RELATEDNESS AMONG PENICILLIN-BINDING PROTEIN 2B GENES OF STREPTOCOCCUS-MITIS, STREPTOCOCCUS-ORALIS, AND STREPTOCOCCUS-PNEUMONIAE

Penicillin-binding protein (PBP) 2b similarities among Streptococcus m itis, S. oralis, and S. pneumoniae using DNA fingerprinting and sequen cing were investigated, The polymerase chain reaction (PCR) was perfor med on 41 penicillin-susceptible and -resistant clinical isolates of S . mitis and S. oralis using the susceptible S. pneumoniae R6 PBP 2b pr imers, PCR products were then analyzed using Hinf I and Sty I restrict ion enzymes, Of 41 S. mitis/S, oralis isolates studied 15 strains prod uced a PCR product of a similar size to that of S. pneumoniae R6, On f ingerprinting these 15 strains, 11 different patterns were seen using Sty I restriction enzyme and 12 different patterns with Hinf I, The PB P 2b genes of the S. mitis and S. oralis isolates studied were found t o be very heterogenous. The PBP 2b genes of two S, mitis isolates, MIC s 0.5 and 2 mu g/ml, were sequenced, These PBP 2b genes were found to possess a mosaic structure when compared to those of other S, pneumoni ae and viridans streptococcal species, Analysis of these mosaic blocks indicates that both S, mitis strains contain areas that originated fr om S, pneumoniae as well as regions of unknown origin, PBP 2b sequence comparisons of a susceptible S, oralis with reported sequences of S, pneumoniae R6 and S, mitis NCTC 10712 revealed what appears at this st age to be nucleotide regions unique to S, oralis, A penicillin-resista nt S, oralis strain contained a pneumococcal region of 272 bp that was flanked by S, oralis sequences, These specific S, oralis regions have been located in PBP 2b genes of penicillin-resistant S. oralis and S, pneumoniae isolates described from Europe and South Africa.