Mycobacterium thermoresistibile: case report of a rarely isolated mycobacterium from Europe and review of literature

Disseminated Mycobacterium thermoresistibile Infection presented with Lymphadenectasis in an AIDS patient: case report and review of literature

BACKGROUND

Nontuberculous mycobacteria disease is a common invasive infectious disease in patients with HIV. However, Mycobacterium thermoresistibile association with lymphadenectasis is unusual in AIDS patients.

CASE PRESENTATION

This report covers the case of a 25-year-old male AIDS patient infected with Mycobacterium thermoresistibile. The case was identified via pathogen-targeted next-generation sequencing (ptNGS).

CONCLUSION

This is the first report of disseminated M. thermoresistibile infection presented with lymphadenectasis in an AIDS patient. Prompt diagnosis and antimicrobial treatment are crucial.

Case of flexor tenosynovitis caused by Mycobacterium arupense

Mycobacterium arupense is a member of the Mycobacterium terrae complex (MTC) that is implicated in bone and joint infections, among others. This group of environmental pathogens can be found in soil, reclaimed and drinking water systems, rodents, fish tanks and bioaerosols in duck houses. Interestingly, while M. arupense is genotypically closely related to the other agents in the MTC, antibiotic susceptibility of these mycobacteria can vary widely and empiric antibiotic therapy is controversial. Our case report contributes to the very limited literature on M. arupense tenosynovitis-as only six cases have been reported since 2008-and sheds light on different courses of treatment. While previous cases have been successfully treated, a streamlined course of therapy for M. arupense tenosynovitis is still needed.

Mycobacterial panniculitis caused by Mycobacterium thermoresistibile in a cat

CASE SUMMARY

A domestic shorthair cat was evaluated for chronic, bilateral, ulcerative dermatitis affecting the inguinal region and lateral aspects of both pelvic limbs. Histopathologic examination of skin biopsies collected throughout the course of disease revealed chronic pyogranulomatous ulcerative dermatitis. Aerobic bacterial skin cultures yielded growth of a methicillin-resistant Staphylococcus aureus and Corynebacterium amycolatum. Upon referral the clinical findings were suggestive of a non-tuberculous Mycobacterium species infection. Previously obtained skin cultures failed to yield growth of mycobacterial organisms. A deep skin biopsy was collected and submitted for mycobacterial culture. At 5 weeks of incubation Mycobacterium thermoresistibile was isolated. In previous reports, M thermoresistibile has been isolated after 2-4 days of incubation, suggesting that this strain may have been a slower growing variant, or other factors (such as prior antimicrobial therapy) inhibited rapid growth of this isolate. The cat was hospitalized for intravenous antibiotic therapy, surgical debridement of wounds, vacuum-assisted wound closure therapy and reconstruction procedures. The wounds were ultimately primarily closed and the cat was discharged to the owner after 50 days of hospitalization. Seven months after hospitalization, the ulcerative skin lesions had healed.

RELEVANCE AND NOVEL INFORMATION

To our knowledge, only two cases of M thermoresistibile panniculitis have been reported in cats. In the only detailed report of feline M thermoresistibile panniculitis, treatment was not attempted. The second case only reported detection of M thermoresistibile by PCR without a clinical description of the case. In our case report, severe chronic skin infection with M thermoresistibile was addressed using prolonged specific antibiotic therapy, surgical debridement and reconstructions, and treatment of secondary bacterial infections.

Infection due to Mycobacterium thermoresistibile: a case associated with an orthopedic device

Mycobacterium thermoresistibile is a rapidly growing environmental nontuberculous mycobacterium, seldom reported in human infections. Here, we describe a rare case of tibial-nail-related osteomyelitis due to Mycobacterium thermoresistibile. We also review the literature about the infections caused by this pathogen.

Laboratory aspects of clinically significant rapidly growing mycobacteria

The pathogenic potential of the rapidly growing mycobacteria (RGM) has started being recognized. This is due to more sensitive and specific techniques in the laboratory. The RGM are generally defined as nontuberculous species of mycobacteria that show visible growth on agar media within 7 days. RGM are widely distributed in nature and have been isolated from natural water, tap water, and soil. Several biochemical tests, high performance liquid chromatography, and molecular techniques have been developed for rapid identification of these species. The American Thoracic Society and the Infectious Disease Society of America recommend that RGM should be identified to the species level using a recognized acceptable methodology such as polymerase chain reaction restriction enzyme analysis or biochemical testing and routine susceptibility testing of RGM should include amikacin, imipenem, doxycycline, the fluorinated quinolones, a sulphonamide or trimethoprim-sulphamethoxazole, cefoxitin, clarithromycin, linezolid, and tobramycin. The diseases caused by these organisms have varied manifestations. They have been responsible for a number of healthcare-associated outbreaks and pseudo-outbreaks. For recognition of outbreaks, it is important to be familiar with the causative organisms like RGM which are most frequently involved in healthcare-associated outbreaks and pseudo outbreaks. It is essential to intervene as soon as possible to interrupt this transmission. Large gaps still exist in our knowledge of RGM. Unquestionably more studies are required. Through this review, we wish to emphasize that reporting of RGM from clinical settings along with their sensitivity patterns is an absolute need of the hour.

Structure of nitrilotriacetate monooxygenase component B from Mycobacterium thermoresistibile

Mycobacterium tuberculosis belongs to a large family of soil bacteria which can degrade a remarkably broad range of organic compounds and utilize them as carbon, nitrogen and energy sources. It has been proposed that a variety of mycobacteria can subsist on alternative carbon sources during latency within an infected human host, with the help of enzymes such as nitrilotriacetate monooxygenase (NTA-Mo). NTA-Mo is a member of a class of enzymes which consist of two components: A and B. While component A has monooxygenase activity and is responsible for the oxidation of the substrate, component B consumes cofactor to generate reduced flavin mononucleotide, which is required for component A activity. NTA-MoB from M. thermoresistibile, a rare but infectious close relative of M. tuberculosis which can thrive at elevated temperatures, has been expressed, purified and crystallized. The 1.6 Å resolution crystal structure of component B of NTA-Mo presented here is one of the first crystal structures determined from the organism M. thermoresistibile. The NTA-MoB crystal structure reveals a homodimer with the characteristic split-barrel motif typical of flavin reductases. Surprisingly, NTA-MoB from M. thermoresistibile contains a C-terminal tail that is highly conserved among mycobacterial orthologs and resides in the active site of the other protomer. Based on the structure, the C-terminal tail may modulate NTA-MoB activity in mycobacteria by blocking the binding of flavins and NADH.