A Systematic Review of Multi-decade Antibiotic Resistance Data for Ocular Bacterial Pathogens in the United States

Novel Anti-Microbial/Anti-Inflammatory Combination Improves Clinical Outcome of Bacillus cereus Endophthalmitis

Purpose

The purpose of this study was to explore the therapeutic potential of the novel combination of Bacillus bacteriophage lysin (PlyB) and a synthetic TLR2/4 inhibitor (oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, OxPAPC) in the treatment of experimental Bacillus cereus endophthalmitis.

Methods

C57BL/6J mice were injected with 100 colony forming units (CFUs) Bacillus cereus to induce endophthalmitis. Two hours postinfection, groups of mice were treated with either PlyB, PlyB with OxPAPC, or the groups were left untreated to serve as a control. A group of uninfected mice was injected with only PlyB to serve as a treatment control. Eight hours post-treatment, infected/treated mice were analyzed for bacterial counts, retinal function, histology, and inflammation.

Results

Groups treated with PlyB alone or PlyB/OxPAPC showed significantly reduced bacterial loads compared with untreated eyes. Compared with untreated eyes, PlyB and PlyB/OxPAPC-treated eyes retained significant A-wave and B-wave function. PlyB/OxPAPC-treated eyes retained greater A- and B-wave function compared with eyes treated with PlyB alone. Histology showed that retinal structures were well preserved, and retinal layers were distinguishable in eyes treated with PlyB and PlyB/OxPAPC. Ninety-five percent of infiltrating CD45+ cells in infected untreated eyes were Ly6G+/Ly6C+ neutrophils. Infected eyes treated with PlyB and PlyB/OxPAPC had significantly reduced numbers of CD45+ immune cells compared with untreated eyes. Eyes treated with PlyB/OxPAPC had a significantly lower number of neutrophils than eyes treated with PlyB alone.

Conclusions

These results demonstrated that the novel combination of bacteriophage lysin and TLR2/4 inhibitor was a successful treatment option for treating experimental Bacillus cereus endophthalmitis.

Synthetic lincosamides iboxamycin and cresomycin are active against ocular multidrug-resistant methicillin-resistant Staphylococcus aureus carrying erm genes

OBJECTIVE

Antimicrobial resistance is a global pandemic that poses a major threat to vision health as ocular bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA), are becoming increasingly resistant to first-line therapies. Here we evaluated the antimicrobial activity of new synthetic lincosamides in comparison to currently used antibiotics against clinical ocular MRSA isolates.

METHODS

Antimicrobial susceptibility testing was performed by broth microdilution for two novel synthetic lincosamides (iboxamycin and cresomycin) and eight comparator antibiotics against a collection of 50 genomically characterised ocular MRSA isolates, including isolates harbouring erm genes (n = 25).

RESULTS

Both drugs were active against widespread MRSA clonal complexes CC8 and CC5. The MIC50 and MIC90 of iboxamycin were 0.06 and 2 mg/L, respectively. Cresomycin (MIC50 = 0.06 mg/L) also displayed good activity with an in vitro potency four-fold higher (MIC90 = 0.5 mg/L) than iboxamycin. In isolates harbouring erm genes, MIC90 were >16, 2, and 0.5 mg/L for clindamycin, iboxamycin, and cresomycin, respectively. The in vitro potencies of iboxamycin and cresomycin were similar or higher than that of comparator agents and were not impacted by multidrug-resistance phenotypes or by the presence of erm genes when compared with clindamycin.

CONCLUSIONS

Our results demonstrate that iboxamycin and cresomycin display potent in vitro activity against ocular MRSA isolates, including multidrug-resistant isolates harbouring erm genes.

Microbiology and management of Staphylococcus aureus lacrimal system infections: A 10-year retrospective study

PURPOSE

To assess the in vitro efficacy of common antimicrobial agents used empirically for methicillin- resistant and sensitive Staphylococcus aureus (MRSA and MSSA) infections of the lacrimal system.

METHODS

A retrospective review of culture-proven S. aureus isolates retrieved from lacrimal system samples collected between January 2013-December 2022 was performed. Microbiologic characteristics such as in vitro susceptibility as well as clinical characteristics including history of recent ocular surgery, presence of lacrimal biomaterial implant, anti-microbial regimen, and treatments outcome were collected.

RESULTS

One hundred and sixteen S. aureus isolates (patients = 116) were identified. Thirty-one (27.4%) and 22 (19.5%) patients had recent ocular procedure and lacrimal intubation, respectively. Fifty (44.2%) patients received a combination of oral and topical antibiotics as first line of treatment. The most common empirically utilized antibiotics were β-lactams (38.9%) and polymyxin B/ trimethoprim (31.0%). The antibiotic regimen was changed at least once in 20.5% of patients due to ineffectiveness. Of the patients with positive cultures from the lacrimal excretory apparatus, 37.3% underwent surgery as part of the treatment approach. Of all isolates identified 44.8% were MRSA. Among the fluoroquinolones, the resistance rate was 38.8% for ciprofloxacin and 30.4% for moxifloxacin, with significantly higher resistance rates in MRSA (P-value <0.0001). The resistance rates for trimethoprim/sulfamethoxazole (TMP/SXT) and gentamicin were 8.6% and 3.4%, retrospectively.

CONCLUSIONS

There is low in vitro efficacy of commonly used antimicrobials such as β-lactams and fluoroquinolones in our study population; thus, we recommend opting for trimethoprim/sulfamethoxazole and gentamicin for systemic and topical single-agent treatments.

