Polymicrobial Versus Monomicrobial Keratitis: A Retrospective Comparative Study

Evaluating Medical Therapy Failure in Microbial Keratitis: Risk Factors and Management Alternatives

PURPOSE

To describe the treatments used in cases of infectious keratitis and determine the risk factors associated with treatment failure, including prolonged infection duration, treatment modifications, and the need for surgical intervention.

PATIENTS AND METHODS

This retrospective case series includes culture-proven microbial keratitis cases treated in nine hospitals in the region of Galicia, Spain, between 2010 and 2020.

RESULTS

A total of 654 patients were included. Prolonged infection duration was associated with factors such as advanced age, deep infiltrates, corneal thinning, and large epithelial defects. Initial empirical treatment was modified in 204 cases (31.2%), with 113 cases requiring changes due to antibiotic resistance and 88 cases due to clinical deterioration. Polymicrobial infections, contact with vegetable matter, previous herpetic keratitis, and topical steroid use were identified as risk factors for treatment modification. Surgical intervention was required in 142 cases (21.7%). Among these, 50 patients (7.6%) underwent evisceration, 43 (6.6%) received amniotic membrane transplantation, and 37 (5.7%) underwent tectonic penetrating keratoplasty. Previous keratoplasty, prior herpetic keratitis, topical steroid use, and large epithelial defects were also significant risk factors for surgical intervention.

CONCLUSIONS

Treatment failure in cases of microbial keratitis (MK) may be influenced by systemic factors, such as advanced age, and ocular factors, including large epithelial defects, deep infiltrates, polymicrobial infections, contact with vegetable matter, and previous topical steroid use. Identifying these risk factors is essential for guiding empirical treatment and recognizing refractory ulcers that may require more intensive management, including surgical intervention.

A Tear-Based Approach for Rapid Identification of Bacterial Pathogens in Corneal Ulcers Using Nanopore Sequencing

Purpose

This prospective observational study assesses the efficacy of using portable next-generation sequencing directly on tear samples to identify bacterial pathogens in corneal ulcers.

Methods

Tear samples were collected from ulcerated and contralateral eyes using Schirmer strips. Corneal scrapings and cultures were performed as medically indicated. The 16S rRNA gene was amplified from tear samples using polymerase chain reaction (PCR), and Nanopore sequencing was used for bacterial species identification and taxonomic classification.

Results

Bacterial DNA was identified in 8 of 10 samples using the tear-based sequencing method. Nanopore sequencing accurately identified the causative bacteria in all four samples that exhibited bacterial growth on culture and detected bacterial pathogens in two of the four ulcers that did not show bacterial growth on culture. In two cases where cultures could not be obtained due to the ulcer's small size, tear sequencing successfully identified bacterial species. Among the nine contralateral tear samples collected, Nanopore sequencing identified commensal bacteria in four samples.

Conclusions

PCR amplification of 16S rRNA directly from tears followed by Nanopore sequencing is an effective, noninvasive method to identify bacterial pathogens in corneal ulcers, offering noninferior results to traditional culture methods.

Translational Relevance

By eliminating the need for corneal scrapings and nucleic acid extraction, this tear-based method improves the timing and accuracy of bacterial pathogen diagnosis in corneal ulcers, allowing for prompt detection of causative organisms and enabling earlier targeted antimicrobial therapy, thereby improving patient outcomes.

Microbiological profiles of infectious corneal ulcers in Derbyshire and North Nottinghamshire-a 10-year analysis

PURPOSE

To assess the spectrum of organisms causing microbial keratitis and their in-vitro anti-microbial sensitivities out of 2 hospitals in the East Midlands Region of the United Kingdom.

METHODS

A retrospective review was undertaken of all patients who underwent corneal scrapes for infectious keratitis between 2011 and 2021 at Royal Derby Hospital (RDH) in Derby and between 2009 and 2021 at King's Mill Hospital in Mansfield.

RESULTS

In total, the results of 645 corneal scrapes (from 622 patients) were analysed after exclusions. Of these, 307 (47.6%) yielded positive cultures. The mean patient age was 52.6 ± 22.1 years (Mean ± St Dev) across both sites and 332 (51.4%) were from female patients. At RDH, there were 195 positive corneal scrape cultures, from which 250 species of organisms were isolated. At RDH, 64% (160/250) were Gram-positive bacteria, 32% (81/250) were Gram-negative bacteria, 2.4% (6/250) were Acanthamoeba species and 1.2% were fungi (3/250). At KMH, there were 112 positive cultures, from which 128 species of organisms were isolated. 14 corneal scrapes from KMH were polymicrobial. At KMH, 96% (123/128) were bacterial (51% Gram positive, 45% Gram negative), 3/128 (2.3%) were fungi and 2/128 (1.6%) were Acanthamoeba. Sensitivity testing confirmed that the fluoroquinolone class of antibiotics appeared to be effective against the majority isolates across the two hospital sites.

CONCLUSION

There are differences in microbiological profiles between these neighbouring hospitals covering neighbouring populations. Despite these differences, reassuringly, the current first-line fluoroquinolone monotherapy treatment is an appropriate first-line treatment for both hospital sites.

Predisposing factors, clinical and microbiological insights of bacterial keratitis: analysis of 354 cases from a leading French academic centre

AIMS

To report an epidemiological update of bacterial keratitis (BK) in a tertiary ophthalmology centre over 20 months compared with a previous study on the same timeframe from 1998 to 1999.

METHODS

354 patients with BK documented by microbiological corneal scraping or resolutive under antibiotics treatment from January 2020 to September 2021 were analysed retrospectively.

RESULTS

One or several risk factors were found in 95.2% of patients: contact lens wear (45.2%), ocular surface disease (25.0%), systemic disease (21.8%), ocular trauma (11.9%) and ocular surgery (8.8%). The positivity rate of corneal scrapings was 82.5%, with 18.2% polybacterial. One hundred seventy-five (59.9%) bacteria were Gram-negative, and 117 (40.1%) were Gram-positive. The most common bacteria were Pseudomonas aeruginosa (32.5%), Moraxella spp (18.1%) and Staphylococcus aureus (8.2%). Final visual acuity (logarithm of the minimum angle of resolution) was associated with age (r=+0.48; p=0.0001), infiltrate size (r=+0.32; p<0.0001), ocular surface disease (r=+0.13; p=0.03), ocular trauma (r=-0.14; p=0.02) and contact lens wear (r=-0.26; p<0.0001). Gram-negative bacteria were responsible for deeper (r=+0.18; p=0.004) and more extensive infiltrates (r=+0.18; p=0.004) in younger patients (r=-0.19; p=0.003). Compared with the previous period, the positivity rate of corneal scrapings and the proportion of Gram-negative bacteria, especially Moraxella spp, increased. All P. aeruginosa and Moraxella spp were sensitive to quinolones, and all S. aureus were sensitive to both quinolones and methicillin.

CONCLUSION

Contact lens wear remained the leading risk factor. The bacteria distribution was reversed, with a predominance of Gram-negative bacteria and increased Moraxella spp.

A Tear-Based Approach for Rapid Identification of Bacterial Pathogens in Corneal Ulcers Using Nanopore Sequencing

Purpose

Corneal ulcers pose a significant threat to vision, with the need for prompt and precise pathogen identification being critical to effective treatment. This study assesses the efficacy of using next-generation portable sequencing (Nanopore Technology) to detect and identify bacterial pathogens directly from tear samples, providing a non-invasive alternative to traditional corneal scraping and culture, which are limited by high false-negative rates.

Design

Prospective observational study.

Participants

Ten participants diagnosed with corneal ulcers.

Methods

Tear samples were collected from the ocular surface using Schirmer strips. Corneal scrapings and cultures were performed as medically indicated. The 16S rRNA gene was amplified directly from the tear samples using polymerase chain reaction (PCR), and Nanopore sequencing was used for bacterial species identification and taxonomic classification. Comparative analysis was conducted to evaluate the concordance between Nanopore sequencing results and traditional culture methods.

Main Outcome Measures

Comparison of bacterial species detected via Nanopore sequencing with those identified through traditional culture methods.

Results

Bacterial DNA was identified in 8 of the 10 samples analyzed using the tear-based sequencing method. Notably, Nanopore sequencing accurately identified the causative bacteria in all 4 samples that exhibited bacterial growth on culture. Additionally, it detected bacterial pathogens in 2 of the 4 ulcers that did not show bacterial growth on culture. In 2 cases where cultures could not be obtained due to the small size of the ulcer, tear sequencing successfully identified bacterial species, highlighting potentially overlooked pathogens in corneal ulcers.

Conclusions

PCR amplification of 16S RNA directly from tears followed by Nanopore sequencing is an effective, non-invasive method to identify bacterial pathogens in corneal ulcers, offering non-inferior results to traditional culture methods. This technique not only allows for the detection of traditionally hard-to-culture organisms, providing immediate diagnostic value to guide treatment, but also enhances our understanding of the microbiological landscape of corneal ulcers, thereby informing more effective treatment strategies.

