Abstract

BACKGROUND Polymyxins are currently used as a “last-line” treatment for multidrug-resistant Gram-negative infections.OBJECTIVES To identify the major mechanisms of resistance to polymyxin and compare the genetic similarity between multi-drug resistant Klebsiella pneumoniae strains recovered from inpatients of public hospitals in the Mid-West of Brazil.METHODS 97 carbapenems non-susceptible K. pneumoniae were studied. β-lactamases (bla OXA-48, bla KPC, bla NDM, bla CTX-M, bla SHV, bla TEM, bla IMP, bla VIM) and mcr-1 to mcr-5 genes were investigated by polymerase chain reaction (PCR). Mutations in chromosomal genes (pmrA, pmrB, phoP, phoQ, and mgrB) were screened by PCR and DNA sequencing. Clonal relatedness was established by using pulsed-field gel electrophoresis and multilocus sequence typing.FINDINGS K. pneumoniae isolates harbored bla KPC (93.3%), bla SHV (86.6%), bla TEM (80.0%), bla CTX-M (60%) genes. Of 15 K. pneumoniae resistant to polymyxin B the authors identified deleterious mutations in pmrB gene, mainly in T157P. None K. pneumoniae presented mcr gene variants. Genetic polymorphism analyses revealed 12 different pulsotypes.MAIN CONCLUSIONS Deleterious mutations in pmrB gene is the main chromosomal target for induction of polymyxin resistance in carbapenem-resistant K. pneumoniae in public hospitals in the Mid-West of Brazil.

Highlights

  • Polymyxins are currently used as a “last-line” treatment for multidrug-resistant Gram-negative infections

  • 2|6 Ana Claudia Souza Rodrigues et al The polymyxin B minimum inhibitory concentration (MIC) were performed by broth microdilution test according the CLSI.[11]. Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 were used as quality control

  • Antimicrobial susceptibility test showed that seven PRKp were XDR

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Summary

Objectives

To identify the major mechanisms of resistance to polymyxin and compare the genetic similarity between multidrug resistant Klebsiella pneumoniae strains recovered from inpatients of public hospitals in the Mid-West of Brazil.

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