We report a new case of Mycobacterium mucogenicum catheter related bloodstream infection, occuring in an immunocompromised patient. M. mucogenicum belongs to the group of rapidly growing mycobacteria, which are ubiquitous environmental organisms. Previously known as M. chelonae-like organism, M. mucogenicum finally changed name because of its phylogenetic distance from M. chelonae, but closeness to M. fortuitum and because of its mucoid colonies .
Infections caused by rapidly growing mycobacteria have been increasingly reported during the past few years because of improvement of isolation and identification techniques and spread of medical conditions compromising immune system [1, 5]. These microorganisms have been shown to cause various infections, including bacteremia. M. mucogenicum is the most common rapidly growing mycobacteria implicated in catheter related bloodstream infections [2, 3]. Like other rapidly growing mycobacteria, it has a high predisposition to create biofilm and colonise intravascular devises. Isolates appear as Gram-positive bacteria on Gram stain. Acid-fast stain is positive. M. mucogenicum can be cultivated in Lowenstein-agar but also in routine culture media within 7 days. The current gold standard for the identification of mycobacteria is DNA sequencing with 16sRNA gene, rpoB, and hsp65 being recognized as useful targets [6, 7]. But these methods are not affordable in many laboratories. Several investigators have demonstrated that MALDI-TOF mass spectrometry could accurately identify mycobacteria [8, 9]. Since treatment and response rates differ widely depending on the mycobacterial species, rapid identification is essential. Prompt identification to the species level can predict in vitro susceptibility and guide the choice of initial antibiotic therapy. Despite the possibility of contamination, recovery of M. mucogenicum from the bloodstream especially in immune-compromised patients should be considered as a true pathogen. Susceptibility testing is indicated for any rapidly growing mycobacteria considered clinically significant. M. mucogenicum isolates are usually susceptible to aminoglycosides, fluoroquinolones, tetracyclines, macrolides, carbapenems, cefoxitin, trimethoprim-sulfamethoxazole, and linezolid . Management of M. mucogenicum catheter-related bloodstream infections is mainly based on clinical experience. Optimal antibiotherapy is not established. In previously published case-series, an aminoglycoside combined with a macrolide and/or a quinolone was the most common empirical treatment [5, 11]. Optimal duration of treatment is unknown. At least 4 weeks of combination regimen were prescribed. But treatment may be prolonged in case of deep and persistent immunosuppression. Removal of the catheter is required to achieve successful outcome. Indeed, relapses have been associated with preservation of the catheter . The mortality rate was usually low [3, 11].