Clinical characteristics of external bacterial ocular and periocular infections and their antimicrobial treatment patterns among a Ghanaian ophthalmic population.

Empirical antimicrobial therapy is linked to a surge in antimicrobial resistant infections. However, an insight on the bacteria etiology of ocular infections is essential in the appropriation of choice of antimicrobial among clinicians, yet there remains a dearth of data from Ghana. We investigated the bacteria etiology of external ocular and periocular infections and antimicrobial treatment patterns among a Ghanaian ophthalmic population. A multicenter study design with purposive sampling approach was employed. Patients demographics and clinical data were collated using a pretested structure questionnaire. Cornea specimens and conjunctival swabs were obtained for bacterial isolation following standard protocols. About 95% (98/103) of ocular samples were positive for bacteria culture. The proportion of Gram-negative bacteria was 58.2%, and the predominant bacteria species were Pseudomonas aeruginosa 38.8% and Staphylococcus aureus 27.6%. Conjunctivitis 40.0% and keratitis 75.0% were mostly caused by Pseudomonas aeruginosa. The routinely administered antimicrobial therapy were polymyxin B 41.2%, neomycin 35.1% and ciprofloxacin 31.6%. Participants demographic and clinical characteristics were unrelated with positive bacteria culture (p > 0.05). Our results showed a markedly high burden of ocular bacterial infections and variations in etiology. Bacterial infection-control and antimicrobial agent management programs should be urgently institutionalized to prevent the emergence of resistant infections.

Cationic Polyelectrolyte Nanocapsules of Moxifloxacin for Microbial Keratitis Therapy: Development, Characterization, and Pharmacodynamic Study.

Microbial keratitis (MK) is a vision-threatening disease and the fourth leading cause of blindness worldwide. In this work, we aim to develop moxifloxacin (MXN)-loaded chitosan-based cationic mucoadhesive polyelectrolyte nanocapsules (PENs) for the effective treatment of MK. PENs were formulated by polyelectrolyte complex coacervation method and characterized for their particle size, surface charge, morphology, mucoadhesive property, in-vitro and ex-vivo release, ocular tolerance, and antimicrobial efficacy studies. The pharmacodynamic study was conducted on rabbit eye model of induced keratitis and it is compared with marketed formulation (MF). Developed PENs showed the size range from 230.7 ± 0.64 to 249.0 ± 0.49 nm and positive surface charge, spherical shape along with appropriate physico-chemical parameters. Both in-vitro and ex-vivo examination concludes that PENs having more efficiency in sustained release of MXN compared to MF. Ocular irritation studies demonstrated that no corneal damage or ocular irritation. The in-vivo study proved that the anti-bacterial efficacy of PENs was improved when compared with MF. These results suggested that PENs are a feasible choice for MK therapy because of their ability to enhance ocular retention of loaded MXN through interaction with the corneal surface of the mucous membrane.

Preparation and Evaluation of a Xanthan Gum-Containing Linezolid Ophthalmic Solution for Topical Treatment of Experimental Bacterial Keratitis.

PURPOSE: To formulate a xanthan gum-containing linezolid ophthalmic solution (LZD-XG) as a new antibiotic treatment against ocular bacterial infection. METHODS: LZD-XG was prepared and evaluated for its in vitro/in vivo ocular tolerance, in vitro/in vivo antibacterial activity, and in vivo ocular penetration. RESULTS: The optimized LZD-XG exhibited good in vitro/in vivo eye tolerance. A prolonged ocular surface residence time of LZD-XG was observed after topical instillation, and the ocular permeation was significantly better for LZD-XG than fora linezolid (LZD) ophthalmic solution. The in vitro antimicrobial activity was significantly better with LZD-XG than with LZD. In vivo evaluation also confirmed a strong therapeutic treatment effect of LZD-XG, as it significantly improved the clinical symptoms, ameliorated the damage of Staphylococcus aureus to ocular tissues, lowered the colony forming unit counts in the cornea, and decreased the myeloperoxidase activity in the cornea. CONCLUSION: LZD-XG was deemed a viable ophthalmic solution against ocular bacterial infection due to its excellent in vitro and in vivo characterizations.

