Vancomycin-resistant Gram-positive bacterial endophthalmitis: epidemiology, treatment options, and outcomes

Antibiotic susceptibility in Endophthalmitis Management Study and intravitreal antibiotic practice trend in India-EMS Report #5

AIM

Analyze antibiotic susceptibility in the Endophthalmitis Management Study (EMS) and compare it with the current intravitreal antibiotic practice trend of members of the Vitreoretinal Society of India (VRSI) practicing in India.

METHODS

The microbiology work-up of undiluted vitreous included microscopy, culture-susceptibility, polymerase chain reaction (PCR), and next-generation sequencing (NGS). VRSI members were invited to the survey. The EMS conventional culture-susceptibility (PCR and NGS excluded) results were compared vis-a-vis gram-positive cocci (GPC), gram-negative bacilli (GNB), and less commonly used antibiotics with the current recommended intravitreal antibiotics. p < 0.05 was considered significant.

RESULTS

Culture and positivity (culture + PCR/NGS) positivity was 28.8% and 56.1%, respectively. GPC was most susceptible to cefazolin, linezolid, and vancomycin; GNB was most susceptible to amikacin, ceftazidime, colistin, and imipenem. There was no susceptibility difference between cefazolin and vancomycin (p = 0.999) and between ceftazidime and imipenem (p = 1.0). Colistin was superior to ceftazidime (p = 0.047) against GNB. The GNB resistant to amikacin (n = 14) were equally susceptible to ceftazidime and colistin; resistant to ceftazidime (n = 16) were susceptible to colistin; and resistant to colistin (n = 7) were susceptible to ceftazidime. The preference of VRSI members (n = 231) practicing in India was a vancomycin-ceftazidime combination (82%), vancomycin for GPC (94%), ceftazidime for GNB (61%), and voriconazole for fungi (74%).

CONCLUSION

In EMS, GPC had good susceptibility to vancomycin; GNB had good susceptibility to ceftazidime and colistin. Given the lower resistance of colistin, a vancomycin-colistin combination could be an alternative empiric treatment in post-cataract endophthalmitis in India.

Evaluating the utility of inflammation score in post-cataract surgery endophthalmitis. Results from a prospective study in India. EMS Report #4

PURPOSE

To investigate if inflammation score (IS), calculated from the cornea, anterior chamber, iris, and vitreous, indicates endophthalmitis severity.

METHODS

In a prospective study, consecutive adults with a clinical diagnosis of post-cataract endophthalmitis within 6 weeks of surgery were recruited. Patients were allocated to IS-based primary treatment (IS < 10: intravitreal injection and IS ≥ 10: vitrectomy) and randomized to two intravitreal antibiotics combinations (vancomycin + ceftazidime and vancomycin + imipenem). Undiluted vitreous microbiology work-up included culture susceptibility, polymerase chain reaction, Sanger sequencing, and targeted next-generation sequencing.

RESULTS

The average age of 175 people was 63.4 ± 10.7 years and included 52.6% small incision cataract surgery and 47.4% phacoemulsification surgery. Severe endophthalmitis (IS ≥ 20), diagnosed in 27.4% of people, had a shorter time to symptoms (average 5.4 vs 8.7 days; P = 0.018), poorer presenting vision (all ≤ hand motion), higher culture positivity (50% vs 30.7%; P = 0.032), and higher Gram-negative bacterial infection (70.8% vs 46.2%; P = 0.042). For IS ≥ 20 discriminant and Gram-negative infection, Spearman's coefficient was 0.7 [P < 0.0001, 95% confidence interval (CI) 0.59-0.82], with an area under the receiver operating characteristic curve of 0.9 (95% CI 0.85-0.94, P < 0.0001), a Youden index J of 0.74, a sensitivity of 87.2%, and a specificity of 87.5%. The final vision of >20/400 and >20/100 was regained in 50.2% and 29.1% of people, respectively. The susceptibility of common Gram-positive cocci and Gram-negative bacilli was the highest for vancomycin (95.0%) and colistin (88.6%), respectively. NGS detected polymicrobial infection in 88.5% of culture-negative endophthalmitis.

CONCLUSIONS

Higher inflammation scores indicated severe disease and Gram-negative infection in post-cataract endophthalmitis.

Targeting bacterial biofilms using vancomycin and multivalent cell-penetrating peptide labeled quantum dots

Bacterial biofilms are highly resilient microbial musters that are difficult to eradicate, driving the development of novel therapeutic strategies. The current study aims to investigate the therapeutic efficacy of cell-penetrating peptide-based targeted delivery of vancomycin functionalized quantum dots in eradicating biofilm formation in gram-positive and gram-negative bacterial strains. The conjugate was characterized using fluorimetry, UV-visible spectroscopy, gel electrophoresis, and zeta potential. The conjugate was then tested for antimicrobial and antibiofilm activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, and it demonstrated excellent antimicrobial as well as antibiofilm activity against all the tested strains. The findings indicated that the conjugate was capable of overcoming bacterial resistance of bacteria in addition to the eradication of biofilms at effective concentrations.