Progressive ulcerative keratitis in dogs in the United Kingdom: Microbial isolates, antimicrobial sensitivity, and resistance patterns

OBJECTIVES

The objective of the study was to identify bacterial pathogens and their antimicrobial sensitivity profile associated with cases of canine progressive ulcerative keratitis.

MATERIALS AND METHODS

Analysis of microbial culture and sensitivity results from dogs with progressive ulcerative keratitis presenting to a UK referral practice between December 2018 and August 2020.

RESULTS

Positive bacterial cultures were obtained from 80/148 (54%) of the canine ulcers sampled with 99 bacterial isolates cultured. Streptococcus canis (n = 29), Pseudomonas aeruginosa (n = 19), and Staphylococcus pseudintermedius (n = 16) were the most common isolates. Pseudomonas aeruginosa was more likely to be isolated whether the ulcer was clinically malacic at the time of sampling (OR = 10.1, p < .001). Ulcers treated prior to culture with fusidic acid were 7.6 times more likely to be positive than those treated with any other antimicrobial(s). Bacterial isolates demonstrated resistance against neomycin (85%), fusidic acid (78%), and tetracycline (68%). Conversely, isolates were most likely to be sensitive to gentamicin (88%), ofloxacin (77%), ciprofloxacin (73%), and chloramphenicol (64%). Antimicrobial combinations of chloramphenicol or gentamicin with a fluoroquinolone (ofloxacin or ciprofloxacin) or chloramphenicol combined with gentamicin were the most effective on in vitro analysis (over 90% susceptibility of all isolates).

CONCLUSION

The most common bacterial species associated with canine progressive ulcerative keratitis in a UK referral population were S. canis, P. aeruginosa, and S. pseudintermedius. Combination antimicrobial therapy is recommended pending culture and sensitivity results given the varied antimicrobial susceptibility profiles and significant bacterial in vitro resistance to antimicrobial monotherapy.

Codetermination of antimicrobial agents in rabbit tear fluid using LC-MS/MS assay: Insights into ocular pharmacokinetic study

Managing ocular microbial infections typically requires pharmacotherapy using antibiotic eye drops, such as moxifloxacin hydrochloride (MFX), combined with an antifungal agent like amphotericin B (AB). We carried out and validated an LC-MS/MS assay to quantify these compounds in rabbit tear fluid in order to look into the pharmacokinetics of these two drugs. We employed a protein precipitation technique for the extraction of drugs under examination. A Waters Symmetry C18 column was used to separate the analytes and internal standard. The composition of the mobile phase was like (A) 0.1% v/v formic acid in water and (B) methanol. The detection of MFX and AB was accomplished through the utilization of positive ion electrospray ionization under multiple reaction monitoring mode. The linearity curves for both analytes exhibited an acceptable trendline across a concentration range of 2.34-300 ng/mL for MFX and 7.81-1000 ng/mL for AB in surrogate rabbit tear fluid. The lower limit of quantitation for MFX was 2.34 ng/mL, while for AB, it was 7.81 ng/mL. The approach was strictly validated, encompassing tests of selectivity, linearity (with r2 > 0.99), precision, accuracy, matrix effects, and stability. Consequently, we employed this method to evaluate the pharmacokinetics profiles of MFX and AB in rabbit tear fluid following single topical doses.

Rapid and strain-specific resistance evolution of Staphylococcus aureus against inhibitory molecules secreted by Pseudomonas aeruginosa

IMPORTANCE

Polymicrobial infections are common. In chronic infections, the different pathogens may repeatedly interact, which could spur evolutionary dynamics with pathogens adapting to one another. Here, we explore the potential of Staphylococcus aureus to adapt to its competitor Pseudomonas aeruginosa. These two pathogens frequently co-occur, and P. aeruginosa is seen as the dominant species being able to displace S. aureus. We studied three different S. aureus strains and found that all became quickly resistant to inhibitory compounds secreted by P. aeruginosa. Our experimental evolution revealed strains-specific adaptations with three main factors contributing to resistance evolution: (i) overproduction of staphyloxanthin, a molecule protecting from oxidative stress; (ii) the formation of small colony variants also protecting from oxidative stress; and (iii) alterations of membrane transporters possibly reducing toxin uptake. Our results show that species interactions can change over time potentially favoring species co-existence, which in turn could affect disease progression and treatment options.

Characterization of Polymicrobial and Antibiotic-Resistant Infectious Keratitis in a County Hospital Setting

Purpose

Infectious keratitis is a serious cause of visual impairment, particularly in low-income communities. This study examines the associations between social risk factors and polymicrobial keratitis, multidrug resistance, pathogen spectrum, and outcomes at a county hospital.

Methods

We performed a retrospective study of Zuckerberg San Francisco General Hospital patients treated for infectious keratitis from 2010-2021. Multivariable regression was performed to analyze the relationships between social, medical, and psychiatric risk factors with polymicrobial growth, multidrug resistance, and clinical outcomes.

Results

Of 174 patients with infectious keratitis, 44 (25%) had polymicrobial growth. Six patients (14%) with polymicrobial growth had multidrug-resistant organisms. Homeless patients were more likely to present with polymicrobial infection (OR 3.4, p = 0.023), and polymicrobial infections were associated with multidrug-resistant organisms (p = 0.018). Smoking, drug use, HIV positivity, prior corneal pathology, and contact lens use were not associated with an increased risk of polymicrobial infection. Eleven patients (6.3%) were started on topical antibiotics prior to presentation; of these, none developed polymicrobial infections or multidrug-resistant organisms. Polymicrobial infections increased the likelihood to initiation of fortified antibiotics (OR 2.9, p = 0.011) but did not impact ulcer size, final visual acuity, time to resolution, or likelihood of emergent procedures.

Conclusions

Homelessness correlates with an increased risk of polymicrobial keratitis and subsequent multidrug resistance, supporting initiation of broad antibiotic coverage in this population. Prior topical antibiotics did not increase risk of polymicrobial infection. Polymicrobial infection did not significantly worsen clinical outcomes.

Clinical and Microbiological Spectra and Therapeutic Outcomes of Polymicrobial Keratitis

PURPOSE

The aim of this study was to evaluate the risk factors, microbiology, and treatment outcomes of polymicrobial keratitis (PMK).

METHODS

We retrospectively analyzed 65 patients diagnosed with PMK between 2016 and 2019. The clinical and microbiological characteristics and outcomes were evaluated. The primary outcome measure was clinical resolution of keratitis. Absolute success (group A) was defined as resolution of infection with medical treatment, qualified success (group B) was resolution with medical therapy and additional minor procedures, and failure (group C) was defined as worsening of infection and presence of corneal melting or perforation requiring therapeutic penetrating keratoplasty or evisceration.

RESULTS

Of 4764 cases of microbial keratitis, PMK was identified in 65 eyes of 65 patients (1.36%). Infiltrate was central in 60% (39 eyes). Predisposing factors were higher in group C and included uncontrolled diabetes mellitus in 25% (7/28), history of trauma/foreign body in 57.1% (16/28), and poor presenting visual acuity (0.9 for group A vs. 1.79 for group B vs. 3.00 logarithm of the minimum angle of resolution for group C; P = 0.02). Microbiological profiling revealed that a majority (95%: 62/65) had bacterial with fungal keratitis. High fluoroquinolone resistance was noted (57%; 34/59). Absolute success was achieved in 28.3% (17/60), qualified success in 16.6% (10/60), and treatment failure was noted in 55% (33/60). The final best corrected visual acuity in group A was significantly better than that in group B and C (0.44 vs. 3.00 vs. 2.78; P < 0.001).

CONCLUSIONS

PMK is extremely rare but responds poorly to medical therapy. Bacterial with fungal etiology is predominant. Early surgical intervention to improve overall outcome is advocated.

ESKAPEE pathogens newly released from biofilm residence by a targeted monoclonal are sensitized to killing by traditional antibiotics

Introduction

The "silent" antimicrobial resistance (AMR) pandemic is responsible for nearly five million deaths annually, with a group of seven biofilm-forming pathogens, known as the ESKAPEE pathogens, responsible for 70% of these fatalities. Biofilm-resident bacteria, as they exist within the disease site, are canonically highly resistant to antibiotics. One strategy to counter AMR and improve disease resolution involves developing methods to disrupt biofilms. These methods aim to release bacteria from the protective biofilm matrix to facilitate their killing by antibiotics or immune effectors. Several laboratories working on such strategies have demonstrated that bacteria newly released from a biofilm display a transient phenotype of significantly increased susceptibility to antibiotics. Similarly, we developed an antibody-based approach for biofilm disruption directed against the two-membered DNABII family of bacterial DNA-binding proteins, which serve as linchpins to stabilize the biofilm matrix. The incubation of biofilms with α-DNABII antibodies rapidly collapses them to induce a population of newly released bacteria (NRel).

