Antibiotic resistant Achromobacter xylosoxidans are highly susceptible to bacteriophages and often are killed synergistically by phage/antibiotic combinations.

Achromobacter infections pose significant challenges to people with Cystic Fibrosis (CF). This microbe often becomes multidrug resistant (MDR) or extensively drug resistant (XDR), leaving physicians with few antibiotic treatment options. It is a growing problem in people with CF because it is difficult to eliminate with antibiotics, leading to chronic lung infections that increasingly acquire antibiotic resistance. We have been searching for alternative therapies for Achromobacter infection and identified a cadre of 26 bacteriophages (viruses that attack bacteria) that target it that could allow us to reduce reliance on antibiotics. We tested these phages against a collection of 56 MDR and XDR clinical Achromobacter isolates and found that all were susceptible to multiple of these phages. We also evaluated whether we could restore the activity of certain antibiotics by using them as adjunctive therapy to phage treatment in vitro. We found that when meropenem (a beta lactam antibiotic) was added to phage treatment, susceptibility to meropenem was demonstrated in many isolates regardless of whether the Achromobacter was initially susceptible to meropenem. The data presented here suggests that combination therapy using meropenem with an active phage should be considered for treatment of Achromobacter infections regardless of pre-existing antibiotic susceptibility.