In vitro Susceptibilities of Methicillin-Susceptible and Resistant Staphylococci to Traditional Antibiotics Compared to a Novel Fluoroquinolone

The pathogenicity and virulence of the opportunistic pathogen Staphylococcus epidermidis

The pervasive presence of Staphylococcus epidermidis and other coagulase-negative staphylococci on the skin and mucous membranes has long underpinned a casual disregard for the infection risk that these organisms pose to vulnerable patients in healthcare settings. Prior to the recognition of biofilm as an important virulence determinant in S. epidermidis, isolation of this microorganism in diagnostic specimens was often overlooked as clinically insignificant with potential delays in diagnosis and onset of appropriate treatment, contributing to the establishment of chronic infection and increased morbidity or mortality. While impressive progress has been made in our understanding of biofilm mechanisms in this important opportunistic pathogen, research into other virulence determinants has lagged S. aureus. In this review, the broader virulence potential of S. epidermidis including biofilm, toxins, proteases, immune evasion strategies and antibiotic resistance mechanisms is surveyed, together with current and future approaches for improved therapeutic interventions.

The Preventive Effect of Gentamicin in the Irrigating Solution on Endophthalmitis Caused by Methicillin-Resistant Staphylococcus epidermidis After Phacoemulsification with Intraocular Lens Implantation in Rabbits

OBJECTIVE

To analyze the effect of gentamicin in the irrigating solution on endophthalmitis caused by methicillin-resistant Staphylococcus epidermidis after phacoemulsification with intraocular lens implantation.

METHODS

Fifteen rabbits were randomly assigned into three groups. During surgery, group A was irrigated with gentamicin-free solution and injected with 100 μL of normal saline postoperatively, group B was irrigated with 80 μg/mL gentamicin and injected with 100 μl of MRSE suspension, group C was irrigated with gentamicin-free solution and injected with 100 μl of MRSE suspension. At different times, corneal endothelial cell count (CEC), inflammation grading，B-scan ultrasonography and histological examination were analyzed.

RESULTS

No endophthalmitis occurred in groups A and B. Group C developed severe endophthalmitis, with massive inflammatory exudation in the vitreous cavity.

CONCLUSION

Irrigating solution containing gentamicin is favorable to reduce the incidence of MRSE endophthalmitis after phacoemulsification with IOL in rabbits.

Antibacterial and antibiofilm potentials of vancomycin-loaded niosomal drug delivery system against methicillin-resistant Staphylococcus aureus (MRSA) infections

The threat of methicillin-resistant Staphylococcus aureus (MRSA) is increasing worldwide, making it significantly necessary to discover a novel way of dealing with related infections. The quick spread of MRSA isolates among infected individuals has heightened public health concerns and significantly limited treatment options. Vancomycin (VAN) can be applied to treat severe MRSA infections, and the indiscriminate administration of this antimicrobial agent has caused several concerns in medical settings. Owing to several advantageous characteristics, a niosomal drug delivery system may increase the potential of loaded antimicrobial agents. This work aims to examine the antibacterial and anti-biofilm properties of VAN-niosome against MRSA clinical isolates with emphasis on cytotoxicity and stability studies. Furthermore, we aim to suggest an effective approach against MRSA infections by investigating the inhibitory effect of formulated niosome on the expression of the biofilm-associated gene (icaR). The thin-film hydration approach was used to prepare the niosome (Tween 60, Span 60, and cholesterol), and field emission scanning electron microscopy (FE-SEM), an in vitro drug release, dynamic light scattering (DLS), and entrapment efficiency (EE%) were used to investigate the physicochemical properties. The physical stability of VAN-niosome, including hydrodynamic size, polydispersity index (PDI), and EE%, was analyzed for a 30-day storage time at 4 °C and 25 °C. In addition, the human foreskin fibroblast (HFF) cell line was used to evaluate the cytotoxic effect of synthesized niosome. Moreover, minimum inhibitory and bactericidal concentrations (MICs/MBCs) were applied to assess the antibacterial properties of niosomal VAN formulation. Also, the antibiofilm potential of VAN-niosome was investigated by microtiter plate (MTP) and real-time PCR methods. The FE-SEM result revealed that synthesized VAN-niosome had a spherical morphology. The hydrodynamic size and PDI of VAN-niosome reported by the DLS method were 201.2 nm and 0.301, respectively. Also, the surface zeta charge of the prepared niosome was - 35.4 mV, and the EE% ranged between 58.9 and 62.5%. Moreover, in vitro release study revealed a sustained-release profile for synthesized niosomal formulation. Our study showed that VAN-niosome had acceptable stability during a 30-day storage time. Additionally, the VAN-niosome had stronger antibacterial and anti-biofilm properties against MRSA clinical isolates compared with free VAN. In conclusion, the result of our study demonstrated that niosomal VAN could be promising as a successful drug delivery system due to sustained drug release, negligible toxicity, and high encapsulation capacity. Also, the antibacterial and anti-biofilm studies showed the high capacity of VAN-niosome against MRSA clinical isolates. Furthermore, the results of real-time PCR exhibited that VAN-niosome could be proposed as a powerful strategy against MRSA biofilm via down-regulation of icaR gene expression.

