Optimization, characterization and in vivo evaluation of mupirocin nanocrystals for topical administration.

Treatment of infectious skin conditions resulting from wounds and burns with topical antibiotics is challenging, particularly those caused by methicillin-resistant Staphylococcus aureus bacteria (MRSA). This is due to the formation of bacterial biofilms characterized by antimicrobial resistance. Mupirocin (MP), a widely used topical antibiotic, is active against gram-positive bacteria including MRSA. However, MP suffers from sub-optimal therapeutic efficacy due to its poor water-solubility and the significant rise in MP-resistant S. aureus. In this study, the physico-chemical characteristics of MP were modified through nanocrystallization to improve its therapeutic efficacy for the treatment of skin infections. Mupirocin-nanocrystals (MP-NC) were prepared using a nanoprecipitation technique and optimized using a D-optimal response surface design. The optimization of MP-NC produced ultra-small monodisperse spherical particles with a mean diameter of 70 nm and a polydispersity index of 0.2. The design resulted in two optimal MP-NC formulations that were evaluated by performing series of in vitro, ex vivo, microbiological, and in vivo studies. In-vitro results showed a 10-fold increase in the saturation solubility and a 9-fold increase in the dissolution rate of MP-NC. Ex vivo permeation studies, using pig ears skin, showed a 2-fold increase in the dermal deposition of MP-NC with the highest drug deposition occurring at 500-µm skin depth. Moreover, the optimal MP-NC formulations were lyophilized and incorporated into a 2% w/w cream. Microbiological studies revealed a 16-fold decrease in the minimum inhibitory concentration and the minimum bactericidal concentration of MP-NC. In vivo studies, using a rat excision burn wound model, demonstrated rapid and complete healing of infected burn wounds in rats treated with MP-NC cream in comparison to marketed Avoban ointment. Our results suggest that nanocrystallization of MP may provide an avenue through which higher levels of a topically applied MP can be permeated into the skin to reach relevant infectious areas and exert potential local antibacterial effects.

Bactericidal activity of a substituted thiazole against multidrug-resistant Eggerthia catenaformis isolated from patients with dental abscess.

Human infections caused by the anaerobic bacterium Eggerthia catenaformis are rare. However, a growing number of case reports have presented the bacterium as the causative agent in many serious complications. This study provides data on the isolation and antibiotic susceptibility profiles of E. catenaformis from dental abscess. Identification of isolates was performed using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). We also investigated the antibacterial activity of 5-acetyl-4-methyl-2-(3-pyridyl) thiazole (AMPT) on E. catenaformis isolates. Minimum inhibitory concentrations (MICs) were determined by an agar dilution method and bactericidal activity was evaluated by a time-kill assay. Moreover, the mechanism of action of AMPT was also explored by cell membrane disruption assay and scanning electron microscopy (SEM). MALDI-TOF MS results revealed unambiguous identification of all isolates with score values between 2.120 and 2.501. Isolates NY4 and NY9 (20% of isolates) were found resistant to multiple antibiotics judged by MIC values. As multidrug-resistant strains of E. catenaformis were not reported to date, we then confirmed the identity of NY4 and NY9 based on 16S rRNA gene sequence. Favorably, all isolates were susceptible to AMPT with an MIC range of 0.25-1 mg/L. Time-kill kinetics of AMPT indicated that it exhibited potent bactericidal activity against the multidrug-resistant isolates NY4 and NY9. Furthermore, this study also hypothesizes that AMPT exerts its antibacterial effect through damaging the cell membrane and thereby induce the release of intracellular components. AMPT could therefore be considered as a therapeutic option for infections caused by multidrug-resistant bacteria.

The Antimicrobial Activity of Ciprofloxacin-Loaded Niosomes against Ciprofloxacin-Resistant and Biofilm-Forming Staphylococcus aureus.

PURPOSE: The threat of Staphylococcus aureus antimicrobial resistance is increasing worldwide. Niosomes are a new drug delivery system that enhances the antimicrobial potential of antibiotics. We hereby aim to evaluate the antimicrobial and antibiofilm activity of ciprofloxacin-loaded niosomes. METHODS: The antimicrobial susceptibility of clinical S. aureus isolates (n=59) was determined by Kirby-Bauer disk diffusion method. Their biofilm formation activity was tested by Christensen's method. Two ciprofloxacin-loaded niosomal formulations were prepared by thin-film hydration method, and their minimum inhibitory concentrations (MIC) were determined by agar dilution method, against ciprofloxacin-resistant and biofilm-forming isolates (n=24). Their ability to inhibit biofilm formation and eradicate already formed biofilms was evaluated and further confirmed by scanning electron microscope images. Non-synonymous mutations, in a quinolone resistance-determining regions of S. aureus isolates, were detected by polymerase chain reaction. RESULTS: Most of the isolates were methicillin- (47/59) and ciprofloxacin-resistant (45/59). All except two isolates were capable of biofilm production. Niosomal preparation I reduced ciprofloxacin MIC by twofold in four isolates, whereas preparation II reduced ciprofloxacin MIC of most isolates by 8- to 32-fold, with three isolates that became ciprofloxacin-susceptible. Non-synonymous mutations were detected in isolates that maintained phenotypic ciprofloxacin resistance against ciprofloxacin-loaded niosomal preparation II. Ciprofloxacin-loaded niosomes reduced the minimum biofilm inhibitory concentration and the minimum biofilm eradication concentration in 58% and 62% of the tested isolates, respectively. CONCLUSION: Ciprofloxacin-loaded niosomes can restore ciprofloxacin activity against resistant S. aureus isolates. To our knowledge, this is the first report on the inhibition of biofilm formation and eradication of formed biofilms by ciprofloxacin-loaded niosomes.

