Antimicrobial resistance and clonality in Acinetobacter baumannii

Abstract

The aim of this thesis was to obtain insight into the epidemiology and molecular basis of multidrug resistance of Acinetobacter baumannii at the population level. To this aim a number of studies were performed on strains mainly from the Czech Republic (CR) which have shown in particular that (i) the vast majority of multidrug resistant (MDR) clinical isolates of A. baumannii from CR belong to clonal lineages termed EU clone I and II; (ii) these two clones have predominated among MDR hospital isolates in CR since at least 1991; (iii) recent emergence of A. baumannii resistance to carbapenems in CR was associated with the country-wide spread of a subclone of EU clone II; (iv) multidrug resistance is a general feature of strains of EU clones I and II, yet strains belonging to one clone may vary in the content of resistance genes; (v) upregulation of genes intrinsic to A. baumannii as well as horizontal acquisition of resistance genes can be sources of development of multidrug resistance and intraclonal diversification; (vi) the genes encoding the non-specific efflux system AdeABC are present in nearly all A. baumannii strains, yet the AdeABC overexpression is seen mostly in MDR strains harbouring additional resistance genes.