Computer-assisted analysis of Mycobacterium avium fingerprints using insertion elements IS1245 and IS1311 in a Caribbean setting

A total of 33 clinical isolates of the Mycobacterium avium complex from 25 patients, identified by means of biochemical and cultural characteristics, the Accuprobe system and DT1/DT6 PCR, were further analysed using novel insertion elements IS1245 and IS1311 in a French Caribbean setting. Pvull-cleaved DNA and non-radioactive Southern hybridization and detection systems were used for fingerprinting with both IS elements. The data confirmed the specificity of the two probes for M. avium in our setting and highlighted a significant proportion of M. intracellulare-infected patients in this region. Two distinct groups composed of 2-3 bands and 6-27 bands were found among M. avium isolates, and were composed of the same isolates both with IS1245 and IS 1311. The computer analysis of polymorphic banding patterns identified two prevalent genotypes: one contained 4 isolates from 3 patients while a second 2-banded cluster was composed of 6 isolates from 4 patients; all the patients were from the same hospital in Guadeloupe. A single isolate from Martinique was falsely included in the 2-banded cluster initially upon IS 1245 fingerprinting, but could be discriminated from other isolates on the basis of IS 1311 fingerprinting of Pvull-cleaved DNA. These results were also confirmed upon IS 1245 fingerprinting of Pstl-digested DNA, as well as DT6 fingerprinting. A single case of polyclonal infection was also discovered in a patient at a 75-day interval. This is the first study comparing the two IS elements and constitutes a first description of dissseminated M. avium complex disease from the Caribbean. We conclude that both elements possess a similar discriminatory potential for M. avium isolates. Coupled with computer analysis, this methodology would appear to be particularly suitable for larger epidemiological studies.