Investigating the association between African spontaneously fermented dairy products faecal carriage of Streptococcus infantarius subsp. infantarius and colorectal adenocarcinoma in Kenya

摘要

class="kwd-title">Abbreviations: cFPD, commercial fermented dairy products; CRC, Colorectal cancer; tFDP, Traditional fermented dairy products; GIT, Gastrointestinal tract; KNH, Kenyatta National Hospital; OR^A, Odds ratio adjusted; SBSEC, Streptococcus bovis/Streptococcus equinus complex; Sgg, Streptococcus gallolyticus subsp. gallolyticus; Sgm, Streptococcus gallolyticus subsp. macedonicus; Sgp, Streptococcus gallolyticus subsp. pasteurianus; Sii, Streptococcus infantarius subsp. infantarius; yFPD, yoghurt fermented dairy product class="kwd-title">Keywords: Spontaneously fermented dairy products, Colonic disorders, Streptococcus bovis, Streptococcus gallolyticus, Colitis, Colorectal cancer class="head no_bottom_margin" id="abs0015title">AbstractConsumption of traditional fermented dairy products (tFDP) in Africa leads to the ingestion of up to 10⁸Streptococcus infantarius subspecies infantarius (Sii) per millilitre of spontaneously fermented milk. Sii is a member of the Streptococcus bovis/Streptococcus equinus complex (SBSEC) for which some members are associated particularly with colorectal cancer or endocarditis. The extent of health risks to tFDP consumers is largely unknown.A hospital-based unmatched case-control study was conducted at Kenyatta National Hospital, Nairobi (Kenya) on 80 cases and 193 controls that were selected exhaustively from patients attending colonoscopy at the hospital. Logistic regression models adjusted for age, sex and residency were used in the statistical analysis. Consumption of tFDP was not associated with CRC (odds ratio (OR) 1.4; 95% Confidence interval (CI) 0.7–2.7; p = 0.34). Risk factors associated with CRC included age above 40 years, and consumption of processed meat and alcohol. Faecal carriage of Sii was significantly higher in persons with colon tumours and polyps compared to controls (8.4% vs 21.6%: OR: 4.6; CI 1.3–15.9). Patients with haemorrhoids represented an unexpected carrier group with significantly higher Sii faecal carriage (30.4%, CI: 17.7–45.8). Consumption of tFDP does not represent risk factors for CRC whereas Sii seems to be associated with CRC. However, there is urgent need to assess this finding also in the general population, investigate the causality of SBSEC, Sii and CRC as well as compare the phylogenetic, functional and genomic relationship between human and dairy Sii with regards to the ongoing application of Sii in FDP production.