Staphylococcus aureus and its Bearing on Ophthalmic Disease

Exogenous Methicillin-Resistant Staphylococcus aureus Endophthalmitis is Caused by Multidrug-Resistant Lineages that are Associated with Poor Outcomes

PURPOSE

To investigate the genomic epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) endophthalmitis and correlate it with the presenting clinical features and outcomes.

METHODS

Nine patients presenting with MRSA endophthalmitis from 2014 to 2022 were included. Phenotypic and genomic tests were used for strain characterization. Demographics, clinical presentation, treatment and outcomes were reviewed.

RESULTS

The MRSA population was dominated by multidrug-resistant (MDR) strains within the clonal complex 5 (CC5) carrying an SCCmec type II genetic element (USA100-like strains). These strains carried genes that confer resistance to five antibiotic classes, in addition to mutations in topoisomerase genes (gyrA and parC) that resulted in resistance to all fluoroquinolones tested. Patients were mostly male (56%), with a median age of 82.7 years, and most had no recent history of extensive healthcare exposure. All cases were exogenous following ocular surgery (67%) or intravitreal injection (33%). The main exam findings were visual acuity ≤ hand motion, hypopyon (89%), and vitreous opacity (89%). Five patients (56%) showed improvement in visual acuity at 1 month following presentation, three (33%) at 3 months, and two (22%) at 6 months. Complications included evisceration (n = 1) and phthisis (n = 1). Patients who had pars plana vitrectomy within 48 hours of presentation had better clinical outcomes compared to those who did not.

CONCLUSION

Exogenous MRSA endophthalmitis is caused by MDR strains that resemble the hospital-acquired lineage USA100. These strains cause severe endophthalmitis in patients with no recent hospital/healthcare exposure.

Insights into the Antimicrobial Mechanisms of a Scorpion Defensin on Staphylococcus aureus Using Transcriptomic and Proteomic Analyses

Defensins constitute a family of cationic antimicrobial peptides that act against different bacteria; however, global information regarding their antibacterial mechanisms from omics-based analyses is highly limited. In this study, transcriptomics and proteomics were used to explore the antibacterial mechanisms of defensin (BmKDfsin4) originally isolated from a scorpion on a common Gram-positive bacterium. Staphylococcus aureus (AB94004) was treated with BmKDfsin4 for 15, 30, or 45 min based on its ability to moderately inhibit bacterial growth for one hour. Compared with those in the control group, more than 1000 genes and nearly 500 proteins in S. aureus were significantly differentially expressed after BmKDfsin4 treatment. In-depth analysis revealed that BmKDfsin4 significantly upregulated bacterial ribosome-related pathways and ribosomal components. In contrast, BmKDfsin4 also significantly downregulated the synthesis and metabolism pathways of bacterial amino acids. Moreover, BmKDfsin4 inhibited the synthesis pathways of teichoic acid and peptidoglycan, which are the key components of the cell wall in S. aureus. Furthermore, glycolysis and other metabolic processes in S. aureus were markedly reduced by BmKDfsin4. Overall, the global information detected from S. aureus revealed the multiple antibacterial mechanisms of BmKDfsin4, which could encourage the exploration of global bacterial information from the defensin family with high degrees of sequence variability and accelerate the research and development of defensins as new antibacterial agents.

Wearable, Biocompatible, and Dual-Emission Ocular Multisensor Patch for Continuous Profiling of Fluoroquinolone Antibiotics in Tears

