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.

The ocular surface bacterial contamination and its management in the prophylaxis of post cataract surgery endophthalmitis

Objective: To investigate the recent pieces of evidence regarding the bacterial ocular surface contamination and its treatment in the prophylaxis of post-cataract surgery endophthalmitis. Methods: We conducted a literature research on the topic of interest and selected the most relevant data. Results: The studies reported a relatively high rate of positive conjunctival culture and the most frequently isolated organism was Coagulase negative Staphylococcus, which is also the most common etiological agent of the postoperative endophthalmitis. The bacterial ocular surface load is influenced by age, climate, associated diseases, topical and systemic medication. The use of povidone-iodine alone or in association with levofloxacin eyedrops as prophylactic method is effective in reducing the conjunctival bacterial contamination and consequently decreases the incidence of postoperative endophthalmitis. Conclusions: Based on the current pieces of evidence, adequate treatment of the bacterial ocular surface contamination prior to cataract surgery seems to be effective in preventing endophthalmitis after cataract surgery. Abbreviations: EU = European Union, Spp. = Species, HIV = Human Immunodeficiency Virus.

Incidence and Determinants of Endophthalmitis within 6 Months of Surgeries over a 2-Year Period at King Khaled Eye Specialist Hospital, Saudi Arabia: A Review

BACKGROUND

We present the incidence and determinants of endophthalmitis between July 2010 and June 2012 at King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia. On its basis, we recommended recommendations to strengthen the infection prevention and control strategies.

METHODS

This is a retrospective review of health records type of study. The details of cases reported having endophthalmitis among those operated in 2 years of study period were studied. The incidence of endophthalmitis was calculated for different eye surgeries and epidemiological variables. The causative organisms in vitreous tap were reviewed. The visual outcomes 6 weeks following intervention/treatment of endophthalmmitis were also studied.

RESULTS

Of the 22,554 cases operated, 17 developed endophthalmitis. The incidence was 0.08% (95% confidence interval [CI] 0.04-0.11). The incidence of endophthlamitis among cataract surgeries was 0.12% (95% CI 0.04-0.21). Five specimens did not show any bacteria or fungus. Staphylococcus epidermis (3 cases) was the main pathogen identified. In 8 (47%) eyes, vision deteriorated in spite of treatment. In 5 (29%) eyes, it became stable and in 4 (23.5%) eyes, it improved following treatment. Signs of infection were noted in 1(st) week, 3 weeks and 12 weeks in 4, 6 and 5 eyes respectively. Late presentation of infection (6 months postoperatively) was reported in two eyes.

CONCLUSIONS

A vigilant infection control unit in a large eye hospital helps in monitoring endophthalmitis related catastrophes and suggests timely preventive measures to reduce the occurrence and appropriate measures to limit visual disabilities following eye surgery related endophthalmitis.

Antibiotic prevention of postcataract endophthalmitis: a systematic review and meta-analysis

Endophthalmitis is one of the most feared complications after cataract surgery. The aim of this systematic review was to evaluate the effect of intracameral and topical antibiotics on the prevention of endophthalmitis after cataract surgery. A systematic literature review in the MEDLINE, CINAHL, Cochrane Library and EMBASE databases revealed one randomized trial and 17 observational studies concerning the prophylactic effect of intracameral antibiotic administration on the rate of endophthalmitis after cataract surgery. The effect of topical antibiotics on endophthalmitis rate was reported by one randomized trial and one observational study. The quality and design of the included studies were analysed using the Cochrane risk of bias tool. The quality of the evidence was evaluated using the GRADE approach. We found high-to-moderate quality evidence for a marked reduction in the risk of endophthalmitis with the use of intracameral antibiotic administration of cefazolin, cefuroxime and moxifloxacin, whereas no effect was found with the use of topical antibiotics or intracameral vancomycin. Endophthalmitis occurred on average in one of 2855 surgeries when intracameral antibiotics were used compared to one of 485 surgeries when intracameral antibiotics were not used. The relative risk (95% CI) of endophthalmitis was reduced to 0.12 (0.08; 0.18) when intracameral antibiotics were used. The difference was highly significant (p < 0.00001). Intracameral antibiotic therapy is the best choice for preventing endophthalmitis after cataract surgery. We did not find evidence to conclude that topical antibiotic therapy prevents endophthalmitis.

Perioperative prophylaxis for endophthalmitis after cataract surgery in iran

Purpose:

To describe prophylactic patterns employed against endophthalmitis after cataract surgery in Iran.

