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.