The abuse or misuse of antibiotics in clinical and agricultural settings severely endangers human health and ecosystems, which has raised profound concerns for public health worldwide. Trace detection and reliable discrimination of commonly used fluoroquinolone (FQ) antibiotics and their analogues have consequently become urgent to guide the rational use of antibiotic medicines and deliver efficient treatments for associated diseases. Herein, we report a wearable eye patch integrated with a quadruplex nanosensor chip for noninvasive detection and discrimination of primary FQ antibiotics in tears during routine eyedrop treatment. A set of dual-mode fluorescent nanoprobes of red- or green-emitting CdTe quantum dots integrated with lanthanide ions and a sensitizer, adenosine monophosphate, were constructed to provide an enhanced fluorescence up to 45-fold and nanomolar sensitivity toward major FQs owing to the aggregation-regulated antenna effect. The aggregation-driven, CdTe-Ln(III)-based microfluidic sensor chip is highly specific to FQ antibiotics against other non-FQ counterparts or biomolecular interfering species and is able to accurately discriminate nine types of FQ or non-FQ eyedrop suspensions using linear discriminant analysis. The prototyped wearable sensing detector has proven to be biocompatible and nontoxic to human tissues, which integrates the entire optical imaging modules into a miniaturized, smartphone-based platform for field use and reduces the overall assay time to ∼5 min. The practicability of the wearable eye patch was demonstrated through accurate quantification of antibiotics in a bactericidal event and the continuous profiling of FQ residues in tears after using a typical prescription antibiotic eyedrop. This technology provides a useful supplement to the toolbox for on-site and real-time examination and regulation of inappropriate daily drug use that might potentially lead to long-term antibiotic abuse and has great implications in advancing personal healthcare techniques for the regulation of daily medication therapy.

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.

Recent advancements in nanotechnology-based bacteriophage delivery strategies against bacterial ocular infections

Antibiotic resistance is growing as a critical challenge in a variety of disease conditions including ocular infections leading to disastrous effects on the human eyes. Staphylococcus aureus (S. aureus) mediated ocular infections are very common affecting different parts of the eye viz. vitreous chamber, conjunctiva, cornea, anterior and posterior chambers, tear duct, and eyelids. Blepharitis, dacryocystitis, conjunctivitis, keratitis, endophthalmitis, and orbital cellulitis are some of the commonly known ocular infections caused by S. aureus. Some of these infections are so fatal that they could cause bilateral blindness like panophthalmitis and orbital cellulitis, which is caused by methicillin-resistant S. aureus (MRSA) and vancomycin-resistance S. aureus (VRSA). The treatment of S. aureus infections with known antibiotics is becoming gradually difficult because of the development of resistance against multiple antibiotics. Apart from the different combinations and formulation strategies, bacteriophage therapy is growing as an effective alternative to treat such infections. Although the superiority of bacteriophage therapy is well established, yet physical factors (high temperatures, acidic pH, UV-rays, and ionic strength) and pharmaceutical barriers (poor stability, low in-vivo retention, controlled and targeted delivery, immune system neutralization, etc.) have the greatest influence on the viability of phage virions (also phage proteins). A variety of Nanotechnology based formulations such as polymeric nanoparticles, liposomes, dendrimers, nanoemulsions, and nanofibres have been recently reported to overcome the above-mentioned obstacles. In this review, we have compiled all these recent reports and discussed bacteriophage-based nanoformulations techniques for the successful treatment of ocular infections caused by multidrug-resistant S. aureus and other bacteria.

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.

The burden of methicillin-resistant Staphylococcus aureus in the delivery of eye care

Background

To describe the clinical presentation, burden and antimicrobial resistance of Methicillin-Resistant Staphylococcus aureus (MRSA) eye infections and to recommend a streamlined protocol for the management of ocular MRSA colonisation detected by pre-operative screening.

Methods

A retrospective review of all ocular samples which resulted in the isolation of MRSA between 1^st of January 2013 and 31^st of December 2019 at the Royal Victoria Eye and Ear Hospital.

