Mycobacterium avium complex: Significance of isolation from bone marrow culture

Six patients with bone marrow cultures yielding Mycobacterium avium complex were encountered at the Mount Sinai Hospital between 1969 and 1976. One additional isolate of the same mycobacterial species was recovered from splenic cyst fluid of a seventh patient. Because none of the patients had illnesses apparently due to M. avium complex, the isolates were unexpected and unexplained. Six of the seven patients had other acute or chronic infectious processes, occurring alone or superimposed on a preexisting disease. These patients were therefore unusual, because nontuberculous mycobacteria have previously been obtained from bone marrow cultures exclusively in patients who had either disseminated or pleuropulmonary nontuberculous mycobacteriosis. The isolation of M. avium complex from the reticuloendothelial tissue of these seven patients may reflect an asymptomatic infection or alternatively may lack significance. Either premise can only be judged by continued careful evaluation of similar findings.