|Year : 1985 | Volume
| Issue : 5 | Page : 289-293
Bacterial and mycotic agents of corneal ulcers in Vellore
Sheila Panhalkar1, Anna Thomas2, TA Alexander2, Grace Koshi1
1 Department of Mirobiology, Christian Medical College Hospital, Vellore, India
2 Department of Ophthalmology, Christian Medical College Hospital, Vellore, India
Department of Mirobiology, Christian Medical College Hospital, Vellore
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Panhalkar S, Thomas A, Alexander T A, Koshi G. Bacterial and mycotic agents of corneal ulcers in Vellore. Indian J Ophthalmol 1985;33:289-93
|How to cite this URL:|
Panhalkar S, Thomas A, Alexander T A, Koshi G. Bacterial and mycotic agents of corneal ulcers in Vellore. Indian J Ophthalmol [serial online] 1985 [cited 2020 Aug 12];33:289-93. Available from: http://www.ijo.in/text.asp?1985/33/5/289/30733
Infections of the cornea are generally produced by opportunistic bacteria and fungi that invade already diseased or injured tissue. The Bacterial and fungal agents responsible for corneal ulcers vary in different geographical regions,,.
Though the commonest agents of healthy conjunctivae have been reported as Staph albus and diphtheroidss, Soundakoff have found that S. albus & S. aureus were almost equally present. Agarwal found B. subtilis and micrococci in 20 & 23% patients respectively. On the other band fungal agents were found in 27.4% by Ainley & Smiths and in 2-9% by Williamson et al; but Agarwal et al  found an incidence of 6.0% while fungi were detected in 22.2% of cases by Nema et al in India However, the cornea is usually remarkably resistant to infection.
We report here results of a study undertaken to delineate the bacterial and mycotic agents involved in health and disease of the cornea.
| Materials and methods|| |
The subjects included were 130 patients with symptoms and signs of corneal ulcers who attended this hospital. The extent of ulceration was determined by instillation of fluorescein dye. Controls included 141 subject of both sexes with vague complaints and no history or obvious signs of eye infection and who had not taken any antibiotics (drops or systemic) during the previous 3 months.
Materials for microbiological studies were collected with two sterile cotton swabs, two minutes after instillation of 4% xylocaine into the affected eye and after gentle scraping of the ulcer with a platinum spatula. In healthy controls, a swab of both conjunctival sacs was done gently, using sterile saline moistened swabs.
One swab each from cases with corneal ulcers and controls were used for making smears for Gram stain, KOH (10%) preparation, Giemsa stain and Periodic Acid Schiff (PAS) stain. The Gram . stained smear was examined for bacteria, candida or actinomycetes. The KOH preparation, Giemsa and PAS stained smears were examined for the presence of true fungal filaments or spores.
Conventional procedures were followed for bacterial and mycotic cultures,.
The second swab from each subject was used to inoculate sheep blood agar (BA), Chocolate agar (CA), MacConkey agar (MA) and a tube of thioglycollate broth (TB) for bacterial isolation. All media were incubated at 37°C and CA in an atmosphere of 5-10% C0 2 , Antibiotic susceptibility tests were done by the disc diffusion technique.
For fungal agents, the swab was inoculated on duplicate media of Sabouraud's dextrose agar. (SDA), with and without antibiotics, brain heart infusion agar and BA, and incubation done at 37°C and at room temperature (RT) appropriately Slide cultures were done using sporulation media to determine further characteristics for identification.
| Observation|| |
Among the 141 healthy controls, 123 (87.2%) yielded some bacterial agents while only 2 (1.4%) yielded fungal agents from the normal conjunctiva. Some subjects yielded mixed flora. The frequency of distribution of common organisms isolated are represented in [Table - 1]. Age-sex analysis did not reveal any significant differences in normal flora. A group of 30 healthy subjects who had antibiotic treatment in the past for other ailments and hence were excluded from the study, had similar organisms isolated in higher percentages, including 10% S. aureus as against 4.9% S. aureus in the healthy controls, showing the probable influence of antibiotics on normal flora.
Out of the 130 corneal ulcers studied in detail, etiologic agents were isolated from 110 (84.6%) of which bacterial agents accounted for 79.2% and fungal agents for 5.4%. Some direct KOH preparation and PAS staining were helpful and there was a correlation of microscopic and culture findings. The variety of bacterial agents isolated from corneal ulcers is shown in [Table - 2]. The degree of growth obtained is indicated. The types of agents involved w°re entirely different from those in normal conjunctiva. Streptococcus pneumoniae (23.8%) and Pseudomonas species (19.2%) were the commonest and were obtained mostly in moderate to heavy growth S. albus & B. subtilis were notable for their scanty yield from corneal ulcers. Other bacteria of significance were S. viridens S. aureus and many gram negative bacilli including H. influenzae & H. aegypti. 133 bacterial agents were isolated from 110 subjects among the 130 cases with corneal ulcers; thus polymicrobial agents were isolated from some patients.
The 7 fungal agents isolated included 3 Aspergillus species, 3 Fusarium species, and one unidentified fungus. Moderate to heavy growth was present in all.
