Evaluation of synergistic activity of bovine lactoferricin with antibiotics in corneal infection

Abstract

Objectives: The objectives of this study were to determine whether a synergistic effect could be obtained in vitro between bovine lactoferricin (B-LFcin) and antibiotics against Pseudomonas aeruginosa and Staphylococcus aureus isolates from ocular infections, and to evaluate the use of B-LFcin as an adjunct to the antibiotic treatment of corneal infection in vivo.Methods: Chequerboard and time -kill assays were performed to investigate the combined effects of B-LFcin and conventional antibiotics, including ciprofloxacin, ceftazidime and gentamicin, against 17 strains of P. aeruginosa (8) and S. aureus (9) isolated from ocular infection and inflammation, and 1 reference strain of S. aureus. Corneas of C57BL/6 mice were topically challenged with a multidrug-resistant strain of P. aeruginosa. Nine hours post-challenge, mice were treated topically and hourly with either vehicle, B-LFcin, ciprofloxacin or ciprofloxacin containing B-LFcin for 8 h. Corneas were then clinically examined, and bacterial numbers and levels of myeloperoxidase (MPO) evaluated.Results: Synergy between B-LFcin and ciprofloxacin or ceftazidime was identified in most P. aeruginosa isolates, including multidrug-resistant strains, whereas no synergistic effect was seen between B-LFcin and gentamicin. Synergy was only observed with B-LFcin and ciprofloxacin against 2/10 S. aureus strains, and there was no synergy between B-LFcin and any of the other antibiotics tested. Combined B-LFcin and ciprofloxacin treatment significantly improved the clinical outcome, and reduced bacterial numbers and MPO in infected mouse corneas. B-LFcin alone was also able to reduce levels of MPO in infected corneas.Conclusions: These findings indicate that B-LFcin may have advantages as an adjunct therapy with both antimicrobial and anti-inflammatory properties in the treatment of corneal infection. Keywords: keratitis, Pseudomonas aeruginosa, Staphylococcus aureus, ciprofloxacin IntroductionSince their introduction, antibiotics have been the mainstay of treatment for bacterial infections.1 However, increasing bacterial resistance to antimicrobials is rapidly becoming a major public health concern.2,3 In response to increasing bacterial resistance, the fluoridated 4-quinolones, such as ciprofloxacin, were introduced in the 1980s. Now, there are increasing reports of resistance to this class of drugs in clinical isolates, particularly Pseudomonas aeruginosa and Staphylococcus aureus, with high levels of resistance being reported in cases of microbial keratitis. 4 Microbial keratitis is a relatively rare but severe disease of the cornea, which can lead to blindness and vision loss as a result of scarring or perforation of the cornea if appropriate antibiotic therapy is not rapidly instituted. S. aureus is the most common pathogen associated with microbial keratitis of all causes, 5 while P. aeruginosa is regarded as a major causative pathogen for contact lens-associated microbial keratitis and represents 40% -70% of clinical isolates from microbial keratitis associated with...

Antimicrobial Activity of Lactoferrin-Related Peptides and Applications in Human and Veterinary Medicine

“…Recently, Oo et al [86] reported that two antibiotics (ciprofloxacin and ceftazidime) act synergistically with bLfcin against various strains of P. aeruginosa isolated from corneal infections in vitro. In mouse corneas, the addition of bLfcin as adjuvant enhanced the activity of ciprofloxacin, with 1.5 log reduction of bacterial growth compared with negative control, although the peptide alone had no significant effect.…”

The synergy of berberine chloride and totarol against Staphylococcus aureus grown in planktonic and biofilm cultures

“…The chequerboard plates were inoculated with 10 6 c.f.u. ml 21 of S. aureus and incubated at 37 uC for 24 h. To evaluate the effect of the combination, the fractional inhibitory concentration (FIC) was calculated for each drug; then, the FIC index (FICI) was calculated as follows (Oo et al, 2010):…”

Lactoferrin as an Adjunctive Agent in the Treatment of Bacterial Infections Associated with Diabetic Foot Ulcers

“…Furthermore, synergistic activity of bovine lactoferricin (11 amino acids) with antibiotics was demonstrated against multiresistant clinical isolates of Staphylococcus aureus and Pseudomonas aeruginosa in vitro and in a model of corneal infection in mice. Lactoferricin also had an anti-inflammatory effect in cornea, suggesting that it leads to a decrease of cytokines and mediators involved in inflammation (Oo et al, 2010). Hence, lactoferrin as well as its derived peptides could be potential adjuncts to conventional antibiotics in combating these pathogens, which also infect diabetic foot ulcers.…”