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Table of Contents
About Salmonella Typhi
- Salmonella enterica subspecies enterica serovar Typhi (Salmonella typhi) causes typhoid fever in humans.
- Typhoid fever is a systemic illness that causes fever. It is spread through faeces and food or water, mostly in the developing world.
- At least 16–20 million people get typhoid fever each year around the world, and about 600,000 of them die.
- S. typhi is different from the other 2300 serovars of S. enterica subs. enterica because it is only able to infect people.
- Given that S. typhi is so specific to humans, it could be younger than the split between humans and higher primates a few million years ago. It could also be younger than the spread of anatomically modern humans from Africa about 50,000 to 100,000 years ago.
- S. enterica and Escherichia coli had their last common ancestor about 140 million years ago, but no one knows how old S. typhi is yet.
- By using pulsed-field gel electrophoresis, IS200 typing, ribotyping, and amplified fragment length polymorphism, it has been shown that the S. typhi population has a lot of genetic diversity.
- All of these fingerprinting methods found different fingerprints that were thought to be from different clones. This suggests that S. typhi is quite diverse.
- There have been cases of typhoid outbreaks caused by a single PFGE genotype, but sporadic disease in endemic areas is usually linked to more than one PFGE genotype.
- S. typhi isolates can have genome sizes that are up to 20% (1 MB) different from each other. This suggests that there has been a long history of insertions, deletions, and/or horizontal genetic exchange.
- Also, unlike other serovars of S. enterica, the order of genes in S. typhi is not fixed. This is because homologous recombination between rRNA genes can cause rearrangements.
Biochemical Test of Salmonella Typhi
| Biochemical Tests | Results |
|---|---|
| Capsule Test: | Negative (-ve) |
| Catalase Test: | Positive (+ve) |
| Citrate Test: | Negative (-ve) |
| Flagella Test: | Positive (+ve) |
| Gas Test: | Negative (-ve) |
| Gelatin Hydrolysis Test: | Negative (-ve) |
| Gram Staining Test: | Negative (-ve) |
| Growth in KCN Test: | Negative (-ve) |
| H2S Test: | Positive (+ve) |
| Indole Test: | Negative (-ve) |
| Motility Test: | Motile |
| MR (Methyl Red) Test: | Positive (+ve) |
| MUG Test | Negative (-ve) |
| Nitrate Reduction Test: | Positive (+ve) |
| Oxidase Test: | Negative (-ve) |
| Pigment Test: | Negative (-ve) |
| Shape | Rod |
| Spore Test: | Negative (-ve) |
| TSIA (Triple Sugar Iron Agar) Test: | Alkali/Acid |
| Urease Test: | Negative (-ve) |
| VP (Voges Proskauer) Test: | Negative (-ve) |
| Adonitol Test: | Negative (-ve) |
| Arabinose Test: | Negative (-ve) |
| Arabitol Test: | Negative (-ve) |
| Cellobiose Test: | Negative (-ve) |
| DNase Test: | Negative (-ve) |
| Dulcitol Test: | Negative (-ve) |
| Erythritol Test: | Negative (-ve) |
| Esculin Hydrolysis Test: | Negative (-ve) |
| Glucose Test: | Positive (+ve) |
| Glycerol Test: | Negative (-ve) |
| Inositol Test: | Negative (-ve) |
| Lactose Test: | Negative (-ve) |
| Malonate Test: | Negative (-ve) |
| Maltose Test: | Positive (+ve) |
| Mannitol Test: | Positive (+ve) |
| Mannose Test: | Positive (+ve) |
| Melibiose Test: | Positive (+ve) |
| Mucate Test: | Negative (-ve) |
| MyoInositol Test: | Negative (-ve) |
| Raffinose Test: | Negative (-ve) |
| Rhamnose Test: | Negative (-ve) |
| Salicin Test: | Negative (-ve) |
| Sorbitol Test: | Positive (+ve) |
| Sucrose Test: | Negative (-ve) |
| Tartrate Test: | Positive (+ve) |
| Trehalose Test: | Positive (+ve) |
| Xylose Test: | Positive (+ve) |
| Acetate Utilization Test: | Negative (-ve) |
| Arginine Dehydrolase Test: | Negative (-ve) |
| Esculin Hydrolysis Test: | Negative (-ve) |
| Lipase Test: | Negative (-ve) |
| Lysine Test: | Positive (+ve) |
| ONPG (β-galactosidase) Test: | Negative (-ve) |
| Ornithine Decarboxylase Test: | Negative (-ve) |
| Peroxidase Test: | Negative (-ve) |
| Tyrosine Hydrolysis Test: | Negative (-ve) |
References
- Kidgell, Claire & Reichard, Ulrike & Wain, John & Linz, Bodo & Torpdahl, Mia & Dougan, Gordon & Achtman, Mark. (2002). Salmonella Typhi, the causative agent of typhoid fever, is approximately 50,000 years old.. Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases. 2. 39-45. 10.1016/S1567-1348(02)00089-8.
- https://universe84a.com/common-bacteria-biochemical-test-demonstration/
- https://journals.plos.org/plosone/article/figure?id=10.1371/journal.pone.0194817.t001
- https://www.slideshare.net/doctorrao/biochemical-tests-in-enterobacteriaceae
- https://www.researchgate.net/figure/Biochemical-tests-of-Salmonella-typhi-isolates_tbl1_344470665
- https://microbiologyinfo.com/biochemical-test-and-identification-of-salmonella-typhi/
- https://microbenotes.com/biochemical-test-of-salmonella-typhi/
