Actinomyces are rod-shaped gram-positive bacteria that are part of the normal microbial flora of oropharynx, gastrointestinal and female genital tracts. Actinomyces tend to cause infections that are chronic and produce abscess, inflammation, and fibrosis. Most common sites of infection are in the face and neck region followed by lung. In the study in this issue by Farazmand et al,1 the authors describe a retrospective descriptive case series on actinomycosis in cancer patients in a single academic medical center. Sixty-five patients were selected based on positive culture or molecular identification for Actinomyces from 2000 to 2017. Of 65 patients, 46 were deemed to have true disease, and 19 were deemed to be either colonization or contamination. Pulmonary actinomycosis was the major clinical presentation in 33 of 46 patients. Actinomyces odontolyticus is the most common species followed by Actinomyces israelii. Lung cancer was present or diagnosed soon after the diagnosis of pulmonary actinomycosis in 10 patients. The authors have described in detail the clinical presentation and radiologic features of pulmonary actinomycosis. Common presenting symptoms were shortness of breath, cough, and fever. Most common radiological features were nodules and consolidation. Interesting aspect of this study is the observance of pulmonary actinomycosis as the predominant form unlike cervicofacial in general population. Three patients in this study had positive positron emission tomography/computed tomography scans in the absence of cancer, highlighting the need to keep pulmonary actinomycosis in the differential diagnoses for positron emission tomography/computed tomography scan–positive nodules. β-Lactam antibiotics are the drugs of choice in treating actinomycosis, and the duration varies greatly. Distinguishing colonization from true infection is difficult in actinomycosis. In this study, the most important factor when a positive culture was deemed a colonizer was patient symptoms in relation to their disease process. Colonization versus true disease question is even more complicated in scenarios when Actinomyces are seen with other bacteria or fungi in culture results. In this study, other bacteria were isolated with Actinomyces in 22 samples and fungi in 25 samples. This presents a complex scenario whether to treat. Because of the lack of established guidelines, I believe an individual physician's previous anecdotal cases play a major part in the physician's decision making. I think this decision is complex and should be made after weighing in patient symptoms, examination findings, radiological features, and immune status.
1. Farazmand C, Klinkova O, Denham J, et al. Actinomycosis in cancer patients: a single-center chart review study. Infect Dis Clin Pract