Laboratory cross-contamination of Mycobacterium tuberculosis in Northwest of Iran

Abstract

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.

Challenges of Tuberculosis in Iran

“…The results of several studies on the distribution pattern of strains in a few ethnic populaces have clarified the mechanism of transmission and factors related to the disease transmission (85,86). The data gathered in the present review will help us comprehend the dynamics of M. tuberculosis strains among different ethnic populations and geographic regions in Iran.…”

Detection of tuberculosis laboratory cross-contamination using whole-genome sequencing

“…Generally, if different clinical strains isolated at the same time from the same laboratory testing location are detected as having the same genotype, cross contamination is suspected, although additional evidence is needed to prove its occurrence. For example, in 1995, strains from three tuberculosis patients in Alabama, USA, from non-overlapping locations were identified by a single laboratory as having the same genotype, suggesting cross contamination may have occurred in that laboratory [16]. A similar event was reported for a tuberculosis laboratory in the northwest of Iran [17].…”

A rare case of sarcoidosis with necrotizing mediastinal lymphadenitis misdiagnosed as multidrug-resistant tuberculosis (MDR- TB)

“…[ 11 ] False-positive results of MTB smears, cultures, or molecular tests in bronchoscopically obtained samples are mainly due to cross-contamination owing to inadequate decontamination of bronchoscopes between use[ 12 ] or cross-contamination in the laboratory. [ 13 ] Xpert MTB/RIF (Cepheid) is a closed system which reduces the risk of cross-contamination. Therefore false-positive Xpert results after bronchoscopically obtained samples are possibly due to a result of inadequate decontamination of the bronchoscope.…”