Streptococcus pneumoniae endophthalmitis: a study of 36 cases with special reference to antibiotic resistance and treatment options

Ocular streptococcal infections: A clinical and microbiological review

Streptococcus is a diverse bacterial genus that is part of the ocular surface microbiome implicated in conjunctivitis, keratitis, endophthalmitis, dacryocystitis, and orbital cellulitis which can lead to decreased visual acuity and require surgical intervention. The pathophysiology of S. pneumoniae is well established and the role of the polysaccharide capsule, pneumolysin, neuraminidases, and zinc metalloproteinases in ocular infections described. Additionally, key virulence factors of the viridans group streptococci such as cytolysins and proteases have been outlined, but there is a paucity of research on the remaining streptococcus species. These virulence factors tend to result in aggressive disease. Clinically, S. pneumoniae is implicated in 2.7-41.2% of bacterial conjunctivitis cases, more predominant in the pediatric population, and is implicated in 1.8-10.7% of bacterial keratitis isolates. Streptococcus bacteria are significantly implicated in acute postoperative, post-intravitreal, and bleb-associated endophthalmitis, responsible for 10.3-37.5, 29.4, and 57.1% of cases, respectively. Group A and B streptococcus endogenous endophthalmitis is rare, but has a very poor prognosis. Inappropriate prescription of antibiotics in cases of non-bacterial aetiology has contributed to increasing resistance, and a clinical index is needed to more accurately monitor this. Furthermore, there is an increasing need for prospective, surveillance studies of antimicrobial resistance in ocular pathogens, as well as point-of-care testing using molecular techniques.

Case Study of Endogenous Streptococcal Endophthalmitis in the Critical Care Setting

We report a rare case of orbital cellulitis and endogenous endophthalmitis, sepsis, meningitis with a brain abscess and a septic knee secondary to Streptococcus pneumonia.

The problems of diagnosis, utility of CT and MRI scanning in the intensive care setting is discussed. The patient was admitted in an obtundated state to the ICU, was noted to have sepsis with blood culture positivity for S pneumoniae. She was noted to have meningitis, a septic knee, a brain abscess and conjunctival injection. CT and MRI scanning did not reveal any ocular or orbital abnormalities. Patient began with a sore throat and knee pain. Despite antibiotic treatment, she became septic with blood culture positivity for S. pneumoniae. She was noted to have knee cellulitis and a brain abscess. 

Streptococcus pneumoniae endophthalmitis: clinical settings, antibiotic susceptibility, and visual outcomes

Streptococcus pneumoniae endophthalmitis is clinically more severe, more difficult to treat, and carry a higher risk of vision loss, evisceration, or enucleation. This study is to investigate the clinical settings, antibiotic susceptibility, and visual outcomes of S. pneumoniae endophthalmitis at a tertiary referral center in Taiwan. S. pneumoniae endophthalmitis was diagnosed in 38 eyes of 38 patients. The main clinical features were postcataract endophthalmitis (n = 13, 34%) and endophthalmitis associated with corneal ulcer (n = 12, 32%), trauma (n = 6, 16%), endogenous etiology (n = 4, 11%), trabeculectomy (n = 2, 5%), and pterygium excision-related scleral ulcer (n = 1, 3%). Presenting visual acuity ranged from counting fingers to no light perception. Pars plana vitrectomy with intravitreal antibiotics was performed in 17 eyes (39%) in primary or secondary treatments. S. pneumoniae isolates were susceptible to vancomycin (38/38, 100%), penicillin (37/38, 97%), ceftriaxone (37/38, 97%), cefuroxime (12/15, 80%), levofloxacin (13/15 ,87%), and moxifloxacin (15/17, 88%). Final visual acuity was better than 20/400 in 3 of 38 eyes (8%), 5/200 to hand motions in 3 eyes (8%), and light perception to no light perception in 32 eyes (84%). Ten eyes (26%) underwent evisceration or enucleation. Although S. pneumoniae isolates were susceptible to vancomycin, S. pneumoniae endophthalmitis had a very poor visual prognosis.

Endophthalmitis in Oman: A descriptive retrospective multi-center study

PURPOSE:

The aim of this study is to report the anatomical and functional outcome, microbiology profile and treatment used for endophthalmitis in Oman.

DESIGN:

The study design involves retrospective descriptive multicenter study.

METHODS:

Demographic and clinical data of patients diagnosed with endophthalmitis over a period of 9 years were collected in three tertiary hospitals in Oman.

RESULTS:

A total of 50 endophthalmitis cases were included in the study. Exogenous endophthalmitis was diagnosed in 48 cases, whereas 2 cases were endogenous endophthalmitis. Culture-positive cases constituted 16 cases (32%) out of these, 12 cases were Gram-positive, 3 cases were Gram-negative and one case had a positive fungal culture. Immediate first-line treatment was vitreous tap and inject in 33 eyes and vitrectomy in 13 eyes. In 45 eyes in which the visual acuity (VA) was recorded; VA after treatment improved in 22 eyes (49%), remained the same in 16 eyes (36%) and worsened in 7 eyes (16%).