Methods

In this study, we used a humanized monoclonal antibody (HuTipMab) directed against protective epitopes of a DNABII protein to determine if we could disrupt biofilms formed by the high-priority ESKAPEE pathogens as visualized by confocal laser scanning microscopy (CLSM) and COMSTAT2 analysis. Then, we demonstrated the potentiated killing of the induced NRel by seven diverse classes of traditional antibiotics by comparative plate count.

Results

To this end, ESKAPEE biofilms were disrupted by 50%-79% using a single tested dose and treatment period with HuTipMab. The NRel of each biofilm were significantly more sensitive to killing than their planktonically grown counterparts (heretofore, considered to be the most sensitive to antibiotic-mediated killing), even when tested at a fraction of the MIC (1/250-1/2 MIC). Moreover, the bacteria that remained within the biofilms of two representative ESKAPEE pathogens after HuTipMab disruption were also significantly more susceptible to killing by antibiotics.

Discussion

New data presented in this study support our continued development of a combinatorial therapy wherein HuTipMab is delivered to a patient with recalcitrant disease due to an ESKAPEE pathogen to disrupt a pathogenic biofilm, along with a co-delivered dose of an antibiotic whose ability to rapidly kill the induced NRel has been demonstrated. This novel regimen could provide a more successful clinical outcome to those with chronic, recurrent, or recalcitrant diseases, while limiting further contribution to AMR.

Corynebacterium Keratitis: Pure Versus Mixed Infection and Antibiotic Susceptibility Patterns From Different Tertiary Eye Care Centers

PURPOSE

The objective of this study was to compare the clinical and microbiological profiles of culture-proven pure Corynebacterium keratitis with mixed infection and their antibiotic susceptibility patterns over a 2-year period.

METHODS

A retrospective analysis of culture-proven cases of Corynebacterium keratitis over a 2-year period was performed in 3 different tertiary eye care centers. All isolates were tested for antibiotic susceptibility in vitro using the disc-diffusion method for 7 antibiotics.

RESULTS

Altogether 108 cases were identified as culture-positive Corynebacterium keratitis in 3 tertiary eye care centers. Of these, 60.2% (n = 65) and 39.8% (n = 43) of cases were due to pure Corynebacterium and mixed infection, respectively. The mean duration of symptoms was 23.2 ± 29.6 days. In the mixed-infection group, fungus was identified as the coexistent pathogen in 22 cases (51.1%). Ocular surface disorder was the most common risk factor (33.9%) in Corynebacterium keratitis. The most frequently isolated species was Corynebacterium amycolatum (22.2%) in both groups. Therapeutic keratoplasty was performed in 8.3% of cases. There was no significant difference in the outcome between the 2 groups. Cefazolin resistance was seen in 13.9% of patients, and all isolates were susceptible to vancomycin. The resistance pattern showed emerging resistance toward fluoroquinolone because the isolates were resistant to gatifloxacin (58.3%), moxifloxacin (47.2%), ciprofloxacin (54.6%), and ofloxacin (45.4%).

CONCLUSIONS

Ocular surface disorder is the most common risk factor in Corynebacterium keratitis. Although fluoroquinolones are commonly used as first-line therapy in microbial keratitis, the in vitro resistance pattern indicates that these are less likely to be effective in infection with Corynebacterium species.

Case Series: Unusual Presentation of Acanthamoeba Coinfection in the Cornea

SIGNIFICANCE

The cases illustrate Acanthamoeba coinfection with Pseudomonas aeruginosa or microsporidia in the cornea.

PURPOSE

This case series aimed to alert clinicians toward considering Acanthamoeba coinfection in the cornea when unusual presentation such as perineuritis or epitheliitis was observed in clinical images. Increased suspicion of Acanthamoeba coinfection may facilitate early diagnosis and prompt management, eventually leading to good vision outcomes.

CASE SERIES

An 11-year-old boy wearing orthokeratology lens for myopia control complained of pain in the right eye for 1 week. A paracentral corneal ulcer with perineuritis was observed. Culture from corneal tissue revealed P. aeruginosa , and an in vivo confocal microscopic examination showed highly reflective and oval-shaped structures indicating Acanthamoeba coinfection. Corneal lesions gradually improved under 0.02% polyhexamethylene biguanidine, 0.1% propamidine isethionate, and 0.3% ciprofloxacin. At 1 year, the final best-corrected visual acuity was 20/25 with residual paracentral corneal opacity. Another 20-year-old man complained of pain in the right eye for 2 weeks. Multiple raised corneal lesions associated with epitheliitis were found. Moreover, 1% acid-fast staining showed oval-shaped spores, and microsporidia infection was inferred. In addition, polymerase chain reaction results obtained after subjecting the patient to corneal debridement revealed positivity for Acanthamoeba . Polyhexamethylene biguanidine (0.02%) and 0.5% moxifloxacin were prescribed, and the lesions subsided. At a 2-year follow-up, the final best-corrected visual acuity was 20/25.

CONCLUSIONS

Perineuritis in orthokeratology lens wearers and epitheliitis without any predisposing factor are unusual presentations of Acanthamoeba coinfection in the cornea. These corneal findings should arouse the suspicion of coinfection and enable the clinicians to conduct the appropriate workup and initiate adequate treatment. This case series demonstrated that early diagnosis and prompt treatment can improve visual prognosis.

Update on diagnosis and management of refractory corneal infections

Infectious keratitis is a medical emergency resulting in significant visual morbidity. Indiscriminate use of antimicrobials leading to the emergence of resistant or refractory microorganisms has further worsened the prognosis. Coexisting ocular surface diseases, delay in diagnosis due to inadequate microbiological sample, a slow-growing/virulent organism, or systemic immunosuppressive state all contribute to the refractory response of the ulcer. With improved understanding of these varied ocular and systemic factors contributing to the refractory nature of the microbes, role of biofilm formation and recent research on improving the bioavailability of drugs along with the development of alternative therapies have helped provide the required multidimensional approach to effectively diagnose and manage cases of refractory corneal ulcers and prevent corneal perforations or further dissemination of disease. In this review, we explore the current literature and future directions of the diagnosis and treatment of refractory keratitis.

Bacterial keratitis: identifying the areas of clinical uncertainty

Bacterial keratitis is a common corneal infection that is treated with topical antimicrobials. By the time of presentation there may already be severe visual loss from corneal ulceration and opacity, which may persist despite treatment. There are significant differences in the associated risk factors and the bacterial isolates between high income and low- or middle-income countries, so that general management guidelines may not be appropriate. Although the diagnosis of bacterial keratitis may seem intuitive there are multiple uncertainties about the criteria that are used, which impacts the interpretation of investigations and recruitment to clinical studies. Importantly, the concept that bacterial keratitis can only be confirmed by culture ignores the approximately 50% of cases clinically consistent with bacterial keratitis in which investigations are negative. The aetiology of these culture-negative cases is unknown. Currently, the estimation of bacterial susceptibility to antimicrobials is based on data from systemic administration and achievable serum or tissue concentrations, rather than relevant corneal concentrations and biological activity in the cornea. The provision to the clinician of minimum inhibitory concentrations of the antimicrobials for the isolated bacteria would be an important step forward. An increase in the prevalence of antimicrobial resistance is a concern, but the effect this has on disease outcomes is yet unclear. Virulence factors are not routinely assessed although they may affect the pathogenicity of bacteria within species and affect outcomes. New technologies have been developed to detect and kill bacteria, and their application to bacterial keratitis is discussed. In this review we present the multiple areas of clinical uncertainty that hamper research and the clinical management of bacterial keratitis, and we address some of the assumptions and dogma that have become established in the literature.

An Evaluation of a Simplified Impression Membrane Sampling Method for the Diagnosis of Microbial Keratitis

The purpose of this study was to compare bacterial isolation rate using a corneal impression membrane (CIM) and a sharp instrument for obtaining corneal samples from patients with suspected microbial keratitis (MK). Data was retrospectively collected for all patients that had corneal samples taken for presumed MK between May 2014 and May 2020. Prior to May 2017 samples were collected by scraping the edges of the ulcer with a blade. From May 2017, samples were collected by placing a CIM (Millicell cell culture insert) against the ulcer. All corneal samples were processed using the same conventional diagnostic culture method. A total of 3099 corneal samples were included, of which 1214 (39.2%) were corneal scrapes and 1885 (60.9%) CIMs. Microorganisms were isolated from 235 (19.4%) and 1229 (65.2%) cases using a corneal scrape and CIM, respectively (p < 0.001). Of routinely described pathogenic microorganisms, there were significant increases in the isolations of S. aureus (2.4% to 11.3%) and Serratia (0.5% to 1.7%) using the CIM and no significant changes in the isolations of S. pneumoniae and P. aeruginosa. No significant differences were seen between the isolation rates of fungi or Acanthamoeba species. There was a significant increase in the isolation rates of other Streptococcal species (0.7% to 6.9%) and CNS species, specifically, S. epidermidis (2.1% to 26.2%), S. capitis (0.4% to 2.6%) and S. warneri (0.3% to 1.6%) using the CIM. The simplified CIM sampling method is an effective method for collecting corneal samples from patients with presumed MK in clinical practice.