Results

A total of 185 samples taken from the ocular surface were MRSA positive. The majority were MRSA colonisation of the ocular surface obtained as part of an MRSA screen (139/6955 patients screened; 2%). Forty-six represented MRSA infections (46/7904 eye samples; 0.58%), most occurring in older patients the majority of whom had known local or systemic risk factors for colonisation. The most common presentation was conjunctivitis (n = 24), followed by pre-septal cellulitis (n = 9). MRSA infections with the poorest clinical outcomes and the longest inpatient stay, were keratitis (n = 6) and post-operative endophthalmitis (n = 2). Our study demonstrated over 60% resistance to azithromycin, fusidic acid and ciprofloxacin, although resistance to chloramphenicol was uncommon.

Conclusion

This study demonstrates that MRSA infections of the eye most commonly manifest as a mild infection, typically conjunctivitis, and are generally non-sight threatening. The majority of presentations occur in the context of known MRSA risk factors and in an older populous. Resistance to chloramphenicol is rare, thus it remains an excellent first line treatment. Its use to eradicate MRSA from the ocular surface is proposed to streamline the delivery of surgical eye care.

Surveillance of post-cataract endophthalmitis at a tertiary referral center: a 10-year critical evaluation

BACKGROUND

Acute post-cataract endophthalmitis (APE) is a rare complication potentially causing irreversible visual loss. A 10-year study of APE was conducted to determine its incidence, microbiological spectra and antibiotic resistance profile of APE-related pathogens at a major tertiary referral center in Brazil.

METHODS

APE cases reported between January 2010 and December 2019 were included. Phacoemulsification and extracapsular cataract techniques were eligible; combined procedures, traumatic and congenital cataract were excluded. Vitreous samples were cultured and antimicrobial resistance was compared for the periods of 2010-2014 and 2015-2019. The results were analyzed with Fisher's exact test.

RESULTS

Our sample consisted of 40,491 cataract surgeries and 51 (0.126%) APE cases. Culture was positive in 35 cases (71.4%), of which 31 (88.6%) Gram-positive, 3 (8.6%) Gram-negative, and 1 (2.9%) fungal. The most frequently isolated organism was Staphylococcus epidermidis (n = 17/35, 48.6%), followed by Staphylococcus aureus (n = 4/35, 11.4%). From 2010-2014 to 2015-2019, antimicrobial resistance increased against moxifloxacin (11.1-54.5%, p = 0.07), ciprofloxacin (54.5-72.7%, p = 0.659) and oxacillin (66.7-93.3%, p = 0.13).

CONCLUSIONS

The observed incidence and microbial spectra were compatible with previous studies. A trend towards growing moxifloxacin and ciprofloxacin resistance was observed. Surveillance remains crucial to prevent treatment failure from antimicrobial resistance.

Mild temperature photothermal assisted anti-bacterial and anti-inflammatory nanosystem for synergistic treatment of post-cataract surgery endophthalmitis

Rationale: Endophthalmitis, which is one of the severest complications of cataract surgeries, can seriously threaten vision and even lead to irreversible blindness owing to its complicated microenvironment, including both local bacterial infection and severe inflammation. It is urgent to develop a comprehensive treatment for both anti-bacterial and anti-inflammatory effects.

Methods: Herein, we developed AuAgCu₂O-bromfenac sodium nanoparticles (AuAgCu₂O-BS NPs), which was designed to combine anti-bacterial and anti-inflammatory effects for integrated therapy of endophthalmitis after cataract surgery. The AuAgCu₂O-BS NPs could eradicate methicillin-resistant Staphylococcus aureus (MRSA) bacterial strain relied on their photodynamic effects and the release of metal ions (Ag⁺ and Cu⁺) by the hollow AuAgCu₂O nanostructures mediated mild photothermal effects. The anti-inflammatory drug, bromfenac sodium, released from the nanoparticles were able to significantly reduce the local inflammation of the endophthalmitis and promote tissue rehabilitation. In vivo bacterial elimination and anti-inflammation were confirmed by a postcataract endophthalmitis rabbit model.

