Microbial keratitis: what's the preferred initial therapy? View 1: corneal scraping and combination antibiotic therapy is indicated

Managing Corneal Infections: Out with the old, in with the new?

There have been multiple reports of eye infections caused by antibiotic-resistant bacteria, with increasing evidence of ineffective treatment outcomes from existing therapies. With respect to corneal infections, the most commonly used antibiotics (fluoroquinolones, aminoglycosides, and cephalosporines) are demonstrating reduced efficacy against bacterial keratitis isolates. While traditional methods are losing efficacy, several novel technologies are under investigation, including light-based anti-infective technology with or without chemical substrates, phage therapy, and probiotics. Many of these methods show non-selective antimicrobial activity with potential development as broad-spectrum antimicrobial agents. Multiple preclinical studies and a limited number of clinical case studies have confirmed the efficacy of some of these novel methods. However, given the rapid evolution of corneal infections, their treatment requires rapid institution to limit the impact on vision and prevent complications such as scarring and corneal perforation. Given their rapid effects on microbial viability, light-based technologies seem particularly promising in this regard.

Microbial keratitis in a tertiary centre in Queensland, Australia (1999-2015)

Clinical relevance: Keratitis is common and studies of blindness throughout the world have found that corneal disease is the second most common cause of blindness.Background: Microbial keratitis a bacterial, fungal, or protozoan disease of the cornea, characterised by a corneal infiltrate with an overlying epithelial defect and associated anterior chamber reaction.Methods: Patients were identified through the hospital pathology database and a retrospective chart review of all patients with a positive corneal culture between 1999 and 2015 at Princess Alexandra Hospital was carried out.Results: There were 895 records from 779 patients included and additional 107 records excluded. The average age of the included patients was 58.9 years (SD 21.0). Males made up 498 (55.6%) of the included patients. Contact lens microbial keratitis (CLMK) was the most common risk factor for MK and was significantly more common in younger patients. CLMK was significantly associated with cultures positive for Pseudomonas aeruginosa (p < 0.001) while MK secondary to ocular surface disease and prior ocular surgery were more commonly associated with gram-positive organisms (p < 0.001). Monotherapy with a fluoroquinolone was the most common treatment for patients with MK. Good outcomes were seen in 57% of patients.Conclusion: In this patient group, contact lens wear was the most common risk factor for MK. Pseudomonas aeruginosa was the most common isolate.

A Novel Vitamin E TPGS-Based Formulation Enhances Chlorhexidine Bioavailability in Corneal Layers

Keratitis is a severe condition characterized by inflammation of the cornea following a local trauma. The most common ocular disease is the bacterial one, which requires an antibiotic treatment. The major limitation of this therapy is the resistance of the antibiotic. For this reason, alternative procedures have been developed and consist of antimicrobial molecules. One of the most used is the chlorhexidine gluconate, which has shown activity versus Gram-positive and Gram-negative bacteria and fungi. In addition to its efficiency, chlorhexidine shows low toxicity levels for mammalian cells and is a low-cost molecule. Despite its multiple benefits, chlorhexidine, if used at concentrations higher than 0.02% (w/w), can cause local eye irritation. Additionally, its poor penetrability through the cornea makes necessary frequent instillation of eye drops for a prolonged time. Due to these limitations, alternative drug delivery strategies are required. Here, we report a novel formulation based on the combination of d-alpha-tocopherol polyethylene glycol 1000 succinate with chlorhexidine, which results in higher accumulation of the drug in human corneas measured by liquid chromatography and strong antimicrobial activity. Moreover, this formulation does not cause any toxic effect on human cells and is well tolerated by rabbit eyes. Therefore this novel formulation represents a good candidate for the treatment of keratitis that overcomes the risk of antibiotic resistance.

Trends of Bacterial Keratitis Culture Isolates in Jerusalem; a 13- Years Analysis

PURPOSE

To describe the trends in pathogens and antibacterial resistance of corneal culture isolates in infectious keratitis during a period of 13 years at Hadassah-Hebrew University Medical Center.

METHODS

A Retrospective analysis of bacterial corneal isolates was performed during the months of January 2002 to December 2014 at Hadassah Hebrew University Medical Center. Demographics, microbiological data and antibiotic resistance and sensitivity were collected.

