An investigation by Robyn Carter

Mycobacterium avium Complex (MAC) is a group of opportunistic pathogenic bacteria which includes M. avium and M. intracellulare. MAC organisms, particularly M. intracellulare, are a significant cause of pulmonary infections in older patients, often in the presence of underlying lung disease. When compared with M. avium, M. intracellulare is more often isolated from immuno-competent patients. Treatment of non-tuberculous mycobacterial diseases is problematic because of the resistant nature of the organisms. The disease may be an infection with the same organism or chronic disease with multiple strains. Reinfection with a new strain after successful treatment can occur. As the organisms are found in the environment, there is the potential for patients to continue to acquire the organisms from their environment. M. intracellulare is commonly isolated in respiratory isolates at Queensland Mycobacterium Reference Laboratory (QMRL) and there is an increasing incidence of infections due to M. intracellulare. By developing a genotyping strategy, it would be possible to define isolations as colonisation, chronic infection or re-infection, thereby contributing to decisions regarding treatment. When polyclonal infections are present, further costly investigations and treatment could be avoided. There would also be the possibility of determining the source of the infection by the comparison of clinical and environmental genotypes.  Variable Number Tandem Repeat-Mycobacterial Interspersed Repetitive Unit (VNTR-MIRU) and High Resolution Melt (HRM) have been shown to be discriminatory genotyping strategies for mycobacterial species and they have been investigated in this study.