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 Table of Contents  
Year : 2022  |  Volume : 34  |  Issue : 1  |  Page : 32-36

Demographical and etiological diagnosis of infective corneal ulcer in a tertiary care center in West Bengal: A cross-sectional study

1 Department of Ophthalmology, Calcutta National Medical College, Kolkata, West Bengal, India
2 Department of Ophthalmology, Regional Institute of Ophthalmology, Medical College Campus, Kolkata, West Bengal, India

Date of Submission03-Jan-2021
Date of Decision23-Jan-2021
Date of Acceptance24-Jan-2021
Date of Web Publication21-Apr-2022

Correspondence Address:
Dr. Anindya Gupta
Regional Institute of Ophthalmology, Medical College Campus, 88 College Street, Kolkata - 700 073, West Bengal
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/kjo.kjo_1_21

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Purpose: The purpose was to study the demographical factors and microbial etiology associated with infective keratitis in a tertiary care center in West Bengal. Materials and Methods: In this cross-sectional study, 142 patients with suspected microbial keratitis were enrolled from June 2019 to May 2020. After taking the history and diagnosing the infective ulcer clinically, the corneal scrapings and cultures were evaluated. The smears were fixed with Gram stain and 10% potassium hydroxide wet preparation. The scrapped material was inoculated in blood agar and Sabouraud dextrose agar for culture. Results: Ocular trauma was the most common predisposing factor in 94 (70.6%) corneal ulcers (P < 0.0001). The most common etiologic agent causing corneal injury was wooden object (38.3%). Microbial etiology was established in 76 (53.52%) corneal scrapings. Out of the total culture-positive cases, 45 patients (31.7%) had pure fungal infections, 25 patients (17.6%) had pure bacterial infections, and 6 patients (4.2%) reported mixed infections. Among the fungal pathogens, Aspergillus species was the most common fungal isolate (29 cases, 56.8%), followed by Fusarium species (17 cases, 33.3%) and Candida species (5 cases, 9.8%). The most common bacterial isolate was Staphylococcus aureus (16 cases, 51.6%), followed by Pneumococcus species (7 cases, 22.5%). Conclusion: Trauma with wooden material was the most common predisposing factor for infective keratitis. Fungal ulcers predominated in the study findings. Aspergillus species and S. aureus were the most common fungal and bacterial isolates, respectively. Regional variations exist in the microbial etiology of infective keratitis.

Keywords: Infective keratitis, microbial etiology, ocular trauma

How to cite this article:
Joshi G, Sengupta P, Gupta A. Demographical and etiological diagnosis of infective corneal ulcer in a tertiary care center in West Bengal: A cross-sectional study. Kerala J Ophthalmol 2022;34:32-6

How to cite this URL:
Joshi G, Sengupta P, Gupta A. Demographical and etiological diagnosis of infective corneal ulcer in a tertiary care center in West Bengal: A cross-sectional study. Kerala J Ophthalmol [serial online] 2022 [cited 2022 Dec 8];34:32-6. Available from: http://www.kjophthal.com/text.asp?2022/34/1/32/343656

  Introduction Top

Corneal ulceration is emerging as a silent epidemic, with India accounting for a large portion of the global burden of infectious keratitis. By definition, a corneal ulcer is a break in the epithelium with underlying stromal necrosis.

Corneal opacities, which are largely caused by infectious keratitis, are the fourth leading cause of blindness globally and responsible for 10% of the avoidable visual impairment in the world's least developed countries.[1],[2] In India, it is estimated that approximately 6.8 million people have vision of <6/60 in at least one eye due to corneal diseases; of these, about a million have bilateral involvement.[3] Therefore, trends in infectious keratitis observed in India are important for global public health planning.[4]

Microbial keratitis, if not adequately treated, can have severe consequences. The clinical presentation of corneal ulceration is worsened due to the indiscriminate use of steroids by local doctors and quacks. With definitive identification and treatment, the significant morbidity associated with severe microbial keratitis may be avoided.