Adoption of a Tetrahedral DNA Nanostructure as a Multifunctional Biomaterial for Drug Delivery

DNA nanostructures have been widely researched in recent years as emerging biomedical materials for drug delivery, biosensing, and cancer therapy, in addition to their hereditary function. Multiple precisely designed single-strand DNAs can be fabricated into complex, three-dimensional DNA nanostructures through a simple self-assembly process. Among all of the synthetic DNA nanostructures, tetrahedral DNA nanostructures (TDNs) stand out as the most promising biomedical nanomaterial. TDNs possess the merits of structural stability, cell membrane permeability, and natural biocompatibility due to their compact structures and DNA origin. In addition to their inherent advantages, TDNs were shown to have great potential in delivering therapeutic agents through multiple functional modifications. As a multifunctional material, TDNs have enabled innovative pharmaceutical applications, including antimicrobial therapy, anticancer treatment, immune modulation, and cartilage regeneration. Given the rapid development of TDNs in the biomedical field, it is critical to understand how to successfully produce and fine-tune the properties of TDNs for specific therapeutic needs and clinical translation. This article provides insights into the synthesis and functionalization of TDNs and summarizes the approaches for TDN-based therapeutics delivery as well as their broad applications in the field of pharmaceutics and nanomedicine, challenges, and future directions.

Cefiderocol Is an Effective Topical Monotherapy for Experimental Extensively Drug-Resistant Pseudomonas aeruginosa Keratitis

Purpose

To test cefiderocol, a siderophore-cephalosporin antibiotic for topical monotherapy treatment of experimental extensively drug-resistant (XDR) Pseudomonas aeruginosa keratitis.

Design

Preclinical study.

Subjects and Controls

Deidentified P. aeruginosa keratitis isolates, XDR P. aeruginosa from eye drop outbreak, rabbits, saline, cefiderocol 50 mg/ml, ciprofloxacin 0.3%, and tobramycin 14 mg/ml.

Methods Intervention or Testing

Cefiderocol antibacterial activity against P. aeruginosa keratitis isolates (n = 135) was evaluated by minimum inhibitory concentration (MIC) testing. Ocular toxicity/tolerability and antibacterial efficacy were tested in vivo with experimental rabbit models. Corneal concentrations and stability were assessed using a bioassay.

Main Outcome Measures

Minimum inhibitory concentration analysis for susceptibility, graded tests for ocular toxicity/tolerability, colony-forming unit (CFU) analysis for bacterial burden, corneal cefiderocol concentrations.

Results

One hundred percent of P. aeruginosa keratitis isolates were susceptible to cefiderocol (n = 135), the MIC90 was 0.125 μg/ml including the XDR isolate (MIC = 0.125 μg/ml). Topical cefiderocol 50 mg/ml was minimally toxic to the ocular surface and was well tolerated. For the XDR P. aeruginosa isolate, topical cefiderocol 50 mg/ml, significantly decreased corneal CFU compared with ciprofloxacin 0.3%, tobramycin 14 mg/ml, and saline. In addition, tobramycin 14 mg/ml was more effective than the saline control. Mean cefiderocol corneal concentrations were 191× greater than the MIC90 of the P. aeruginosa keratitis isolates. Refrigerated cefiderocol maintained antimicrobial activity over a 1-month period.

Conclusions

These results demonstrate that cefiderocol is well tolerated on rabbit corneas and is effective against P. aeruginosa keratitis isolates in vitro and was effective in vivo against an XDR isolate in a rabbit keratitis model. Given the recent outbreak of keratitis caused by this XDR P. aeruginosa, cefiderocol is a promising additional antibiotic that should be further evaluated for topical treatment of keratitis caused by antibiotic resistant P. aeruginosa.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Topical Antiseptics in Minimizing Ocular Surface Bacterial Load Before Ophthalmic Surgery: A Randomized Controlled Trial

PURPOSE

To investigate the reduction of the ocular surface bacterial load induced by 2 commercially available ophthalmic antiseptic formulations, povidone-iodine (PVI) 0.6% and chlorhexidine (CLX) 0.02%, before ocular surgery.

DESIGN

Randomized controlled trial.

METHODS

Seventy adult patients undergoing intraocular surgery (phacoemulsification) were randomized to receive in the index eye PVI (group A) 4 times a day for 3 days or CLX (group B) 4 times a day for 3 days before surgery. The untreated eye was used as control. A conjunctival swab was taken in both eyes before (T0) and after (T1) therapy. Microbial DNA was quantified with real-time polymerase chain reaction (PCR) analysis. The Mick algorithm was used to compare the abundance of each genus/genera against the distribution of abundances from the reference. At T1, patients filled a questionnaire to evaluate therapy-induced symptoms. Primary outcome was the reduction of bacterial DNA at T1 (microbial load), vs control arm, expressed as mean number of real-time PCR cycle times (CTs). Secondary outcomes were taxonomic composition, differential abundance, and therapy-induced ocular symptoms.

RESULTS

The T0-T1 difference in CT was significant in group B, but not in group A (mean [95% CI], 0.99 [0.33] vs 0.26 [0.15], P < .001, and 0.65 [0.3] vs 0.45 [0.41], P = .09, respectively). The taxonomic composition, alpha, and beta diversity remained consistent at all time points in both groups. The rate of patients reporting therapy-induced ocular symptoms and the mean discomfort grade were greater in group A than in group B (97% vs 26% and 4.97±2.48 vs 0.66±1.53, respectively).

CONCLUSIONS

Compared with PVI 0.6%, CLX 0.02% induced a greater reduction of ocular surface bacterial load, with no significant alterations of the taxonomic composition. Moreover, CLX was better tolerated than PVI.

Mesenchymal stem cell-based adjunctive therapy for Pseudomonas aeruginosa-induced keratitis: A proof-of-concept in-vitro study

PURPOSE

Pseudomonas aeruginosa-induced keratitis is one of the most severe and challenging forms of corneal infection, owing to its associated intense inflammatory reactions leading to corneal necrosis and dense corneal scar with loss of vision. Since mesenchymal stem cells (MSCs) are reported to possess antimicrobial and immunomodulatory properties, they can be tested as an adjuvant treatment along with the antibiotics which are the current standard of care. This study aims to investigate the anti-bacterial and immunomodulatory roles of human bone marrow MSC-derived conditioned medium (MSC-CM) in P. aeruginosa-infected human corneal epithelial cells (HCECs) in vitro.