CONCLUSION:

Although endophthalmitis is rare, it is a devastating ocular emergency. Early diagnosis and prompt intervention are crucial in management. Awareness among the patients undergoing intraocular surgeries about this rare condition is very crucial. Moreover, frontline health-care providers must be aware and critical if they encounter patients with suspicion of endophthalmitis as early recognition, prompt referral, and timely treatment are the key for better visual prognosis. Finally, establishing a National Endophthalmitis Registry is recommended as it will help analyze the incidence, treatment instituted and the outcome of this condition across Oman.

Specific PCR and Quantitative Real-Time PCR in Ocular Samples from Acute and Delayed-Onset Postoperative Endophthalmitis

PURPOSE

Rapid identification of virulent pathogens is essential to strengthen the therapeutic strategy of acute endophthalmitis.

OBJECTIVES

This study sought to compare the contribution of a combination of polymerase chain reaction (PCR)-based tests to culture methods, in patients with postoperative endophthalmitis.

DESIGN

Prospective multicenter study diagnostic evaluation.

METHODS

Setting: university referral centers.

PARTICIPANTS

153 consecutive patients presenting with acute or delayed-onset postoperative endophthalmitis, between 2008 and 2015. There were a total of 284 aqueous humor (AH) and/or vitreous fluid (VF) samples. Outcomes and measurements: microbiological tests of intraocular samples included bacterial culturing of pediatric blood culture bottles; 16SrDNA amplification and sequencing (panbacterial PCR) for detection and identification of all bacterial species; real-time PCR (qPCR) assays targeting the femA or lytA gene for detection of Staphylococcus aureus (S. aureus) or Streptococcus pneumoniae (S. pneumoniae), respectively; and a qPCR assay targeting the tuf gene for detection and quantification of Staphylococcus epidermidis (S. epidermidis).

RESULTS

At the time of admission, the rate of detection of microorganisms by PCR-based tests was not significantly different than that by culturing (38% versus 30% in AH samples [n = 69]; 66% versus 63% in VF samples [n = 82], respectively). In contrast, after 1 intravitreal injection (IVI) of antibiotics, the identification rate by PCR-based tests was higher than that in VF by culturing (62% vs 48%, respectively; n = 94; P = 0.05). Bacteria were identified in 70% of patients, with a predominance of Gram-positive bacteria (93%). Specific qPCR tests targeting S. aureus and S. pneumoniae did not provide additional diagnoses but provided earlier results. The S. epidermidis load in vitreous at the time of patients' admission was higher in cases of final visual acuity (VA) of <20/40 (127,118 ± 125,848 DNA copies/mL) in patients with a VA of ≥20/40 (40350,000 ± 46,912 DNA copies/mL; P = 0.09). No significant changes in S. epidermidis load was found after one IVI.

CONCLUSIONS

Patients with acute or delayed-onset endophthalmitis should benefit from microbiological identification in vitreous samples by combined analysis using bacterial cultures in pediatric blood culture bottles and panbacterial PCR. The last test was more effective than cultures in vitreous samples collected after an IVI of antibiotics. The qPCR tests targeting S. aureus and S. pneumoniae gave earlier results than culture and panbacterial PCR but did not provide additional diagnoses. As for S. epidermidis infections, determination of bacterial load using the qPCR test targeting the tuf gene could help evaluation of the visual prognosis of patients. Its role in the follow-up of patients after antibiotic treatment needs further investigation.

A Pyrrhic Victory: The PMN Response to Ocular Bacterial Infections

Some tissues of the eye are susceptible to damage due to their exposure to the outside environment and inability to regenerate. Immune privilege, although beneficial to the eye in terms of homeostasis and protection, can be harmful when breached or when an aberrant response occurs in the face of challenge. In this review, we highlight the role of the PMN (polymorphonuclear leukocyte) in different bacterial ocular infections that invade the immune privileged eye at the anterior and posterior segments: keratitis, conjunctivitis, uveitis, and endophthalmitis. Interestingly, the PMN response from the host seems to be necessary for pathogen clearance in ocular disease, but the inflammatory response can also be detrimental to vision retention. This “Pyrrhic Victory” scenario is explored in each type of ocular infection, with details on PMN recruitment and response at the site of ocular infection. In addition, we emphasize the differences in PMN responses between each ocular disease and its most common corresponding bacterial pathogen. The in vitro and animal models used to identify PMN responses, such as recruitment, phagocytosis, degranulation, and NETosis, are also outlined in each ocular infection. This detailed study of the ocular acute immune response to infection could provide novel therapeutic strategies for blinding diseases, provide more general information on ocular PMN responses, and reveal areas of bacterial ocular infection research that lack PMN response studies.

Infectious endophthalmitis leading to evisceration: spectrum of bacterial and fungal pathogens and antibacterial susceptibility profile

Purpose

To describe the spectrum of bacterial and fungal pathogens in cases of endophthalmitis requiring evisceration and report their antimicrobial susceptibilities.

Methods

Retrospective, consecutive, and descriptive case series of endophthalmitis that underwent evisceration from January 2004 to December 2017. Vitreous samples from all patients had been investigated for bacteria and fungus using institutional protocol. Bacterial isolates were identified using analytical profile index (API) system until 2010 and Vitek-2 compact system (bioMérieux, France), thereafter. The susceptibility of bacterial isolates to a variety of antibiotics was determined by the Kirby-Bauer disk-diffusion method.

