Occurrence and Characterisation of Coagulase-Negative Staphylococci from Nigerian Traditional Fermented Foods

Coagulase-negative staphylococci (CoNS) were believed to be avirulent although recent studies have implicated them as causative agents of diseases. The lack of standardization and poor personal hygiene in the production of traditional fermented foods may introduce these organisms into food. This study was designed to investigate the occurrence of CoNS in Nigerian traditional fermented foods. In this study, the occurrence of CoNS in a total of 324 fermented food samples comprising of six traditional fermented food samples namely ogi, iru, nono, wara, kindirmo, kunu from North Central Nigeria was investigated. CoNS were isolated from the fermented food samples employing serial dilution technique and plating out on Mannitol salt agar (Oxoid, Germany). The identification of pure isolates was carried out using standard methods for phenotypic characterisation and genotypically characterised by PCR and 16S rRNA sequencing employing the primers; MSQ-F (5′- TGA AGA GTT TGA TCA TGG CTC AG-3′) and MSQ-R (5′-ACC GCG GCT GCT GGC AC-3′). A total of 255 (79.3%) CoNS were isolated and identified. The isolates were identified as S. epidermidis, S. xylosus, S. simulans, S. kloosii and S. caprae showing 90-95% homology with reference strains from NCBI database.  S. epidermidis (50%) was the highest occurring CoNS species in the food samples examined. S. epidermidis (30.5%) was predominant in iru, S. kloosii (28.6%), S. simulans (32%) and S. xylosus (33.3%) were the highest occurring CoNS species in kindirmo and S. caprae (38.5%) was predominant in nono samples. This study established the occurrence of CoNS in Nigerian traditional fermented foods. Personal hygiene especially by food handlers and producers should be encouraged. The education on food safety should be taught to local traditional food producers and legal actions taken against non-compliance to food safety standards. Milk produced locally should be pasteurized or heat treated before use in food production. Keywords: 16S rRNA sequencing, Characterization, Nigerian fermented foods, Coagulase-negative   staphylococci, Occurrence, Food safety

Antibiotic Resistance Profiling of Salmonella sp. isolated from African Catfish (Clarias gariepinus)

The African catfish (Clarias gariepinus) is an important fresh water fish consumed by a large percentage of the populace globally and it may be contaminated by pathogenic bacteria such as Salmonella sp. In this study, a total of fifteen (15) samples of African catfish were collected from different markets in Lokoja, Nigeria. The Salmonella sp. were isolated from the catfish samples by pre-enrichment in peptone water and subsequent inoculation on selective medium namely brilliant-green agar (BGA), bismuth sulphite agar (BSA) and Salmonella-Shigella agar (SSA). The Salmonella isolates were tested for susceptibility to 10 different commercially available antibiotics using the disc diffusion method. A total of thirty-four Salmonella species was isolated. The percentage occurrence of Salmonella sp. in the catfishes examined was very high (80%). The incidence of Salmonella sp. in the intestine (86.7%) of the catfish was higher than for the gills (66.7%) and the skin (73.3%). Majority of the isolates were resistant to Amoxicillin, Sulfomethoxazole-trimethoprim, Amoxicillin-clavulanic acid and Streptomycin. This study therefore demonstrated the occurrence of Salmonella species in African catfish with some exhibiting antibiotic resistance. Thus, there is a potential risk of transmission of drug resistant Salmonella species to man when contaminated catfish is consumed. The use of antibiotics in fish farming should be regulated so as to decrease antibiotic residues in fish

VIRULENCE AND TOXIGENICITY OF COAGULASE–NEGATIVE STAPHYLOCOCCI FROM NIGERIAN TRADITIONAL FERMENTED FOODS

The incidence of coagulase-negative staphylococci may render food unsafe as clinical isolates have been reported to exude virulent traits. A total of 255 CoNS isolates from six traditional fermented foods (nono, kunu, wara, iru, ogi and kindirmo) from North Central Nigeria identified as S. epidermidis, S. simulans, S. xylosus, S. kloosii and S. caprae were investigated for virulence traits. The stains were examined for biofilm formation, production of hyaluronidase, DNAse, TNAse, haemolysins and superantigenic toxins (SEA, SEB, SEC, SED and TSST-1) using standard and genotypic methods. The analysis of virulence factors revealed the production of slime in 200 (78.4%), α- haemolysin 136 (53.3%), β-haemolysin 43 (16.9%), DNAse 199 (78.0%), TNAse 29 (11.4%) and hyaluronidase 125 (49.0%), TSST-1 119 (46.7%) and enterotoxin producing isolates: SEA, SEB, SEC and SED (61 (23.9%), 19 (7.5%), 9 (3.5%) and 8 (3.1%) respectively). PCR analysis detected tsst-1, sea, seb and sec genes. The ability of these microorganisms to exhibit virulence evokes the potential to cause disease especially under determinate conditions or in immune-compromised patients. The occurrence of CoNS in food should not be ignored nor their pathogenic potential considered as insignificant rather safety measures should be taken to reduce or totally eliminate their occurrence in foods.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author