Molecular characterization, technological properties and safety aspects of enterococci from 'Hussuwa', an African fermented sorghum product

Abstract

Aims: To identify enterococci from Hussuwa, a Sudanese fermented sorghum product, and determine their technological properties and safety for possible inclusion in a starter culture preparation. Methods and Results: Twenty-two Enterococcus isolates from Hussuwa were identified as Enterococcus faecium by using phenotypic and genotypic tests such as 16S rDNA gene sequencing, RAPD-PCR and restriction fragment length polymorphism of the 16S/23S intergenic spacer region fingerprinting. Genotyping revealed that strains were not clonally related and exhibited a considerable degree of genomic diversity. Some strains possessed useful technological properties such as production of bacteriocins and H 2 O 2 or utilization of raffinose and stachyose. None produced a-amylase or tannase. A safety investigation revealed that all strains were susceptible to the antibiotics ampicillin, gentamicin, chloramphenicol, tetracycline and streptomycin, but some were resistant to ciprofloxacin, erythromycin, penicillin and vancomycin. Production of biogenic amines or presence of genes encoding virulence determinants occurred in some strains. Conclusions: Enterococcus faecium strains are associated with fermentation of Sudanese Hussuwa. Some strains exhibited useful technological properties such as production of antimicrobial agents and fermentation of indigestible sugars, which may aid in stabilizing and improving the digestibility of the product respectively. Significance and Impact of the Study: Enterococci were shown to play a role in the fermentation of African foods. While beneficial properties of these bacteria are indicated, their presence in this food may also imply a hygienic risk as a result of antimicrobial resistances or presence of virulence determinants.

Occurrence of enterocin genes, virulence factors, and antibiotic resistance in 3 bacteriocin-producer Enterococcus faecium strains isolated from Turkish tulum cheese

“…The exact role of efaAfm as a virulence factor is still unknown (11). The efaAfm gene has not yet been conclusively shown to contribute to pathogenesis in animal studies, in contrast to the adhesion-like E. faecalis antigen A (efaAfs) (15). Furthermore, the absence of cylMBA and gelE genes in E. faecium EYT17, EYT31, and EYT39 strains agrees with our observation that these strains lack β-haemolytic and gelatinase activity.…”

“…PCR for structural genes of enterocins was performed as an initial cycle of denaturation at 94 °C for 5 min, followed by 35 cycles of denaturation 94 °C for 1 min, annealing at an appropriate temperature for 1 min, and elongation at 72 °C for 40 s (15). The amplification products were analysed by electrophoresis on 1.5% agarose gel at 120 V for 1.5 h in Tris-acetate-EDTA buffer and revealed in ethidium bromide (20 µg/mL).…”

Bioprospecting of strains of Streptococcus thermophilus from Indian fermented milk products for folate production

“…Similarly Andrighetto et al (2002) analysed the genetic variability within 218 S. thermophilus isolates from Italian traditional cheeses by RAPD-PCR and showed five major clusters at 60% similarity level. Later, Yousif et al (2005) showed considerable degree of genomic diversity between 21 Enterococcus isolates from Hussuwa fermentations carried out in different surroundings by RAPD-PCR genotyping using M13 and AP4 primer. Omar et al(2006) also evaluated the genetic diversity of seven isolates from ben saalga, a traditional fermented gruel from Burkina Faso using primer M13 and AP4, and found that six of the isolates were genetically different, indicating that they were in fact different strains.…”

Functional and safety aspects of enterococci in dairy foods

“…Thus, before using enterococci for food production or in probiotic preparations, safety of these strains should be evaluated. Recently, many authors have assessed the safety of enterococci isolated from different origins [93][94][95][96][97]. Safe strains of enterococci that can be used in food and as probiotics ideally should possess neither any of virulence factors, nor should be able to acquire antibiotic resistance gene [8].…”