Antagonistic Effect of Colistin on Vancomycin Activity against Methicillin-Resistant Staphylococcus aureus in In Vitro and In Vivo Studies

Sungim Choi, Song Mi Moon, Su Jin Park, Seung Cheol Lee, Kyung Hwa Jung, Heung Sup Sung, Mi Na Kim, Jiwon Jung, Min Jae Kim, Sung Han Kim, Sang Oh Lee, Sang Ho Choi, Jin Yong Jeong, Jun Hee Woo, Yang Soo Kim, Yong Pil Chong

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8 Scopus citations

Abstract

As concerns arise that the vancomycin MIC of methicillin-resistant Staphylococcus aureus (MRSA) could be increased by concurrent colistin administration, we evaluated the effect of colistin on vancomycin efficacy against MRSA via in vitro and in vivo studies. Among MRSA blood isolates collected in a tertiary-care hospital, we selected representative strains from community-associated MRSA strains (CA-MRSA; ST72-MRSA-SCCmec IV) and hospital-acquired MRSA strains (HA-MRSA; ST5-MRSA-SCCmec II). USA CA-MRSA (USA300), HA-MRSA (USA100), N315 (New York/Japan clone), and a MRSA standard strain (ATCC 43300) were used for comparison. We performed checkerboard assays to identify changes in the vancomycin MIC of MRSA following colistin exposure and evaluated the effect of a vancomycin-colistin combination using time-kill assays. We also assessed the in vivo antagonistic effect by administering vancomycin, colistin, and a combination of these two in a neutropenic murine thigh infection model. In the checkerboard assays, vancomycin MICs of all MRSA strains except N315 were increased by from 0.25 to 0.75 μg/ml following colistin exposure. However, the time-kill assays indicated antagonism only against ST5-MRSA and USA100, when the vancomycin concentration was twice the MIC. In the murine thigh infection model with ST5-MRSA and USA100, vancomycin monotherapy reduced the number of CFU/muscle >1 log10 compared to a combination treatment after 24 h in ST5-MRSA, indicating an antagonistic effect of colistin on vancomycin treatment. This study suggests that exposure to colistin may reduce the susceptibility to vancomycin of certain MRSA strains. Combination therapy with vancomycin and colistin for multidrug-resistant pathogens might result in treatment failure for concurrent MRSA infection.

Original languageEnglish
JournalAntimicrobial Agents and Chemotherapy
Volume64
Issue number4
DOIs
StatePublished - 24 Mar 2020

Keywords

  • antagonism
  • colistin
  • combination
  • MRSA
  • vancomycin

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