Corneal blindness is a major public health problem worldwide and infectious keratitis is one of the predominant causes. The main objective of the study was to find out the microbial etiology of corneal ulcers among our patients and to determine the antibiotic susceptibility pattern of the bacterial isolates. Besides, we also analyzed the demographic profile of the patients and the epidemiological factors prevailing in our locality.
Demographic data of the patients revealed that majority of them belonged to the age group of 41-60 years (38/84, i.e 45.2%). Thus, many patients belonged to the working age group and thus might have had more chances of exposure to ocular trauma, which was the most common predisposing factor as shown in the present study. This observation of ours is similar to that reported by Chowdhary et. al [[endnoteRef:19]] who showed as high as 37 % of cases of keratitis to have occurred in the age group i.e 31- 40 years. Considering such high prevalence in the younger subjects, it could, be deduced that younger the age group affected, greater could be the socioeconomic consequences, as a result of loss of active man power. [19: . Chowdhary A, Singh K. Spectrum of fungal keratitis in North India. Cornea. 2005; 24(1): 8 -15]
Of the 84 subjects studied, 50 (59.5%) were females and 34 (40.5%) were males. Similar findings on higher infection rates in females as compared to males were noted by Sharmila et al. [[endnoteRef:20]] in a study from Nepal. Others, however, reported a higher incidence of infectious keratitis in males [[endnoteRef:21],[endnoteRef:22]]. The higher number of cases among females, in our study could be because of more exposure of the female population to agricultural and household activities in the context of Nepal. Females in this part of the world seemed to be affected more often than males because there is a significant contribution of the female population to the agricultural force as compared to the males who quite often remain away from outdoor activities in search of employment [[endnoteRef:23]]. [20: . Suwal S, Bhandari D, Thapa P, Shrestha MK and Amatya J. Microbiological profile of corneal ulcer cases diagnosed in a tertiary care ophthalmological institute in Nepal.BMC Ophthalmology. (2016) 16:209 DOI 10.1186/s12886-016-0388.] [21: . Lavaju P, Arya SK, Khanal B, Amatya R, Patel S. Demograhic pattern, clinical features and treatment outcome of patients with infective keratitis in the eastern region of Nepal. Nepal J Ophthalmol. 2009;1(2):101–6. ] [22: . Dhakhwa K, Sharma MK, Bajimaya S, Dwivedi AK, Rai S. Causative organisms in microbial keratitis, their sensitivity pattern and treatment outcome in western Nepal. Nepal J Ophthalmol. 2012; 4(1):119–27. Available from:http://www. epjoph.org.np/pdf/NEPjOPH_201201136.pdf.] [23: 23. Rai PG, Chaudhary M, Sharma AK, Gautam V, Rai SG et al Direct microscopy in suppurative keratitis: a report from tertiary level hospital in Nepal. Nepal J Ophthalmol. 2016; 8(16): 128-138.]
In this present study, thirty-three (39.3%) of the subjects were farmers by occupation. In a country like Nepal, majority of the population is engaged in agricultural work and various types of manual labors. Thus, they invariably become prone to injuries for being exposed to dust & wind, dryness and heat due to which they often have ocular surface abnormalities, which in presence of poor ocular hygiene may promote development of ulcerative keratitis. Similar observations were noted by Sharma et al.[[endnoteRef:24]] in an investigation on the clinical profile and contributing factors in microbial keratitis from Nepal. Obviously, trauma was the most common risk factor accounting for 46% (39/84) of our cases. Ocular trauma had always been identified as a common predisposing condition for the development of ulcerative keratitis [[endnoteRef:25],[endnoteRef:26]]. [24: . Sharma B, Gupta R, V Som SS Kubrey. Reena Anand, K Kumar, “Clinical profile of microbial keratitis causes and contributing factors”. Journal of Evolution of Medical and Dental Sciences 2013; Vol2, Issue 51, December 23; Page: 9939-9947.] [25: . Kampitak K, Suntisetsin H, Sirikul T. Brief communication (Original). Clinical and microbiological characteristics of corneal ulcers in a Thai referral center. Asian Biomedicine.2014; 8(2):275-282.] [26: . Nayak N, Satpathy Gm Vajpayee RB, Sathi A, Ray M, Sinha R. Clinical significance of steme production by Staphylococcus epidermidis in bacterial keratitis. Ann Opthalmol 2002; 34 (4):204-10.]
As reported previously, trauma as a predisposing factor could influence the outcome of infectious keratitis in any clinical setting. In the present study, 66.7% of the patients with previous history of trauma had moderate to severe form of keratitis (table 3).
Thus it goes with the earlier concept that, disruption of corneal epithelial barrier in any form, including trauma might accentuate the pathogenicity of microorganisms facilitating their invasion into the layers of cornea producing clinical severity [[endnoteRef:27],[endnoteRef:28]]. [27: . Gordon LR, Brinsor JH. Outpatient treatment of microbial corneal ulcers. Arch Opthalmol 1986; 104:84-6.] [28: . Cheurg J, Slomorie AR. Microbial etiology and predisposing factors among patients hospitalized for corneal ulceration. Can J Opthalmol 1995; 30(5): 251-5.]
