Laboratory Analysis of Fecal Lactobacillus Strains and pH in Tobacco Smokers: A Comparative Study From a Developing...

Tobacco smoking is a major cause of preventable mortality globally, disproportionately impacting developing countries. While its systemic health effects are well-known, the influence of tobacco on gut microbiota-especially beneficial Lactobacillus species-remains poorly explored in resource-limited settings.

This study examined fecal Lactobacillus composition and stool pH among 200 participants from western Iran, including cigarette smokers, hookah users, combined users, and non-smoking controls. Standard microbiological methods were employed: stool pH measurement, anaerobic culture on MRS agar, Gram staining, biochemical tests, phenotypic assays (acid/bile resistance, antibiotic susceptibility), and PCR sequencing of the 16S rRNA gene for species identification.

Results showed significantly elevated stool pH in tobacco users, particularly hookah smokers (p = 0.001). Lactobacillus prevalence was markedly lower in all smoker groups compared to controls (p < 0.001). Dominant species identified were L. casei, L. plantarum, and L. acidophilus, with control strains exhibiting greater acid and bile tolerance (p < 0.05). Antibiotic resistance was common, notably to vancomycin (75%) and ampicillin (67%).

These findings indicate tobacco-associated gut dysbiosis characterized by increased stool pH and diminished Lactobacillus viability, potentially impairing gut barrier integrity. The study highlights the importance of clinical microbiological evaluation of smoking-related microbiota alterations, especially in populations with limited probiotic access.