Results

Of 791 cases reviewed, culture positivity was reported in 388 cases (48.92%). Commonest clinical setting of endophthalmitis necessitating evisceration was post-microbial keratitis (58%), followed by post-trauma and post-cataract surgery (14–15%). The commonest isolate was Streptococcus pneumoniae, seen in 68 samples overall (17.52%). One hundred and eighty-three isolates (47.16%) were gram-positive, 86 (22.16%) were gram-negative, and fungi constituted 137 (35.3%) isolates. Streptococcus pneumoniae was the commonest gram-positive bacterial isolate seen in 68/183 samples (37.15%). Among gram-negative organisms, the commonest was Pseudomonas aeruginosa seen in 47/86 (54.65%). Aspergillus spp. formed the commonest fungal isolate, 58/137 (42.33%). The susceptibility of the gram-positive bacteria was highest with vancomycin, 136/147 (92.51%) and for gram-negative bacteria was seen best with imipenem 24/29 (82.75%). Susceptibility to ceftazidime was 31/61 (50.81%) in 31/61.

Conclusion

Endophthalmitis due to Pneumococci, Aspergillus, and Pseudomonas can be very fulminant and progress to require evisceration in spite of prompt and appropriate treatment.

Predictive factors in the treatment of streptococcal endophthalmitis

Objective

To evaluate visual outcomes and possible predictive factors in the treatment of infectious endophthalmitis caused by Streptococcus species during 2012–2016 at a large referral eye center in northeastern Thailand.

Methods

A retrospective medical record chart review of patients with culture-positive endophthalmitis caused by Streptococcus species was conducted. Demographic data including age, gender, occupation, duration of symptoms, time to surgery, surgical procedures, initial visual acuity at presentation, and final visual acuity after treatment were collected and analyzed. Possible predictive factors associated with improved visual outcomes were also studied.

Results

Forty-five eyes of 45 patients were recruited for the study. The 3 most common types of endophthalmitis were postoperative (35.56%), posttraumatic (20%), and endogenous (15.56%). At presentation, most patients (95.56%) had visual acuity of hand motion (55.56%), light perception (28.89%), or no light perception (11.11%). The 3 most common isolates were Streptococcus pneumoniae (44.44%), Group B β-hemolytic Streptococcus (26.68%), and Streptococcus viridans (20%). Most patients (62.22%) were treated with surgical interventions, either pars plana vitrectomy with intravitreal antibiotics or pars plana vitrectomy with intravitreal antibiotics and silicone oil tamponade. After treatment, improved visual outcome was noted in only 9 patients (20%), and no visual improvement was seen in 36 patients (80%). Evisceration and enucleation were performed in 15 patients (33.33%). The only possible predictive factor associated with improved visual outcomes was early vitrectomy, performed within 3 days.

Conclusion

Streptococcal endophthalmitis is often associated with poor visual prognosis. Only 9 patients (20%) had improved vision after treatment. The only possible predictive factor associated with improved visual outcomes was vitrectomy within 3 days. Early diagnosis and early vitrectomy are therefore recommended.

Predictors of visual outcome and the role of early vitrectomy in streptococcal endophthalmitis

IMPORTANCE

Streptococcal endophthalmitis has devastating sequelae. This study aims to identify factors which may be targeted to optimize patient outcomes.

BACKGROUND

This study investigated characteristics influencing visual outcomes and the role of early vitrectomy.

DESIGN

Retrospective observational case series of consecutive patients was conducted.

PARTICIPANTS

All patients with a culture-positive diagnosis of streptococcal endophthalmitis treated at a tertiary ophthalmology referral centre between July 1997 and February 2012 were included.

METHODS

Patient records were reviewed and data collected on their presentation, examination, microbiology results, procedures and final outcome.

MAIN OUTCOME MEASURES

Visual acuity (VA) and enucleation/evisceration were measured.

RESULTS

Of the 101 patients, 35.6% presented with a VA of hand movements and 42.6% with light perception (LP). Final VA was poor (6/60 or worse) in 77.6% and 24.7% were enucleated/eviscerated. Presenting VA of LP or worse (P = 0.008), no view of fundus (P = 0.001), large number of organisms (P < 0.001), recognition of Streptococcus on Gram stain (P = 0.010), heavy growth on culture (P < 0.001) and more intravitreal injections (P = 0.038) were significantly associated with poor visual outcome (6/60 or worse). Presenting VA of LP or worse (P = 0.042) and non-viridans Streptococcus species (P = 0.002) were significantly associated with enucleation/evisceration. Fifteen patients (14.9%) had early vitrectomy within 48 h which was not associated with poor final VA or removal of the eye (P = 1.000).

CONCLUSIONS AND RELEVANCE

Early vitrectomy did not influence visual outcome in this cohort. Microbiology results were useful in predicting poor outcomes, and may allow clinicians to make early treatment decisions and provide prognostic information for patients.

Perioperative antibiotics for prevention of acute endophthalmitis after cataract surgery

BACKGROUND

Endophthalmitis is a severe inflammation of the anterior or posterior (or both) chambers of the eye that may be sterile or associated with infection. It is a potentially vision-threatening complication of cataract surgery. Prophylactic measures for endophthalmitis are targeted against various sources of infection.

