Laboratory cross-contamination of Mycobacterium tuberculosis in Northwest of Iran

Introduction: Gold standard method for Mycobacterium tuberculosis identification is microbial culture, but this method can cause cross-contaminations. In the present study we aimed to investigate possible cross-contaminations in two main tuberculosis laboratories in Northwest of Iran. Methods: One hundred and fifty-six isolates from two central tuberculosis laboratories were investigated by IS6110-RFLP and VNTR-ETR methods. Results: 53 isolates were clustered in 18 clusters. 15 isolates were smear negative and single culture positive among which four isolates were suspected to be contaminated and in two isolates (1.28%) contaminations were confirmed. Conclusion: With this confirmation clustered isolates reduced from 53 isolates to 49 isolates and recent transmission rate of tuberculosis reduced to 21.2%. This study showed genotyping smear negative and single culture positive isolates can prevent unnecessary treatments and for this purpose VNTR-ETR is a suitable method.