A simple alternative method for rapid detection of slime produced by Staphylococcus epidermidis isolates in bacterial keratitis.
OBJECTIVE
Slime is a known virulence factor of Staphylococcus epidermidis. The conventional Christensen's method for detection of slime in the laboratory takes at least 48 h. We, therefore, tried to evaluate the efficacy of the Congo red agar method as a routine procedure for detecting slime among isolates from corneal ulcers.


METHODS
A total of 244 isolates from corneal ulcers were identified as S. epidermidis by the standard procedures. Slime was detected both by the conventional Christensen's method as well as by the Congo red agar method.


RESULTS
Ninety two (37.7%) isolates were positive and 86 (35.2%) were negative for slime by both the techniques. Fifty four (22.1%) isolates were positive in Congo red agar, but negative by Christensen's method; whereas only 12 (4.9%) were negative by Congo red but positive by Christensen's method. Detection of slime by Congo red agar method was rapid i.e., all the 146 strains were positive within 24 h of incubation. On the other hand, Christensen's method had a delayed response; 42.3 per cent (44/104) strains being negative during the first 24 h of incubation.


CONCLUSIONS
Our results suggested that culture on Congo red agar was a sensitive and rapid test for detecting slime. This might help in the quick identification in a routine laboratory of slime positive isolates in bacterial keratitis.
Nayak
N
N
Division of Microbiology, Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
Satpathy
G
G
Vajpayee
R B
RB
Pandey
R M
RM
D001431:Bacteriological Techniques; D003224:Congo Red; D003320:Corneal Ulcer / Q000382:microbiology*; D006801:Humans; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D013203:Staphylococcal Infections / Q000382:microbiology*; D013212:Staphylococcus epidermidis / Q000302:isolation & purification* / Q000378:metabolism / Q000472:pathogenicity; D014774:Virulence
D011135:Polysaccharides, Bacterial; D003224:Congo Red