The use of blood culture bottles in endophthalmitis

[Bacterial endogenous endophthalmitis : Spectrum of pathogens and drug therapy]

Endogenous endophthalmitis represents an ophthalmological emergency requiring immediate diagnostics and treatment. Pathogens should be detected using appropriate methods, such as the Freiburg endophthalmitis set. In bacterial endophthalmitis both Gram-positive and Gram-negative bacteria can be detected. Frequent underlying sources include endocarditis, gastrointestinal or urogenital surgery, indwelling venous catheters, liver abscesses, skin or soft tissue infections, meningitis or less commonly, intravenous drug abuse. The treatment consists of systemic and intraocular administration of antibiotics and vitrectomy. Systemic or intraocular corticosteroids can additionally be considered.

EFFICACY OF VITRECTOMY COMBINED WITH INTRAVITREAL ANTIBIOTICS FOR SEVERE POST-TRAUMATIC ENDOPHTHALMITIS

PURPOSE

To explore clinical efficacy of vitrectomy combined with intravitreal antibiotics in treating severe endophthalmitis after open-globe trauma in patients.

METHODS

The records of all patients who received vitrectomy combined with intravitreal for the severe post-traumatic endophthalmitis with light perception or worse between 2010 and 2022 were retrospectively reviewed. Patients received vitrectomy combined with intravitreal antibiotics, repeated intravitreal antibiotics with or without vitreous aspiration, and retinal repair after the infection was controlled. Efficacy of severe post-traumatic endophthalmitis was analyzed.

RESULTS

One hundred and twenty-one patients (121 eyes) were included in this study. The mean BCVA improved from 4.03 ± 0.18 logarithm of the minimum angle of resolution to 1.75 ± 1.41 logarithm of the minimum angle of resolution ( P < 0.001) at the end of the follow-up period, which increased in 106 eyes (87.60%). Infection was successfully controlled in all eyes, 88 eyes within two operations. Pathogens including streptococci (odds ratio [OR] = 6.68, P < 0.001), fungi (OR = 15.23, P < 0.001), and mixed infection (OR = 6.67, P < 0.05) were related to the number of operations. Finally, 60 eyes (49.59%) received silicone oil filling, 25 received gas tamponade, and the remaining 36 received no tamponade; complete vitrectomy was performed in all eyes with intraocular tamponade. All eyes for gas tamponade and no tamponade had been remained stable without retinal detachment and proliferative vitreoretinopathy after 6-month follow-up. The rate of recurrent retinal detachment after silicone oil tamponade was 4.96% (six eyes), including 1.65% (two eyes) of proliferative vitreoretinopathy; these eyes underwent reoperation of retinal detachment repair.

CONCLUSION

Vitrectomy combined with intravitreal antibiotics may be an effective treatment option for severe post-traumatic endophthalmitis.

Acute postoperative endophthalmitis: Microbiology from the laboratory to the bedside

Postoperative endophthalmitis is a dreaded complication of intraocular surgery. Acute presentations need prompt management and good knowledge of differential diagnoses. In the last 10 years, progress in direct microbial detection and identification from intraocular samples included the use of blood culture systems and, more recently, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, improving the rate of bacterial identification. Whatever the method used, diagnostic sensitivity is better for vitreous samples than for aqueous humor samples. Besides, molecular biology techniques have further improved the identification rate of infectious agents in intraocular samples. They also provide faster results compared to culture-based techniques. Quantitative real-time PCR (qPCR) can also determine the bacterial load in intraocular samples. Several studies have shown that intraocular bacterial loads in endophthalmitis patients are usually high, which helps differentiating infection from contamination. The prognostic value of qPCR remains to be validated. Whole genome DNA sequencing technologies facilitate direct and sequencing of single DNA molecules. They have the potential to increase the rate of microbiological identification. Some antibiotic resistance markers (e.g., methicillin resistance in staphylococci and vancomycin resistance in enterococci) may be detected earlier using molecular techniques (usually real-time PCR tests). Early determination of the involved microorganism and their antibiotic resistances can help establishing an earlier therapeutic strategy.

Endophthalmitis After Intravitreal Anti-Vascular Endothelial Factor Injections: Outcomes of Eyes Managed Without Microbiologic Cultures

PURPOSE

To evaluate outcomes of eyes that developed endophthalmitis after intravitreal anti-vascular endothelial growth factor injections that were managed without microbiologic cultures.

DESIGN

Retrospective, single-center, comparative cohort study.

