|Year : 1987 | Volume
| Issue : 1 | Page : 14-7
Detection of Salmonella typhi 'O' antigen by counter-immuno-electrophoresis.
PJ Vadher, DU Antani, SA Kamat
P J Vadher
|How to cite this article:|
Vadher P J, Antani D U, Kamat S A. Detection of Salmonella typhi 'O' antigen by counter-immuno-electrophoresis. J Postgrad Med 1987;33:14-7
|How to cite this URL:|
Vadher P J, Antani D U, Kamat S A. Detection of Salmonella typhi 'O' antigen by counter-immuno-electrophoresis. J Postgrad Med [serial online] 1987 [cited 2020 Jun 6 ];33:14-7
Available from: http://www.jpgmonline.com/text.asp?1987/33/1/14/5313
The diagnosis of enteric fever has been traditionally based either on demonstration of Salmonella organisms in the patient's body (blood, stool, urine) or by demonstration of a rising titre of specific antibodies by Widal test. Since the advent of Counter immunoelectrophoresis (CIEP), its application in the laboratory for demonstration of microbial antigens is on the increase. This study evaluates the usefulness of CIEP in the detection of Salmonella 'O' antigen in the sera of patients suffering from enteric fever.
MATERIAL AND METHODS
In the initial pilot study, 130 patients of suspected enteric fever were studied by clot culture and CIEP for Salmonella 'O' antigen. After the pilot study, another 250 patients suspected to be suffering from enteric fever and admitted in Kasturba Hospital for Infectious Diseases were included in the study from June 1982 to May 1983. Blood culture, clot culture and CIEP for Salmonella antigen were done on the day of admission. Blood for culture was collected in tryptic soya broth with liquoid and clot culture was done in bile broth. Blood and clot cultures were followed up for one week and the resultant growth was identified by standard methods. CIEP for Salmonella 'O' antigen was done using antiserum raised in rabbits by repeated intramuscular injection of Salmonella 'O' antigen extract. CIEP was done using agarose gel and standard electrophoretic apparatus and buffer as suggested by Kelkar and Niphadkar. The samples showing the characteristic precipitin lines were interpreted as positive. Positive and negative controls for both antigen and antibody were run simultaneously in each test. The results were read, in a dark ground viewing box.
[Table 1] shows the results of the initial pilot study. Sixty five patients (50%) gave positive culture for S. typhi or S. paratyphi 'A' All these patients' sera also showed Salmonella 'O' antigen by CIEP. One patient's clot culture was negative but had Salmonella 'O' antigen in his serum.
[Table 2] shows the comparative results of blood culture, clot culture and CIEP for Salmonella 'O' antigen in 250 patients under study. S. typhi was isolated from clot culture in 72 cases (28.8%) and from blood culture in 59 cases (23.6%). S. paratyphi 'A' was isolated from clot culture in 10 cases (4%) and from blood culture in 8 cases (3.2%). Antigen detection by CIEP was positive in 68 patients (27.2%) whose clot culture showed S. typhi. All ten patients whose clot culture yielded S. paratyphi 'A' were also positive by CIEP. Three cases (1.2%) whose blood culture and clot culture yielded no growth showed the presence of Salmonella 'O' antigen in their serum by CIEP.
Gupta and Rao demonstrated Salmonella 'O' antigen in 24 of 26 patients of clinical enteric fever in the acute phase. Harish and Rao detected the antigen only in 56% of their blood culture positive patients. The above results show that clot culture gives better results than blood culture. Soman and Modi also showed that clot culture was superior to blood culture for growing Salmonella organisms. When the patients had septicaemia due to organisms like Gram positive cocci and Gram negative bacilli other than Salmonella, the CIEP was negative. This is significant in that no false positive results were obtained by CIEP. Four patients whose clot culture; was positive for S, typhi did not show 'O' antigen in their sera by CIEP. This could be due to a technical error. However, overall results suggest that the CIEP is as useful as clot culture if not better. (False positive tests are not likely to occur.) Moreover, CIEP is quite a simple procedure and can be done in any laboratory and gives quicker results. Results of blood culture and clot culture may be available 48 hours or later after collection of blood. CIEP, on the other hand, can give a result in about an hour or so. If clot culture and IEP are done simultaneously many patients of enteric fever can be diagnosed.
We acknowledge our gratefulness to the Dean, Topiwala National Medical College, Bombay, and Medical Superintendent, Kasturba Hospital for Infectious Diseases, Bombay, for the permission to publish this work.
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