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Year : 1971  |  Volume : 19  |  Issue : 3  |  Page : 130-135

Bacterial and fungal flora of the normal eye

Department of Pathology & Bacteriology, G. S. V. M. Medical College, Kanpur, India

Correspondence Address:
Hari Saxena
Department of Pathology & Bacteriology, G. S. V. M. Medical College, Kanpur
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Source of Support: None, Conflict of Interest: None

PMID: 15744983

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How to cite this article:
Saxena H, Goswami P. Bacterial and fungal flora of the normal eye. Indian J Ophthalmol 1971;19:130-5

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Saxena H, Goswami P. Bacterial and fungal flora of the normal eye. Indian J Ophthalmol [serial online] 1971 [cited 2021 May 11];19:130-5. Available from: https://www.ijo.in/text.asp?1971/19/3/130/34978

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Table 1

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Table 1

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Ocular infections are commonly treated with broad spectrum anti­biotics and or corticosteroids with­out microbiologic studies and it is only clinical failure in therapy that suggest incorrect diagnosis. One of the main reasons for irra­tional treatment is lack of swift methods of laboratory verification of microbiologic agents and their sensitivity results, available in most laboratories, Rising incidence of mycotic infections of the eye has been well documented, Haggerty and Zimmerman, [5] and Anderson, Roberts, Gonzales and Chick, [3]).

It has been suggested that the incidence is associated with in­creasing use of antibiotics and or corticosteroids. Mitsui and Hana ­reported four cases of cor-busa [9] neal ulcer due to fungi following cortisone therapy and also demon­strated that the use of topical corticosteroids for three weeks in previously negative persons yield­ed fungus in almost 50% eyes. Ainley and Smith [2] however failed to obtain such results in similar study. Experimentally Agarwal, Malik, Mohan and Khosla [1] pro­duced mycotic corneal ulcers with intracorneal injections of Asper­gillus and Candida species.

The incidence of normal fungal flora in healthy eyes shows con­siderable variation in reported series from 2.9% (williamson, Gordon, Wood, Dyer and Yahya, [11] ) to 27.9 % (Ainley and Smith [2] ). In India surprisingly very few studies have been done. Sinha and Das [10] reported 13.4% incidence in Gujeratees of Calcutta. The need for many such surveys is obvious. The present study was planned to determine the indige­nous bacterial and fungal flora of the eye in both sexes at all ages and to study the effect of topical corticosteroids on its incidence.

  Material and Methods Top

A total of 307 individuals form the material for this communica­tion. All were considered normal on the basis of Clinical evaluation of the eye with special emphasis on absence of erythema oedema and discharge from the eyes, at­least for a fortnight before. The subject were either patients who attended the out patient depart­ment for minor ailments not re­lated to eyes or comprised of medical students and technical staff of the college. It was thought desirable to include equal number of both sexes of different ages to represent infant, child, adult, middle age and old age.

Conjunctival swabs were taken from both eyes for smear and culture and streaked over the surface of blood agar, nutrient agar and sabouraud's dextrose agar for bacteria and fungi. Bacterial cul­tures were incubated at 37° C for 24-48 hours and colonies identi­fied by conventional methods.

The cultures for fungi were incubated at 25° C and screened for growth every week for four weeks before being labelled as negative. The fungi were identi­fied on the basis of colonial characters, microscopy, and sugar fermentation reactions. Candida albicans was diagnosed on the basis of chlamydospore formation on corn meal agar.

For control blank cultures were exposed to the atmosphere in the vicinity of patient for roughly the same time, taken for swabbing of eye and inoculation over the media and incubated for the same length of time.

  Observations Top

Of a total number of 307 in­dividuals included in this study for investigation, 55 were infants upto the age of 1 month, 68 child­ren between ages of 1-12 years, 64 adults between 15-40 years and 62 middle aged between 41­-55 years and 58 old persons bet­ween 56-82 years. The number of males and females were 156 and 151 respectively. Each group was almost equal distribution of sexes. Culture for bacterial microbes were positive in all eyes in all cases although organisms isolated from both eyes in the same individual were not necessa­rily the same. [Table - 1], shows the species and the frequency of orga­nisms isolated. The commonest organism was co-agulase negative staphylococcus albus in 264 eyes (43%), followed by C, xerosis in 216 eyes, (35.1%). C.xerosis seems to have more affinity for eyes of adults and old persons. No influ­ence of sex was noted in the colo­nisation of bacteria.

