Wang XD, Cai JC, Zhou HW, Zhang R, Chen GX
Reduced susceptibility to carbapenems in Klebsiella pneumoniae clinical isolates associated with plasmid-mediated beta-lactamases production and OmpK36 porin deficiency. [JOURNAL ARTICLE]
J Med Microbiol 2009 Jun 15.
Two carbapenem-non-susceptible K. pneumoniae (Z2554 and Z2110) were isolated from a hospital in China and were analyzed by pulsed-field gel electrophoresis. K. pneumoniae Z2554 and Z2110 were genetically unrelated and showed resistance to ertapenem and reduced susceptibility to imipenem and meropenem. Analysis of beta-lactamases indicated that K. pneumoniae Z2554 produced TEM-1 and CTX-M-14 beta-lactamases, and Z2110 produced a plasmid-mediated AmpC beta-lactamase DHA-1 in addition to TEM-1 and CTX-M-14. SDS-PAGE analysis of outer membrane proteins (OMPs) revealed that both isolates lacked an OMP of approximately 39 kDa (OmpK36), while there is an additional protein at ca. molecular weight of 26 kDa in Z2110. Analysis of OMPs genes demonstrated that the ompK35 gene sequence of K. pneumoniae Z2554 and Z2110 contained a few silent mutations. In ompK36, several insertions and deletions of short DNA fragment (1 to 6 bp) were detected in both isolates. The N-terminal sequence of the protein band identified in Z2110 with ca. 26 kDa has no similarity with the sequence of OmpK36. It rather has high similarity with a hypothetical protein called KPN_03267 originated from K. pneumoniae subsp. pneumoniae MGH78578.We conclude that beta-lactamases production combined with OmpK36 deficiency results in ertapenem resistance and reduced imipenem and meropenem susceptibility in K. pneumoniae Z2554 and Z2110. OmpK36 appears to play a major role in the resistance or reduced susceptibility to carbapenems in K. pneumoniae producing AmpC, ESBL or broad-spectrum beta-lactamase.
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