Drug resistance in Streptococcus pneumoniae:: epidemiology and control

Streptococcus pneumoniae is one of the most important human pathogens, The rapid emergence and global spread of resistance against the most important antibiotics is therefore a serious public health concern. Resistance to beta-lactam antibiotics is due to alteration of the penicillin-binding proteins (PBPs), enzymes responsible for cell wall synthesis. This alteration implies reduced affinity for penicillin and also for other beta-lactam drugs, but to a different extent. Under the influence of antibiotic selective pressure, increase in resistance prevalence is due to (1) horizontal transfer of low-affinity PBP gene segments from closely related alpha-haemolytic streptococci by natural transformation, (2) spread of antibiotic-resistant clones and (3) further remodelling of PBP genes by mutations and further gene exchange. Although the risk,factors associated with carriage and infection by resistant strains are well known, the effect of community-wide interventions is not. Prudent use of antibiotics, vaccination by improved conjugate vaccines and infection control measures are likely to be important in preserving the efficacy of available antimicrobial agents.