Abstract
Bacterial biofilms are highly recalcitrant to antibiotic therapies due to multiple tolerance mechanisms. The involvement of Pseudomonas aeruginosa in a wide range of biofilm-related infections often leads to treatment failures. Indeed, few current antimicrobial molecules are still effective on tolerant sessile cells. In contrast, studies increasingly showed that conventional antibiotics can, at low concentrations, induce a phenotype change in bacteria and consequently, the biofilm formation. Understanding the clinical effects of antimicrobials on biofilm establishment is essential to avoid the use of inappropriate treatments in the case of biofilm infections. This article reviews the current knowledge about bacterial growth within a biofilm and the preventive or inducer impact of standard antimicrobials on its formation by P. aeruginosa. The effect of antibiotics used to treat biofilms of other bacterial species, as Staphylococcus aureus or Escherichia coli, was also briefly mentioned. Finally, it describes two in vitro devices which could potentially be used as antibiotic susceptibility testing for adherent bacteria.
Highlights
Bacterial biofilm was defined for the first time in 1978 as a structured community of microorganisms adhering to a surface and producing an extracellular matrix of polysaccharides (Costerton et al, 1978)
Concerning the positive effect of classic antimicrobial therapies on other sessile pathogens, minimal inhibitory concentration (MIC) and minimal bactericidal concentrations (MBCs) of rifampicin have demonstrated an activity against biofilms of Staphylococcus epidermidis and Staphylococcus aureus isolates associated with device infections, especially when it is used in association with other molecules as fusidic acid, vancomycin or ciprofloxacin in an in vitro biofilm model (Saginur et al, 2006)
Results showed that serum concentrations of cloxacillin, corresponding to the minimal biofilm inhibitory concentrations (MBICs) determined by Antibiofilmogram R (ATBFG), allowed reduction to 3 log the bacterial biomasses colonizing the catheters for three clinical strains, whereas the simple MICs of the antibiotic were inefficient on biofilm formation
Summary
Bacterial biofilm was defined for the first time in 1978 as a structured community of microorganisms adhering to a surface and producing an extracellular matrix of polysaccharides (Costerton et al, 1978). In a recent study, Otani et al (2018) showed that sub-MICs of ceftazidime reduce biofilm volume, inhibit twitching motility, and repress gene expression involved in bacterial adhesion and matrix production of P. aeruginosa PAO1.
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