Comparison of the in vitro activities of delafloxacin and comparators against Staphylococcus epidermidis clinical strains involved in osteoarticular infections: a CRIOGO multicentre retrospective study

OBJECTIVES

Staphylococcus epidermidis bone and joint infections (BJIs) on material are often difficult to treat. The activity of delafloxacin has not yet been studied on S. epidermidis in this context. The aim of this study was to assess its in vitro activity compared with other fluoroquinolones, against a large collection of S. epidermidis clinical strains.

METHODS

We selected 538 S. epidermidis strains isolated between January 2015 and February 2023 from six French teaching hospitals. One hundred and fifty-two strains were ofloxacin susceptible and 386 were ofloxacin resistant. Identifications were performed by MS and MICs were determined using gradient concentration strips for ofloxacin, levofloxacin, moxifloxacin and delafloxacin.

RESULTS

Ofloxacin-susceptible strains were susceptible to all fluoroquinolones. Resistant strains had higher MICs of all fluoroquinolones. Strains resistant to ofloxacin (89.1%) still showed susceptibility to delafloxacin when using the Staphylococcus aureus 2021 CA-SFM/EUCAST threshold of 0.25 mg/L. In contrast, only 3.9% of the ofloxacin-resistant strains remained susceptible to delafloxacin with the 0.016 mg/L S. aureus breakpoint according to CA-SFM/EUCAST guidelines in 2022. The MIC50 was 0.094 mg/L and the MIC90 was 0.38 mg/L.

CONCLUSIONS

We showed low delafloxacin MICs for ofloxacin-susceptible S. epidermidis strains and a double population for ofloxacin-resistant strains. Despite the absence of breakpoints for S. epidermidis, delafloxacin may be an option for the treatment of complex BJI, including strains with MICs of ≤0.094 mg/L, leading to 64% susceptibility. This study underlines the importance for determining specific S. epidermidis delafloxacin breakpoints for the management of BJI on material.

Reimagining the Past: A Future for Antibiotic Drug Discovery in Ophthalmology

ABSTRACT

Antibiotic resistance has emerged as a critical threat for the treatment of bacterial ocular infections. To address the critical need for novel therapeutics, antibiotic drug repurposing holds significant promise. As such, examples of existing FDA-approved drugs currently under development for new applications, novel combinations, and improved delivery systems are discussed.

Evaluation of the effect of gentamicin in surgical perfusion solution on cataract postoperative endophthalmitis

Objective

To evaluate the effect of gentamicin in surgical perfusion solution on endophthalmitis incidence after cataract surgery.

Methods

A retrospective analysis of endophthalmitis incidence was conducted in two groups of patients who underwent cataract surgery, with (Group B) or without gentamicin (Group A) in the surgical perfusion solution. Endophthalmitis incidence, the isolated pathogenic bacteria strains and their antibiotic sensitivity, and the drug-resistant genotype of the pathogens were examined.

