23 October 2014, 12.00pm-1.00pm, GLT3, Warwick Medical School Building, University of Warwick
'Evolution of penicillin-resistant streptococcus pneumoniae'
Professor Regine Hakenbeck, University of Kaiserslautern, Department of Microbiology and Alfried Krupp Wissenschaftskolleg Greifswald
Streptococcus pneumoniae is the paradigm for the evolution of target mediated penicillin resistance. The first resistant isolates in Papua-New Guinea were reported in the 1970s, followed by the dramatic appearance of high level penicillin and multiple antibiotic resistant strains in South Africa. Since then, rates of resistance and the level of resistance have increased worldwide to over 70 % in some regions. Penicillin resistance is due to alterations in the target enzymes for beta-lactam, the penicillin-binding proteins (PBPs). Resistant S. pneumoniae isolates contain mosaic genes encoding altered PBPs with low affinity to the antibiotic. Mosaic genes are the result of horizontal gene transfer, with commensal species such as S. mitis and S. oralis being the putative donor species. All these streptococcal species are naturally competent for genetic transformation, the reason for rapid spread of the resistance phenotype. One major family of mosaic PBP genes occurs in many distinct resistant clones of S. pneumoniae from different continents, and ancestor genes were recognized in sensitive S. mitis strains. In addition, complex mosaic structures document intensive inter- and intraspecies gene transfer. The comparison of genomes of the commensal species S. mitis and S. oralis with pneumococcal genomes sheds more light in the evolution of this pathogen.