METHODS

We included all eyes with postinjection endophthalmitis from July 1, 2013, to September 1, 2019. Endophthalmitis cases were divided into the culture group if treated with intravitreal antibiotics and a vitreous or aqueous tap sent for microbiologic sampling or into the no culture group if treated with immediate injection of intravitreal antibiotics with an anterior chamber paracentesis that was not sent for microbiologic sampling. The main outcome measures were visual acuity, the incidence of retinal detachment, and the need for additional procedures.

RESULTS

Of 165 endophthalmitis cases identified, 119 (72%) were in the culture group and 46 (28%) were in the no culture group. At endophthalmitis presentation, eyes in the culture group had a mean logMAR VA of 1.98 (∼20/1900) compared with 1.90 (∼20/1600) for eyes in the no culture group (P = .589). At the 6-month follow-up, the mean vision loss was 5.5 lines lost from baseline for the culture group compared with 2.5 lines lost for the no culture group (P = .017). Eyes in the culture group required a subsequent pars plana vitrectomy in 29 of 119 cases (24%) compared with 7 of 46 cases (15%) in the no culture group (P = .29). Six of 119 eyes (5%) in the culture group developed secondary retinal detachments compared with none in the no culture group (P = .143).

CONCLUSIONS

When access to microbiologic facility is not available, the management of postinjection endophthalmitis using intravitreal antibiotics without microbiologic cultures may be an acceptable treatment strategy.

Practical Guidance for Clinical Microbiology Laboratories: Diagnosis of Ocular Infections

The variety and complexity of ocular infections have increased significantly in the last decade since the publication of Cumitech 13B, Laboratory Diagnosis of Ocular Infections (L. D. Gray, P. H. Gilligan, and W. C. Fowler, Cumitech 13B, Laboratory Diagnosis of Ocular Infections, 2010). The purpose of this practical guidance document is to review, for individuals working in clinical microbiology laboratories, current tools used in the laboratory diagnosis of ocular infections. This document begins by describing the complex, delicate anatomy of the eye, which often leads to limitations in specimen quantity, requiring a close working bond between laboratorians and ophthalmologists to ensure high-quality diagnostic care. Descriptions are provided of common ocular infections in developed nations and neglected ocular infections seen in developing nations. Subsequently, preanalytic, analytic, and postanalytic aspects of laboratory diagnosis and antimicrobial susceptibility testing are explored in depth.

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.

The cereus matter of Bacillus endophthalmitis

Bacillus cereus (B. cereus) endophthalmitis is a devastating intraocular infection primarily associated with post-traumatic injuries. The majority of these infections result in substantial vision loss, if not loss of the eye itself, within 12-48 h. Multifactorial mechanisms that lead to the innate intraocular inflammatory response during this disease include the combination of robust bacterial replication, migration of the organism throughout the eye, and toxin production by the organism. Therefore, the window of therapeutic intervention in B. cereus endophthalmitis is quite narrow compared to that of other pathogens which cause this disease. Understanding the interaction of bacterial and host factors is critical in understanding the disease and formulating more rational therapeutics for salvaging vision. In this review, we will discuss clinical and research findings related to B. cereus endophthalmitis in terms of the organism's virulence and inflammogenic potential, and strategies for improving of current therapeutic regimens for this blinding disease.

[Modern diagnosis and treatment of endophthalmitis]

Endophthalmitis is characterized by inflammation of intraocular fluids and tissues, which can lead to irreversible loss of vision if the disease is not treated timely and properly. Endophthalmitis can be classified as exogenous or endogenous depending on the route of infectious agent transmission. Exogenous endophthalmitis occurs when pathogens enter the eye through direct inoculation, while endogenous endophthalmitis develops when pathogens get into the eye through the hematogenous route from a distant infection focus. Classification of endophthalmitis helps determine the etiology and probable causative organisms of the disease. Diagnosis of endophthalmitis is based on clinical data. Early diagnosis and treatment are keys to preserving the eye. Best results are achieved by rapid initiation of an empirical broad-spectrum antimicrobial therapy.

Changes in Management Based on Vitreous Culture in Endophthalmitis After Intravitreal Anti-vascular Endothelial Growth Factor Injection

PURPOSE

To assess whether vitreous culture results affect the clinical management of patients with acute endophthalmitis after intravitreal anti-vascular endothelial growth factor (VEGF) injection.

DESIGN

Retrospective case series.

METHODS

Setting: Single-center.

STUDY POPULATION

Patients who developed endophthalmitis after intravitreal injection of aflibercept, bevacizumab, or ranibizumab between January 1, 2016, and May 31, 2018.

OBSERVATION

A change in clinical management was defined as additional intravitreal antibiotic injections or pars plana vitrectomy.

