Abstract:
Normal intestinal flora of humans and animals constitute enormous reservoir of
resistance genes for potentially pathogenic bacteria and may serve as major
indictors of selection pressure exerted by anti-microbial use in a given population. A
study was conducted in September 2003 at 3 purposively selected peri-urban sites
spread across 3 senatorial zones of Imo state, Nigeria to determines the anti-
microbial resistance profile of commensal E. coli isolated from free range chickens.
The isolates were screened for anti-microbial resistance profile against 10 antibiotics
using the disc diffusion method. E. coli strains from local fowls, recorded 100 and
78.9% resistances against ampicillin and cotrimoxazole respectively, while resistance
rates against ciprofloxacin, gentamycin and norfloxacin were 0.0, 5.3 and 5.3%
respectively. Isolates from free-range cockerels recorded 100% resistance against
norfloxacin, cotrimoxazole and ampicillin and 83.3% against nitrofurantoin. Similarly,
isolates from old layers, recorded 100% resistance against nitrofurantoin,
cotrimoxazole, tetracycline, chloramphenicol and ampicillin and 80% against nalidixic
acid. Similar resistance trends were observed in E. coli isolates from free-range
turkeys and broiler roosters against the inexpensive broad-spectrum first line
antibiotics (ampicillin, nalidixic acid, cotrimoxazole, nitrofurantoin and
chloramphenicol), although values varied slightly across poultry types. Resistances
against gentamycin were consistently low in isolates from the different types of
poultry. Twenty-nine resistance patterns were observed in the E. coli isolates with
predominant patterns being distributed widely across poultry types indicating a
striking diversity of resistance patterns in the areas.
Key Words: E. coli, Anti-microbial resistance, Local fowl, Turkey, Roosters,
Cockerels, Nigeria
Introduction
The level of anti-microbial resistance in bacteria belonging to the normal intestinal
flora of humans and animals may increase due to exposure to antibiotics.(1) These
bacteria which constitute an enormous reservoir of resistance genes for potentially
pathogenic bacteria may serve as major indictors for selection pressure exerted by
anti-microbial use in a given animal or human population.(1-3) Investigation of
prevalence of resistance in such bacteria, especially E. coli may reveal the
prevalence of resistance in different animal populations and detect possible transfer
of resistant bacteria from animals to humans and vice versa.(1)
For E. coli and other classes of enterobacteriaceae in which asypmtomatic
colonization of the intestine usually precedes infection, acquisition of one or several
new genes, rather than point mutation in existing genes has been shown to be the
common ant-microbial resistance mediation route.(4-5) For example, segments of
new genes could be replaced with alleles having entirely different sequences from
the new type at multiple positions. These new mechanisms thus arise and spread in
the bacterial population under conditions of anti-microbial selective pressure.(5)
Again, it has been shown that exposure of most E. coli strains to anti-microbial
agents usually occurs during treatment directed at infections caused by other
unrelated organisms. Anti-microbial treatment that alters the population of E. coli in
a given host or environment, will usually affect bacterial contacts of the host or
environment.(6) Thus, use of a particular antibiotic in for example human hosts, in
an environment may increase the risk of colonization by or infection with resistant
organisms in other humans or even animals that have not received that set of
antibiotics but are sharing common environment with the humans.(5) Anti-microbial
OJHAS Vol 4 Issue 3, 2005-3-3: Original Article. Antimicrobial resistance profile of E.coli isolates from tropical free range chickens. www.ojhas.org/issue15/2005-3-3.htm