecal samples collected in the southern region of Rio Grande do Sul state (RS) from calves with and without diarrhea, as well as investigate the antimicrobial susceptibility of E. coli isolates from calves with diarrhea. Materials, Methods & Results: Forty stool samples were collected in 12 farms, each one from calves having one day to six months of age, with and without diarrhea. The total DNA of from these isolates was extracted and a PCR using primers specific for the virulence factors Stx1, Eae, F41, F5 and STa was conducted. The susceptibility testing used the disk diffusion method and the susceptibility profile was evaluated against the following antimicrobials: ampicillin, penicillin, chloramphenicol, enrofloxacin, gentamicin, trimethoprim, sulfonamide, tetracycline and streptomycin. From all calves, 15 (15/40, 37.5%) had diarrheal stools and 25 (25/40, 62.5%) had normal or semi-liquid stools. Twelve (12/40; 30%) E. coli isolates showed at least one virulence factor. These factors were found in four isolates (4/15; 26.6%) from diarrheal stools and eight isolates (8/25; 28.5%) from normal stool. The Stx1 factor was identified in five isolates (5/40; 12.5%), and the Eae and the Sta factors in one (1/40; 0.2%) and in atypical associations between Stx1 and Eae and also between Eae and F41 in two isolates (2/40; 0.5%). Also, the Eae and Sta factors were identified in one isolate (1/40; 0.2%). The susceptibility test showed resistance to penicillin and tetracycline in 93% and 80% of the tested isolates, respectively. Discussion: The identification of virulence factors is necessary because E. coli is an enterobacterium present in calves gastrointestinal tract, to prove its pathogenicity. [ ](AU)
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