METHODS

The effect of MSC-CM on the growth of clinical isolates of P. aeruginosa was evaluated by colony-forming unit assay. The expression of inflammatory cytokines (IL-6 and TNF-α) and an antimicrobial peptide (Lipocalin 2) in lipopolysaccharide-treated MSCs and HCECs was analyzed through ELISA. Corneal epithelial repair following infection with P. aeruginosa was studied through scratch assay.

RESULTS

Compared to control (P. aeruginosa (5*105) incubated in DMEM (1 ml) at 37 °C for 16 h), MSC-CM significantly: i) inhibits the growth of P. aeruginosa (159*109 vs. 104*109 CFU/ml), ii) accelerates corneal epithelial repair following infection with P. aeruginosa (9% vs. 24% closure of the wounded area after 12 h of infection), and iii) downregulates the lipopolysaccharide-induced expression of IL-6, TNF-α and Lipocalin 2 in HCECs. A combination of MSC-CM with an antibiotic, Ciprofloxacin moderately regulated the expression of IL-6, TNF-α, and Lipocalin 2.

CONCLUSION

MSC-CM holds promise as an adjunctive therapeutic approach for P. aeruginosa-induced corneal epithelial damage.

Characterization of the resistome and predominant genetic lineages of Gram-positive bacteria causing keratitis

Bacterial keratitis is a vision-threatening infection mainly caused by Gram-positive bacteria (GPB). Antimicrobial therapy is commonly empirical using broad-spectrum agents with efficacy increasingly compromised by the emergence of antimicrobial resistance. We used a combination of phenotypic tests and genome sequencing to identify the predominant lineages of GPB causing keratitis and to characterize their antimicrobial resistance patterns. A total of 161 isolates, including Staphylococcus aureus (n = 86), coagulase-negative staphylococci (CoNS; n = 34), Streptococcus spp. (n = 34), and Enterococcus faecalis (n = 7), were included. The population of S. aureus isolates consisted mainly of clonal complex 5 (CC5) (30.2%). Similarly, the population of Staphylococcus epidermidis was homogenous with most of them belonging to CC2 (78.3%). Conversely, the genetic population of Streptococcus pneumoniae was highly diverse. Resistance to first-line antibiotics was common among staphylococci, especially among CC5 S. aureus. Methicillin-resistant S. aureus was commonly resistant to fluoroquinolones and azithromycin (78.6%) and tobramycin (57%). One-third of the CoNS were resistant to fluoroquinolones and 53% to azithromycin. Macrolide resistance was commonly caused by erm genes in S. aureus, mphC and msrA in CoNS, and mefA and msr(D) in streptococci. Aminoglycoside resistance in staphylococci was mainly associated with genes commonly found in mobile genetic elements and that encode for nucleotidyltransferases like ant(4')-Ib and ant(9)-Ia. Fluroquinolone-resistant staphylococci carried from 1 to 4 quinolone resistance-determining region mutations, mainly in the gyrA and parC genes. We found that GPB causing keratitis are associated with strains commonly resistant to first-line topical therapies, especially staphylococcal isolates that are frequently multidrug-resistant and associated with major hospital-adapted epidemic lineages.

New Approaches to Overcoming Antimicrobial Resistance in Endophthalmitis

Endophthalmitis is a rare but vision-threatening infection characterized by marked inflammation of intraocular fluids and tissues, uncommonly seen following surgery and intravitreal injection. Antimicrobials are used worldwide in the prophylaxis and treatment of bacterial and fungal infections of the eye and are standard treatment in the preoperative and postoperative care of surgical patients. However, antimicrobials are reported to be overprescribed in many parts of the world, which contributes to antimicrobial resistance (AMR). AMR complicates the prophylaxis and treatment of endophthalmitis. This article examines the prevalence and mechanisms of AMR in ocular microorganisms, emphasizing the importance of understanding AMR patterns for tailored treatments. It also explores prophylaxis and management strategies for endophthalmitis, with a discussion on the use of intracameral antibiotic administration. The use of prophylactic intracameral antibiotics during cataract surgery is common in many parts of the world but is still controversial in some locations, especially in the US. Finally, it highlights the role of stewardship in ophthalmology and its benefits in the treatment of endophthalmitis.

Microbiological isolates and associated complications of dacryocystitis and canaliculitis in a prominent tertiary ophthalmic teaching hospital in northern China

BACKGROUND

To report the microbiological isolates, aetiology, complications, antibiotic susceptibilities, and clinical remission of dacryocystitis and canaliculitis in a prominent tertiary ophthalmic teaching and referral hospital located in northern China and to offer appropriate recommendations for preventing and formulating drug treatment strategies.

METHODS

This prospective study recruited a total of 477 participants who had been diagnosed with either dacryocystitis or canaliculitis. The cohort comprised 307 patients with chronic dacryocystitis, 111 patients with acute dacryocystitis, and 59 patients with canaliculitis. Purulent discharge from the lacrimal duct was collected using a sterile swab and immediately subjected to microbial culture. Antimicrobial susceptibility testing was conducted following established protocols. All participants were scheduled for follow-up visits within 14 days after receiving antibiotic therapy.

