Proximate Composition and Antibiotic Resistant Listeria Species in Fura-de-nunu Sold in Port Harcourt

Aims: The study evaluated the proximate composition and the occurrence of antibiotic resistant Listeria species from fura-de-nunu sold in Port Harcourt metropolis.

Study Design: The experiment was conducted in duplicate and mean values calculated.

Place and Duration of Study: Department of Microbiology, University of Port Harcourt, Nigeria, between October 2013 and May, 2014.

Methodology: A total of 101 samples were examined for the presence of Listeria using standard methods employing Fraser broth and polymixin acriflavin lithium chloride ceftazidime aesculin mannitol (PALCAM) agar. Characteristic colonies were identified on the basis of Gram staining, catalase reaction, oxidase reaction, beta haemolysis on sheep blood agar and carbohydrate fermentation using mannitol, rhamnose and xylose. Antibiotic susceptibility of the isolates was determined by the disk diffusion method on Mueller-Hinton Agar, according to CLSI guidelines using the breakpoints of Staphylococcus species resistance since no resistance criteria exist for Listeria susceptibility testing in the CLSI guidelines. The moisture, crude protein, crude fibre, crude fat, carbohydrate and total ash contents of the fura-de-nunu samples were analysed using the method described by Association of Official Analytical Chemists.

Results: The average proximate chemical analysis shows the following: moisture (84.92%), ash (0.48%), carbohydrate (7.70%), protein (3.32%), lipid (3.09%) and fibre (0.49%). Out of the 101 samples examined, Listeria spp. was present in 38 (37.60%) samples. The resulting isolates were confirmed to be L. grayi, 29.63% (40 of 135 isolates), L. seeligeri 18.52% (25 of 135 isolates) and L. welshimeri 51.85% (70 of 135 isolates). The results of the antibiotic sensitivity testing showed varying degrees of resistance against the selected antibiotics with the highest resistance against erythromycin (73.53%), followed by cloxacillin (61.76%) and least was against chloramphenicol (16.91%).

Conclusion: The presence of antibiotic resistant Listeria spp. portends danger for consumers of this product hence efforts should be intensified in ensuring the safety of consumers.