Bacterial Replication Rate Modulation in Combination with Antimicrobial Therapy: Turning the Microbe against Itself

Abstract

A major clinical challenge for treating infectious diseases is the duration of antimicrobial therapy required to eradicate the pathogen. We hypothesized that modulation of the bacterial replication rate in the context of an antimicrobial exposure is coupled with the rate and extent of bactericidal effects. Herein we describe results from in vitro infection model (one compartment, 24-h model; hollow fiber, 10-day model) studies designed to probe the relationship between the bacterial replication rate and the rate and extent of bactericidal effects in the context of an effective antibiotic exposure. The bacterial replication rate was modulated by adjusting the sodium chloride concentration (0 to 8%) in the growth media (Mueller-Hinton II broth). The study drug selected was levofloxacin, and the challenge isolate was Staphylococcus aureus ATCC 29213 (levofloxacin MIC, 0.125 mg/liter). Within each in vitro infection model, human levofloxacin concentration-time profiles (half-life, 7 h) were simulated and the challenge isolate was subjected to an effective exposure (free-drug area under the concentration-time curve over 24 h divided by the MIC [AUC/MIC ratio], 65; administered as a single dose or daily for 10 days). Over the course of each study, samples were taken from each model for bacterial density determinations and drug concentration assay using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In the 24-h one-compartment in vitro infection model studies, as the bacterial replication rate increased, so too did the rate (slope, 0 to 4 h) and extent (24-h CFU count per milliliter) of bacterial killing. In the 10-day hollow-fiber infection model studies, the times until a reduction of bacterial density to 1 ϫ 10 2 CFU/ml occurred were 10 days in the media in which the challenge isolate grew slowly and approximately 2 days in the media in which the challenge isolate grew rapidly. Together, these data provide a proof of concept for new adjunctive therapeutic options with respect to the use of antimicrobial agents alone that reduce treatment durations. Such adjunctive therapies hold promise for marked reductions in the tonnage of antimicrobial agents administered to patient populations and selection pressure toward antimicrobial resistance.

Apotransferrin in Combination with Ciprofloxacin Slows Bacterial Replication, Prevents Resistance Amplification, and Increases Antimicrobial Regimen Effect

“…With regard to bacterial-growth-rate modulation, recent studies have suggested that speeding up bacterial replication in the context of effective antimicrobial exposure increases the rate and extent of bactericidal activity and shortens therapy duration (5,6). In the context of ineffective antimicrobial exposure, such regimens increased bactericidal activity early in the course of therapy but ultimately failed due to antibioticresistant bacterial subpopulations (6).…”

Antibacterial Drug Development: A New Approach Is Needed for the Field to Survive and Thrive

“…There has been renewed interest in therapeutic and adjuvant alternatives to small molecule antibacterial agents. Among these are phage therapies [19,20], virulence inhibitors [19,21], bacterial growth rate modulators [22][23][24], monoclonal antibodies [25][26][27], and other approaches for meeting the challenge of antibiotic resistance. Of the 37 programs in the CARB-X portfolio for antibacterial treatment, over 48% are alternatives to traditional small molecule antibacterial agents [28].…”

Norepinephrine in Combination with Antibiotic Therapy Increases both the Bacterial Replication Rate and Bactericidal Activity

“…W e previously evaluated the relationship between the bacterial replication rate and the rate and extent of bactericidal effects in the context of an effective antibiotic exposure (1). In brief, the studies utilized in vitro infection models (a one-compartment, 24-h model; a hollow-fiber, 10-day model) where the bacterial replication rate was modulated using sodium chloride.…”