Emerging Antibiotic Resistance Patterns Affect Visual Outcome Treating Acute Endophthalmitis

Background: Examining the effect of antibiotic resistance, use of intravitreal antibiotics and systemic corticosteroids on visual outcome of eyes with acute endophthalmitis. Methods: We included 226 eyes with acute endophthalmitis, treated using a standardized protocol. Visual outcome up to 12 months was assessed related to biopsy results, antibiotics resistance and treatment regimens. Results: Vitreous biopsies were more likely to be culture-positive (41.1%) than anterior chamber biopsies (21.6%, p < 0.0001). Antibiotic resistance for amikacin was found in 19 eyes (24.7%), vancomycin in 29 eyes (31.5%) and moxiflocacin in 14 eyes (16.1%). At presentation 91.53% of eyes had BCVA < 20/40, reducing by 1 month to 69.94% (p < 0.0001) and remaining stable at 12 months. There was no difference in visual outcome for those receiving early systemic corticosteroids. Endophthalmitis following cataract surgery (OR 1.66, 1.04−2.66 95% CI, p = 0.03) and receiving intravitreal vancomycin (OR 3.15, 1.18−8.42 95% CI, p = 0.02) were associated with a greater chance of final BCVA ≥ 20/40. Conclusion: Using vitreous taps with intravitreal antibiotics, despite an increase in resistance to both vancomycin and moxifloxacin, results in a final BCVA > 20/200 in half of eyes and ≥20/40 in a third. Early treatment with intravitreal antibiotics should not be delayed.

Complications of intravitreal injections: 2022

PURPOSE OF REVIEW

This review highlights the complications of both intravitreal injection procedure as well as different intravitreal medications including antivascular endothelial growth factors, antibiotics, antivirals, antifungals, methotrexate, and steroids. Techniques for reducing rates of endophthalmitis will also be discussed.

RECENT FINDINGS

Intravitreal vancomycin can cause hemorrhagic occlusive retinal vasculitis resulting in severe vision loss. Intravitreal brolucizumab is associated with intraocular inflammation and retinal vasculitis resulting in significant vision loss. Face mask use by both patient and physician is not associated with increased risk of endophthalmitis and may decrease culture positive endophthalmitis.

SUMMARY

Intravitreal injections continue to be one of the most commonly performed procedures by ophthalmologists. Although the injections are generally well tolerated, sight-threatening complications can occur including endophthalmitis, retinal detachment, and/or retinal vasculitis. Adverse events associated with specific medications are outlined below. Several safety measures have been shown to reduce rates of endophthalmitis, the most concerning complication of this procedure.

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.

In vitro study examining the effectiveness of antiseptic prophylaxis for antibiotic-resistant bacterial endophthalmitis

PURPOSE

To assess the effectiveness of current antiseptic agents on multidrug-resistant (MDR) isolates in an in vitro setting.

SETTING

Department of Microbiology, The National Maternity Hospital, Dublin, Ireland.

DESIGN

Organisms were selected based on current review of endophthalmitis literature: methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE), Pseudomonas aeruginosa, carbapenem-resistant and extended-spectrum β-lactamase Klebsiella pneumoniae, and vancomycin-resistant (VRE) Enterococcus faecalis.

METHODS

Samples were exposed to povidone-iodine (PVI) 5% and chlorhexidine (CHX) 0.05% for 0.5 minutes, 1 minute, 3 minutes, and 5 minutes. After inactivation, organisms were incubated under standard conditions and growth assessed after 16 hours.

RESULTS

MRSA and MRSE responded to 3-minute PVI exposure. CHX eradicated MRSA growth after 5 minutes but failed to completely suppress MRSE. Pseudomonas and Klebsiella required 3-minute CHX exposure and 5-minute PVI exposure for complete clearance. Eradication of enterococci (VRE positive and negative) was not achieved at 10 minutes of CHX or PVI exposure. Comparison of PVI vs CHX showed a benefit for PVI in MRSA (P < .01) and MRSE (P < .001) eradication at 3 minutes.

CONCLUSIONS

Current recommendations of 3 minutes of antisepsis prior to intraocular surgery are not sufficient for complete eradication of MDR organisms from the ocular surface. A bespoke approach is suggested to patients at risk for carriage of MDR organisms to minimize the risk of endophthalmitis.

Does Endogenous Endophthalmitis Need a More Aggressive Treatment?

