Disruption of Membrane by Colistin Kills Uropathogenic Escherichia coli Persisters and Enhances Killing of Other Antibiotics

Abstract

cPersisters are small populations of quiescent bacterial cells that survive exposure to bactericidal antibiotics and are responsible for many persistent infections and posttreatment relapses. However, little is known about how to effectively kill persister bacteria. In the work presented here, we found that colistin, a membrane-active antibiotic, was highly active against Escherichia coli persisters at high concentrations (25 or 50 g/ml). At a clinically relevant lower concentration (10 g/ml), colistin alone had no apparent effect on E. coli persisters. In combination with other drugs, this concentration of colistin enhanced the antipersister activity of gentamicin and ofloxacin but not that of ampicillin, nitrofurans, and sulfa drugs in vitro. The colistin enhancement effect was most likely due to increased uptake of the other antibiotics, as demonstrated by increased accumulation of fluorescence-labeled gentamicin. Interestingly, colistin significantly enhanced the activity of ofloxacin and nitrofurantoin but not that of gentamicin or sulfa drugs in the murine model of urinary tract infection. Our findings suggest that targeting bacterial membranes is a valuable approach to eradicating persisters and should have implications for more effective treatment of persistent bacterial infections. P ersisters are a small fraction of nonreplicating, metabolically quiescent bacteria that survive the lethal action of bactericidal antibiotic treatment and can potentially regrow after antibiotic removal, while remaining susceptible to the same antibiotic (1, 2). Persister cells are thought to be responsible for many persistent bacterial infections, such as tuberculosis (3), urinary tract infections (UTIs) (4), and biofilm infections (5). These infections require prolonged treatment, have a high risk of relapse, and can lead to genetic antibiotic resistance during prolonged and repeated treatment.Although the persister phenomenon was first discovered in the 1940s (6, 7), only recently did we begin to understand the molecular mechanisms of persisters (1,8,9). Common antibiotics that inhibit macromolecule synthesis generally have poor activity against persister bacteria, and how the persister bacteria survive treatment with current antibiotics is still unclear. Theoretically, at least two possibilities exist: one is that the drugs cannot enter the persister cells, and the other is that the drugs enter the persister cells but cannot generate lethal effects as they do in growing cells. Work on Mycobacterium tuberculosis demonstrated that the intracellular concentrations of many antibiotics were considerably lower in nonreplicating bacteria than in replicating bacilli (10). Consistent with this observation, increasing the uptake of aminoglycosides by using mannitol (11) and silver (12) was shown to enhance the killing of bacterial persisters by gentamicin. Based on these observations, it is reasonable to postulate that lack of antibiotic entry may play an important role in the survival of persisters during antibiotic exposure and...

Identification of essential oils with strong activity against stationary phase uropathogenic Escherichia coli

“…While commonly used antibiotics for UTIs exhibited effective inhibitory effect on multiplying and free-living log phase E. coli , they demonstrated very limited activity against aggregated E. coli at stationary phase [8, 15, 16]. Our previous study with persister drug colistin in combination with gentamicin or fluoroquinolone drug indicated the importance of including persister drugs for more effective treatment of persistent UTIs in the mouse model [9]. In line with this thinking, in this study, we screened a panel of essential oils as suitable alternatives for more effective elimination of persister bacteria for improved treatment of recurrent UTIs.…”

“…In our previous study, we have screened an FDA-approved drug library and found some active hits such as tosufloxacin and colistin to be highly active against stationary phase culture of uropathogenic E. coli UTI89 strain [8]. The importance of including drugs that target persister bacteria has been demonstrated with persister drug colistin in a persistent UTI mouse model [9]. However, the choice of persister drugs that may be useful is quite limited from the FDA drug library screen [8].…”

UroPathogenic Escherichia coli (UPEC) Infections: Virulence Factors, Bladder Responses, Antibiotic, and Non-antibiotic Antimicrobial Strategies

“…New antibiotics, such as colistin (Cui et al, 2016 ), finafloxacin, and cefiderocol (S-649266), which are currently in early clinical development, might be useful in the treatment of UTIs (Zacché and Giarenis, 2016 ).…”

Identification of novel genes including rpmF and yjjQ critical for Type II persister formation in Escherichia coli

“…Further experiments should be performed to detect the effects of these metabolic pathways on ATP production. Membrane and membrane proteins have previously been shown to participate in persistence (Cui et al, 2016; Guo et al, 2017), and our data indicate that their roles in persister formation may be far more important and complicated than previously thought, and changes to lowermembrane permeability to drugs has been noted in some dormant bacteria (Dick T, 2015)…”