The prevalence of visual disability due to corneal opacity varies from one geographical location to another.[5] It is therefore important to recognize these patterns for early diagnosis, institution of therapy, optimal management, and also for the prevention of the disease.

There are several studies establishing the microbial etiology of infective keratitis from various parts of India. However, adequate data are lacking in the eastern part of the country in particular. This study is being done to find the microbial etiology of infective keratitis in a tertiary care center in West Bengal and also to identify the risk factors predisposing to corneal ulceration.

  Materials and Methods Top

This study was a teaching hospital-based cross-sectional type of observational study. We took history, performed ophthalmologic examination, and took samples in 142 patients, aged between 10 and 80 years, who presented with a corneal infiltrate that was compatible with the diagnosis of a bacterial or fungal corneal ulcer, at the outpatient clinic of the Department of Ophthalmology, Calcutta National Medical College and Hospital (CNMCH), from June 2019 to May 2020.

The Institutional Ethics Board of CNMCH and West Bengal University of Health Sciences Ethics Committee approved the clinical study. The patients themselves provided written informed consent after being given a detailed explanation of the study. We confirmed that the patients had seen the manuscript and patient data and agreed to its publication in a journal.

Exclusion criteria were as follows: (i) typical or suspected viral ulcers; (ii) Mooren's ulcer, marginal keratitis, interstitial keratitis, and atheromatous ulcers; (iii) any ulcer associated with systemic/autoimmune diseases; (iv) neurotrophic corneal ulcers; and (v) unwilling patients.

Ocular examination and specimen collection

The visual acuity was measured using a Snellen's chart. All the patients were examined under a slit-lamp biomicroscope by an ophthalmologist. The size of the ulcer, size of the stromal infiltrate, and depth were measured and recorded (in millimeters). The ulcer margin, floor, thinning, presence of vascularization, satellite lesions, pigmentation on the ulcer surface, surrounding corneal tissue, and any impacted foreign body were noted. The presence of hypopyon was noted and its height was recorded (in millimeters). The use of topical medications including topical corticosteroids and contact lens wear was noted. Associated ocular conditions such as dry eye, lagophthalmos, chronic dacryocystitis, and corneal anesthesia were noted.

Corneal scraping was performed under strict aseptic conditions by an ophthalmologist using a sterile Bard-Parker blade (No. 15). Fresh proparacaine (0.5%) eye drops were used for topical anesthesia, and the procedure was performed under the magnification of a slit lamp. The material obtained from the leading edge and the base of each ulcer was inoculated into the media and was smeared onto two slides – one for Gram stain and the other for 10% potassium hydroxide wet mount preparation for direct microscopic examination.

Laboratory procedures

All laboratory diagnosis was performed using standard protocols. For bacterial cultures, the material inoculated in blood agar, chocolate agar, and MacConkey agar was incubated at 37°C for 24 h. Examination was done at the end of 24 h and again after 48 h of incubation. If no growth was observed, the plates were discarded. The Sabouraud dextrose agar slope was incubated at room temperature for up to 2 weeks. The first examination was done after 48 h of inoculation, and then, it was reincubated. Further examination was done biweekly for up to 2 weeks to identify the growth of fungal colonies. At the end of the 2nd week, if there was no growth, the slope was discarded as negative.

Microbial cultures were considered to be significant if growth of the same organism could be demonstrated on two or more solid phase cultures. Similiarly, cultures were also significant if there was semiconfluent growth at the site of inoculation or growth on one solid medium consistent with microscopy; or semiconfluent growth at the site of inoculation on one solid medium; or growth of the same organism on repeated scraping. If, by microscopy, hyphae were observed in corneal tissue, but failed to grow in culture, the causative organism was reported as fungal.[6]

In the present study, a specimen was considered microbiologically positive only when the culture results were positive.

Statistical analysis

We made the following analysis and evaluation in patients who presented to us with a corneal infiltrate that was compatible with the diagnosis of a bacterial or fungal corneal ulcer: demographic characteristics, distribution of cases according to occupation, predisposing factors, various agents causing trauma, microbiological diagnosis, first presentation, and medication applied before inclusion in the study.