Methods:

This cross-sectional study included 486 ophthalmologists filling in a self-administered questionnaire during the 20^th Annual Congress of the Iranian Society of Ophthalmology in December 2010, Tehran, working in both private and academic medical centers. Prophylactic measures used preoperatively, intraoperatively and postoperatively and self-reported rates of endophthalmitis were assessed as the main outcome measurements.

Results:

In the preoperative phase, 75.5% of surgeons used povidone-iodine in the conjunctival sac and 71.4% of them did not use antibiotics. The rate of intraoperative prophylaxis was 61.9% either in the form of intracameral antibiotics or subconjunctival injection (mostly cephazolin or gentamicin). Only 7.8% of participants used intracameral cephalosporins. Postoperative antibiotics [mostly chloramphenicol (57%) and ciprofloxacin (28%)] were used by 94.2% of surgeons. On average, ten years of practice were required to observe one case of endophthalmitis.

Conclusion:

The surgeons in present setting used various prophylactic regimens against endophthalmitis after cataract surgery. Setting a local and evidence-based clinical practice guideline seems necessary.

Cataract surgery and methods of wound closure: a review

Clear corneal incisions are routinely used in cataract surgery, but watertight wound closure may not always be achieved, which can increase the risk for anterior chamber fluid egress or ocular surface fluid ingress. A new US Food and Drug Administration-approved ocular sealant appears to have good efficacy in sealing clear corneal incisions; its use may be indicated when wound integrity is in question.

Treatment Paradigm After Uncomplicated Cataract Surgery: A Prospective Evaluation

PURPOSE

To compare 3 clinical variables, namely, visual recovery, anterior chamber inflammation, and macular edema, between 2 different regimens after uncomplicated cataract surgery.

DESIGN

Prospective, randomized, single-blind study at a single center, private, teaching practice in Las Vegas, NV.

METHODS

Patients randomized to group I (nonsteroidal anti-inflammatory drugs, n = 113) received besifloxacin ophthalmic suspension 0.6% and bromfenac 0.09%, whereas those randomized to group II (steroid, n = 109) received besifloxacin ophthalmic suspension 0.6% and prednisolone acetate 1%.Preoperative evaluation included a baseline macular optical coherence tomography. Postoperative data collected included visual acuity, direct visual anterior segment cell and flare counts, and macular optical coherence tomographies. Foveal thickness and total macular volume were used to assess the presence of cystoid macular edema.

RESULTS

Visual recovery was statistically insignificant with P values at 0.7, 0.10, 0.2, and 0.7 at 1 day, 1 week, 1 month, and 2 months, respectively.The degree of anterior segment inflammation was not statistically significant (P = 0.8) between the studied populations.The foveal thickness (1 week, P = 0.8; 1 month, P = 0.2; 2 months, P = 0.2) and total macular volume (1 week, P = 0.7; 1 month, P = 0.1; 2 months, P = 0.2) were not statistically significant between the groups, and the observed power were 0.902 and 0.666, respectively.

CONCLUSIONS

This study demonstrated that bromfenac was equally efficacious when compared with a potent topical steroid in restoring visual function, decreasing and resolving anterior chamber inflammation, and preventing the development of macular edema.

Intravitreal injection of the chimeric phage endolysin Ply187 protects mice from Staphylococcus aureus endophthalmitis

The treatment of endophthalmitis is becoming very challenging due to the emergence of multidrug-resistant bacteria. Hence, the development of novel therapeutic alternatives for ocular use is essential. Here, we evaluated the therapeutic potential of Ply187AN-KSH3b, a chimeric phage endolysin derived from the Ply187 prophage, in a mouse model of Staphylococcus aureus endophthalmitis. Our data showed that the chimeric Ply187 endolysin exhibited strong antimicrobial activity against both methicillin-sensitive S. aureus and methicillin-resistant S. aureus (MRSA) strains, as evidenced by MIC determinations, reductions in turbidity, and disruption of biofilms. Moreover, exposure of S. aureus to Ply187 for up to 10 generations did not lead to resistance development. The intravitreal injection of chimeric Ply187 (at 6 or 12 h postinfection) significantly improved the outcome of endophthalmitis, preserved retinal structural integrity, and maintained visual function as assessed by electroretinogram analysis. Furthermore, phage lysin treatment significantly reduced the bacterial burden and the levels of inflammatory cytokines and neutrophil infiltration in the eyes. These results indicate that the intravitreal administration of a phage lytic enzyme attenuates the development of bacterial endophthalmitis in mice. To the best of our knowledge, this is the first study demonstrating the therapeutic use of phage-based antimicrobials in ocular infections.

