Phage selection restores antibiotic sensitivity in MDR Pseudomonas aeruginosa

Abstract

Increasing prevalence and severity of multi-drug-resistant (MDR) bacterial infections has necessitated novel antibacterial strategies. Ideally, new approaches would target bacterial pathogens while exerting selection for reduced pathogenesis when these bacteria inevitably evolve resistance to therapeutic intervention. As an example of such a management strategy, we isolated a lytic bacteriophage, OMKO1, (family Myoviridae) of Pseudomonas aeruginosa that utilizes the outer membrane porin M (OprM) of the multidrug efflux systems MexAB and MexXY as a receptor-binding site. Results show that phage selection produces an evolutionary trade-off in MDR P. aeruginosa, whereby the evolution of bacterial resistance to phage attack changes the efflux pump mechanism, causing increased sensitivity to drugs from several antibiotic classes. Although modern phage therapy is still in its infancy, we conclude that phages, such as OMKO1, represent a new approach to phage therapy where bacteriophages exert selection for MDR bacteria to become increasingly sensitive to traditional antibiotics. This approach, using phages as targeted antibacterials, could extend the lifetime of our current antibiotics and potentially reduce the incidence of antibiotic resistant infections.

Rapid evolution of generalized resistance mechanisms can constrain the efficacy of phage–antibiotic treatments

“…This is in contrast with previous studies reporting beneficial effects of phage–antibiotic combinations on Escherichia coli biofilms (Ryan, Alkawareek, Donnelly, & Gilmore, 2012) and planktonic P. aeruginosa cultures (Torres‐Barceló et al., 2016). However, phage–antibiotic effects are not always observed (Verma et al., 2009), which could be due to the specific phage species and class of antibiotic as PAS often requires mechanistic compatibility between the two (Chan et al., 2016; Comeau et al., 2007; Kamal & Dennis, 2015). For example, it has recently been reported that associations between phage and gentamycin resistance are predominantly positive, while associations between phage and ciprofloxacin resistance are mainly negative with natural and clinical E. coli isolates (Allen, Pfrunder‐Cardozo, Meinel, Egli, & Hall, 2017).…”

“…Positive correlation between phage selection and antibiotic resistance is in contrast with previous studies showing an opposite effect where phage treatment reduced the emergence of antibiotic resistance (Jalasvuori, Friman, Nieminen, Bamford, & Buckling, 2011; Zhang & Buckling, 2012). One explanation for this discrepancy is that phage–antibiotic synergies could be very specific to the given phage species and type of antibiotics, whereas antibiotic selection‐mediated susceptibility to phages could have been driven by some degree of collateral sensitivity (Chan et al., 2016; Comeau et al., 2007; Kamal & Dennis, 2015). …”

“…PAS is thought to occur because two sufficiently different selective pressures are more likely to kill both nonresistant (susceptible to antibiotics) and antibiotic‐resistant (susceptible to phages) pathogen genotypes (Torres‐Barceló & Hochberg, 2016). Moreover, two concurrently acting selection pressures might impose evolutionary trade‐offs for the pathogen, which could constrain the evolution of resistance to antibiotics, phage or both (Chan et al., 2016; Torres‐Barceló & Hochberg, 2016; Wang et al., 2017). Here, we studied this using a model system where we exposed P. aeruginosa pathogen to both phage and sublethal concentration of gentamycin and monitored ecological and evolutionary dynamics in both homogenous (planktonic) and spatial (biofilm) dimensions of the microcosms.…”

“…For example, a Pseudomonas aeruginosa ‐specific phage has been reported to use outer membrane porin M (OprM) of the multidrug efflux systems MexAB and MexXY as a receptor‐binding site (Chan et al., 2016). Mutations that change the structure of these receptors has been shown to confer P. aeruginosa resistance to phages, but at the same time increase its susceptibility to antibiotics due to its less functional efflux pump (Chan et al., 2016). In the same way, it has recently been reported that phage selection can make Ralstonia solanacearum plant pathogenic bacterium more susceptible to antibiotics produced by Bacillus amyloliquefaciens biocontrol bacterium even though the mechanism has not yet been described in detail (Wang et al., 2017).…”

La phagothérapie

“…Ainsi, en cas d'utilisation large, l'impact écologique de la phagothérapie sur les populations bactériennes devra faire l'objet d'une surveillance adéquate de façon à ne pas reproduire les erreurs du passé observées avec les antibiotiques. Par ailleurs, dans certains cas, l'apparition de la résistance aux phages peut s'accompagner d'une diminution ou d'une perte de la virulence bactérienne [25][26][27], ou d'une re-sensibilisation de la bactérie à des antibiotiques auxquels elle était initialement résistante [28]. Enfin, compte tenu de la grande diversité virale existante, l'acquisition d'une résistance est de moindre portée que pour les antibiotiques : la recherche d'un nouveau phage actif s'avère beaucoup plus aisée et rapide que celle d'une nouvelle molécule antibiotique.…”