Comparison of the In vitro Activity of Five Antimicrobial Drugs against Staphylococcus pseudintermedius and Staphylococcus aureus Biofilms

Abstract

Resistance in canine pathogenic staphylococci is necessitating re-evaluation of the current antimicrobial treatments especially for biofilm-associated infections. Long, repeated treatments are often required to control such infections due to the tolerance of bacteria within the biofilm. To comply with the goal of better antibiotic stewardship in veterinary medicine, the efficacies of the available drugs need to be directly assessed on bacterial biofilms. We compared the activities of amoxicillin, cefalexin, clindamycin, doxycycline, and marbofloxacin on in vitro biofilms of Staphylococcus pseudintermedius and Staphylococcus aureus. Exposure of biofilms for 15 h to maximum concentrations of the antibiotics achievable in canine plasma only reduced biofilm bacteria by 0.5–2.0 log10 CFU, compared to the control, except for marbofloxacin which reduced S. aureus biofilms by 5.4 log10 CFU. Two-antibiotic combinations did not improve, and even decreased, bacterial killing. In comparison, 5 min-exposure to 2% chlorhexidine reduced biofilms of the two tested strains by 4 log10 CFU. Our results showed that S. pseudintermedius and S. aureus biofilms were highly tolerant to all the drugs tested, consistent with the treatment failures observed in practice. Under our in vitro conditions, the use of chlorhexidine was more efficacious than antimicrobials to reduce S. pseudintermedius biofilm.

Antibacterial Liquid Metals: Biofilm Treatment via Magnetic Activation

“…The efficacy of the magnetically activated GLM-Fe particles was compared to that of three conventional antibiotics: amoxicillin, clindamycin, and tetracycline. Here, mature biofilms of S. aureus and P. aeruginosa were exposed individually to concentrations of the respective antibiotics at and/or above the minimum inhibition concentrations (MIC) and 100× the therapeutic dose level, as previously determined. , It should be noted that P. aeruginosa is thought to be innately resistant to clindamycin and amoxicillin; however, for tetracycline it is susceptible at concentrations of ∼32 μg/mL. Here we tested at higher concentrations of 50 μg/mL and 5 mg/mL, to thoroughly compare the efficacy of the antibiotics compared to the GLM-Fe particles.…”

Complications and survival after subcutaneous ureteral bypass device placement in 24 cats: a retrospective study (2016–2019)

“…28 Based on in vitro data, marbofloxacin seems more likely to prevent biofilm formation than amoxicillin, cefalexin, doxycycline and clindamycin. 36 Likewise, in humans, fluoroquinolones are considered to be effective in preventing biofilm formation on ureteral stents. 37 Our results were different, as all cats with persistent/recurrent UTI postoperatively received postoperative marbofloxacin, while the two cats in which antimicrobials were discontinued immediately postoperatively did not develop a UTI.…”

Anti-biofilm activity of Thai herbal essential oils against Staphylococcus pseudintermedius causing canine pyoderma

“…Manuka EO concentrations of 7.8-800 times the MIC (0.1% w/v) inhibited formation of biofilms by 76.2%. The study of Ferran et al [35] showed the inhibitory effect of antibiotics such as marbofloxacin (0.00005% w/v), clindamycin (0.001% w/v), doxycycline (0.001% w/v), amoxicillin (0.002% w/v) and cefalexin (0.005% w/v) against S. pseudintermedius biofilms was 1.2-1.4 times lower than that against planktonic cells.…”