Antimicrobial Susceptibility Testing in Pseudomonas aeruginosa Biofilms: One Step Closer to a Standardized Method
Carmen Lozano1, María López1, Beatriz Rojo-Bezares1
1Área de Microbiología Molecular, Centro de Investigación Biomédica de La Rioja (CIBIR), 26006 Logroño, Spain.
Abstract:
The ability of Pseudomonas aeruginosa to form biofilm during a long-term infection makes it difficult to treat patients correctly. The current clinical antimicrobial susceptibility testing methods are based on the study of planktonic strains. A standardized protocol to analyze the antimicrobial susceptibility in biofilms is necessary for routine laboratories. The aims of this study were to develop a simple biofilm model and to study the antimicrobial susceptibility of P. aeruginosa strains in biofilm growth. Different artificial sputum media, and aerobiosis and microaerobiosis conditions were analyzed using a microtiter plate method and P. aeruginosa PAO1 as reference strain. Planktonic and biofilm antimicrobial susceptibility to cefepime, imipenem, azithromycin, gentamicin, tobramycin, and ciprofloxacin were determined in clinical and non-clinical P. aeruginosa strains. The Synthetic Cystic Fibrosis Medium was proposed as a good medium. The biofilm greatly increased the resistance to tested antimicrobials, except for azithromycin. Cefepime and imipenem showed poor anti-biofilm effect while tobramycin, gentamicin, and ciprofloxacin showed good activity in some strains. Azithromycin showed a better activity in biofilm than in planktonic state when aerobic conditions were used. This study establishes useful information to test antimicrobial susceptibility in P. aeruginosa biofilms, and includes possible antimicrobial options to treat long-term infected patients.
Insights
Pseudomonas aeruginosa biofilms significantly increase antimicrobial resistance, complicating treatment. This study developed a simple biofilm model to test susceptibility, revealing tobramycin, gentamicin, and ciprofloxacin as potentially effective options.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Pseudomonas aeruginosa biofilm formation poses challenges in treating chronic infections.
- Current antimicrobial susceptibility testing (AST) methods, focusing on planktonic bacteria, are inadequate for biofilms.
- A standardized protocol for biofilm AST is crucial for clinical laboratories.
Purpose of the Study:
- To develop a simple biofilm model for P. aeruginosa.
- To assess antimicrobial susceptibility of P. aeruginosa within biofilms.
- To identify potential antimicrobial agents for biofilm-related infections.
Main Methods:
- A microtiter plate method was used to establish a biofilm model.
- Synthetic Cystic Fibrosis Medium (SCFM) and various oxygen conditions were tested.
- Antimicrobial susceptibility testing (AST) for planktonic and biofilm states was performed using cefepime, imipenem, azithromycin, gentamicin, tobramycin, and ciprofloxacin.
Main Results:
- Synthetic Cystic Fibrosis Medium proved effective for biofilm development.
- Biofilms generally enhanced bacterial resistance to antimicrobials, with azithromycin being an exception.
- Cefepime and imipenem exhibited limited anti-biofilm activity.
- Tobramycin, gentamicin, and ciprofloxacin demonstrated strain-dependent efficacy against biofilms.
- Azithromycin showed improved activity in biofilms under aerobic conditions compared to planktonic states.
Conclusions:
- This study provides valuable data for routine biofilm antimicrobial susceptibility testing.
- The findings suggest potential antimicrobial strategies for treating P. aeruginosa biofilm infections.
- A simple biofilm model can aid in optimizing treatment for chronic P. aeruginosa infections.
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