Topic: To focus on endogenous endophthalmitis management, particularly etiology-based medical and surgical therapy.Methods: Literature search of published studies from July 1990 to February 2019 on endogenous endophthalmitis available on PubMed was made without any language constraints.Results: A total of 78 articles were retrieved from 728 initially analyzed and 62 studies were included. Although the superiority of vitrectomy over tap and inject techniques is controversial, the most recent publications favor an early surgical approach for endogenous endophthalmitis. Vitrectomy is useful in severe cases complicated by marked vitreous opacity, retinal detachment, poor initial visual acuity, and more virulent pathogens. Oral or intravenous antibiotics are also necessary to treat systemic infection. Vitrectomy is superior to blood cultures in diagnosing the etiology of infection.Conclusions: Endogenous endophthalmitis is an important cause of visual acuity impairment. Prompt treatment with appropriate use of pharmacological or surgical therapy is mandatory to preserve visual function.Abbreviations: IOP: intra-ocular pressure; AIDS: acquired immune deficiency syndrome; EVS: endophthalmitis vitrectomy study; CEVE: complete and early vitrectomy for endophthalmitis.

ENTEROCOCCUS ENDOPHTHALMITIS: Clinical Settings, Antimicrobial Susceptibility, and Management Outcomes

PURPOSE

To report the clinical presentation and management outcome of patients with endophthalmitis caused by Enterococcus species and to report the susceptibility profile of the isolates.

METHODS

Twenty-nine cases with culture-proven Enterococcus endophthalmitis from January 2005 to May 2018 underwent vitrectomy/vitreous biopsy, intravitreal antibiotic with or without additional procedures. The undiluted vitreous was subjected to microbiologic evaluation. A favorable anatomical outcome was defined as preservation of the globe, absence of hypotony, attached retina, and absence of active inflammation at the last visit. Favorable visual outcome was final visual acuity ≥20/400.

RESULTS

There were 24 men (82.8%). Mean age at presentation was 32.89 ± 25.25 years (median 24 years). Inciting event was open globe injury in 18 (62%), endogenous in 5 (17.24%), postcataract surgery in 3 (10.34%), postscleral buckling in 2 (6.89%), and postkeratoplasty in 1 (3.44%). Enterococcus casseliflavus was the commonest species isolated (14/29, 48.27%) followed by E. faecalis (9/29, 31%). Susceptibility to vancomycin was seen in 27/29 isolates (93%). Visual acuity was ≤20/400 in all eyes at presentation and ≥20/400 in 10/29 cases (34.48%) at final visit. Anatomical success was seen in 18/29 eyes (62%). Corneal involvement was high at 24/29 eyes (82.75%).

CONCLUSION

Enterococcus is not an uncommon organism in the setting of endophthalmitis after open globe injury. Resistance to vancomycin is rare. Multidrug resistance pattern is restricted to E. faecalis. Visual outcome is poor despite early and appropriate therapy due to inherent organism virulence.

Microbial Spectrum and Antibacterial Susceptibility of Endophthalmitis Cultures in a Tertiary Referral Center in the Midwestern United States: An Analysis From 295 Patients

Purpose:

This work evaluates the microbial spectrum and antibiotic susceptibility pattern of endophthalmitis cases in a large tertiary referral center in the Midwestern United States.

Methods:

This retrospective case series included patients with clinically diagnosed endophthalmitis between April 14, 2006 and April 14, 2016, in whom ocular samples were submitted to the Microbiology Department at Indiana University. The patients were assessed by 11 vitreoretinal surgeons from 6 different sites in Indianapolis, including Indiana University and private practices, who receive patients from urban, suburban, and rural agricultural areas. Submitted specimens were cultured with the following media: blood agar, chocolate agar, MacConkey agar, and thioglycolate broth.

Results:

A total of 327 specimens from 295 patients were analyzed, with 96 (32.5%) samples from 90 (30.5%) patients meeting the criteria of confirmed growth. Of these 96 positive specimens, 83 (86.5%) organisms were identified as bacterial, and 13 (13.5%) were identified as fungal. Coagulase-negative Staphylococcus was the most common isolate (37.5%). Fifty gram-positive isolates and 10 gram-negative isolates underwent susceptibility testing. All 40 of the gram-positive isolates tested for vancomycin sensitivity were susceptible, whereas all 7 of the gram-negative isolates tested for ceftazidime sensitivity were susceptible.

Conclusions:

Empiric treatment with vancomycin and ceftazidime remains appropriate in most cases of endophthalmitis in the Midwestern United States, with 100% susceptibility of bacterial organisms tested with these antibiotics in this series. The high fungal culture rates in this study highlight the utility of obtaining vitreous cultures and potential need for antifungal agents in suspicious cases.

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.

