Year : 1968 | Volume
: 16 | Issue : 1 | Page : 24--28
Bacterial flora of the conjunctiva
Dept of Pathology and Bacteriology, Moti Lal Nehru Medical College, Allahabad, India
V S Rajvanshi
Dept of Pathology and Bacteriology, Moti Lal Nehru Medical College, Allahabad
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Rajvanshi V S. Bacterial flora of the conjunctiva.Indian J Ophthalmol 1968;16:24-28
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Rajvanshi V S. Bacterial flora of the conjunctiva. Indian J Ophthalmol [serial online] 1968 [cited 2021 Apr 20 ];16:24-28
Available from: https://www.ijo.in/text.asp?1968/16/1/24/37489
In the conjunctival sac the organisms are comparatively scanty considering the fact that it is constantly exposed to the atmosphere. The conjunctiva may owe its comparative freedom from micro-organisms, primarily, due to a highly potent lytic enzyme, lysozyme. FLEMMING AND ALLISON  showed that tears had a high bactericidal power and were capable of dissolving certain saprophytic cocci in a dilution of 1/40,000. A large number of bacteriological culture reports of conjunctiva are available in the literature. The widespread use of antibiotics has been associated with changes in the type and antibiotic sensitivity of bacteria inhabiting the human body as well as those which are responsible for producing disease.
Coagulase negative staphylococci are the organisms most commonly isolated from conjunctiva (ORFILA and COURDEN  ; AGARWAL and KHOSLA  ; NEMA, BAL NATH and SHUKLA and HABIB, LAURETTI and ITO  ). The other organisms isolated included diphtheroids, Coagulase positive staphylococci, Streptococcus pyogenes, pneumococci, gram positive spore bearing bacilli and various gram negative coliform bacilli. KANSKI  in a study of the conjunctival bacterial flora in dead bodies found E. colt in maximum numbers in isolates 9 hours after death.
MATERIAL AND METHODS
The present report is based on the bacteriological culture results of the conjunctiva from 102 patients referred to the Department of Pathology and Bacteriology from Manohar Das Eye Hospital, Allahabad and from other hospitals of the town during the period from December 1963 to June 1967. Most of these patients were for operation of cataract and were not suffering from inflammation of the conjunctiva at the time of culture. The findings of the present study, thus, represent the normal bacterial flora of the conjunctiva.
The conjunctival swabs were cultured on to blood agar, chocolate agar and nutrient agar plates within half an hour of collection. The culture plates were examined after 24 and 48 hours of incubation at 37°C under aerobic conditions. The staphylococcal strains isolated were investigated for pigment production, beta-haemolysis on blood agar plates, mannitol fermentation and coagulase production. Staphylococci having a combination of the above characterstics were grouped as Staphylococcus aureus (the pathogenic strains) and the others were grouped as staphylococcus albus (the nonpathogenic strains). Since coagulase production is the most convenient and reliable single test for determining the pathogenicity of a staphyloccus (CHAPMAN BERENS, NILSON AND CRUCIO  , GILLESPIE, DAVENISH AND COWAN  ; FAIRB R O T H E R, CHRISTIE and KEOGH  ) it was used as a diagnostic criterion of prime importance. Tube test as described by CRUICKSHANK  was carried out to test the coagulase production.
All the organisms isolated were examined for antibiotic sensitivity by diffusion technique with filter paper disc (CRUICKSHANK  .) The following antibiotics were used: Penicillin G 1 unit, Streptomycin 10 micro-g., chloramphenicol 25 micro-g., tetracy-cline 10 micro-g., and erythromycin 10 micro-g per disc each.
The results of bacteriological culture examination are summarised in [Table 1]. Staphylococcus albus was isolated in 53% of the cases. The other organisms isolated were: Staphylococcus aureus (14.7%) diphtheroids (11.7%) pseudomonas (5.8%), organisms of E. Coli group (1.9%), alpha-haemolytic and non-haemolytic streptococci (6.8%), gram positive spore bearing aerobic bacilli (4.9%) and Klebsiella penmonice (1.9%).
Antibiotic sensitivity pattern of staphylococci is given in [Table 2]. The sensitivity pattern of these organisms is being reported not only because they constitute the bulk of the organisms isolated in this series but also because these organisms develop resistance to various antibiotics rapidly.
