Mycobacterium xenopi Pneumonia in the Southeastern United States

Jihane A. Faress, MD, Lisa A. McKinney, DO, Maroun T. Semaan, MD, Ryland P. Byrd Jr., MD, Jay B. Mehta, MD, Thomas M. Roy, MD


South Med J. 2003;96(6) 

In This Article

Abstract and Introduction

Mycobacterium xenopi (M. xenopi) is a slow-growing, nontuberculous mycobacterium (NTM). This organism is found in fresh water and has been isolated in water samples collected from water systems in homes and hospitals. Before the acquired immunodeficiency syndrome epidemic, M. xenopi infection was infrequent and occurred in clusters; however, M. xenopi is now a recognized cause of pulmonary infection in immunocompetent patients with preexisting lung disease. The classic chest x-ray appearance is cavitary apical pulmonary disease, which mimics tuberculosis. M. xenopi is currently one of the most common NTM pathogens in parts of England and Canada and has been reported in parts of the northeastern United States. Whether the isolation of M. xenopi from our patient in Tennessee represents a new geographic distribution of this organism or technologic advancements that now allow for reliable identification is debatable. This case serves as a reminder to clinicians that the incidence of NTM infection is rising in the United States and that unusual NTM are capable of causing disease even in patients who are not immunocompromised.

The genus Mycobacterium contains more than 70 recognized or proposed species. These species can be divided into two groups based upon their growth rate in culture.[1] The slow-growing species require more than 7 days to form visible colonies on solid media, whereas the rapid-growing species require less than 7 days. Although there are important exceptions, the slow-growing species are often pathogenic in humans, whereas the rapid-growing species are usually considered nonpathogenic. Mycobacterium xenopi (M. xenopi) is a slow-growing, nontubercular mycobacterium (NTM). It is uncommon for it to be isolated from humans in the United States, but pulmonary infections caused by this organism have been recognized in patients residing in the Northeast.[2] Because infection from NTM is not a reportable disease in the United States, no reliable estimates of incidence or prevalence of M. xenopi infection are available.[3] Our patient represents the first case of M. xenopi respiratory infection to be reported from the southeastern United States and should alert clinicians that unusual NTM pulmonary infections can occur in immunocompetent hosts.


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