Clinically Relevant Epithelial Lining Fluid Concentrations of Meropenem with Ciprofloxacin Provide Synergistic Killing and Resistance Suppression of Hypermutable Pseudomonas aeruginosa in a Dynamic Biofilm Model

Abstract

Treatment of exacerbations of chronic Pseudomonas aeruginosa infections in patients with cystic fibrosis (CF) is highly challenging due to hypermutability, biofilm formation, and an increased risk of resistance emergence. We evaluated the impact of ciprofloxacin and meropenem as monotherapy and in combination in the dynamic in vitro CDC biofilm reactor (CBR). Two hypermutable P. aeruginosa strains, PAOΔmutS (MIC of ciprofloxacin [MICciprofloxacin], 0.25 mg/liter; MICmeropenem, 2 mg/liter) and CW44 (MICciprofloxacin, 0.5 mg/liter; MICmeropenem, 4 mg/liter), were investigated for 120 h. Concentration-time profiles achievable in epithelial lining fluid (ELF) following FDA-approved doses were simulated in the CBR. Treatments were ciprofloxacin at 0.4 g every 8 h as 1-h infusions (80% ELF penetration), meropenem at 6 g/day as a continuous infusion (CI) (30% and 60% ELF penetration), and their combinations. Counts of total and less-susceptible planktonic and biofilm bacteria and MICs were determined. Antibiotic concentrations were quantified by an ultrahigh-performance liquid chromatography photodiode array (UHPLC-PDA) assay. For both strains, all monotherapies failed, with substantial regrowth and resistance of planktonic (≥8 log10 CFU/ml) and biofilm (>8 log10 CFU/cm2) bacteria at 120 h (MICciprofloxacin, up to 8 mg/liter; MICmeropenem, up to 64 mg/liter). Both combination treatments demonstrated synergistic bacterial killing of planktonic and biofilm bacteria of both strains from ∼48 h onwards and suppressed regrowth to ≤4 log10 CFU/ml and ≤6 log10 CFU/cm2 at 120 h. Overall, both combination treatments suppressed the amplification of resistance of planktonic bacteria for both strains and of biofilm bacteria for CW44. The combination with meropenem at 60% ELF penetration also suppressed the amplification of resistance of biofilm bacteria for PAOΔmutS. Thus, combination treatment demonstrated synergistic bacterial killing and resistance suppression against difficult-to-treat hypermutable P. aeruginosa strains.

Clinically Relevant Concentrations of Polymyxin B and Meropenem Synergistically Kill Multidrug-Resistant Pseudomonas aeruginosa and Minimize Biofilm Formation

“…Sustained bacterial clearance for up to 24 h was only achieved with the simultaneous introduction of polymyxin B at 16 mg/L. Similar initial killing followed by re-growth of otherwise meropenem-susceptible clinical strains of P. aeruginosa has previously been reported in both planktonic and biofilm-embedded bacteria exposed to meropenem monotherapy with concentrations close to or even exceeding 100% f T >MIC [48][49][50].…”

Evaluation of Meropenem‐Ciprofloxacin Combination Dosage Regimens for the Pharmacokinetics of Critically Ill Patients With Augmented Renal Clearance

“…Definitions for additivity and synergy were as described above for the SCTK studies. Concentrations of meropenem and ciprofloxacin in media samples collected from the HFIM were quantified using a validated ultra‐high‐performance liquid chromatography‐photodiode array method 25 …”

“…Concentrations of meropenem and ciprofloxacin in media samples collected from the HFIM were quantified using a validated ultra-highperformance liquid chromatography-photodiode array method. 25 Mechanism-based mathematical modeling For all three isolates, an MBM was developed based on the SCTK data at both the low and high inoculum to characterize the time-course of bacterial killing and regrowth suppression. The underlying biological processes involved in the growth and replication of P. aeruginosa were described via a life-cycle growth model incorporated in the MBM.…”

An in vitro dynamic bioreactor model for evaluating antimicrobial effectiveness on periodontal polymicrobial biofilms: a proof‐of‐concept study

“…6,8 The CDC model allows "real-time" pharmacokinetic and pharmacodynamic responses facilitated by inlet and outlet ports for infusion of media/drugs and the collection of effluent media. 9,10 There have been numerous attempts to evaluate the antimicrobial effect on Staphylococcus aureus and enterococci-derived biofilms using CDC biofilm reactor models. 11,12 Although individual species of bacteria have been implicated in the * BioSurface Technologies Corporation, Bozeman, MT, USA pathogenesis of oral diseases (e.g., dental caries and periodontitis), 13 these diseases are associated with polymicrobial biofilms.…”

“…The Center for Disease Control (CDC) bioreactor is an established model for growing biofilms and evaluating the antimicrobial activity on biofilms in dynamic and high shear conditions 6,8 . The CDC model allows “real‐time” pharmacokinetic and pharmacodynamic responses facilitated by inlet and outlet ports for infusion of media/drugs and the collection of effluent media 9,10 . There have been numerous attempts to evaluate the antimicrobial effect on Staphylococcus aureus and enterococci ‐derived biofilms using CDC biofilm reactor models 11,12 .…”