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

Endogenous Endophthalmitis - A Major Review

Endogenous endophthalmitis (EE) is an uncommon but potentially devastating ocular infection involving the inner layers of the eye. The global incidence of EE is on the rise. Common ocular signs and symptoms associated with EE include conjunctival injection, ocular pain, and reduced visual acuity. On clinical examination, a history of prior or coexisting systemic infections, symptoms (e.g., fever, malaise), and localizing features may be noted. Clinical diagnosis is often challenging, resulting in critical delays that contribute to a poor prognosis. Blood cultures and ocular fluid samples can aid in conforming causative pathogen(s), after which empirical antibiotic therapy, both systemic and intravitreal, should be instated. The use of steroids to suppress inflammation remains controversial. Surgical options include pars plana vitrectomy. Overall prognosis varies depending on host and pathogen factors, and early diagnosis and initiation of appropriate treatment are crucial.

Clinical Practice Update: Management of Infectious Endophthalmitis After Intravitreal Anti-VEGF Injection

Although infectious endophthalmitis after intravitreal antivascular endothelial growth factor injections is rare, it is the most feared and potentially devastating complication of this procedure. There is no high-level evidence to provide definitive guidance on the management of endophthalmitis occurring after intravitreal injection (IVI). This clinical practice update reviews the published literature regarding post-IVI endophthalmitis and highlights areas in which further research is needed to better guide its management.

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.

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.

Evaluation of the Accelerate Pheno System for Rapid Identification and Antimicrobial Susceptibility Testing of Positive Blood Culture Bottles Inoculated with Primary Sterile Specimens from Patients with Suspected Severe Infections

The Accelerate Pheno system is approved for rapid identification and phenotypic antimicrobial susceptibility testing (AST) of microorganisms grown from positive blood cultures inoculated with blood from septic patients. We evaluated the performance of the system for identification and AST from positive blood culture bottles inoculated with primary sterile nonblood specimens from patients with suspected severe infections. One hundred positive blood culture bottles with primary sterile specimens (63 cerebrospinal fluids, 16 ascites, 7 pleural fluids, 4 vitreous fluids, 5 joint aspirates, and 5 other aspirates) from 100 patients were included. Pathogen identification was in agreement with conventional methods for 72 of 100 cultures (72%) and for 81 of 112 (72%) pathogens when considering all pathogens and for 72 of 92 (78%) cultures and 81 of 104 (78%) pathogens when considering on-panel pathogens only. Eight of 31 isolates (26%) not identified by APS were pathogens not included in the APS panel. APS and conventional methods accordingly identified all pathogens from two of nine polymicrobial cultures (22%). APS generated antimicrobial resistance results for 57 pathogens of 57 cultures. The overall category agreement between APS and culture-based AST was 91.2%; and the rate for minor errors was 6.9%, for major was 1.7%, and for very major errors was 0.2%. APS may accelerate pathogen identification and phenotypic AST from positive blood culture bottles inoculated with primary sterile specimens from patients with serious infections, especially for hospitals without an on-site microbiology laboratory. However, the inclusion of nonblood specimens with a high likelihood of polymicrobial infections may result in an inferior performance.

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.

Diagnostic Performance of MALDI-TOF MS Compared to Conventional Microbiological Cultures in Patients with Suspected Endophthalmitis

Purpose: To evaluate the performance and speed of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) when identifying the pathogenic microorganism of endophthalmitis compared to conventional microbiological culturing.Methods: Forty-four patients with suspected endophthalmitis who had undergone vitrectomy were enrolled. Vitreous specimen was analyzed using either conventional culturing or MALDI-TOF MS.Results: The identification rates of the conventional microbiological culture and MALDI-TOF MS were 45.5% (20/44) and 65.9% (29/44), respectively (Kappa value 0.787, P < 0.000). The mean detection times by the standard culturing method and MALDI-TOF MS were 5.39 ± 0.56d and 3.17 ± 0.40d (P < 0.001). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MALDI-TOF MS were 70.59%, 54.17%, 80.00%, and 86.67%, respectively. Polymicrobial endophthalmitis was identified in 6.82% of the patients (3/44) using conventional microbiological culturing. However, MALDI-TOF MS failed to identify any polymicrobial infection.Conclusions: With a higher sensitivity, acceptable specificity and a shorter detection time, MALDI-TOF MS was an efficient technique for the rapid identification of a pathogenic microorganism in endophthalmitis.

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.

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.

Bactec™ blood culture bottles allied to MALDI-TOF mass spectrometry: rapid etiologic diagnosis of bacterial endophthalmitis

Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS) has been used for direct identification of pathogens from blood-inoculated blood culture bottles (BCBs). We showed that MALDI-TOF MS is an useful technique for rapid identification of the causative agents of endophthalmitis from vitreous humor-inoculated BCBs with a simple protocol.

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.