12-year analysis of incidence, microbiological profiles and in vitro antimicrobial susceptibility of infectious keratitis: the Nottingham Infectious Keratitis Study.

BACKGROUND/AIMS: To examine the incidence, causative microorganisms and in vitro antimicrobial susceptibility and resistance profiles of infectious keratitis (IK) in Nottingham, UK. METHODS: A retrospective study of all patients who were diagnosed with IK and underwent corneal scraping between July 2007 and October 2019 (a 12-year period) at a UK tertiary referral centre. Relevant data, including demographic factors, microbiological profiles and in vitro antibiotic susceptibility of IK, were analysed. RESULTS: The estimated incidence of IK was 34.7 per 100 000 people/year. Of the 1333 corneal scrapes, 502 (37.7%) were culture-positive and 572 causative microorganisms were identified. Sixty (4.5%) cases were of polymicrobial origin (caused by ≥2 different microorganisms). Gram-positive bacteria (308, 53.8%) were most commonly isolated, followed by Gram-negative bacteria (223, 39.0%), acanthamoeba (24, 4.2%) and fungi (17, 3.0%). Pseudomonas aeruginosa (135, 23.6%) was the single most common organism isolated. There was a significant increase in Moraxella spp (p<0.001) and significant decrease in Klebsiella spp (p=0.004) over time. The in vitro susceptibilities of Gram-positive and Gram-negative bacteria to cephalosporin, fluoroquinolone and aminoglycoside were 100.0% and 81.3%, 91.9% and 98.1%, and 95.2% and 98.3%, respectively. An increase in resistance against penicillin was observed in Gram-positive (from 3.5% to 12.7%; p=0.005) and Gram-negative bacteria (from 52.6% to 65.4%; p=0.22). CONCLUSION: IK represents a relatively common and persistent burden in the UK and the reported incidence is likely underestimated. Current broad-spectrum antimicrobial treatment provides a good coverage for IK, although challenged by some level of antimicrobial resistance and polymicrobial infection.

Monocaprin eye drop formulation to combat antibiotic resistant gonococcal blindness.

Neisseria gonorrhoeae bacteria are acknowledged as an urgent threat to human health because this species has developed resistances to all of the antibiotics used clinically to treat its infections. N. gonorrhoeae causes the sexually transmitted disease gonorrhoea, but also causes blindness when the bacteria infect the eyes. Infants are particularly susceptible, acquiring the infection from their mothers at birth. We have shown that the monoglyceride monocaprin rapidly kills N. gonorrhoeae and other bacterial species and is non-irritating in ocular assays. Here we show that the physical and chemical properties of monocaprin make it ideal for use in a thickened eye drop formulation to combat eye infections. Monocaprin-containing formulations were assessed using analytical techniques and for antimicrobial activity in vitro and in ex vivo infections. Monocaprin-containing formulations retained activity after three years and are non-irritating, unlike preparations of povidone iodine in our assays. A recommended formulation for further development and investigation is 0.25% monocaprin in 1% HPMC with 1% polysorbate 20.

Epidemiology of Microbial Keratitis in Uganda: A Cohort Study.