OBJECTIVES

To evaluate the effects of perioperative antibiotic prophylaxis for endophthalmitis following cataract surgery compared with no prophylaxis or other form of prophylaxis.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2016, Issue 12), Ovid MEDLINE, Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid MEDLINE Daily (January 1946 to December 2016), Embase (January 1980 to December 2016), Latin American and Caribbean Health Sciences Literature Database (LILACS) (1982 to December 2016),the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov), and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We used no date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 6 December 2016. We also searched for additional studies that cited any included trials using the Science Citation Index.

SELECTION CRITERIA

We included randomized controlled trials that enrolled adults undergoing cataract surgery (any method and incision type) for lens opacities due to any origin. We included trials that evaluated preoperative antibiotics, intraoperative (intracameral, subconjunctival or systemic), or postoperative antibiotic prophylaxis for acute endophthalmitis. We excluded studies that evaluated antiseptic preoperative preparations using agents such as povidone iodine or antibiotics for treating acute endophthalmitis after cataract surgery.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed abstracts and full-text articles for eligibility, assessed the risk of bias for each included study, and abstracted data.

MAIN RESULTS

Five studies met the inclusion criteria for this review, including 101,005 adults and 132 endophthalmitis cases. While the sample size was very large, the heterogeneity of the study designs and modes of antibiotic delivery made it impossible to conduct a formal meta-analysis. Interventions investigated included the utility of adding vancomycin and gentamycin to the irrigating solution compared with standard balanced saline solution irrigation alone, use of intracameral cefuroxime with or without topical levofloxacin perioperatively, periocular penicillin injections and topical chloramphenicol-sulfadimidine drops compared with topical antibiotics alone, and mode of antibiotic delivery (subconjunctival versus retrobulbar injections; fixed versus separate instillation of gatifloxacin and prednisolone). The risk of bias among studies was low to unclear due to information not being reported. We identified one ongoing study.Two studies compared any antibiotic with no antibiotic. One study, which compared irrigation with antibiotics in balanced salt solution (BSS) versus BSS alone, was not sufficiently powered to detect differences in endophthalmitis between groups (very low-certainty evidence). One study found reduced risk of endophthalmitis when combining intracameral cefuroxime and topical levofloxacin (risk ratio (RR) 0.14, 95% confidence interval (CI) 0.03 to 0.63; 8106 participants; high-certainty evidence) or using intracameral cefuroxime alone (RR 0.21, CI 0.06 to 0.74; 8110 participants; high-certainty evidence) compared with placebo, and an uncertain effect when using topical levofloxacin alone compared with placebo (RR 0.72, CI 0.32 to 1.61; 8103 participants; moderate-certainty evidence).Two studies found reduced risk of endophthalmitis when combining antibiotic injections during surgery and topical antibiotics compared with topical antibiotics alone (risk ratio (RR) 0.33, 95% confidence interval (CI) 0.12 to 0.92 (periocular penicillin and topical chloramphenicol-sulfadimidine; 6618 participants; moderate-certainty evidence); and RR 0.20, 95% CI 0.04 to 0.91 (intracameral cefuroxime and topical levofloxacin; 8101 participants; high-certainty evidence)).One study, which compared fixed versus separate instillation of gatifloxacin and prednisolone, was not sufficiently powered to detect differences in endophthalmitis between groups (very low-certainty evidence). Another study found no evidence of a difference in endophthalmitis when comparing subconjunctival versus retrobulbar antibiotic injections (RR 0.85, 95% CI 0.55 to 1.32; 77,015 participants; moderate-certainty evidence).Two studies reported any visual acuity outcome; one study, which compared fixed versus separate instillation of gatifloxacin and prednisolone, reported only that mean visual acuity was the same for both groups at 20 days postoperation. In the other study, the difference in the proportion of eyes with final visual acuity greater than 20/40 following endophthalmitis between groups receiving intracameral cefuroxime with or without topical levofloxacin compared with no intracameral cefuroxime was uncertain (RR 0.69, 95% CI 0.22 to 2.11; 29 participants; moderate-certainty evidence).Only one study reported adverse events (1 of 129 eyes had pupillary membrane in front of the intraocular lens and 8 eyes showed posterior capsule opacity). No study reported outcomes related to quality of life or economic outcomes.

AUTHORS' CONCLUSIONS

Multiple measures for preventing endophthalmitis following cataract surgery have been studied. High-certainty evidence shows that injection with cefuroxime with or without topical levofloxacin lowers the chance of endophthalmitis after surgery, and there is moderate-certainty evidence to suggest that using antibiotic eye drops in addition to antibiotic injection probably lowers the chance of endophthalmitis compared with using injections or eye drops alone. Clinical trials with rare outcomes require very large sample sizes and are quite costly to conduct; thus, it is unlikely that many additional clinical trials will be conducted to evaluate currently available prophylaxis. Practitioners should rely on current evidence to make informed decisions regarding prophylaxis choices.

