|Year : 1981 | Volume
| Issue : 3 | Page : 177-182
The correlation between environmental and ocular fungi
DK Sandhu, IS Randhawa, Daljit Singh
Department of Ophthalmology, Medical College, Amritsar, India
D K Sandhu
Department of Ophthalmology, Medical College, Amritsar
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sandhu D K, Randhawa I S, Singh D. The correlation between environmental and ocular fungi. Indian J Ophthalmol 1981;29:177-82
The fungi most often isolated from human corneal ulcers are also known to inhabit the normal eyes and also commonly occur as saprobes in the soil and vegetable matter. Due to the abundance of fungi in the surroundings of man, it is difficult to assign a pathogenic role to them, when they are isolated from the diseased eyes. The problem is further aggravated by the presence of predisposing factors like the use of immunosuppressive agents, antibiotics and physical injury to the eye. It was therefore thought that a simultaneous study in infected human eyes, normal human eyes and the surroundings would be of help in elucidating some aspects of fungal infections of the eye.
| Materials and methods|| |
Conjunctival swabs of 128 normal and 140 corneal ulcer eyes were taken with the help of sterilized cotton swabs dipped in normal saline. Direct microscopic examination of the specimens was done after digestion of a loopful of material in 10 per cent KOH. The specimens were cultured on Sabouraud's glucose agar with and without antibiotics and incubated at 28 degree C. The prevalence of aerial fungal spores was studied by petri plate exposure method from month of July to June.
The fungi isolated from the diseased human eyes were tested for sensitivity to antifungal agents which included cyclohexamide, copper sulphate and garlic extract.
| Observations|| |
A. Cases of corneal ulcers
Eye swabs from 140 cases of corneal ulcers included 87 males and 53 females. Fungi were positive in 32.14 per cent, yielding 14 different fungi [Table - 1].
Aspergillus was found to be the most predominant fungus. Other fungi commonly isolated were Alternaria, Curvularia, Fusarium, Helmenthosporium and Cladosporium.
The incidence of positive cases amongst the males was 32.18 per cent compared to 32.07 per cent in the females.
The maximum number of patients belonged to the age-group 21-30 years. The prevalence of fungi was also highest in this group (35.06 per cent).
The patients included farmers, labourers, housewives, students and others. The highest percentage of positive cases was seen amongst labourers and farmers (41.38 per cent and 34.0 per cent respectively).
The prevalence of fungi was 37.23 percent in the rural patients as compared to 21.73 per cent in the urban patients. A history of foreign body like mud and dust etc. was recorded in 60 cases out of which 25 (41.66 percent) were positive for fungi.
The percentage of positive fungi was higher amongst those receiving antibacterial antibiotics (35.41 percent) compared to those receiving antifungal (24.0 per cent) or no treatment (26.31 percent).
There was an apparent seasonal variation in the frequency of corneal ulcers. Maximum number of cases were recorded in the months of August, September and October (44.28 percent) while minimum were recorded in the months of December and January (9.28 percent).
B. Normal eyes
Out of 128 healthy eyes investigated 26.56 percent were positive for fungi. Again, the most common fungus was Aspergillus. Positive results were obtained in 25.35 per cent males and 28.07 percent females.
The prevalence of fungi and their seasonal variations in the normal eyes with regards to age, sex and occupation of the subjects was similar to that observed in cases of corneal ulcers. [Table - 1] compares the fungi isolated in cases of corneal and the normal eyes, as well as with the atmospheric fungi.
C. Atmospheric studies
Petri plates were exposed for a total of 186 days, between July 1977 and June 1978. A total of 2913 colonies belonging to 23 different fungi appeared in the plates [Table - 1], [Figure - 1][Figure - 2]
The highest number of fungal colonies was recorded in the month of October followed by November. The total colony counts remained at a low level from December to January. The predominance of fungal colonies was observed in the case of Aspergillus followed by Alternaria, Curvularia and Fusarium.
All the 14 varieties of fungi isolated from the cases of corneal ulcers were tested for sensitivity to the following agents : 1 . Cyclohexarnide. 2. Copper sulphate. 3. Garlic extract. [Table - 2]
The minimum inhibitory concentration (MIC) of cyclohexamide was highest (0. 1 mg ml) for A. flavus, while it was lowest (0.005mg/ ml) for Cephalothesium roseum and Torula sp. Copper sulphate was most effective against C. roseum showing a MIC of 0.35 mg/ ml, while the MIC for Curvularia sp. and Trichoderma sp. was 0.95 mg/ml. Garlic extract inhibited the growth of 8 out of 14 fungi at a concentration of 1.00 mg/ml (dry weight), while a concentration of 2 percent inhibited all the fungi.
| Discussion|| |
Aspergillus was the most common fungus associated with corneal ulcers in the present study. This is in conformity with earlier reports from other parts of the world,. However in India even higher prevalence of Aspergillus has been reported : 35 percent from Pondicherry, 54 percent from Madras, 41.7 percent from Pondicherry and 7 percent from Amritsar.