RESULTS

A total of 943 corneal isolates were analyzed during a 13 year period. A total of 415 positive bacterial cultures and 37 positive fungal cultures were recovered, representing 48% of the total cultures. The Annual incidence was 34.78 ± 6.54 cases. The most common isolate was coagulase-negative staphylococcus (32%), which had a significant decrease in trend throughout the study period (APC = -8.1, p = 0.002). Methicillin-resistant Staphylococcus aureus (MRSA) appears to have a decrease trend (APC = -31.2, P = 0.5). There was an increase in the resistance trend of coagulase-negative staphylococci to penicillin (APC = 5.0, P = <0.001). None of the pathogens had developed any resistance to Vancomycin. (P = 0.88).

CONCLUSIONS

Coagulase negative staphylococci were the predominant bacteria isolated from patients with keratitis. There was no significant change in the annual incidence of cases of bacterial keratitis seen over the past 13 years. Keratitis caused by MRSA appeared to decrease in contrast to the reported literature.

In vitro amoebicidal activities of Satureja cuneifolia and Melissa officinalis on Acanthamoeba castellanii cysts and trophozoites

Amoebic keratitis is difficult to treat without total efficacy in some patients because of cysts, which are less susceptible than trophozoites to the usual treatments. The aim of this study is to evaluate the in vitro amoebicidal activity of the methanolic extracts of Satureja cuneifolia and Melissa officinalis. In the presence of methanolic extracts (ranging from 1.0 to 32.0 mg/ml), numbers of the viable Acanthamoe castellanii trophozoites and cysts were decreased during the experimental process. Both extracts showed a time- and dose-dependent amoebicidal action on the trophozoites and cysts. Among the extracts tested, S. cuneifolia showed the strongest amoebicidal effect on the trophozoites and cysts. In the presence of 32 mg/ml extract, no viable trophozoites were observed within 24 h. At the same concentration value, the extract was found effective against the cysts at a rate of 46.3% within 72 h of the experimental process. At 16 mg/ml extract concentration, no viable trophozoites were also observed in the 24th hour of the experiment. At the end of the experimental process, 34.7% of the cysts were killed by the extract. M. officinalis showed moderate amoebicidal effect. At the concentration of 32 mg/ml, 44.3% and 30.0% of the trophozoites and cysts were killed by the extract, respectively. Results obtained from these concentration values were found statistically different in terms of their actions both on trophozoites and cysts (p<0.05).

Bacteriocin-like substance from Bacillus amyloliquefaciens shows remarkable inhibition of Acanthamoeba polyphaga

The effectiveness of a bacteriocin-like substance (BLS) produced by Bacillus amyloliquefaciens was tested against Acanthamoeba polyphaga strains, and its cytotoxic potential on Vero cells was investigated. Amebicidal activity of the purified BLS was tested by plate bioassays with concentrations ranging from 12.5 to 6,400 AU mL(-1). Damage to A. pholyphaga cells was monitored using an inverted microscope and counted in a Fuchs-Rosenthal chamber after 24, 48, and 72 h. According to the results obtained, the BLS showed remarkable amebicidal and amebostatic effect on A. polyphaga and showed no cytotoxicity on the Vero cells. These results may have great relevance in the development of new acanthamoebicidal compounds.

Initial therapy for suppurative microbial keratitis in Iraq

OBJECTIVE

To provide data-based guidelines for selection of an appropriate initial therapy for management suppurative microbial keratitis (SMK) in Iraq.

METHODS

This case-series study enrolled patients with clinical signs of suppurative keratitis suspected of being microbial, presented prospectively at Ibn Al-Haetham Teaching Eye Hospital from April 2002 to March 2005. Predisposing factors, microbial profile and sensitivities of isolated bacteria were determined. If direct microscopic examination of smears was negative for fungal elements, initial therapy started with ciprofloxacin 0.3% eye-drops. Subsequent treatment depends on clinical response and cultures' results.

