Listeria species and occurrence in retailed smoked fish samples in selected Ota markets, Ogun State, Nigeria

Abstract

This study investigated the prevalence of Listeria spp. in 72 samples of smoked species of codfish (Gadus morhua), herring (Clupea  harengus), catfish (Clarias gariepinus) and mackerel (Scomber scombrus) sampled from Sango (SA), Oju-ore (OO), Oja-Oba, Iyana-Iyesi  (II), Iju (IJ) and Atan (AT) markets, all in Ota, Ogun State, Nigeria. Adopting Oxoid Listeria Precis method, Listeria spp. were isolated and  characterized morphologically and biochemically. Of the 72 samples, 8 (11.11%) tested positive. Listeria ivanovii (1.38%), L. grayi (2.78%),  L. monocytogenes (2.78%) and L. innocua (4.16%) were identified in all the fish samples except Clupea harengus. Antibiotic sensitivity tests revealed all the isolates resisted Imipenem, Cefuroxime, Amoxillin and Cefexine but susceptible to Levofloxacin: 34mm (L. grayi) to  39mm (L. ivanovii), Ciprofloxacin: 25mm (L. monocytogenes) to 36mm (L. grayi) and Ofloxacin: 20mm (L. ivanovii) to 29mm (L. innocua).  Occurrence of these bacteria could indict the safety of the smoked fish products for consumption. The low percentage occurrences  coupled with the high antibiotic susceptibility may, however, relieve the potential consumers of the menace of the associated health risks  the consumption of such fish products could pose. The required control measures to prevent the occurrence of especially Listeria  monocytogenes and other species in the processing and distribution chains of these smoked fish products should be prioritized.