Purpose: To describe the epidemiology of Microbial Keratitis (MK) in Uganda.Methods: We prospectively recruited patients presenting with MK at two main eye units in Southern Uganda between December 2016 and March 2018. We collected information on clinical history and presentation, microbiology and 3-month outcomes. Poor vision was defined as vision < 6/60).Results: 313 individuals were enrolled. Median age was 47 years (range 18-96) and 174 (56%) were male. Median presentation time was 17 days from onset (IQR 8-32). Trauma was reported by 29% and use of Traditional Eye Medicine by 60%. Majority presented with severe infections (median infiltrate size 5.2 mm); 47% were blind in the affected eye (vision < 3/60). Microbiology was available from 270 cases: 62% were fungal, 7% mixed (bacterial and fungal), 7% bacterial and 24% no organism detected. At 3 months, 30% of the participants were blind in the affected eye, while 9% had lost their eye from the infection. Delayed presentation (overall p = .007) and prior use of Traditional Eye Medicine (aOR 1.58 [95% CI 1.04-2.42], p = .033) were responsible for poor presentation. Predictors of poor vision at 3 months were: baseline vision (aOR 2.98 [95%CI 2.12-4.19], p < .0001), infiltrate size (aOR 1.19 [95%CI 1.03-1.36], p < .020) and perforation at presentation (aOR 9.93 [95% CI 3.70-26.6], p < .0001).Conclusion: The most important outcome predictor was the state of the eye at presentation, facilitated by prior use of Traditional Eye Medicine and delayed presentation. In order to improve outcomes, we need effective early interventions.

A Novel, Broad-Spectrum Antimicrobial Combination for the Treatment of Pseudomonas aeruginosa Corneal Infections.

Bacterial keratitis causes significant blindness, yet antimicrobial resistance has rendered current treatments ineffective. Polymyxin B-trimethoprim (PT) plus rifampin has potent in vitro activity against Staphylococcus aureus and Pseudomonas aeruginosa, two important causes of keratitis. Here we further characterize this combination against P. aeruginosa in a murine keratitis model. PT plus rifampin performed comparably to or better than moxifloxacin, the gold standard, suggesting that the combination may be a promising therapy for bacterial keratitis.

Protective Action of Linear Polyethylenimine against Staphylococcus aureus Colonization and Exaggerated Inflammation in Vitro and in Vivo.

Increased evolution of multidrug resistant pathogens necessitates the development of multifunctional antimicrobials. There is a perceived need for developing new antimicrobials that can interfere with acute inflammation after bacterial infections. Here, we investigated the therapeutic potential of linear polyethylenimine (LPEI) in vitro and in vivo. The minimum inhibitory concentration of LPEI ranged from 8 to 32 µg/mL and elicited rapid bactericidal activity against clinical isolates of meticillin-resistant Staphylococcus aureus (MRSA). The polymer was biocompatible for human cultured ocular and dermal cells. Prophylactic addition of LPEI inhibited the bacterial colonization of human primary dermal fibroblasts (hDFs). In a scratch wound cell migration assay, LPEI attenuated the migration inhibitory effects of bacterial secretions. The polymer neutralized the cytokine release by hDFs exposed to bacterial secretions, possibly by blocking their accessibility to host cell receptors. Topical instillation of LPEI (1 mg/mL) was noncytotoxic and did not affect the re-epithelialization of injured porcine cornea. In a prophylactic in vivo model of S. aureus keratitis, LPEI was superior to gatifloxacin in terms of reducing stimulation of cytokines, corneal edema, and overall severity of the infection. These observations demonstrate therapeutic potential of LPEI for antimicrobial prophylaxis.

Evaluation of corneal cross-linking as adjuvant therapy for the management of fungal keratitis.

PURPOSE: To evaluate the efficacy of corneal cross-linking (CXL) as adjuvant therapy for the treatment of fungal ulcerative keratitis. METHODS: Forty-one patients with fungal ulcerative keratitis were recruited and assigned into two randomized controlled groups. These groups were treated with CXL combined with antifungal medications (CXL-M) or antifungal medications alone (M). The ulcers were assessed by slit-lamp biomicroscopy, slit-lamp images, in vivo confocal microscopy (IVCM), and anterior segment optical coherence tomography (AS-OCT). The patients were followed up before surgery/first visit (FV), 1 day after surgery, 1 and 2 weeks, and 1, 2, 3, 4, 5, and 6 months after surgery/FV. RESULTS: In the cured patients, the area of corneal ulcers, the duration of ulcer healing, the time to non-observed fungal hyphae by IVCM, the number of antifungal medications, the frequency of administered medications, and the maximum ulcer depth decreased significantly after CXL (all P < 0.05) compared with the M group. There were no significant differences in either corneal thickness or epithelial thickness of ulcers after healing between 5 and 6 months after surgery in the CXL-M group, while these were increased significantly at 6 months compared with 5 months after FV in the M group (both P < 0.05). CONCLUSIONS: In our study, CXL accelerated healing of the fungal ulcers, shortened the treatment duration, and minimized the need for medications and surgery. It appears that CXL is an effective procedure and adjuvant therapy for managing fungal keratitis.

