Polymicrobial infections with specific Actinomyces and related organisms, using the current taxonomy

Abstract

<p><em>Actinomyces</em> organisms reside on mucosal surfaces of the oropharynx and the genitourinary tract. Polymicrobial infections with <em>Actinomyces</em> organisms are increasingly being reported in the literature. Since these infections differ from classical actinomycosis, lacking of specific clinical and imaging findings, slow-growing <em>Actinomyces</em> organisms can be regarded as contaminants or insignificant findings. In addition, only limited knowledge is available about novel <em>Actinomyces</em> species and their clinical relevance. The recent reclassifications have resulted in the transfer of several <em>Actinomyces</em> species to novel genera <em>Bowdeniella</em>, <em>Gleimia</em>, <em>Pauljensenia</em>, <em>Schaalia</em>, or <em>Winkia</em>. The spectrum of diseases associated with specific members of <em>Actinomyces</em> and these related genera varies. In human infections, the most common species are Actinomyces <em>israelii</em>, <em>Schaalia meyeri</em>, and <em>Schaalia odontolytica</em>, which are typical inhabitants of the mouth, and <em>Gleimia europaea</em>, <em>Schaalia turicensis</em>, and <em>Winkia neuii</em>. In this narrative review, the purpose was to gather information on the emerging role of specific organisms within the <em>Actinomyces</em> and related genera in polymicrobial infections. These include <em>Actinomyces graevenitzii</em> in pulmonary infections, <em>S. meyeri</em> in brain abscesses and infections in the lower respiratory tract, <em>S. turicensis</em> in skin-related infections, <em>G. europaea</em> in necrotizing fasciitis and skin abscesses, and <em>W. neuii</em> in infected tissues around prostheses and devices. Increased understanding of the role of <em>Actinomyces</em> and related species in polymicrobial infections could provide improved outcomes for patient care.<br></p>