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Journal of Clinical Microbiology, April 2008, p. 1246-1251, Vol. 46, No. 4
0095-1137/08/$08.00+0     doi:10.1128/JCM.01621-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Genetic Diversity of Mycobacterium avium Isolates Recovered from Clinical Samples and from the Environment: Molecular Characterization for Diagnostic Purposes

Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad Complutense de Madrid, 28040 Madrid, Spain,¹ Servicio de Urología, Hospital Virgen de la Salud, 45004 Toledo, Spain,² Servicio de Microbiología, Hospital Ramón y Cajal, IMSALUD, 28034 Madrid, Spain³

Received 14 August 2007/ Returned for modification 2 December 2007/ Accepted 4 February 2008

Isolation of Mycobacterium avium complex (MAC) organisms from clinical samples may occur in patients without clinical disease, making the interpretation of results difficult. The clinical relevance of MAC isolates from different types of clinical samples (n = 47) from 39 patients in different sections of a hospital was assessed by comparison with environmental isolates (n = 17) from the hospital. Various methods for identification and typing (commercial probes, phenotypic characteristics, PCR for detection of IS1245 and IS901, sequencing of the hsp65 gene, and pulsed-field gel electrophoresis) were evaluated. The same strain was found in all the environmental isolates, 21 out of 23 (91.3%) of the isolates cultured from urine samples, and 5 out of 19 (26.3%) isolates from respiratory specimens. This strain did not cause disease in the patients. Testing best characterized the strain as M. avium subsp. hominissuis, with the unusual feature that 81.4% of these isolates lacked the IS1245 element. Contamination of certain clinical samples with an environmental strain was the most likely event; therefore, characterization of the environmental mycobacteria present in health care facilities should be performed to discard false-positive isolations in nonsterile samples, mainly urine samples. Molecular techniques applied in this study demonstrated their usefulness for this purpose.

Published ahead of print on 13 February 2008.