Effect of Optisol Supplementation With 0.255 µg/mL Amphotericin B on Elimination of Yeast at 5°C.

PURPOSE: Fungal infections in lamellar keratoplasty are a growing concern. Optisol-GS does not contain an antifungal agent and supplementation with 0.255 µg/mL Amphotericin B (AmpB) has been considered. This study tested the ability of 0.255 µg/mL AmpB in Optisol-GS to eliminate yeast contamination of corneal tissue. METHODS: Three isolates of Candida albicans, 1 of Candida parapsilosis, and 1 of Candida glabrata were tested in Optisol with and without AmpB. Corneoscleral rims stored at -80°C were thawed and placed in 10 multiwell plates (4 per plate). The rims were inoculated with 4 respective loads of yeast: 0, 10, 10, and 10 colony-forming units in 2 sets of 5 for 5 yeasts. One set was filled with Optisol plus AmpB and the other with Optisol only. All 10 plates were incubated at cold storage (2°C-8°C) for 48 hours. After 48 hours, all corneal rims were placed into 10 mL of yeast extract peptone dextrose medium; a swab culture of each well was plated onto Sabouraud plates; and all plates with the remaining Optisol were incubated at 30°C. Yeast growth was monitored for 10 days. Minimum inhibitory concentration and minimum fungicidal concentration were determined. RESULTS: All corneoscleral specimens were positive regardless of fungal load or presence of AmpB. All controls remained negative. Minimum inhibitory concentrations and minimum fungicidal concentrations were equivalent and ranged between 0.5 and 2.0 µg/mL. CONCLUSIONS: AmpB at a concentration of 0.255 µg/mL in Optisol-GS at cold storage (2°C-8°C) over 48 hours did not eliminate yeast from corneal tissue.

Fungal Keratitis: Epidemiology, Rapid Detection, and Antifungal Susceptibilities of Fusarium and Aspergillus Isolates from Corneal Scrapings.

Fungal aetiology of keratitis/corneal ulcer is considered to be one of the leading causes of ocular morbidity, particularly in developing countries including India. More importantly, Fusarium and Aspergillus are reported commonly implicating corneal ulcer and against this background the present work was undertaken so as to understand the current epidemiological trend of the two fungal keratitis. During the project period, a total of 500 corneal scrapings were collected from suspected mycotic keratitis patients, of which 411 (82.2%) were culture positive for bacteria, fungi, and parasites. Among fungal aetiologies, Fusarium (216, 52.5% of 411) and Aspergillus (68, 16.5% of 411) were predominantly determined. While the study revealed a male preponderance with both the fungal keratitis , it further brought out that polyene compounds (natamycin and amphotericin B) and azoles were active, respectively, against Fusarium spp. and Aspergillus spp. Additionally, 94.1% of culture proven Fusarium keratitis and, respectively, 100% and 63.6% of A. flavus and A. fumigatus were confirmed by multiplex PCR. The sensitivity of the PCR employed in the present study was noted to be 10 fg/µl, 1 pg/µl, and 300 pg/µl of DNA, respectively, for Fusarium, A. flavus, and A. fumigatus. Alarming fact was that Fusarium and Aspergillus regionally remained to be the common cause of mycotic keratitis and the Fusarium isolates had a higher antifungal resistance than Aspergillus strains against most of the test drugs.

