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 Table of Contents  
Year : 2021  |  Volume : 33  |  Issue : 1  |  Page : 39-43

Etiological diagnosis of microbial keratitis in a tertiary care hospital in Lucknow

1 Department of Microbiology, Maulana Azad Medical College, Delhi, India
2 Department of Microbiology, King George's Medical University, Lucknow, Uttar Pradesh, India
3 Department of Ophthalmology, King George's Medical University, Lucknow, Uttar Pradesh, India

Date of Submission20-Jun-2020
Date of Decision31-Jul-2020
Date of Acceptance06-Aug-2020
Date of Web Publication19-Apr-2021

Correspondence Address:
Dr. Nazia Khan
E-103, Abul Fazal Enclave Part-1, Near Hari Kothi, Jamia Nagar, Delhi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/kjo.kjo_85_20

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Context: Microbial keratitis is a sight-threatening infection which can lead to devastating outcome if not managed timely and rightly. Aim: The aim is to study the etiology and assess the risk factors of infectious keratitis in patients presenting to the Ophthalmology Department in King George's Medical University, Lucknow (Uttar Pradesh), India. Setting and Design: The study was conducted at the Microbiology and Ophthalmology Department of King George's Medical University, Lucknow. This was a prospective, observational study. Subjects and Methods: A total of 120 corneal scrapings were performed in patients presenting with corneal ulcers between August 2016 and July 2017. Gram staining, KOH mount, and culture on blood agar and Sabouraud's dextrose agar were done for all the scrapings for the identification of bacterial and fungal isolates. Statistical Analysis: None. Results: Microbial etiology was established 34.17% of scrapings. The most common risk factor was trauma (56.7%) of which vegetative trauma was maximum (31/68). Among 41 positive cultures, 34.14% were bacterial while 65.85% were fungal in etiology. The most common bacterial and fungal isolates were coagulase-negative Staphylococcus spp. (50%) and Aspergillus spp. (25.93%), respectively. Conclusion: Trauma was the most common predisposing factor for microbial keratitis in our setting. Fungal infections were more common than bacterial. The “regional” findings play an important role in public health implications to understand the etiology better and to initiate appropriate treatment.

Keywords: Microbial keratitis, sight threatening, trauma

How to cite this article:
Khan N, Banerjee G, Gupta P, Kishore P, Sharma A. Etiological diagnosis of microbial keratitis in a tertiary care hospital in Lucknow. Kerala J Ophthalmol 2021;33:39-43

How to cite this URL:
Khan N, Banerjee G, Gupta P, Kishore P, Sharma A. Etiological diagnosis of microbial keratitis in a tertiary care hospital in Lucknow. Kerala J Ophthalmol [serial online] 2021 [cited 2021 Jun 13];33:39-43. Available from: http://www.kjophthal.com/text.asp?2021/33/1/39/314107

  Introduction Top

Keratitis is an inflammation of the cornea produced by infectious organisms or noninfectious agents or stimuli.[1] Microbial keratitis is a potentially sight-threatening infectious corneal inflammation, which can be caused by bacteria, virus, fungi, or parasite.[2] In some developing tropical countries, corneal infections are the second most common cause of monocular blindness after unoperated cataract. Corneal ulceration has been labeled as “silent epidemic” in developing countries[3] [Figure 1].
Figure 1: Corneal ulcer

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Infectious keratitis imposes diagnostic dilemma because of varied presentations, and prompt antimicrobial treatment should be initiated after clinical and microbiological evaluation to minimize its devastating complications and sequelae.

It has been found that the etiological and epidemiological pattern of corneal ulcers varies with patient's population, health of cornea, geographical location, and seasonal variation and also with time.[4] Thus, it is important to carry out local studies periodically to be aware of the local disease trend and sensitivity pattern.

This study was thus conducted to study the etiology and assess the risk factors of infectious keratitis in patients presenting to the Ophthalmology Department in King George's Medical University, Lucknow (Uttar Pradesh).

  Subject and Methods Top

It was a prospective study conducted on 120 patients with corneal ulcers presenting to the cornea clinic in the Department of Ophthalmology in King George's Medical University, Lucknow, from August 2016 to July 2017. Consent was taken from the patients/guardians before enrollment, and patients of all groups were included in the study. Ethical clearance was obtained by Ethics Committee of King George's Medical University.

