Salmonella Paratyphi: Introduction, Identification Features, Keynotes, and Salmonella Footages

Introduction

Salmonella Paratyphi (serovar) belongs to Enterobacteriaceae and thus is a Gram-negative bacterium causing mild gastroenteritis to a life-threatening bloodstream infection. It causes paratyphoid fever and it is restricted to humans. Proper sanitation and hygiene may decrease its infection chance. Travelers must be cautious during traveling in endemic countries of this organism.

Biochemical Tests of Salmonella Paratyphi

Basic Features	Properties
1. Gram Staining	Gram-Negative Rods (GNRs)
2. Spore	Non-Sporing
3. Capsule	Negative
4. Motility	Positive
5. Pigment	Negative
6. Growth in potassium cyanide (KCN) medium	Negative
7. Catalase test	Positive
8. Oxidase test	Negative
9. Nitrate reduction test	Positive
10. MR (Methyl Red) test	Positive
11. VP (Voges- Proskauer) assay	Negative
12. OF (Oxidative-Fermentative) test	Fermentative/Facultative anaerobe
13. Gas	Positive
14. H2S production	Negative
15. Indole formation	Negative
16. Urease/ urea hydrolysis test	Negative
17. Citrate/ citrate utilization	Negative
18. DNase test	Negative
19. Glucose fermentation	Positive
20. Maltose fermentation	Positive
21. Lactose fermentation	Negative
22. Sucrose fermentation	Negative
23. Xylose fermentation	Positive
24. Mannitol fermentation	Positive
25. Acetate Utilization	Negative
26. ONPG (β-galactosidase)	Negative
27. Phenylalanine Deaminase (PDA)/PPA Test	Negative
28. Lipase test	Negative
29. Esculin Hydrolysis test	Negative
30. Lysine Decarboxylase Test	Positive
31. Ornithine Decarboxylase Test	Negative
32. Arginine Dihydrolase Test	Negative

Keynotes on Salmonella

• The mode of transmission of S. Typhi is the faeco-oral route.
• The infective dose of typhoid is 10 bacilli through ingestion.
• Most strains of Salmonella are motile except Salmonella gallinarum and S. pullorum.
• Antigens of Salmonella are o antigen (somatic),H antigen (flagellar), Vi antigen and K antigen (capsular antigens), F antigen (fimbrial), M antigen and R antigen (in S R mutation due to the loss of O antigens).
• S. Paratyphi causes paratyphoid.
• Salmonella Typhi differs from S. Paratyphi in TSI reactions on the basis of H₂S production (S. Typhi) and gas formation (S. Paratyphi).
• Some other Salmonella serovars are Salmonella Typhi, Salmonella Typhimurium and Salmonella Enteritidis.

Salmonella Footages

Turbidity of blood culture bottle having Trypton soya broth from blood specimen due to S. Paratyphi

Salmonella Paratyphi growth on Nutrient Agar

Salmonella Paratyphi growth on Blood Agar

S. Paratyphi growth on MacConkey Medium

Salmonella Paratyphi in Gram Stained smear of Culture Microscopy

Salmonella Typhi and Paratyphi Colony Morphology on XLD agar

Salmonella-Shigella (SS) Agar with Salmonella Paratyphi and Shigella flexneri Growth

S. Paratyphi Biochemical Tests in TSI, SIM, Citrate, and Urea Agar Expo

Salmonella Serovar Paratyphi growth on Nutrient agar, Blood agar, MacConkey medium, BHI broth, and Biochemical reactions in TSI, SIM, citrate, and urea agar

Further Readings

• Cowan and Steel’s, manual for the identification of medical bacteria
• Topley and Wilson’s microbiology and microbial infection Topley and Wilson’s microbiology and microbial infection – Bacteriology-2-10th Edn.
• Manual of Clinical Microbiology -Patrick R. Murray -8th Edn.
• Bailey and Scott’s Diagnostic Microbiology -13th Edn.
• Mackie & Mc Cartney Practical Medical Microbiology- 14th Edn.
• Diagnostic Microbiology -Connie R. Mahon & George Manuselis
• Koneman Color Atlas and Textbook of Diagnostic Microbiology-6th Edn.
• Jawetz Melnick and Adelberg’s Medical Microbiology- 25th Edn.
• Lippincott’s –Illustrated- review-Microbiology-3rd Edn.
• Mandell’s Infectious Disease-7th Edn.
• https://research.itg.be/en/projects/salmonella-paratyphi-a-the-emergence-of-a-neglected-pathogen-in-a
• Bergey’s Manual of Systemic Bacteriology – 2nd Edn.
• Text Book of Microbiology -Anantanarayan & Paniker-9th Edn.