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

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??g/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.

SUBMITTER: Choi S

PROVIDER: S-EPMC7179267 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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

Choi Sungim S Moon Song Mi SM Park Su-Jin SJ Lee Seung Cheol SC Jung Kyung Hwa KH Sung Heung-Sup HS Kim Mi-Na MN Jung Jiwon J Kim Min Jae MJ Kim Sung-Han SH Lee Sang-Oh SO Choi Sang-Ho SH Jeong Jin-Yong JY Woo Jun Hee JH Kim Yang Soo YS Chong Yong Pil YP

Antimicrobial agents and chemotherapy 20200324 4

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-MRS ...[more]

PMID: 32041713

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Project description:ObjectivesDalbavancin is a lipoglycopeptide active against methicillin-resistant Staphylococcus aureus (MRSA). Its long half-life (8.5-16 days) allows for once-weekly or single-dose treatments but could prolong the mutant selection window, promoting resistance and cross-resistance to related antimicrobials such as vancomycin. The objective of this study was to evaluate the capacity of post-distributional pharmacokinetic exposures of dalbavancin to select for resistance and cross-resistance in MRSA.MethodsWe simulated average, post-distributional exposures of single-dose (1500 mg) dalbavancin (fCmax 9.9 μg/mL, β-elimination t1/2 204 h) in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model for 28 days (672 h) against five MRSA strains and one methicillin-susceptible strain (MSSA). Samples were collected at least daily, and surviving colonies were enumerated and screened for resistance on drug-free and dalbavancin-supplemented medium respectively. Isolates from resistance screening plates were subjected to whole-genome sequencing (WGS) and susceptibly testing against dalbavancin, vancomycin, daptomycin, and six β-lactams with varying penicillin-binding protein (PBP) affinities.ResultsDalbavancin was bactericidal against most strains for days 1-4 before regrowth of less susceptible subpopulations occurred. Isolates with eight-fold increases in dalbavancin MIC were detected as early as day 4 but increased 64-128-fold in all models by day 28. Vancomycin and daptomycin MICs increased 4-16-fold, exceeding the susceptibly breakpoints for both antibiotics; β-lactam MICs generally decreased by two-to eight-fold, suggesting a dalbavancin-β-lactam seesaw effect, but increased by eight-fold or more in certain isolates. Resistant isolates carried mutations in a variety of genes, most commonly walKR, apt, stp1, and atl.ConclusionsIn our in vitro system, post-distributional dalbavancin exposures selected for stable mutants with reduced susceptibility to dalbavancin, vancomycin, and daptomycin, and generally increased susceptibility to β-lactams in all strains of MRSA tested. The clinical significance of these findings remains unclear, but created an opportunity to genotype a unique collection of dalbavancin-resistant strains for the first time. Mutations involved genes previously associated with vancomycin intermediate susceptibility and daptomycin non-susceptibility, most commonly walKR-associated genes.

Dataset Information

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

Publications

Antagonistic Effect of Colistin on Vancomycin Activity against Methicillin-Resistant Staphylococcus aureus in <i>In Vitro</i> and <i>In Vivo</i> Studies.

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