Results

The incidence of endophthalmitis in patients of group A was 0.8‰. Thirteen pathogenic bacterial strains were isolated from the patient samples in group A, including 8 strains of Staphylococcus epidermidis, 1 Staphylococcus aureus, 1 Streptococcus pneumoniae, 1 Streptococcus bovis, 1 Enterococcus faecium and 1 Morganella sp. The incidence of endophthalmitis in group B patients was 0.2‰, which was significantly lower than that in group A (P<0.05). Five strains of pathogenic bacteria were successfully isolated, including 2 strains of Enterococcus faecium, 1 Enterococcus faecalis, 1 Staphylococcus epidermidis and 1 Staphylococcus aureus. There was no significant difference in the proportion of Staphylococcus strains in all isolated bacteria between the two groups (P > 0.05). However, the proportion of Enterococci isolated in group B samples was higher than that in group A (P < 0.05). There were more gentamicin-sensitive strains than levofloxacin-sensitive strains identified (P < 0.05). Interestingly, aminoglycoside-inactivating enzyme resistance gene was detected in Enterococcus strains.

Conclusion

Our data suggest that gentamicin-containing perfusion solution can reduce the incidence of postoperative endophthalmitis in cataract patients. However, the selective pressure imposed by gentamicin may facilitate the development of aminoglycoside-resistant Enterococcos strains.

Delafloxacin-Capped Gold Nanoparticles (DFX-AuNPs): An Effective Antibacterial Nano-Formulation of Fluoroquinolone Antibiotic

New antibiotics are seen as 'drugs of last resort' against virulent bacteria. However, development of resistance towards new antibiotics with time is a universal fact. Delafloxacin (DFX) is a new fluoroquinolone antibiotic that differs from existing fluoroquinolones by the lack of a protonatable substituent, which gives the molecule a weakly acidic nature, affording it higher antibacterial activity under an acidic environment. Furthermore, antibiotic-functionalized metallic nanoparticles have been recently emerged as a feasible platform for conquering bacterial resistance. In the present study, therefore, we aimed at preparing DFX-gold nano-formulations to increase the antibacterial potential of DFX. To synthesize DFX-capped gold nanoparticles (DFX-AuNPs), DFX was used as a reducing and stabilizing/encapsulating agent. Various analytical techniques such as UV-visible spectroscopy, TEM, DLS, FTIR and zeta potential analysis were applied to determine the properties of the synthesized DFX-AuNPs. The synthesized DFX-AuNPs revealed a distinct surface plasmon resonance (SPR) band at 530 nm and an average size of 16 nm as manifested by TEM analysis. In addition, Zeta potential results (-19 mV) confirmed the stability of the synthesized DFX-AuNPs. Furthermore, FTIR analysis demonstrated that DFX was adsorbed onto the surface of AuNPs via strong interaction between AuNPs and DFX. Most importantly, comparative antibacterial analysis of DFX alone and DFX-AuNPs against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus and Bacillus subtilis) verified the superior antibacterial activity of DFX-AuNPs against the tested microorganisms. To sum up, DFX gold nano-formulations can offer a promising possible solution, even at a lower antibiotic dose, to combat pathogenic bacteria.

Potential new fluoroquinolone treatments for suspected bacterial keratitis

Topical fluoroquinolones (FQs) are an established treatment for suspected microbial keratitis. An increased FQ resistance in some classes of bacterial pathogens is a concern. Some recently developed FQs have an extended spectrum of activity, making them a suitable alternative for topical ophthalmic use. For example, the new generation FQs, avarofloxacin, delafloxacin, finafloxacin, lascufloxacin, nadifloxacin, levonadifloxacin, nemonoxacin and zabofloxacin have good activity against the common ophthalmic pathogens such as Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pneumoniae and several of the Enterobacteriaceae. However, because there are no published ophthalmic break-point concentrations, the susceptibility of an isolated micro-organism to a topical FQ is extrapolated from systemic break-point data and wild type susceptibility. The purpose of this review is to compare the pharmacokinetics and pharmacodynamics of the FQs licensed for topical ophthalmic use with the same parameters for new generation FQs. We performed a literature review of the FQs approved for topical treatment and the new generation FQs licensed to treat systemic infections. We then compared the minimum inhibitory concentrations (MIC) of bacterial isolates and the published concentrations that FQs achieved in the cornea and aqueous. We also considered the potential suitability of new generation FQs for topical use based on their medicinal properties. Notably, we found significant variation in the reported corneal and aqueous FQ concentrations so that reliance on the reported mean concentration may not be appropriate, and the first quartile concentration may be more clinically relevant. The provision of the MIC for the microorganism together with the achieved lower (first) quartile concentration of a FQ in the cornea could inform management decisions such as whether to continue with the prescribed antimicrobial, increase the frequency of application, use a combination of antimicrobials or change treatment.