Bacillus S-Layer-Mediated Innate Interactions During Endophthalmitis

Bacillus endophthalmitis is a severe intraocular infection. Hallmarks of Bacillus endophthalmitis include robust inflammation and rapid loss of vision. We reported that the absence of Bacillus surface layer protein (SLP) significantly blunted endophthalmitis severity. Here, we further investigated SLP in the context of Bacillus-retinal cell interactions and innate immune pathways to explore the mechanisms by which SLP contributes to intraocular inflammation. We compared phenotypes of Wild-type (WT) and SLP deficient (ΔslpA) Bacillus thuringiensis by analyzing bacterial adherence to and phagocytosis by human retinal Muller cells and phagocytosis by mouse neutrophils. Innate immune receptor activation by the Bacillus envelope and purified SLP was analyzed using TLR2/4 reporter cell lines. A synthetic TLR2/4 inhibitor was used as a control for this receptor activation. To induce endophthalmitis, mouse eyes were injected intravitreally with 100 CFU WT or ΔslpA B. thuringiensis. A group of WT infected mice was treated intravitreally with a TLR2/4 inhibitor at 4 h postinfection. At 10 h postinfection, infected eyes were analyzed for viable bacteria, inflammation, and retinal function. We observed that B. thuringiensis SLPs contributed to retinal Muller cell adherence, and protected this pathogen from Muller cell- and neutrophil-mediated phagocytosis. We found that B. thuringiensis envelope activated TLR2 and, surprisingly, TLR4, suggesting the presence of a surface-associated TLR4 agonist in Bacillus. Further investigation showed that purified SLP from B. thuringiensis activated TLR4, as well as TLR2 in vitro. Growth of WT B. thuringiensis was significantly higher and caused greater inflammation in untreated eyes than in eyes treated with the TLR2/4 inhibitor. Retinal function analysis also showed greater retention of A-wave and B-wave function in infected eyes treated with the TLR2/4 inhibitor. The TLR2/4 inhibitor was not antibacterial in vitro, and did not cause inflammation when injected into uninfected eyes. Taken together, these results suggest a potential role for Bacillus SLP in host-bacterial interactions, as well as in endophthalmitis pathogenesis via TLR2- and TLR4-mediated pathways.

Pars Plana Vitrectomy for Endophthalmitis: Microbiologic Spectrum and Clinical Outcomes

Purpose: To report visual outcomes, microbiologic spectrum, and antibiotic resistance in endophthalmitis patients undergoing pars plana vitrectomy (PPV).Methods: Retrospective study of 32 patients who underwent PPV with microbial analysis. Linear mixed models were utilized to compare visual acuity (VA).Results: Streptococcal species and coagulase-negative staphylococcus (CoNS) were the most common organisms. No resistance to vancomycin or fluoroquinolones was observed. Culture-negative individuals had better VA and lower incidences of retinal detachment (RD) and hypotony and better VA than culture-positive group at post-surgical month 3 (p = .025) and marginally at month 12 (p = .098). CoNS endophthalmitis (final logMAR VA 0.80) was associated with better VA than Streptococcal endophthalmitis (final logMAR VA 2.36) (p = .001). Secondary RD was observed in 33.3% of non-cataract endophthalmitis.Conclusion: No organisms were resistant to vancomycin or fluoroquinolones. Culture-negative endophthalmitis had better VA and lower rates of RD and hypotony than culture-positive group. A high rate of RD was observed in non-cataract endophthalmitis.

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.

Therapeutic Effects of Intravitreously Administered Bacteriophage in a Mouse Model of Endophthalmitis Caused by Vancomycin-Sensitive or -Resistant Enterococcus faecalis

Endophthalmitis due to infection with Enterococcus spp. progresses rapidly and often results in substantial and irreversible vision loss. Given that the frequency of this condition caused by vancomycin-resistant Enterococcus faecalis has been increasing, the development of novel therapeutics is urgently required. We have demonstrated the therapeutic potential of bacteriophage ΦEF24C-P2 in a mouse model of endophthalmitis caused by vancomycin-sensitive (EF24) or vancomycin-resistant (VRE2) strains of E. faecalis Phage ΦEF24C-P2 induced rapid and pronounced bacterial lysis in turbidity reduction assays with EF24, VRE2, and clinical isolates derived from patients with E. faecalis-related postoperative endophthalmitis. Endophthalmitis was induced in mice by injection of EF24 or VRE2 (1 × 10⁴ cells) into the vitreous. The number of viable bacteria in the eye increased to >1 × 10⁷ CFU, and neutrophil infiltration into the eye was detected as an increase in myeloperoxidase activity at 24 h after infection. A clinical score based on loss of visibility of the fundus as well as the number of viable bacteria and the level of myeloperoxidase activity in the eye were all significantly decreased by intravitreous injection of ΦEF24C-P2 6 h after injection of EF24 or VRE2. Whereas histopathologic analysis revealed massive infiltration of inflammatory cells and retinal detachment in vehicle-treated eyes, the number of these cells was greatly reduced and retinal structural integrity was preserved in phage-treated eyes. Our results thus suggest that intravitreous phage therapy is a potential treatment for endophthalmitis caused by vancomycin-sensitive or -resistant strains of E. faecalis.