Characterization of Polybacterial versus Monobacterial Conjunctivitis Infections in Pediatric Subjects Across Multiple Studies and Microbiological Outcomes with Besifloxacin Ophthalmic Suspension 0.6

Introduction

The choice of empiric therapy for bacterial conjunctivitis should be guided by an awareness of typical causative pathogen distributions. Bacterial conjunctivitis can be polybacterial, although pediatric-specific data are lacking.

Methods

This was a post-hoc analysis of data in pediatric subjects (1–17 years) from five bacterial conjunctivitis trials evaluating besifloxacin ophthalmic solution 0.6%.

Results

Of the 730 pediatric subjects with culture-confirmed conjunctivitis, nearly one-fourth (23.6%) had polybacterial infections and three-fourths (76.4%) had monobacterial infections at baseline. In both polybacterial and monobacterial infections, the most prevalent organisms were Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus, and Streptococcus mitis/S. mitis group. In polybacterial versus monobacterial infections, S. mitis/S. mitis group (8.7% vs 4.3%; P=0.032) and Moraxella catarrhalis (4.7% vs 0.5%; P<0.001) were identified more frequently, whereas S. pneumoniae (14.0% vs 28.1%; P<0.001) was identified less frequently, as the dominant infecting species. MICs for individual species were similar for tested antibiotics regardless of polybacterial or monobacterial infection, except Staphylococcus epidermidis for which fluoroquinolone MICs were ≥3 dilutions higher for isolates of this species sourced from polybacterial compared to monobacterial infections. Treatment with besifloxacin resulted in microbial eradication in 79.1% of polybacterial and 92.3% of monobacterial infections (P≤0.005 vs vehicle).

Discussion

One in four pediatric bacterial conjunctivitis infections is polybacterial, highlighting the need for a broad-spectrum antibiotic when choosing empiric therapy.

In Vitro Antibiotic Resistance among Bacteria from the Cornea in the Antibiotic Resistance Monitoring in Ocular MicRoorganisms Surveillance Study

PURPOSE

This study aimed to report on in vitro susceptibility patterns among corneal isolates collected in the Antibiotic Resistance Monitoring in Ocular micRoorganisms (ARMOR) study.

METHODS

Each year, from 2009 to 2019, Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Streptococcus pneumoniae, Pseudomonas aeruginosa, and Haemophilus influenzae isolates cultured from patients with ocular infections at participating ARMOR sites were submitted to a central laboratory for species confirmation and antibiotic susceptibility testing. In this analysis of corneal isolates, odds ratios for concurrent resistance were based on sample proportions, one-way ANOVA was used to evaluate resistance by patient age, and Cochran-Armitage tests were used to examine changes in antibiotic resistance over time.

RESULTS

A total of 1499 corneal isolates were collected from 61 sites over the 11-year period. Overall, 34.5% (148 of 429) of S. aureus and 41.9% (220 of 525) of CoNS isolates were methicillin resistant and had higher odds ratios for concurrent resistance to azithromycin (17.44 and 5.67), ciprofloxacin (39.63 and 12.81), and tobramycin (19.56 and 19.95), respectively, relative to methicillin-susceptible isolates (P < .001, all); also, a high proportion of methicillin-resistant S. aureus (85.1%) and methicillin-resistant CoNS (81.8%) were multidrug resistant (at least three classes of antibiotics). Resistance among S. pneumoniae isolates was highest for azithromycin (33.1%), whereas P. aeruginosa and H. influenzae isolates demonstrated low resistance overall. Among staphylococci, antibiotic resistance differed by patient age (S. aureus: F = 6.46, P < .001; CoNS: F = 4.82, P < .001), and few small changes in resistance (≤3.60% per year), mostly decreases, were observed over time.

CONCLUSIONS

Although rates of in vitro antibiotic resistance among presumed keratitis isolates obtained in ARMOR seemed stable between 2009 and 2019, resistance among staphylococci and pneumococci remains high (and should be considered when treating keratitis).

Polymicrobial Keratitis: Risk Factors, Clinical Characteristics, Bacterial Profile, and Antimicrobial Resistance

OBJECTIVE

To describe clinical characteristics, complications, and the most prevalent microorganisms causing polymicrobial keratitis and their antibiotic sensitivities.

METHODS

A cross-sectional study including a consecutive analysis of patient's records with a diagnosis of bacterial keratitis with a positive culture and antibiogram report were included. Patients were grouped into those having monomicrobial and polymicrobial infection. Features studied included demographic and clinical characteristics, risk factors, Gram stain, cultures, and antibiotic sensitivity.

RESULTS

We included 656 patients; in 31.5% more than one microorganism was found. Seven hundred and twenty-three gram-positive bacteria were isolated, and 336 (46.5%) had polymicrobial keratitis. One hundred sixty-one gram-negative bacteria were isolated, and 99 (61.5%) from polymicrobial keratitis. Fourteen (0.60%) patients presented ring infiltrate, and 10 (71.42%) of those patients had polymicrobial keratitis (X2 10.654, P=0.001). Multivariate analysis showed that patients with history of contact lens use (odds ratio [OR] of 1.78, P=0.042), coexistent autoimmune disease (OR 4.64, P=0.03), irregular edges of the infiltrate (OR 2.06, P=0.005), and ring infiltrate (OR 6.034, P=0.005) have a higher risk for developing polymicrobial infection. In the polymicrobial group, gram-positive and gram-negative organisms showed a high sensitivity to Netilmicin.

CONCLUSIONS

We found a high incidence of polymicrobial keratitis. Our results suggest that it should be suspected in patients with a history of contact lens use, coexistent autoimmune disease, infiltrates with indistinct edges, and ring infiltrates. Sensitivities to moxifloxacin are lower than those reported in previous studies, but sensitivity to Netilmicin is higher.

Clinical aspects and prognosis of polymicrobial keratitis caused by different microbial combinations: a retrospective comparative case study

PURPOSE

The purpose of this study is to compare the predisposing factors, clinical findings, treatment results, and prognosis for polymicrobial keratitis.

METHODS

In this retrospective comparative case study, we identified the cases of polymicrobial keratitis from the microbiological records (n = 649) at Balcalı Hospital, Çukurova University (Adana, Turkey; October 2010-2018). We included all the cases of infectious keratitis with two different types of microbial agents and grouped them as follows: group 1 (n = 25), bacterium-fungus coexistence; group 2 (n = 12), herpes simplex virus (HSV) or Acanthamoeba with bacterial infection; and group 3 (n = 7), HSV or Acanthamoeba with fungal infection. We compared the clinical and microbiological characteristics, and treatment outcomes among the groups.

RESULTS

In our study, we found that 44 infectious keratitis cases (6.7%) were of polymicrobial nature. The mean follow-up period was 11.4 ± 17.8 months. In total, 17 different bacteria along with 3 different fungi, HSV, and Acanthamoeba were isolated. The most common bacterium was Staphylococcus epidermidis (25%). Most of the fungal pathogens were filamentous. Patients with initial treatment failure and requiring surgical intervention had larger infiltrates (p = 0.023, p = 0.003, respectively) than other patients. Older age was associated with delayed recovery and poor visual prognosis.

CONCLUSIONS

Bacterial-fungus coexistence is the most common combination among patients, but other combinations should also be considered for suspected polymicrobial etiology. The corneal infiltrate size may be an important indicator of the course of disease and response to treatment. A closer and longer follow-up period should be planned for older patients.

Comparison of Clinical Features and Treatment Outcomes of Pseudomonas aeruginosa Keratitis in Contact Lens and Non-Contact Lens Wearers

PURPOSE

To compare the outcomes of Pseudomonas aeruginosa keratitis (PAK) in contact lens wearers (CLWs) and non-contact lens wearers (non-CLWs) and identify risk factors for poor visual acuity (VA) outcomes in each group.

DESIGN

Retrospective cohort study METHODS: Two hundred fourteen consecutive cases of PAK were included between January 2006 and December 2019. Clinical features, microbiologic results, and treatment course were compared between CLW and non-CLW groups. Analyses of clinical features predicting poor final VA were performed.

