The eye harbours bacteria from the time of birth throughout life. Owing to its antibacterial properties, the normal conjunctival flora plays a significant role in the defence against superficia

Lm V. K. E

Mohinder Singh

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Med. J. Malaysia Vol. 42 No. 1 March 1987
BACTERIOLOGY OF
HEALTHY CONJUNCTIVAE
IN MALAYSIANS
MOHINDER SINGH
L1M V.K.E.
INTRODUCTION
The eye harbours bacteria from the time of
birth throughout life. Owing to its antibacterial
properties, the normal conjunctival flora plays a
significant role in the defence against superficial
ocular infections. In view of its protective action
as well as its probable role in causing ocular disease
under certain circumstances, the study of the
normal flora and its pattern of antibiotic suscep-
tibility could provide useful information in the
prevention and treatment of post-surgical
infections. While several such surveys have been
reported from various parts of the world, no data
is available for the Malaysian population.
This survey seeks to establish the pattern of
bacterial flora in healthy conjunctivae of Malay-
sians. In addition, the bacterial flora of a non-
diabetic population was compared to that of a
diabetic population to see if there were any
differences.
MATERIALS AND METHODS
Conjunctival swabs were obtained from 200
non-diabetic and 50 diabetic subjects attending
the Ophthalmological and Diabetic clinics of the
Mohinder Singh, MBBS. novs. MS, FRCS
Department of Ophthalmology
Um V.K.E., MBBS, MSc, MRCPath
Department of Microbiology
Faculty of Medicine
Universiti Kebangsaan Malaysia
Jalan Raja Muda, 50300 Kuala Lumpur
Correspondence Address:
Or Mohinder Singh
37 Norman Road
Ilford, Essex 1G1 2NH, England
50
Universiti Kebangsaan Malaysia. None of the
subjects had evidence of ocular infections nor had
they used any eye medication during the previous
two months.
Cotton swabs moistened with sterile normal
saline were used. It was passed back and forth
twice over the greater part of the lower conjunc-
tiva. Care was taken not to touch the eyel id or
eyelashes. The swab was then inoculated onto
two blood agar, one chocolate agar and one
MacConkey agar plates. A fresh swab was used
for the other eye.
All inoculated plates were sent to the Baterio-
logy laboratory for incubation and further process-
ing. One blood agar and the MacConkey plate were
incubated aerobically while the chocolate plate
was incubated in a candle jar. The other blood agar
plate was incubated anaerobically using the
GasPak disposable anaerobic system (BBL). The
incubation temperature was 370C. The plates
were read after 48 hours and again after a further
72 hours of incubation. All isolates were identified
in the usual manner. Antibiotic susceptibility was
determined using a standardised disk test.'
RESULTS
Table I shows the age and sex distribution of
the subjects.
Among the 200 non-diabetic subjects, no
bacteria was isolated from 139 (69.5%). Of the
remaining 61 subjects, bacteria was isolated
from one eye in 26 and from both eyes in 35.
Of the 96 positive cultures, 69 were pure growths
and 27 mixed growths.
The types of organisms isolated are summarised
in Table 11. Staphylococcus epidermidis was theTABLE I
AGE AND SEX DISTRIBUTION OF SUBJECTS
Normal Diabetic
Age group Male Female Male Female
(yrs)
10 - 20 8 ( 3) 9 ( 0) o( 0) 1 ( 1)
21 - 30 59 (19) 47 ( 7) 1 ( 1) 2 ( 1)
31 - 40 19 (12) 28 (11) 4 ( 2) 2 ( 0)
41 - 50 5 ( 2) 6 ( 3) .9 ( 6) 8 ( 4)
51 - 60 6 ( 4) 8 ( 0) 10 ( 6) 5 ( 3)
61 -70 3 ( 0) 2 ( 0) 4 ( 4) 4 ( 3)
Total 100 (40) 100 (21) 28 (19) 22 (12)
Number of positive cultures in parenthesis.
TABLE 11
TYPES OF ORGANISMS ISOLATED FROM
HEAL THY CONJUNCTIVAE
Organism Non-diabetic Diabetic Total (%)
S. epidermidis 59 40 99 (52.6 )
Corynebacterium sp, 43 18 61 (32.4
S. aureus 7 4 11 ( 5.9
Acinetobectersp. 5 2 7 ( 3.7
Propionibacterium sp, 3 0 3 ( 1.6
Others* 7 0 7 ( 3.7
Total 124 64 188 (100.0)
*Others - Strep sp, 3; Micrococcus sp, 2 yeasts 2.
most common bacterial isolate (52.6%), followed
by Corynebacterium sp, (32%),and Staphylococcus
aureus (5.9%). There were five cultures of Acine-
tobacter sp which was the only gram-negative
bacillus isolated. Yeasts were isolated from both
eyes in one patient and there were three isolates
of anaerobic bacteria which were all Propioni-