It was even interesting to observe that higher number of patients (20 of 29, i.e 68.95 %) in our series with fungal etiology had prior history of corneal injury (table 4). A previous study from Nepal documented that 37.68% of corneal ulcer cases with trauma were of fungal origin, whereas 23.19% had yielded bacterial growth [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. [29: . Basak SK, Basak S, Mohanta A, Bhowmick A. Epidemiological and Microbiological Diagnosis of Suppurative Keratitis in Gangetic West Bengal, Eastern India. Indian J Opthalmol. 2005; 53(1): 17-22.]
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 0.11-2% of the cases [[endnoteRef:30],[endnoteRef:31]]. Nevertheless, it is important to note that Pseudomonas aeruginosa was reported to be the common bacterial agent in contact lens associated keratitis due to its biofilm forming ability on extended wear contact lenses [[endnoteRef:32]]. [30: . Sharma S, Gopalakrishnan S, Aasuri MK, Garg P, Rao GN. Trends in contact lens-associated microbial keratitis in Southern India. Ophthalmology 2003 Jan; 110(1):138-43.] [31: . Eltis M. Contact lens related microbial keratitis. Case report and review. J optometry 2011;4 (4);122-7.] [32: . Danielle M. Robertson, Quinn M. Parks, Robert L. Young, Jennifer kret, Katie R Poch, Kenneth C. Malcolm et al. Disruption of Contact Lens–Associated Pseudomonas aeruginosa Biofilms Formed in the Presence of Neutrophils. Investigative Ophthalmology & Visual Science April 2011, Vol.52, 2844-2850. doi:10.1167/iovs.10-6469.]
As shown in table 3, out of the 84 samples examined, culture positivity was seen in 42 (50%). Among these 42; 25 (29.7%) yielded fungal growth, 13 (30.1%) yielded bacteria and the rest 4 (4.7%) showed mixed growth. Overall there were 17(20.2%) bacterial isolates and 29 (34.5%) fungal isolates. Aspergillus spp. (10/29) were the commonest among all fungi isolated followed by Fusarium spp., 20 % (6/29). The most commonly isolated fungal pathogens in the current series were Aspergillus spp., (33.3%) followed by Fusarium spp., (12.67%). Aspergillus spp. had been incriminated as the commonest fungal agents of infectious keratitis in the past as per the documented reports from parts of northern India and Nepal [11, 14]. On the contrary, Fusarium spp. were more commonly associated according to the reports from southern parts of India and other tropical countries like Ghana [ 8,[endnoteRef:33],34]. [33: . Tewari A, Sood N, Vegad MM, Mehta DC. Epidemiological and microbiological profile of infective keratitis in Ahmedabad. Indian J Opthalmol. 2012; 60(4): 267-72.]
Ganguly et al. from Nepal found Fusarium, as the commonest fungus isolated and it was the sole fungal pathogen isolated in 32 % of their cases, followed by unidentified dematiaceous species in 22 % and Curvularia species in 18 % of cases [[endnoteRef:34]]. In the saprobic environment, Fusarium species are well known plant pathogens, especially causing damage to cereal crops. These are also found in decaying plant debris and are abundantly present in soil. Therefore, the practice of growing plenty of cereal crops during the summer and early part of rainy season in south India and Ghana probably provides conducive ecological conditions, including hot and humid environment, optimally favoring these species to flourish in these geographical areas. [34: . Ganguly S, Salma KC, Kansakar I, Sharma M, Bastola P, Pradhan R. A Pattern of fungal isolates in cases of corneal ulcer in the western periphery of Nepal. Nepal J Ophthalmol.2011; 3 (2): 118-122.]
As far as bacteria pathogens were concerned, Staphylococcus aureus, (47%; 8/17) was the most common agent followed by Pseudomonas, (11.7%; 2/17). All the strains of Staphylococci were sensitive to amikacin and moxifloxacin. Amongst the Staphylococcus aureus 5/8 were methicillin sensitive and 3/8 were methicillin-resistant. Out of 3 methicillin resistant Staphylococcus aureus (MRSA), 2 isolates were resistant to ciprofloxacin and 1 was resistant to levofloxacin. All the isolates of E. coli (n=2) Klebsiella spp. (n=2) and Pseudomonas (n=2) were sensitive to the whole panel of antibiotics tested. Acinetobacter (n=1) was sensitive to all except chloramphenicol. The single isolate of Enterobacter (n=1) 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) monotherapy [[endnoteRef:35]]. [35: . Tittiyal JS, Negi S, Anand A, Tandon R, Sharma N, Vajpayee RB. Risk factors for perforation in microbial corneal ulcers in north India. Br J Opthalmol 2006; 90(6): 686-9.]
Notwithstanding the above, all our patients in our series, responded well to topical moxifloxacin, and the ulcers healed without complications. Ranjini and collegues [[endnoteRef:36]] from India also reported that all their 52 bacterial isolates (both gram positive and gram negative) from 117 culture positive keratitis cases were sensitive to gatifloxacin. [36: . Ranjini CY, Vandana VW. Microbial Profile of Corneal Ulcers in a Tertiary Care Hospital in South India. J Opthalmic Vis Res. 2016; 11(4): 363-7.]