Fungus cultures

Fungi were isolated in 54 eyes (8.7%) of 43 persons (14.0%), with the lowest incidence in infants (0.32%) and the highest incidence in the middle aged (2.9%) and old persons (2.7%). The predominant species isolated was Penicillium in 21 eyes (38.8%) of 16 persons. Candida was isolated in 20 eyes (38.4%) of .15 persons. Of a total of 43 persons in whom fungus was grown 29 were females and 14 males. Candida was more com­monly seen in females (13) eyes and Penicillium was more common in male eyes (16) eyes. The species of Candida were C. albicans (13) eyes, C. pseudotropicalis (5 eyes and C. parapsilosis, 2 eyes).

Control cultures

Culture media exposed to atmos­phere near the eyes showed bacte­rial growth in one out of 25 plates (4%), comprising of co-agulase negative staphylococci. All media (25) for fungal growth were nega­tive.

Effect of topical hydrocortisone:

In 31 adults initially negative for fungi, topical hydrocortisone was instilled twice a day for three weeks and culture repeated after­wards. Fungi were grown in 9 eyes (29.0%) of 7 persons (22.5%) No appreciable difference was observ­ed in both sexes. [Table - 3] gives the details.

  Discussion Top

The present study amply con­firms that bacterial flora appear soon after birth n the external eye and continue to be present at all ages in both sexes. Similar obser­vations were reported by Wilson, Abeam, Jones and Sexton [12] who showed a 10O% presence of bacte­ria in their investigation of 312 eyes. However, Sinha and Das [10] could find bacteria in 56.7% of 67 healthy eyes. Diphtheroids, mainly C. xerosis along with staphylococcus albus form the predominant bacteria in the eyes and both are normally consider­ed coomnensals. Staphylococcus aureus was grown in 3.4 0/c of eyes and our figure compares favour­ Sinha ably with the finding of and Das [10] who reported 2.9% incidence.

Fungi were isolated from 43 persons (14%) in 54 eyes (8.7%). Our incidence is lower than that reported in published series in India and other countries and the data are summarised in [Table - 4].

This variable incidence suggests the importance of ecological diffe­rences in temperature, and humi­dity of the place and of course the number of eyes investigated and the methods employed.

Fungal isolation seems to be affected by age as infants had the lowest (0.32%) incidence which increased to 2.9% in the middle aged. Hammeke and Ellis [6] also demonstrated this variation, with 0.1 % incidence in infants and 10.3% in adults and postulated that the lower incidence in infants is due to lesser chance of ex­posure on account of infant eyes being closed, most of the time.

Females harbour fungi more commonly than males and the ratio in present work was almost 2:1. This could be attributable to increasing use of cosmetics, mas­cara and other beauty aids, already contaminated by fungi. Wilson, [12] et al grew C. parapsilosis from mascara. Apart from the varying incidence of fungi in the external eye there seems to be agreement on the species of yeast and mycelia isolated in the present study with reported work in the literature. Thus Penicillium, As­pergillus and Candida species are common in all studies. Rhodoto­rula reported by most workers in other countries has not been iso­lated by us. The only other Indian publication on fungal flora of the eye by Sinha and Das [10] does not mention isolation of Candida species.

The over all incidence of nor­mal fungi from the eye is how­ever quite low and it does not seem probable that oculomycosis is due to activation of these nor­mal fungi. It rather suggests that any fungi isolated in the normal eye are transient in nature and has been shown by Williamson," et al, in their experiments. A re­peat culture after 4 weeks in 32 positive cases, showed fungi in only 4 and the species isolated were also not similar.

