Spectrum and Sensitivity of Bacterial Keratitis Isolates in Auckland

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

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

Preclinical confirmation of UVC efficacy in treating infectious keratitis

PURPOSE

Preclinical evaluation of the therapeutic potential of antimicrobial 265 nm UVC for infectious keratitis.

METHODS

Four experiments explored UVC: 1) impact on bacterial and fungal lawns on agar, in individual or mixed culture, 2) bacterial inactivation dose in an in vitro deep corneal infection model, 3) dose validation in an ex vivo porcine keratitis model and 4) efficacy in a masked, randomised, controlled murine keratitis trial using bioluminescent Pseudomonas aeruginosa.

RESULTS

Minimum effective UVC exposures ranged between 2 s and 5 s for lawn bacteria and fungi in individual or mixed culture. Significant P. aeruginosa growth inhibition in the in vitro infection model was achieved with 15 s UVC, that resulted in a >3.5 log10 reduction of bacteria in a subsequent ex vivo keratitis model (p < 0.05). Bioluminescence fell below baseline levels in all treated animals, within 8 h of treatment (p < 0.05), in the in vivo study. Re-epithelialisation with corneal clarity occurred within 24 h in 75% of UVC-treated cases, with no relapse at 48 h. On plating, bacteria were recovered only from untreated controls.

CONCLUSIONS

UVC inhibited all tested bacteria and fungi, including mixed culture and strains linked to antibiotic resistance, in vitro, with exposures of ≤ 5 s. In vitro and ex vivo testing confirmed therapeutic potential of 15 s UVC. In vivo, 15 s UVC administered in two doses, 4 h apart, proved effective in treating murine bacterial keratitis.

Positive Microbiological Stains of Corneal Scrapings among Patients with Keratitis in a Tertiary Care Centre: A Descriptive Cross-sectional Study

Introduction

Keratitis, an ocular emergency, requires rapid and accurate treatment to prevent vision impairment. Wet mount direct microscopy examination of corneal scraping smear using gram and 10% potassium hydroxide stain helps in early diagnosis and treatment. The main objective of this study was to find out the prevalence of positive microbiological stains of corneal scrapings among patients with keratitis in a tertiary care centre.

Methods

A descriptive cross-sectional study was conducted in the Department of Ophthalmic Pathology and Laboratory Medicine from January, 2018 to December, 2019. Data collection was done after taking ethical approval from the Institutional Review Committee of the hospital (Reference number: BEH-IRC-35/A). All corneal smear samples received in this department were included in this study. Case records with incomplete data were excluded. Whole sampling was done. The data were analyzed using Statistical Package for the Social Sciences version 22.0. Frequency and percentage was calculated for binary data.

Results

Among 4631 corneal scrapings, microbiological stains were positive in 3538 (76.40%) patients.

Conclusions

The prevalence of positive microbiological stains of corneal scrapings in our study was higher in comparison to other studies done in similar settings. This technique could be used where culture facilities are unavailable or unaffordable.

Keywords

keratitis; microscopy; Nepal.

Bacterial and fungal causes of infectious keratitis among patients attending Research Institute of Ophthalmology

Background

Corneal ulcer is a potentially sight threatening ocular condition and the leading cause of monocular blindness in developing countries. Knowing the predisposing factors and etiologic microorganism can help prompt diagnosis and treatment to prevent devastating outcomes

The aim of this study was to detect the prevalence of bacteria and fungi in infectious keratitis. And to detect the antimicrobial susceptibility pattern against these causative bacterial and fungal pathogens using antibacterial and antifungal disces.

Results

Out of 50 cases (= 50 eyes), fungal growth was predominant 23/50 representing 46% with Aspergillus flavus being the most prevalent 14/23(61%). Bacterial growth was 7/50 (14%), 4/7 was gram-positive cocci (Staphylococcus aureus and Streptococcus pneumonie) and 3/7 was pseudomonas spp. While twenty out of 50 cases (40%) showed no growth.

Conclusion

Ocular trauma was the major cause of infectious keratitis, more in rural population. Fungal growth; mainly Aspergillus spp. was the most prevalent pathogen encountered in all cases. Voriconazole proved to be the first choice in the treatment of mould keratitis with 100% susceptibility. While alarmingly, fluconazole should no longer be used for the empirical therapy as it showed resistance to all the fungal isolates.

Ocular bacterial infections: Pathogenesis and diagnosis

The human eye is a rigid asymmetric structure with unique defence system. Despite considerable resident microbiota, eye is exposed to external environment where a range of microorganisms also inhabits. Opportunistically, some of these microorganisms could associate with eye pathogen that could contact incidentally, leading to destructive visual consequences. Among such microbiota, bacteria form the major proportion concerning ocular complications worldwide. The succession of genome based approach through 16S rRNA gene based identification tremendously augmented the knowledge on diversity of ocular surface bacteria. Such evidence suggests that while few bacteria contribute towards normal ocular functions, considerable number of bacteria play active role in pathophysiology of ocular diseases. Thus, understanding the complexity of ocular microflora not only throw light on their critical role towards normal function of the eye, but also enlighten on certain visual exigencies. Under these circumstances, development of a rapid, reliable and cost effective method is essential that eventually evolve as a routine diagnostic protocol. Such precise prognostic modalities facilitate ophthalmologists to formulate pioneering therapeutics towards challenging ocular diseases.