Development of a Broad-Spectrum Antimicrobial Combination for the Treatment of Staphylococcus aureus and Pseudomonas aeruginosa Corneal Infections.

Staphylococcus aureus and Pseudomonas aeruginosa are two of the most common causes of bacterial keratitis and corresponding corneal blindness. Accordingly, such infections are predominantly treated with broad-spectrum fluoroquinolones, such as moxifloxacin. Yet, the rising fluoroquinolone resistance has necessitated the development of alternative therapeutic options. Herein, we describe the development of a polymyxin B-trimethoprim (PT) ophthalmic formulation containing the antibiotic rifampin, which exhibits synergistic antimicrobial activity toward a panel of contemporary ocular clinical S. aureus and P. aeruginosa isolates, low spontaneous resistance frequency, and in vitro bactericidal kinetics and antibiofilm activities equaling or exceeding the antimicrobial properties of moxifloxacin. The PT plus rifampin combination also demonstrated increased efficacy in comparison to those of either commercial PT or moxifloxacin in a murine keratitis model of infection, resulting in bacterial clearance of 70% in the animals treated. These results suggest that the combination of PT and rifampin may represent a novel antimicrobial agent in the treatment of bacterial keratitis.

Types of organisms and in-vitro susceptibility of bacterial isolates from patients with microbial keratitis: A trend analysis of 8 years.

PURPOSE: To report the distribution and trends of types of organisms and antibiotic susceptibility of the bacterial isolates obtained from patients with microbial keratitis. METHODS: Microbiology records of culture-positive microbial keratitis that underwent a diagnostic corneal scraping and cultures were reviewed. Fungal, bacterial, and parasitic culture results and antibiotic susceptibility profile of bacteria were analyzed and comparisons were made between two halves of the study period (2007-2010 vs. 2011-2014). RESULTS: A total of 3981 corneal scrapings were processed during the 8-year study period. Pathogen was recovered in culture in 1914 (48.1%) samples. Fungi, bacteria, and parasites constituted 38.7%, 60%, and 1.3% of the total isolates, respectively. The common fungal isolates were Aspergillus spp. (224/868, 25.8%) and Fusarium spp. (200/868, 23.0%), while common Gram-positive bacteria were Streptococcus pneumoniae (217/1125, 19.3%) and Staphylococcus aureus (185/1125, 16.4%), and common Gram-negative bacteria was Pseudomonas spp. (99/219, 45.2%). There was no significant difference in proportion of bacterial (P = 0.225) and fungal (P = 0.421) keratitis between the first half and second half of the study period. There was a significant increase in proportion of Gram-positive isolates (P = 0.015) [353/758 (46.6%) vs. 772/1482 (52.1%)] and decrease in proportion of Gram-negative organisms (P = 0.044) [88/758 (11.6%) vs. 131/1482 (8.8%)] in the recent years. In-vitro antibiotic susceptibility testing showed decrease in susceptibility to moxifloxacin for Pseudomonas spp. (P = 0.016) in recent years. CONCLUSION: Prevalence of fungal and bacterial keratitis has remained unchanged over the years. This study shows a significant increase in Gram-positive bacterial infection and decrease in Gram-negative bacterial infection of the cornea in the recent years.

Clinical pattern and antibiotic sensitivity of bacterial corneal ulcers in Kano, Northern Nigeria.