RESULTS

This study identified 214 infected eyes in 207 patients with PAK, including 163 eyes (76.2%) in CLWs and 51 eyes (23.8%) in non-CLWs. The average age was 39.2 years in CLWs and 71.9 years in non-CLWs (P < .0001). The average logMAR visual acuity (VA) at presentation was 1.39 in CLWs and 2.17 in non-CLWs (P < .0001); average final VA was 0.76 in CLWs and 1.82 in non-CLWs (P < .0001). Stromal necrosis required a procedural or surgical intervention in 13.5% of CLWs and 49.0% of non-CLWs (P < .0001). A machine learning-based analysis yielded a list of clinical features that most strongly predict a poor VA outcome (worse than 20/40), including worse initial VA, older age, larger size of infiltrate or epithelial defect at presentation, and greater maximal depth of stromal necrosis.

CONCLUSIONS

Non-CLWs have significantly worse VA outcomes and required a higher rate of surgical intervention, compared with CLWs. Our study elucidates risk factors for poor visual outcomes in non-CLWs with PAK.

Acanthamoeba Keratitis Versus Mixed Acanthamoeba and Bacterial Keratitis: Comparison of Clinical and Microbiological Profiles

PURPOSE

To compare the clinical profiles and outcomes of patients with Acanthamoeba keratitis with or without mixed bacterial infection.

METHODS

A retrospective analysis of microbiologically confirmed AK cases presenting to a tertiary care center over a 9-year period was conducted. Fourteen eyes in the coinfected group (group 1) and 24 eyes in the AK group (group 2) were analyzed to study the differences in these 2 groups of patients. The cases were diagnosed using a conventional microscopic analysis with staining techniques confirmed by cultural methods and were treated, which tailored to the microbiology report.

RESULTS

There was no difference in the demographic profile and presenting features in the 2 groups. Duration of symptoms and history of ocular trauma, contact lens wear, and previous steroid usage were also similar for both the groups. Dense central corneal infiltrate was the common presentation for both groups (7/14 vs. 16/24 in group 1 vs. group 2). Epithelial defect without dense stromal infiltrate was significantly more common in group 1 (42.9% vs. 4.2%, P = 0.003) as a presenting clinical feature. Hypopyon was present in 8/14 of group 1 versus 9/24 of group 2 eyes (P = 0.25). No significant difference was found in the final visual acuity in pure and mixed AK cases, and the need for surgical intervention was comparable. The most common bacterial pathogen isolated in the mixed group was the Staphylococcus species.

CONCLUSIONS

Bacterial coinfection is common in patients with Acanthamoeba keratitis. Coinfection did not point toward a worse clinical disease at presentation or outcome.

Diagnostic approach and epidemiology of Microbial Keratitis: findings from an Italian Tertiary Care center

Rapid identification of causative microorganisms of microbial keratitis (MK) and knowledge of the most common local pathogens are prerequisites for rational antimicrobial therapy. We retrospectively reviewed the characteristics of MK diagnosed at the IRCCS Arcispedale Santa Maria Nuova of Reggio Emilia (Italy) in a 5-years period, where the Ophthalmologist Unit is a reference center for corneal infections. During the study period, 183 MK were evaluated through corneal scrapings cultures. The positivity rate was 54,1%. A total of 107 microorganisms have been isolated: Acanthamoeba species was the etiologic agent in 19 cases. Pseudomonas aeruginosa and Staphylococcus aureus were more frequently isolated in bacterial keratitis, while Fusarium spp., Candida albicans, and Alternaria alternata were predominant among the fungal isolates. Strict cooperation between ophthalmologists and clinical microbiologists is advisable to allow the best diagnostic approach for MK.

Proteus mirabilis Keratitis: Risk Factors, Clinical Features, Treatment Outcomes, and Microbiological Characteristics

PURPOSE

To characterize the risk factors, clinical presentations, management choices, and outcomes of Proteus mirabilis keratitis.

METHODS

In this retrospective study, 26 culture-proven cases of P. mirabilis infections were diagnosed and treated between 1998 and 2019 at the University of Pittsburgh Medical Center. Medical records were available for 14 keratitis cases and were reviewed for demographic information, ocular risk factors, and treatment outcomes.

RESULTS

Sixteen eyes of 14 patients were included in the study. The average age was 47.8 ± 19.3 years, with a median follow-up time of 6 months. The most common ocular risk factors were poor ocular surface and contact lens use in 57.1% and 42.9% of cases, respectively. Eleven of the 14 patients (78.6%) had positive corneal cultures, and 13 of the 14 patients (92.9%) had positive conjunctiva or eyelid cultures. All isolates were susceptible to ciprofloxacin, ofloxacin, moxifloxacin, gatifloxacin, and cefazolin. Surgical intervention was required in 4 patients (28.6%). Average LogMAR visual acuity was 1.3 ± 1.0 at presentation and 0.9 6 ± 1.0 at the most recent follow-up visit.

CONCLUSIONS

Proteus mirabilis is an uncommon cause of microbial keratitis. Patients with poor ocular surface and those who use contact lens are at increased risk for developing this cause of keratitis. Empiric treatment with fortified antibiotics or fluoroquinolones seemed to provide effective coverage for P. mirabilis.

Clinical Features and Management of Stenotrophomonas Maltophilia Keratitis

Introduction

Stenotrophomonas maltophilia keratitis is an uncommon infectious disease of the cornea. The clinical features, antibiotic susceptibility, and clinical outcomes of S. maltophilia keratitis were investigated in this study.

Methods

Between January 2015 and February 2020, the medical records of 16 patients with culture-proven S. maltophilia-associated infectious keratitis were retrospectively reviewed. Clinical data were analyzed regarding risk factors, clinical presentation, antibiotic susceptibility, and clinical outcomes.

Results

The average age of the patients was 56.24 ± 24.84 years. The most common risk factors for S. maltophilia keratitis were trauma (6/16, 37.5%), use of contact lenses (6/16, 37.5%), and herpes simplex virus keratitis (3/16, 18.8%), which caused ocular instability. Regarding the antibiotic sensitivities, most isolates (15/16, 93.8%) were susceptible to fluoroquinolones, 87.5% (14/16) of them to aminoglycosides, and 81.3% (13/16) of them to beta-lactams. Patients were classified into two groups according to the initial antibiotic eye drops, and there were significant differences in the final visual acuity between two groups: mixed fluoroquinolone, beta-lactam, aminoglycoside group, and mixed beta-lactam and aminoglycoside groups (p = 0.039).

Conclusion

Ocular infection due to S. maltophilia is an opportunistic infection followed by instability of the ocular surface. In cases of S. maltophilia infection, mixed use of fluoroquinolone, beta-lactam, and aminoglycoside should be considered for treatment of choice.

Infectious keratitis: an update on epidemiology, causative microorganisms, risk factors, and antimicrobial resistance

Corneal opacity is the 5th leading cause of blindness and visual impairment globally, affecting ~6 million of the world population. In addition, it is responsible for 1.5-2.0 million new cases of monocular blindness per year, highlighting an ongoing uncurbed burden on human health. Among all aetiologies such as infection, trauma, inflammation, degeneration and nutritional deficiency, infectious keratitis (IK) represents the leading cause of corneal blindness in both developed and developing countries, with an estimated incidence ranging from 2.5 to 799 per 100,000 population-year. IK can be caused by a wide range of microorganisms, including bacteria, fungi, virus, parasites and polymicrobial infection. Subject to the geographical and temporal variations, bacteria and fungi have been shown to be the most common causative microorganisms for corneal infection. Although viral and Acanthamoeba keratitis are less common, they represent important causes for corneal blindness in the developed countries. Contact lens wear, trauma, ocular surface diseases, lid diseases, and post-ocular surgery have been shown to be the major risk factors for IK. Broad-spectrum topical antimicrobial treatment is the current mainstay of treatment for IK, though its effectiveness is being challenged by the emergence of antimicrobial resistance, including multidrug resistance, in some parts of the world. In this review, we aim to provide an updated review on IK, encompassing the epidemiology, causative microorganisms, major risk factors and the impact of antimicrobial resistance.

Melting corneal ulcers (keratomalacia) in dogs: A 5-year clinical and microbiological study (2014-2018)

OBJECTIVES

To identify bacterial microorganisms associated with canine keratomalacia, review their antimicrobial sensitivity, and evaluate clinical outcomes compared to results of microbial culture.

METHODS

Retrospective analysis of clinical records of dogs diagnosed with a melting corneal ulcer presented to a referral hospital in Hertfordshire, UK between 2014 and 2018.

