Salmonella typhi.Salmonella.SlideShare.pptx.

Medical Bacteriology , Salmonella typhi, Salmonella

1. VIVEKANANDA ARTS AND SCIENCE COLLEGE FOR WOMEN Affiliated to Periyar University,salem ; recognised under section 2(f)&12(B) of the UGC act,1956 Veerachipalayam-637 303, Sankagiri , Salem Dt, Tamilnadu , India DEPARTMENT OF MICROBIOLOGY SUBJECT: MEDICAL BACTERIOLOGY TITLE: SALMONELLA TYPHI Submitted By: Ms.Swathi Natrajan , III B.Sc Microbiology, Department of Microbiology. Subject Incharge : Dr.R.Mythili Ravichandran , Head of the Department, Department of Microbiology.

2. CONTENTS Introduction Morphology Taxonomic ranks of Salmonella Culture Biochemical reaction Virulence factors Pathogenesis Laboratory diagnosis

3. Clinical manifestations Vaccines Treatment Prevention

4. INTRODUCTION Salmon and Smith in 1885 isolated for first time named after its discoverer Salmon salmonellae organism are survives in facultative anaerobic condition. It is a Gram negative bacilli and typically live in animal and human intestines and are shed through stool (feces). Salmonella is infected most frequently through the contaminated water or food. Some people with Salmonella infection have no symptoms. Salmonella strains are sometimes cause infection in urine, blood, bones, joints or the nervous system ( Spinal fluid & brain) and can cause severe disease. Salmonella typhi is the most important member of the genus Salmonella that causes typhoid fever.

5. This bacillus, subsequently designated as S.choleraesuis was the first of a series of similar bacteria to be isolated from animals as well as human beings, subsequently it was realised that the bacillus responsible for typhoid fever also belongs to this group with some biochemical differences and this organism. Salmonellae produce 2 main types of disease This disease in man but mixed forms are frequently observed are ; Enteric fever group Non- typhoidal salmonellosis group

6. Enteric fever group: Serotypes S.typhi and S.paratyphi A,B,C are exclusively or primarily restricted to human hosts in whom these organisms cause enteric fever. Non- typhoidal salmonellosis group: The remaining serotypes of salmonella [non typhoidal Salmonella,NTS ] are essentially animal parasites.

7. MORPHOLOGY Salmonellae is gram negative,motile,non-sporing,Non - capsulated bacilli, measuring approximately 1-3×0.5 micro metre . Most strains are motile due to presence of peritrichons flagella expecpt S.pullorum which are always non- motile. Non-motile mutants of other types of salmonella may sometimes be found. They do not produce capsules or spores but may have fimbriae. Taxonomic ranks of Salmonella: Domain – Bacteria Kingdom – Eubacteria

8. Phylum – Proteobacteria Class - Gamma Proteobacteria Order – Enterobacteriales Family – Enterobacteriaceae Genus – Salmonella Species – Salmonella bongori , Salmonella enterica Sub-species – In enterica species – enterica (I), salamae (II), arizonae ( IIIa ) ,diarizonae( IIIb ), hontenae (IV), indica (VI).

9. CULTURE Salmonellae is aerobe and facultatively anaerobic.Optimum temperature for growth is 37 o C ( Range 15 o -41 o C). pH= 4 to 8. They grow readily on simple culture media and in Mac conkey’s agar and DCA media over range of pH is 6 to 8 and produce large ,2 to 3mm in diameter, circular, transluscent,low convex, smooth and colourless colonies due to the absence of lactose fermentation. In blood agar: On blood agar medium, Salmonella species produce colourless colonies which are some what moist ,smooth , opaque and dull grey .

10. In Mac conkey agar & DCA : On Mac conkey agar &DCA , Salmonellae do not show any red pigmentation & colonies are colourless indicating the organism as a non-lactose fermenter . These media permit rapid detection of other organisms, such as proteus , serratia ,pseudomonas and etc.

11. BIOCHEMICAL REACTION The salmonellae do not ferment lactose or sucrose and do not produce indole or ferment gelatin.They ferment glucose, mannitol, maltose & dextrin with production of acid and gas except S.typhi which produces only acid and no gas .Most strains produce H 2 S in triple sugar iron agar . Utilise citrate and are MR positive.Urea is not hydrolyzed. The biochemical tests are helpful for distinguishing enteric salmonella – serotypes - S.typhi and S.paratyphi A,B,C from non- typhoidal Salmonella.

12. VIRULENCE FACTORS I . Principal factor Type III secretion system (bacterial proteins): Two separate type III secretion systems of bacterial proteins medicate the initial invasion of Salmonella into the mucosa of small intestine. II. Other factors: Endotoxin : Cell wall polysaccharide (O antigen). Invasions : Invasions are proteins that mediate adherence to and penetration of intestinal epithelial synthesis of these fimbrial proteins by the bacterial cell is under the control of invasion in vgenes .