Purpose: The purpose of this study is to determine predisposing factors, common bacterial causes, and antibiotic sensitivity of corneal ulcers in Murtala Muhammad Specialist Hospital. Materials and Methods: A prospective, cross-sectional, observational study was carried out on patients with corneal ulcers. Information on relevant clinical, sociodemographic profile was obtained. Examination includes visual acuity test and slit-lamp biomicroscopy, especially fluorescein staining. Corneal scrapings from the ulcer were inoculated onto the selected solid culture media plates. Gram staining for microscopic examination was done. Antibiotic sensitivity test on different antibiograms was done using modified Kirby-Bauer technique, determining bacterial isolate sensitivity or resistance to relevant antibiotics (chloramphenicol, ciprofloxacin, ofloxacin, gentamicin, tetracycline, ceftazidime, ceftriaxone, cefotaxime, and penicillin). Results: A total of 77 patients with corneal ulcer were examined. Ocular trauma, application of harmful traditional eye medication, and use of unspecified topical medication before presentation were among the predisposing factors. Bacterial growth was seen in 46.8% of the samples, of which 28.6% of the growth were Gram-positive. The common bacteria isolated were Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pneumoniae, Proteus species, and Klebsiella pneumoniae. Isolates were sensitive to ciprofloxacin and ofloxacin while an intermediate sensitivity was seen with chloramphenicol and gentamicin. Isolates were resistant to tetracycline, ceftazidime, ceftriaxone, cefotaxime, and penicillin. Conclusion: Ocular trauma was the major predisposing factor to corneal ulcer, and Staphylococcus species was the major bacterial organism isolated. Isolates were found to be sensitive to ciprofloxacin and ofloxacin, while an intermediate sensitivity was seen with chloramphenicol and gentamicin.

RésuméBut: Le but de cette étude est de déterminer les facteurs de prédisposition, les causes bactériennes courantes, et la sensibilité aux antibiotiques des ulcères de la cornée à l'hôpital Murtala Mohammed Specialist. Matériels et méthodes: une étude prospective, transversales, l'étude d'observation a été effectuée sur des patients atteints d'ulcères de la cornée. Des informations sur les caractéristiques sociodémographiques, cliniques a été obtenue profi l. Examen comprend test d'acuité visuelle et lampe à fente biomicroscopie, surtout fl uorescein la coloration. À partir de l'ulcère cornéen raclures ont été inoculées sur la plaque de culture solide. La coloration de Gram pour l'examen microscopique a été fait. Essai sur la sensibilité aux antibiotiques a été effectuée à l'aide d antibiograms différentes modifi Ed Kirby-Bauer technique, déterminer la sensibilité ou la résistance d'isoler des bactéries aux antibiotiques correspondants (chloramphénicol, oxacin oxacin ciprofl, ofl, la gentamicine, la tétracycline, la ceftazidime, la ceftriaxone, céfotaxime, et la pénicilline). Résultats: Un total de 77 patients atteints d' ulcère cornéen ont été examinés. Un traumatisme oculaire, l'application de médicament traditionnel des nuisibles, et l'utilisation d'unspecifi ed médicament topique avant la présentation ont été parmi les facteurs de prédisposition. La croissance bactérienne a été observée dans 46,8 % des échantillons, dont 28,6 % de la croissance des bactéries Gram-positives ont été. Les bactéries communes isolées étaient Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pneumoniae, espèces de Proteus et Klebsiella pneumoniae. Les isolats étaient sensibles à l'oxacin oxacin ciprofl et ofl tandis qu'une sensibilité intermédiaire a été vu par le chloramphénicol et la gentamicine. Isolats étaient résistants à la tétracycline, la ceftazidime, la ceftriaxone, céfotaxime, et la pénicilline. Conclusion: un traumatisme oculaire a été le principal facteur prédisposant à l'ulcère cornéen, et Staphylococcus espèce a été le principal organisme bactérien isolé. Les isolats ont été trouvés à être sensibles à l'oxacin oxacin ciprofl et ofl, tandis qu'une sensibilité intermédiaire a été vu par le chloramphénicol et la gentamicine.

Effect of Mucoadhesive Polymeric Formulation on Corneal Permeation of Fluoroquinolones.

