[Phenotypic variations of susceptibility in Klebsiella pneumoniae strains of nosocomial origin and their association with biofilm formation].

Klebsiella pneumoniae is the principal opportunist pathogen associated with nosocomial infections. The morbidity and mortality produced by this microorganism is related mostly to antimicrobial resistance and its capacity to form biofilms. In this study, the phenotypic variations of susceptibility in 50 Klebsiella pneumoniae strains (26 betaLEE-producer and 24 no betaLEE-producer) isolated from pediatric patients with nosocomial septicemia at the High-risk Neonatal Unit of the Instituto Aut6nomo Hospital Universitario de Los Andes, Mérida, Venezuela and their associations with biofilm formation were analyzed. These strains were biochemically identified by standard microbiology methods. Antimicrobial susceptibility was determined by minimal inhibitory concentration and biofilm formation was detected by spectrophotometric techniques. Most of betaLEE strains were frequently associated with resistance markers such as tobramycin, kanamycin, tetracycline, chloramphenicol (38% each), streptomycin (36%) and netilmicin (34%). The predominant multiresistent phenotype was composed of betaLEE+ -AMG-TET-CLF (30%). 18% of K. pneumoniae strains were sensible to the antibiotics tested. Formation of biofilm was observed in 77.8% and 96.2% of sensible and resistent strains, respectively. There was no statistic relation between phenotipic variations of susceptibility and biofilm formation (p > = 0.05). However, both characteristics of K. pneumoniae should be evaluated to determine the therapeutic conduct to treat patients with nosocomial infection.