Catheter-Related Bloodstream Infection Caused by Mycobacterium mageritense

Mycobacterium mageritense is an uncommon cause of catheter-related bacteremia (1, 4).

We report a 26-year-old pregnant woman who presented with fever for 3 weeks. A tunneled central venous catheter (CVC) had been placed due to hyperemesis. The patient did not have any immunocompromised conditions. Blood cultures were performed by use of BACTEC Aerobic Plus and Anaerobic Lytic. Anaerobic cultures from both the central line and a peripheral site showed beaded gram-positive rods. The time to detection was 103 h. A modified acid-fast stain was highly suggestive of a nontuberculous mycobacterium (NTM) which was identified as Mycobacterium mageritense by DNA sequencing. Susceptibility studies performed by a broth dilution MIC method showed the organism to be susceptible to ciprofloxacin (MIC, 0.5 μg/ml) and trimethoprim-sulfamethoxazole (TMP-SXT) (MIC, 0.5 and 9.5 μg/ml, respectively) and resistant to amikacin (MIC, 128 μg/ml) and clarithromycin (MIC, >64 μg/ml). The breakpoints were determined according to standards of the Clinical and Laboratory Standards Institute (CLSI).

Intravenous TMP-SXT was initiated. The catheter was removed 1 week later, and the tip was cultured using the roll plate technique on sheep blood agar. No growth was observed after 5 days of incubation. The patient was treated for 2 weeks with intravenous TMP-SXT, with complete resolution of her symptoms.

To our knowledge, this is the second reported case in the literature of a CVC-related bloodstream infection due to Mycobacterium mageritense. The first reported case occurred in a 32-year-old immunocompromised woman who was treated with linezolid and amikacin.

Clinical disease produced by M. mageritense is uncommon and ranges from skin and soft tissue infection to health care-associated infections (4). It is a nonpigmented, rapidly growing mycobacterium, closely resembling the M. fortuitum third biovariant complex (2, 4). The source of M. mageritense in our case remains unclear.

Although bloodstream infection with NTM usually occurs in immunocompromised patients with CVC, our case occurred in a patient with no immunocompromised state. The catheter tip did not grow the organism, which may be due to the patient's prior antimicrobial therapy. Also, since this catheter was cultured using the roll plate technique (which detects only extraluminal colonization), intraluminal colonization, frequently seen with long-term catheters, was not detected. CVC infection is documented with a positive catheter tip in only 15 to 25% of cases with presumptive CVC-related infection. There are no treatment guidelines for NTM bloodstream infections. The decision to remove the catheter from our patient was based on previously reported cases of M. fortuitum bacteremia in which a high relapse rate was seen if catheters were not removed (3).

The susceptibility pattern of this isolate of M. mageritense resembles that of the M. fortuitum group. Given that isolates of M. mageritense have growth, biochemical, and drug susceptibility patterns of the M. fortuitum third biovariant complex, it has been postulated that M. mageritense might actually be a new taxon within the M. fortuitum third biovariant complex (2). Even though M. mageritense is a low-virulence organism usually not associated with clinical disease, this case illustrates the pathogenic potential of this organism in patients with long-term indwelling catheters.