LysPBC2, a Novel Endolysin Harboring a Bacillus cereus Spore Binding Domain

To control the spore-forming human pathogen Bacillus cereus, we isolated and characterized a novel endolysin, LysPBC2, from a newly isolated B. cereus phage, PBC2. Compared to the narrow host range of phage PBC2, LysPBC2 showed very broad lytic activity against all Bacillus, Listeria, and Clostridium species tested. In addition to a catalytic domain and a cell wall binding domain, LysPBC2 has a spore binding domain (SBD) partially overlapping its catalytic domain, which specifically binds to B. cereus spores but not to vegetative cells of B. cereus Both immunogold electron microscopy and a binding assay indicated that the SBD binds the external region of the spore cortex layer. Several amino acid residues required for catalytic or spore binding activity of LysPBC2 were determined by mutagenesis studies. Interestingly, LysPBC2 derivatives with impaired spore binding activity showed an increased lytic activity against vegetative cells of B. cereus compared with that of wild-type LysPBC2. Further biochemical studies revealed that these LysPBC2 derivatives have lower thermal stability, suggesting a stabilizing role of SBD in LysPBC2 structure.IMPORTANCE Bacteriophages produce highly evolved lytic enzymes, called endolysins, to lyse peptidoglycan and release their progeny from bacterial cells. Due to their potent lytic activity and specificity, the use of endolysins has gained increasing attention as a natural alternative to antibiotics. Since most endolysins from Gram-positive-bacterium-infecting phages have a modular structure, understanding the function of each domain is crucial to make effective endolysin-based therapeutics. Here, we report the functional and biochemical characterization of a Bacillus cereus phage endolysin, LysPBC2, which has an unusual spore binding domain and a cell wall binding domain. A single point mutation in the spore binding domain greatly enhanced the lytic activity of endolysin at the cost of reduced thermostability. This work contributes to the understanding of the role of each domain in LysPBC2 and will provide insight for the rational design of efficient antimicrobials or diagnostic tools for controlling B. cereus.

Culture-Proven Endophthalmitis After Intravitreal Injection: A 10-Year Analysis

BACKGROUND AND OBJECTIVE

To report on the microbiology, management, and visual outcomes of intravitreal injection (IVI)-associated, culture-proven endophthalmitis.

PATIENTS AND METHODS

All patients seen at a tertiary referral center with culture-proven endophthalmitis associated with an IVI between June 2007 and July 2017 were included in this retrospective analysis.

RESULTS

Thirty-five patients with culture-positive endophthalmitis following IVI were identified. All gram-positive organisms (34 of 35) were susceptible to vancomycin. Cases due to pathogens associated with oral or respiratory flora were common (31.4%, n = 11), presented earlier (2.0 days vs. 4.6 days, P < .001), were more likely to undergo pars plana vitrectomy (81.8% vs. 25.0%, P = .002) and had worse visual acuity outcomes.

CONCLUSION

IVI-associated endophthalmitis pathogens and anti-microbial susceptibilities in the Pacific Northwest are similar to those reported from other geographic locations. Bacteria associated with the oral and respiratory flora are common isolates that result in a more aggressive course and worse visual outcomes. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:33-38.].

A Review of Antimicrobial Therapy for Infectious Uveitis of the Posterior Segment

Treatment of infectious posterior uveitis represents a therapeutic challenge for ophthalmologists. The eye is a privileged site, maintained by blood ocular barriers, which limits penetration of systemic antimicrobials into the posterior segment. In addition, topical and subconjunctival therapies are incapable of producing sufficient drug concentrations, intraocularly. Posterior infectious uveitis can be caused by bacteria, virus, fungi, or protozoa. Mode of treatment varies greatly based on the infectious etiology. Certain drugs have advantages over others in the treatment of infectious uveitis. Topical and systemic therapies are often employed in the treatment of ocular infection, yet the route of treatment can have limitations based on penetration, concentration, and duration. The introduction of intravitreal antimicrobial therapy has advanced the management of intraocular infections. Being able to bypass blood-ocular barriers allows high drug concentrations to be delivered directly to the posterior segment with minimal systemic absorption. However, because the difference between the therapeutic and the toxic doses of some antimicrobial drugs falls within a narrow concentration range, intravitreal therapy could be associated with ocular toxicity risks. In many cases of infectious uveitis, combination of intravitreal and systemic therapies are necessary. In this comprehensive review, the authors aimed at reviewing clinically relevant data regarding intraocular and systemic antimicrobial therapy for posterior segment infectious uveitis. The review also discussed the evolving trends in intraocular treatment, and elaborated on antibiotic pharmacokinetics and pharmacodynamics, efficacy, and adverse effects.