RESULTS

The present findings indicated that women exhibited a higher susceptibility to the condition, as evidenced by the occurrence of 367 cases in comparison to 110 cases among men. Among the 477 patients, definitive causes were established in 59 individuals, accounting for 12.4% of the patients. Additionally, ocular complications were reported by 132 patients, representing 27.7% of the total. Monocular involvement was observed in the majority of cases, with 402 out of 477 patients (84.3%) affected, while binocular involvement was present in 75 patients (15.7%). In total, 506 microbiological strains were recovered from 552 eyes, with Staphylococcus epidermidis (16.4%) being the most prevalent microorganism. Other predominant isolates included Corynebacterium macginleyi (9.1%), Staphylococcus aureus (5.1%), Streptococcus pneumoniae (4.9%), Haemophilus (4.4%), Propionibacterium acnes (3.5%), and Eikenella corrodens (3.1%). Among the 12 isolated fungi, Candida parapsilosis accounted for 66.7%. The susceptibility to antimicrobial agents tested in gram-negative bacilli (79.5%) was observed to be higher than that of anaerobic bacteria (76.7%) and gram-positive cocci (55.4%). With pharmacological therapy, the remission rate of acute dacryocystitis (72.7%) was found to be higher than that of canaliculitis (53.3%) and chronic dacryocystitis (42.3%).

CONCLUSIONS

This study highlights the microbial spectrum of dacryocystitis and canaliculitis, particularly C.macginleyi, E.corrodens and C.parapsilosis, which are also more frequently isolated. Vancomycin and imipenem may be more effective treatment options. Most cases have an unknown aetiology, and essential preventive measures involve postoperative cleansing of the lacrimal passage following eye and nasal surgeries, as well as the proactive management of rhinitis.

Abietic Acid as a Novel Agent against Ocular Biofilms: An In Vitro and Preliminary In Vivo Investigation

Biofilm-related ocular infections can lead to vision loss and are difficult to treat with antibiotics due to challenges with application and increasing microbial resistance. In turn, the design and testing of new synthetic drugs is a time- and cost-consuming process. Therefore, in this work, for the first time, we assessed the in vitro efficacy of the plant-based abietic acid molecule, both alone and when introduced to a polymeric cellulose carrier, against biofilms formed by Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans in standard laboratory settings as well as in a self-designed setting using the topologically challenging surface of the artificial eye. These analyses were performed using the standard microdilution method, the biofilm-oriented antiseptic test (BOAT), a modified disk-diffusion method, and eyeball models. Additionally, we assessed the cytotoxicity of abietic acid against eukaryotic cell lines and its anti-staphylococcal efficacy in an in vivo model using Galleria mellonella larvae. We found that abietic acid was more effective against Staphylococcus than Pseudomonas (from two to four times, depending on the test applied) and that it was generally more effective against the tested bacteria (up to four times) than against the fungus C. albicans at concentrations non-cytotoxic to the eukaryotic cell lines and to G. mellonella (256 and 512 µg/mL, respectively). In the in vivo infection model, abietic acid effectively prevented the spread of staphylococcus throughout the larvae organisms, decreasing their lethality by up to 50%. These initial results obtained indicate promising features of abietic acid, which may potentially be applied to treat ocular infections caused by pathogenic biofilms, with higher efficiency manifested against bacterial than fungal biofilms.

Antibiotic resistance of bacterial pathogens isolated from the conjunctiva in the Antibiotic Resistance Monitoring in Ocular micRoorganisms (ARMOR) surveillance study (2009-2021)

Antibiotic resistance in bacterial ocular infections is of significant clinical concern and may affect treatment outcomes. We report on in vitro antibiotic susceptibility rates and trends among conjunctival-sourced isolates collected in the Antibiotic Resistance Monitoring in Ocular micRoorganisms (ARMOR) surveillance study. A total of 2214 conjunctival isolates (918 Staphylococcus aureus, 589 coagulase-negative staphylococci [CoNS], 194 Streptococcus pneumoniae, 171 Pseudomonas aeruginosa, and 342 Haemophilus influenzae) obtained between 2009-2021 were analyzed. Staphylococci were commonly resistant to azithromycin (≥54.8%) and oxacillin (≥29.3%). Resistance among S. pneumoniae isolates was notable for azithromycin (34.0%) and penicillin (28.9%), while P. aeruginosa and H. influenzae isolates were highly susceptible to most tested antibiotics. Methicillin-resistant staphylococci demonstrated greater concurrent resistance to other antibiotics than methicillin-susceptible isolates and exhibited high rates of multidrug resistance (≥74.0%). Among staphylococci, antibiotic resistance increased with patient age, and there were small decreases in resistance to several drugs over the 13-year period. These findings indicate that resistance to antibiotics routinely used in ophthalmic practice remains high among conjunctival isolates.

Innovative cold atmospheric plasma (iCAP) decreases corneal ulcer formation and bacterial loads and improves anterior chamber health in methicillin resistant Staphylococcus aureus keratitis

Bacterial keratitis is a vision-threatening infection of the cornea that is typically treated with antibiotics. However, antibiotics sometimes fail to eradicate the infection and do not prevent or repair the damage caused directly by the bacteria or the host immune response to the infection. Our group previously demonstrated that treatment of Pseudomonas aeruginosa keratitis in rabbits with innovative cold atmospheric plasma (iCAP) resulted in reduced edema, ulcer formation, and bacterial load. In this study, we investigated the efficacy of iCAP treatment in methicillin-resistant Staphylococcus aureus (MRSA). New Zealand white rabbits were infected intrastromally with MRSA then treated with iCAP, moxifloxacin, vancomycin, or combination of iCAP with each antibiotic to assess the safety and efficacy of iCAP treatment compared to untreated controls and antibiotics. iCAP treatment significantly reduced bacterial loads and inflammation, improved anterior chamber clarity, and prevented corneal ulceration compared to untreated controls and antibiotic treatment. Safety assessments of grimace test scores and tear production showed that iCAP was not significantly different from either antibiotic treatment in terms of distress or tear production. Combination iCAP/antibiotic treatment did not appear to provide significant added benefit over iCAP alone. Our findings suggest that the addition of iCAP may be a viable tool in reducing damage to the cornea and anterior chamber of the eye following S. aureus keratitis.