Results: Excellent antibacterial ability of AuAgCu₂O-BS NPs was verified both in vitro and in vivo. Ophthalmological clinical observation and pathologic histology analysis showed prominent treatment of inflammatory reaction. Importantly, the mild temperature photothermal effect not only promoted the release of metal ions and bromfenac sodium but also avoided the thermal damage of the surrounding tissues, which was more suitable for the practical application of ophthalmology due to the complex structure of the eyeball. Moreover, superior biocompatibility was approved by the preliminary toxicity investigations, including low cytotoxicity, negligible damage to major organs, and stable intraocular pressure.

Conclusions: Our studies of nanosystem provide a promising synergic therapeutic strategy for postcataract endophthalmitis treatment with favorable prognosis and promise in clinical translations.

A SYBR Green based multiplex Real-Time PCR assay for rapid detection and differentiation of ocular bacterial pathogens

PURPOSE

Ocular bacterial pathogenesis is a serious sight threatening infection due to several bacterial species like Staphylococcus aureus, Streptococcus pneumoniae and Pseudomonas aeruginosa which are predominant. It is necessary to expedite diagnosis of pathogens for early treatment. Hence, a SYBR Green based multiplex Real-Time PCR assay coupled with melting curve analysis has been developed for rapid detection and differentiation of Staphylococcus aureus, Streptococcus pneumoniae and Pseudomonas aeruginosa in a single reaction.

METHODS

The assay was designed for simultaneous detection and differentiation of pathogens based on their distinct melting curve. The analytical specificity, sensitivity and reproducibility of the assay were examined using various reference strains. Clinical validation was carried out with 100 ocular samples collected from patients suffering from ocular infections.

RESULT

Each reaction tested for the targets individually generated three non overlapping melting curves with well alienated peaks corresponding to each gene. Among 100 ocular samples tested, 40 samples diagnosed with positive results in RT-PCR. Thus assay showed 100% specificity with high sensitivity and reproducibility.

CONCLUSION

The developed assay consistently established as a rapid and accurate diagnosis of ocular bacterial pathogens compared to the conventional laboratory techniques. Such precise method would aid greatly in clinical management of devastating ocular infections.

In Vitro Antimicrobial Activity of Diacerein on 76 Isolates of Gram-Positive Cocci from Bacterial Keratitis Patients and In Vivo Study of Diacerein Eye Drops on Staphylococcus aureus Keratitis in Mice

Bacterial keratitis is an aggressive infectious corneal disease. With the continuing rise in antibiotic resistance and a decline in the discovery of new antibiotics, new antimicrobial drugs are now required. In the present study, we determined the antibacterial activity of diacerein, an anti-inflammatory drug, against 76 Gram-positive cocci isolated from bacterial keratitis patients in vitro and anti-Staphylococcus aureus activity in a mouse bacterial keratitis model in vivo The MICs of diacerein were tested using the broth microdilution method in vitro A BALB/c Staphylococcus aureus keratitis animal model was selected and the corneal clinical observation, viable bacteria, and hematoxylin-eosin and Gram staining of infected corneas were measured to evaluate the antibacterial efficacy of diacerein eye drops in vivo An in vivo eye irritation study was carried out by a modified Draize test in rabbits. Our in vitro results showed that diacerein possesses satisfactory antibacterial activity against the majority of Gram-positive cocci (60/76), including all 57 tested Staphylococcus spp. and 3 Enterococcus spp. The in vivo experiment showed that diacerein eye drops reduced bacterial load and improved ocular clinical scores after topical administration of diacerein drops on infected corneas. The ocular irritation test revealed that diacerein eye drop had excellent ocular tolerance. These results indicated that diacerein possesses in vivo anti-Staphylococcus aureus activity. We suggest that diacerein is a possible topically administered drug for Staphylococcus aureus-infected patients, especially those with ocular surface inflammatory disorders.