bacterium sp.
Among the diabetic subjects, growth was
obtained in 31 (62%). The organisms isolated are
also summarised in Table 11. Again S. epidermidis
was the most common, followed by Coryne-
bacterium sp.and S. aureus.
51
A significant proportion of S. epidermidis
(48.5%) were resistant to penicillin. Resistance to
tetracycline was also common. The majority of
S. epidermidis, however, remained sensitive to
chloramphenicol and gentamicin. Resistance to
these antibiotics among the Corynebacterium
sp. was not common. All staphylococcal isolates
were found to be sensitive to methicillin. All
isolates in this survey were sensitive to gentamicin.
DISCUSSION
Infections of the outer eye have been attributed
to agents such as bacteria, viruses and rickettsia.
In a large survey involving 10,271 individuals
between 1952 - 1968, Locatcher-Khorazo and
Gutierres found S. epidermidis, S. aureus and
diphtheroids to be the most commonly isolated
organisms from the normal conjunctival sac.
They did not find any significant variation with
regards to sex, age and season.? Similar studies
from around the world including China and Japan'
as well as the present survey confirm these findings.
We were disappointed in the low rate of isola-
tion of anaerobes in this survey. Although Locat-
cher-Khorazo and Gutierres did not isolate any
anaerobes, more recent studies have shown that
anaerobes, in particular Propionibacterium sp, are
common in the conjunctival flora. 3,4 We feel that
the apparent absence of anaerobes in our survey
is due to technical deficiencies rather than a true
low prevalence.
Diabetic subjects when compared to non-
diabetics had more positive cultures. Between
3-40% of normal subjects showed an absence of
growth, and this apparent absence may be due to
the fact that bacterial counts are low in normal
conjunctivae and the variation in the figures is
a reflection of the different sensitivities of isola-
tion procedures. Although the number in the
diabetic group is too small for any generalisation,
the findings of more positive cultures in our
diabetic subjects seem to suggest that the con-
junctival bacterial population in diabetics may be
higher than that of nondiabetics. Further studies
are required to confirm this. Certain immune
mechanisms have been found to be deficient indiabetics'' and it would be interesting to find
out if this deficiency has resulted in their apparent
failure to limit the numbers of bacteria in their
conjunctivae.
Surgical intervention in the diabetic eye has
become more frequent in recent years and longer
operative procedures are considered to be asso-
ciated with increased risk of post-surgical infec-
tions. A higher incidence of positive cultures in
our healthy diabetics' eyes thus appear quite
relevant in this respect.
Penicillin, tetracycline, chloramphenicol and
gentamicin are common topical agents used by
ophthalmologists in Malaysia, but resistance to
penicillin and tetracycline among conjunctival
flora appears to be fairly common. Hence for
empirical therapy, we would suggest chloramphe-
nicol or gentamicin.
ACKNOWLEDGEMENTS
The authors are grateful to Assoc. Prof. Abdul
Khalid Kadir for allowing us to study patients
from the Diabetic clinic. We are thankful to the
52
technologists, in particular Cik Halljah Mohd
Yunus, for their laboratory assistance; Puan
Rohana Ariffin and Cik Zabedah Kassim for their
secretarial work.
This study was funded by Universiti Kebang-
saan Malaysia Research Grant No: 22/84,
REFERENCES
1 Garrod L P, Lambert H P, O'Grady F. Antibiotic and
chemotherepy (5th Edition), Edinburgh: Churchill
Livingstone, 1981 : 464-503.
2 Locatcher-Khorazo D, and Gutierrez E. The bacterial
flora of the normal eye. In Locatcher-Khorazo D, See-
gal BC (sds). Mtcrobiotoqy of the Eve. St Louis: C.V.
Mosby Co, 1972: 13 - 23.
J Perkins R E, Kundsin R B, Pratt M V, Abrahmsen I,
Leibowitz H M. Bacteriology of the normal and infec-
ted conjunctivae. J Clin Microbio/1975; 1 : 147-149.
4 McNatt J, Alien S D, Wilson LA, Dowell V R Jr. Anae-
robic flora of the normal human conjunctival sac. Arch
Ophthalmol 1978; 96 : 1448 - 1450.
Thornton G P. Infection and diabetes. Medical Clinics
ofNorth America 1971; 55 : 931 - 938.

BACTERIOLOGY OF HEALTHY CONJUNCTIVAE IN MALAYSIANS

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