Risk factors for acute endophthalmitis following cataract surgery: a systematic review and meta-analysis

Background

Acute endophthalmitis is one of the most serious complications of cataract surgery and often results in severe visual impairment. Several risk factors for acute postoperative endophthalmitis (POE) following cataract surgery have been reported but the level of evidence and strength of association is varied. The purpose of this study was to critically appraise published reports on and to summarize clinical risk factors associated with acute POE which could be easily assessed by ophthalmologists for the introduction and implementation of preventive measure.

Methods

A systematic review and meta-analysis of observational studies was performed. Six databases were searched with no limits on the year or language of publication. Study-specific odds ratios (Ors) or relative risk (RR) of each risk factor were pooled using a random effect model.

Results

A total of 6 686 169 participants with 8 963 endophthalmitis in 42 studies were analyzed. Of the nine risk factors identified in our systematic review and meta-analysis, extra- or intracapsular cataract extraction, a clear corneal incision, without intracameral cefazolin (1 mg in 0.1 ml solution), without intracameral cefuroxime (1 mg in 0.1 ml solution), post capsular rupture, silicone intraocular lenses and intraoperative complications were found strongly associated with acute endophthalmitis. Other significant factors with a lower strength of association (risk estimates generally 1.5 or less) were male gender and old age (85 years and older).

Conclusions

Our study provides summary data on the risk factors for acute POE. Identifying patients at high risk of this sight-threatening eye disease is important from both the public health and clinical perspectives as this would facilitate detection of disease before the onset of irreversible visual loss enabling earlier intervention.

Eyelid skin disinfecting and conjunctival bacteria in cataract surgery

PURPOSE

To evaluate the effect on conjunctival micro-organisms of chlorhexidine alcohol 0.5% eyelid wash in cataract patients.

METHODS

In this single-centre experimental study, 120 patients scheduled to undergo cataract operation were cultured in the conjunctiva before the operation and after the insertion of the intraocular lens. Bacterial samples for aerobic and anaerobic cultures were taken with a polyvinyl alcohol pad and transported in peptone water to the microbiological laboratory where they were analysed in a blinded fashion. Half of the patients received a standardized eyelid scrub with chlorhexidine alcohol 0.5%, while the rest did not. The conjunctiva of all patients was rinsed preoperatively with chlorhexidine solution 0.05%.

RESULTS

In all the between-group comparisons, the treated eyelid group had slightly lower bacterial counts than the control group on the postoperative samples, but differences were far from statistically significant. Within-group comparisons revealed statistically significant reduction in colonies and species between the preoperative and postoperative sampling.

CONCLUSION

In this experimental culture study, no evidence was found to suggest that preoperative eyelid chlorhexidine alcohol wash is effective in further reducing bacterial counts in the conjunctiva when the conjunctiva itself is rinsed preoperatively with chlorhexidine solution. The present results, however, do not contradict that the wash may be of some marginal help in reducing bacterial contamination of the operation field. Consequently, this part of the prophylactic protocol is still in practice in our institution.

Preventing surgical site infections

The risk of surgical site infection (SSI) is approximately 1-3% for elective clean surgery. Apart from patient endogenous factors, the role of external risk factors in the pathogenesis of SSI is well recognized. However, among the many measures to prevent SSI, only some are based on strong evidence, for example, adequate perioperative administration of prophylactic antibiotics, and there is insufficient evidence to show whether one method is superior to any other. This highlights the need for a multimodal approach involving active post-discharge surveillance, as well as measures at every step of the care process, ranging from the operating theater to postoperative care. Multicenter or supranational intervention programs based on evidence-based guidelines, 'bundles' or safety checklists are likely to be beneficial on a global scale. Although theoretically reducible to zero, the maximal realistic extent by which SSI can be decreased remains unknown.

Acute endophthalmitis after cataract surgery at a referral centre in Northern Taiwan: review of the causative organisms, antibiotic susceptibility, and clinical features

PURPOSES

The aims of this study were to describe the bacterial isolates and treatment outcomes of endophthalmitis after cataract surgery at a referral centre in Northern Taiwan.

METHODS

This was a retrospective, interventional, and observational series. Medical records were review of patients with clinical diagnosed, and/or culture-proven bacterial endophthalmitis at a tertiary referral centre in Northern Taiwan from January 2002 to December 2008. Treatment generally conformed to standard guidelines. Main outcome measurements were results of organism culture, antibiotic susceptibility of isolated bacteria, and visual acuity (VA) outcome.

RESULTS

Thirty-four patients had positive cultures. A total of 55.9% of the culture-positive isolates were Gram negative and 44.1% were Gram positive. Pseudomonas aeruginosa was the most commonly isolated organism. Eighteen patients had final VA better than 5/200, and 41 had final VA worse than 5/200. In multiple linear regression analysis, female gender, presence of hypopyon, and worse baseline VA were significant independent predictors of worse visual outcome.

