Decreased penicillin sensitivity of pneumococci

: The mechanism of penicillin-resistance of Streptococcus pneumoniae involves the development of altered forms of penicillin-binding proteins (PBPs) that have a decreased affinity for penicillin. PBPs are involved in the assembly of the cell wall. Normal forms of PBPs are inhibited by penicillin but altered forms are not. It appears that the altered PBP genes arose by interspecies recombinational events in which segments of the PBPs structural genes had been replaced by regions derived from PBP genes of oral streptococcal species. Altered PBP genes of penicillin-resistant pneumococci can be spread horizontally to sensitive pneumococci by transformation. Highly resistant pneumococci have several altered PBPs and also show resistance to the third-generation cephalosporins and other antibiotics. Some clones of resistant pneumococci seem to have an increased epidemic potential to spread. In Austria, Germany, Italy, and Switzerland approximately 95% of pneumococci are still penicillin-sensitive. However, an increase of the highly resistant pneumococci would change the empirical therapy of severe pneumococcal infections in the near future. Reasonable use of antimicrobials might reduce the selective antimicrobial pressure and the spread of penicillin-resistant strains.