A case report of catheter-associated bloodstream infection caused by the Mycobacterium fortuitum complex of two different strains that were in a colony form

Abstract

We report a case of catheter-associated bloodstream infection caused by the Mycobacterium fortuitum complex of two different strains that were in a colony form. The patient was a 61-year-old female, whose chief complaints were fever and lassitude. The blood culture became positive in four days of illness, and the Gram stain of the blood sample showed Gram-positive bacilli. Owing to our suspicion of Mycobacterium species, we conducted Ziehl–Neelsen staining, which revealed Mycobacterium species. The Mycobacterium species of two different strains that were in a colony form grew in 5% sheep blood agar, and both strains were detected from an encrustation (crust) on the central venous catheter surface and from the implantable central venous access port. The catheter-associated bloodstream infection caused by rapidly growing mycobacteria was suspected from the speed of growth. The two strains were identified as M. fortuitum by DNA–DNA hybridization and as a M. fortuitum complex by mass spectrometry. The results of susceptibility tests of both strains were the same. Treatment with Imipenem/Cilastatin (IPM/CS) and Amikacin (AMK) was continued for six weeks, after which, the patient’s symptoms resolved. The identification of the nontuberculous mycobacteria and the choice of the method for susceptibility tests are important. In intractable or rare nontuberculous mycobacteria cases, the information exchange with the doctor in charge is important.