RESULTS

One hundred and ten melting corneal ulcers were sampled in 106 dogs. The most common pure bacterial isolate was Pseudomonas aeruginosa (n = 26) followed by β-hemolytic Streptococcus (n = 12). Melting corneal ulcers that cultured coagulase-positive Staphylococcus, coliform bacteria, Pasteurella multocida, Enterococcus, and Streptococcus viridans presented in smaller numbers and were analyzed together (n = 16). Multiple cultures were identified in nine cases (n = 9). Forty-seven cultures yielded no bacterial growth (n = 47). The susceptibility to fluoroquinolones remained high with the exception of β-hemolytic Streptococci. There was no significant difference in the ulcer severity at presentation in regard to the cultured bacteria. Overall, 63 eyes (57%) received surgical grafting in addition to medical treatment. In 14 cases (13%), the progression of corneal melting despite medical ± surgical treatment resulted in enucleation. Fifty-seven percent (8/14) of the enucleated eyes cultured pure Pseudomonas aeruginosa isolates. In contrast, all β-hemolytic Streptococcus-associated ulcers healed.

CONCLUSIONS

The most common bacterial species associated with canine keratomalacia were Pseudomonas aeruginosa and β-hemolytic Streptococcus. Because of the variation in antibacterial sensitivity between these two species, bacterial culture and sensitivity testing should be performed in all dogs presenting with keratomalacia. Melting corneal ulcers associated with pure Pseudomonas infection were significantly more likely to result in globe loss than melting corneal ulcers associated with other cultures.

Procedures, Visits, and Procedure Costs in the Management of Microbial Keratitis

PURPOSE

To investigate the burden of procedures, visits, and procedure costs in the management of microbial keratitis (MK).

METHODS

Medical records of patients from an academic hospital outpatient facility between December 2013 and May 2018 were retrospectively reviewed. Patients were included if they were older than the age of 18 years, recruited for study of likely MK, and not concurrently undergoing treatment for other acute eye conditions. For procedural costs, Medicare data for billing were obtained using the Center for Medicare and Medicaid Services Physician Fee Lookup tool.

RESULTS

A total of 68 patients were included for analysis. Patients were on average 51.3 years (SD = 19.5), 55.9% women (n = 38), and 89.7% White (n = 61). Per person, the average number of procedures was 2.9 (SD = 4.2). The average number of visits was 13.9 (SD = 9.2) over an average of 26.9 weeks (SD = 24.3). Age (P < 0.0001), positive Gram stain (P = 0.03), and mixed Gram stain (P = 0.002) were positively associated with the number of procedures. Age (P = 0.0003), fungal keratitis (P = 0.02), and mixed Gram stain (P = 0.01) were positively associated with the number of visits. Race was inversely associated with the number of procedures (P = 0.045) and visits (0.03). Patients with bacterial keratitis were more likely to have amniotic membrane grafts (P = 0.01) and tarsorrhaphies (P = 0.03) than fungal patients. Across all procedures performed for the management of MK, the mean cost per patient was $1788.7 (SD = $3324.62).

CONCLUSIONS

Patients incur many procedural costs and attend many visits during the management of MK. These findings emphasize the importance of patient-provider communication for frequent follow-up care and the potential need to perform procedures for disease management.

Current understanding and therapeutic management of contact lens associated sterile corneal infiltrates and microbial keratitis

Contact lenses are widely prescribed in clinical practice with multiple applications and advantages. However, contact lenses can be associated with various complications which range from innocuous to severe. Clinicians thus not only need to possess the ability to prescribe the most appropriate contact lenses for each individual patient but also be able to recognise and manage any associated complications. This review examines the existing literature on the management of corneal infiltrative events associated with soft contact lenses, including microbial keratitis, particularly in the context of practising in Australia. The definitions and diagnosis of corneal infiltrative events, as well as the current understanding of their aetiologies, will be explored. The various aspects of a successful management will be discussed, including the applications of therapeutic agents such as antimicrobial and anti-inflammatory agents, the role of microbiological investigations, and strategies to improve long-term prognosis. The currently available evidence supporting management options will be presented, highlighting the relative abundance of high-level evidence on management protocols, antimicrobial selection and treatment duration for microbial keratitis; and the relative paucity of studies and trials for sterile corneal infiltrative events, despite this condition being much more commonly encountered in clinical practice.

12-year analysis of incidence, microbiological profiles and in vitro antimicrobial susceptibility of infectious keratitis: the Nottingham Infectious Keratitis Study

BACKGROUND/AIMS

To examine the incidence, causative microorganisms and in vitro antimicrobial susceptibility and resistance profiles of infectious keratitis (IK) in Nottingham, UK.

METHODS

A retrospective study of all patients who were diagnosed with IK and underwent corneal scraping between July 2007 and October 2019 (a 12-year period) at a UK tertiary referral centre. Relevant data, including demographic factors, microbiological profiles and in vitro antibiotic susceptibility of IK, were analysed.

RESULTS

The estimated incidence of IK was 34.7 per 100 000 people/year. Of the 1333 corneal scrapes, 502 (37.7%) were culture-positive and 572 causative microorganisms were identified. Sixty (4.5%) cases were of polymicrobial origin (caused by ≥2 different microorganisms). Gram-positive bacteria (308, 53.8%) were most commonly isolated, followed by Gram-negative bacteria (223, 39.0%), acanthamoeba (24, 4.2%) and fungi (17, 3.0%). Pseudomonas aeruginosa (135, 23.6%) was the single most common organism isolated. There was a significant increase in Moraxella spp (p<0.001) and significant decrease in Klebsiella spp (p=0.004) over time. The in vitro susceptibilities of Gram-positive and Gram-negative bacteria to cephalosporin, fluoroquinolone and aminoglycoside were 100.0% and 81.3%, 91.9% and 98.1%, and 95.2% and 98.3%, respectively. An increase in resistance against penicillin was observed in Gram-positive (from 3.5% to 12.7%; p=0.005) and Gram-negative bacteria (from 52.6% to 65.4%; p=0.22).

CONCLUSION

IK represents a relatively common and persistent burden in the UK and the reported incidence is likely underestimated. Current broad-spectrum antimicrobial treatment provides a good coverage for IK, although challenged by some level of antimicrobial resistance and polymicrobial infection.

Successful Control of a Co-Infection Caused by Candida albicans and Pseudomonas aeruginosa in Keratitis

Nowadays, the co-infection of different classes of pathogens is a major concern. The objective of this study was to develop a successful therapy for keratitis caused by the co-infection of Candida sp. with Pseudomonas sp, which is difficult to cure. The study is based on a 47 years old male farmer showing redness and watering in the right eye for 15-days. ; Methods: The microbiological examination was performed to isolate the causative organisms, i.e. Pseudomonas aeruginosa and Candida albicans. They were cultured separately along with their co-culture and treated with ciprofloxacin and amphotericin B during the growing stage to predict a definite cure. ; Results: Scanning electron microscope (SEM) results confirmed the inter-specific interaction between the two different types of microorganisms. Amphotericin-B and Ciprofloxacin showed the least MIC value for both organisms in co-culture. ; Conclusion: Treatment with Amphotericin-B and 5% ciprofloxacin effectively hindered the growth of Pseudomonas aeruginosa and Candida albicans, the co-infection of which caused keratitis. This therapy may be successfully implied for such cases of co-infection in the future.

16S Ribosomal RNA PCR Versus Conventional Diagnostic Culture in the Investigation of Suspected Bacterial Keratitis

Purpose

The purpose of this study was to compare conventional diagnostic culture (CDC) to 16S ribosomal RNA polymerase chain reaction (PCR) analysis for diagnosing bacterial keratitis.

Methods

Samples collected from 100 consecutive patients presenting to the Royal Liverpool University Hospital with bacterial keratitis were processed using CDC and 16S PCR analysis.

Results

The overall detection rate using both methods was 36%. Of these, 72.2% (26/36) were detected by PCR and 63.9% (23/36) isolated by CDC (P = 0.62). Using a combination of both PCR and CDC increased the detection rate for pathogenic bacteria by 13% compared to using CDC alone (P = 0.04). In CDC negative samples, 16S PCR identified more pathogens than CDC in 16S PCR negative samples. Neither order of sample collection nor prior antimicrobial use affected the detection rate.

Conclusions

16S rRNA gene PCR performed in addition to CDC on corneal samples from patients with clinically suspected bacterial keratitis led to additional pathogen detection.

Translational Relevance

16S rRNA gene PCR should be developed to become an additional part of clinical service for patients with bacterial keratitis rather than used in isolation.

Characterization of baseline polybacterial versus monobacterial infections in three randomized controlled bacterial conjunctivitis trials and microbial outcomes with besifloxacin ophthalmic suspension 0.6

Background/Purpose

To date, studies examining polymicrobial infections in ocular disease have mostly been limited to keratitis or endophthalmitis. We characterized polybacterial infections compared to monobacterial infections in prior clinical studies evaluating besifloxacin ophthalmic suspension 0.6% for the treatment of bacterial conjunctivitis and report on associated microbiological outcomes.

