The Dissemination of Antibiotic Resistance by Bacterial Conjugation

Abstract

In areas where trachoma is highly endemic, that is, where about 70% of the population is infected, many individuals typically carry Streptococcus pneumoniae. Of these, 2% were originally macrolide resistant. After 2 weeks of trachoma treatment, the carrier rate for macrolide-resistant pneumococci rose to 50%, with an increase in the carrier rate of the more highly resistant strains. This study dramatically illustrates the potential for rapid in vivo selection of resistance. In this study it was also found that one chronically ill child was carrying a strain with very high level resistance. This chapter defines gene dissemination mechanisms and shows how and why conjugative mechanisms are the most proficient in multiple drug resistance (MDR) transfer. The plasmid is an interesting variation on the theme of MDR dissemination. The chapter reviews aspects of bacterial conjugation in terms of basic science and clinical relevance. A unifying model can be developed because the general mechanism for classical bacterial conjugation appears to be conserved in conjugative transposons. It is reasonable to suggest that bacterial conjugation is the greatest mover of genes in the microbial world and, in the clinical world, that these genes are often antibiotic resistance genes. The cycle of antibiotic resistance and pathogen genome sequencing are showcasing the prominent role of bacterial conjugation in gene dissemination.