Isolation and characterization of histamine-producing, multi-drug-resistant Enterococcus species in fermented oil bean seeds in Nsukka, Nigeria

Abstract

Aims: The microbiological qualities of fermented oil bean seeds depend on the indigenous microflora, personal and environmental hygiene of the handlers and the food environments. This study was aimed to evaluate the incidence of histamine-producing, multi-drug-resistant Enterococcus isolates from oil bean seeds during fermentation. Methodology and results: Histamine extraction and analysis were performed on randomly sampled oil bean seeds. Histamine producing lactic acid bacteria (LAB) were isolated, from where Enterococcus species were further isolated. Strain-specific identification and antibiotic sensitivity tests were carried out on the identified Enterococcus isolates. Histamine was detected in fermented seeds. Enterococcus strains were identified among the histamine-producing fermenters. These include E. faecalis HA5, E. faecium VB976, E. faecium LMEM18, E. gallinarum M190262 and E. gilvus CR1. Enterococcus faecalis HA5, E. faecium VB976, E. faecium LMEM18, E. gallinarum M190262 and E. gallinarum were resistant to Ampiclox, Amoxicillin, Ceftriaxone, Ciprofloxacin and Erythromycin. Enterococcus faecium VB976, E. faecium LMEM18 and E. gallinarum M190262 were resistant to Streptomycin and Gentamycin. Enterococcus faecalis HA5 was intermediately resistant to Streptomycin and Gentamycin but sensitive to Vancomycin, while E. gilvus was intermediately resistant to Ampiclox, Amoxicillin and Gentamycin but sensitive to Ceftriaxone, Vancomycin, Ciprofloxacin, Streptomycin and Erythromycin. Conclusion, significance and impact of study: The pathogenic and histamine-producing abilities of Enterococcus pose serious public health hazard. This is complicated by their resistance to a wide range of antibiotics. Therefore, improving the hygienic practices and regulating fermentation conditions is essential to curtailing histamine production and growth of fermenters with pathogenic potentials and ensuring the safety of the product.