Antimicrobial Susceptibility of Oral Actinomycetes From Hiv-Infected Patients Publisher



Bakhtiari A ; Fard R M N ; Doust R H H ; Shahedin G J
Source: Jundishapur Journal of Microbiology Published:2026

Abstract

Background: Actinomycetes can colonize the oral cavity of HIV-infected patients and may cause opportunistic infections. The use of commonly prescribed antimicrobials to treat these infections may contribute to the development of antimicrobia resistance (AMR). Objectives: This study aimed to assess the antimicrobial susceptibility of actinomycetes isolated from the oral cavities of HIV infected patients in Tehran, Iran. The susceptibility of the isolates to the essential oils (EOs) of thyme and ajwain was also evaluated. Methods: Samples were previously collected from 200 HIV-infected participants and 85 healthy participants using oral swabs and inoculated into thioglycolate media. The isolated bacteria were characterized phenotypically and genotypically. The antimicrobial susceptibility of the isolates to 14 antimicrobials was then assessed. In addition, the susceptibility of the isolates to the EOs of thyme and ajwain was evaluated. Results: Overall, actinomycetes were identified in 6.5% of HIV-infected patients and 3.5% of healthy controls. Most isolates were multidrug resistant (MDR) to amoxicillin, clindamycin, erythromycin, nalidixic acid, penicillin G, and tetracycline but were susceptible to gentamicin, ciprofloxacin, amikacin, linezolid, trimethoprim-sulfamethoxazole, and nitrofurantoin. All isolates were also susceptible to the herbal EOs. Conclusions: The findings demonstrated that the Actinomycetes isolates were MDR to several antimicrobials, including some listed by the World Health Organization (WHO) as first-line agents for treating major bacterial infections. This study highlights the importance of early diagnosis and appropriate treatment of Actinomycetes-associated infections and further suggests that the EOs of thyme and ajwain may be considered therapeutic options alongside conventional antimicrobial regimens. Copyright © 2026, Bakhtiari et al.