Development of Antibiotic Resistance during Simulated Treatment of Pseudomonas aeruginosa in Chemostats.

Yanfang Feng,Stanley Brul,Constance Schultsz,Reinier M Van Hest,Benno H Ter Kuile,Caspar J Hodiamont,Hendrik W Van Veen

doi:10.1371/journal.pone.0149310

Abstract

During treatment of infections with antibiotics in critically ill patients in the intensive care resistance often develops. This study aims to establish whether under those conditions this resistance can develop de novo or that genetic exchange between bacteria is by necessity involved. Chemostat cultures of Pseudomonas aeruginosa were exposed to treatment regimes with ceftazidime and meropenem that simulated conditions expected in patient plasma. Development of antibiotic resistance was monitored and mutations in resistance genes were searched for by sequencing PCR products. Even at the highest concentrations that can be expected in patients, sufficient bacteria survived in clumps of filamentous cells to recover and grow out after 3 to 5 days. At the end of a 7 days simulated treatment, the minimal inhibitory concentration (MIC) had increased by a factor between 10 and 10,000 depending on the antibiotic and the treatment protocol. The fitness costs of resistance were minimal. In the resistant strains, only three mutations were observed in genes associated with beta-lactam resistance. The development of resistance often observed during patient treatment can be explained by de novo acquisition of resistance and genetic exchange of resistance genes is not by necessity involved. As far as conclusions based on an in vitro study using P. aeruginosa and only two antibiotics can be generalized, it seems that development of resistance can be minimized by treating with antibiotics in the highest concentration the patient can endure for the shortest time needed to eliminate the infection.

Highlights

Antimicrobial treatment of critically ill patients in the intensive care is often complicated by antimicrobial resistance (AMR) development of the targeted microorganisms, even thoughPLOS ONE | DOI:10.1371/journal.pone.0149310 February 12, 2016Development of Antibiotic Resistance during Simulated Treatment these were susceptible at the start of treatment [1]
The 5, 50, and 95 percentile concentration-time profiles resulting from the computer-simulations, which are representative for the expected concentration-time profiles in critically ill patients, were mimicked for each antibiotic in the chemostat
There was considerable inter-individual variation in the concentrations calculated for patients, which is illustrated by the large difference between the 5 and 95 percentile values for both antibiotics

Summary

Introduction

Development of Antibiotic Resistance during Simulated Treatment these were susceptible at the start of treatment [1]. The acquired resistance complicates any further antimicrobial treatment that might be needed and can endanger the health of the patient in the case of recurring infections and should be prevented as much as possible. Antibiotic resistance can be acquired by transfer of genetic information between bacteria at the infection site, or it can develop de novo through genetic mutations, as a result of exposure to the drug [5,6]. Due to the complexity of all potential and actual interactions between microbes at an infection site, it is not possible to ascertain with certainty the occurrence of de novo development of resistance in patients during treatment. Simulation of the treatment in chemostats, can provide the necessary controlled and reproducible conditions

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