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

A Review of Current Practices and Future Trends in Body Fluid Testing

BACKGROUND

Body fluid testing in the clinical chemistry laboratory is a cornerstone in the diagnostic workup of pathological effusions. Laboratorians may not be aware of the preanalytical workflows used in the collection of body fluids though the value is evident whenever processes change or issues arise. The analytical validation requirements can vary depending on the regulations dictated by the laboratories' jurisdiction and accreditor requirements. Much of analytical validation hinges on how useful testing is to clinical care. Usefulness of testing varies with how well established and incorporated the tests and interpretation are in practice guidelines.

CONTENT

Body fluid collections are depicted and described so clinical laboratorians have a basic appreciation of what specimens are submitted to the laboratory for testing. A review of validation requirements by major laboratory accreditation entities is presented. A review of the usefulness and proposed decision limits for common body fluid chemistry analytes is presented. Body fluid tests that show promise and those that are losing (or lost long ago) value are also reviewed.

SUMMARY

The total testing process from collection to result interpretation can be complicated and easily overlooked by the clinical laboratory. This review aims to improve the understanding and awareness of collections, validation, result interpretation, and provide an update on recent trends.

Endogenous Methicillin-Resistant Staphylococcus Aureus (MRSA) Endophthalmitis: A Six-year Series at a Tertiary Care Center

PURPOSE

To investigate the clinical outcomes of methicillin-resistant Staphylococcus aureus (MRSA) endophthalmitis.

METHODS

Clinical courses were reviewed for 17 eyes (15 patients) with endogenous MRSA endophthalmitis based on positive blood and vitreous culture or clinical suspicion between 2013 to 2019 at Duke University Hospitals.

RESULTS

Of 17 eyes, initial VA ranged from 20/40 to light perception. Of 15 patients, 9 had predisposing risk factors for bacteremia. All eyes received intravitreal vancomycin, 13 also received ceftazidime, and 2 also received amikacin instead of ceftazidime. Nine eyes developed retinal detachment; 6 underwent vitrectomy. Final VA ranged from 20/20 to no light perception and was ≥20/200 in 8 eyes. Eleven eyes had improved VA, 2 eyes were unchanged, and 4 were worse.

CONCLUSIONS

This study is the largest series on endogenous MRSA endophthalmitis to date. Patients had a higher proportion of final VA ≥20/200, similarly high rate of RD, and fewer enucleations compared to prior reports.

The Diagnosis and Treatment of Fungal Endophthalmitis: An Update

In recent, large case series of fungal endophthalmitis (FE) that were published by Asian authors, the most frequent etiologic agents for all types of FE are molds (usually Aspergillus species, while Fusarium is the prevalent etiology in keratitis-related FE). Candida was the organism found in most cases of endogenous FE. However, we must keep in mind that prevalence of fungal species varies with the geographical area. Lately, polymerase chain reaction (PCR) was increasingly used for the diagnosis of FE, allowing for very high diagnostic sensitivity, while the costs become more affordable with time. The most important shortcoming of PCR—the limited number of pathogens that can be simultaneously searched for—may be overcome by newer techniques, such as next-generation sequencing. There are even hopes of searching for genetic sequences that codify resistance to antifungals. We must not forget the potential of simpler tests (such as galactomannan and β-d-glucan) in orienting towards a diagnosis of FE. There are few reports about the use of newer antifungals in FE. Echinocandins have low penetration in the vitreous cavity, and may be of use in cases of fungal chorioretinitis (without vitritis), or injected intravitreally as an off-label, salvage therapy.

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.

How to Handle CT-Guided Abscess Drainages in Microbiological Analyses? Sterile Vials vs. Blood Culture Bottles for Transport and Processing

The aim of this investigation was to compare microbiological analyses of 100 computed tomography-guided drainages from infectious foci (thoracic, abdominal, musculoskeletal), transported and analyzed by two widely established techniques, that are (i) sterile vials or (ii) inoculated blood culture bottles. The mean number of detected microorganisms from blood culture (aerobic/anaerobic) or conventional method (sterile vial, solid and broth media) per specimen were comparable with 1.29 and 1.41, respectively (p = 1.0). The conventional method showed a trend towards shorter time-to-result (median 28.62 h) in comparison to blood culture incubation (median 43.55 h) (p = 0.0722). Of note, detection of anaerobes (13% vs. 36%) and the number of detected microorganisms in polymicrobial infections (2.76 vs. 3.26) differed significantly with an advantage towards conventional techniques (p = 0.0015; p = 0.035), especially in abdominal aspirations. Despite substantially overlapping results from both techniques, the conventional approach includes some benefits which justify its role as standard approach.

