Detection and analysis of different interactions between resistance mechanisms and carbapenems in clinical isolates of Klebsiella pneumoniae

Abstract Carbapenems are considered last-line agents for the treatment of serious infections caused by Klebsiella pneumoniae, and this microorganism may exhibit resistance to β-lactam antibiotics due to different mechanisms of resistance. We evaluated 27 isolates of K. pneumoniae resistant to carbapenems recovered from inpatients at the University Hospital of Santa Maria-RS from July 2013 to August 2014. We carried out antimicrobial susceptibility, carbapenemase detection, testing for the presence of efflux pump by broth microdilution and loss of porin by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Genetic similarity was evaluated by ERIC-PCR. High levels of resistance were verified by the minimum inhibitory concentration for the antimicrobials tested. The blaKPC gene was present in 89% of the clinical isolates. Blue-Carba and combined disk with AFB tests showed 100% concordance, while the combined disk test with EDTA showed a high number of false-positives (48%) compared with the gold-standard genotypic test. Four isolates showed a phenotypic resistance profile consistent with the overexpression of the efflux pump, and all clinical isolates had lost one or both porins. The ERIC-PCR dendrogram demonstrated the presence of nine clusters. The main mechanism of resistance to carbapenems found in the assessed isolates was the presence of the blaKPC gene.

Caracterização molecular da resistência a oxacilina em isolados de staphylococcus aureus hospitalares e comunitários / Molecular characterization of oxacillin resistance in staphylococcus aureus isolates from hospital and community

Os objetivos do presente estudo foram avaliar os perfis de sensibilidade a antimicrobianos de MRSA isolados de sangue, identificar o tipo de SCCmec e analisar o perfil de DNA desses isolados para verificar a existência de linhagens predominantes. Amostras de MRSA isoladas de sangue foram submetidas ao teste de triagem em ágar para detecção de resistência a oxacilina, teste de sensibilidade aos antimicrobianos, PCR multiplex para detecção dos genes mecA e coa e do tipo de SCCmec, tipagem molecular por PFGE. 89% das amostras de MRSA foi de origem hospitalar. Foi observado multirresistência em 69% dos isolados. 83% dos isolados apresentaram SCCmec tipo IIIA e um perfil PFGE predominante. Foram observadas amostras de MRSA sensíveis a diversas classes de antimicrobianos, portando SCCmec tipo IV, associadas a infecção de origem hospitalar e a tipagem molecular permitiu observar o predomínio de um clone, disseminado em todo o complexo HC.

The aims of this study were to evaluate the susceptibility profile of MRSA strains isolated from blood, identify the SCCmec types and analyze the DNA profile in order to determine if there were predominant lineages. Consecutive MRSA blood isolates were submitted to oxacillin agar screening test, antimicrobial susceptibility test, multiplex PCR to detect mecA and coa genes, SCCmec typing and molecular typing by PFGE. 89% of the isolates were nosocomial-acquired. 69% of strains were observed to be multiresistant. 83% of the 223 isolates had SCCmec type IIIA and had a predominant DNA pattern by PFGE. Some strains nosocomial-acquired had SCCmec type IV, resistance only to beta-lactams and demonstrated PFGE pattern with one predominant clone.