SESSION TYPE: Infectious Disease Case Report Posters I
PRESENTED ON: Tuesday, October 23, 2012 at 01:30 PM - 02:30 PM
INTRODUCTION: M. interjectum rarely causes disease in immunocompetent adults.
CASE PRESENTATION: A 64 years-old, male smoker presented with night sweats, weight loss and productive cough. Chest CT scan showed an 8.6x5.9 cm. cavity and tree-in-bud opacities in the right lung. A sputum sample was negative for M. tuberculosis by RNA amplification analysis and Quantiferon-GOLD test was negative. Mycobacterium avium intracellulare was detected 3 months after onset of symptoms and azithromycin, ethambutol and rifampim were begun. Physical examination was normal and the patient was afebrile and eupneic at presentation to our clinic 3 days later. Bronchoalveolar lavage smears were positive for acid fast bacilli. Mycobacterium interjectum was repeatedly identified through DNA sequencing and Scopulariopsis spp developed in culture. The initial susceptibility testing at an outside facility showed that M. interjectum was sensitive to rifampin, ethambutol, clarithromycin and streptomycin and resistant to ciprofloxacin. Suceptibility testing done at our hospital differed from the above in that the isolate was resistant to Ethambutol and sensitive to Trimetoprim/Sulfamethoxazole and amikacin. Treatment was modified based on these results. HIV serology was negative. Resolution of symptoms and radiological improvement followed. Sputum became negative for acid fast bacilli 4 months after treatment initiation without fungal growth. Continued therapy with rifampin, ethambutol, clarithromycin and Trimetoprim/Sulfamethoxazole for one year after negativization of sputum for mycobacteria is planned.
DISCUSSION: M. interjectum was first described in 1993 causing cervical lymphadenitis in toddlers. It has also been isolated in immunosuppressed patients. Most pediatric cases failed antibiotic therapy and required resection for cure. Only 2 cases of cavitary lung disease (CLD) in immunocompetent adults have been reliably described. The first was a 52 years-old woman with progressive destructive lung disease refractory to antibiotics. Another case of CLD mimicking tuberculosis responded to 7 months of antibiotic therapy. M. interjectum is similar phenotypically to M. scrofulaceum and M. gordonae. Diagnosis requires sequencing of the 16S rRNA and prior susceptibility testing has demonstrated multidrug resistance. To our knowledge, ours is the third described case of M. interjectum destructive lung disease in an immunocompetent adult. It is possible that many cases of M. interjectum lung disease have been misdiagnosed as other non-tuberculous mycobacteria and that the prevalence is higher than previously suspected.
CONCLUSIONS: The clinician should remain alert to the possibility of M. interjectum CLD as empiric treatment may require a more aggressive initial approach. The advent of 16s rRNA sequencing will certainly prove useful for earlier diagnosis.
1) Am J Tuberc Lung Disease.2009.13(8);1048.
DISCLOSURE: The following authors have nothing to disclose: Maria Mirant-Borde, Jose Soto Soto, Margaret Johnson
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