Proteomic profiling of Klebsiella pneumoniae carbapenemase (KPC)-producer Klebsiella pneumoniae after induced polymyxin resistance.

Aim: To elucidate the changes in protein expression associated with polymyxin resistance in Klebsiella pneumoniae, we profiled a comparative proteomic analysis of polymyxin B-resistant mutants KPC-2-producing K. pneumoniae, and of its susceptible counterparts. Material & methods: Two-dimensional reversed phase nano ultra-performance liquid chromatography mass spectrometry was used for proteomic analysis. Results: Our results showed that the proteomic profile involved several biological processes, and we highlight the downregulation of outer membrane protein A (OmpA) and the upregulation of SlyB outer membrane lipoprotein (conserved protein member of the PhoPQ regulon) and AcrA multidrug efflux pump in polymyxin B-resistant strains. Conclusion: Our results highlight the possible participation of the SlyB, AcrA and OmpA proteins in the determination of polymyxin B heteroresistance in KPC-2-producing K. pneumoniae.

(-)-Camphene-based derivatives as potential antibacterial agents against Staphylococcus aureus and Enterococcus spp.

Aim: To evaluate the activity of (-)-camphene-based thiosemicarbazide (TSC) and 4-hydroxy-thiosemicarbazone (4-OH-TSZ), alone and in combination against Gram-positive. Material & methods: MIC were determined for Staphylococcus aureus, Enterococcus spp. reference strains and clinical isolates. Drug combination, time-kill and cytotoxicity assays were also performed. Results: TSC and 4-OH-TSZ demonstrated potent inhibitory activity against S. aureus and Enterococcus spp., including multidrug-resistant isolates (MIC ranging from 1.9 to 31.2 µg/ml), and were bactericidal for the reference strains of both Gram-positive tested. The derivatives proved to be selective for the bacteria and synergistic with oxacillin and vancomycin. Conclusion: (-)-Camphene-based derivatives can represent promising drug candidates against critical pathogens, such as S. aureus and Enterococcus spp., including MRSA and vancomycin resistance Enterococcus spp. isolates.