Staphylococcus aureus from ocular and otolaryngology infections are frequently resistant to clinically important antibiotics and are associated with lineages of community and hospital origins

Staphylococcus aureus is an important human pathogen that causes serious antibiotic-resistant infections. Its population structure is marked by the appearance and dissemination of successful lineages across different settings. To begin understanding the population structure of S. aureus causing ocular and otolaryngology infections, we characterized 262 isolates by antimicrobial sensitivity testing and multilocus sequence typing (MLST). Methicillin-resistant S. aureus were subjected to SCCmec typing and Panton-Valentine leukocidin (PVL) screening. Although we detected a high level of genetic diversity among methicillin-sensitive (MSSA) isolates, (63 sequence types—STs), the population was dominated by five lineages: ST30, ST5, ST8, ST15 and ST97. Resistance to penicillin, erythromycin and clindamycin was common among the major MSSA lineages, with fluctuations markedly impacted by genetic background. Isolates belonging to the predominant lineage, ST30, displayed high rates of resistance to penicillin (100%), erythromycin (71%), and clindamycin (63%). Overall, 21% of the isolates were methicillin-resistant (MRSA), with an apparent enrichment among otitis and orbital cellulitis isolates (>40%). MRSA isolates belonged to 14 STs grouped in 5 clonal complexes (CC), however, CC5 (56.1%) and CC8 (38.6%) dominated the population. Most CC5 strains were SCCmec type II, and resembled the hospital-adapted USA100 clone. CC8 strains were SCCmec type IV, and 86% were positive for the PVL toxin, common features of the community-acquired clone USA300. CC5 strains harboring a SCCmec type IV, typical for the USA800 clone, comprised 15.5% of the population. USA100 strains were highly resistant to clindamycin, erythromycin and levofloxacin (100%), while USA300 strains were frequently resistant to erythromycin (89%) but displayed lower rates of resistance to levofloxacin (39%) and clindamycin (17%). Our data demonstrate that the ocular and otolaryngology S. aureus populations are composed of strains that are commonly resistant to clinically relevant antibiotics, and are associated with the major epidemic clonal complexes of both community and hospital origins.

Modeling intraocular bacterial infections

Bacterial endophthalmitis is an infection and inflammation of the posterior segment of the eye which can result in significant loss of visual acuity. Even with prompt antibiotic, anti-inflammatory and surgical intervention, vision and even the eye itself may be lost. For the past century, experimental animal models have been used to examine various aspects of the pathogenesis and pathophysiology of bacterial endophthalmitis, to further the development of anti-inflammatory treatment strategies, and to evaluate the pharmacokinetics and efficacies of antibiotics. Experimental models allow independent control of many parameters of infection and facilitate systematic examination of infection outcomes. While no single animal model perfectly reproduces the human pathology of bacterial endophthalmitis, investigators have successfully used these models to understand the infectious process and the host response, and have provided new information regarding therapeutic options for the treatment of bacterial endophthalmitis. This review highlights experimental animal models of endophthalmitis and correlates this information with the clinical setting. The goal is to identify knowledge gaps that may be addressed in future experimental and clinical studies focused on improvements in the therapeutic preservation of vision during and after this disease.

Anti-MRSA Activities of Enterocins DD28 and DD93 and Evidences on Their Role in the Inhibition of Biofilm Formation

Methicillin-resistant Staphylococcus aureus (MRSA) has become a worrisome superbug. This work aimed at studying the effects of two class IIb bacteriocins, enterocins DD28 and DD93 as anti-MRSA agents. Thus, these bacteriocins were purified, from the cultures supernatants of Enterococcus faecalis 28 and 93, using a simplified purification procedure consisting in a cation exchange chromatography and a reversed-phase high-performance liquid chromatography. The anti-Staphylococcal activity was shown in vitro by the assessment of the minimal inhibitory concentration (MIC), followed by a checkerboard and time-kill kinetics experiments. The data unveiled a clear synergistic effect of enterocins DD28 and DD93 in combination with erythromycin or kanamycin against the clinical MRSA-S1 strain. Besides, these combinations impeded as well the MRSA-S1 clinical strain to setup biofilms on stainless steel and glace devices.