Susceptibility of Ocular Surface Bacteria to Various Antibiotic Agents in a Romanian Ophthalmology Clinic

Periodic assessment of bacterial contamination is necessary as it allows proper guidance in cases of eye infections through the use of appropriate antibiotics. Due to the extensive use of antibiotic treatment, many strains of the microbiota that cause infections are resistant to the usual ophthalmic antibiotics. The present study provides an updated assessment of the susceptibility of Gram-positive and Gram-negative bacteria found on the ocular surface to the most commonly used antibiotic agents in patients undergoing cataract surgery. A total of 993 patients were included in the study with ages between 44 and 98 years old. Conjunctival cultures were collected 7 days before cataract surgery. The response of Gram-positive and Gram-negative bacteria to various antibiotic classes, such as glycopeptides, cephalosporins, carbapenems, fluoroquinolones, aminoglycosides, phenicols, tetracyclines, rifamycins, macrolides and penicillins, was assessed. From the tested antibiotics, vancomycin had 97.8% efficacy on Gram-positive bacteria. In the cephalosporin category, we observed a high level of resistance of the cefuroxime for both Gram-positive and negative bacteria. Antibiotics that have more than 90% efficacy on Gram-positive bacteria are meropenem, imipenem, netilmicin, amikacin and rifampicin. On Gram-negative bacteria, we found 100% efficacy of all tested fluoroquinolones, i.e., aminoglycosides (except for tobramycin), doxycycline, azithromycin, clarithromycin and chloramphenicol. The current study illustrates patterns of increased resistance in certain bacteria present on the ocular surface to some of the commonly used antibiotics in ophthalmological clinical practice. One such revealing example is cefuroxime, which has been highly used as an intracameral antibiotic for the prevention of bacterial endophthalmitis after cataract surgery.

Epidemiological and microbiological profiles of microbial keratitis in a tertiary eye center in Eastern India (Bihar)

Purpose

To determine the demography, risk factors, and causative organisms of microbial keratitis (MK) in Bihar, an eastern state of India.

Design

Retrospective study.

Methods

We reviewed the demographic, clinical, and microbiological data of 2303 patients with MK (non-viral) presenting between January 2019 and December 2022.

Results

This study revealed a predominance of males (65.0%) compared to females (34.9%), with a mean age of 48.4 ± 16.5 years. The majority of patients (63.1%) presented after 2 weeks from the onset of symptoms. The most common risk factor observed was corneal injury (58.1%), followed by ocular surface diseases (13.6%) and diabetes mellitus (13.3%). The majority of patients (73.16%) were involved in agriculture. Prior to presentation, almost all patients (92%) had received topical antibiotics. Unsupervised use of topical corticosteroids was observed in 29.2% of the patients for the median duration of 3 days (odds ratio, 0.17). At presentation, the median size of corneal ulcers was 5 mm, the best-corrected visual acuity was less than 20/400 in 51.4% of patients, and corneal perforation was in 14% of patients. The smear and culture positivity rate were 75.4% and 47.9%, respectively. The common causative organism was fungus (48.8%), followed by bacteria (17.4%). Aspergillus spp. and Staphylococcus spp. were the most commonly identified organisms; a quarter of the patients (24.5%) remained unidentified. All bacteria showed good sensitivity to vancomycin.

Conclusion

MK is a significant cause of ocular morbidity in Bihar. The knowledge of epidemiology, risk factors, and microbiological profiles of MK can provide a valuable approach to disease prevention, diagnosis, and management.

Microbiology of Eye Infections at the Massachusetts Eye and Ear: An 8-Year Retrospective Review Combined With Genomic Epidemiology

PURPOSE

Ocular bacterial infections are important causes of morbidity and vision loss. Early antimicrobial therapy is necessary to save vision, but their efficacy is increasingly compromised by antimicrobial resistance (AMR). We assessed the etiology of ocular bacterial infections seen at Massachusetts Eye and Ear and investigated the molecular epidemiology and AMR profiles of contemporary isolates.

DESIGN

Laboratory investigation.

METHODS

We used a combination of phenotypic tests and genome sequencing to identify the predominant lineages of leading ocular pathogens and their AMR profiles.

RESULTS

A total of 1601 isolates were collected from 2014 to 2021, with Staphylococcus aureus (n = 621), coagulase-negative staphylococci (CoNS) (n = 234), Pseudomonas aeruginosa (n = 213), Enterobacteriaceae (n = 167), and Streptococcus pneumoniae (n = 95) being the most common. Resistance was high among staphylococci, with methicillin resistance (MR) detected in 28% of S aureus and 39.8% of CoNS isolates. Multidrug resistance (MDR) was frequent among MR staphylococci (MRSA 60%, MRCoNS 76.1%). The population of S aureus isolates consisted mainly of 2 clonal complexes (CCs): CC8 (26.1%) and CC5 (24.1%). CC5 strains carried a variety of AMR markers, resulting in high levels of resistance to first-line therapies. Similarly, the population of ocular Staphylococcus epidermidis was homogenous with most belonging to CC2 (85%), which were commonly MDR (48%). Conversely, ocular S pneumoniae, P aeruginosa, and Enterobacteriaceae were often susceptible to first-line therapies and grouped into highly diverse genetic populations.

CONCLUSION

Our data showed that ocular bacterial infections in our patient population are disproportionately caused by strains that are resistant to clinically relevant antibiotics and are associated with major epidemic genotypes with both community and hospital associations.

A rise in the frequency of lasR mutant Pseudomonas aeruginosa among keratitis isolates between 1993 and 2021

Introduction

Pseudomonas aeruginosa causes vision threatening keratitis. The LasR transcription factor regulates virulence factors in response to the quorum sensing molecule N-3-oxo-dodecanoyl-L-homoserine lactone. P. aeruginosa isolates with lasR mutations are characterized by an iridescent high sheen phenotype caused by a build-up of 2-heptyl-4-quinolone. A previous study demonstrated 22% (n=101) of P. aeruginosa keratitis isolates from India between 2010 and 2016 were sheen positive lasR mutants, and the sheen phenotype correlated with worse clinical outcomes for patients. In this study, a longitudinal collection of P. aeruginosa keratitis isolates from Eastern North America were screened for lasR mutations by the sheen phenotype and sequencing of the lasR gene.