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.

Endophthalmitis in Eyes With the Boston Type I Keratoprosthesis: Incidence, Recurrence, Risk Factors, and Outcomes

PURPOSE

To determine the incidence and recurrence of Boston type I keratoprosthesis (KPro)-associated endophthalmitis, and its microbiological profile, risk factors, and outcomes.

METHODS

This is a retrospective study of 158 consecutive KPro procedures with a median follow-up of 78.4 months. Medical charts were reviewed for ocular history, contact lens and topical antibiotic use, visual acuity, and complications. For eyes with endophthalmitis, time to infection, culture results, and recurrences were collected. Cox regression analyses identified risk factors for endophthalmitis and compared the risk for visual failure, KPro retention, and globe loss between eyes with and without endophthalmitis.

RESULTS

The incidence and recurrence rates of endophthalmitis were of 1.7% and 6.0% per procedure-year, respectively. First episodes occurred at a median of 18.6 months. Eight of 18 episodes (44%) were culture positive, isolating mainly Gram-positive bacteria (7 [88%]). Previous ocular burn (hazard ratio: 7.34, 95% confidence interval: 1.91-28.15), infectious keratitis (5.09, 1.70-15.22), corneal melt (4.55, 1.50-13.83), and postoperative contact lens wear (4.19, 1.17-15.04) were risk factors. Eyes with endophthalmitis did not have a higher risk for visual failure (1.74, 0.78-3.91) but were more likely to not retain the KPro (2.81, 1.15-6.88) and undergo evisceration (2.81, 1.15-6.88). All eyes lost ≥ 2 lines of vision during the endophthalmitis episode.

CONCLUSIONS

Endophthalmitis is rare but vision and globe threatening in eyes with KPro. Given the increased associated risk, corneal melts and infectious keratitis must be promptly treated, postoperative contact lenses should be considered on a case-by-case basis, and patients with ocular burns might require more aggressive antimicrobial prophylaxis.

In Vitro Probitotic Evaluation of Saccharomyces boulardii with Antimicrobial Spectrum in a Caenorhabditis elegans Model

In the present study, we screened for potential probiotic yeast that could survive under extreme frozen conditions. The antimicrobial and heat-stable properties of the isolated yeast strains Saccharomyces boulardii (S. boulardii) (KT000032, KT000033, KT000034, KT000035, KT000036, and KT000037) was analyzed and compared with commercial probiotic strains. The results revealed that the tested S. boulardii KT000032 strain showed higher resistance to gastric enzymes (bile salts, pepsin, and pancreatic enzyme) at low pH, with broad antibiotic resistance. In addition, the strain also showed efficient auto-aggregation and co-aggregation abilities and efficient hydrophobicity in the in-vitro and in-vivo C. elegens gut model. Further, the KT000032 strain showed higher antimicrobial efficiency against 13 different enteropathogens and exhibited commensal relationships with five commercial probiotic strains. Besides, the bioactive compounds produced in the cell-free supernatant of probiotic yeast showed thermo-tolerance (95 °C for two hours). Furthermore, the thermo-stable property of the strains will facilitate their incorporation into ready-to-eat food products under extreme food processing conditions.

Characterization of Pseudomonas aeruginosa isolates from patients with endophthalmitis using conventional microbiologic techniques and whole genome sequencing

Purpose

To demonstrate antibiotic susceptibility and genomic virulence factor profiles of Pseudomonas aeruginosa isolates from patients with culture-confirmed endophthalmitis.

Methods

Clinical isolates from patients diagnosed with pseudomonas endophthalmitis were included. Laboratory antibiotic susceptibility testing and whole genome sequencing was performed on all isolates.

Results

In the current study, 8 patients had vitreous culture-confirmed endophthalmitis due to P. aeruginosa. All isolates were multi-drug resistant but sensitive to ceftazidime and each fluoroquinolone tested. Whole genome sequencing revealed a total of 179 unique genes. The most common type of virulence genes included those involved in adherence and the secretion system. Seven of 8 (88%) isolates were of the cytoinvasive phenotype (exoST) and no isolates contained exoU.

Conclusions

P. aeruginosa associated endophthalmitis is often multi-drug resistant and demonstrates a variety of virulence factors with those involved in adherence and the secretion system being the most common.