Data were collected in a brief predesigned format. It included patient's name, age, sex, occupation, duration of symptoms, history of (H/O) ocular trauma, contact lens wear, bathing in pond water, any associated ocular illness, systemic illness, therapy received before presentation, and clinical examination. Corneal scrapings were performed under strict aseptic conditions by an ophthalmologist after instillation of 4% lignocaine without preservative using sterile Bard-Parker needle (No. 15) under slit lamp magnification.[5],[6] The material was taken from the leading edge and base of the ulcer. It was placed in a C-shaped streak on the 5% sheep blood agar (SBA) plate and two Sabouraud's dextrose agar (SDA) plates. Any growth on C streak was considered to be significant. Another sample was taken for Gram staining and 10% KOH mount.[7] One set of SBA and SDA plate were incubated at 37°C, and the other SDA plate was incubated at 25°C. SBA plate was considered sterile if no growth was observed within 48 h, and SDA plate was considered sterile if no growth was found in 28 days. The specific identification of bacterial colonies was done by Gram staining, and standard tests using standard laboratory protocols and fungal colonies were identified by their colony characteristics on SDA and morphological appearance of the hyphae and spores in lacto phenol cotton blue mount.

  Results Top

Microbial etiology was found in 34.17% of cases (n = 41).

Of 120 clinically suspected corneal ulcers, males showed higher preponderance (68.33%; n = 82) when compared to females owing to more outdoor work profile (31.67%; n = 38). The most common age group of presentation was 41–65 years (46.67%, n = 56), and majority of the patients belonged to the rural background (85%; n = 102). Out of the patients involved in outdoor work, farmers were maximum affected (73.9%; 51/69).

H/O ocular trauma could be elicited in 56.67% (n = 68) of the patients, and injury due to vegetative material (45.59%; n = 31) was the leading cause of ocular trauma.

Around 57.5% (n = 69) of the affected individuals presented to the outpatient department after >4 weeks of symptoms as majority of them had sought medical aid from local practitioners or quacks or local medical shops and visited our hospital mainly when their symptoms were either not resolving or worsened [Table 1].
Table 1: Distribution of patients according to history of prior consultation/treatment before presenting to the hospital (n=120)

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Fungal isolates were recovered from 22.50% (n = 27) of samples [Figure 2] whereas bacterial isolates from 11.67% (n = 14) of samples. Aspergillus spp. (25.93%; n = 7) was the most common isolated fungal isolate followed by Fusarium spp. (18.52%; n = 6) and Alternaria spp. (18.52%; n = 5). Coagulase-negative Staphylococcus spp. (CONS) predominated the bacterial isolates (50%; n = 7), while Pseudomonas spp. (0.83%; n = 1) was the least common bacterial isolate [Table 2] and [Table 3].
Figure 2: Growth of fungal spp. on Sabouraud's dextrose agar

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Table 2: Bacterial pathogens isolated from 14 culture-positive bacterial keratitis cases

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Table 3: Fungal pathogens isolated from 27 culture-positive fungal keratitis cases

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Taking culture as the gold standard, the sensitivity and specificity of 10% KOH are 81.5% and 78.5%, respectively, and the sensitivity and specificity of Gram stain are 29.6% and 93.5%, respectively, for the fungal isolates. The sensitivity and specificity of Gram staining for bacterial isolates are 100% and 70.8%, respectively [Table 4],[Table 5],[Table 6].
Table 4: Comparison of Sabouraud's dextrose agar culture and 10% KOH mount for fungal isolates

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Table 5: Comparison of blood culture and gram stain for bacterial isolates

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Table 6: Comparison of Sabouraud's dextrose agar culture and Gram stain for fungal isolate

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  Discussion Top

Microbial etiology of keratitis in our study was found to be 34.17%. This is lower when compared to the study by Tewari et al. which was 59.3%, the study by Bharathi et al. which was 69.59%, or other Indian studies.[4],[8] All the patients had unilateral eye involvement.

