Molecular strain typing of Mycobacterium tuberculosis isolates to detect cross-contamination events. Proposed modifications to prevent its recurrence.
OBJECTIVE
To investigate possible cross-contamination events of Mycobacterium tuberculosis cultures, and also to shed light on cross-contamination problems in our laboratories.


METHODS
At the TB Research Unit in the Department of Comparative Medicine Research Centre of King Faisal Specialist Hospital and Research Centre, Riyadh, Kingdom of Saudi Arabia, we received 22 TB isolates sub-cultured on Lowenstein-Jensen media from a local laboratory in Riyadh on 1st July 2005. We finger printed all 22 isolates in question using a polymerase chain reaction-based spoligotype molecular technique. The epidemiological and clinical data were reviewed.


RESULTS
All 22 cases had been proven to be cross-contaminated as a result of processing all specimens using a contaminated buffer. All of these patients had no clinical course consistent with tuberculosis. The discordant clinical pictures, and a deoxyribonucleic acid fingerprint that matches those of other culture-positive specimens processed concurrently, in addition to a lack of an epidemiological link between the patients suggest cross-contamination events.


CONCLUSIONS
Using molecular techniques has become an absolute necessity to detect cross-contamination events in our laboratory, to prevent the deleterious consequences of cross-contamination in patients.
Al-Hajoj
Sahal A
SA
Department of Comparative Medicine, King Faisal Specialist Hospital & Research Centre (MBC 03), PO Box 3354, Riyadh 11211, Kingdom of Saudi Arabia. hajoj@kfshrc.edu.sa
D006801:Humans; D007753:Laboratories; D008828:Microbiological Techniques; D009169:Mycobacterium tuberculosis / Q000145:classification* / Q000235:genetics; D011786:Quality Control