Nanocrystals of Fusidic Acid for Dual Enhancement of Dermal Delivery and Antibacterial Activity: In Vitro, Ex Vivo and In Vivo Evaluation.

With the alarming rise in incidence of antibiotic-resistant bacteria and the scarcity of newly developed antibiotics, it is imperative that we design more effective formulations for already marketed antimicrobial agents. Fusidic acid (FA), one of the most widely used antibiotics in the topical treatment of several skin and eye infections, suffers from poor water-solubility, sub-optimal therapeutic efficacy, and a significant rise in FA-resistant Staphylococcus aureus (FRSA). In this work, the physico-chemical characteristics of FA were modified by nanocrystallization and lyophilization to improve its therapeutic efficacy through the dermal route. FA-nanocrystals (NC) were prepared using a modified nanoprecipitation technique and the influence of several formulation/process variables on the prepared FA-NC characteristics were optimized using full factorial statistical design. The optimized FA-NC formulation was evaluated before and after lyophilization by several in-vitro, ex-vivo, and microbiological tests. Furthermore, the lyophilized FA-NC formulation was incorporated into a cream product and its topical antibacterial efficacy was assessed in vivo using a rat excision wound infection model. Surface morphology of optimized FA-NC showed spherical particles with a mean particle size of 115 nm, span value of 1.6 and zeta potential of -11.6 mV. Differential scanning calorimetry and powder X-ray diffractometry confirmed the crystallinity of FA following nanocrystallization and lyophilization. In-vitro results showed a 10-fold increase in the saturation solubility of FA-NC while ex-vivo skin permeation studies showed a 2-fold increase in FA dermal deposition from FA-NC compared to coarse FA. Microbiological studies revealed a 4-fofd decrease in the MIC against S. aureus and S. epidermidis from FA-NC cream compared to commercial Fucidin cream. In-vivo results showed that FA-NC cream improved FA distribution and enhanced bacterial exposure in the infected wound, resulting in increased therapeutic efficacy when compared to coarse FA marketed as Fucidin cream.

Efficient wound healing composite hydrogel using Egyptian Avena sativa L. polysaccharide containing ß-glucan.

The purpose of this study was to develop an efficient wound healing PVA-biopolymer composite hydrogel using the polysaccharide derived from Egyptian Avena sativa L. The prepared polysaccharide showed high ß-glucan content which accelerates wound healing. The ß-glucan content was 13.28% and GC analysis revealed that glucose was the major sugar component (71.19%). Different PVA-polysaccharide hydrogels combined with different polymers and loaded with 0.3% bacitracin zinc were developed using the freezing-thawing method. The used polymers were; polyvinylpyrrolidone (PVP), Carbopol 940 (CP), hydroxyethylcellulose (HEC), hydroxypropyl methylcellulose (HPMC), and sodium carboxymethylcellulose (Na CMC). The prepared hydrogels were characterized by determination of gel fraction, swelling ratio, mechanical and bioadhesive properties. The results revealed that hydrogels prepared using anionic (NaCMC and CP) and more hydrophilic (HEC) polymers showed better swelling ratio, bioadhesive and mechanical characters compared with hydrogels prepared using cationic (PVP) or less hydrophilic (HPMC) polymers. For two selected formulations containing HEC (F7) and NaCMC (F9), disk diffusion method and In vitro microbial penetration were performed for microbiological assessment. In addition, In vivo evaluation of the anti-inflammatory and wound healing activity compared with conventional products were performed on rats. The results showed higher anti-inflammatory activity of F7 (21.4% edema reduction) compared with F9 (19.8% edema reduction). Similarly, F7 showed better healing (99% relative wound size reduction) than F9 (75%). The current study revealed the potential of using the prepared Egyptian Avena sativa L. polysaccharide and HEC for development of an efficient wound healing dressing with antimicrobial and anti-inflammatory activities.