Methods

Keratitis isolates (n=399) were classified by sheen phenotype. The lasR gene was cloned from a subset of isolates, sequenced, and tested for loss of function or dominant-negative status based on an azocasein protease assay. A retrospective chart review compared outcomes of keratitis patients infected by sheen positive and negative isolates.

Results

A significant increase in sheen positive isolates was observed between 1993 and 2021. Extracellular protease activity was reduced among the sheen positive isolates and a defined lasR mutant. Cloned lasR alleles from the sheen positive isolates were loss of function or dominant negative and differed in sequence from previously reported ocular lasR mutant alleles. Retrospective analysis of patient information suggested significantly better visual outcomes for patients infected by sheen positive isolates.

Discussion

These results indicate an increase in lasR mutations among keratitis isolates in the United States and suggest that endemic lasR mutants can cause keratitis.

Ozonated Oil in Liposome Eyedrops Reduces the Formation of Biofilm, Selection of Antibiotic-Resistant Bacteria, and Adhesion of Bacteria to Human Corneal Cells

The recent attention to the risk of potential permanent eye damage triggered by ocular infections has been leading to a deeper investigation of the current antimicrobials. An antimicrobial agent used in ophthalmology should possess the following characteristics: a broad antimicrobial spectrum, prompt action even in the presence of organic matter, and nontoxicity. The objective of this study is to compare the antimicrobial efficacy of widely used ophthalmic antiseptics containing povidone-iodine, chlorhexidine, and liposomes containing ozonated sunflower oil. We determined the minimum inhibitory concentration (MIC) on various microbial strains: Staphylococcus aureus (ATCC 6538), methicillin-resistant Staphylococcus aureus (ATCC 33591), Staphylococcus epidermidis (ATCC 12228), Pseudomonas aeruginosa (ATCC 9027), and Escherichia coli (ATCC 873). Furthermore, we assessed its efficacy in controlling antibiotic resistance, biofilm formation, and bacterial adhesion. All three antiseptic ophthalmic preparations showed significant anti-microbicidal and anti-biofilm activity, with the liposomes containing ozonated sunflower oil with the highest ability to control antibiotic resistance and bacteria adhesion to human corneal cells.

Cefiderocol is an effective topical monotherapy for experimental extensively-drug resistant Pseudomonas aeruginosa keratitis

Purpose

To test cefiderocol, a siderophore-cephalosporin antibiotic for topical monotherapy treatment of experimental extensively drug resistant (XDR) Pseudomonas aeruginosa keratitis.

Design

Preclinical study.

Subjects and Controls

Deidentified P. aeruginosa keratitis isolates, XDR P. aeruginosa from eye drop outbreak, rabbits, saline, cefiderocol 50 mg/ml, ciprofloxacin 0.3%, and tobramycin 14 mg/ml.

Methods Intervention or Testing

Cefiderocol antibacterial activity against P. aeruginosa keratitis isolates (n=135) was evaluated by minimum inhibitory concentration (MIC) testing. Ocular toxicity/tolerability and antibacterial efficacy were tested in vivo with experimental rabbit models. Corneal concentrations and stability were assessed using a bioassay.

Main Outcome Measures

MIC analysis for susceptibility, graded tests for ocular toxicity/tolerability, CFU analysis for bacterial burden, corneal cefiderocol concentrations.

Results

100% of P. aeruginosa keratitis isolates were susceptible to cefiderocol (n=135), the MIC90 was 0.125 μg/ml including the XDR isolate (MIC = 0.125 μg/ml). Topical cefiderocol 50 mg/ml was minimally toxic to the ocular surface and was well tolerated. For the XDR P. aeruginosa isolate, topical cefiderocol 50 mg/ml, significantly decreased corneal CFU compared to ciprofloxacin 0.3%, tobramycin 14 mg/ml, and saline. In addition, tobramycin 14 mg/ml was more effective than the saline control. Mean cefiderocol corneal concentrations were 191x greater than the MIC90 of the P. aeruginosa keratitis isolates. Refrigerated cefiderocol maintained antimicrobial activity over a one-month period.

Conclusions

These results demonstrate that cefiderocol is well tolerated on rabbit corneas and is effective against P. aeruginosa keratitis isolates in vitro and was effective in vivo against an XDR isolate in a rabbit keratitis model. Given the recent outbreak of keratitis caused by this XDR P. aeruginosa, cefiderocol is a promising additional antibiotic that should be further evaluated for topical treatment of keratitis caused by antibiotic resistant P. aeruginosa.

Rise in frequency of lasR mutant Pseudomonas aeruginosa among keratitis isolates between 1993 and 2021

Pseudomonas aeruginosa causes severe vision threatening keratitis. LasR is a transcription factor that regulates virulence associated genes in response to the quorum sensing molecule N-3-oxo-dodecanoyl-L-homoserine lactone. P. aeruginosa isolates with lasR mutations are characterized by an iridescent high sheen phenotype caused by a build-up of 2-heptyl-4-quinolone. A previous study indicated a high proportion (22 out of 101) of P. aeruginosa keratitis isolates from India between 2010 and 2016 were sheen positive and had mutations in the lasR gene, and the sheen phenotype correlated with worse clinical outcomes for patients. In this study, a longitudinal collection of P. aeruginosa keratitis isolates from Eastern North America were screened for lasR mutations by the sheen phenotype and sequencing of the lasR gene. A significant increase in the frequency of isolates with the sheen positive phenotype was observed in isolates between 1993 and 2021. Extracellular protease activity was lower among the sheen positive isolates and a defined lasR mutant. Cloned lasR alleles from the sheen positive isolates were loss of function or dominant negative and differed in sequence from previously reported ocular lasR mutant alleles. Insertion elements were present in a subset of independent isolates and may represent an endemic source from some of the isolates. Retrospective analysis of patient information suggested significantly better visual outcomes for patients with infected by sheen positive isolates. Together, these results indicate an increasing trend towards lasR mutations among keratitis isolates at a tertiary eye care hospital in the United States.