A Case of Invasive Pneumococcal Infection with Septic Shock and Rare Complications

Invasive pneumococcus is a serious illness with potentially devastating outcomes. A 64-year-old female with a medical history of psoriatic arthritis and diabetes was transferred from an outside hospital for ventilator dependent respiratory failure and altered mental status. She initially presented with worsening back pain and was found to have leukocytosis with bandemia and acute renal failure but she was in septic shock upon arrival to our tertiary care center. Her blood cultures grew Streptococcus pneumoniae and MRI of the brain revealed pus within the posterior lateral ventricles and multiple infarcts. MRI of the spine revealed a psoas abscess. Transesophageal echocardiogram revealed mitral valve vegetation and her right eye developed endogenous endophthalmitis. She was treated with intravenous and intravitreal antibiotics and underwent drainage of the abscess with no improvement in mental status. Repeat imaging revealed multiple new thalamic, basal ganglia, and parietal lobe infarcts likely from septic emboli. After a protracted ICU stay, the patient’s family opted for comfort care. The incidence of invasive pneumococcal infections has declined rapidly since the advent of antibiotics and vaccines. With the growing incidence of antibiotic resistance as well as the emergence of new immunomodulating drugs for various pathologies, there is a concern that invasive infections will reemerge. Ventriculitis and endogenous endophthalmitis are very rare complications of pneumococcal bacteremia.

Differential bacterial gene expression during experimental pneumococcal endophthalmitis

Streptococcus pneumoniae (pneumococcus) is a potential cause of bacterial endophthalmitis in humans that can result in ocular morbidity. We sought to identify pneumococcal genes that are differentially expressed during growth in the vitreous humor of the eye in an experimental endophthalmitis model. Microarray analysis was used to identify genes that were differentially expressed when pneumococci replicated in the vitreous of rabbit eyes as compared with bacteria grown in vitro in Todd Hewitt medium. Array results were verified by quantitative real-time PCR analysis of representative genes. Select genes potentially playing a role in virulence during endophthalmitis were deleted, and mutants were tested for reduced eye pathogenesis and altered adhesion to host cells. Array analysis identified 134 genes that were differentially expressed during endophthalmitis; 112 genes demonstrated increased expression during growth in the eye whereas 22 were downregulated. Real-time analysis verified increased expression of neuraminidase A (NanA; SP1693), neuraminidase B (NanB; SP1687) and serine protease (SP1954), and decreased expression of RlrA (SP0461) and choline transporter (SP1861). Mutation of NanA and NanB had no major effect on pathogenesis. Loss of SP1954 led to increased adherence to host cells. S. pneumoniae enhances and represses the expression of a variety of genes during endophthalmitis. While some of these genes reflect changes in metabolic requirements, some appear to play a role in immune evasion and pathogenesis in the eye.

Perioperative antibiotics for prevention of acute endophthalmitis after cataract surgery

BACKGROUND

Endophthalmitis is a severe inflammation of the anterior and/or posterior chambers of the eye that may be sterile or associated with infection. It is a potentially vision-threatening complication of cataract surgery. Prophylactic measures for endophthalmitis are targeted against various sources of infection.

OBJECTIVES

The objective of this review was to evaluate the effects of perioperative antibiotic prophylaxis for endophthalmitis following cataract surgery.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 10), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE, (January 1950 to October 2012), EMBASE (January 1980 to October 2012), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to October 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 25 October 2012. We also searched for additional studies that cited any included trials using the Science Citation Index.

SELECTION CRITERIA

We included randomized controlled trials that enrolled adults undergoing cataract surgery (any method and incision type) for lens opacities due to any origin. Trials that evaluated preoperative antibiotics, intraoperative (intracameral, subconjunctival or systemic) or postoperative antibiotic prophylaxis for acute endophthalmitis were included. We did not include studies that evaluated antiseptic preoperative preparations using agents such as povidone iodine, nor did we include studies that evaluated antibiotics for treating acute endophthalmitis after cataract surgery.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed abstracts and full-text articles for eligibility, assessed the risk of bias for each included study, and abstracted data.

MAIN RESULTS

Four studies met the inclusion criteria for this review, including 100,876 adults and 131 endophthalmitis cases. While the sample size is very large, the heterogeneity of the study designs and modes of antibiotic delivery made it impossible to conduct a formal meta-analysis. Interventions investigated in the studies included the utility of adding vancomycin and gentamycin to the irrigating solution compared with standard balanced saline solution irrigation alone, use of intracameral cefuroxime and/or topical levofloxacin perioperatively, periocular penicillin injections and topical chloramphenicol-sulphadimidine drops compared with topical antibiotics alone, and mode of antibiotic delivery (subconjunctival versus retrobulbar injections). Two studies with adequate sample sizes to evaluate a rare outcome found reduced risk of endophthalmitis with antibiotic injections during surgery compared with topical antibiotics alone: risk ratio (RR) 0.33, 95% confidence interval (CI) 0.12 to 0.92 (periocular penicillin versus topical chloramphenicol-sulphadimidine) and RR 0.21, 95% CI 0.06 to 0.74 (intracameral cefuroxime versus topical levofloxacin). Another study found no significant difference in endophthalmitis when comparing subconjunctival versus retrobulbar antibiotic injections (RR 0.85, 95% CI 0.55 to 1.32). The fourth study which compared irrigation with balanced salt solution (BSS) alone versus BSS with antibiotics was not sufficiently powered to detect differences in endophthalmitis between groups. The risk of bias among studies was low to unclear due to information not being reported.

