A. Domenech-sanchez et al., Identification and characterization of a new porin gene of Klebsiella pneumoniae: Its role in beta-lactam antibiotic resistance, J BACT, 181(9), 1999, pp. 2726-2732
Klebsiella pneumoniae porin genes were analyzed to detect mutations account
ing for the porin deficiency observed in many beta-lactam-resistant strains
. PCR and Southern blot analysis revealed the existence of a third porin ge
ne in addition to the OmpK36 and OmpK35 porin genes previously described. T
his new porin gene was designated ompK37 and is present in all of the clini
cal isolates tested. The OmpK37 porin gene was cloned, sequenced, and overe
xpressed in Escherichia coli. In contrast to that of the major porins, OmpK
37 porin expression was only detectable by Western blot analysis in porin-d
eficient beta-lactam-resistant strains, suggesting strong down regulation u
nder standard laboratory conditions. Functional characterization suggested
a narrower pore for the OmpK37 porin than for K. pneumoniae porins OmpK36 a
nd OmpK35, This correlated with the susceptibility to certain beta-lactam a
ntibiotics, since a K. pneumoniae strain expressing porin OmpK37, but not p
orin OmpK36 or OmpK35, was less susceptible to beta-lactam antibiotics than
the same strain expressing either porin OmpK36 or OmpK35.