title: Antimicrobial activity of fosfomycin and tobramycin in combination against cystic fibrosis pathogens under aerobic and anaerobic conditions.
abstract: BACKGROUND
  There is a need for new antibiotics or combination of antibiotics that possess activity against increasingly resistant cystic fibrosis (CF) respiratory pathogens such as Pseudomonas aeruginosa and MRSA.
  
  
  METHODS
  The antimicrobial activity of a novel 4:1 (w/w) fosfomycin:tobramycin (F:T) combination against CF respiratory pathogens under both aerobic and anaerobic conditions was determined by MIC, time-kill and biofilm studies, and compared with activity of fosfomycin and tobramycin, individually.
  
  
  RESULTS
  F:T and fosfomycin had excellent activity against P. aeruginosa and were more active than tobramycin against P. aeruginosa under anaerobic conditions with lower MIC(50), MIC(90) and geometric mean values. F:T (p<0.001) and fosfomycin (p<0.001) MICs for P. aeruginosa were significantly lower under anaerobic conditions with tobramycin MICs significantly higher (p<0.001). F:T and fosfomycin also had high activity against MRSA with both being more active than tobramycin. In time-kill studies, F:T was rapidly bactericidal against all 15 P. aeruginosa and 3/5 MRSA isolates tested. F:T also demonstrated bactericidal activity against P. aeruginosa grown in biofilm under both aerobic and anaerobic conditions.
  
  
  CONCLUSIONS
  F:T has promising in vitro antimicrobial activity against MRSA and P. aeruginosa with greater activity under anaerobic conditions similar to those found in the CF lung.
authors.affiliation: CF and Airways Microbiology Research Group, Queen's University Belfast, United Kingdom.
authors.forename: Gerard
authors.initials: G
authors.lastname: McCaughey
authors.forename: Matt
authors.initials: M
authors.lastname: McKevitt
authors.forename: J Stuart
authors.initials: JS
authors.lastname: Elborn
authors.forename: Michael M
authors.initials: MM
authors.lastname: Tunney
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D018441:Biofilms / Q000187:drug effects*; D015169:Colony Count, Microbial; D003550:Cystic Fibrosis / Q000150:complications / Q000188:drug therapy / Q000382:microbiology*; D004338:Drug Combinations; D005578:Fosfomycin / Q000494:pharmacology*; D006801:Humans; D008168:Lung / Q000382:microbiology*; D055624:Methicillin-Resistant Staphylococcus aureus; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability; D011552:Pseudomonas Infections / Q000150:complications / Q000188:drug therapy / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000502:physiology; D013203:Staphylococcal Infections / Q000150:complications / Q000188:drug therapy / Q000382:microbiology; D014031:Tobramycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D005578:Fosfomycin; D014031:Tobramycin