Methods

In this post-hoc analysis, microbiological data for subjects with conjunctivitis due to one or more than one bacterial species in three previous studies (two vehicle-, one active-controlled) of besifloxacin were extracted. Bacterial species identified at baseline were deemed causative if their colony count equaled or exceeded species-specific prespecified threshold criteria. In subjects with polybacterial infections, the fold-increase over threshold was used to rank order the contribution of individual species. Baseline pathogens and their minimum inhibitory concentrations (MICs) for common ophthalmic antibiotics were compared by infection type, as were microbial eradication rates following treatment with besifloxacin.

Results

Of 1041 subjects with culture-confirmed conjunctivitis, 17% had polybacterial and 83% had monobacterial conjunctivitis at baseline. In polybacterial compared to monobacterial infections, Haemophilus influenzae and Streptococcus pneumoniae were identified less frequently as the dominant infecting species (P = 0.042 and P<0.001, respectively), whereas Streptococcus mitis/S. mitis group was identified more frequently as dominant (P<0.001). Viral coinfection was also identified more frequently in polybacterial infections (P<0.001). Staphylococcus aureus was the most common coinfecting species in polybacterial infections and the second most common dominant species in such infections. With few exceptions, MICs for individual species were comparable regardless of infection type. Clinical microbial eradication rates with besifloxacin were high regardless of infection type (P≤0.016 vs vehicle at follow-up visits).

Conclusions

Approximately one in five subjects with bacterial conjunctivitis are infected with more than one bacterial species underscoring the need for a broad-spectrum antibiotic for such infections. Besifloxacin treatment resulted in robust eradication rates of these infections comparable to monobacterial infections.

Trial registration

NCT000622908, NCT00347932, NCT00348348

Antimicrobial susceptibility of isolated pathogens from patients with contact lens-related bacterial keratitis in Crete, Greece: A ten-year analysis

PURPOSE

To evaluate the bacterial spectrum and antimicrobial susceptibilities of pathogens isolated from contact lens-related bacterial keratitis cases in a large academic Greek hospital.

METHODS

All adult patients with positive corneal scrapings or contact lens culture between 2007 and 2016 at the University Hospital of Heraklion, Greece, were retrospectively identified through a local microbiology database and their medical records were reviewed.

RESULTS

A total of 240 isolates were recovered from 131 patients with culture-proven contact lens-associated bacterial keratitis. The most common microorganism identified was Serratia marcescens (17.1% of total isolates), followed by Pseudomonas aeruginosa, Klebsiella spp. and coagulase-negative staphylococci (CoNS). Rates of aztreonam-resistant P. aeruginosa and erythromycin-resistant CoNS decreased in recent years, while the decrease in oxacillin-resistant CoNS was statistically significant (p=0.009). More than 90% of the isolated organisms (S. marcescens, P. aeruginosa, Klebsiella spp. and CoNS) were susceptible to ciprofloxacin or gentamicin.

CONCLUSION

Gram-negative microorganisms are the most common causative pathogens of contact lens-related keratitis in the region of Crete. Topical antibacterials containing quinolones or gentamicin represent an effective empirical treatment for the majority of the cases. This is quite encouraging, considering that the present study was conducted in a country characterised by high antimicrobial resistance rates. However, culture-driven antimicrobial treatment is mandatory for this sight-threatening infection.

Microbial keratitis in Sydney, Australia: risk factors, patient outcomes, and seasonal variation

PURPOSE

To provide recent data on patient demographics, clinical profile and outcomes of patients with microbial keratitis over a 5-year period at the Sydney Eye Hospital, and to identify seasonal variations of the main causative organisms.

METHOD

A retrospective study of patients with a clinical diagnosis of microbial keratitis and corneal scrape performed between 1 January 2012 and 31 December 2016. Clinical information was gathered from medical records and pathology data.

RESULTS

One thousand fifty-two eyes from 979 patients with a mean age of 54.7 ± 21.5 years (range 18-100 years) were included. The majority of cases were bacterial (65%) followed by polymicrobial (2.4%), fungi (2.3%), and culture-negative (31%). Common risk factors for microbial keratitis were contact lens wear (63%) and previous topical steroid use (24%). Factors significantly associated with poor patient outcomes in the multivariate model were age, visual acuity, and epithelial defect size (p < 0.05). Patients with fungal or polymicrobial keratitis presented with worse clinical features at initial and final presentation (p < 0.05). There was a significant variation in the occurrence of Pseudomonas aeruginosa (p = 0.018) and fungal keratitis (predominately made up of Candida and Fusarium species) (p = 0.056) in the hottest seasons.

CONCLUSION

Poorer outcomes are more likely to be seen in older patients and those presenting with poor visual acuity and large epithelial defects at the initial presentation.

Clinical diagnosis and treatment of rare painless keratitis caused by three pathogens: clinical practice and experiential discussion

There have been numerous reports regarding the occurrence of keratitis in patients with soft contact lenses, but few reports in patients with rigid gas permeable contact lenses. To the best of our knowledge, the occurrence of infection associated with three species of pathogens has never been reported. Here, we describe a patient who exhibited refractory painless keratitis caused by three pathogens (Staphylococcus epidermidis, Acanthamoeba, and herpes simplex virus) and summarize similar reports published at multiple centers worldwide, with the aim of providing guidance for clinicians who might encounter mixed-type corneal infections. We describe the results of many ophthalmologic and laboratory investigations, which guided our treatment selection. We achieved good treatment efficacy, such that the patient exhibited a corrected visual acuity of 20/20 in the affected eye after a series of treatments, including curettage of ulcer lesions. Corneal infections caused by multiple pathogens are challenging in clinical practice. This summary of our experience in patient diagnosis and treatment can help clinicians to achieve a favorable prognosis in treatment of future patients.

"It Takes a Village": Mechanisms Underlying Antimicrobial Recalcitrance of Polymicrobial Biofilms

Chronic infections are frequently caused by polymicrobial biofilms. Importantly, these infections are often difficult to treat effectively in part due to the recalcitrance of biofilms to antimicrobial therapy. Emerging evidence suggests that polymicrobial interactions can lead to dramatic and unexpected changes in the ability of antibiotics to eradicate biofilms and often result in decreased antimicrobial efficacy in vitro In this review, we discuss the influence of polymicrobial interactions on the antibiotic susceptibility of biofilms, and we highlight the studies that first documented the shifted antimicrobial susceptibilities of mixed-species cultures. Recent studies have identified several mechanisms underlying the recalcitrance of polymicrobial biofilm communities, including interspecies exchange of antibiotic resistance genes, β-lactamase-mediated inactivation of antibiotics, changes in gene expression induced by metabolites and quorum sensing signals, inhibition of the electron transport chain, and changes in properties of the cell membrane. In addition to elucidating multiple mechanisms that contribute to the altered drug susceptibility of polymicrobial biofilms, these studies have uncovered novel ways in which polymicrobial interactions can impact microbial physiology. The diversity of findings discussed highlights the importance of continuing to investigate the efficacy of antibiotics against biofilm communities composed of different combinations of microbial species. Together, the data presented here illustrate the importance of studying microbes as part of mixed-species communities rather than in isolation. In light of our greater understanding of how interspecies interactions alter the efficacy of antimicrobial agents, we propose that the methods for measuring the drug susceptibility of polymicrobial infections should be revisited.

Disease patterns of microbial keratitis in Singapore: A retrospective case series

PURPOSE

To investigate the disease patterns of Microbial Keratitis(MK) in patients seen in a tertiary referral hospital, to evaluate the clinical outcomes of MK and the risk factors for poorer visual outcomes.

METHODS

This is a retrospective case series of all culture-positive corneal scrapings between April 2012 and October 2016. A total of 230 patients(n = 230) were included into this study. Patient demographics, clinical information and microbiological characteristics of organisms are collected.

RESULTS

64.3% of patients with MK are contact lens(CL) users. Among CL users, there is a preponderance of females(68.9%) and they tend to be younger (27.1 ± 10.6 years). The most frequently isolated organism in this study is Pseudomonas aeruginosa(51.7%) with 69.6% of cases belonging to CL users. MK in non-CL users tend to involve other organisms, such as coagulase-negative Staphylococci, Staphylococcus aureus and Streptococcus pneumoniae. Pseudomonas aeruginosa exhibits good sensitivity rates to ciprofloxacin, levofloxacin and gentamicin. Non-Pseudomonas organisms display similar sensitivities to ciprofloxacin, levofloxacin and gentamicin. MK in non-CL users is related to predisposing factors of prior ocular trauma and concomitant ocular pathology. They tend to have worse visual acuity(VA) on presentation and after treatment compared to CL users. Poorer VA outcome is associated with larger ulcers, increasing age, trauma and non-CL wearers. Successful clinical outcome is achieved in 97.8% of patients, with only 2.2% requiring further surgical intervention.

CONCLUSION

CL use alters the disease patterns of MK as well as the underlying microbiological etiology. Fluoroquinolones and aminoglycosides are good empirical antibiotics for MK treatment. Early referral to a tertiary centre will likely allow for earlier treatment, which can result in better VA outcome, especially so in patients who are older, non-CL wearers and have larger ulcers with associated trauma.