PURPOSE: The aim of the study was to develop a novel formulation of levofloxacin and besifloxacin to achieve improved mucoadhesion and permeability of besifloxacin and levofloxacin through cornea for the effective treatment of ocular infections. METHODS: A multicomponent hydrogel formulation containing chitosan-polyvinyl alcohol (PVA)-poly(N-vinylpyrrolidone) (PVP) was designed. Lysophosphatidylcholine was used to enhance corneal penetration of the drugs. The hydrogel preparations were characterized for various parameters, including clarity, pH, viscosity, in vitro release kinetics, mucoadhesion, ex vivo human corneal permeation, and antimicrobial efficacy. The formulations were compared with standard drug solution and marketed eye drops (Besix® and Levotop®). RESULTS: Compared to commercial ophthalmic preparations and free drug solutions, hydrogel formulation of both besifloxacin and levofloxacin was found to have 3.5- and 8-fold higher (P < 0.001) mucoadhesion and superior cumulative corneal permeation. The formulations showed superior in vitro anti-infective properties. Incubation of besifloxacin and levofloxacin formulations with Staphylococcus aureus-infected cornea model for 0.5 h showed greater potency of the hydrogel formulations compared to the marketed eye drops and standard solutions. CONCLUSIONS: The results of the study show the multicomponent hydrogel formulations of besifloxacin and levofloxacin to have superior corneal permeation with the potential for being used as topical ophthalmic preparations.

Designed Host Defense Peptides for the Treatment of Bacterial Keratitis.

Purpose: To limit corneal damage and potential loss of vision, bacterial keratitis must be treated aggressively. Innovation in antimicrobials is required due to the need for empirical treatment and the rapid emergence of bacterial resistance. Designed host defense peptides (dHDPs) are synthetic analogues of naturally occurring HDPs, which provide defense against invading pathogens. This study investigates the use of novel dHDPs for the treatment of bacterial keratitis. Methods: The minimum inhibitory concentrations (MICs) were determined for dHDPs on both Gram-positive and -negative bacteria. The minimum biofilm eradication concentrations (MBEC) and in vitro time-kill assays were determined. The most active dHDP, RP444, was evaluated for propensity to induce drug resistance and therapeutic benefit in a murine Pseudomonas aeruginosa keratitis model. Results: Designed HDPs were bactericidal with MICs ranging from 2 to >64 µg/mL and MBEC ranging from 6 to 750 µg/mL. In time-kill assays, dHDPs were able to rapidly reduce bacterial counts upon contact with as little as 2 µg/mL. RP444 did not induce resistance after repeated exposure of P. aeruginosa to subinhibitory concentrations. RP444 demonstrated significant efficacy in a murine model of bacterial keratitis as evidenced by a significant dose-dependent decrease in ocular clinical scores, a significantly reduced bacterial load, and substantially decreased inflammatory cell infiltrates. Conclusions: Innovative dHDPs demonstrated potent antimicrobial activity, possess a limited potential for development of resistance, and reduced the severity of murine P. aeruginosa keratitis. These studies demonstrate that a novel dHDP may have potential to treat patients with sight-threatening bacterial keratitis.

Symmetrically Substituted Xanthone Amphiphiles Combat Gram-Positive Bacterial Resistance with Enhanced Membrane Selectivity.

This is the first report of the design of a new series of symmetric xanthone derivatives that mimic antimicrobial peptides using a total synthesis approach. This novel design is advantageous because of its low cost, synthetic simplicity and versatility, and easy tuning of amphiphilicity by controlling the incorporated cationic and hydrophobic moieties. Two water-soluble optimized compounds, 6 and 18, showed potent activities against Gram-positive bacteria, including MRSA and VRE (MICs = 0.78-6.25 µg/mL) with a rapid bactericidal effect, low toxicity, and no emergence of drug resistance. Both compounds demonstrated enhanced membrane selectivity that was higher than those of most membrane-active antimicrobials in clinical trials or previous reports. The compounds appear to kill bacteria by disrupting their membranes. Significantly, 6 was effective in vivo using a mouse model of corneal infection. These results provide compelling evidence that these compounds have therapeutic potential as novel antimicrobials for multidrug-resistant Gram-positive infections.

Antimicrobial Blue Light Therapy for Infectious Keratitis: Ex Vivo and In Vivo Studies.

