We took 150 clinical specimens from patients ranging in age from 7 to 65 years old who were suffering from gingivitis, dental caries, and dental plaque. Of these, 70 were male and 80 were female. Among the specimens tested, 124/150 (82.7%) showed positive culture on both blood agar and MacConkey agar, while 26/124 (17.3%) showed no growth on MacConkey agar. The results of the culture showed that 72/124 (58.1%) isolates belonged to Enterobacteriaceae, and 44/124 (35.5%) specimens belonged to other Gram-negative bacteria. The results of the culture on blood agar showed 6/124 (4.8%) isolates belong to coagulase-negative staphylococci, and 2/124 (1.6%) isolates belong to coagulase-positive staphylococci. K. pneumoniae and E. cloacae isolates were diagnosed according to cultural and biochemical tests as well as the final among bacterial isolates, K. pneumoniae 26 (32.5), which was detected phenotypically resistant to some antibacterial agents after being isolated and identified from clinical samples of the mouth. From clinical samples of the mouth, 26 (32.5%) of the bacteria tested positive for K. pneumoniae, and phenotypic testing revealed that these bacteria exhibited resistance to at least one antibiotic. A large percentage of K. pneumoniae isolates showed positive responses to piperacillin-tazobactam (88.8%), colistin (66.6%), and ticarcillin (88.8%). The rate of resistance to trimethoprim-sulfamethoxazole was moderate, at 44.4%. Most of the people who were resistant to Cefepime (33.3%), Aztreonam (22.2%), Gentamicin (22.2%), Ceftazidime (11.1%), Meropenem (0%), and Imipenem (0%), were also resistant to Levofloxacin (0%), Ciprofloxacin (0%), Amikacin (0%), and Tobramycin (0%). The fimH gene, which codes for fimbria type 1, helps K. pneumoniae isolates make biofilms. In 11/14 isolates (78.8%), the gene was found to be increasing.