Cervical lymphadenitis caused by Mycobacterium lentiflavum

We report a case of human infection caused by Mycobacterium lentiflavum and review the literature for infections caused by this bacterium. The patient was a 19-month-old boy with involvement of a cervical lymph node. Surgical removal of the lymphadenopathy was both diagnostic and curative. Mycobacterium lentiflavum is a recently described slowly growing species of mycobacteria that is phylogenetically related to Mycobacterium simiae. 1, 2 Since its description only a few cases of clinical disease have been described in the literature. 3, 4 Here we report a new case of disease and review our data and the literature about this species. Between January 1, 2000, and June 30, 2001, nontuberculous mycobacteria were isolated in our laboratory in 83 clinical samples. Among these samples 3 (3.6%) from 3 patients were identified as M. lentiflavum by using common biochemical tests and PCR-restriction fragment length polymorphism analysis. 1 All strains were hybridized with the commercial DNA probe for the Mycobacterium avium complex (ACCUPROBE; bioMérieux, Marcy l’Étoile, France) and gave negative results. The clinical charts of the patients with the three isolates were reviewed. In two (strains isolated from bronchoalveolar lavage and skin biopsy), the isolate was nonsignificant. Both cases were acid-fast stain-negative, and the strain grew in scanty amounts. The third case was considered significant. Case report. The patient was a 19-month-old boy with asthma being treated with terbutaline. He developed multiple bilateral submandibular lymph nodes that had been growing for 10 days, one on the right side being larger than the others. No fever or constitutional symptoms were observed. Therapy with amoxicillin/clavulanic acid was started. After 15 days of therapy a large node increased in size and became fluctuant, resulting in surgical extirpation of the lymph node. Histopathologic analysis of the lymph node revealed lymphadenitis with granulomatous inflammation and microabscess formation. Ziehl-Neelsen stain revealed the presence of acid-fast bacilli. Antituberculous treatment was then inaugurated with isoniazid, rifampin and pyrazinamide. Culture of the material gave abundant growth of a slowly growing, yellow mycobacterium that was identified as M. lentiflavum. The strain was resistant in vitro to all first line antituberculous drugs (Canetti’s proportion method). After the surgery the patient recovered uneventfully. Discussion. Nontuberculous mycobacteria are a well-known cause of cervical lymphadenitis. Among the most commonly isolated species are M. avium and Mycobacterium intracellulare, 5 but other species like Mycobacterium haemophilum, Mycobacterium celatum, Mycobacterium malmoense, Mycobacterium interjectum and even M. lentiflavum have also been described as the cause of this syndrome. 3 In our case, as in those previously described, the short duration of the disease was remarkable and also the fact that cure was achieved with surgery and conventional antituberculous therapy, despite in vitro resistance against these agents. Only a few cases of human disease caused by M. lentiflavum have been reported. The first case described 1 was a 85-year-old woman with spondylodiscitis that was treated with conventional antituberculous therapy with improvement of her symptoms. The second and third case 3 were two children (42 and 33 months of age) with lymphadenitis who were treated surgically. Other cases of human isolates of M. lentiflavum from different samples have been described, 1, 2 but without clinical significance. In conclusion, M. lentiflavum is a species of mycobacterium described mainly as cause of lymphadenitis in children. The need of genetic techniques for identification of these strains suggests that perhaps its role in human diseases is underestimated and that new syndromes could be described as these techniques become available to routine clinical microbiology laboratories.