Molecular identification for six virulent genes of escherichia coli isolated from diarrheic calves and their resistance profile to antimicrobials in selected towns of south Wollo administrative zone, Amhara, Ethiopia.
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Date
2018-10
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Addis Ababa Universty
Abstract
Background: Escherichia coli are normal flora of the gastrointestinal tract frequently used as
model for various research questions. Potential gain and loss of virulent genes enable them to
become pathogenic and causes calf diarrhea while beneficial ones subsidize vitamin K2. These
virulent genes are found on plasmids, genomes or integrated on bacteriophages and horizontal
gene transfer plays in its epidemiology.
Objective: To identify virulence genes informative for four pathogenic strains of E. coli and
study their antibiotic resistance patterns to eleven antimicrobials agents.
Methodology: The study was conducted in Kombolcha, Dessie and Haik areas. Purposive
sampling was used to collect 123 fecal samples from 53 farms of all sites. E. coli isolates were
identified based on their green metallic sheen appearance on EMB agar, their characteristic
reactions on MacConkey agar and IMViC (+ + - -) biochemical tests. Antimicrobial
susceptibility testing of the isolates was carried out using agar disc diffusion method on Muller
Hinton agar following standard procedures. Genomic DNA was extracted from the isolates using
boiling method for strain identification using PCR.
Results: One hundred (81.3%) pure isolates of E. coli were harvested, of which, 23 (29.9%)
isolates carried one or more of the tested virulent genes. stx1 14(18.2%), stx2 7(9.1%), eae
9(11.7%), hlyA 1(1.3%) were the detected virulent genes with their respective frequency.
However, no isolates were detected for bfpA and aatA genes. Virulent genes were detected in 2-4
weeks aged calves at significantly higher order (P ≤ 0.05). Calves housed with their dam and
those given supplement feed were significantly associated with detected genes (P ≤ 0.05). From
samples processed using PCR, 14 (18.2%) were confirmed as STEC strain, 5 (6.5%) of EHEC
and 4 (5.2%) of EPEC. Most isolates were resistant to sulfonamide, clindamycine, ampicillin,
Oxytetracyclne, trimethoprime and streptomycin and sensitive to nitrfurantoin, gentamycin,
neomycin, clorampfenicol and ciprofloxacine.
Conclusion: Zoonotic STEC and EHEC strains are collectively found highest and implies
reservoir of calves to both farm animals and humans. Poor farm hygiene and frequent use of
limited antibiotics was a problem observed. As a consequence, farms hygiene, more spatial and
temporal distribution of E. coli should be concerned. Additionally, Antibiotics should be
alternatively used to avoid resistance.
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Keywords
Antimicrobials, Calf, Escherichia coli, Resistance Strains, Virulent Genes.