Ocular penetration of topically applied 1% tigecycline in a rabbit model

AIM

To evaluate ocular penetration of topically applied 1% tigecycline.

METHODS

Forty-two New Zealand White rabbits were divided into 3 groups. A 50 µL drop of 1% tigecycline was administered in group 1. In groups 2 and 3, the drop was administered every 15min for 60min (keratitis protocol). Aqueous humor samples in groups 1 and 2 were collected under general anesthesia at 15, 30, 45, 60, 120, and 180min after the last drop. All animals in group 3 were euthanatized. Cornea, vitreous and blood samples were collected 60 and 120min after the last drop. Tigecycline concentrations were measured using high performance liquid chromatography-mass spectrometry (LC-MS/MS).

RESULTS

The peak aqueous humor tigecycline concentration [mean 0.73±0.14 mg/L (SD) and 2.41±0.14 mg/L, respectively] occurred 45min after topical drug application in groups 1 and 2. Group 3 mean values in the cornea, and vitreous, were 3.27±0.50 µg/g, and 0.17±0.10 mg/L at 60min and 3.17±0.77 µg/g and 0.20±0.07 mg/L at 120min, respectively. Tigecycline serum concentrations were negligible.

CONCLUSION

Tigecycline levels in the aqueous humor in groups 1 and 2, and in the cornea in group 3 exceeded the minimum inhibitory concentrations of most gram-positive organisms that cause bacterial keratitis and endophthalmitis.

The Susceptibility of Bacterial Endophthalmitis Isolates to Vancomycin, Ceftazidime, and Amikacin: a 23 Year-Review

PURPOSE

To investigate the in vitro susceptibility of Gram-positive and Gram-negative endophthalmitis bacterial isolates to vancomycin, amikacin, and ceftazidime over a 23-year period.

DESIGN

Retrospective non-comparative laboratory case series.

SUBJECTS

Endophthalmitis patients that were culture positive for bacteria.

METHODS

Laboratory records of bacteria isolated from endophthalmitis specimens collected from January 1^st 1993 to December 31^st 2015 were reviewed for incidence and standard susceptibility testing.

MAIN OUTCOME MEASURES

The in vitro susceptibilities of bacteria cultured from endophthalmitis to vancomycin (VAN), amikacin (AMK), and ceftazidime (CEF).

RESULTS

Patients with endophthalmitis were culture positive for bacteria in 665 cases.. Coagulase negative Staphylococci (CoNS) were the most common bacteria (54.6%), followed by Streptococci (Strep) species (20.8%), Staphylococcus aureus (SA) (10.2%), other Gram-positive (other-GP) bacteria (7.4%) and Gram-negative (GN) bacteria (7.1%). All Gram-positive organisms were susceptible to VAN, with the exception of 2 isolates. The in vitro susceptibilities of bacteria to AMK were: CoNS (95.3%), SA (75.0%), Strep (8.0%), GN (95.7%), and other-GP (81.1%). The in vitro susceptibilities of bacteria to CEF were: CoNS (58.5%), SA (54.4%), Strep (84.1%), GN (93.6.%), and other-GP (52.8%). There was no difference between AMK (95.7%) and CEF (93.6%) for GN coverage. AMK provided better coverage than CEF for CoNS, SA, and other-GP bacteria respectively (p<0.05, Fisher's exact), however, CEF appeared to provide better coverage (p<0.001, Fisher's exact) for Strep than AMK.

CONCLUSIONS

Based on standard in vitro susceptibility testing, vancomycin remains an optimal antibiotic choice for the treatment of Gram-positive endophthalmitis. AMK and CEF appear to provide equal GN coverage, but AMK appears to provide better coverage for CoNS, SA, and other-GP, but not Strep.

Isolates and antibiotic susceptibilities of endophthalmitis in postcataract surgery: a 12-year review of culture-proven cases

The purpose of this study was to investigate the spectrum of organisms causing endophthalmitis after cataract surgery in a tertiary medical center in Taiwan and the antibiotic susceptibilities. This was a retrospective case series study. Patients with endophthalmitis after cataract surgery from January 2004 to July 2015 were reviewed. The outcome measures included the identification of isolates, antibiotic susceptibilities, and final visual outcomes. Twenty-one organisms were isolated from 19 cases. The most common organisms were Enterococcus in 38.1 %, especially Enterococcus faecalis, followed by Staphylococcus epidermidis in 28.6 % and Staphylococcus aureus in 9.5 %. All of the Gram-positive isolates tested were susceptible to vancomycin (100 %), and ceftazidime and amikacin were susceptible for Gram-negative organisms. The Gram-positive organisms remain to be the predominant cause of postoperative endophthalmitis, and Enterococcus species has had an increasing incidence. Vancomycin is still the most powerful antibiotic for Gram-positive organisms, while ceftazidime and amikacin are effective for Gram-negative bacteria.