MAIN OUTCOME MEASURES

A change in clinical management within 2 weeks of initial endophthalmitis culture and treatment; visual acuity.

RESULTS

Of 204,986 intravitreal anti-VEGF injections performed, 60 cases (0.0293%) of endophthalmitis were identified, 18 of which were culture-positive. Six of 60 eyes (10%) had a change in clinical management. A change in clinical management was initiated in 3 of 18 (17%) culture-positive cases compared to 3 of 42 (7%) culture-negative cases (P = .357). Changes in management for culture-positive cases were performed based on declining vision (2 cases) and worsening clinical examination (1 case). Changes in management for culture-negative endophthalmitis cases were performed based on declining vision (1 case) and worsening clinical examination (2 cases). No additional interventions were initiated based on positive-culture results. Comparing vision loss from baseline by culture result, at final follow-up, oral flora-associated culture-positive cases lost 17.5 lines, non-oral flora-associated culture-positive cases lost 9.1 lines, and culture-negative cases lost 2.5 lines of vision (P < .001).

CONCLUSION

Following endophthalmitis from intravitreal injection of anti-VEGF agents, vitreous culture data may help prognosticate visual outcomes but appear to have a limited effect on clinical management.

Diagnostic value of pediatric blood culture bottles for acute postoperative endophthalmitis

OBJECTIVE

To report our experience using conventional culture methods (CM) and pediatric blood culture bottles (PBCBs) for vitreous sample culture of acute postoperative endophthalmitis.

METHODS

A retrospective study was conducted at the Department of Ophthalmology, Hospital das Clinicas, HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, BR, from January 2010 to December 2015, and it included 54 patients with clinically suspected acute postoperative endophthalmitis. Vitreous samples were obtained by vitreous tap or vitrectomy. Samples from January 2010 to December 2011 were cultivated in CM, whereas samples from January 2012 to December 2015 were inoculated in PBCBs. The measured outcome was the yield of positive cultures.

RESULTS

Twenty cases were included in the CM group, and 34 cases were included in the PBCB group. The yield of positive cultures in PBCBs (64.7%) was significantly higher than that in conventional CM (35%, p=0.034). Staphylococcus epidermidis and Streptococcus viridans were the two most commonly found agents.

CONCLUSION

PBCBs can be used successfully in clinically suspected endophthalmitis. The method showed a higher yield of positive cultures than the conventional method. This technique appears to have several advantages over the traditional method: it saves time, as only one medium needs to be inoculated; transportation to a laboratory is easier than in the traditional method, and there is no need to maintain a supply of fresh agar media. The use of PBCBs may be recommended as the primary method for microbiological diagnosis and is especially suitable for office settings and remote clinics.

Silicone Oil in the Surgical Treatment of Traumatic Endophthalmitis

Purpose

To explore the effects of vitrectomy combined with silicone oil injection in the treatment of traumatic endophthalmitis without retinal detachment, and analyze the relative factors.

Methods

Eighteen eyes of 18 patients with traumatic endophthalmitis and without retinal detachment received the treatment of vitrectomy combined with silicone oil filling. Silicone oil removal combined with intraocular lens implantations were performed in all eyes 6 months postoperatively. The visual acuity was measured by logMAR values. Preoperative visual acuity ranged from light perception to 0.1. The mean preoperative intraocular pressure was 9 mmHg with a range from 5 to 25 mmHg. Follow-up ranged from 6 to 43 months with a mean of 18 months.

Results

The postoperative visual acuity ranged from light perception to 0.8 at the last follow-up examination. The visual acuity increased in 15 eyes (83%), and was stable in 3 eyes (17%). The mean postoperative intraocular pressure was 17 mmHg with a range from 10 to 20 mmHg, and was significantly higher than preoperatively (p<0.05). There was no retinal detachment or ocular atrophy. Postoperative complications mainly included fibrosis exudates in the anterior chamber (18 eyes) and temporary intraocular pressure elevation (3 eyes).

Conclusions

Under treatment with systemic antibiotics, vitrectomy combined with silicone oil filling may be a reasonable alternative to standard endophthalmitis treatment using intravitreal antibiotics.