CONCLUSIONS

It was found that at a referral centre in Northern Taiwan, the majority of bacterial isolates were Gram negative in acute postoperative bacterial endophthalmitis after cataract surgery and P. aeruginosa was the most common bacterial isolate.

Toll-like receptor 2 ligand-induced protection against bacterial endophthalmitis

BACKGROUND

Activation of innate immunity plays a key role in determining the outcome of an infection. Here, we investigated whether Toll-like receptors (TLRs) are involved in retinal innate response and explored the prophylactic use of TLR2 ligand in preventing bacterial endophthalmitis.

METHODS

C57BL/6 mice were given intravitreal injections of Pam3Cys, a synthetic ligand of TLR2, or vehicle (phosphate-buffered saline) 24 h prior to Staphylococcus aureus inoculation. The severity of endophthalmitis was graded by slit lamp, electroretinography, histological examinations, and determination of bacterial load in the retina. The expression of cytokines/chemokines and cathelicidin-related antimicrobial peptide was assessed by enzyme-linked immunosorbent assay and Western blot, respectively.

RESULTS

Intravitreal injections of Pam3Cys up-regulated TLR2 expression in the retina of C57BL/6 mice, and Pam3Cys pretreatment significantly improved the outcome of S. aureus endophthalmitis, preserved retinal structural integrity, and maintained visual function as assessed by electroretinography in C57BL/6 mice. Furthermore, Pam3Cys pretreatment activated retinal microglia cells, induced the expression of cathelicidin-related antimicrobial peptide, and remarkably reduced the bacterial load.

CONCLUSIONS

This is the first report that highlights the existence and role of TLR2 in retinal innate immune response to S. aureus infection and suggests that modulation of TLR activation provides a novel prophylactic approach to prevent bacterial endophthalmitis.

Acute postoperative endophthalmitis caused by Gemella morbillorum

PURPOSE

We present a case of Gemella morbillorum endophthalmitis after uneventful cataract surgery.

METHODS

A 78-year-old woman developed progressive blurring of vision, hypopyon, and vitritis in the precocious postoperatory following cataract surgery. Pars plana vitrectomy and intraocular lens explantation were performed followed by intravitreal injection of vancomycin and ceftazidime. Postoperatively, the patient was given hourly topical fortified vancomycin according to antimicrobial susceptibility testing. At the final follow-up visit 6 months after the initial procedure, visual acuity was 20/50 and no signs or symptoms of endophthalmitis were observed.

RESULTS

The undiluted vitreous samples and explanted lens were analyzed. Cultures revealed the growth of G morbillorum, an infrequent opportunistic pathogen.

CONCLUSIONS

To date, this is the second reported case of postoperative endophthalmitis by this species. Although endophthalmitis is rare, ophthalmologists should be alert to the possibility of patients having endophthalmitis caused by G morbillorum. Especially, it is necessary to be cautious with surgery in patients with recent infections. A review of the medical literature of this rare ocular infection is presented.

The conjunctival bacterial pattern of diabetics undergoing cataract surgery

PURPOSE

To ascertain the conjunctival bacterial pattern of diabetics undergoing cataract operation to reduce the risk of postoperative endophthalmitis (PE).

METHODS

An observational retrospective study of the conjunctival bacteria of consecutive patients undergoing cataract surgery from July 2005 to November 2008. Records of patients having eye surgical prophylaxis in the 6 months before the culture and those patients having cataract operation combined with other surgical procedures were excluded. Aerobic and microaerobic cultures were carried out. Dade-Behring panels were used for bacterial identification. The database containing the isolated bacteria was linked to another Access database containing demographic and clinical data such as diabetes presence and baseline blood glucose and creatinine levels. The conjunctival bacteria of diabetics were compared with those of the non-diabetics. Epidat 3.1 program was used for statistical calculations.

RESULTS

From 5922 selected patients, 1325 (22.37%) knew they were diabetics (higher prevalence than expected). Among self-reported non-diabetics, 900 (15.2%) could be 'unknown' diabetics; another 274 had an impaired renal function; and 3423 non-diabetics joined the control group. Diabetics have a significantly higher prevalence of Staphylococcus aureus, Enterococci, certain Streptococci, and Klebsiella sp. than non-diabetics. Diabetics and non-diabetics having a blood creatinine level above 105.2 mumol/l had an increased conjunctival bacterial prevalence; these groups had a higher mean age and men predominated.

CONCLUSIONS

Diabetics have a conjunctival flora pattern whose increased bacteria are a predominant cause of many diabetic infections. An abnormally high blood creatinine level is an indicator of increased conjunctival colonisation in diabetics and non-diabetics.