The categorical variables were expressed as the number of patients and percentage of patients and were compared across the groups using Fisher's exact test. The statistical software SPSS version 20 has been used for the analysis. An alpha level of 5% has been taken, i.e., if any P < 0.05, it has been considered as significant.

  Results Top

Distribution of study population according to age

The age of the patients included in the study ranged from 12 years to 79 years. Majority of the patients (58) were in the age group of 41–60 years (40.8%), P < 0.001, with the mean age being 45 ± 16.09 years [Table 1].
Table 1: Distribution of study population based on age groups (n=142)

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Distribution of study population according to gender and residence

In the study participants, there was male predominance (P < 0.05) and majority of the patients resided in urban areas (64.08%) [Table 2].
Table 2: Distribution of study population based on residence (n=142)

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Distribution of cases according to occupation

Majority of the patients in the study group were cultivators and gardeners (28.2%), followed by laborers and industrial workers (24.6%) and homemakers (19.0%) [Table 3].
Table 3: Distribution of study population based on occupation (n=142)

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Distribution of corneal ulcer cases according to predisposing factors

Out of the total 133 patients who had a history of predisposing factors, ocular trauma was the most common predisposing factor (P < 0.001) in 94 patients (70.6%). Preexisting ocular disease which included chronic dacryocystitis, dry eye, trichiasis, entropion, and lagophthalmos was seen in 10 patients (7.5%) [Table 4].
Table 4: Distribution of corneal ulcer cases according to different predisposing factors (n=142)

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Distribution of cases according to various agents causing trauma

The most common agent causing trauma as identified in the study was wooden object (38.3%). This was followed by vegetative matter (22.3%) [Table 5].
Table 5: Frequency distribution of agents causing trauma (n=94)

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Distribution of corneal ulcer cases according to microbiological diagnosis

Microbial etiology was found in 76 out of the 142 cases of corneal ulcers, with 45 cases (31.7%) positive for pure fungal pathogens and 25 cases (17.6%) positive for pure bacterial isolates. Mixed infections (both bacteria and fungi) were found in 4.2% of the cases [Table 6].
Table 6: Distribution of study cases based on type of infection (n=142)

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Distribution of fungal isolates from corneal ulcer cases

Filamentous fungi predominated in our study while few yeasts (Candida species) were also isolated. Aspergillus species was the predominant fungal pathogen (58.6%), followed by Fusarium species (33.3%) [Table 7].
Table 7: The bacterial isolates in patients with bacterial and missed infections (n=31)

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Distribution of bacterial isolates from corneal ulcer cases

A majority of the bacterial isolates were positive for Gram-positive cocci while only one for Gram-negative bacilli (GBC). Staphylococcus aureus was the most common bacterial pathogen found in 16 cases (51.6%), followed by Pneumococcus species seen in 7 cases (22.5%) [Table 7].

  Discussion Top

The external location of the cornea predisposes it to a variety of sight-threatening insults. A wide spectrum of microbial organisms can produce corneal infection. The severity of corneal infection depends on the underlying condition of the cornea and pathogenicity of the infecting organism,[7] and consequently, therapeutic strategies may be variable.[8]

In the present study, corneal ulceration was seen in all the age groups with a preponderance among physically active adults [Table 1]. Male patients outnumbered females in the study (58.45%) (P < 0.05), and majority of the patients were from urban areas [Table 2]. This pattern was consistent with most of the earlier observations, such as that reported by Gopinathan et al.,[9] and could be attributed to an increased outdoor activity of men, especially in the working age group. In this study, we found that majority of the patients were cultivators and gardeners (28%), followed by laborers and industrial workers (24.6%) [Table 3]. This may be explained by the increased risk of injuries while working in the fields or at the construction site or at the factories. This pattern of occupational profile is consistent with that seen in a South Indian study by Bharathi et al.[10] However, this was in contrast to a study done in Ghana where only 16.1% of the patients were agricultural workers.[11] Trauma was the most common predisposing factor (70.6%) [Table 4] similar to the findings of a study in South India.[5] The most common etiologic agent causing corneal injury was wooden object (38.3%), followed by vegetative matter (22.3%) [Table 5]. These figures compare favorably with a study in Ahmedabad,[12] where it was reported that trauma due to wooden objects (34%) was the leading cause of corneal ulceration.

