Infectious Keratitis in Western Nepal: An Experience from a Tertiary Care Hospital

Corneal blindness is a major public health problem worldwide and infectious keratitis remains a leading cause. The aim was to analyze the microbial etiology of corneal ulcers and to determine the antibiotic susceptibility pattern of bacterial isolates. Among 84 clinically diagnosed cases, 33 (39.3%) were farmers by occupation. All cases were reviewed for predisposing conditions and clinical severity. Ulcers were categorized as mild in 49 cases moderate in 12 and severe in 23 cases. Predisposing conditions were detected in 65.5% (55/84) of patients. Forty-two cases showed culture positivity. Among these 42; 25 (29.7%) yielded fungi, 13(30.1%) yielded bacteria and the rest 4 (4.7%) showed mixed growth, accounting for a total of 29 cases showing fungal growth, and 17 demonstrating bacterial growth. Aspergillus spp. (10/29; 34.5%) were the commonest fungi and Staphylococcus aureus, (8/17; 47%) was the most common among bacteria. Majority i.e 66.7% (26 of 39) of those having trauma as the predisposing factor developed moderate to severe degree of corneal ulceration as compared to only 20% (9 of 45) of those without any history of trauma and this difference was found to be statistically significant (p<0.001). Interestingly, 20(68.9%) of 29 cases that yielded fungal growth on culture had previous history of ocular trauma in contrast to only 19 (34.5%) of 55 who had non-fungal keratitis (p=0.003). It was also observed that significantly higher number of fungal keratits cases exhibited pronounced degree of clinical severity, as compared to cases without any fungal aetiology (p<0.001) Topical administration of fourth generation fluoroquinolone eye drops remained the most effective drug of choice as far as the clinical outcome of bacterial keratitis was concerned. Trauma with vegetative matter predisposed to most cases of fungal keratitis. Severe form of ulceration was noticed in patients with fungal infection.

Thus, a precise knowledge about the causative agents and their antibiotic susceptibility patterns is important in order to make a decision on the proper management strategies.
Isolating the pathogen, initiating appropriate therapy based on the organism's identification and sensitivity pattern, represent the key to success in patient management.
Moreover, an understanding of the pathogenesis of the condition is important in its rapid recognition so that one may adopt modalities and prevent complications like corneal scarring and subsequent visual loss. To the best of our knowledge, the microbial etiology of corneal ulcer and the magnitude of the problem in Nepal is yet underestimated Thus, the aim of this study was is to analyze the bacterial and fungal agents causing corneal ulcer among patients presenting to a tertiary care hospital in western Nepal. Secondly we also attempted to determine the antibiotic susceptibility pattern of bacterial isolates in order to know the existing pattern of antibiotic resistance among the isolates.

Methods
A total of 84 clinically diagnosed keratitis patients presenting to a tertiary eye care hospital 6 (Himalayan Eye Hospital, Pokhara) in western Nepal over a period of 12 month (June 2017 to May 2018) were investigated. All the cases had reported with presenting symptoms of redness, pain, watery discharge, diminution of vision, and photophobia. Patients' written consents were taken and a standardized detailed history, including their demographic profile, time of onset of symptoms, predisposing factors if any including corneal injuries (agricultural, non-agricultural, and foreign body injuries), history of contact lens wear, prior antibiotic therapy, steroid use and previous surgery were obtained. The plates were examined after 24 and 48 hrs. All the bacterial isolates were identified with the help of standard protocol [14]. [14: . N Nayak: Fungal infections of the eye -laboratory      [22]. Our results are in complete agreement with the data reported elsewhere, [14] which showed that trauma with vegetative matter, could predispose to ulcerative keratitis in 23-55% of the cases.
Thus, it is very much relevant to mention here that fungi being ubiquitous in nature, their spores upon getting deposited over the damaged cornea following trauma, may easily germinate and propagate to hyphal forms which are potentially invasive, and are able to transverve through the layers of the cornea producing different grades of severity of the lesions [14,19].
In the present geographical location, seasonal variation of out-flair of corneal ulcer was noticed during May to August, the period when agricultural activity was on its peak as it was the crop planting period. We again found an upsurge of cases in November and December, i.e the crop harvesting period. Seasonal trend similar to that observed in the present series was shown by Basak et al.,[[endnoteRef:29]] from eastern part of India, which could be accounted due to the frequent exposure to vegetative matter in the cornfields with easy facilitation for corneal injury. None of the study subjects in our series had the history of contact lens wear. Use of contact lenses was documented as one of the main predisposing conditions for microbial keratitis among young adults in the developed nations [30]. Cheung and Stomovac [28] reported contact lens associated keratitis in 12% of their cases, and Pseudomonas aeruginosa was the predominant isolate among the contact lens wearers. However, a number of studies conducted earlier in different parts of the world in tertiary care eye centers put forth the view that incidence of contact lens induced keratitis was very meagre accounting for only was sensitive to all except cefazolin. Streptococcus pneumoniae (n=1), however was also sensitive to all the antibiotics.
In the view of frequent reports of changing pattern of susceptibility among bacteria, testing of clinical isolates for their susceptibility to antimicrobial drugs is necessary for selection of appropriate antibiotics or for changing an already administered antibiotic. In this study, all the bacterial isolates (Gram positive and Gram negative) were susceptible to fourth generation quinolone moxifloxacin, which is often chosen as the antibiotic of choice by many clinicians, including us, for treating bacterial keratitis. All the isolated S. pneumoniae and viridians Streptococci were susceptible to the entire panel of antibiotics tested.
Dhakhwa et al [22] from Nepal stated that the most effective antibiotic against gram positive bacteria was cephazolin (84.92% of the organisms being sensitive) and that against gram negative organisms was the commonly used fluoroquinolone, ciprofloxacin (79.31% of the organisms showing sensitivity). However, a review of available treatment modalities in corneal ulcer showed that monotherapy with fluoroquinolones was a risk for the perforation in corneal ulcer, and there was concern over the emergence of resistance to fluoroqinolones in patients treated with these agents ( gatifloxacin or moxifloxacin or ciprofloxacin) This study showed that trauma with vegetative matter was the most common predisposing factor especially for fungal keratitis. Fungal etiology accounted for more severe form of ulcerative lesions. In the light of constantly changing trends in the etiology and in the antibiotic susceptibility patterns of the etiologic agents in infectious keratitis it is advocated to have routine surveillance of culture and sensitivity testing of the keratitis causing pathogens in order to provide appropriate antimicrobial therapy.

Declarations
Ethical approval and consent to participate: Ethical approval was obtained from Himalayan Eye Hospital, Pokhara, Nepal before conducting the research.
Informed written consent was obtained from each patient in this study before collection of samples.

Consent for publication: Not Applicable
Availability of data and materials: All data obtained during this study are available within the article.
Funding: No specific funding for this study was received.