The susceptibility of conjunctiva to various infectious agents differs from that of the nasal mucous membrance. The most frequent offenders are the pneumococcus, diplobacillus of Morax-Axenfeld, Influenza bacillus, Koch-Weeks bacillus, streptococcus, gonococcus, and pathogenic staphylococcus. It is known that pathogenic staphylococci may grow in the mucous film on conjunctival surface without causing disease. Streptococci, diplobacilli and coliform organisms may, occasionaly, grow in a similar fashion as normal flora (HOGAN and ZIMMERMAN.  ) But the most frequent saprophytic organism in the conjunctiva is staphylococcus albus.
The present observation is in agreement with the reports of other workers that Staphylococcus albus is the most commonly isolated organism from normal conjunctiva. Staphylococcus aureus, the potentially pathogenic organism, was isolated from 14.7% of apparently normal conjunctivae in the present study. This is linked with the larger problem of colonisation of different parts of the body by Staphylococcus aureus. There are but few locations from where staphylococci have not been isolated. Several workers (HALLMAN,  McFARLAN,  GILLESPIE et al,  ROUNTREE and BARBOUR,  ) have shown that they are present in the anterior nares of a high proportion of normal persons and that 30-60% of persons are nasal carriers of potentially pathogenic staphylococci. Relatively harmless members of albus species are commonly present on the skin, but the more dangerous aureus species is found on the hands of only a small proportion of healthy persons who are usually shown on investigation to be heavy nasal carriers (GILLESPIE et al,  and MILES, WILLIAMS AND CLAYTON-COOPER  ). In a study carried out by RAJVANSHI, SAHAI AND MEHROTRA  coagulase positive staphylococci were isolated from the anterior hares of 63.8% of the hospital staff, 58% of hospitalised patients, 32% of persons unassociated with hospitals and 55% of the infants delivered in hospital. Ubiquitous as staphylococci are, their natural habitat is the animal body, which serves as a reservoir of infection. Many of the strains isolated from the conjunctiva would have come from the anterior nares of these persons.
A variety of other gram negative and gram positive bacilli are capable of a saprophytic existence in the conjunctiva. Pseudomonas was isolated in 5.8% of the cases in the present series, which is a rather high incidence as compared to other reports. SOUDAKOFF  isolated Pseudomonas in 2.5% of their cases, while NICHOLAS AND GOOLDEN  reported 1.4% incidence of Pseudomonas in cases of conjunctivitis. Pseudomonas is widely distributed in nature being found in water and sewage, sometimes in the intestinal canal and on the normal skin. It has been found to be an important cause of infection in persons being treated with broad spectrum antibiotics, corticosteroids and antimetabolites (WILLIMS, WILLIAMS and HYAMS.  ) As the history of administration of broad spectrum antibiotics or corticosteroids was not ascertained in these cases and the number of cases studied ill the present series is small, no conclusions can he drawn. Further study comprising a larger m tuber of cases is necessary to establish the incidence of pseudomonas in normal conjunctiva.
The sensitivity tests indicate that staphylococcus albus strains were proportionately more sensitive than Staphylococcus aureus strains to all the antibiotics tested. Highest percentage of strains were found to be sensitive to erythromycin and chloramphenicol. MONNIER AND SCHOENBACH  and BARBER, CSILLAG AND MEDWAY have also reported a high percentage of staphylococcal strains to be sensitive to chloramphenicol.
The results of bacteriological culture from normal conjunctiva of 102 persons are reported. Staphylococcus albus (53%) was most commonly isolated organism followed by staphylococcus aureus (14.7%) and diphtheroids (11.7%). Peseudomonas was isolated from 6 cases (5.8%). Sensitivity tests indicated that Staphylococcus albus was more sensitive to antibiotics than Staphylococcus aureus. Large majority of staphylococcal strains were sensitive to chloramphenicol and erythromycin.
I am thankful to Prof. D. B. Chandra, M.S., F.R.C.S., Head of the Department of Ophthalmology for supplying material for the present study.
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|16||NEMA H., BAL A., NATH K. AND SHUKLA B.: Baterial Flora of Trachomatous Conjunctiva. Brit. J. Ophthal., 48, 690-691, (1964).|
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