Purpose: To investigate the effectiveness of antimicrobial blue light (aBL) as an alternative or adjunctive therapeutic for infectious keratitis. Methods: We developed an ex vivo rabbit model and an in vivo mouse model of infectious keratitis. A bioluminescent strain of Pseudomonas aeruginosa was used as the causative pathogen, allowing noninvasive monitoring of the extent of infection in real time via bioluminescence imaging. Quantitation of bacterial luminescence was correlated to colony-forming units (CFU). Using the ex vivo and in vivo models, the effectiveness of aBL (415 nm) for the treatment of keratitis was evaluated as a function of radiant exposure when aBL was delivered at 6 or 24 hours after bacterial inoculation. The aBL exposures calculated to reach the retina were compared to the American National Standards Institute standards to estimate aBL retinal safety. Results: Pseudomonas aeruginosa keratitis fully developed in both the ex vivo and in vivo models at 24 hours post inoculation. Bacterial luminescence in the infected corneas correlated linearly to CFU (R2 = 0.921). Bacterial burden in the infected corneas was rapidly and significantly reduced (>2-log10) both ex vivo and in vivo after a single exposure of aBL. Recurrence of infection was observed in the aBL-treated mice at 24 hours after aBL exposure. The aBL toxicity to the retina is largely dependent on the aBL transmission of the cornea. Conclusions: Antimicrobial blue light is a potential alternative or adjunctive therapeutic for infectious keratitis. Further studies of corneal and retinal safety using large animal models, in which the ocular anatomies are similar to that of humans, are warranted.

Cationic lipid emulsions as potential bioadhesive carriers for ophthalmic delivery of palmatine.

Palmatine (PM) is a potent anti-infective agent used to treat eye diseases. However, PM is less effective for ocular application due to short residence time within the eyes. This study aimed to develop a cationic lipid emulsions (CLEs) for ophthalmic delivery of PM and evaluate its suitability in infection treatment. PM-loaded CLEs (PM-CLEs) were prepared through emulsifying/high-pressure homogenisation and characterised by particle size, ζ potential and morphology. The resulting PM-CLEs possessed a particle size of 192 nm and ζ potential of 45 mV around. In vitro release illustrated that PM was released less from CLEs. Corneal bioadhesion test showed that PM-CLEs exhibited an enhanced ocular residence time. Improved anti-infective activity was achieved in the model of fungus-induced keratitis. Furthermore, PM-CLEs demonstrated predominant cellular uptake and internalisation in the corneal epithelial cells. These results provide proof of concept that CLEs are promising bioadhesive carriers for ophthalmic delivery of PM.

Histidine biosynthesis plays a crucial role in metal homeostasis and virulence of Aspergillus fumigatus.

Aspergillus fumigatus is the most prevalent airborne fungal pathogen causing invasive fungal infections in immunosuppressed individuals. The histidine biosynthetic pathway is found in bacteria, archaebacteria, lower eukaryotes, and plants, but is absent in mammals. Here we demonstrate that deletion of the gene encoding imidazoleglycerol-phosphate dehydratase (HisB) in A. fumigatus causes (i) histidine auxotrophy, (ii) decreased resistance to both starvation and excess of various heavy metals, including iron, copper and zinc, which play a pivotal role in antimicrobial host defense, (iii) attenuation of pathogenicity in 4 virulence models: murine pulmonary infection, murine systemic infection, murine corneal infection, and wax moth larvae. In agreement with the in vivo importance of histidine biosynthesis, the HisB inhibitor 3-amino-1,2,4-triazole reduced the virulence of the A. fumigatus wild type and histidine supplementation partially rescued virulence of the histidine-auxotrophic mutant in the wax moth model. Taken together, this study reveals limited histidine availability in diverse A. fumigatus host niches, a crucial role for histidine in metal homeostasis, and the histidine biosynthetic pathway as being an attractive target for development of novel antifungal therapy approaches.