Unusually High Prevalence of Cosecretion of Ambler Class A and B Carbapenemases and Nonenzymatic Mechanisms in Multidrug-Resistant Clinical Isolates of <i>Pseudomonas aeruginosa</i> in Lebanon

Abstract

The opportunistic pathogen, <i>Pseudomonas aeruginosa</i>, is a main cause of nosocomial infections in Lebanese hospitals. This pathogen is highly threatening due to its ability to develop multiresistance toward a large variety of antibiotics, including the carbapenem subgroup of β-lactams. In this study, we surveyed the enzymatic and nonenzymatic mechanisms of carbapenem resistance in several multidrug-resistant (MDR) strains of <i>P. aeruginosa</i> isolated from patients suffering from nosocomial urinary tract infections in a Lebanese hospital. The occurrence of β-lactamase-encoding genes notably <i>GES, KPC, IMP, VIM, NDM,</i> and <i>OXA,</i> which are characterized by a carbapenemase activity was checked by genomic analyses. Our results provide a first evidence of the occurrence of <i>GES</i> in clinical <i>P. aeruginosa</i> isolates resistant to carbapenems in Lebanon. More interestingly, we showed that almost 40% of the analyzed strains have acquired a dual-carbapenemase secretion of <i>GES-6</i> and <i>VIM-2</i> or <i>IMP-15</i>, this being a rare phenomenon among this type of multidrug resistance. Moreover, LC-MS/MS analyses revealed a high prevalence of another enzymatic mechanism of resistance; this is the coexistence of <i>AmpC</i> and <i>Pdc-13</i> as well as a number of virulence proteins, for instance pilin, lytic transglycosylase, ecotin, chitin-binding protein (Cbp), and TolB-dependent receptor. It is to be noted that a mutation of the <i>oprD2</i> gene encoding a porin selective for carbapenems has been detected in almost 66% of our strains. All in all, our study reveals by the use of different methods, unusual simultaneous enzymatic (<i>GES</i>, <i>IMP</i>, <i>VIM</i>, <i>pdc13</i>, and <i>AmpC</i>) and nonenzymatic mechanisms of resistance (reduction of <i>OprD2</i> expression) for MDR <i>Pseudomonas aeruginosa</i>.