Successive synovial Mycoplasma hominis isolates exhibit apparent antigenic variation

The expression of surface proteins by 14 successive Mycoplasma hominis isolates obtained from the synovial fluid of a chronically infected septic arthritis patient was examined. Marked differences in the expression of surface proteins, as determined by monoclonal antibodies raised against the first isolate, were observed. However, identical restriction patterns and virtually identical hybridization patterns with probes containing the conserved genes of the Mycoplasma capricolum rRNA operon and the Escherichia coli elongation factor Tu suggest that the protein differences might reflect antigenic variation by M. hominis during infection.