Clinical Impact of Antibiotics for the Treatment of Pseudomonas aeruginosa Biofilm Infections

Abstract

Bacterial biofilms are highly recalcitrant to antibiotic therapies due to multiple tolerance mechanisms. The involvement of Pseudomonas aeruginosa in a wide range of biofilmrelated 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.

Synergistic effects of pomegranate and rosemary extracts in combination with antibiotics against antibiotic resistance and biofilm formation of Pseudomonas aeruginosa

“…Next, the established biofilms were measured at 570 nm against blank (95% ethanol) using a micro-titer plate reader (Shcheer SH9600-Shanghai) [13]. Based on ODs, the biofilm formation were classified into 3 categories as weak (OD 570nm ≤ 0.5), intermediate (0.5 > OD 570nm < 1.5), and strong (OD 570nm ≥ 1.5) [14] .…”

“…The susceptibility of P. aeruginosa isolates to 13 different antibiotic disks (IPM, CDZ, FEP, CN, NOR, OFX, CIP, LEV, AK, GAT, NA, PRL, and TOB) was investigated by disk diffusion method [15]. Briefly, a sterile cotton wool swab was dipped into the bacterial suspension (adjusted to 1 × 10 6 cfu/ml) and spread evenly on the surface of sterile MHA plate and allowed to dry before placing the antibiotic disks.…”

“…Wells dispensed with 200 μL of and inoculated MHB containing 0.5% DMSO were considered as negative and positive controls, respectively. The MIC values of used antibiotics were interpreted as the lowest concentration of tested antibiotic that prevented visible growth after 24 h of incubation at 37°C [16,17].…”

“…The MIC of plant extract was interpreted as the lowest concentration of the extract that prevented visible growth after 24 h of incubation at 37°C. The MBC of plant extract was interpreted as the lowest concentration of the extract that killed 100% of bacterial inoculum after 24 h of incubation at 37°C [16,17].…”

“…Pseudomonas aeruginosa is the most frequent opportunistic Gram-negative rods; it is capable of infecting variety of all tissues and becoming a major cause's morbidity and mortality among hospital patients. It is the second causative agent of nosocomial pneumonia, the third common bacterial pathogen of urinary tract infection, the fourth common causes of surgical site infection, the fifth most frequently isolated pathogen from all sites, and the seventh regular pathogen isolated from the bloodstream [1] .…”