Abstract

GARCIA CASTELLANOS, Tersilia; CASTILLO MARSHAL, Arianna  and  SALAZAR RODRIGUEZ, Daniel. Mechanisms of resistance to beta-lactams in Gram-negative bacteria. Rev Cubana Salud Pública [online]. 2014, vol.40, n.1, pp. 129-135. ISSN 0864-3466.

The beta-lactams antibiotics are commonly used in the treatment of infections caused by Gram-negative bacteria. However, growing antimicrobial resistance has limited their use in cases with this treatments . The objective of this paper was to describe the beta-lactams resistance mechanisms in Gram-negative bacteria. Isolates of Escherichia coli, Klebsiella pneumoniae, Enterobacter spp. and Pseudomonas aeruginosa, identified in the Clinical Microbiology Department of "Pedro Kouri" Institute in two years (2010 and 2011), were analyzed. Bacterial identification and antimicrobial susceptibility were both determined by the automated VITEK 2 Compact (bioMérieux, France). A total number of 623 isolates of Escherichia coli, 159 of Klebsiella pneumoniae, 155 of Pseudomonas aeruginosa and 95 of Enterorobacter spp were identified. The production of extended-spectrum beta-lactamases (ESBLs) was observed in 22.2 % of enterobacteria, mainly in E. coli (51.7 %). Carbapenemen resistance due to impermeability was manifested in 3.9 % of all isolates, predominantly in P. aeruginosa (87.9 %). The production of carbapenemases (0.3 %) was observed only in Enterobacter strains Resistance to beta-lactams in identified enterobacteria was primarily determined by the production of extended-spectrum beta-lactamases, but one must take into account the production of AmpC cephalosporinases mainly in Enterobacter spp. Impermeability in P. aeruginosa is one of the most important mechanisms of resistance against carbapenems.

Keywords : mechanisms of resistance; beta-lactams; Gram-negative bacteria.