Lactic acid bacteria diversity of African raw and fermented camel milk products reveals a highly competitive, potentially health-threatening predominant microflora

Abstract

The microflora of 59 East African camel milk samples of unfermented raw milk supply chains and spontaneously fermented milk (suusac) was analyzed to describe the diversity of predominant lactic acid bacteria (LAB), identify potential health risks and study bacteriocin-like inhibitory substance (BLIS) production. Bacterial isolates (n = 532) were identified using a genotypic approach incorporating rep-PCR, 16S rRNA gene sequencing, and species-specific PCR assays. The bacterial numbers on MRS and M17 agar exceeded log10 6.5 colony forming units (CFU) mL−1 for raw milk supply chain samples and log10 8 CFU mL−1 for suusac. Streptococcus agalactiae and Staphylococcus spp. were predominant in unfermented products, while suusac contained predominantly Streptococcus infantarius subsp. infantarius followed by Lactococcus lactis subsp. lactis, Streptococcus thermophilus, and lactobacilli. Fifty per cent of S. infantarius subsp. infantarius isolates originating from 15 out of 24 suusac samples produced a BLIS active against other LAB or Listeria and representing a potential selective advantage during fermentation. This study provides a detailed insight at the genotypic level into the LAB diversity of previously unstudied dairy products. It indicates potential health risks for consumers and the need for hygienic and manufacturing interventions and reports a potentially novel BLIS produced by S. infantarius subsp. infantarius.