STUDY OF THE ENZYME-HOST COMPATIBILITY AND THE INCORPORATION OF OXA ΒETALACTAMASES INTO OUTER MEMBRANE VESICLES

CAPODIMONTE, LUCIA; LÓPEZ, CAROLINA; VILA, ALEJANDRO

Los Cocos, Córdoba

Congreso; XVII Congreso Argentino de Microbiología General; 2022

Sociedad Argentina de Microbiología General (SAMIGE)

MODALIDAD POSTEROXA enzymes belong to class D of β-lactamases, representing around 15% of the total universe of β- lactamases. Some OXAs are capable of hydrolyzing carbapenems, “last resort” antibiotics, whichmakes the bacteria carrying them a threat of major concern. OXA-23, OXA-24 and OXA-48 are themost clinically relevant enzymes from this family. OXA-48, initially isolated from Klebsiella pneumoniae, is also found in other species from Enterobacteriaceae, while OXA-23 and OXA-48 arefrequently found in Acinetobacter baumannii. Furthermore, OXA-23 and OXA-24 are putative lipoproteins; since they have a lipobox sequence which anchors them to the outer membrane,whereas OXA-48 is a soluble periplasmic protein, without a lipobox sequence. In order to understand the features determining the host specificity of these enzymes, we study the effect of their expression on different bacteria (A. baumannii, Escherichia coli, and Pseudomonas aeruginosa). We analyzed the resistance phenotype by measuring MICs against different carbapenems, and the fitness cost by growth curves. We observed that, although some of these enzymes conferred great resistance, the fact that they negatively affected the bacterial growth excludes them from some bacterial strains. Some β-lactamases can be incorporated into outer membrane vesicles (OMVs), which makes them less susceptible to degradation and allows them to protect coexisting bacterial populations, playing a key role in polymicrobial infections. We studied the incorporation of OXAs into OMVs, focusing on the role of their cellular localization. We studied OXA-23 as a model of a lipoprotein and OXA-48 as a model of a soluble periplasmic protein. We purified OMVs of E. coli and A. baumannii expressing OXA- 23 and OXA-48 and their levels were determined by immunoblotting. Both enzymes were incorporated in OMVs but the proportion varied in each of the studied bacterial host, indicating that there are protein- and host-dependent features that play a role in OXAs levels into vesicles. We observed that membrane anchoring is not the only factor that favors the selective packaging of OXAs into OMVs, and this incorporation involves specific enzyme-host interactions.