| dc.description.abstract | Escherichia coli and isolates belonging to serotypes O157 are Gram negative, rod shaped
bacteria that have received a lot of attention recently due to their potential to cause life
threatening sporadic incidents and outbreaks of infections in humans worldwide. The aim of
this study was to determine the prevalence and virulence of gene profiles of Shiga-toxigenic
Escherichia coli O157:H7 strains isolated from cattle. A total of 500 faecal samples were
collected from cattle in both communal and commercial farms in the North West province,
South Africa. Isolation of E. coli was done by sub-culturing a loop full of the bacterial colony
onto Sorbitol Mac-Conkey agar (Bio lab, South Africa) supplemented with cefixime and
potassium tellurite (SMAC-CT). Identification of E. coli isolates were performed using
preliminary (serological assay) and confirmatory (PCR assay) tests. Antibiotic susceptibility
test was performed using the Kirby-Bauer disc diffusion method to determine the resistance
profile of the isolates against a panel of seven different antimicrobial agents (Ciprofloxacin,
Gemifloxacin, Levofloxacin, Moxifloxacin, Tetracycline, Penicillin and Norfloxacin).
From 326 isolates, 119 were positive for serological assay and 62 isolates were found
positive uidA gene fragment. Of those 62 isolates, 5 (83.3%) isolates were from Rooigront
farm, 3 (37.5%) from Molelwane farm, 16 (80%) from Lokaleng farm, 16 (100%) from
Rooigrond prison farm, 6 (66.6%) from Klippan, 15 (37.5%) from Ottosdal farm and 1 (5%)
was from Zeerust. Fifty isolates were found positive for rfbO157 gene fragment. Of these 50
isolates, 3 (6%) isolates from farm, 3 (37.5%) from Molelwane farm, 16 (80%) from
Lokaleng farm, 8 (50%) from Rooigrond prison farm, 5 (55.5%) from Klippan, 15 (37.5%)
from Ottosdal farm and 0 (0%) from Zeerust. Fifty-five (55) of confirmed E. coli O157:H7
isolates were positive for shiga-toxins genes of which 30 (60%) isolates carried stx1 virulene
gene while 25 (50%) carried stx2 gene. The persistence- of other virulence genes. Iha, toxB,
katP, espP, tir and terD genes were confirmed in 7 (14%), 9 (18%), 5 (10%), 13 (26%), 11
(22%) and 50 (100%) isolates respectively. In the present study most of the isolates were
found to be resistant to tested antimicrobial agents. Most isolates were resistant towards
Ciprofloxacin (40%), Amplicillin (100%) and Moxifloxacin (28%), while all the isolates were
found susceptible to Levofloxacin, Tetracycline, Gemifloxacin and Norfloxacin. Multiple
antibiotic resistant (MAR) phenotypes AP-C-M were dominant in all the tested isolates.
Therefore, hypothetically it can be concluded that the bacterial isolates did have the STECvirulence
strains within their host which were then able to be expressed in the presences of
antimicrobial agents especially those that are frequently utilized in veterinary and human
medicine. | en_US |
