Abstract
Background: Oral infections are known to be highly polymicrobial, but growing rates of antimicrobial resistance (AMR) are leading to reduced efficacy of treatment, especially in South Asia, due to widespread avalability of non-prescription antibiotics. Objectives: To establish the pathogens involved in oral infections and their antibiotic resistance patterns to penicillin, linezolid, vancomycin, gentamycin, moxifloxacin, and TMP-SMX. Methods: In this experimental cross-sectional study carried out at the Laboratory of Khyber Medical University Institute of Health Sciences, Swabi from December 2025 to May 2026, oral swabs were collected from 153 patients having clinically diagnosed cases of oral infection. Bacterial cultures were grown on blood and MacConkey agars; their identification was done based on colony morphology and Gram stain reaction, while antibiotic resistance was determined using disc diffusion technique. Results: Total of ten bacteria were isolated, among which gram-negative bacteria were more commonly isolated than the gram-positive ones (greater than 57% prevalence rate). *Prevotella intermedia* and *Staphylococcus aureus* were the most common bacteria isolated (both at 14.4%), followed by *Streptococcus viridans* (13.1%) and *Tannerella forsythia* (11.1%). Antibiotic resistance rates were high; linezolid was the most sensitive antibiotic (30.7%) but vancomycin showed maximum resistance (27.5%). Only 22.2% isolates were sensitive to penicillin. Lowest resistance rates were observed in gentamycin (20.3%), but significant rates of intermediate susceptibility were observed in it too. Both moxifloxacin and TMP-SMX exhibited very poor antibiotic sensitivity rates (less than 25%). Most of the infections were present in middle-aged individuals; males were slightly more common. Conclusion: Pathogens of oral infections exhibit a high degree of AMR, which is compromising the antibiotic treatment efficacy. Penicillin cannot be reliably used any more for treating such infections. Culturing prior to starting empirical antibiotic treatment is a must