Microbiological evaluation of the indigenous fermented condiment okpeye available at various retail markets in the south-eastern region of Nigeria

Abstract

In Africa, indigenous fermented condiments contribute to food security as a low-cost source of protein. <i>Okpeye</i> is an indigenous fermented condiment produced from <i>Prosopis africana</i> seeds. The reliance on spontaneous fermentation processes and unhygienic practices during production often results in the contamination of the final product with microbial hazards. A microbiological evaluation of 18 commercial samples of <i>okpeye</i> purchased from six markets in two cities in southeastern Nigeria was conducted. Fifty-nine (59) bacteria were isolated and identified at the species level by phenotyping and sequencing the 16S <i>rRNA</i>, <i>gyrB</i> and <i>rpoB</i> genes. <i>Bacillus</i> (47.4 %) and <i>Staphylococcus</i> (42.3 %) were the predominant bacterial genera in <i>okpeye</i>. Overall, <i>B. amyloliquefaciens</i> and <i>S. simulans</i> were the most frequently occurring bacteria and were present in all samples. In addition, <i>B. cereus</i> was isolated in samples obtained from all markets. Other bacterial species included <i>B. velezensis, Oceanobacillus caeni</i>, <i>S. cohnii, Escherichia fergusonni</i> and <i>Vagacoccus lutrae.</i> The <i>B. cereus</i> isolates (10) were screened for the presence of 8 enterotoxin genes (<i>hblA</i>, <i>hblC</i>, <i>hblD</i>, <i>nheA</i>, <i>nheB</i>, <i>nheC</i>, <i>cytK</i>, <i>entFM</i>) and one emetic gene (<i>cesB</i>). The non-haemolytic enterotoxin (<i>nheABC</i>) and haemolytic enterotoxin (<i>hblABD</i>) complexes were present in 70 % and 50 % of <i>B. cereus</i> respectively. The positive rate of <i>cytK</i> and <i>entFM</i> genes was 70 %, while the <i>cesB</i> gene was 30 %. Antibiotic susceptibility assessment showed that most of the isolates were susceptible to gentamicin, tetracycline, streptomycin, and erythromycin but resistant to ciprofloxacin and vancomycin. These findings highlight the need for further controls to reduce contamination with potential pathogenic bacteria in indigenous fermented condiments such as <i>okpey</i>e. There is also a need to educate producers regarding hygienic practices to safeguard public health and food security.