Phenotypic and genotypic characterization of carbapenemases produced by Gram-negative bacterial pathogens isolated in hospitals in Paraguay (2022)

Abstract

Introduction: the dissemination of Gram-negative bacteria resistant to carbapenems represents an important cause of morbidity and mortality, being a growing threat to public health and of great concern worldwide. Although resistance to carbapenems can be due to several mechanisms, the most relevant, clinically and epidemiologically, is enzyme production. The goals of this study were to phenotypically and genotypically characterize carbapenemases produced by clinically important Gram-negative bacilli (GNB) isolated in hospitals in Paraguay in 2022 and evaluate the susceptibility to colistin.
Methodology: retrospective study, carried out on 1,226 GNB strains sent to the Central Laboratory during 2022 for phenotypic and genotypic characterization. Identification studies were performed out by conventional methods, susceptibility to colistin by microdilution in broth, and molecular studies for the confirmation of resistance genes.
Results: in total, of 1226 GNB isolates, 629 (51 %) were confirmed as non-carbohydrate-fermenting GNB (89 % Acinetobacter spp.) and 597 (49 %) as carbohydrate-fermenting GNB (74 % Klebsiella pneumoniae). Carbapenemases OXA-23 (94.9 %), NDM (3.1 %), OXA-23+NDM (1.8 %) and OXA-23+NDM+OXA-58 (0.2 %) were confirmed in Acinetobacter baumannii; in K. pneumoniae: NDM (84.5 %), KPC (11.7 %), KPC+NDM (3.7 %) and NDM+OXA-48like (0.2 %); and in P. aeruginosa the prevalent was NDM (50.9 %). Colistin-associated resistance was found mainly in K. pneumoniae (24%).
Conclusions: in our country the circulation of carbapenemase-producing bacteria is endemic. The co-production of these enzymes is confirmed. NDM is prevalent in Enterobacterales and P. aeruginosa, and OXA-23 in A. baumannii. The high resistance associated with colistin in K. pneumoniae makes it imperative to have new, more effective antimicrobials for the treatment of infections.