In this approach, a cariogenic strain is permanently implanted in the host microflora. Once established, the presence of this strain encourages the colonisation or growth of other pathogens. Objectives: The aim of this study is to isolate and identify the bacteria responsible for these carious infections (cariogenic bacteria) in the human oral cavity from samples taken in private dental practices in Bechar’s town. Methods: Participants completed a questionnaire and were clinically examined according to criteria set by the World Health Organisation. Dental caries samples were collected from 250 subjects with caries lesions. Conventional methods for culturing and identifying aerobic and anaerobic bacteria were used. Results: This shows that the Streptococcaceae and Lactobacillaceae are the families most represented in our samples. Streptococcus mutans is the most cariogenic organism in the oral microflora, due to a number of factors. The analysis of dental plaques of adults and infants with caries revealed the presence of 210 strains belonging to 7 genera of 4 aero-anaerobic (Streptococcus, Haemophilus, Gamella and Staphylococcus) and 3 anaerobic genera (Lactobacillus, Peptococcus, Peptostreptococcus) (P < 0.05). Nine (09) bacterial strains were isolated from dental caries, some of them belonging to an aero-anaerobic genus, others to an anaerobic genus. Streptococcus mutans (22%), Streptococcus intermedius (18%), Lactobacillus sp (15%), Streptococcus mitis 1 (12%), Peptococcus sp (10%), Haemophilus parainfluenzae (8%),Gamella morbillorum (6%) and Peptostreptococcus spp.(5%) and Staphylococcus aureus (4%) showed a significantly high prevalence in the group of subjects with carious teeth. Antibiotic sensitivity tests conducted on these microorganisms revealed confirmed resistance in some strains against (Azithromycin, Amoxicillin+ Clavulanic acid, Amoxicillin, Gentamycin, Amikacin, Streptomycin and Spiramycin) and marked sensitivity for other antibiotic (Tobramycin, Oxacillin, Tetracycline, Bacitracin) and as well as having chloramphenicol as an intermediate. Streptococci and lactobacilli are bacteria that can originate either internally or externally and can cause oral diseases such as dental caries, which is a public health scourge. Conclusion: The impact of dental pain and infection on quality of life also needs to be considered. Diseases of the oral cavity occur in a complex host-bacterial community interaction that often does not fit a single microbe pathogenesis model. This study corroborates that oral hygiene practices minimize the prevalence of dental caries.