Detection of synergy using the combination of polymyxin B with either meropenem or rifampin against carbapenemase-producing Klebsiella pneumoniae

Polymyxin B (PB) plus meropenem (MER) or rifampin (RIF) was tested by Etest® method and time-kill assay (TKA) against 14 genetically unique clinical Klebsiella pneumoniae carbapenemase-producing K. pneumoniae. PB + MER: Etest, 43% synergy; TKA, 64% synergy. Concordance between methods was 79%. For PB + RIF: Etest, 21% synergy; TKA, 100% synergy. Concordance between methods was 21%.