Such poor and unhygienic disposal methods of human excrements definitely expose
local fowls that feed on such excrement to normal human enteric flora that may
harbor novel resistant factors. Furthermore, an enhancement of risk for acquisition of
resistant organisms by animal hosts, because of selective use of antibiotics in other
hosts in the same environment has recently been described by Lipsitch and
Samore.(5)
Resistance events in E. coli isolates from free-range cockerels exceeded that of local
fowls. It would seem that their exposure to resistance trends in the commercial farms
where they were started continued to influence events in colonizing organisms even
at their definitive locations. Thus, ampicillin, cotrimoxazole, nitrofurantoin,
norfloxacin and nalidixic acid were highly resistant in this group. The 100%
resistance returned by the E. coli isolates to norfloxacin is of public health
importance. This probably the first documented evidence of such a very high
resistance figure against any fluoroquinolone in bacterial isolates from farm animals
in Nigeria. In fact, Chah et al. (27) reported the highest resistance rate of 27.7% to
norfloxacin in E. coli from broilers. Ciprofloxacin, which is the only other
fluoroquinolone tested in this group however, recorded 0% resistances in the E. coli
isolates.
It is probable that even though norfloxacin and ciprofloxacin belong to the first
generation fluoroquinolones, the latter may have been introduced first into clinical
practice in the country. Both medicines however remain unavailable for veterinary
prescription in Nigeria. Current information indicates that quinolone resistance can
also be plasmid mediated, involving the qnr gene, which is quite distinct from the
known quinolone resistance genes. The gene has been isolated from E. coli and
Klebsiella pneumoniae and has been identified in USA and China.(28) It is probable
that this plasmid-mediated gene may be contributing to the wide distribution of high
bacterial resistance to quinolones in the study area.
The resistance rates observed in E. coli isolates from the old layers are alarming. One
hundred percent resistance was recorded against nitrofurantoin, cotrimoxazole,
tetracycline, chloramphenicol and ampicillin, and 80% for nalidixic acid indicating
that these compounds have become seriously compromised and probably are
currently of little value in the treatment of E. coli infections in the area. These
organisms may also constitute enormous reservoirs for genes encoding resistance
against these antibiotics and foci for continual spread of these mechanisms.(29-30)
The present figures, although higher are similar to the 93.3, 90.0, 70.0, and 60%
resistance to ampicillin, tetracycline, chloramphenicol, nitrofurantoin and
cotrimoxazole respectively reported by Chah et al. (20) in colisepticeamic E. coli
strains at Enugu state and Okoli et al (31) in E. coli isolates from a commercial layer
poultry farm in Owerri, Imo state, Nigeria.
E. coli isolates from turkeys and broiler roosters returned high figures for the
inexpensive broad-spectrum first line antibiotics (ampicillin, nalidixic acid,
cotrimoxazole, nitrofurantoin and chloramphenicol), although values varied slightly
across poultry types. These results once more tally with those of the other poultry
types especially free range cockerels and old layers earlier reported, thus confirming
high resistance profiles against these drug to be the order in E. coli isolates from
different types free-range poultry in Imo state.
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. Multi-drug resistance was a
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
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