Female: male ratio was found to be 1:2.16. This is more attributed to outdoor work done by males. Affected patients generally belonged to 40–65 years of age group (46.67%) which is similar to Chhangte et al. where 53.9% of cases were of the same age group.[5]

Majority of the patients were from rural background (around 85%). Major bulk of Indian population live in rural areas, and they are more involved in manual labor; thus, they have more chances of injuries and infections as compared to desk job people in the urban setup. Trauma as a whole accounted for 56.67% of all the cases, thus being the most common predisposing risk factor. Similar findings of trauma have been seen in Paraguay with 48%,[9] Eastern Nepal with 53%,[10] South India with 65%,[11] and Eastern India with 83%[12] of all the keratitis cases.

Most of the traumatized patients were outdoor workers (70.59%).[13] Sitoula et al. also showed trauma to be the most common risk factor in their study.[14] Among the patients enrolled, 47.50% had encountered corneal trauma mainly from vegetative matter and less commonly from dust, insect bite, or any other cause. Out of these, 15% (n = 18) of the patients had systemic illness in the form of blood pressure, diabetes, rheumatoid arthritis, facial palsy, seizure, thyroid, asthma, or heart surgery, while 15% (n = 18) patients presented with ocular injuries such as cataract, glaucoma, vitreous prolapse, or any operative procedure. None of our patients had H/O using contact lenses.

Of 120 corneal scrapings performed, 65.83% (n = 79) of the cultures were sterile and 34.17% showed growth. Total microbial etiology of 34.17% is less as compared to other studies by Tewari et al. and Bharathi et al. with a recovery of 59.3% and 69.59%, respectively, but is in accordance with study by Gupta et al. where 38.3% of cases were culture positive.[4],[6],[15]

Bacterial growth was seen in 11.67% (n = 14) of the cultures, whereas 22.50% (n = 27) of the cultures showed fungal growth. Growth rate is lower when compared to other studies such as Bharathi et al. (34.98%), Tewari et al. (38%), Kumar et al. (26.5%), and Basak et al. (28.8%).[4],[6],[12],[16] This reduction in bacterial corneal ulcers at the referral centers can be credited to better treatment outcome at peripheral centers since the introduction of topical fluoroquinolones in the late 1990s.[17]

Among 11.67% of the bacterial cultures positive, 50% (n = 7) showed growth of CONS, 28.57% (n = 4) of Staphylococcus aureus, 1.67% (n = 2) of Streptococcus pneumoniae, and 7.14% (n = 1) of Pseudomonas spp. The isolation rate of CONS (60%) is almost similar to the study by Tewari et al.[4] The most common bacterial infection in Nepal and South India was S. pneumoniae and in Ghana and Bangladesh was Pseudomonas spp. Gram-positive bacilli were not observed in the present study. This differs from various studies that have demonstrated a 4.0%–12.5% incidence.[12],[18],[19] We isolated only one Gram-negative isolate which was Pseudomonas spp. This is in contrast to other studies where the isolation of Gram-negative organisms has been as high as 39.7% by Tewari et al.[4]

Fungal positivity was seen in 22.50% of the cultures. This isolation rate is lower when compared to studies done by Sitoula et al.(70%), Leck et al. (44.1%), Srinivasan et al. (51.9%) and Basak et al. (59.3%) but is almost similar to Bharathi et al. (32.26%).[5] Out of the 22.50% positive fungal cultures, Aspergillus spp. is the most common fungal isolate (25.93%; n = 7) followed by Fusarium spp. (22.22%; n = 6), Alternaria spp. (18.52%; n = 5), Curvularia spp. (14.81%; n = 4), and Candida albicans (7.41%; n = 2), and 3.7% (n = 1) cases showed Acremonium spp., Aureobasidium pullulans, and Cladosporium spp. Aspergillus spp. has been found to be a common fungal isolate in West Bengal (Basak et al.), Nepal (Upadhyay et al), and Bangladesh (William et al.) as well.[3] In contrast, the prevalence of fungal corneal ulcers in developed countries was as low as 20% in Florida[20] to 3% in the UK.[21] However, Fusarium spp. was the most common cause of fungal keratitis in South India, Western India, and few studies from abroad.[8],[12],[22],[23] A. pullulans was an unusual pathogen isolated in the study.

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  References Top

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  [Figure 1], [Figure 2]

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


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