Epidemiologia molecular de enterobactérias resistentes a carbapenêmicos

Abstract

Enterobacteriaceae producing β-lactamases extended spectrum (ESBL) and carbapenemases continue to be the leading cause of resistance to β-lactam antibiotics and, potentially a major global health problem. This study was carried out to assess antimicrobial susceptibilities and molecular epidemiology of β-lactamases-producing Serratia sp. and Klebsiella sp. strains isolated in a public hospital in Dourados/MS. During May/2011 to May/2013, 30 Serratia marcescens and 68 Klebsiella pneumoniae strains with resistance or intermediate profile to third-generation cephalosporins were recovered. Species identification was performed with Vitek-2 automatized system and confirmed by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS). All strains showed resistances to carbapenem by minimum inhibitory concentration (MIC). Carbapenemase production by Modified Hodge Test (MHT) was detected in 67 K. pneumoniae and 24 S. marcescens strains. However, carbapenem hydrolysis by MALDI-TOF MS was detected in 57 K. pneumoniae and 24 S. marcescens. The blaKPC-2 gene was present in 24 carbapenem-resistant S. marcescens and among them the blaIMP-10 gene was also observed in six strains. The presence of blaTEM-like and blaSHV-like genes was evidenced in six S. marcescens negative to blaKPC-2. The conjugation experiments and hybridization showed that blaKPC-2 gene was inserted into conjugative plasmids while blaIMP-10 gene, was inserted into a class 1 integron with the presence of two inserted gene cassette, aac(6’)-IIc and aad1. All KPC-producing S. marcenscens strains showed the same PFGE patters. PCR amplification and sequencing showed that the blaKPC-2 gene was present in 57 carbapenem-resistant K. pneumoniae. The blaKPC-2 gene was not found in 11 strains. However, the presence of blaCTX– M-1-like, blaCTX–M-2-like, blaCTX-M-8 like, blaCTX-M-14-like, blaSHV-like genes and altered OmpK35 and OmpK36 proteins, were observed. The KPC-producing K. pneumoniae showed high genetic similarity in PFGE analysis. To identify risk factors for KPC-producing K. pneumoniae, a case-control study was conducted with 94 patients (47 cases and 47 controls). Longer hospitalizations, previous surgery, use of mechanical ventilation, central venous catheter and urinary catheter were associated with KPC-producing K. pneumoniae in the multivariable analysis. The results indicate the spread of β-lactamases-producing Enterobacteriaceae in a public hospital in Dourados Mato Grosso do Sul and the first report of KPC-2 and IMP-10 co producing S. marcescens strains. Therefore, understanding the extent of the reservoir in healthcare facilities may be important for targeted intervention and reduction of hospital infections.