Diagnostic performance of blood culture bottles for vitreous culture compared to conventional microbiological cultures in patients with suspected endophthalmitis

The purpose of this investigation was to evaluate the performance of blood culture bottles in comparison to conventional microbiological culture techniques in detecting causative microorganisms of endophthalmitis and to determine their anti-infective susceptibility profiles. All consecutive cases with clinically suspected endophthalmitis in a university-based ophthalmology department between January 2009 and December 2016 were analysed in this retrospective comparative case series. Samples from 247 patients with suspected endophthalmitis underwent microbiological diagnostic work-up. All three culture methods were performed from 140 vitreous specimens. Vitreous fluid specimens were inoculated in blood culture bottles, aerobic and anaerobic broth solutions, and on solid media. Anti-infective susceptibility profiles were evaluated by semi-automated methods and/or gradient diffusion methods. Microorganisms were grown in 82 of 140 specimens for which all methods were performed (59%). Microorganisms were more frequently grown from blood culture bottles (55%) compared to broth solution (45%, p = 0.007) and solid media (33%, p < 0.0001). Considerable differences in the performance among culture media were detected for fungal pathogens. All grown fungi were detected by blood culture bottles (11 of 11, 100%). Broth solution recovered 64% and solid media 46% of grown fungi. No Gram-positive bacterium was resistant to vancomycin and all Gram-negative pathogens except for one isolate were susceptible to third-generation cephalosporins. In suspected endophthalmitis patients, blood culture bottles have a higher overall pathogen detection rate from vitreous fluid compared to conventional microbiological media, especially for fungi. The initial intravitreal antibiotic therapy with vancomycin plus third-generation cephalosporins appears to be an appropriate treatment approach for bacterial endophthalmitis.

Comparison of methods for identifying causative bacterial microorganisms in presumed acute endophthalmitis: conventional culture, blood culture, and PCR

Background

Identification of bacterial pathogens in endophthalmitis is important to inform antibiotic selection and treatment decisions. Hemoculture bottles and polymerase chain reaction (PCR) analysis have been proposed to offer good detection sensitivity. This study compared the sensitivity and accuracy of a blood culture system, a PCR approach, and conventional culture methods for identification of causative bacteria in cases of acute endophthalmitis.

Methods

Twenty-nine patients with a diagnosis of presumed acute bacterial endophthalmitis who underwent vitreous specimen collection at King Chulalongkorn Memorial Hospital were enrolled in this study. Forty-one specimens were collected. Each specimen was divided into three parts, and each part was analyzed using one of three microbial identification techniques: conventional plate culture, blood culture, and polymerase chain reaction and sequencing. The results of the three methods were then compared.

Results

Bacteria were identified in 15 of the 41 specimens (36.5%). Five (12.2%) specimens were positive by conventional culture methods, 11 (26.8%) were positive by hemoculture, and 11 (26.8%) were positive by PCR. Cohen’s kappa analysis revealed p-values for conventional methods vs. hemoculture, conventional methods vs. PCR, and hemoculture vs. PCR of 0.057, 0.33, and 0.009, respectively. Higher detection rates of Enterococcus faecalis were observed for hemoculture and PCR than for conventional methods.

Conclusions

Blood culture bottles and PCR detection may facilitate bacterial identification in cases of presumed acute endophthalmitis. These techniques should be used in addition to conventional plate culture methods because they provide a greater degree of sensitivity than conventional plate culture alone for the detection of specific microorganisms such as E. faecalis.

Trial registration

Thai Clinical Trial Register No. TCTR20110000024.

Blood culture bottles are superior to conventional media for vitreous culture

BACKGROUND

To compare blood culture bottles and conventional media for the vitreous culture in patients with clinically suspected infectious endophthalmitis.

DESIGN

Retrospective comparative study at KKU Eye Center, Khon Kaen University.

PARTICIPANTS

There were 342 patients with clinically suspected infectious endophthalmitis participated in the study.

METHODS

The vitreous specimens were inoculated in both blood culture bottles and on conventional culture media (blood agar, MacConkey agar, chocolate agar, Sabouraud dextrose agar and thioglycolate broth).

MAIN OUTCOME MEASURES

The number of positive culture yields in both blood culture bottles and conventional media.

RESULTS

Positive culture yields in both methods were found in 151 eyes (49.5%). There were 136 of 151 eyes (90.1%) with positive culture in blood culture bottles, whereas 99 of 151 eyes (65.6%) yielded positive cultures in conventional media. These findings were different with a statistical significance (P < 0.00001) and an odds ratio of 3.47 (95% confidence interval 1.92, 6.63). A combination of blood culture bottles and conventional media improved the yield.

CONCLUSIONS

Blood culture bottles are superior to conventional media for vitreous culture in clinically suspected infectious endophthalmitis. Vitreous culture using blood culture bottles should be recommended as the primary method for microbiological diagnosis. A combination of both methods further improves the positive culture yield.

