Actinomyces israelii endogenous endophthalmitis

Molecular Diagnostics for Ocular Infectious Diseases: LXXVIII Edward Jackson Memorial Lecture

PURPOSE

To review the use of molecular diagnostic techniques in the management of ocular infectious disease.

DESIGN

Retrospective review.

METHODS

A combination of literature review and personal recollections are used.

RESULTS

Although the broad term molecular diagnostics may encompass techniques to identify pathogens via protein or metabolomic signatures, this review concentrates on detection of pathogen nucleic acid as an indicator of infection. The introduction of the polymerase chain reaction (PCR) in 1985 opened a new era in analysis of nucleic acids. This technique was soon applied to the detection of potential pathogen DNA and RNA, including viruses, bacteria, and parasites in infectious eye disease. Advances in PCR have allowed class-specific diagnostics (ie, pan-bacterial and pan-fungal), quantitation of pathogen DNA, and multiplexed testing. The Human Genome Project in the early 2000s greatly accelerated development of DNA sequencers, ushering in the era of "Next Generation Sequencing" and permitting pathogen-agnostic methods for the detection of potential infectious agents. Most recently, new technologies such as nanopore sequencing have reduced both cost and equipment requirements for whole-genome sequencing; when coupled with real-time sequence analysis methods, these methods offer the promise of true, real-time, point-of-service ocular infectious disease diagnostics.

CONCLUSIONS

Molecular methods for pathogen detection have greatly advanced the diagnosis of ocular infectious disease. Further methodologic advances will have a direct impact on the management of these conditions.

Actinomyces and related organisms in human infections

Actinomyces israelii has long been recognized as a causative agent of actinomycosis. During the past 3 decades, a large number of novel Actinomyces species have been described. Their detection and identification in clinical microbiology laboratories and recognition as pathogens in clinical settings can be challenging. With the introduction of advanced molecular methods, knowledge about their clinical relevance is gradually increasing, and the spectrum of diseases associated with Actinomyces and Actinomyces-like organisms is widening accordingly; for example, Actinomyces meyeri, Actinomyces neuii, and Actinomyces turicensis as well as Actinotignum (formerly Actinobaculum) schaalii are emerging as important causes of specific infections at various body sites. In the present review, we have gathered this information to provide a comprehensive and microbiologically consistent overview of the significance of Actinomyces and some closely related taxa in human infections.

Systematic review of 342 cases of endogenous bacterial endophthalmitis

We review a total of 342 cases of endogenous bacterial endophthalmitis reported between 1986 and 2012. Predisposing conditions were present in 60%, most commonly diabetes, intravenous drug use, and malignancy. The most common sources of infection were liver, lung, endocardium, urinary tract, and meninges. Systemic features such as fever were present in 74%, hypopyon in 35%, and an absent fundal view in 40%. Diagnostic delay occurred in 26%. Blood cultures were positive in 56%, and at least one intraocular sample was positive in 58% (comprising 26% anterior chamber samples, 59% vitreous taps, and 41% vitrectomy specimens). Worldwide, Gram negative infections (55%) were more frequent than Gram positive (45%) infections, particularly in Asia. Over the last decade, 11% of eyes were treated with systemic antibiotics alone, 10% intravitreal antibiotics alone, 36% systemic plus intravitreal antibiotics, and 20% systemic plus intravitreal antibiotics plus pars plana vitrectomy. The most commonly used intravitreal antibiotics were vancomycin (for Gram positive infection) and ceftazidime (Gram negative). The median final visual acuity was 20/100, with 44% worse than 20/200. Among all cases, 24% required evisceration or enucleation, and mortality was 4%. Both intravitreal dexamethasone and vitrectomy were each associated with a significantly greater chance of retaining 20/200 or better and significantly fewer eviscerations or enucleations-these warrant further study. For most patients, treatment should include a thorough systemic evaluation and prompt intravitreal and systemic antibiotics.

Role of molecular diagnostics in ocular microbiology

Although microbial culture remains the gold standard for diagnosis of many ocular infections, the technique is limited by low yield, inability to detect certain organisms, and potentially long delays to results. DNA-based molecular diagnostic techniques use detection of specific nucleic acid sequences as evidence for presence of suspected pathogens. The polymerase chain reaction (PCR) is a powerful molecular biology technique that allows for detection of fewer than 10 copies of pathogen genome. Recent technical advances in PCR have permitted quantitation of pathogen load using quantitative PCR (qPCR), and have permitted multiplexing of primer sets. Use of pan-bacterial and pan-fungal primers for ribosomal DNA sequences has allowed diagnosis of bacterial and fungal infections using molecular techniques. In this review, we highlight recent advances in the application of PCR to the diagnosis of anterior segment and posterior segment ocular infectious diseases.

Actinomyces endogenous endophthalmitis in a cat following multiple dental extractions

An 8-year-old, brachycephalic, mixed breed cat underwent full mouth tooth extractions for the treatment of tooth root abscessation. Subsequently, the cat developed anterior uveitis refractory to topical therapy that eventually necessitated enucleation. Actinomyces species were isolated from both the tooth root abscesses and the anterior chamber after enucleation. Histopathology of the enucleated eye revealed panophthalmitis with abundant intralesional bacteria morphologically consistent with Actinomyces. Between the time of tooth root extraction and enucleation (20 weeks), the cat was diagnosed with hyperthyroidism and treated with oral steroids for inflammatory bowel syndrome. We believe this report represents a rare case of endogenous endophthalmitis secondary to dental disease, possibly precipitated by concurrent immunosuppression.

Endogenous endophthalmitis with an unusual infective agent: Actinomyces neuii

PURPOSE

To report an unusual case of a patient with endogenous endophthalmitis caused by Actinomyces neuii.

METHODS AND RESULTS

A 69-year-old woman in an immunosuppressed state and who had a previous history of periappendicular abscess presented with bilateral red painful eyes. The diagnosis was confirmed by culture and pan-bacterial polymerase chain reaction drawn from anterior chamber sample. On admission, the patient underwent an intravitreal injection of vancomycin combined with ceftazidime. Following a 3-week treatment of intravenous penicillin and topical sulfacetamide sodium, the patient recovered fully.

CONCLUSIONS

Actinomyces neuii can cause endogenous endophthalmitis. Intravenous penicillin G is an effective treatment leading to favorable prognosis.

The microbiology of endophthalmitis: global trends and a local perspective

Endophthalmitis is a rare but frequently devastating infection, caused by diverse organisms, including bacteria, viruses, fungi, and parasites. The causative agents of endophthalmitis vary according to the mechanism. The involvement of intraocular structures can result from exogenous spread from ocular trauma, infection of adjacent structures, or as a complication of intraocular surgery. Of the causes of exogenous endophthalmitis, post-operative endophthalmitis is the most frequently encountered; specifically, cataract surgery is the most frequent eye surgery and, thus, leads the list of surgery-associated endophthalmitis. Exogenous source is far more common than endogenous endophthalmitis, a disease that is caused by the hematogenous spread of organisms from a remote infectious site to the eye, leading to severe visual loss. Several large series estimate that endogenous endophthalmitis accounts for 2-15 % of all cases of endophthalmitis. Progressive vitritis is a hallmark for all forms of endophthalmitis, accompanied by intraocular inflammation, loss of vision, pain, and hypopyon. The common presentation consists of reduced vision, conjunctival injection, pain, and eyelid swelling. We reviewed the microbiology of endophthalmitis during a 9-year period in Winnipeg, Canada. Gram-positive bacteria with coagulase-negative staphylococci are the most common causative organisms, reflecting the association with surgical procedures.