Stationary biofilm growth normalizes mutation frequencies and mutant prevention concentrations in Pseudomonas aeruginosa from cystic fibrosis patients

Bacterial biofilms play an important role in the persistent colonization of the respiratory tract in cystic fibrosis (CF) patients. The trade‐offs among planktonic or sessile modes of growth, mutation frequency, antibiotic susceptibility and mutant prevention concentrations (MPCs) were studied in a...

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Published in:	Clinical microbiology and infection 2011-05, Vol.17 (5), p.704-711
Main Authors:	García‐Castillo, M., del Campo, R., Baquero, F., Morosini, M.‐I., Turrientes, M.‐C., Zamora, J., Cantón, R.
Format:	Article
Language:	eng
Subjects:	Anti-Bacterial Agents - therapeutic use Biofilm Biofilms - drug effects Biological and medical sciences Ceftazidime - pharmacology Ciprofloxacin - pharmacology cystic fibrosis Cystic Fibrosis - drug therapy Cystic Fibrosis - microbiology Drug Resistance, Bacterial Errors of metabolism Genetic Variation Humans Imipenem - pharmacology Infectious diseases Medical sciences Metabolic diseases Microbial Sensitivity Tests Miscellaneous hereditary metabolic disorders mutant prevention concentrations Mutation mutation frequency Pseudomonas aeruginosa Pseudomonas aeruginosa - drug effects Pseudomonas aeruginosa - genetics Pseudomonas aeruginosa - physiology Pseudomonas Infections - drug therapy Pseudomonas Infections - genetics Pseudomonas Infections - microbiology Respiratory System - microbiology Tobramycin - pharmacology
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Summary:	Bacterial biofilms play an important role in the persistent colonization of the respiratory tract in cystic fibrosis (CF) patients. The trade‐offs among planktonic or sessile modes of growth, mutation frequency, antibiotic susceptibility and mutant prevention concentrations (MPCs) were studied in a well‐defined collection of 42 CF Pseudomonas aeruginosa isolates. MICs of ciprofloxacin, tobramycin, imipenem and ceftazidime increased in the biofilm mode of growth, but not the MPCs of the same drugs. The mutation frequency median was significantly higher in planktonic conditions (1.1 × 10−8) than in biofilm (9.9 × 10−9) (p 0.015). Isolates categorized as hypomutable increased their mutation frequency from 3.6 × 10−9 in the planktonic mode to 6 × 10−8 in biofilm, whereas normomutators (from 9.4 × 10−8 to 5.3 × 10−8) and hypermutators (from 1.6 × 10−6 to 7.7 × 10−7) decreased their mutation frequencies in biofilm. High and low mutation frequencies in planktonic growth converge into the normomutable category in the biofilm mode of growth of CF P. aeruginosa, leading to stabilization of MPCs. This result suggests that once the biofilm mode of growth has been established, the propensity of CF P. aeruginosa populations to evolve towards resistance is not necessarily increased.
ISSN:	1198-743X 1469-0691