Oral <i>Actinomycetes</i> from HIV-Infected Patients in Tehran, Iran

Abstract

Background: Human immunodeficiency virus (HIV) is a member of the retroviral family. The virus infects human white blood cells, including macrophages, dendritic cells, and CD4 lymphocytes, thereby weakening the immune system if patients are not appropriately treated with antiviral agents. Subsequently, the disease progresses to acquired immunodeficiency syndrome (AIDS), with clinical manifestations caused by opportunistic microorganisms, including filamentous bacteria and other bacterial and fungal agents. Filamentous bacteria, or actinomycetes, include important environmental and medically relevant species. These bacteria constitute a major component of the oral microbiota, including that of the oropharynx, particularly in periodontal pockets, gingival grooves, tonsil crypts, and dental plaques. Objectives: The primary aim of this study was to isolate and phenotypically and genotypically characterize Actinomycetes from the oral cavity of HIV-infected participants. Methods: In this retrospective cross-sectional study, conducted from March 2022 to August 2023, buccal samples were collected from 200 HIV-infected participants at a university clinic and transported under cold-chain conditions to the microbiology laboratory at Tehran University of Medical Sciences, Tehran, Iran. Samples were cultured on appropriate media, and bacterial isolates were identified using microscopic, biochemical, and molecular assays. The antimicrobial susceptibility of the Actinomycetes was assessed against selected antimicrobials. In addition, the phylogeny of the isolates was analyzed using sequencing and bioinformatics tools. Results: Of 200 oral samples from HIV-infected patients, 19 Actinomycetes strains (9.5%) were isolated, including Streptomyces (n = 6), Nocardia (n = 6; all N. farcinica), Nocardiopsis (n = 6; including two N. alba), and Saccharopolyspora (n = 1) species. Most isolates were multidrug resistant, exhibiting resistance to beta-lactams such as penicillin G and amoxicillin/clavulanic acid, as well as erythromycin, tetracycline, nalidixic acid, and clindamycin. However, the isolates were largely susceptible to other antimicrobials. Conclusions: This study demonstrated a high prevalence of Actinomycetes, particularly Nocardia and Streptomyces spp., among HIV-infected patients. Accurate identification of Actinomycetes and determination of their antimicrobial susceptibility can effectively guide the treatment of oral ulcers, especially in patients infected with antimicrobial-resistant strains.