It is however well documented that corticosteroids may well potentiate these commensal fungi to pathogeniciety, (Ley, [7] ) . Agar­wal,1 et al submitted experimental proof of producing corneal ulcer after injection of fungi and show­ed that corticosteroids enhance the virulence. Mitsui and Hana­busa [9] have suggested that anti­biotics and or corticosteroids therapy might convert nonpatho­genic fungi into pathogenic types. They reported 4 cases of occulo­mycosis after cortisone therapy.

Ainley and Smith [2] failed to de­monstrate the role of cortisone on the incidence of normal fungal flora. Our incidence of 29% after cortisone is almost four times more than that without topical corticosteroids, and is fairly signi­ficant.

Candida albicans is now regard­ed as the cause of many corneal infections (Mitsui and Hanabusa[9]). Manchester and George[8] reported fungal keratitis due to C. parapsi­losis.

  Summary Top

Normal healthy eyes were in­vestigated for bacterial and fun­gal flora in 307 persons of both sexes in varying age periods.

Bacteria were present in all the eyes, predominant organism was co-agulase negative staphylococ­cus albus (43%) followed by C. xerosis in 35.1% eyes.

Fungi were grown in 54 (8.7%) eyes of 43 persons (14%). The incidence was lowest in infants (0.32%) and highest in the middle aged (2.9%). Penicillium was the commonest species isolated (38.8%) followed by Candida (38.4%).

Use of topical hydrocorticone in the eyes for three weeks in­creased the incidence to 29%.

  References Top

AGARWAL, L. P., MALIK, S. R. K., MOHAN, M. and KHOSLA, P. K.: Mycotic corneal ulcers, experimen­tal production. Brit. J. Ophth. 47: 109 (1963).  Back to cited text no. 1
AINLEY, R., and SMITH, B.: Fungal flora of the conjunctival sac in healthy and Diseased eyes. Brit. J. Ophth. 49: 505, (1965).  Back to cited text no. 2
ANDERSON, B., ROBERTS, S. S., GONZALES, C., and CHICK, E. W.: Mycotic ulcerative keratitis. Arch. Ophth. (Chicago) 62: 169 (1959).  Back to cited text no. 3
FAZAKAS, A.: Zusammenfassender Bericht ubermeine ophthalmologi­schem, Pilzuntor Suchungen. Oph_ thalmological (Basel). 126: 91, (1953)  Back to cited text no. 4
HAGGERTY, T. E., and ZIMMER­man, L. E.: Mycotic keratitis. Souther. M. J. 51: 153 (1958).  Back to cited text no. 5
HAMMEKE, J. C., and ELLIS, P. P.: Mycotic flora of the conjunc­tiva. Am. J. Ophth. 49: 1174 (1960).  Back to cited text no. 6
LEY, A. P.: Experimental fungus infections of the Cornea., Amer. J. Ophthal. 42: 59 (1956).  Back to cited text no. 7
MANCHESTER, P. T. and GEORG, L. K. Corneal ulcer due to Candida parapsilosis. J. Amer. Med. Ass. 171: 1339 (1959).  Back to cited text no. 8
MITSUI, Y. and HANABUSA, J.: Corneal infections after cortisone therapy. Brit. J. Ophth. 39: 244 (1955).  Back to cited text no. 9
SINHA, B. N. and DAS, M. S.: Bacterial and fungal flora of the conjunctiva in Healthy and Diseas­ed eyes. J.. Ind. Med. Ass. 51: 217 (1968).  Back to cited text no. 10
WILLIAMSON, J., GORDON, A. M., WOOD, R., DYER, A. M. and YAHYA, O. A.: Fungal flora of the conjunctival sac. in health and disease. Brit. J. Ophth. 52: 127, (1968).  Back to cited text no. 11
WILSON, L. A., A BEARN, D. G., JONES, D. B. and SEXTON, R. R.: Fungi from the normal Outer eye. Amer. J. Ophth. 67: 52, (1969).  Back to cited text no. 12


  [Table - 1], [Table - 2], [Table - 3], [Table - 4]


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