Mycoplasma orale has a sequence similar to the insertion-like sequence of M-fermentans

Polymerase chain reaction (PCR) using the Mycoplasma fermentans insertion s equence-like element (ISLE) RW primer set amplifies DNA from Mycoplasma ora le when more than 1 ng is present in the reaction tube. In this study, ampl ified products from 11 different clinical isolates and the ATCC prototype o f M. orale were sequenced and compared to 206 bp amplicons from eight isola tes and the ATCC strain of M. fermentans. The nucleotide sequences of the a mplified M. orale products had high sequence homology (88-92%) to those fro m M. fermentans, but differed at several key positions. The M. orale produc ts contained a Dral restriction enzyme site not found in any of the M. ferm entans amplified products. Consistent with this finding, the PCR products f rom M. orale were digested by Dral while the PCR products from M. fermentan s were resistant to Dral digestion. The results suggest that M. orale may c arry a similar IS-like element that complicates but does not negate using t he ISLE PCR assay designed to detect M. fermentans. It appears possible for the RW primers to amplify M. orale if the mycoplasmas are present at highe r concentrations. The amplified products can be differentiated from those f rom M. fermentans by a rapid Dral restriction endonuclease digestion or by Southern blot analysis using the RW006 internal probe under highly stringen t conditions. (C) 1999 Academic Press.