Prevalence and Antimicrobial Resistance of Causative Agents to Ocular Infections

Multi-aptamer-mediated hairpin allosteric and aptamer-assisted CRISPR system for detection of S. pneumoniae and S. aureus

A novel nucleic acid aptamer nanoprobes-mediated hairpin allosteric and aptamer-assisted CRISPR system for detection of Streptococcus pneumoniae and Staphylococcus aureus is presented. In this fluorescence assay system, utilizing the hairpin allosteric effect caused by the aptamer binding to the target bacteria, the detection of S. pneumoniae is first achieved through changes in fluorescence due to FRET. Subsequently, a Cas12a protein mixture is added to detect S. aureus. The amplified output signal is triggered by two methods to ensure the sensitivity of the method: the synergistic FRET effect is achieved by the assembly of multi-aptamer through the conjugation of streptavidin-biotin, and the trans-cleavage function of CRISPR/Cas 12a. Under the optimized conditions, the proposed hairpin allosteric aptasensor could achieve high sensitivity (a detection limit of 135 cfu/mL) and broad-concentration quantification (dynamic range of 103-107 cfu/mL) of S. pneumoniae. The aptamer-assisted CRISPR system for S. aureus detection showed good linearity (R2 = 0.996) in the concentration range 102-108 cfu/mL, with a detection limit of 39 cfu/mL. No cross-reactivity with other foodborne pathogenic bacteria was observed in both systems. Taking only 55 min, this method of multiple pathogen detection proved to be promising.

Molecular Characterization of Bacterial Agents Causing External Ocular Infections Isolates of Patients in a Third Level Hospital

Empirical use of antibiotics in the treatment of eye infections leads to bacterial pathogens becoming resistant to antibiotics; consequently, treatment failure and eye health complications occur. The aim of this study was to describe the phenotype and genotype of the resistance and adherence of bacterial agents causing eye infections in patients at Hospital Juárez de México. An observational, prospective, cross-sectional, and descriptive study was carried out in patients with signs and symptoms of ocular infection. Bacterial agents were isolated and identified by classical microbiology and mass spectrometry. Antibiotic resistance and adherence profiles were determined. Finally, resistance (mecA/SCCmec) and virulence (icaA and icaD) genes were detected in the Gram-positive population. The results showed that blepharitis was the most prevalent condition in the study population. A MALDI-TOF analysis revealed that Staphylococcus and Pseudomonas genus were the most prevalent as causal agents of infection. Resistances to β-lactams were detected of 44 to 100%, followed by clindamycins, aminoglycosides, folate inhibitors, and nitrofurans. A multiple correspondence analysis showed a relationship between mecA genotype and β-lactams resistance. The identification of SCCmecIII and SCCmecIV elements suggested community and hospital sources of infection. Finally, the coexistence of icaA+/icaD+/mecA(SCCmecIII) and icaA+/icaD+/mecA(SCCmecIV) genotypes was detected in S. aureus. The identification of resistant and virulent isolates highlights the importance of developing protocols that address the timely diagnosis of ocular infections. Herein, implications for the failure of antimicrobial therapy in the treatment of ocular infections in susceptible patients are analysed and discussed.

Managing Corneal Infections: Out with the old, in with the new?

There have been multiple reports of eye infections caused by antibiotic-resistant bacteria, with increasing evidence of ineffective treatment outcomes from existing therapies. With respect to corneal infections, the most commonly used antibiotics (fluoroquinolones, aminoglycosides, and cephalosporines) are demonstrating reduced efficacy against bacterial keratitis isolates. While traditional methods are losing efficacy, several novel technologies are under investigation, including light-based anti-infective technology with or without chemical substrates, phage therapy, and probiotics. Many of these methods show non-selective antimicrobial activity with potential development as broad-spectrum antimicrobial agents. Multiple preclinical studies and a limited number of clinical case studies have confirmed the efficacy of some of these novel methods. However, given the rapid evolution of corneal infections, their treatment requires rapid institution to limit the impact on vision and prevent complications such as scarring and corneal perforation. Given their rapid effects on microbial viability, light-based technologies seem particularly promising in this regard.

Current Advances in Nano-Based and Polymeric Stimuli-Responsive Drug Delivery Targeting the Ocular Microenvironment: A Review and Envisaged Future Perspectives

Optimal vision remains one of the most essential elements of the sensory system continuously threatened by many ocular pathologies. Various pharmacological agents possess the potential to effectively treat these ophthalmic conditions; however, the use and efficacy of conventional ophthalmic formulations is hindered by ocular anatomical barriers. Recent novel designs of ophthalmic drug delivery systems (DDS) using nanotechnology show promising prospects, and ophthalmic formulations based on nanotechnology are currently being investigated due to their potential to bypass these barriers to ensure successful ocular drug delivery. More recently, stimuli-responsive nano drug carriers have gained more attention based on their great potential to effectively treat and alleviate many ocular diseases. The attraction is based on their biocompatibility and biodegradability, unique secondary conformations, varying functionalities, and, especially, the stimuli-enhanced therapeutic efficacy and reduced side effects. This review introduces the design and fabrication of stimuli-responsive nano drug carriers, including those that are responsive to endogenous stimuli, viz., pH, reduction, reactive oxygen species, adenosine triphosphate, and enzymes or exogenous stimuli such as light, magnetic field or temperature, which are biologically related or applicable in clinical settings. Furthermore, the paper discusses the applications and prospects of these stimuli-responsive nano drug carriers that are capable of overcoming the biological barriers of ocular disease alleviation and/or treatment for in vivo administration. There remains a great need to accelerate the development of stimuli-responsive nano drug carriers for clinical transition and applications in the treatment of ocular diseases and possible extrapolation to other topical applications such as ungual or otic drug delivery.

Evaluation of the Pathogenic Potential of Escherichia coli Strains Isolated from Eye Infections

While primarily Gram-positive bacteria cause bacterial eye infections, several Gram-negative species also pose eye health risks. Currently, few studies have tried to understand the pathogenic mechanisms involved in E. coli eye infections. Therefore, this study aimed to establish the pathogenic potential of E. coli strains isolated from eye infections. Twenty-two strains isolated between 2005 and 2019 from patients with keratitis or conjunctivitis were included and submitted to traditional polymerase chain reactions (PCR) to define their virulence profile, phylogeny, clonal relationship, and sequence type (ST). Phenotypic assays were employed to determine hemolytic activity, antimicrobial susceptibility, and adhesion to human primary corneal epithelial cells (PCS-700-010). The phylogenetic results indicated that groups B2 and ST131 were the most frequent. Twenty-five virulence genes were found among our strains, with ecp, sitA, fimA, and fyuA being the most prevalent. Two strains presented a hemolytic phenotype, and resistance to ciprofloxacin and ertapenem was found in six strains and one strain, respectively. Regarding adherence, all but one strains adhered in vitro to corneal cells. Our results indicate significant genetic and virulence variation among ocular strains and point to an ocular pathogenic potential related to multiple virulence mechanisms.