RETROSPECTIVE DETECTION OF LABORATORY CROSS-CONTAMINATION OF MYCOBACTERIUM-TUBERCULOSIS CULTURES WITH USE OF DNA FINGERPRINT ANALYSIS

In 1992-1993, we investigated possible cross-contamination of Mycobact erium tuberculosis cultures as part of a study of tuberculosis in Arka nsas by using DNA fingerprint analysis. Of patients whose isolates wer e matched, those for whom smears were negative and only one culture wa s positive were identified from laboratory records, Clinical, laborato ry, DNA fingerprint, and epidemiological data were reviewed, Of 259 pa tients, nine (3.5%) were judged to be due to cross-contamination. None of these patients had a clinical course consistent with tuberculosis. All nine specimens were processed with another isolate with a matchin g DNA fingerprint, and epidemiological connections were not identified among any of the patients. To avoid erroneous diagnoses and unnecessa ry therapy and public health investigations, specimens from patients w ith tuberculosis whose smears are negative and only one culture is pos itive should be investigated for cross-contamination, An inconsistent clinical course and a DNA fingerprint that matches those of other cult ure-positive specimens processed concurrently, coupled with the lack o f an epidemiological connection, suggest cross-contamination.