Infectious Keratitis: Microbiological Review of 297 Cases

Infectious keratitis is a serious ocular infection that can lead to loss of vision. The aim of this study was to investigate the microbiological characteristics of this infection at the University Hospital of Guadalajara (Spain). We retrospectively reviewed all cases diagnosed between January 2010 and December 2016. During the 7-year study period, 297 corneal scrapes corresponding to 298 patients were performed. Antibiotic treatment prior to the culture was administered in 59 cases (19.9%). Contact lens wear was the most common risk factor (33.2%). Bacterial keratitis accounted for 64.6% of cases, viral keratitis for 3.4%, and fungal keratitis for 1%. A total of 241 bacterial strains were identified. Gram-positive isolates represented 87.1%, and gram-negative 12.7%. Coagulase-negative Staphylococcus strains were the most common microorganisms isolated (30.3%). When gram-positive microorganisms were analyzed, the sensitivity prevalence rates for vancomycin (VCM), levofloxacin, gentamicin (GM), and tobramycin (TO) were 99.4%, 84.6%, 87.9%, and 88.3%, respectively. For the gram-negative organisms, the sensitivity prevalence rates for ceftazidime, ciprofloxacin, GM, and TO were 83.3%, 93.5%, 96.3%, and 100%, respectively. Our study revealed strong predominance of gram-positive microorganisms. We suggest empirically treating bacterial keratitis originating in our area with VCM and TO, especially severe bacterial keratitis and pretreated cases in the community without a clinical response.

Contact lens-related polymicrobial keratitis: Acanthamoeba spp. genotype T4 and Candida albicans

A 31-year-old female daily user of contact lenses sought medical attention, reporting blurred vision and irritation of the left eye. Slit-lamp examination revealed hyperemia and an irregular corneal epithelium surface, and empirical treatment was started. A corneal scrape was obtained and examined for the presence of fungi, bacteria, and Acanthamoeba spp. The results of the microbial culture revealed growth of Acanthamoeba spp. and Candida albicans. The Acanthamoeba isolate was characterized by cyst morphology as belonging to group II according to Pussard and Pons. Sequencing of the diagnostic fragment 3 (DF3) region located on the 18S ribosomal DNA identified the isolate as genotype T4. The patient was treated with chlorhexidine 0.02% and polyhexamethylene biguanide (PHMB) 0.02% drops for 5 months until the infection resolved. Lately, rare cases of polymicrobial keratitis associated with Acanthamoeba and Candida albicans have been reported. Cases of co-infection are more difficult to treat, since the specific treatment depends on precise identification of the agents involved.

Clinical Characteristics of Stenotrophomonas maltophilia Keratitis

PURPOSE

Stenotrophomonas maltophilia is an important opportunistic pathogen but an uncommon cause of corneal infections. This study aimed to report the clinical features, antibiotic susceptibility, treatments, and visual outcomes of S. maltophilia keratitis.

METHODS

The medical records of 21 patients with culture-proven S. maltophilia-associated infectious keratitis in our hospital between January 1, 2003, and December 31, 2014, were retrospectively reviewed. The clinical features of patients with S. maltophilia keratitis were compared with those of patients from 17 previously reported cases.

RESULTS

The most common risk factors for S. maltophilia keratitis were preexisting corneal disease or previous corneal surgery (16), followed by soft contact lens wear (9). Nine patients (42.9%) were multifactorial. Polymicrobial infections was detected in 12 eyes (57.1%). All S. maltophilia isolates were susceptible to levofloxacin and moxifloxacin. A total of 17 of 21 patients (81.0%) had favorable responses to topical antimicrobial treatment, and 10 (47.6%) required surgical intervention for promotion of reepithelialization (6) and corneal perforation (4). Final vision ranged from light perception to 20/20. The clinical features of S. maltophilia keratitis in our cases and in previously reported cases were similar.

CONCLUSIONS

S. maltophilia keratitis primarily affects patients with compromised ocular surfaces. S. maltophilia demonstrates in vitro susceptibility and a strong clinical response to fluoroquinolones.

[Diagnostic and therapeutic contribution of microbiological analysis in severe microbial keratitis at Reims University Hospital between 2012 and 2014]

PURPOSE

To investigate the contribution of microbial analysis in the diagnosis and management of severe microbial keratitis.

MATERIAL AND METHOD

This is a monocentric retrospective study at the University Hospital of Reims from January 2012 to December 2014. Corneal scrapings with infectious keratitis were subjected to routine bacterial and fungal culture. PCR was also performed to detect various viral DNA (VZV, CMV, EBV, HSV 1 & 2, adenovirus) and Acanthamoeba sp. DNA. All contact lens cases were analyzed if available.

RESULTS

One hundred and six patients were hospitalized, including 30 contact lens wearers (28.3%). Sixty-four bacterial cultures were positive (68%). Twenty-five different bacterial species were identified with a majority of gram-positive bacteria (67.92%). Among contact lens wearers, the initial VA was better than non-wearers (P=0.0004) and 37% of bacteria identified (a plurality) were gram positive. Of 11 contact lens case analyzed, in only one case (3.3%) did the result correlate with the corneal culture. Only 9 samples from the 323 viral DNA extractions and real time PCR were positive (2.8%); 7 were HSV1. No prior antiviral therapy had been started. Fungal culture was positive in 2 of the 97 corneal samples taken and 63.6% of the contact lens cases (7/11 cases). Only one of the 40 Acanthamoeba sp. PCR's was positive.

CONCLUSION

The systematic performance of microbiological investigations is a good diagnostic approach given the polymorphism of clinical presentations of corneal ulcers, which can sometimes be extremely misleading. Culture of contact lens cases appears ineffective for the detection and determination of the causative microorganism. The high incidence of Staphylococcus in bacterial keratitis and the prevalence of infections with gram-positive bacteria in contact lens wearers were noted.

Peptoid Efficacy against Polymicrobial Biofilms Determined by Using Propidium Monoazide-Modified Quantitative PCR

Biofilms containing Candida albicans are responsible for a wide variety of clinical infections. The protective effects of the biofilm matrix, the low metabolic activity of microorganisms within a biofilm and their high mutation rate, significantly enhance the resistance of biofilms to conventional antimicrobial treatments. Peptoids are peptide‐mimics that share many features of host defence antimicrobial peptides but have increased resistance to proteases and therefore have better stability in vivo. The activity of a library of peptoids was tested against monospecies and polymicrobial bacterial/fungal biofilms. Selected peptoids showed significant bactericidal and fungicidal activity against the polymicrobial biofilms. This coupled with low cytotoxicity suggests that peptoids could offer a new option for the treatment of clinically relevant polymicrobial infections.

Comparison Between Polymicrobial and Fungal Keratitis: Clinical Features, Risk Factors, and Outcome

PURPOSE

To compare the clinical features, risk factors, and outcome of polymicrobial keratitis with monomicrobial keratitis due to fungus.

DESIGN

Retrospective, comparative interventional case series.

METHODS

Consecutive cases of microbial keratitis with significant growth of more than 1 organism in culture and culture-proven fungal keratitis treated with natamycin alone were retrieved from the microbiology department. Complete success was defined as resolution of the infiltrate with scar formation on medical treatment, partial success as resolution following tissue adhesive application, and failure as inadequate response to medical therapy with increasing infiltrate size, corneal melting, and/or perforation necessitating therapeutic penetrating keratoplasty (PKP) or evisceration.

RESULTS

There were 34 eyes of 34 patients with polymicrobial keratitis and 60 cases of fungal keratitis. Compared to patients with fungal keratitis, patients with polymicrobial keratitis were significantly older (50.03 ± 9.81 years vs 42.79 ± 12.15 years, P = .0038), with larger infiltrates at presentation (61.8% vs 24.1%, P = .0007), a higher association with endophthalmitis (11.8% vs 0%, P = .03), previous history of corneal graft (20.6% vs 0%, P = .0012), and prior topical corticosteroid use (23.5% vs 5%, P = .019). In the polymicrobial group, a combination of bacteria and fungus was more frequently isolated (23, 67.6%), among which filamentous fungi (25, 39.1%) and coagulase-negative staphylococci (14, 21.9%) comprised a majority. Complete success was significantly lower in the polymicrobial group compared to the fungal keratitis group (39.3% vs 73.7%, P = .0045). In multivariate logistic regression analysis comparing factors affecting the outcome between the 2 groups, older age (P = .027) and ulcers larger than 6 mm (P = .001) at presentation adversely affected outcome.

CONCLUSIONS

Polymicrobial keratitis with fungus and bacteria was more common and more challenging to treat, with a poorer outcome than fungal keratitis. Medical treatment may be effective; however, therapeutic PKP provided globe salvage at best. Early PKP may be advocated for larger ulcers at presentation.