Compared to other livestock, domestic fowls are much more commonly reared and consumed in Nigeria. The emergence of serious live-threatening infections from veterinary sources and treatment failures occurring with the available antibiotics warrants investigation into the use of antimicrobial agents in poultry farms and how they contribute to the menace of antibiotic resistance. The main aim of this study was to investigate the use of antimicrobial agents in poultry farms by poultry farmers in Ile-Ife and the prevalence of resistance in bacterial isolates from the poultry. The study was carried out in two stages which comprised of field work and laboratory investigations.
A total of 60 questionnaires were distributed to farmers patronizing two well known poultry drug seller shops in Ile-Ife. Ten out of the 60 farms were subsequently visited for sample collection. Fresh feacal samples were collected from the farms for isolation and identification of E. coli and Staphylococci which were subsequently subjected to antimicrobial susceptibility tests.
All the poultry farmers used one or more antibiotics for their birds. Antibiotics were used mostly for therapeutic and prophylactic purposes and to a lesser extent for growth promotion. Cotrimoxazole and neomycin were the most commonly used antibiotics. The E. coli strains were more resistant than the staphylococci and showed 100% resistance to nalidixic acid and amoxicillin but with lower resistance to gentamicin.
Our findings provide additional evidence that the poultry production environment in Nigeria represents an important reservoir of antibiotic resistance genes which poses potential public health risk to human populations.
Compared to other livestock, domestic fowls are much more commonly reared in Nigeria [1,2]. The reasons for this are not far-fetching. It has been shown that the domestic fowl grow fast and have high financial returns with few social, health and religious taboos against its consumption, usage and production in contrast to other livestock [2,3]. Furthermore, in Nigeria, poultry meat and eggs are among the main source of protein in most homes [1].
Most commercial farmers rearing chicken for meat or layers for eggs rear them under intensive management system [4]. The farmers do everything possible to care for their fowls in order to prevent diseases and death and thus increase profitability. Apart from feeding, the next instrument in the arsenals of farmers in order to ensure this is the use of veterinary drugs. Antimicrobials comprised the major components of veterinary drugs [5]. These drugs are supplemented in poultry feeds at sub-therapeutic levels for growth improvement, prevention or reduction of disease outbreaks, improvement of digestion, acceleration of weight gain and increase in feed conversion ratio [5,6].
Despite the benefits derived from the use of antimicrobial agents in poultry and other livestock production, the increased use has been shown to contribute to the increasing prevalence of bacterial antibiotic resistance in humans [7-9]. Reports revealed widespread presence of antibiotic-resistant pathogens in poultry farms and products in many areas around the world [10-13]. Isolated pathogens include Staphylococcus aureus, Campylobacter, Salmonella, Escherichia coli, Proteus mirabilis, and some other enterobacterias [12-19].
E. coli isolated from Portuguese poultry were reported to have high resistant tetracycline (70%), ampicillin (63%) while low level of resistance was observed with co-trimoxazole (33%), gentamicin (17%) and co-amoxiclav (17%) [20]. Similarly, Salmonella isolated from retail raw poultry in China was resistant to sulfisoxazole (74.1%), tetracycline (71.1%) and to a lower extent, cefoxitin (19%). Only 4% of the isolates were sensitive to all the antibiotics tested [21]. In Jamaica, E. coli isolated from broiler chickens were resistant to kanamycin (91.2%), nalidixic acid (85.3%) and ampicillin (20.6%) but all the isolates were sensitive to gentamicin [22].
Antibiotic resistant organisms can get to the general population from the farm through food chain or animal handlers [17] and through the application of animal manure on crop lands [22-24]. Furthermore, it has been shown that farm-raised superbugs can exchange genetic materials and give their resistance to other bacteria, even of other genera and species that have never been exposed to antibiotics [18,25,26].
The emergence of serious live-threatening infections from veterinary sources and treatment failures occurring with the available antibiotics warrants investigation into the use of antimicrobial agents in poultry farms and how they contribute to the menace of antibiotic resistance [27-29]. Attempts to control the emergence of antibiotic resistance in humans will therefore involve taking care of its occurrence in animals, particularly poultry which are consumed by a large proportion of people in Nigeria.
The main aim of this study is to investigate the use of antimicrobial agents in poultry farms by poultry farmers in Ile-Ife and the prevalence of resistance in bacterial isolates from the poultry feaces.
Ethical approval was obtained from Osun State Health Research Ethics Committee, Osun State Ministry of Health (OSHREC/PRS/569T/123). The consents of selected farmers were sought and obtained after explaining the purpose of the study.
This study was carried out in Ile-Ife of Osun State, in South-West of Nigeria. Ile-Ife is a semi-urban town with two Local Government Areas, namely Ife Central and Ife East Local Government Areas. Geographically, Ile-Ife lies on longitude 4°69'E and latitude 70°50'N and has a humid tropical climate with distinct wet and dry seasons. Rainy season starts April through October while the dry season lasts October to March. Ile-Ife is an ancient town in Yoruba history and is regarded as the cradle of civilization [30]. Ile-Ife can be divided into five areas based on the major roads in the town: Ede road, Ibadan road, Ondo road, Sabo/ Ilesha road and road 7/campus.
This involved the use of questionnaires. A set questionnaire was designed to survey the antibiotics commonly used by farmers in their poultry farms. Two well known poultry drug seller shops in Ile-Ife were selected and visited twice in a week each for two consecutive weeks. Questionnaires were administered to clients (poultry farmers) that patronize these poultry drug sellers who gave informed consent to participate in the survey.
A total of 60 questionnaires were administered in the study period: 45 questionnaires were administered in the shop that had higher patronage and 15 questionnaires in the second. The questionnaires were grouped into five based on the five major roads in Ile-Ife town as already indicated.
Data gathered with the questionnaire were coded and entered into IBM/ SPSS version 21. This was used to generate frequencies and percentages.
Two filled questionnaires each were picked at random from each of the five groups making a total of ten questionnaires representing ten farms. The ten selected farms were visited for sample collection. Fresh fecal samples were collected in sterile universal bottles from the ten poultry farms. Samples were taken immediately to the laboratory for isolation and identification of E. coli and Staphylococci; and for antimicrobial susceptibility tests.
Feacal samples were plated on MacConkey Agar for E. coli and Mannitol Salt Agar for staphylococci isolation. Plates were incubated at 37 ℃ for 24 to 48 hours. Morphological characteristics of the colonies were noted for characterization. Further characterization of isolates involved biochemical tests such as catalase tests, indole production and sugar fermentations [10,13].
Few colonies from the plates were inoculated in 2 ml sterile distilled water, and shaken using a rotamixer for uniform dispersion until a turbidity conforming to 0.5 McFarmland Barium Sulphate standard unit (average turbidity, 108 cfu/ml) was obtained in accordance to standard guidelines [31]. Surface of the over-dried Mueller Hinton Agar plates were swabbed with the dispersion. Antibiotic discs were placed on the plates with the aid of flamed forceps and plates were then incubated in the refrigerator for an hour and subsequently at 37 ℃ for 24 hours. Antibiotics screened reflected both the ones being used by the poultry farmers as well as the commonly available. The antibiotics screened include: Augmentin® (30 µg), gentamicin (10 µg), nalidixic acid (30 µg), chloramphenicol (30 µg), cloxacillin (5 µg), erythromycin (5 µg), penicillin (1i.u.), streptomycin (10 µg), tetracycline (25 µg), ampicillin (10 µg), amoxicillin (25 µg) and cotrimoxazole (25 µg) (Abtek, England). The diameter of the zones of inhibition was measured for each of the disc and used for interpretation following standard guidelines [31].