AUTHORS' CONCLUSIONS

Multiple measures for preventing endophthalmitis following cataract surgery have been studied. One of the included studies, the ESCRS (European Society of Cataract and Refractive Surgeons) study, was performed using contemporary surgical technique and employed cefuroxime, an antibiotic commonly used in many parts of the world. Clinical trials with rare outcomes require very large sample sizes and are quite costly to conduct; thus, it is unlikely that additional clinical trials will be conducted to evaluate currently available prophylaxis. Practitioners should rely on current evidence to make informed decisions regarding prophylaxis choices.

The cholesterol-dependent cytolysin pneumolysin from Streptococcus pneumoniae binds to lipid raft microdomains in human corneal epithelial cells

Streptococcus pneumoniae (pneumococcus) is an opportunistic bacterial pathogen responsible for causing several human diseases including pneumonia, meningitis, and otitis media. Pneumococcus is also a major cause of human ocular infections and is commonly isolated in cases of bacterial keratitis, an infection of the cornea. The ocular pathology that occurs during pneumococcal keratitis is partly due to the actions of pneumolysin (Ply), a cholesterol-dependent cytolysin produced by pneumococcus. The lytic mechanism of Ply is a three step process beginning with surface binding to cholesterol. Multiple Ply monomers then oligomerize to form a prepore. The prepore then undergoes a conformational change that creates a large pore in the host cell membrane, resulting in cell lysis. We engineered a collection of single amino acid substitution mutants at residues (A370, A406, W433, and L460) that are crucial to the progression of the lytic mechanism and determined the effects that these mutations had on lytic function. Both Ply^WT and the mutant Ply molecules (Ply^A370G, Ply^A370E, Ply^A406G, Ply^A406E, Ply^W433G, Ply^W433E, Ply^W433F, Ply^L460G, and Ply^L460E) were able to bind to the surface of human corneal epithelial cells (HCECs) with similar efficiency. Additionally, Ply^WT localized to cholesterol-rich microdomains on the HCEC surface, however, only one mutant (Ply^A370G) was able to duplicate this behavior. Four of the 9 mutant Ply molecules (Ply^A370E, Ply^W433G, Ply^W433E, and Ply^L460E) were deficient in oligomer formation. Lastly, all of the mutant Ply molecules, except Ply^A370G, exhibited significantly impaired lytic activity on HCECs. The other 8 mutants all experienced a reduction in lytic activity, but 4 of the 8 retained the ability to oligomerize. A thorough understanding of the molecular interactions that occur between Ply and the target cell, could lead to targeted treatments aimed to reduce the pathology observed during pneumococcal keratitis.

Streptococcus pneumoniae ocular infections, prominent role of unencapsulated isolates in conjunctivitis

The aim of this study was to determine the characteristics and shifts in serotype distribution of pneumococcal isolates causing ocular infections in a region of northern Spain in two periods: 1999-2010 for episodes of conjunctivitis (n = 612) and 1980-2010 for uncommon and more severe non-conjunctival ocular infections (n = 36). All isolates were serotyped and non-typeable isolates were confirmed as unencapsulated by multiplex-PCR of the lytA, ply and cpsA genes. Genotyping was done by pulsed-field gel electrophoresis and multi-locus sequence typing. Most conjunctivitis cases occurred in children under 5 years old (89.5%), and more severe non-conjunctival ocular infections occurred in patients older than 25 years (86.1%). Unencapsulated isolates were detected in 213 conjunctivitis episodes (34.8%) and one non-conjunctival infection (2.8%). Rates of unencapsulated isolates were similar throughout the study. Among 399 conjunctival encapsulated isolates, the most prevalent were serotypes 19A (n = 53), 15B (n = 30), 6A (n = 27), 19F (n = 25), 23F (n = 21) and 6B (n = 17). The most prevalent serotypes in non-conjunctival infections were serotype 3 (n = 4), 23F (n = 4), 6B (n = 3) and 19A (n = 3). Conjunctivitis caused by serotypes included in the hepta-valent pneumococcal conjugate vaccine steadily decreased, accounting for 34.9% (22/63) in 1999-2001, 19.7% (23/117) in 2002-04, 13.6% (33/242) in 2005-07 and 3.2% (6/190) in 2008-10. Among the 213 unencapsulated isolates, 31 different pulsed-field gel electrophoresis patterns were identified. The main clonal complexes (CC) were CC941 (ST941, ST942), CC448 (ST448) and CC344 (ST344, ST3097). CC941 was the predominant CC in 1999-2001, 2002-04 and 2005-07, being replaced by CC448 in 2008-10. The multidrug-resistant CC344 was present throughout the study.

Passive immunization with Pneumovax® 23 and pneumolysin in combination with vancomycin for pneumococcal endophthalmitis

Background

Capsule and pneumolysin (PLY) are two major virulence factors of Streptococcus pneumoniae. S. pneumoniae is one of the leading causes of bacterial endophthalmitis. The aim of this study is to determine whether passive immunization with the 23-valent pneumococcal polysaccharide vaccine (Pneumovax^® 23; PPSV23) or PLY protects against pneumococcal endophthalmitis.