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.

Endophthalmitis after Cataract Surgery: Changes in Management Based on Microbiologic Cultures

PURPOSE

To assess the utility of microbiologic culture data for the management of endophthalmitis after cataract surgery.

DESIGN

Retrospective, single-center, cohort study.

PARTICIPANTS

All patients treated for endophthalmitis after cataract surgery between January 1, 2014, and December 31, 2017, at a single institution.

METHODS

Endophthalmitis cases were determined from billing records and confirmed with chart review. 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 (VA).

RESULTS

A total of 111 eyes of 111 patients were treated for endophthalmitis after cataract surgery, of which 57 (51%) were culture-positive. After initial treatment of endophthalmitis, a change in clinical management after vitreous culture occurred in 9 of 111 eyes (8%), including 6 of 57 (11%) culture-positive eyes compared with 3 of 54 (6%) culture-negative eyes (P = 0.49). Change in clinical management for culture-positive eyes was based on declining vision (3 eyes), worsening clinical examination results (2 eyes), and retinal detachment (1 case). Change in clinical management for culture-negative endophthalmitis eyes was based on worsening clinical examination results (2 eyes) and declining vision (1 eye). No additional interventions were initiated on the basis of positive culture results. At final follow-up, mean logarithm of the minimum angle of resolution (logMAR) VA was 1.09 (∼20/250) for the culture-positive eyes compared with 0.59 (∼20/80) for culture-negative eyes (adjusted difference, 0.394; 95% confidence interval, 0.02-0.77, P = 0.03). Rhegmatogenous retinal detachments (RRDs) or retinal tears occurred in 19 of 111 eyes (17%) after developing endophthalmitis, and culture-positive eyes developed a secondary RRD in 11 of 57 eyes (19%) compared with 3 of 54 (6%) culture-negative eyes (P = 0.03).

CONCLUSIONS

After endophthalmitis related to cataract surgery, vitreous cultures may have prognostic value for final visual outcomes but have a limited effect on clinical management.

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.

Utility of broad-range 16S rRNA PCR assay versus conventional methods for laboratory diagnosis of bacterial endophthalmitis in a tertiary care hospital

Background

Endophthalmitis, a sight-threatening intraocular infection, can be of postsurgical, post-traumatic or endogenous origin. Laboratory diagnosis-based appropriate therapy can be vision-saving. Conventional culture-based laboratory diagnosis takes time and lacks sensitivity. In this study a broad-range PCR assay was assessed against conventional and automated culture methods in vitreous specimens for accurate microbiological diagnosis.

Aims

To use broad-range PCR assay targeting 16S ribosomal RNA (rRNA) region of bacteria and to assess its performance vis-à-vis conventional and automated culture methods in the laboratory diagnosis of endophthalmitis.

Methods

Vitreous specimens from 195 patients with clinically diagnosed endophthalmitis were processed for classical and automated culture methods, antimicrobial sensitivity and broad-range PCR assay targeting 762 bp region of 16S rRNA followed by nucleotide sequencing by Sanger’s method. Causative agents were identified from the nucleotide sequences analysed against the GenBank database, and organisms were identified using the Clinical and Laboratory Standards Institute (CLSI) MM18A guidelines.

Results

Bacteria could be detected from 127 (65.13%) of the 195 vitreous specimens by broad-range PCR assay; bacterial isolation was possible from 17 (8.7%) and 60 (30.76%) of these specimens by conventional and automated culture methods, respectively (p<0.0001). PCR assay could detect two uncultured bacterium, and in five cases the bacterial identity could not be determined from NCBI database matching.

Conclusion

Broad-range PCR assay could provide definitive microbial diagnosis within 24 hours in significantly more patients (p<0.0001). Some rare organisms could be detected, useful in treatment modalities. Automated culture was significantly more sensitive than conventional culture.