RESULTS

Out of 396 cases enrolled, positive cultures were obtained in 232 cases (58.6%). The predominating agents isolated were Gram-positive cocci (Staphylococcus and Streptococcus) 75 cases (18.9%); Pseudomonas 68 cases (17.2%); and fungal species 74 cases (18.7%). Treatment was initiated with ciprofloxacin eye-drops in 364 cases, a favourable response was recorded in 185 cases (50.8%), addition of other antimicrobial drugs was required in 56 cases (15.4%), while failure of treatment was recorded in 123 cases (33.8%).

CONCLUSION

Use of ciprofloxacin eye drops alone as an initial therapy cannot cover most of the causative agents of SMK in Iraq. Addition of another drug can provide a better coverage for the predominating causative agents. The choice of this additional drug is based on the suspected infecting agent depending on the regional predisposing factors, and the clinical features.

Prescrire les collyres fortifiés

Fortified preparations of ophthalmic antibiotics are made with commercially available antibiotics (parenteral or lyophilized preparations). These fortified eyedrops have two main advantages: the increase in the antibiotic concentration in the corneal stroma and the wide choice of available antibiotics. Fortified ophthalmic solutions are used in severe keratitis (large diameter, stroma infiltration, inflammation of the anterior chamber, old patient). The following associations are recommended: ticarcillin+gentamicin+vancomycin or cephazolin+amikacin since they provide a broad-spectrum antibiotic activity against the wide range of bacteria that may cause keratitis. The main toxicity of these preparations is the retardation effect of the epithelial-healing rate (aminoglycosides, vancomycin) and the corneal and conjunctival toxic effects (aminoglycosides). However, fortified antibiotic drops remain the standard therapy for severe bacterial keratitis, given their corneal penetration and the possibility of the synergic and combined effect of an antibiotic association.

In vitro acanthamoebicidal activity of a killer monoclonal antibody and a synthetic peptide

OBJECTIVES

To evaluate the in vitro microbicidal activity against Acanthamoeba castellanii of a murine monoclonal anti-idiotypic antibody (KTmAb) and a synthetic killer mimotope (KP), which mimic a yeast killer toxin (KT) characterized by a wide spectrum of antimicrobial activity through interaction with specific cell wall receptors, mainly constituted by beta-glucans.

METHODS

Amoebicidal activity was investigated after incubation of trophozoites under different experimental conditions with laminarinase, KTmAb, KP and a scrambled decapeptide (SP). To confirm the specific interaction of KP with beta-glucans, the experiments were also carried out in the presence of laminarin (beta1-3-glucan) or pustulan (beta1-6-glucan); both glucan molecules were co-incubated with KP or SP.

RESULTS

KTmAb and KP exhibited a time-dependent killing activity, in comparison with SP or heat-inactivated KTmAb; this activity was completely abolished by pre-incubation with laminarin, but not by pustulan. Notably, in vitro amoebicidal activity was observed in the presence of laminarinase, an enzyme that specifically hydrolyses beta-glucans. Furthermore, KP specifically inhibited the growth of Acanthamoeba on infected contact lenses and the remaining adherent KP-treated trophozoites appeared strongly damaged.

CONCLUSIONS

The results indicate that the expression of beta1-3-glucan receptors in the cell membrane is probably modulated during cell growth of A. castellanii and is critical for the killing activity of KT-like molecules. Our data confirm the broad antimicrobial spectra of KTmAb and KP, emphasize the crucial role of beta1-3-glucan in microbial physiology and suggest the potential use of KTmAb and KP in the prevention and therapy of Acanthamoeba infections or in preventing Acanthamoeba contamination during storage of contact lenses.

Inflammatory stromal keratopathies: medical management of stromal keratomalacia, stromal abscesses, eosinophilic keratitis, and band keratopathy in the horse

This article discusses the diagnosis and medical treatment of stromal keratomalacia or "melting ulcers," stromal abscesses, eosinophilic keratitis (EK), and calcific band keratopathy. These are common and important inflammatory keratopathies of the equine corneal stroma. Keratomalacia and stromal abscesses are associated with infection, leukocytic invasion of the stroma, and loss of tissue and tear film proteinase homeostasis. Eosinophils infiltrate the stroma in response to unknown stimuli in EK. Calcium is deposited in the stroma and epithelium secondary to chronic equine recurrent uveitis in calcific band keratopathy. They are all associated with varying degrees of iridocyclitis.