Methods

New Zealand white rabbits were passively immunized with antiserum to PLY, PPSV23, a mixture of PPSV23/PLY, or PBS (mock). Vitreous was infected with a clinical strain of S. pneumoniae. In a separate group of experiments, vancomycin was injected 4 hours post-infection (PI) for each passively immunized group. Severity of infection, bacterial recovery, myeloperoxidase (MPO) activity and percent loss of retinal function were determined.

Results

Passive immunization with each antiserum significantly lowered clinical severity compared to mock immunization (PPSV23 = 9.19, PPSV23/PLY = 10.45, PLY = 8.71, Mock = 16.83; P = 0.0467). A significantly higher bacterial load was recovered from the vitreous of PLY passively immunized rabbits 24 hours PI (7.87 log₁₀ CFU) compared to controls (7.10 log₁₀ CFU; P = 0.0134). Retinas from immunized rabbits were more intact. Vitreous of PLY (2.88 MPO untis/mL) and PPSV23/PLY (2.17) passively immunized rabbits had less MPO activity compared to controls (5.64; P = 0.0480), and both passive immunizations (PLY = 31.34% loss of retinal function, PPSV23/PLY = 27.44%) helped to significantly preserve retinal function compared to controls (64.58%; P = 0.0323). When vancomycin was administered 4 hours PI, all eyes were sterile at 24 hours PI. A significantly lower clinical severity was observed for rabbits administered the combination immunization (5.29) or PPSV23 (5.29) with vancomycin treatment compared to controls (17.68; P = 0.0469).

Conclusions

Passive immunization with antisera to these antigens is effective in reducing clinical severity of pneumococcal endophthalmitis in rabbits. Addition of vancomycin to immunization is effective at eliminating the bacteria.

A comparison of pneumolysin activity and concentration in vitro and in vivo in a rabbit endophthalmitis model

The purpose of this study was to determine whether the in vitro activity and concentration of Streptococcus pneumoniae pneumolysin correlated to the pathogenesis of S. pneumoniae endophthalmitis. Five S. pneumoniae clinical endophthalmitis strains were grown in media to similar optical densities (OD), and extracellular milieu was tested for pneumolysin activity by hemolysis of rabbit red blood cells. Pneumolysin concentration was determined using a sandwich ELISA. Rabbit vitreous was injected with 10² colony-forming units (CFU) of 1 of 2 different strains with low hemolytic activity (n = 10 and 12 for strains 4 and 5, respectively) or 1 of 3 different strains with high hemolytic activity (n = 12 per strain). Pathogenesis of endophthalmitis infection was graded by slit lamp examination (SLE) at 24 hours post-infection. Bacteria were recovered from infected vitreous and quantitated. The SLE scores of eyes infected with strains having high hemolytic activity were significantly higher than the scores of those infected with strains having low hemolytic activity (P < 0.05). Pneumolysin concentration in vitro, however, did not correlate with hemolysis or severity of endophthalmitis. Bacterial concentrations from the vitreous infected with 4 of the strains were not significantly different (P > 0.05). These data suggest that pneumolysin hemolytic activity in vitro directly correlates to the pathogenesis of S. pneumoniae endophthalmitis. The protein concentration of pneumolysin, however, is not a reliable indicator of pneumolysin activity.

The Streptococcus pneumoniae capsule is required for full virulence in pneumococcal endophthalmitis

PURPOSE

To determine whether Streptococcus pneumoniae capsule was necessary for pathogenesis of pneumococcal endophthalmitis.

METHODS

An isogenic capsule-deficient strain was created using homologous recombination. New Zealand White rabbits were injected intravitreously with 10(2) colony-forming units (CFU) of the parent strain or the capsule mutant. Slit lamp examination (SLE), electroretinography, and myeloperoxidase activity were performed 24 and 48 hours postinfection (PI). Serial dilutions of vitreous were plated to quantitate CFU, eyes were extracted for histology, and host cytokine mRNA expression was determined.

RESULTS

Eyes infected with the parent strain had significantly higher SLE scores than eyes infected with the capsule-deficient strain 24 and 48 hours PI (P < 0.001). CFU recovered from eyes infected with the capsule mutant were significantly fewer than CFU recovered from eyes infected with the parent strain 24 and 48 hours PI (P < 0.001). The parent strain caused a significantly greater decrease in retinal function and more retinal destruction than the mutant strain 48 hours PI (P = 0.026). Vitreal IL-1β, IL-6, and TNF-α were upregulated by both the parent and mutant strain 12 hours PI. By 48 hours PI, there was significantly more neutrophil infiltration in the vitreous infected with the parent strain.

CONCLUSIONS

Endophthalmitis caused by the encapsulated strain is more damaging to retinal function and structural integrity. These findings indicate that capsule is an important virulence factor of S. pneumoniae endophthalmitis, in contrast to keratitis, suggesting that the anatomic host site in pneumococcal ocular infections is important.

Immunization with pneumolysin protects against both retinal and global damage caused by Streptococcus pneumoniae endophthalmitis

PURPOSE

To determine whether immunization with pneumolysin (PLY) protects against pneumococcal endophthalmitis.

