Anti-biofilm and resistance suppression activities of CXA-101 against chronic respiratory infection phenotypes of Pseudomonas aeruginosa strain PAO1.
OBJECTIVE
Biofilm growth, mucoid phenotype and proficient resistance development by hypermutable strains dramatically limit the efficacy of current therapies for Pseudomonas aeruginosa chronic respiratory infection (CRI) in cystic fibrosis (CF) patients. We evaluated the activity of the new cephalosporin CXA-101, ceftazidime, meropenem and ciprofloxacin against biofilms of wild-type PAO1 and its mucoid (mucA), hypermutable (mutS) and mucoid-hypermutable derivatives, and analysed the capacity of these strains to develop resistance during planktonic and biofilm growth.


METHODS
MICs and MBCs were determined by microdilution, and mutant frequencies were determined at 4x and 16x the MICs. Biofilms were formed using a modified Calgary device and were incubated for 24 h with 0x, 1x, 4x or 16x the MIC of each antibiotic. Biofilms were plated, and total cells and resistant mutants enumerated.


RESULTS
CXA-101 showed concentration-independent biofilm bactericidal activity, being the most potent agent tested at 1x the MIC for wild-type, mucoid and hypermutable strains. The spontaneous mutant frequencies for CXA-101 were extremely low (<5 x 10(-11)), even for the hypermutable strain at low concentrations (4x the MIC), in sharp contrast to the other antipseudomonal agents. Accordingly, mutants resistant to 4x the MIC of CXA-101 did not emerge in biofilms for any of the strains/concentrations tested.


CONCLUSIONS
These data strongly suggest that resistance to CXA-101 (at least 4x the MIC) cannot be driven by single-step mutations, either in planktonic or in biofilm growth. CXA-101 shows encouraging properties for the treatment of CRI by P. aeruginosa, which need to be further evaluated in animal models and pertinent clinical trials.
Riera
Elena
E
Servicio de Microbiología and Unidad de Investigación, Hospital Son Dureta, Instituto Universitario de Investigación en Ciencias de la Salud (IUNICS), Palma de Mallorca, Spain.
Macià
María D
MD
Mena
Ana
A
Mulet
Xavier
X
Pérez
José L
JL
Ge
Yigong
Y
Oliver
Antonio
A
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D002511:Cephalosporins / Q000494:pharmacology*; D015169:Colony Count, Microbial; D024881:Drug Resistance, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D009154:Mutation; D010641:Phenotype; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000502:physiology; D012141:Respiratory Tract Infections / Q000382:microbiology*
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; C519491:ceftolozane