1. LAGOS STATE UNIVERSITY, OJO
5th Conference of The Faculty of Science
10th – 14th October, 2017.

2. TITLE OF PAPER PRESENTATION
SODIUM BISELENITE INHIBITED SALMONELLA GROWTH ON DEOXYCHOLATE CITRATE AGAR
Presenter: AMISU, Kehinde Olugbenga
Date: 12TH October, 2017.

3. Outline Of Presentation:
Introduction
Morphologic and biochemical characteristics of Salmonella
Epidemiology of Salmonella infection
Laboratory diagnosis
Selectivity of DCA and Sodium biselenite
Research problems
Aim of the Study
Materials and Methods
Results
Discussion and Conclusion
List Of References

4. MORPHOLOGICAL AND BIOCHEMICAL CHARACTERIISTCS OF SALMONELLA
Gram negative, rod shaped, peritrichous and motile
bacterium
Non-fastidious, facultative anaerobe, non-lactose fermenter
Reduces sulfur to H2S
Source: Kemal (2014)

5. EPIDEMIOLOGY OF SALMONELLA
An enteropathogenic bacterium of humans and animals
Found and shed in faeces of infected humans and animals
Transmitted through contaminated foods and water sources causes gastroenteritis and enteric fever
A major health problem, especially in developing countries
Source: Freitas et al., 2010; Kemal, 2014

6. LABORATORY DIAGNOSIS
An enteropathogenic bacterium of humans and animals
Found and shed in faeces of infected humans and animals
Transmitted through contaminated foods and water sources causes gastroenteritis and enteric fever
A major health problem, especially in developing countries
Source: Freitas et al., 2010; Kemal, 2014

7. SELECTIVITY AND SENSITIVITY OF DCA AND SODIUM BISELENITE
SB highly inhibitory to coliforms
SB (4g/l) is used for selective enrichment of Salmonella in foods, faeces and sewage
DCA, a differentia and selective medium
DCA is inhibitory to intestinal Gram positive bacteria
DCA, supports the growth of enteric Gram negative bacteria Salmonella grows and produces colonies with distinct black center
DCA is used for both direct and indirect detection of Salmonella
SOURCE: Leifson, 1935, Baker et al., 2010

8. RESEARCH PROBLEMS
Abundance of competitive faecal bacteria flora is a serious challenge to direct plating technique
Salmonella yields from direct plating is generally low in comparison to indirect methods
Indirect plating is both time consuming and costly
inhibition of more competitive faecal flora on direct plating with increased inocula size and should improve recovery rates of Salmonella

9. AIM OF THE STUDY
To determine the growth selective performance of DCA supplemented with SB for detection of Salmonella

10. MATERIALS AND METHODS
Concentrated SB solution prepared and added to molten DCA forming DCASB
About 1g from each of 10 poultry droppings were suspended in 9.8ml normal saline
0.2 ml of actively growing Salmonella strains (1.5x107 cfu/ml), SAL 1 to 5 added to faecal suspensions
0.1ml of faecal inoculated onto DCASB and control DCA by spread plating technique
Plates were incubated at 37oC for 18-24hr
Culture plates were compared for bacterial growth and recovery rates of Salmonella

11. RESULTS
Addition of SB to molten DCA changed colour of medium (DCASB) to reddish brown
No faecal bacterial growth was observed on DCASB, even with extended incubation
Control plates yielded good and confluent bacterial growths
Bacterial yield on control plates include coliforms, Salmonella, Proteus and Pseudomonas

12. DISCUSSION
Laboratory diagnostic protocols play an important role in the management of infectious diseases
Attempt to modify DCA with addition of SB for improved recovery of Salmonella did not support any bacterial growth, including salmonella
Gross inhibition of feacal bacterial growth on DCASB suggests presence of highly toxic product formed from the interaction of SB with DCA components

13. DISCUSSION (CONTINUES)
Suspicions for formation of potent antibacterial product(s) is further supported by the spontaneous colour change of DCASB
It may be interesting to identify the unknown broad spectrum antibacterial agent
The unknown active agent may be useful for microbial control, if consider safe for use

14. CONCLUSION
The addition of SB to DCA is highly inhibitory to faecal bacteria, including Salmonella and
SB-DCA combination should not be used except where gross inhibition of bacterial growths is desired.

15. LIST OF REFERENCES
Baker, S., Favorov, M., and Dougan, G. (2010). Searching for the elusive typhoid diagnostic. BMC Infectious Diseases, 10:45.
Freitas, C. G. d., Santana, A. P., Silva, P. H. C. d., Goncalves, V. S. P., Barros, M. F., Torres, F. A. G., Murata, L. S. and Perecmanis, S. (2010). PCR multiplex for detection of Salmonella enteritidis, typhi and typhimurium and occurrence in poultry meat. International Journal of Food Microbiology. 39:

16. LIST OF REFERENCES (Cont)
Leifson, E. (1935). Formulation and composition of deoxycholate citrate medium. Journal of Pathological Bacteriology, 40: 581
Leifson, E. (1936). New selenite enrichment media for the isolation of typhoid and paratyphoid (Salmonella) bacilli. A. J. Hyg. 24:
Kemal J (2014) A Review on the Public Health Importance of Bovine Salmonellosis. J Veterinar Sci Technol, 5:175

17. LIST OF REFERENCES (Cont.)
North, W.R. (1950). A modified selenite enrichment broth for the detection of Salmonella. Bacteriological Proceedings, 50th General Meeting, pg. 67.
Willey, J., Sherwood, L. and Wolverton, C. (2013). Prescott s Microbiology. 9th Edition, McGraw- Hill, New York. ISBN-13:

18. Thanks for listening