Intravitreal Daptomycin for Recalcitrant Postoperative Endophthalmitis

Purpose

To report the first case to our knowledge of intravitreal daptomycin used to successfully treat culture-negative vancomycin resistant to exogenous endophthalmitis.

Methods

Case report with preoperative, intraoperative, and postoperative findings.

Results

A 63-year-old Caucasian male underwent routine pars plana vitrectomy with epiretinal membrane peeling. He developed acute postoperative endophthalmitis, and underwent vitreous tap and injection of intravitreal vancomycin/ceftazidime/dexamethasone. Gram stain showed Gram-positive cocci, but cultures were negative. His infection subsequently proved very recalcitrant and his treatment course involved pars plana vitrectomy with anterior chamber washout and repeat injection of antibiotics, followed by repeat intravitreal vancomycin and ceftazidime. Ultimately, a second vitrectomy with intravitreal daptomycin controlled his intraocular infection. On each occasion, cultures were negative.

Conclusion

This case suggests that vancomycin resistance should be considered in culture-negative postoperative endophthalmitis, and intravitreal daptomycin should be considered as an important treatment alternative. Although vancomycin resistance is fairly rare in endophthalmitis, acknowledgment of its increasing occurrence rate is critical for optimal management.

Endophthalmitis caused by Gram-positive organisms with reduced vancomycin susceptibility: literature review and options for treatment

BACKGROUND

Endophthalmitis caused by Gram-positive organisms with reduced vancomycin susceptibility and/or resistance is an important clinical issue worldwide.

PURPOSE

To review the published literature on endophthalmitis caused by Gram-positive organisms with reduced vancomycin susceptibility and/or vancomycin resistance.

METHODS

The data were analysed from a PubMed search of endophthalmitis cases caused by Gram-positive organisms with reported reduced vancomycin susceptibility and/or vancomycin resistance from 1990 to 2015.

RESULTS

From 18 publications identified, a total of 27 endophthalmitis cases caused by Gram-positive organisms with reduced vancomycin susceptibility and/or vancomycin resistance were identified. The aetiologies of endophthalmitis were exogenous in 19/27 cases (11 post-cataract surgery, 2 post-penetrating keratoplasty, 1 post-glaucoma surgery, 4 post-open globe injury, 1 post-intravitreal injection of ranibizumab), and endogenous in 4/24 cases; no details were available about the four remaining patients. The causative organisms included Enterococcus species (7/27), coagulase-negative staphylococci (4/27), Staphylococcus aureus (4/27), Bacillus species (4/27), Streptococcus species (3/27), Leuconostoc species (3/27), Staphylococcus hominis (1/27), and unidentified Gram-positive cocci (1/27). Visual acuity of 20/400 or better at the final follow-up was recorded in 10/26 patients (38.5%; data were not available for one patient). Treatment options include fluoroquinolones, penicillin, cephalosporins, tetracyclines, and oxazolidinones.

CONCLUSIONS

In the current study, visual acuity outcomes were generally poor. Enterococcus and Staphylococcus species were the most common organisms reported and postoperative endophthalmitis after cataract surgery was the most common clinical setting.

Endogenous endophthalmitis: diagnosis, management, and prognosis

Endogenous endophthalmitis is an ophthalmic emergency that can have severe sight-threatening complications. It is often a diagnostic challenge because it can manifest at any age and is associated with a number of underlying predisposing factors. Microorganisms associated with this condition vary along a broad spectrum. Depending upon the severity of the disease, both medical and surgical interventions may be employed. Due to rarity of the disease, there are no guidelines in literature for optimal management of these patients. In this review, treatment guidelines based on clinical data and microorganism profile have been proposed.

Ocular Infection: Endophthalmitis

Endophthalmitis is characterized by marked inflammation of intraocular fluids and tissues. Infective endophthalmitis may be categorized by the cause of the infection, which helps predict the underlying etiology and most likely causative organisms. The major category remains acute-onset postoperative endophthalmitis. Infective endophthalmitis is a clinical diagnosis but is confirmed by evaluation of intraocular fluid specimens. The Endophthalmitis Vitrectomy Study offered important guidelines for the initial management of endophthalmitis, and these guidelines remain relevant to this day. Prompt initiation of empiric broad-spectrum antimicrobial therapy is important in achieving best outcomes.

Bilateral endogenous endophthalmitis caused by vancomycin-resistant Staphylococcus epidermidis in a neonate

BACKGROUND

Neonatal bilateral endogenous endophthalmitis is rare and often results in devastating visual outcome.

