Analysis of the diversity of Actinomyces/Actinotignum clinical isolates in a university hospital

Actinomyces and related genera are grampositive bacilli, opportunistic pathogens, which have been mainly involved in endogenous infections. However, due to the complexity in identifying them for most clinical laboratories, there is scant knowledge about their real clinical significance. In this work, 166 isolates of 13 different species of Actinomyces/Actinotignum species recovered from clinical samples of patients treated in a university hospital were studied. The identification was performed by MALDI-TOF MS and molecular identification. MALDI-TOF MS identified 91.57% of the isolates (152/166) at the species level using a score > 1.7 and 3.61% (6/166) of the isolates were identified only at the gender level with a score > 1.5. MALDI-TOF MS did not yield reliable identification results for 4.82% (8/166) of the isolates. Actinomyces/Actinotignum species were isolated from: soft tissue (n: 47), urine samples (n: 35), head / neck abscesses (n: 19), genital abscesses (n: 11), blood samples (n: 10), breast abscesses (n: 8), osteoarticular samples (n: 6), abdominal/ascitic fluids (n: 3), abdominal abscesses (n: 5), sputum/BAL (n: 4), brain abscesses (n: 3), and others (n: 15). The results obtained from the statistical analysis showed a high differential frequency (> 2) for the location/species association: urine/A. schaalii/sanguinis; brain abscesses/A. europaeus; osteoarticular samples/A. urogenitalis; abdominal abscesses/ A. turicensis; respiratory samples/A. naeslundii/viscosus. This information provides a greater understanding of the clinical and epidemiological relevance of these species. The pathogenic role of Actinomyces spp. will be increasingly revealed as these microorganisms could be recognized thanks to prolonged culture and the advances in identification technology facilitated by MALDI-TOF MS. (c) 2020 Asociacion Argentina de Microbiologia. Published by Elsevier Espana, S.L.U. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).