In Vitro Biofilm Formation and Antibiotic Susceptibility Patterns of Bacteria from Suspected External Eye Infected Patients Attending Ophthalmology Clinic, Southwest Ethiopia

Background

Ocular disease with its complications is a major public health problem which has significant impacts on the quality of life particularly in developing countries. An eye infection due to bacterial agents can lead to reduced vision and blindness. This study was aimed to assess the antimicrobial susceptibility pattern and biofilm-forming potential of bacteria isolated from suspected external eye infected patients in Jimma.

Method

A cross-sectional facility-based study was conducted on 319 suspect patients with external eye infections from March to June 2017 at Jimma University Medical Center (JUMC) Ophthalmology Department in Ethiopia. External ocular specimens were collected and standard operating procedures were followed to handle and culture throughout the study period. Antimicrobial susceptibility was determined by the disk diffusion method according to CLSI guidelines. Microtiter (96 wells) plate method was used to screen biofilm formation by ELISA reader at 570 nm.

Results

Out of 319 study participants with an external eye infection, the prevalence of bacterial pathogens was 46.1%. The predominant bacterial isolates were coagulase-negative staphylococcus (CoNS) (27.7%) followed by Staphylococcus aureus (19.7%). Among Gram-negative groups, Pseudomonas aeruginosa (6.8%) was the leading isolate. Increased antimicrobial resistance was observed for tetracycline (64%), erythromycin (66.7%), and penicillin (77.1%). Amoxicillin-clavulanic acid, ciprofloxacin, and gentamicin were the most effective drugs for external eye infections due to susceptibility ranging from 70 to 100% among both Gram-negative and Gram-positive groups. Methicillin-resistant S. aureus (MRSA) accounted for 13.8%. Multidrug resistance (MDR) accounted for 68.7%. The overall biofilm formation rate of bacterial ocular pathogens was 66.1%, where P. aeruginosa (40%), CoNS (34.1%), and S. aureus (31%) formed strong biofilm phenotype.

Conclusion

The prevalence rate of bacterial isolates was high. Almost all bacterial isolates were resistant to at least one or more drugs. MDR pathogens were observed increasingly among biofilm formers or vice versa.

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.

Stability of a 50 mg/mL Ceftazidime Eye-Drops Formulation

Background

Microbial keratitis are severe infectionsgenerally linked to risk factors. High-doses antibiotic eye-drops could be required to avoid severe complications. In such cases, hospital pharmacists are in charge of their production given the lack of such formulations on the market. The stability of these antibiotic eye-drops is generally limited to a couple of days and publications generally do not describe addition of microbial preservatives even though it is a European Pharmacopeia requirement. The aim of this study was to describe a new ceftazidime eye-drops formulation at 50 mg/mL with a antimicrobial additive, benzalkonium chloride at 0.04 mg/mL.

Methods

Physico-chemical studies of this new formulation were performed by a stability indicating HPLC-UV method validated according to ICH standards, osmolality measurements, pH monitoring and visual examinations. Antimicrobial preservative efficacy was evaluated according to the method from the European Pharmacopeia.

Results

After 75 days at −20 °C followed by 7 days at 4 °C, or after 7 days at 4 °C, the eye-drops were stable. A degradation trend was finally observed at day 14 at 4 °C.

Conclusions

A new ceftazidime eye-drops formulation is proposed with a stability of 7 days. Outpatients do not need to return to the hospital pharmacy for repeat dispensing, thus possibly improving treatment compliance.

Bacterial keratitis treated by strengthened antibiotic eye drops: An 18 months review of clinical cases and antibiotic susceptibilities

PURPOSE

To describe, in patients treated for infectious keratitis, the microorganisms identified and their antibiotic susceptibility over a period of 18 months.

METHOD

Retrospective, descriptive, non-comparative study. Medical and biological data were extracted from the patients' file treated with strengthened antibiotic eye drops at Angers University Hospital between January 2015 and June 2016. The main elements noted were the bacteria involved and their susceptibility to antibiotics. Patients' visual acuity at the start and end of treatment was compared.

RESULTS

Forty-eight patients were included. Almost one bacterium was identified in 31 patients, totalling 43 pathogens of 24 different species. The most frequently found microorganisms were Gram-positive cocci (55.8%), including Staphylococcus Aureus (14.0%) and Epidermidis (14.0%). All Gram-negative bacilli amounted to 30.2% of the identified bacteria, including 9.3% of Pseudomonas aeruginosa. None of the Gram-positive cocci were resistant to vancomycin and all Gram-negative bacilli were susceptible to ceftazidime and amikacin. Following treatment with at least one of the three antibiotic eye drops produced by our pharmacy (amikacin at 50mg/mL, ceftazidime at 50mg/mL and vancomycin at 25mg/mL), patients' visual acuity was significantly improved (P=0.043).

CONCLUSION

The study helped identify the bacterial ecology of patients admitted for infectious keratitis. Among the bacteria identified, none were found to be resistant to any of the three strengthened antibiotic eye drops produced by the hospital pharmacy. These eye drops allowed for a rapid and effective treatment of patients and the improvement of their visual acuity before even identifying the bacteria.