Emergence of multidrug-resistant Mycobacterium fortuitum during treatment

We present a case of pulmonary infection with Mycobacterium fortuitum demonstrating the development of multidrug resistance during therapy with multiple drugs. Emergence of drug resistance in a previously sensitive M fortuitum has been described with single drug therapy, but never before with multiple drug treatment. Development of resistance in the setting of multiple drug therapy illustrates the importance of repeated susceptibility testing during therapy.