Mycobacterium Immunogenum is a rapidly growing mycobacterium(RGM) which closely resembles M. abscessus & M. chelonae. RGM have increasingly been reported to cause disease in the transplant population. M.Immunogenum, however, is infrequently described in transplant recipients, and the true incidence of infection with this organism remains unknown. The pathogenicity and clinical significance of M.Immunogenumis therefore controversial.
We retrospectively reviewed 29 patients(pts) with cultures growing M. Immunogenum from 11/2011 to 6/2014 at UTSW Medical Center. The primary aim was to determine signs/symptoms, risk factors, and clinical outcomes; hence establishing whether M. Immunogenum are clinically significant in these pts.
29 pts with positive cultures were identified. 19/29(65.5%) pts with solid organ transplant & 4/29(14%) pts with autoimmune disease requiring immunosuppression.
Sources were from bronchial wash 21 pts (72.5%), bronchioalveolar lavage 3 pts(10%), Sputum 3 pts(10%), peritoneal fluid 2 pts(7%) and bronchial biopsy, stool & chesttube drainage in 1 each. 23/29 pts had bronchoscopy. In 11/23 pts bronchoscopy was done for routine post-transplant screening & 12/23 pts it was done because of either symptoms or abnormal imaging. 19/ 23(83%) pts underwent repeat bronchoscopy without treatment & only 2 pts grew M.Immunogenumin repeat bronchial specimen culture. Only 3/29(10%) pt was treated. 7/29 isolates were tested for sensitivity.
All-cause mortality rate was 31% & 6 month hospital readmission rate was 45%. It should also be noted that there was a pseudo epidemic of M. immunogenum and M.Aerupense within the similar time period that was traced to ice-machine water used to lower the temperature of syringes of saline that were instilled into bronchoscopic ports to achieve hemostasis.
In our limited retrospective series, only 3 pts who had Mycobacterium immunogenum was considered clinically significant requiring treatment meaning most of the isolates were considered nonpathogenic or “contamination”. Since this was a small retrospective case series, it would be uncertain to determine whether the presence of M. Immunogenum contributed to their overall clinical picture or whether their underlying comorbid conditions increased their risk for acquiring M. Immunogenum.
J. P. Luby, None
F. Lee, None
R. Gander, None
R. Portinari, None
D. Arocha, None