Whereas, the commonest etiologic agent S. pneumoniae, was sensitive to penicillin, tetracycline and cbloramphenicol, 23 out of the 25 strains of pseudomonas and 2 out of the 3 Proteus vui'garis were resistant to common antibiotics included in topical preparations namely Penicillin, Streptomycin, Chlorampbenicol, Tetracycline, . Erythromycin etc.
| Discussion|| |
Early diagnosis, knowledge of the agents involved and appropriate therapy are of utmost importance for prevention of ocular impairment as a result of corneal ulcers. In our study a variety of media were used to recover maximum bacterial and mycotic flora present in the conjunctiva and corneal ulcers. The bacteria we encountered in the normal conjunctivae were similar to that reported earlier,. Though B. subtilis was less frequently recovered by others. Our higher isolation of B. subtilis was similar to those of Agarwal et al. It is possible that the dry and dusty atmosphere of a tropical and subtropical climate as found in different regions of India, is conducive to the higher presence of B. subtilis in the air, dust, bath water, as well as fomites and body surface. However, it is noteworthy that S. albus and B. subtilis, the commonest agents in normal conjunctivae were rarely present in corneal ulcers and when present were recovered in scanty amounts.
The overall isolation of bacterial agents from 79.2% of subjects with corneal ulcers were almost similar to those from normal conjunctivae, though in the normals large number of agents gave scanty growth. It is interesting to note that the commonest bacterial agent detected in the corneal ulcers in this study S. pneumoniae (23.8%), were not present in normal conjunctiva. Pseudomonas, the second common organism (19.2%) in corneal ulcers, was present in only 0.7% of normal conjunctivae. Both these organisms and a variety of other new agents were recovered in moderate to heavy growth. On the other hand, S. albus and B. subtilis and other common flora found in healthy conjunctiva, were recovered in scanty amounts showing their relative unimportance in corneal ulcers. Very high incidence of S, aureus found by Bat et a1, might have been due to the associated conditions of patients. Of the 6 S. aureus isolates we had, 5 showed scanty growth.
The S. pneumoniae, pseudomonas and other pathogenic organisms recovered from corneal ulcers might have primarily gained entry to the injured devitalised or diseased cornea from neighbouring sites like nose, ear & throat where they exist as normal commensals. Some agents might have been introduced through contaminated foreign bodies or from air, water and fomites. Eighty two (63%) of our patients gave a history of prior trauma and three had used native herbs. Trauma was commonly caused by a stick, paddy leaf, grain, sand or dust. Twentynine of the patients giving histories of trauma were farmers, 13 were coolies & 25 were housewives whose chores included sweeping, cleaning of grains for food, preparation of meals with open fires, and some were field workers. Other studies, have shown as in ours, that Gram negative bacilli of diverse types were isolated with higher frequency. This may be a reflection of widespread unrestricted use of broad spectrum antibiotics leading to elimination of susceptible organisms and emergence of multi-drug resistant Gram negative bacilli. Introduction of agents through unsterile ophthalmic preparations is also a possibility.
The isolation rate of fungi from a normal conjunctivae were rather low in our study despite using a battery of media and tests. It is to be noted that Wilsonj recovered a majority of fungal isolates from the eye lids rather than from the conjunctivae.
In our study, great care was taken to swab only the conjunctivae. The fungal agents were isolated in 5.4% of corneal ulcers in our study, as against 1.4% from normal conjuntiva. The fungi isolated included Fusarium and Aspergillus in 3 cases each and an unidentified fungus in 1 patient. Puttanna found Aspergillus species to be the commonest followed by Penicillium, Fusarium, Rhizopus, Candida, etc. Others also have reported on frequent isolation of candida,. We did not find any Candida though it is a common fungal isolate. Thus we found less common occurrence of keratomycosis in our patients as compared to bacterial agents causing corneal ulcers despite a significant proportion giving history of trauma.
Most fortunately the commonest agent S. pneumoniae was amenable to treatment. Varying antibiotic susceptibilities of agents particularly the Gram negative rods were noted. This finding emphasises the necessity for isolation of agents and determination of the antibiotic susceptibility for effective treatment of corneal ulcers.
| Summary|| |
In a study of 130 patients with corneal ulcers, 63% gave a history of preceding trauma. Bacterial etiology was found in 79.2%, S. pneumoniae being the commonest agent closely followed by Pseudomonas species and S. viridans. Most pathogens were isolated in moderate to heavy growth Fungal agents were found in 5.4%, the common agents being the Aspergillus species and Fusarium species, equally represented. The concurrent study in 141 healthy controls revealed that S. albus, B. subtilis, Micrococci and Diphtheroids were commonly present in normal conjuctivae, most of them in scanty amounts. Surprisingly, the normal commensals of conjunctivae were less often encountered as agents of corneal ulcer.
| References|| |
Nema, H V., Ahuja. O.P., Bat. A. and Mohapatra, L.N, (1966). Am J. Ophthalmol. 62 :968.
Bal. A, and Nema, H.V. 1667. Acta, Ophthalmol. 45: 247.
Ostler. H.B. and Okwnoto, M. 1976. Am. J. Ophthalmol. 81 :518.
Puttanna, S T. 1957. J. All -India Ophtha!mol. Soc. 15:
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Carson, L. and Winkler, C.H. 1954. Arch. Ophthalmol. 51 : 196.
Agarwal. L,P. and Khosla, P.K. 1967. J. All India Opthalmol. Soc. 15: 1.
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Zimmerman, L.E. 1962. Mycotic keratitis. Lab. Invest. 11 :1151-1159.
Myers, R.M and Koshi, G. 1982. Diagnostic Procedures in Medical Microbiology & Immunology/ Serology. IELC Concordia Press, Vaniyambadl, Tamil Nadu, 635, 751.
Emmons, C.W., Binford. C.H., Utz, J.P. and Kwon-Chung, K.J 1977. Medical Mycology, 3rd ed. Lea and Febiger, Philadelphia, 535-549.
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[Table - 1], [Table - 2]
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