Sergei Vakulenko, Research Associate Professor

Mechanisms and evolution of resistance of clinically important pathogens to two major classes of antibiotic, beta-lactams and aminoglycosides. Exposure of bacteria to antibiotics in clinical environments results in selection of antibiotic-resistant microorganisms and dramatically reduces our chances to successfully challenge infectious diseases. Resistance to beta-lactam antibiotics in Gram-negative bacteria is mainly associated with the production of beta-lactamases, enzymes that efficiently hydrolyze the drug. Beta-lactamases are classified into a four major classes, are capable of efficiently broaden their substrate specificity as a result of single or multiple amino acid substitutions in their structures. Dr. Vakulenko is interested not only to identify such mutational changes, but also to predict (using in vitro directional evolution approaches, such as DNA shuffling) the development of new types of resistance to beta-lactam antibiotics and beta-lactamase inhibitors. Bacterial resistance to another class of antibiotics, aminoglycosides, is largely the result of enzymatic modification of various aminoglycoside antibiotics. Three major types of enzymes are produced by resistant microorganisms: aminoglycoside acetyltransferases, -phosphotransferases and -nucleotidyltransferases. Dr. Vakulenko investigates mechanisms and possible evolutionary pathways of the aminoglycoside phosphotransferases produced by clinical isolates of Enterococci that result in emergence of novel resistance patterns.

Analysis of mutant beta-lactamases and aminoglycoside-modifying enzymes that we produce include evaluation of their role in produced antibiotic resistance, detail kinetic measurements with various substrates and, finally, crystallographic analysis. These studies aimed to facilitate our understanding of evolution of antibiotic resistance mechanisms in bacteria, to forecast appearance of novel mutants and to improve existing and to develop new strategies to counter such resistance.