Prevalence and comparison of Streptococcus infantarius subsp. infantarius and Streptococcus gallolyticus subsp. macedonicus in raw and fermented dairy products from East and West Africa

Abstract

Streptococcus infantarius subsp. infantarius (Sii) and Streptococcus gallolyticus subsp. macedonicus are members of the Streptococcus bovis/Streptococcus equinus complex (SBSEC) associated with human infections. SBSEC-related endocarditis was furthermore associated with rural residency in Southern Europe. SBSEC members are increasingly isolated as predominant species from fermented dairy products in Europe, Asia and Africa. African variants of Sii displayed dairy adaptations to lactose metabolism paralleling those of Streptococcus thermophilus including genome decay. In this study, the aim was to assess the prevalence of Sii and possibly other SBSEC members in dairy products of East and West Africa in order to identify their habitat, estimate their importance in dairy fermentation processes and determine geographic areas affected by this potential health risk. Presumptive SBSEC members were isolated on semi-selective M17 and SM agar media. Subsequent genotypic identification of isolates was based on rep-PCR fingerprinting and SBSEC-specific16S rRNA gene PCR assay. Detailed identification was achieved through application of novel primers enhancing the binding stringency in partial groES/ groEL gene amplification and subsequent DNA sequencing. The presence of S. thermophilus-like lacS and lacZ genes in the SBSEC isolates was determined to elucidate the prevalence of this dairy adaptation. Isolates (n = 754) were obtained from 72 raw and 95 fermented milk samples from Côte d'Ivoire and Kenya on semi-selective agar media. Colonies of Sii were not detected from raw milk despite high microbial titers of approximately 10 6 CFU/mL on M17 agar medium. However, after spontaneous milk fermentation Sii was genotypically identified in 94

The clinical epidemiology and malignancies associated with Streptococcus bovis biotypes in 506 cases of bloodstream infections

“…13,14 Some factors such as diet or animal contact might have a role in human intestinal colonization by Sb. 14,15 A previous study of our group has also suggested an increased rate of Sb endocarditis in rural setting, 16 being higher than those reported in other hospitals of our country. 17e19 We studied a large cohort of patients with Sb bacteraemia including the following issues: 1) Incidence of Sb bacteraemia in three geographical areas; 2) Comparison of clinical findings between Sb-I and Sb-II cases; and 3) The association of Sb-I and Sb-II with malignancies.…”

“…A plausible explanation for the link between Sb bacteraemia and rural areas is that people living in these areas are at higher risk of acquiring Sb through close contact with animals or contaminated food. 14,15 Moreover, an association between Sb bacteraemia/endocarditis and CRN was already established. 31,32 Consequently in settings with high rates of CRN an increased rates of Sb bacteraemia might be expected, which is the case of France presenting high incidence of CRN.…”

Acquisition through Horizontal Gene Transfer of Plasmid pSMA198 by Streptococcus macedonicus ACA-DC 198 Points towards the Dairy Origin of the Species

“…After its original description S. macedonicus has been identified in a wide range of dairies around the world and current studies indicate that milk and its products represent its primary ecological niche [ 6 ]. Similarly to S. macedonicus , strains of S. infantarius have been isolated from the food environment [ 8 , 9 ]. Both species are clearly related to the other members of the SBSEC, such as the commensals Streptococcus gallolyticus and Streptococcus pasteurianus that are associated with endocarditis, bacteremia and colon cancer [ 10 , 11 ].…”

“…Such HGT events seem to be specific for S. macedonicus and S. infantarius and to be absent from S. gallolyticus and S. pasteurianus. Events like these in the evolutionary history of the two species suggest a longstanding relationship with milk and fermented dairy products, even though their actual presence in these niches was only recently confirmed [ 6 , 9 ]. Among the most common HGT mechanisms is conjugation which involves the transfer of DNA by plasmids through plasmid encoded cell-to-cell junctions [ 18 ].…”

Strain-Level Metagenomic Analysis of the Fermented Dairy Beverage Nunu Highlights Potential Food Safety Risks

“…However, we also detected high abundances of Enterobacteriales, including Enterobacter and Escherichia, in both groups. Subsequently, wholemetagenome shotgun sequencing showed that most samples were dominated by Streptococcus infantarius, a species that had been identified previously in other African dairy products (29,30). Of concern, S. infantarius has been linked to several human diseases, including bacteremia (31), endocarditis (32), and colon cancer (33).…”