Occurrence and Antibiogram of Shigella spp in Free Range and Intensively Reared Chickens in Nsukka, Enugu State, Nigeria

Introduction: Shigellosis is considered a veterinary and public health problem of major importance. Shigella is implicated in food poisoning and bloody diarrhoea in humans and is an important cause of various diseases of livestock resulting in high morbidity and mortality. Shigella spp. is spread by direct contact with an infected host, or by eating contaminated food or drinking contaminated water. A cross-sectional survey was conducted to determine the occurrence of Shigella in free range and intensively reared chickens from markets and poultry farms in Nsukka, Enugu State, Nigeria, and to determine their antibiogram.

Materials and Methods: A total of 300 cloacal swabs from 150 free range and 150 intensively reared chickens, collected from 3 local markets and 3 farms respectively, were sampled. Shigella was isolated after passing the samples through pre-enrichment, selective enrichment and culture in a selective medium and identified using standard microbiological and biochemical methods. Antibiotic susceptibility test was performed by the disc diffusion method according to the CLSI method (Kirby-Bauer disk diffusion test) on Muller-Hinton agar.

Results: Out of the 300 samples, 10 (3.3%) were positive for shigellae. The occurrence in free-range chickens was 6.7%, while none was isolated in intensively reared chickens (0% occurrence). The Shigella spp. isolated were sensitive to ciprofloxacin (100%), moderately sensitive to ofloxacin (70%), gentamicin (70%), nalidixic acid (60%), cotrimoxazole (60%) and tetracycline (70%), and resistant to amoxicillin (100%) and augmentin (100%). The MIC ranges for cotrimoxazole, ciprofloxacin, gentamicin, and tetracycline, were 8-32, 0.015-0.25, 0.5-2.0, and 2.0-64.0 µg/ml, respectively. The MBC values obtained for ciprofloxacin, gentamicin, and tetracycline were 0.015-8, 2.0-8.0, and 128.0-512.0 µg/ml, were, respectively. The Shigella spp. isolates were classified as multidrug resistant. The difference in susceptibility patterns of the isolates from different sources was not significant (p > 0.05).

Conclusions: The findings of this study have shown that free-range chickens could serve as reservoirs/vehicles for the transmission of Shigella spp. in the study area.