Abstract

Plasmids are extra-chromosomal genetic materials which confer some attributes such as resistance to antibiotics, chemicals and synergy formation among the bacteria. Abattoir plays a vital role to man by serving a link for the inflow of animal protein to the food chain but can also serve as a hotspot for the influx of pathogenic bacteria such as Escherichia coli with antibiotic and virulent traits. This study aimed at exploring the potential involvement of plasmids on antibiotic resistance and virulence in E. coli from three select abattoirs in Aba Metropolis, Nigeria. Fifty (50) E. coli isolates collected from soil, effluent, butchers’ palms, animals, table/slab and knives were phenotypically identified using cultural characteristic growth pattern of the organism on Eosin Methylene Blue (EMB) and biochemical test. Using plasmid elimination technique, plasmids from the bacterial isolates were cured using acridine orange while virulence traits of protease formation, hemolysis and biofilm formation were carried out using skim milk agar, blood agar and Congo red agar respectively and the antibiotic susceptibility testing was carried out using the Kirby Bauer method. The rate of resistance in the uncured bacteria isolates ranged from 82.7% to 100% in uncured isolates which was similar to results obtained following plasmid curing. Plasmid curing had a minimal effect on resistance rates as only 1% to 2% observed change were observed in majority of the antibiotics tested (91.7%) but greater than 5% decrease (6.2%) was observed only with respect to a single antibiotic (ofloxacin). Same slight change was recorded in Multiple Antibiotic Resistance (MAR) indices of the bacteria: 79.6% to 71.4% (index 1), 18.4%-23.5% (index 0.92) and 2%-5.1% (0.83). Same trend was observed in the studied virulence traits of 30% to 46% before curing and 24% to 34% after curing. Only 5% reduction took place in the isolates except for hemolysin production which reduced by 10%. These finding indicate minimal role of plasmids in antibiotic resistant E. coli with virulent traits from select abattoirs in Aba metropolis of Nigeria.