METHODS

New Zealand white rabbits were immunized with a mutant form of PLY that retains only 1% of its cytolytic activity until serum IgG titers were ≥51,200. For a negative control, rabbits were immunized with phosphate-buffered saline (mock). Each vitreous was injected with 10(2) colony-forming units of a clinical endophthalmitis isolate of Streptococcus pneumoniae. Severity of endophthalmitis was graded by slit lamp examination at 24 and 48 h postinfection (PI). Serial dilutions of vitreous were plated for bacterial colony-forming units quantitation, eyes were extracted for histology, and a whole blood survival assay was performed.

RESULTS

Immunized rabbits had a significantly lower mean slit lamp examination score at 24 and 48 h PI when compared to mock immunized rabbits (P ≤ 0.002). There was not a significant difference in bacterial load in the vitreous at 24 or 48 h PI. Histological sections showed that retinas of mock immunized rabbits appeared to be destroyed, whereas those of PLY immunized rabbits remained largely intact. Damage spread to the aqueous humor, stroma, and conjunctiva of mock immunized rabbits by 48 h PI. Minimal damage was observed in the vitreous of PLY immunized rabbits and did not spread to other parts of the eye. Whole blood from immunized rabbits inhibited the growth of bacteria better than whole blood from mock immunized rabbits.

CONCLUSION

Immunization with PLY helps protect the eye from damage caused by pneumococcal endophthalmitis.

Endophthalmitis: Pathogenesis, clinical presentation, management, and perspectives

Endophthalmitis is a rare but sight-threatening complication that can occur after ocular surgery or trauma or as a consequence of systemic infection. To optimize visual outcome, early diagnosis and treatment are essential. Over recent decades, advances in hygienic standards, improved microbiologic and surgical techniques, development of powerful antimicrobial drugs, and the introduction of intravitreal antibiotic therapy have led to a decreased incidence and improved management of endophthalmitis. However, endophthalmitis still represents a serious clinical problem. This review focuses on current principles and techniques for evaluation and treatment of endophthalmitis. In addition, it addresses recent developments regarding antimicrobial treatment and prophylaxis of infectious endophthalmitis.

Pharmacokinetics of linezolid in human non-inflamed vitreous after systemic administration

OBJECTIVES

To determine the concentration-time curves of linezolid in serum and vitreous from 24 patients undergoing vitrectomy.

METHODS

Vitrectomy was performed 1, 2, 4, 8 and 12 h after infusion of 600 mg of linezolid in 20 patients divided into groups of four. Four additional patients were studied 12 h after two separate oral doses of 600 mg of linezolid. Serum samples were obtained 1 h after linezolid administration to determine C(max); vitreous and a second serum sample were taken simultaneously during the vitrectomy in all patients, and the concentrations of linezolid in vitreous (C(v)) and serum (C(s)) were determined.

RESULTS

Among patients who received one intravenous dose of 600 mg of linezolid, the highest mean C(v) was observed at 4 and 8 h following linezolid administration (3.4 and 3.7 mg/L). The highest mean C(v) was observed in patients who received two oral doses of 600 mg of linezolid separated by 12 h (4.5 mg/L), which was higher than the MIC(90) for Staphylococcus epidermidis. The highest C(v)/C(s) ratio was reached 12 h after administration of one and two doses (2.4 and 1.5, respectively).

CONCLUSIONS

Microbiologically significant concentrations of linezolid can be achieved in the vitreous of the non-inflamed human eye after intravenous administration of 600 mg, and it is even better after two doses of 600 mg. It appears that linezolid accumulates in the vitreous, achieving potentially useful steady-state concentrations. An evaluation of clinical efficacy is needed to confirm the perceived utility based on the pharmacokinetics.

Cholesterol as treatment for pneumococcal keratitis: cholesterol-specific inhibition of pneumolysin in the cornea

PURPOSE

The purpose of this study was to determine whether cholesterol, the host cell receptor for pneumolysin of Streptococcus pneumoniae, could effectively treat pneumococcal keratitis.

METHODS

New Zealand White rabbits were intrastromally injected with 10(5) colony-forming units (CFUs) of S. pneumoniae D39. Corneas were treated with topical drops of 1% cholesterol every 2 hours beginning 25 hours after infection and were examined by slit lamp microscopy 24, 36, and 48 hours after infection. Rabbits were killed, and CFUs were recovered from the corneas after the final slit lamp examination (SLE). Minimal inhibitory concentration (MIC) assays of cholesterol against bacteria were performed. Specific inhibition of pneumolysin by cholesterol in the rabbit cornea was tested by intrastromal injection of pneumolysin with or without cholesterol and was compared with cholesterol inhibition of pneumolysin in vitro using hemolysis assays with rabbit erythrocytes.

RESULTS

Corneas treated with cholesterol had significantly lower SLE scores 48 hours after infection than corneas treated with vehicle (P = 0.0015). Treated corneas also had significantly less log(10) CFUs than vehicle-treated corneas (P = 0.0006). Cholesterol at a 1% concentration was bactericidal to bacteria in vitro, and lower concentrations of cholesterol were partially inhibitory in a concentration-dependent manner. Cholesterol also specifically inhibited 1 mug pneumolysin in vivo and up to 50 ng pneumolysin in vitro.

CONCLUSIONS

Topical cholesterol is an effective treatment for S. pneumoniae keratitis. Cholesterol not only inhibits pneumolysin, it is also bactericidal.