A 10-year study of membrane filter system versus blood culture bottles in culturing vitrectomy cassette vitreous in infectious endophthalmitis

PURPOSE

To compare the microbiological outcomes of membrane filter system and blood culture bottle techniques in culturing diluted vitrectomy cassette vitreous.

DESIGN

Retrospective comparative case series.

METHODS

Diluted vitrectomy cassette vitreous specimens from March 25, 2002 to July 11, 2012 were cultured using both membrane filter system and blood culture bottles. The isolates were divided into 3 groups: ones that had positive cultures with (1) both membrane filter system and blood culture bottles, (2) membrane filter system only, and (3) blood culture bottles only. The 48-hour as well as 2-week results were documented.

RESULTS

A total of 447 patients with 168 positive cultures were studied. At the 48-hour time point, 126 isolates were documented. Of those, 104 (82%) were culture positive with both membrane filter system and blood culture bottles, 15 (12%) were culture positive only with membrane filter system, and 7 (6%) were culture positive only with blood culture bottles. At the 2-week time point, an additional 42 organisms were isolated. Of those, 19 (45%) were culture positive with both membrane filter system and blood culture bottles, 11 (26%) with membrane filter system only, and 12 (29%) with blood culture bottles only. Out of 168 total isolates, 123 (73%) were culture positive with both membrane filter system and blood culture bottles, 26 (16%) with membrane filter system only, and 19 (11%) with blood culture bottles only. Among all microbiological outcomes, there was no significant difference between membrane filter system and blood culture bottle (P = .37). Of those organisms that were culture positive only with either membrane filter system or blood culture bottle, mold and Mycobacterium species were culture positive more commonly with membrane filter system (P = .034 and P = .016, respectively), and gram-positive organisms were culture positive more commonly with blood culture bottles (P = .021).

CONCLUSIONS

In the current study, a combination of membrane filter system and blood culture bottles for culture of diluted vitrectomy cassette vitreous provides the highest number of positive culture outcomes. The blood culture bottle method is technically easier and represents a viable alternative to the more complex membrane filter system technique.

Prevention, diagnosis, and management of acute postoperative bacterial endophthalmitis

This distillation of the peer-reviewed scientific literature on infection after cataract surgery summarizes background material on epidemiology, etiology, and pathogenesis, describes the roles of surgical technique and antibiotic prophylaxis in prevention, and discusses diagnostic and therapeutic interventions in cases of suspected endophthalmitis.

The additional value of blood culture bottles in the diagnosis of endophthalmitis

PURPOSE

To assess the additional value of blood culture bottles (BCBs) in the diagnosis of endophthalmitis by comparing its culture yield with that of conventional media (CM).

DESIGN

Retrospective consecutive case series.

METHODS

We included patients who were treated between January 2001 and January 2010 for clinically suspected endophthalmitis of any etiology, and had vitreous specimens cultivated in both BCB and CM.

RESULTS

Specimens from 85 eyes from 85 patients were included. The culture yield of BCB was 69%, and that of CM was 72% (difference not significant). Adding the results of BCB improved the yield of CM significantly by 13%, resulting in a combined yield of 81%. The sensitivity of detection of Haemophilus influenzae in BCB seemed lower compared with CM, possibly due to the lack of growth factors in the BCB. There was no difference in yield between specimens obtained by tap or by vitrectomy.

CONCLUSION

In contrast with earlier reports, we did not find BCB superior to CM. The combined use of BCB and CM increased the pathogen detection rate significantly and should therefore be considered as the microbiological method of choice in the work-up of endophthalmitis.

Endogenous endophthalmitis caused by methicillin-resistant Staphylococcus aureus (MRSA)

PURPOSE

To report clinical features, diagnostic features, and outcome in three patients presenting with fulminant endogenous endophthalmitis caused by methicillin-resistant Staphylococcus aureus.

METHODS

Retrospective review of clinical data and microbiological findings in three cases.

RESULTS

All three patients had predisposing conditions for endogenous endophthalmitis (B-cell lymphoma, diabetes mellitus, steroid therapy, or gastrointestinal symptoms, such as vomiting and diarrhea). Two patients were colonized by methicillin-resistant Staphylococcus aureus in typical sites (nose, groin, throat, and conjunctiva), whereas one patient who developed phlebitis at the infusion puncture site followed by bacteremia presented no typical colonization. Despite adequate therapy, two patients lost visual function in the infected eye, one of which had to be enucleated. The other patient's eye regained adequate function.

CONCLUSION

Endogenous endophthalmitis by methicillin-resistant Staphylococcus aureus is a rare but serious condition. Early and specific therapy based on reliable detection of the underlying microorganism may help in preventing loss of visual function.