[Severe bacterial keratitis referred to ophthalmology emergency departments: a retrospective study of 268 cases]

The effect of climatic and seasonal factors on the microbial keratitis profile

PURPOSE

To compare retrospective data on microbial keratitis (MK) from two different climatic regions in Turkey over 11 years.

STUDY DESIGN

Retrospective cohort.

METHODS

This retrospective cohort study included patients diagnosed with presumed MK at two referral centers. Center A was located in the subtropical region of Turkey, whereas Center B was located in a continental temperate climate zone. Clinical and laboratory data were also recorded. The results were evaluated for seasonal variations.

RESULTS

This study included data from 665 patients with presumed MK (351 and 314 patients from centers A and B, respectively). The most common predisposing factors were ocular trauma in Center A, prior ocular surgery, and systemic disease in Center B. Severe keratitis was related to prior ocular surgery, presence of systemic disease, and fungal infection at presentation. The culture positivity rate was higher in spring and lower in summer at both centers. Gram-positive bacteria were the most commonly isolated bacteria in both centers in all seasons. The fungal and mixed keratitis ratios were higher in Center A than in Center B. In Center A, filamentous fungi were common pathogens that were found year-round, and peaks were observed in July and October.

CONCLUSION

The results of this study show that climatic and seasonal factors may affect the microbial profile of keratitis. Fungal keratitis appears to be a climatic disease. Understanding the regional profile of MK can aid clinicians in their disease management.

Chitosan-poly(lactide-co-glycolide)/poloxamer mixed micelles as a mucoadhesive thermo-responsive moxifloxacin eye drop to improve treatment efficacy in bacterial keratitis

A mucoadhesive self-assembling polymeric system was developed to carry moxifloxacin (M) for treating bacterial keratitis (BK). Chitosan-PLGA (C) conjugate was synthesized, and poloxamers (F68/127) were mixed in different proportions (1: 5/10) to prepare moxifloxacin (M)-encapsulated mixed micelles (M@CF68/127(5/10)Ms), including M@CF68(5)Ms, M@CF68(10)Ms, M@CF127(5)Ms, and M@CF127(10)Ms. The corneal penetration and mucoadhesiveness were determined biochemically, in vitro using human corneal epithelial (HCE) cells in monolayers and spheroids, ex vivo using goat cornea, and in vivo via live-animal imaging. The antibacterial efficacy was studied on planktonic biofilms of P. aeruginosa and S. aureus (in vitro) and Bk-induced mice (in vivo). Both M@CF68(10)Ms and M@CF127(10)Ms demonstrated high cellular uptake, corneal retention, muco-adhesiveness, and antibacterial effect, with M@CF127(10)Ms exhibiting superior therapeutic effects in P. aeruginosa and S. aureus-infected BK mouse model by reducing the corneal bacterial load and preventing corneal damage. Therefore, the newly developed nanomedicine is promising for clinical translation in treating BK.

Paradox of complex diversity: Challenges in the diagnosis and management of bacterial keratitis

Bacterial keratitis continues to be one of the leading causes of corneal blindness in the developed as well as the developing world, despite swift progress since the dawn of the "anti-biotic era". Although, we are expeditiously developing our understanding about the different causative organisms and associated pathology leading to keratitis, extensive gaps in knowledge continue to dampen the efforts for early and accurate diagnosis, and management in these patients, resulting in poor clinical outcomes. The ability of the causative bacteria to subdue the therapeutic challenge stems from their large genome encoding complex regulatory networks, variety of unique virulence factors, and rapid secretion of tissue damaging proteases and toxins. In this review article, we have provided an overview of the established classical diagnostic techniques and therapeutics for keratitis caused by various bacteria. We have extensively reported our recent in-roads through novel tools for accurate diagnosis of mono- and poly-bacterial corneal infections. Furthermore, we outlined the recent progress by our group and others in understanding the sub-cellular genomic changes that lead to antibiotic resistance in these organisms. Finally, we discussed in detail, the novel therapies and drug delivery systems in development for the efficacious management of bacterial keratitis.

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.

[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.

Modulation of immune signaling, bacterial clearance, and corneal integrity by toll-like receptors during streptococcus pneumoniae keratitis

PURPOSE

Bacterial keratitis, without effective antimicrobial treatment, leads to poor patient prognosis. Even after bacterial clearance, the host inflammatory response can contribute to corneal damage. Though Streptococcus pneumoniae (pneumococcus) is a common cause of bacterial keratitis, the role of host innate immunity during pneumococcal keratitis is not well characterized. This study investigated the role of Toll-like receptors (TLRs) during pneumococcal keratitis.

MATERIALS AND METHODS

C57BL/6, as well as TLR2(-/-) and TLR4(-/-) mice, were infected with S. pneumoniae, and infected corneas were examined for 21 days. Quantitative real-time reverse-transcriptase polymerase chain reaction was performed using primers for genes involved in the inflammatory response and TLR signaling. Bacterial survival and leukocyte invasion were examined over a 72-h period.

RESULTS

The corneal expression of TLR2, TLR4, and other inflammatory genes was increased at 72 h post-infection (p.i.) compared to uninfected C57BL/6 scratch controls. TLR2(-/-) mice showed a significant increase in bacterial survival at 24 h p.i. likely due to decreased neutrophil infiltration; however, after Day 5 p.i. observed clinical scores of TLR2(-/-) and C57BL/6 mice were not significantly different. In contrast, permanent corneal damage was observed for TLR4(-/-) mice over 21 days. Initially, both TLR(-/-) mouse strains exhibited lower expression levels in many immune genes, but returned to similar or elevated levels compared to C57BL/6 mice by 72 h p.i.

CONCLUSIONS

TLR2 and TLR4 are involved in the response to pneumococcal keratitis and TLR2 may aid in bacterial clearance by recruitment of neutrophils to the cornea, whereas TLR4 may be necessary to modulate the immune response to limit cellular damage.