13. Factors involved in resistance of acid pH : Salmonellae are protected from stomach acid and acid pH of the phagosome by acid tolerance response (ATR) gene of chromosome.
Vi (virulence) antigen: This surface antigen (Vi antigen) of S.typhi has antiphagocytic properties,its role as a virulent factor in not clear.

14. PATHOGENESIS Infection begins with ingestion of contaminated water or food.The infective dose is 10 3 -10 6 bacilli (colony forming units) . A)Incubation stage: After crossing the epithelial layer of the small intestine, S typhi and S.paratyphi , causing enteric fever are phagocytosed by macrophages. They survive in the antimicrobial environment of macrophage by means of type III secretion system (SPI -2). A transient bacteraemia follows , during which the bacilli colonise in reticuloendothelial tissues –liver, spleen, lymph nodes & bone marrow.

15. B)Septicemic stage: By about 10 th day , the parasitised cells undergo necrosis and the bacilli pass into blood leading to a secondary and heavier bacteraemia , which corresponds with the onset of clinical illness at about 14 th day after ingestion. C) Stage of localisation : From the blood stream organisms localise in lymphoid tissue and different organs. The principal lesions include hyperplasia and necrosis of lymphoid tissue.

16. LABORATORY DIAGNOSIS Bacteiological diagnosis of enteric fever consists of isolation of the bacilli from the patient and the stration of antibiotics in his or her serum. Specimen: Blood is collected for culture as in urine and stool.Serum is obtained for the Widal test.The choice of specimen depends on the duration of illness. Blood culture: A positive blood culture is diagnostic.Bacteremia occurs early in the disease and blood cultures are positive in the first week of fever .Blood culture is positive in approximately 75 % of cases in the second week. 60 percent in the third week and 25% thereafter till the subsidence of pyrexia . Blood cultures

17. Cultures rapidly become negative on treatment with antibiotics. Clot culture: An alternative to blood culture in clot culture,5 ml of blood is withdrawn from the patient into a sterile test tube and allowed to clot.The serum is pipetted off and used for the Widal test. The clot is broken up with a sterile glass rod and added to a bottle of bile broth. The corporation of streptokinase (100 units per ml) in the broth facilitates lysis of the clot. Clot cultures yield a higher rate of isolation than blood cultures as the bactericidal action of the serum is obviated.

18. Feces culture: Salmonellae are shed in feces throughout the course of the disease and even in convalescence, with varying frequency. Hence,fecal cultures are almost as valuable as blood cultures in diagnosis. A positive fecal culture , however may occur in carriers as well as in patients. Fecal samples are plated directly on Macconkey ,DCA or XLD and Wilson- Blavir media. Urine Culture : Salmonellae are shed in urine irregularly and infrequently. Cultures are generally positive only in the second and third weeks and then only in about 25% of cases. PCR based tests: These are also sensitive but not widely available.

19. CLINICAL MANIFESTATIONS SYMPTOMS Early symptoms: Fever Chills Headache Weakness and Fatigue Muscle aches Stomach pain Diarrhea / Constipation Rash

20. After Illness Stomach pain Swollen Stomach Infection caused by GUT Bacteria spread throughout the body,is called sepsis. In some cases people may have confused,Not able to pay attention to anything & Not able to react to the world.

21. VACCINES They are three types of vaccines are used they are, TAB vaccine Live oral vaccine Vi vaccine TAB vaccine: Specific prophylaxis with the heat killed typhoid bacillus vaccine was developed and successfully field tested by Almroth Wright during the boer war in South Africa. Live oral vaccine: The live oral vaccine ( Typhoral ) is stable mutant of S.typhi strain Type2 1a, lacking the enzyme UDP-galactose-4-epimerase ( Gal E mutant).

22. Vi vaccine: The injectable vaccine ( typhim -Vi) contains purified Vi polysaccharide antigen (25 micro gram per dose) from S.typhi strain Type2. TREATMENT : Ampicillin, Amoxycillin and Cotrimoxazole were the other drugs found useful in the treatment to typhoid fever but current strains show resistance to these also. At present,Ciprofloxacin is the drug of choice or in case of resistance, Ceftriaxone is given.

23. PREVENTION Wash your hands.
Keep your food preparation areas clean.
Avoid unpasteurized foods.
Cook and store your food at the appropriate temperatures.
Be careful when handling animals.
Use caution when swimming.
Do you suspect that you have a foodborne or waterborne illness.

24. REFERENCE A Textbook of Microbiology P Chakraborty,1995. https://images.app.goo.gl/mXR53mBoZ8w6Ubu78 . https://images.app.goo.gl/Ly8r1vBzr1JbLwBw5 . https://images.app.goo.gl/Dc9XW9Cm4YurD4xs6 https://images.app.goo.gl/nEhQQdm1Ey3pVkoX6 , etc ,.

25. Thank you !