Measuring antimicrobial susceptibility of Pseudomonas aeruginosa using Poloxamer 407 gel
Hiroyuki Yamada1, Naohito Koike, Tomoko Ehara
1Department of Microbiology, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo, 160-8402, Japan.
Abstract:
Pseudomonas aeruginosa is a Gram-negative bacterium that causes various opportunistic infections. Chronic and intractable infections with P. aeruginosa are closely related to the high levels of resistance displayed by this organism to antimicrobial agents and its ability to form biofilms. Although the standard method for examining antimicrobial resistance involves susceptibility testing using Mueller-Hinton agar or broth, this method does not take into account the influence of biofilm formation on antimicrobial susceptibility. Poloxamer 407 is a hydrophilic, nonionic surfactant of the more general class of copolymers that can be used to culture bacteria with similar properties as cells in a biofilm environment. Therefore, the aim of this study was to compare the antimicrobial susceptibility of bacteria cultured in Poloxamer 407 gel to those grown on Mueller-Hinton agar using the Kirby-Bauer disk diffusion method with 24 strains of P. aeruginosa. Antimicrobial sensibility differed between the two mediums, with >60% of the strains displaying increased resistance to β-lactams when cultured on Poloxamer 407 gel. In addition, scanning electron microscopy revealed that typical biofilm formation and extracellular polymeric substance production was only observed with bacteria grown on Poloxamer 407 gel. Therefore, antimicrobial susceptibility test using Poloxamer 407 gel may provide more accurate information and allow the selection of suitable antimicrobial agents for treating patients infected with biofilm-forming pathogens.
Insights
Poloxamer 407 gel culture better mimics Pseudomonas aeruginosa biofilms than standard methods. This approach reveals increased antimicrobial resistance, aiding treatment selection for biofilm-related infections.
Area of Science:
- Microbiology
- Bacteriology
- Antimicrobial Resistance
Background:
- Pseudomonas aeruginosa causes opportunistic infections, often intractable due to antimicrobial resistance and biofilm formation.
- Standard antimicrobial susceptibility testing (AST) methods do not fully account for biofilm's impact on resistance.
- Biofilm formation is a critical factor in persistent bacterial infections.
Purpose of the Study:
- To compare antimicrobial susceptibility of P. aeruginosa cultured in Poloxamer 407 gel versus Mueller-Hinton agar.
- To evaluate Poloxamer 407 gel as a model for biofilm-related antimicrobial susceptibility testing.
- To assess the influence of biofilm formation on P. aeruginosa resistance to beta-lactams.
Main Methods:
- Utilized the Kirby-Bauer disk diffusion method for AST.
- Cultured 24 strains of P. aeruginosa on Poloxamer 407 gel and Mueller-Hinton agar.
- Employed scanning electron microscopy (SEM) to visualize biofilm formation and extracellular polymeric substance (EPS) production.
Main Results:
- >60% of P. aeruginosa strains showed increased resistance to beta-lactams when cultured in Poloxamer 407 gel.
- Typical biofilm formation and EPS production were observed only in bacteria cultured on Poloxamer 407 gel.
- Significant differences in antimicrobial susceptibility were noted between the two culture mediums.
Conclusions:
- Poloxamer 407 gel culture provides a more accurate model for P. aeruginosa biofilm-related AST.
- This method may improve the selection of effective antimicrobial agents for biofilm-forming infections.
- Standard AST methods may underestimate resistance in biofilm-forming pathogens like P. aeruginosa.