FINDINGS

An 18-day-old neonate presented with whitening of the cornea in the left eye. The child was examined under anesthesia, and a diagnosis of bilateral endogenous endophthalmitis was made. Vitreous biopsy from the left eye showed no growth. Blood samples showed growth of Staphylococcus epidermidis which was multidrug resistant (including vancomycin) but sensitive to piperacillin-tazobactam. The patient was managed with bilateral intravitreal injections of piperacillin-tazobactam and systemic cefpodoxime. Systemic and topical antibiotics were given for 3 and 8 weeks, respectively, and infection was controlled. At 2-year follow-up, the right eye is fixing and following to light with clear view of the fundus and the left eye has a clear cornea with red glow of the fundus.

CONCLUSIONS

Vancomycin-resistant S. epidermidis may be a cause of endogenous endophthalmitis. Intravitreal piperacillin-tazobactam and systemic cefpodoxime were used to eliminate the infection in this neonate.

Susceptibility of bacterial isolates to vancomycin and ceftazidime from patients with endophthalmitis: Is there a need to change the empirical therapy in suspected bacterial endophthalmitis?

To review the susceptibility of bacterial isolates to ceftazidime and vancomycin isolated from patients with endophthalmitis. Microbiology records of patients with endophthalmitis between June 2010 and May 2013 were reviewed. Vitreous and AC fluids obtained from patients with endophthalmitis were subjected to direct microscopy examination and culture. Antibiotic susceptibility of the isolates was performed by Kirby Bauer disk diffusion method. Resistant to ceftazidime in Gram negative bacteria (GNB) by disk diffusion method is confirmed by minimum inhibitory concentration using E test. Culture was positive for bacteria/Fungi in 224/356 patients (62.9 %). Out of 224 patients, 191 (85.2 %) patients showed bacterial growth and 33 (14.0 %) showed fungal growth. Mixed bacterial infection was seen in five patients. Among the GNB, 23/123 (18 %) of the isolates were resistant to ceftazidime, and all the Gram positive bacteria 73/73 (100 %) were susceptible to vancomycin. Sixteen of 123 (13 %) GNB were resistant to amikacin. Although there is an increase in resistance to ceftazidime compared to amikacin in GNB, amikacin intravitreal injection is associated with macular toxicity and no single antibiotic has full coverage for all GNB. Combination of vancomycin and ceftazidime empiric therapy can be continued in patients with suspected endophthalmitis and treatment is modified based on clinical response and susceptibility results.

Endophthalmitis caused by Enterococcus faecalis: clinical features, antibiotic sensitivities, and outcomes

PURPOSE

To report the clinical features, antibiotic sensitivities, and visual acuity outcomes of endophthalmitis caused by Enterococcus faecalis.

STUDY DESIGN

Retrospective, observational case series.

METHODS

A consecutive case series of patients with culture-positive endophthalmitis caused by E. faecalis between January 1, 2002, and December 31, 2012, at an academic referral center.

RESULTS

Of 14 patients identified, clinical settings included bleb association (n = 8), occurrence after cataract surgery (n = 4), and occurrence after penetrating keratoplasty (n = 2). All isolates were vancomycin sensitive. When comparing isolates in the current study with isolates from 1990 through 2001, the minimal inhibitory concentration required to inhibit 90% of isolates increased for ciprofloxacin (4 μg/mL from 1 μg/mL), erythromycin (256 μg/mL from 4 μg/mL), and penicillin (8 μg/mL from 4 μg/mL), indicating higher levels of resistance. The minimal inhibitory concentration required to inhibit 90% of isolates remained the same for vancomycin (2 μg/mL) and linezolid (2 μg/mL). Presenting visual acuity ranged from hand movements to no light perception. Initial treatment strategies were vitreous tap and intravitreal antibiotic injection (n = 12) and pars plana vitrectomy with intravitreal antibiotic injection (n = 2). Visual acuity outcomes were 20/400 or worse in 13 (93%) of 14 patients.

CONCLUSIONS

Although all isolates were sensitive to vancomycin and linezolid, higher minimal inhibitory concentration required to inhibit 90% of isolates in the current study, compared with isolates from 1990 through 2001, occurred with ciprofloxacin, erythromycin, and penicillin. Despite prompt treatment, most patients had poor outcomes.

Update on the prevention and treatment of endophthalmitis

Endophthalmitis remains a rare but serious cause of visual loss. Over time, changes have been noted in endophthalmitis in terms of predominant causes, infecting organisms, and antibiotic susceptibilities. There is controversy regarding the use of intracameral prophylactic antimicrobials during cataract surgery. Alternatively, there appears to be increasing evidence against using routine topical antibiotics for intravitreal injections. There are also increasing reports of multidrug-resistant organisms causing endophthalmitis, but the combination of vancomycin and ceftazidime appears effective for the vast majority of cases. Future trends may involve increasing utilization of polymerase chain reaction for diagnosis, and possibly office-based pars plana vitrectomy for treatment of endophthalmitis.