Repetitive element sequence-based PCR (rep-PCR) was compared to restriction fragment length polymorphism analysis using pulsed-field gel electrophoresis (RFLP by PFGE) to evaluate the sensitivity of the former for tracking microbial transfer between humans. In an initial comparison of 22 previously fingerprinted strains of Staphylococcus aureus, 19 showed distinct SmaI restriction digest patterns, but only 15 differed in rep-PCR patterns. Five strains that had identical PCR fingerprints to other strains differed in RFLP pattern by no more than two bands. To further evaluate the two techniques both rep-PCR and RFLP analyses were done on 90 S. aureus isolates from two Mir space station missions. 17 different RFLP patterns and 14 different rep-ÐPCR patterns were observed. Five strains were found to have the same rep-ÐPCR pattern as other strains, but in each case they differed in restriction digest pattern by at most two bands to the other strains. rep-PCR appeared sensitive enough for tracking S. aureus. In two Mir missions, one dominant strain was detected for three of six crew members, multiple strains were detected for two crew members, and no strain was detected for a backup crew member. Four of the six participants shared strains with the same RFLP and rep-PCR fingerprints indicating that microbial transfer occurred. Two environmental isolates from the Mir spacecraft matched the pattern of crew members illustrating environmental contamination.

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An Epidemiological Evaluation of Staphylococcus aureus on Two Mir Missions Using rep-PCR