Severe problem of macrolides resistance to common pathogens in China

With the widespread use of macrolide antibiotics in China, common pathogens causing children's infections, such as Streptococcus pneumoniae, Streptococcus (including Group A streptococcus, Group B streptococcus), Staphylococcus aureus, Bordetella pertussis, and Mycoplasma pneumoniae, have shown varying degrees of drug resistance. In order to provide such problem and related evidence for rational use of antibiotics in clinic, we reviewed the drug resistance of common bacteria to macrolides in children recent 20 years.

The Current Progress of Tetrahedral DNA Nanostructure for Antibacterial Application and Bone Tissue Regeneration

Recently, programmable assembly technologies have enabled the application of DNA in the creation of new nanomaterials with unprecedented functionality. One of the most common DNA nanostructures is the tetrahedral DNA nanostructure (TDN), which has attracted great interest worldwide due to its high stability, simple assembly procedure, high predictability, perfect programmability, and excellent biocompatibility. The unique spatial structure of TDN allows it to penetrate cell membranes in abundance and regulate cellular biological properties as a natural genetic material. Previous studies have demonstrated that TDNs can regulate various cellular biological properties, including promoting cells proliferation, migration and differentiation, inhibiting cells apoptosis, as well as possessing anti-inflammation and immunomodulatory capabilities. Furthermore, functional molecules can be easily modified at the vertices of DNA tetrahedron, DNA double helix structure, DNA tetrahedral arms or DNA tetrahedral cage structure, enabling TDN to be used as a nanocarrier for a variety of biological applications, including targeted therapies, molecular diagnosis, biosensing, antibacterial treatment, antitumor strategies, and tissue regeneration. In this review, we mainly focus on the current progress of TDN-based nanomaterials for antimicrobial applications, bone and cartilage tissue repair and regeneration. The synthesis and characterization of TDN, as well as the biological merits are introduced. In addition, the challenges and prospects of TDN-based nanomaterials are also discussed.

An All-in-One Highly Multiplexed Diagnostic Assay for Rapid, Sensitive, and Comprehensive Detection of Intraocular Pathogens

PURPOSE

Intraocular infections are sight-threatening conditions that can lead to vision loss. Rapid identification of the etiologies plays a key role in early initiation of effective therapy to save vision. However, current diagnostic modalities are time consuming and lack sensitivity and inclusiveness. We present here a newly developed comprehensive ocular panel designed to improve diagnostic yields and provide a tool for rapid and sensitive pathogen detection.

DESIGN

Experimental laboratory investigation.

METHODS

A panel containing 46 pathogens and 2 resistance/virulence markers that are commonly detected in intraocular infections was developed. Genomic targets were scrutinized for stretches predicted to be specific for a particular species while being conserved across different strains. A set of primers for sample enrichment, and two 50mer NanoString compatible probes were then designed for each target. Probe-target hybrids were detected and quantified using the NanoString nCounter SPRINT Profiler. Diagnostic feasibility was assessed in a pilot clinical study testing samples from infectious retinitis (n = 15) and endophthalmitis (n = 12) patients, for which the etiologies were confirmed by polymerase chain reaction (PCR) or culture.

RESULTS

Analytical studies demonstrated highly sensitive detection of a broad spectrum of pathogens, including bacteria, viruses, and parasites, with limits of detection being as low as 2.5 femtograms per reaction. We also found excellent target specificity, with minimal cross-reactivity detected. The custom-designed NanoString ocular panel correctly identified the causative agent from all clinical specimens positive for a variety of pathogens.

CONCLUSION

This highly multiplexed panel for pathogen detection offers a sensitive, comprehensive, and uniform assay run directly on ocular fluids that could significantly improve diagnostics of sight-threatening intraocular infections.

Comparative In Vitro Activity of New Lipoglycopeptides and Vancomycin Against Ocular Staphylococci and Their Toxicity on the Human Corneal Epithelium

PURPOSE

The purpose of this study was to assess the potential of new lipoglycopeptides as novel topical therapies for improved treatment of recalcitrant ocular infections. We evaluated the in vitro antimicrobial activity of oritavancin, dalbavancin, and telavancin compared with vancomycin (VAN) against a large collection of ocular staphylococcal isolates and their cytotoxicity on human corneal epithelial cells (HCECs).

METHODS

Antimicrobial susceptibility testing was performed by broth microdilution against 223 Staphylococcus spp. clinical isolates. Time-kill kinetics were determined for methicillin-resistant strains of Staphylococcus aureus (MRSA) (n = 2) and Staphylococcus epidermidis (MRSE) (n = 1). In vitro cytotoxicity assays were performed with AlamarBlue and live/dead staining on HCECs.

RESULTS

All new lipoglycopeptides showed strong in vitro potency against ocular staphylococci, including multidrug-resistant MRSA strains, with dalbavancin showing a slightly higher potency overall [minimum inhibitory concentration (MIC) 90 0.06 μg/mL] compared with telavancin and oritavancin (MIC 90 0.12 μg/mL), whereas VAN had the lowest potency (MIC 90 2 μg/mL). Oritavancin exerted rapid bactericidal activity within 1 h for MRSA and 2 h for MRSE. All other drugs were bactericidal within 24 h. At a concentration commonly used for topical preparations (25 mg/mL), cytotoxicity was observed for VAN after 5 min of incubation, whereas reduction in HCEC viability was not seen for telavancin and was less affected by oritavancin and dalbavancin. Cytotoxicity at 25 mg/mL was seen for all drugs at 30 and 60 min but was significantly reduced or undetected for lower concentrations.