In our study, we observed that about 35 (24.6%) patients presented in their 1st week of illness. This is in contrast to the findings in the study of Srinivasan et al.,[5] where most of the patients, i.e., around 60%, were examined within 7 days after the onset of their illness. Medical help was sought by 65.49% of the patients before their initial examination at our outpatient department. It is of interest to note that 11 patients (7.74%) went to village healers. There is a risk of a possible bacterial or fungal contamination of traditional medicine which can lead to deterioration and further progression of corneal ulceration.

We observed that about 97 patients (68.3%) were applying some form of topical medication before their inclusion in the study. In the study, 58 out of 142 cases were applying topical antibiotic drops, 23 patients were on antifungals and antibiotics, and 16 cases were applying corticosteroids. The application of medication before inclusion in the study was statistically significant as a large proportion of ulcer scrapings were sterile (66 cases, 46.48%) (P < 0.001).

Microorganisms were isolated from 76 (53.52%) specimens sent for culture [Table 6]. This figure is consistent with the findings of a study in Ghana[11] where 57.3% of all the cultures were positive, but it does not approach the 80% culture positivity rate reported from Nepal by Upadhyay et al.[13] The lower rate of isolation can be attributed to the widespread availability of topical medications in West Bengal and their use in the majority of the patients (68.3%) before evaluation. More than half (59.21%) of all corneal ulcers with positive cultures were fungal in origin. If the six mixed infections (7.89%) are also considered to be primarily fungal for treatment purpose and are added to the pure fungal cases, 67.1% of all the culture-positive ulcers grew fungal pathogens. This figure approaches the fungal isolation rate in Ghana where Hagan et al.[11] cultured fungi from 56% culture-positive cases. Aspergillus species (56.8%) was the predominant fungal agent [Table 7] in line with studies from eastern[14] and western India[12] and in Nepal by Upadhyay et al.,[13] where Aspergillus species accounted for 47% of all the fungal pathogens. This was followed by Fusarium species (33.8%) and Candida species (9.8%). Studies from South India[5],[10] and South Florida[15] show Fusarium species as the predominantly isolated pathogen among fungal positive corneal ulcer cases. This pattern of distribution could possibly be explained by differences in the climate and the natural environment.

Mixed infections both by bacteria and fungi comprised 4.2% of the total cases, which was less as compared to that reported by Srinivasan et al.[5] (5.1%) and more than that reported by Bharathi et al.[10] (2.4%).

We observed that 31 (21.8%) culture-positive cases demonstrated bacterial etiology, of which S. aureus was the most frequently isolated organism (51.6%), followed by Streptococcus pneumoniae (22.5%) and Staphylococcus epidermidis (19.3%). This was consistent with a similar study in Bengal.[14] However, studies in Nepal[13] and Ghana[11] found S. pneumoniae as the most frequently isolated bacterial pathogen. A history of contact lens wear was present in two patients in the study, out of which Pseudomonas species and S. aureus were isolated in one case each.

  Conclusion Top

The results of our present study showed trauma due to wooden objects as the most common predisposing factor in causing infective keratitis.

Fungi predominated the culture-positive cases, with Aspergillus species being the predominant fungal agent, while S. aureus was the predominant bacterial pathogen. This study was carried out primarily to identify the specific pathogens responsible for corneal ulceration in eastern India and determine the demographical characteristics of the population at risk for corneal ulceration and also the different factors which can predispose to the development of an ulcer. This knowledge can be useful for defining the magnitude of problem in this part of the country and providing a base for further research work.

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Conflicts of interest

There are no conflicts of interest.

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  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]


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