PHYSICOCHEMICAL PROPERTIES AND ANTIBACTERIAL ACTIVITY OF THE PRECIPITATE OF VANCOMYCIN AND CEFTAZIDIME: Implications in the Management of Endophthalmitis

Consensus and controversies in the science of endophthalmitis management: Basic research and clinical perspectives

Infectious endophthalmitis is a severe intraocular infection caused by bacteria, or less commonly by fungi. It can occur after penetrating eye procedures, trauma, or the spread of infection from contiguous structures or via emboli from distant organs. Because of the time-critical nature of the treatment, endophthalmitis is treated with the clinical diagnosis and modified by the microbiological report of the intraocular contents. The current strategy for managing endophthalmitis relies on pre-clinical literature, case series, and one large multi-center randomized clinical trial on post-cataract surgery endophthalmitis. Culture-susceptibility of the microorganisms from undiluted vitreous guides the definitive treatment in non-responsive cases. Strategies to reduce the incidence of endophthalmitis after penetrating eye procedures have been developed concurrently with refined means of treatment. Despite these advances, outcomes remain poor for many patients. Although consensus articles have been published on managing endophthalmitis, treatment patterns vary, and controversies remain. These include (1) the use of newer methods for early and precise microbiological diagnosis; (2) the choice of intravitreal antibiotics; (3) the need for systemic therapy; (4) early and complete vitrectomy. Here, we review the current consensus and address controversies in diagnosing and managing endophthalmitis. This review is intended to familiarize physicians and ophthalmologists with different aspects of endophthalmitis management to make informed decisions.

Cyclodextrins Allow the Combination of Incompatible Vancomycin and Ceftazidime into an Ophthalmic Formulation for the Treatment of Bacterial Keratitis

Ceftazidime (CZ) and vancomycin (VA) are two antibiotics used to treat bacterial keratitis. Due to their physical incompatibility (formation of a precipitate), it is not currently possible to associate both molecules in a single container for ophthalmic administration. We firstly characterized the incompatibility then investigated if 2-hydroxypropyl-beta (HPβCD) and 2-hydroxypropyl-gamma cyclodextrins (HPγCD) could prevent this incompatibility. The impact of pH on the precipitation phenomena was investigated by analysing the supernatant solution of the mixture using high performance liquid chromatography. A characterization of the inclusion of CZ with HPγCD using ¹H nuclear magnetic resonance (NMR), and VA with HPβCD using ¹H-NMR and a solubility diagram was performed. A design of experiment was built to determine the optimal conditions to obtain a formulation that had the lowest turbidity and particle count. Our results showed that VA and CZ form an equimolar precipitate below pH 7.3. The best formulation obtained underwent an in-vitro evaluation of its antibacterial activity. The impact of HPCDs on incompatibility has been demonstrated through the inclusion of antibiotics and especially VA. The formulation has been shown to be able to inhibit the incompatibility for pH higher than 7.3 and to possess unaltered antibacterial activity.

Physical Incompatibility between Vancomycin and Viscoelastic Mimicking Acute Endophthalmitis: The First Report

This is the first documentation of vancomycin precipitation with viscoelastic in the anterior chamber of the eye. A 34-year-old white male underwent uneventful penetrating keratoplasty. Intracameral instillation of 1 mg/0.1 mL of vancomycin followed no attempts of meticulous viscoelastic irrigation. Six hours later thick white material in the anterior chamber was sedimented. The following criteria excluded the diagnosis of endophthalmitis and TASS: clear and transparent anterior chamber and vitreous body, the absence of ciliary injection and corneal oedema, and unremarkable laboratory tests' results. This iatrogenic complication mimicking endophthalmitis does not require any specific management and should be acknowledged in guidelines for prevention and treatment of endophthalmitis. The objective of this paper is to alert colleagues to this iatrogenic complication of vancomycin mimicking endophthalmitis. Whether this condition should be labelled as positive or negative demands further investigation. As vancomycin is a time-dependent antibiotic, it is possible that this precipitate could serve as a slowly releasing drug depot and viscoelastic as a vehicle for precipitation. This being the case, investigation is needed to analyse its potential to precipitate with another dispersive and cohesive viscoelasticity.

Risk Factors for Culture-Positive Endophthalmitis after Repair of Open Globe Injuries

Purpose

To identify risk factors for the development of culture-positive endophthalmitis after repair of open globe injuries.

Methods

We retrospectively reviewed the medical records of 629 consecutive patients with open globe injuries admitted to King Abdulaziz University Hospital between May 1996 and January 2008.

Results

Endophthalmitis developed in 12 (1.9%) patients. The following factors were significantly associated with endophthalmitis by univariate analysis: delayed presentation (>24 hours) (p=0.008), rural address (p=0.013), and dirty wound (p=0.012). Logistic regression analysis identified dirty wound to be associated with the development of endophthalmitis (odds ratio = 11.6; 95% confidence interval [CI] = 2.67–50.6). On logistic regression analysis, presence of retained intraocular foreign body (IOFB) in association with rural address (odds ratio = 11.0; 95% CI = 1.44–83.3) or dirty wound (odds ratio = 9.2; 95% CI = 1.22–69.1) was associated with development of endophthalmitis. Endophthalmitis was a significant negative predictor for final good visual outcome (p=0.00261) and was significantly associated with hypotony (p=0.033).

