Effect of Different Antibiotic Chemotherapies on Pseudomonas aeruginosa Infection In Vitro of Primary Human Corneal Fibroblast Cells.

Maria Del Mar Cendra,Myron Christodoulides,Parwez Hossain

doi:10.3389/fmicb.2017.01614

Abstract

Pseudomonas aeruginosa is a major cause of bacterial keratitis (BK) worldwide. Inappropriate or non-optimal antibiotic chemotherapy can lead to corneal perforation and rapid sight loss. In this study, we tested the hypothesis that P. aeruginosa strain PAO1 invades primary human corneal fibroblasts (hCFs) in vitro and persists intracellularly, despite chemotherapy with antibiotics used commonly to treat BK. In rank order, ciprofloxacin, levofloxacin and polymyxin B showed the highest activity against planktonic PAO1 growth (100% inhibitory concentration ≤10 μg/mL; 50% inhibitory concentration ≤1 μg/mL), followed by gentamicin and ofloxacin (100% inhibitory concentration ≤50 μg/mL; 50% inhibitory concentration ≤10 μg/mL). These bactericidal antibiotics (50–200 μg/mL concentrations) all killed PAO1 in the extracellular environment of infected hCF monolayers. By contrast, the bactericidal antibiotic cefuroxime and the bacteriostatic antibiotic chloramphenicol failed to sterilize both PAO1 broth cultures, even at a concentration of ≥200 μg/mL) and infected hCF monolayers. Statistically, all antibiotics were able to prevent LDH release from PAO1-infected hCF monolayers at both concentrations tested. Intracellular Pseudomonas were significantly reduced (>99%, P < 0.05) following treatment with ciprofloxacin, levofloxacin and ofloxacin, whereas gentamicin, polymyxin B and cefuroxime failed to clear intracellular bacteria over 24 h. Intracellular Pseudomonas infection was resistant to chloramphenicol, with hCF death observed by 9 h. Eventual growth of remaining intracellular Pseudomonas was observed in hCF after removal of all antibiotics, resulting in re-infection cycles and cell death by 48 h. All of the antibiotics reduced significantly (P < 0.05) IL-1β secretion by hCF infected with a Multiplicity Of Infection (MOI) = 1 of PAO1. With higher MOI, no pro-inflammatory effects were observed with antibiotic treatment, expect with polymyxin B and ofloxacin, which induced significant increased IL-1β secretion (P < 0.001). The findings from our study demonstrated that bactericidal and bacteriostatic antibiotics, routinely used to treat BK, failed to eradicate Pseudomonas infection of hCFs in vitro and that their bactericidal efficacies were influenced by the cellular location of the organism.

Highlights

Pseudomonas aeruginosa is the leading cause of bacterial keratitis (BK) associated with contact lens wear (Shah et al, 2011; Stapleton and Carnt, 2012)
We used an in vitro model of primary human primary corneal fibroblasts (hCFs) cells derived from the stroma, to evaluate current antibiotic treatments used in the United Kingdom to treat eye infections
LB broth could support the planktonic growth of P. aeruginosa PAO1 over time in the absence of antibiotics (Supplementary Figure S2)

Summary

Introduction

Pseudomonas aeruginosa is the leading cause of bacterial keratitis (BK) associated with contact lens wear (Shah et al, 2011; Stapleton and Carnt, 2012). A healthy cornea is inherently resistant to microbial infections but when the epithelium is breached, e.g., following surgery, trauma or contact lens wear, microbes can penetrate and gain access to the stroma (Taube et al, 2015). Overstimulation of the inflammatory response is a common issue during BK treatment (Taube et al, 2015). It is not known if different antibiotic regimens have inherent inflammatory effects that may impact on the corneal healing response. Corticosteroids are known to possess anti-inflammatory properties, but their use is not recommended until infection is cleared (Gokhale, 2008)

Methods

Results

Conclusion