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

Background and Aims 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. Methods 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 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%). Conclusion 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.