ABSTRACT
Introduction ........................................................................................................ 230 Evolution of Antibiotic Resistance .................................................................... 230
β-Lactam Resistance and Clinical Consequences .................................. 230 Role of Penicillin-Binding Proteins in β-Lactam Resistance ...... 231 Role of Oral Streptococci in the Formation of Mosaic pbp Genes ... 232
Development of Multiple Antibiotic Resistance ..................................... 232 Epidemiology of S. pneumoniae ........................................................................ 234
Population Structure of S. pneumoniae .................................................. 234 Intercontinental Spread of Resistant Clones ........................................... 235 Prevalence of PNSP Worldwide .............................................................. 237
Summary and Future Prospects ......................................................................... 239 References .......................................................................................................... 240
Streptococcus pneumoniae is still an important human bacterial pathogen. The past two decades have witnessed the global spread of resistance to major groups of antipneumococcal drugs and there are no countries free of multidrug-resistant strains. In this naturally transformable organism resistance to antibiotics can arise by both inter-and intra-species recombination events, enabling resistance acquired by horizontal gene transfer or from point mutation to spread throughout the population. However, there is also strong evidence for clonal expansion by the international spread of multidrug-resistant strains. Among such successful clones, the Spain23F-1, Spain6B-2, and Spain9V-3 in particular have reached the status of pandemic clones. All three have emerged as being penicillin-non-susceptible (PNSP) and often resistant to tetracyclines, macrolides, chloramphenicol, or co-trimoxazole. The presence
of the most successful, the Spain23F-1 clone, and its other capsular variants, has been documented in 42 countries all over the world. The susceptibility-testing results survey done for this study showed that prevalence of PNSP was above 40% in 25 out of 96 countries and below 5% in only 8 of them. This chapter offers insight into the mechanisms of the antibiotic resistance acquisition in pneumococci, their evolution, and the epidemiology of multidrug-resistant strains.
