Actinomyces Species As Emerging Pathogens: An Observational Study of Clinical Infections and Microbiological...

Actinomyces species, Gram-positive filamentous anaerobic microaerophilic organisms, are commensals of the human oropharynx, gastrointestinal, and urogenital tracts. Actinomycosis is rare and occurs when tissue integrity is compromised, typically in a polymicrobial fashion. There is an emerging rise in Actinomyces species-associated infections, with attendant therapeutic challenges.

We evaluated the pattern, presentation, and risk factors for Actinomyces species-associated infections.

Blood culture, tissue, fluids, bone, and swab samples with isolated Actinomyces species were evaluated between July 2016 and April 2021. The antibiotic susceptibility of the isolated Actinomyces was obtained as per the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. Electronic medical records were retrospectively evaluated for demographic and clinicopathological data relating to the patients.

A total of 145 patients were evaluated, comprising 63 males and 82 females; the mean age was 49 years. About 52.4% and 59.3% of comorbidities and risk factors for Actinomyces species infection susceptibility, respectively. The most common presentations were infected sebaceous cysts (25.5%) and pilonidal abscesses (13.8%). Actinomyces species were isolated from swabs (78), pus (32), blood cultures (26), body fluids (6), soft tissues (2), and bone fragments (1). Eleven different Actinomyces species were isolated, and commonly isolated species were Actinomyces neuii (24.8%), Actinomyces turicensis (22.8%), and Actinomyces europaeus (13.8%). About 57.2% of the samples had mixed microorganisms isolated; 26 of 29 blood culture samples yielded Actinomyces, and 6 of 29 yielded mixed microbial agents. A majority (78.6%) of the patients received empirical antibiotics, and 79% of the antibiotic choice was appropriate. Conclusion​​​​​: Actinomyces species isolates and infections are increasingly reported, potentially attributed to improved culture techniques. We recommend epidemiology and resistance surveillance in Actinomyces species-associated infections.