Out of other commonly encountered fungi i.e., Alternaria, Curvularia and Fusarium, the first two cause keratomycosis rarely while the last has been shown to be associated with pathogenesis of corneal ulcers.
The frequency of positive cultures was the same in the males and the females contrary to other reports from India, where it has been reported to be higher in males,. The higher prevalence in the females could be attributed to the use of mascara etc. already contaminated by fungi.
The higher prevalence of fungi for the age group of 21-40 years may be due to the fact that adults are more active as compared to children and older people and hence their eyes are more exposed to foreign matter and infection. Similarly, the corneal ulcers as well as fungal isolations were more frequent in labourers and farmers who come in direct contact wth vegetable matter and are prone to injury as compared to other occupational groups. Physical injury to the eye is one of the common predisposing factors for corneal ulcers. In the present study 60 patients out of 140 has physical injury and 25 (41.66 percent) were positive for fungi. The treatment with antibacterial antibiotics apparently promotes higher prevalence of fungi by disturbing the ecological balance in favour of fungi,.
The percentage of positive cultures amongst healthy subjects was 25.56 percent as compared to 32.14 percent amongst the patients. The prevalence of fungi in the normal eyes has been shown to vary from 2 percent to 52 percent. which may be related to the number of samples investigated and different climatic conditions. The commonest fungus was Aspergillus which was also encountered in appreciable numbers in the atmosphere.
All the 14 fungi isolated from corneal ulcers were prevalent in the atmosphere and 11 of these were also isolated from the healthy eyes [Table - 1]. Some of these fungi like Aspergillus, Alternaria, Curvularia, and Fusarium were common in the eyes of the patients, healthy persons and the atmosphere. Further there were seasonal variations in the occurance of atmospheric fungi with a corresponding increase in the occurance of positive cases amongst the patients and the healthy individuals [Figure - 2].
A similar correlation has been found between atmospheric fungal spores and fungi associated with eyes and nose. This is further supported by the fact that repeated cultures of normal eyes at intervals yield varying types of fungi. Therefore the condition of the eyes with respect to their microbial flora at the moment of trauma would determine to a large extent, the nature of the infection. From the above it appears that fungi represent incidental or transient spores in the eye except in those cases where some of them may get an opportunity to cause invasion of the tissues to a variable degree.
Therapy of fungus infections of the eye is a difficult job because very little is known about the biology of the fungi especially their pathogenesis. The problem of therapy is further made difficult by the fact that many of the drugs active against a wide spectrum of fungi in vitro suffer from their inability to penetrate into the host tissues. Almost all the polyene antifungal antibiotics are limited in their use as therapeutic agents because of being insoluble in water, unstable, toxic, irritating and having a number of side effects.
All the fungi tested were sensitive to cyclohexamide in far smaller doses as compared to copper sulphate and garlic extract. Although cyclohexamide is toxic to human skin, it has been tried successfully in a case of Fusarium keratitis. There was not a wide range in the MIC of copper sulphate for various fungi. In view of the easy availability and relative irontoxicity to the skin and conjunctiva, regular washings with copper sulphate with copper sulphate in cases of corneal ulcers may be of great help.
Garlic extract has a wide range of antimicrobial activity. It has been shown to inhibit the growth of many pathogenic fungi in vitro. In the present study, a 0.1 percent solution inhibited 8 out of 14 fungi, whereas a 0.2 per cent solution inhibited all the fungi. The active component of the garlic extract is supposed to be allicin which probably disrupts cell metabolism by inactivating proteins.
Keeping the above in view, it will be of great help if substances like garlic extract can be employed for treatment of fungat infections because its activity is differential, being injurious to the fungal cells, but not to mammalian cells in tissue cultures and it was a wide spectrum of - activity against a large number of fungi invitro.
More intensive studies are required about the isolation and characterization of the active components of garlic extract.
| Summary|| |
The correlation between environmental and ocular fungus has been done. Some antifungal agents were also evaluated.
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[Figure - 1], [Figure - 2]
[Table - 1], [Table - 2]
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