Identification of Streptomyces spp. in a Clinical Sample: Always Contamination? Results of a French Retrospective Study

Abstract

Background Streptomyces are environmental Gram-positive bacilli that can cause ubiquitous mycetoma and, more rarely, invasive infections. We describe the clinical relevance of Streptomyces spp. identified in human samples and characteristics of patients with invasive Streptomyces infections. Methods We conducted a retrospective (2006-2017) study of Streptomyces isolates identified in clinical samples in French microbiology laboratories. Streptomyces genus was confirmed by a specific 16S rRNA PCR and antibiotic susceptibility testing was performed by disk diffusion and trimethoprim-sulfamethoxazole MIC (E-test) if resistance was suspected. Patient characteristics, treatment and outcomes were collected. Invasive infection was defined as a positive culture from a sterile site with signs of infection but without cutaneous inoculation. Results Of 137 Streptomyces isolates, all were susceptible to amikacin (113/113) and linezolid (112/112) and 92.9% to imipenem (105/113). Using disk diffusion, 50.9% (57/112) of isolates were susceptible to trimethoprim-sulfamethoxazole but most of apparently-resistant isolates (25/36, 69.4%) tested by E-test were ultimately classified as susceptible. Clinical data were obtained for 63/137 (45.9%) isolates: 30 (47.6%) invasive infections, 8 (12.7%) primary cutaneous infections, 22 (34.9%) contaminations, 3 (4.7%) respiratory colonization. Patients with invasive infection were more frequently receiving corticosteroids than patients without invasive infection (11/30, 36.7% vs 2/25, 8.0%, P = 0.03) and at 6-months follow-up, 14 of them were cured, three had relapsed, four were dead and nine were lost to follow-up. Conclusions Half of the clinical samples that grew Streptomyces were from patients with invasive infection. In that case, antimicrobial therapy should include one or two antibiotics among linezolid, amikacin or imipenem.

Streptomyces albireticuli lung infection managed as a pulmonary air cyst: a case report and literature review

“…They found that Streptomyces species were most susceptible to amikacin, gentamycin, vancomycin, and linezolid, and exhibited high susceptibility to tetracycline and clarithromycin, while showing intrinsic resistance to penicillin ( Kotrbová et al., 2022 ). Similarly, in two retrospective studies of human clinical samples, amikacin and linezolid covered 100% of the Streptomyces isolates ( Sáez-Nieto et al., 2021 ; Gras et al., 2022 ). Consistent with these studies, our AST results showed that the pathogen was sensitive to clarithromycin, amikacin, and linezolid.…”

“…Known for their ability to produce rich and diverse secondary metabolites, they have been widely used in clinical medicine ( Del Carratore et al., 2022 ). Despite the tremendous contributions of Streptomyces to medicine, they also pose risks as potential pathogens in humans, and particularly in immunocompromised patients ( Herbrík et al., 2020 ; Gras et al., 2022 ). Among the documented cases of Streptomyces infection, only a few have been described as clinical isolates relevant to humans ( McNeil et al., 1990 ; Gras et al., 2022 ).…”

“…Despite the tremendous contributions of Streptomyces to medicine, they also pose risks as potential pathogens in humans, and particularly in immunocompromised patients ( Herbrík et al., 2020 ; Gras et al., 2022 ). Among the documented cases of Streptomyces infection, only a few have been described as clinical isolates relevant to humans ( McNeil et al., 1990 ; Gras et al., 2022 ). Actinomycetoma is the most commonly observed infection caused by Streptomyces spp.…”

“…Additionally, Streptomyces can also cause rare invasive infections such as pulmonary infections and other diseases ( Herbrík et al., 2020 ; Bai et al., 2021 ). A retrospective study of Streptomyces isolates identified from clinical samples in French microbiology laboratories showed that nearly half of Streptomyces infections with complete clinical documentation were invasive ( Gras et al., 2022 ). Therefore, the significance of Streptomyces as opportunistic pathogens must not be overlooked.…”