2010 Comprehensive review (PubMed).
Gram positive branching rods; includes A. israelii as the most common human pathogen but includes A. cardiffensis, A. europaeus, A. funkei, A. gerencseriae, A. graevenitzii, A. houstonensis, A. lingnae, A. meyeri,A. naeslundii/viscosus complex, A. neuii, A. odontolyticus, A. radingae, A. turicensis, Arcanobacterium (Actinomyces) bernardiae, Arcanobacterium (Actinomyces) pyogenes. Infections are more often than not polymicrobial.
It can be slow/difficult to grow so if worried about it let the microbiology department know.
Part of the human GI tract, often disease occurs with poor dentition (lumpy jaw), aspiration pneumonia/lung abscess (most commonly), and trauma (abdominal/uterine infections).
Actinomyces are everywhere in the environment and help plant material rot.
There a huge number of species that can be found in a variety of human organs and diseases (PubMed).
A. israelii: Lumpy jaw, empyema, lung abscess, abdominal and uterine infections (usually due to an old IUD. Some IUD's can be left in for years and they can wander, perforating the uterous) as well as the odd other organ infection. These infections are indolent and often present like a malignancy.
If you are concerned about lumpy jay, make sure the pathologist does the proper histopathology: "Twelve serial sections for each case were cut from the paraffin blocks, individually collected on positively charged slides to obtain good section-to-slide adhesion, and stained with hematoxylin and eosin (H&E) and periodic acid-Schiff (PAS). Histopathological examination of the serial sections allowed the identification of bacterial colonies consistent with actinomycetes in 22 cases (32 %). The proposed histopathological examination allowed the retrospective diagnosis of cervical actinomycosis in one-third of clinical specimens that remained misdiagnosed following traditional H&E examination (PubMed)."
The non- A. israelii spp, like A. turicensis, A. radingae, and A. europaeus, can cause of a variety of infections (PubMed). They are associated with balanitis, urethritis, prostatitis, a variety of female -itisis, UTI, soft tissue infections, some gi infections and rarely bacteremia.
The odd Actinomyces have variable sensitivities. (PubMed).
NotesA. israelii causes the so called sulfur granules (which are masses of the organism, not sulfur) and the organism likes to track through, rather than along, tissue planes, so it tends to pop out and drain in unexpected places. On exam, lumpy jaw really does feel like balsa wood.
Relevant links to my Medscape blog
Last Update: 04/27/18.