Optimizing Bothropstoxin-I-Derived Peptides: Exploring the Antibacterial Potential of p-BthW.

Antimicrobial peptides are an emerging class of antibiotics that present a series of advantageous characteristics such as wide structural variety, broad spectrum of activity, and low propensity to select for resistance. They are found in all classes of life as defense molecules. A group of peptides derived from the protein Bothropstoxin-I has been previously studied as an alternative treatment against multi-drug-resistant bacteria. The peptide p-BthTX-I (sequence: KKYRYHLKPFCKK) and its homodimer, linked by disulfide oxidation through the residues of Cys11 and the serum degradation product [sequence: (KKYRYHLKPFC)2], were evaluated and showed similar antimicrobial activity. In this study, we synthesized an analogue of p-BthTX-I that uses the strategy of Fmoc-Lys(Fmoc)-OH in the C-terminal region for dimerization and tryptophan for all aromatic amino acids to provide better membrane interactions. This analogue, named p-BthW, displayed potent antibacterial activity at lower concentrations and maintained the same hemolytic levels as the original molecule. Our assessment revealed that p-BthW has a quick in vitro bactericidal action and prolonged post-antibiotic effect, comparable to the action of polymyxin B. The mode of action of p-BthW seems to rely not only on membrane depolarization but also on necrosis-like effects, especially in Gram-negative bacteria. Overall, the remarkable results regarding the propensity to develop resistance reaffirmed the great potential of the developed molecule.

Identification of the Infection Source of an Outbreak of Mycobacterium Chelonae Keratitis After Laser in Situ Keratomileusis.

PURPOSE: Nontuberculous mycobacteria keratitis is a rare but challenging complication of laser in situ keratomileusis (LASIK). This study was conducted to determine the source(s) of infection in a cluster of cases of keratitis after LASIK and to describe this outbreak and patients' outcomes. METHODS: In this retrospective, case series, single-center study, 86 patients were included who underwent LASIK or photorefractive keratectomy between December 2011 and February 2012. Corneal scrapes from the affected eyes, samples of tap and distilled water, water from the reservoir of the distilling equipment, steamer, and autoclave cassette; antiseptic and anesthetic solutions and surgical instrument imprints were cultivated in liquid and on solid media. Gram-negative bacteria and yeasts were identified using automated systems and mycobacteria by polymerase chain reaction-restriction enzyme analysis of the hsp65 gene (PRA-hsp65) and DNA sequencing. Mycobacterial isolates were typed by pulsed-field gel electrophoresis. The cases and outcomes are described. The main outcome measure was identification of the source(s) of the mycobacterial infections. RESULTS: Eight (15 eyes) of 86 patients (172 eyes) who underwent LASIK developed infections postoperatively; no patients who underwent photorefractive keratectomy developed infections. Mycobacterium chelonae was isolated from 4 eyes. The distilled water collected in the surgical facility contained the same M. chelonae strain isolated from the patients' eyes. Different gram-negative bacteria and yeasts were isolated from samples collected at the clinic but not from the patients' eyes. CONCLUSIONS: Tap water distilled locally in surgical facilities may be a source of infection after ocular surgery and its use should be avoided.

Analysis of Intraocular Lens Biofilms and Fluids After Long-Term Uncomplicated Cataract Surgery.

PURPOSE: Postoperative endophthalmitis is a potentially sight-threatening complication of cataract surgery. However, the pathophysiological mechanisms are not completely understood. We sought to study and evaluate the intraocular environment (aqueous and vitreous humors), the capsular tissue, and the intraocular lens (IOL) surfaces of normal eyes after long-term uncomplicated cataract surgery. DESIGN: Experimental laboratory investigation. METHODS: We studied 69 eyes donated for transplantation that had previously undergone cataract surgery with posterior chamber IOL implantation and that had no recorded clinical history of postoperative inflammation. We assessed the intraocular environment (DNA traces and biofilm formation) by microbiological evaluation of intraocular fluids using conventional microbiology and molecular techniques, including assessment for the presence of microbes (biofilm formation) on the IOL surface by scanning electron microscopy and ultrastructural capsular remnants by transmission electron microscopy. RESULTS: Isolated or aggregated cocci were probable in 18.8% of IOL optic surfaces (n = 13) studied by scanning electron microscopy, suggesting the presence of bacterial biofilm. In 3 intraocular fluid samples for IOLs with biofilm, we identified 16S rDNA by polymerase chain reaction and sequencing. No microbial contamination was found in intraocular fluids by conventional microbiological methods. CONCLUSIONS: Our data suggest the possibility of bacterial biofilm formation on the optic surface of IOLs in normal eyes after long-term uncomplicated cataract surgery even in the absence of clinical or subclinical symptoms.

Safety and efficacy of moxifloxacin-dexamethasone eyedrops as treatment for bacterial ocular infection associated with bacterial blepharitis.

INTRODUCTION: Treatments that offer two medications in a fixed combination have the potential to offer efficacious and safe treatment with advantages such as a regimen that is simpler than administering two separate solutions. This study evaluated the safety and efficacy of fixed-combination versus concomitant moxifloxacin 0.5% and dexamethasone 0.1% ocular solutions for the treatment of bacterial ocular inflammation and infection. METHODS: The clinical study design was a randomized, double-masked, active-controlled, parallel-group trial of 102 subjects with bacterial blepharitis in which two patients also had bacterial conjunctivitis. All subjects received two bottles of study medication: either a fixed combination of moxifloxacin 0.5%/dexamethasone 0.1% ophthalmic solution and placebo eye drops (fixed-dose group), or moxifloxacin 0.5% ophthalmic solution and dexamethasone 0.1% (concomitant group). One drop of each study medication was instilled bilaterally four times per day for 7 days. Clinical resolution, signs, symptoms, and safety were assessed. Microbiological specimens were collected from the eyelid margin and conjunctivae of each eye from each patient at the time of enrollment and at the exit visit. RESULTS: Clinical resolution occurred similarly in both groups (81.6% of eyes, fixed-dose group; 82.3% of eyes, concomitant group). Moreover, the microbiological efficacy of the treatment was also similar for both the fixed-dose group (84%) and the concomitant group (83%). Ocular symptoms and signs improved over time, with no significant differences between groups after 7 days of treatment, except the fixed-dose group had significantly more eyes with clinical resolution in eyelid erythema (100%, n = 98/98, fixed-dose group; 92.7%, n = 89/96, concomitant group; P = 0.0194) and eyelid scaling/crusting (98%, n = 96/98, fixed-dose group; 89.6%; n = 86/96 eyes, concomitant group; P = 0.0337). Both regimens were safe and well tolerated. CONCLUSION: The fixed-dose combination of moxifloxacin, 0.5% and dexamethasone, 0.1% was therapeutically equivalent and as well tolerated as the concomitant dosage.