Antibiogram of Listeria and Salmonella Species Isolated from Tilapia Fish (Oreochromis nitolicus) and Snail (Archachatina marginata) Sold in Port Harcourt, Nigeria

Land snails are ubiquitous creatures found on farms, forests and domesticated in homes. Bacteriological studies indicate that various potentially pathogenic bacteria inhabit different organs and tissues including the haemolymph of the African giant snail, the presence of pathogenic bacteria in the snails are a health threat to consumers and may cause food borne diseases/ infection. Pollution of aquatic environments with organic waste of animal and human origin may lead to transfer of pathogens to the fishes, thereby making them carriers of the pathogens. In this study antibiogram studies were carried out on the isolates from snail and tilapia fish to determine antibiogram of Listeria monocytogenes and Salmonella species isolated from tilapia fishes and snails sold in Port Harcourt. One hundred and thirty two (132) samples were obtained from three different markets namely; Creek road, Mile one and Rumuokoro markets over a period of six months. Standard analytical protocols were employed to determine the bacteriological characteristics of the various parts such as intestine, flesh/meat, gills and fluid(snail). Antibiogram of Listeria and Salmonella species were determined using standard methods as recommended by CLSI. Statistical analyses were carried out using ANOVA and All pairs tukey-kramer. Results of Total heterotrophic bacterial count shows that snail samples had the highest number of bacterial count compared to frozen tilapia fishes. Mean Listeria spp. count for frozen tilapia fish ranged from 2.7 ±0.68 x104cfu/g to 2.9 ±0.23 x104cfu/g (flesh), 3.3 ±0.15 x104 to 3.7 ±0.35 x104cfu/g (gill), 3.8 ±0.44 x104 to 4.3 ±0.57 x104 cfu/g (Intestine), across the three markets, Mean Listeria spp. count for snail sample ranged from 0.7 ±0.29 x104 to 1.1 ±0.18 x104cfu/ml (Snail fluid) 1.1 ±0.18 x104 to 1.2 ±0.16 x104cfu/g (meat), 1.6 ±0.44 x104 to 1.9 ±0.57 x104cfu/g (Intestine) Creek road market. Mean total Salmonella count for frozen tilapia fish ranged from 1.0 ±0 x103cfu/g to 1.3 ±0.58 x103 (flesh), 1.0 ± 0 x103 to 1.6 ± 0.58 x103cfu/g (gills), 1.2 ±0.5 x103 cfu/g to 2 .0 ±1.41 x103 cfu/g (Intestine), across the three markets. Mean total Salmonella count for snail ranged from 1.0 ±0.58 x103 to 1.3 ±0 x103cfu/ml (fluid), 1.5 ±1.0 x103 to 1.7 ±0.96 x103cfu/g (meat), 1.7 ±0.96 x103cfu/g to 3.0 ±1.58 x103cfu/g (Intestine), across the three markets. Results of antibiogram revealed that all the Listeria species were 100% susceptible to Levofloxacin, Ofloxacin, Gentamycin, Azithromycin, Erythromycin and Ceftriaxone-sulbactam but 100% resistance to Augmentin, Ciprofloxacin and Cefuxime while Salmonella species were 100% susceptible to Ofloxacin and Ciprofloxacin and resistance to Cetazidime and Gentamicin, thus, these drugs should be considered the drug of choice for infections caused by these bacteria,