CONCLUSIONS

Our study demonstrates that new lipoglycopeptides have substantially better in vitro antimicrobial activity against ocular staphylococcal isolates compared with VAN, with a similar or improved toxicity profile on HCECs.

Antimicrobial activity of a new class of synthetic retinoid antibiotics and comparator agents against ocular staphylococci

Objectives

Antimicrobial resistance is global pandemic that poses a major threat to vision health as ocular pathogens, especially staphylococcal species, are becoming increasingly resistant to first-line therapies. Here we evaluated the antimicrobial activity of a new class of synthetic retinoids in comparison to currently used antibiotics against clinically relevant ocular staphylococcal isolates.

Methods

Antimicrobial susceptibility testing was performed by broth microdilution for 3 novel synthetic retinoids (CD1530, CD437, and a CD437 analogue) and 7 comparator antibiotics, against a collection of 216 clinical isolates.

Results

CD437 MIC50 and MIC90 were 2 µg/mL for Staphylococcus aureus, and 1 µg/mL and 2 µg/mL respectively, for coagulase-negative staphylococci (CoNS). CD1530 (MIC50 = 2 µg/mL for all species) also displayed good activity with an in vitro potency slightly lower (2-fold) for S. aureus (MIC90 = 4 µg/mL) when compared to CD437. A CD437 analogue also demonstrated good in vitro activity (MIC50 = 2 µg/mL for all species) and potency (MIC90 = 2 µg/mL for MRSA and 4 µg/mL for MSSA and CoNS). In vitro potencies were similar or higher than that of comparator agents, and were not impacted by multidrug resistance phenotypes.

Conclusion

Our results demonstrate that synthetic retinoids display potent in vitro activity against ocular staphylococcal species, including multidrug-resistant isolates.

Trends in the Microbiological Spectrum of Nonviral Keratitis at a Single Tertiary Care Ophthalmic Hospital in India: A Review of 30 years

PURPOSE

The aims of this study were to assess the trends in microorganisms from patients with infectious keratitis and to assess their antibiogram patterns at a tertiary eye care center in India.

METHODS

In this retrospective observational case series, microbiological records of all corneal ulcers were reviewed from 1991 to 2020 and assessed for trends in keratitis and antibiotic susceptibility using the χ2 test.

RESULTS

Of the total of 51,747 patients, 51.13% were culture positive. A decrease in bacteria was noted from 56% to 38%, with a parallel increase in fungal isolates from 24% to 51%. Gram-positive bacteria accounted for 70.8% of the total bacteria, a trend in rise of Streptococcus pneumoniae (31%) and a decreasing trend in prevalence of Staphylococcus epidermidis was observed over 30 years. Pseudomonas aeruginosa (55.5%) was the most prevalent gram-negative pathogen, whereas Fusarium spp. (33.1%) and Aspergillus spp. (32.4%) were the most common fungal isolates. The susceptibility of gram-positive organisms to cefazolin decreased from 95.5% to 66% (P = 0.0001), amikacin from 88% to 55% (P= 0.0001), and vancomycin from 98.9% to 90.7% (P < 0.05). A similar decrease in susceptibility was also significant for gram-negative organisms with piperacillin/tazobactam and chloramphenicol (P < 0.05). A significant trend toward increasing resistance against fluoroquinolones was also observed for ciprofloxacin (gram-positive organisms: 16% to 50%; gram-negative organisms: 11.5% to 18.7%), gatifloxacin (38% to 47%), and moxifloxacin (9.4% to 29%).

CONCLUSIONS

The spectrum of keratitis has changed, and fungus is now the predominant etiology. An increasing trend in resistance to all antibiotics studied would affect the empiric treatment, also suggesting regular surveillance.

Research Progress and Potential Applications of Spermidine in Ocular Diseases

Spermidine, a natural polyamine, exists in almost all human tissues, exhibiting broad properties like anti-aging, autophagy induction, anti-inflammation, anti-oxidation, cell proliferation activation, and ion channel regulation. Considering that spermidine is already present in human nutrition, recent studies targeting supplementing exogenous sources of this polyamine appear feasible. The protective role of spermidine in various systems has been illuminated in the literature, while recent progress of spermidine administration in ocular diseases remains to be clarified. This study shows the current landscape of studies on spermidine and its potential to become a promising therapeutic agent to treat ocular diseases: glaucoma, optic nerve injury, age-related macular degeneration (AMD), cataracts, dry eye syndrome, and bacterial keratitis. It also has the potential to become a potent biomarker to predict keratoconus (KC), cataracts, uveitis, glaucoma, proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and retinopathy of prematurity (ROP). We also summarize the routes of administration and the effects of spermidine at different doses.

Absence of Streptococcus pneumoniae Capsule Increases Bacterial Binding, Persistence, and Inflammation in Corneal Infection

The role of the pneumococcal polysaccharide capsule is largely unclear for Streptococcus pneumoniae keratitis, an ocular inflammatory disease that develops as a result of bacterial infection of the cornea. In this study, capsule-deficient strains were compared to isogenic parent strains in their ability to adhere to human corneal epithelial cells. One isogenic pair was further used in topical ocular infection of mice to assess the contribution of the capsule to keratitis. The results showed that non-encapsulated pneumococci were significantly more adherent to cells, persisted in significantly higher numbers on mouse corneas in vivo, and caused significant increases in murine ocular IL9, IL10, IL12-p70, MIG, and MIP-1-gamma compared to encapsulated S. pneumoniae. These findings indicate that the bacterial capsule impedes virulence and the absence of capsule impacts inflammation following corneal infection.