Conclusions

Delayed presentation, rural address, and dirty wound were associated with development of endophthalmitis. Retained IOFB in association with rural address or dirty wound was associated with a particularly high risk of endophthalmitis.

Prevention of Evisceration or Enucleation in Endogenous Bacterial Panophthalmitis with No Light Perception and Scleral Abscess

Panophthalmitis is the most extensive ocular involvement in endophthalmitis with inflammation in periocular tissues. Severe inflammation of the anterior and posterior segments is frequently accompanied by corneal opacity, scleral abscess, and perforation or rupture. Enucleation or evisceration was the only remaining viable treatment option when all options to salvage the eye had been exhausted. The purpose of this retrospective study is to examine the outcomes of patients with endogenous bacterial panophthalmitis, no light perception and scleral abscess who were treated with multiple intravitreal and periocular injections of antibiotics and dexamethasone. Evaluation included spreading of infection to contiguous or remote sites, following evisceration or enucleation, and sympathetic ophthalmia. Eighteen patients were diagnosed with EBP, with liver abscesses in eight patients, retroperitoneal infection in four, pneumonia in two, infective endocarditis in one, cellulitis in one, drug abuse in one, and mycotic pseudoaneurysm in one. Culture results were positive for Klebsiella pneumoniae in 12 patients, Streptococcus spp. in three, Pseudomonas aeruginosa in one, Escherichia coli in one, and Staphylococcus aureus in one. The average number of periocular injections was 2.2, and the average number of intravitreal injections was 5.8. No eye required evisceration or enucleation and developed the spreading of infection to contiguous or remote sites during the follow-up. No sympathetic ophthalmia was observed in the fellow eye of all patients. Prevention of evisceration or enucleation in patients with EBP, NLP and scleral abscess can be achieved by multiple intravitreal and periocular injections of antibiotics and dexamethasone.

Pharmacokinetics of intravitreal antibiotics in endophthalmitis

Intravitreal antibiotics are the mainstay of treatment in the management of infectious endophthalmitis. Basic knowledge of the commonly used intravitreal antibiotics, which includes their pharmacokinetics, half-life, duration of action and clearance, is essential for elimination of intraocular infection without any iatrogenic adverse effect to the ocular tissue. Various drugs have been studied over the past century to achieve this goal. We performed a comprehensive review of the antibiotics which have been used for intravitreal route and the pharmacokinetic factors influencing the drug delivery and safety profile of these antibiotics. Using online resources like PubMed and Google Scholar, articles were reviewed. The articles were confined to the English language only. We present a broad overview of pharmacokinetic concepts fundamental for use of intravitreal antibiotics in endophthalmitis along with a tabulated compendium of the intravitreal antibiotics using available literature. Recent advances for increasing bioavailability of antibiotics to the posterior segment with the development of controlled drug delivery devices are also described.

Acute Postoperative Endophthalmitis Following Cataract Surgery: A Review

Endophthalmitis following cataract surgery is rare but continues to be a serious complication following cataract surgery. Over the years, the incidence of endophthalmitis has declined because of various preoperative and perioperative measures. They include use of antiseptic and appropriate surgical draping techniques. In this review, we have focused on the incidence, existing risk factors, various clinical features, management strategies, and prophylaxis pertaining to postoperative endophthalmitis following cataract surgery. Outcomes and pitfalls of 2 landmark studies, namely, the Endophthalmitis Vitrectomy Study and the European Society of Cataract and Refractive Surgeons Endophthalmitis Study, are briefly mentioned.Infectious endophthalmitis following cataract surgery is a dreaded complication. Preoperative identification of risk factors and effective prophylaxis could help in reducing its incidence. Early diagnosis followed by management of these patients either with vitreous tap or vitrectomy coupled with intravitreal antibiotics holds the key.

Interaction of intravitreal combination drugs and the effect on the targeted site

BACKGROUND

After evaluating experimentally the diffusion processes in the retina using peroxidase as a tracer material (previously published work), we found that junctional complexes of the retinal pigment epithelium and retinal capillaries were the major impediment to free diffusion between the retina and choroidal-retinal blood vessels. These experiments indicated that to achieve high therapeutic concentrations of medications inside the eye, it was necessary to administer them by intravitreal injection. Soon after initial experimental work the necessity of combining antibiotics or antibiotics with steroids became obvious. As the use of intravitreal injection grew over the last 2 decades, so did the concept of combination therapy.

METHODS

This review describes potential causes of drug-drug interaction and the rationale for combination therapy when injected into the vitreous cavity, encompassing publications between 1971 and 2008.

RESULTS

We describe the conditions that can cause physical-chemical interactions between the medications and the need for combination therapy for treatment of various intraocular disease processes.

CONCLUSIONS

The intravitreal injection of medication and their combinations has become a part of standard care for many diseases of the retina and choroid. This article reviews the potential interaction of nontoxic doses of medications when injected simultaneously in the vitreous cavity, and disease processes that are now treated with these combination therapies.