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Research was conducted to examine porin loss as a mechanism of antimicrobial resistance in Klebsiella pneumoniae. Clinical strains resistant to beta-lactam antibiotics, which have a common characteristic of lacking expression of the OmpK35 and OmpK36 porins, were isolated. The porin genes were PCR amplified from porin deficient K. pneumoniae clinical isolates. Results demonstrated the existence of a new porin gene in K. pneumoniae.

Two porins, OmpK36 and OmpK35, have been previously isolated from Klebsiella pneumoniae, and they are homologous to the Escherichia coli porins OmpC and OmpF, respectively. Identification of the two porins revealed that most isolates lacking expression of extended-spectrum beta-lactamases express the two porins, while most isolates producing these beta-lactamases express only porin OmpK36, and the OmpK35 porin is either very low or not expressed.