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Disseminated Mycobacterium genavense infection in two patients with AIDS
C D Gaynor1, R A Clark, F P Koontz
1Department of Medicine, University of Iowa Hospitals and Clinics, Iowa City 52242.
Abstract:
Mycobacterium genavense is a recently defined fastidious organism that has been identified as a cause of disseminated infection in patients with AIDS. We report the cases of two patients who had advanced AIDS and a clinical syndrome of fever, anorexia, abdominal pain, diarrhea, and weight loss. In addition, splenomegaly and lymphadenopathy were prominent in both cases, and in one patient's case radiographic findings were suggestive of splenic abscesses. Mycobacteria isolated from specimens of blood and bone marrow grew in liquid media but not on solid media. The results of DNA probe tests for Mycobacterium tuberculosis and Mycobacterium avium complex were false-positive for both patients. After treatment of the broth cultures to lyse red blood cells, the results of DNA probe tests were negative for these pathogens. Amplification and sequencing of 16S rRNA with use of the polymerase chain reaction indicated that the mycobacterial isolates from both patients had sequences identical to those previously reported for M. genavense. One patient survived 5 months after diagnosis, the other 2 months after diagnosis; only one patient responded (transiently) to antimycobacterial chemotherapy.
Insights
Two AIDS patients developed disseminated infections with Mycobacterium genavense, a fastidious bacterium. Diagnosis was challenging due to false-positive tests for other mycobacteria, highlighting the need for advanced molecular methods.
Area of Science:
- Infectious Diseases
- Microbiology
- Molecular Biology
Background:
- Mycobacterium genavense is an emerging pathogen causing disseminated infections in immunocompromised individuals, particularly those with advanced Acquired Immunodeficiency Syndrome (AIDS).
- Accurate and timely diagnosis of mycobacterial infections is crucial for effective patient management, especially in vulnerable populations.
Observation:
- Two patients with advanced AIDS presented with severe constitutional symptoms including fever, anorexia, abdominal pain, diarrhea, weight loss, splenomegaly, and lymphadenopathy.
- Initial diagnostic attempts using standard DNA probe tests for Mycobacterium tuberculosis and Mycobacterium avium complex yielded false-positive results.
- The causative agent, Mycobacterium genavense, was isolated from blood and bone marrow specimens, growing only in liquid media.
Findings:
- Polymerase chain reaction (PCR) amplification and 16S rRNA sequencing confirmed the presence of Mycobacterium genavense, identifying sequences identical to previously reported strains.
- False-positive DNA probe results were attributed to the presence of red blood cells in the initial cultures, which became negative after lysis.
Implications:
- This case series underscores the diagnostic challenges posed by Mycobacterium genavense in AIDS patients and the limitations of conventional diagnostic methods.
- Advanced molecular techniques like PCR-based sequencing are essential for accurate identification of fastidious mycobacteria.
- The findings highlight the need for improved diagnostic strategies to facilitate earlier treatment and potentially better outcomes for patients with disseminated M. genavense infections.