classification, disease- symptoms, conditions, diagnosis, treatment, prevention.

1. SALMONELLA
A llwy n Vy a s G.

2. SALMONELLA - CLASSIFICATION
o Kingdom: Bacteria
o Phylum: Proteobacteria
o Class: Gamma Proteobacteria
o Order: Enterobacteriales
o Family: Enterobacteriaceae
o Genus: Salmonella
o Species: S. enterica, S. bongori

3. SALMONELLA - CLASSIFICATION
o The genus Salmonella is divided into two species:
 Salmonella enterica.
 Salmonella bongori.
o S. enterica is further divided into six subspecies that can be
abbreviated by Roman numerals, I, II, IIIa, IIIb, IV & VI.

4. SALMONELLA - CLASSIFICATION
o Salmonella enterica spp. is subdivided into 6 subspecies:
 enterica (I) [99% of Salmonella isolated from humans]
 salamae (II)
 arizonae (IIIa)
 diarizonae (IIIb)
 houtenae (IV) and
 indica (VI)

5. SALMONELLA - CLASSIFICATION
o SEROVARS / SEROTYPES
• A serotype or serovar is a distinct variation within
a species of bacteria or virus or among immune cells of
different individuals.
• These microorganisms, viruses, or cells are classified
together based on their cell surface antigens, allowing the
epidemiologic classification of organisms to the sub-species
level.
• The Salmonella has been determined to have over 2600
serotypes.

6. SALMONELLA - CLASSIFICATION
o S.enterica subsp enterica is further divided into several
serotypes or serovars based on biotypes (Antigenic
structures)
o For e.g.
• S. enterica subsp enterica ser. Typhimuruim
• S. enterica subsp enterica ser. Paratyphi
• S. enterica subsp enterica ser. Typhi

7. Morphology & Characteristics
Gram Negative.
Flagellated. (Except S. gallinarum & S. pullorum)
Non Spore Formers.
Facultative Anaerobic Bacilli.
May possess Fimbriae.
Chemoorganotrophic.

8. Salmonella with a peritrichous arrangement of flagella

9. S. enterica subsp enterica ser. Typhi under Scanning Electron Microscope

10. Salmonella (Gram stain) Gram negative rods

11. ANTIGENIC STRUCTURE
The genus Salmonella has three kinds of major
antigens with diagnostic or identifying applications:
Somatic, surface, and flagellar.
• Somatic (O) or Cell Wall Antigens.
• Flagellar (H) Antigens.
• Surface (Vi) Antigens. ( Found in some spp.)

12. ANTIGENIC STRUCTURE
o Somatic (O) or Cell Wall Antigens.
• Occurs on the surface of the outer membrane and are
determined by the specific sugar sequences on the cell
surfaces.
• Integral part of the cell wall [LPS complex].
• Heat stable- resistant to boiling up to 2hrs ; 30 mins.
• Resistant to 96% alcohol at 37oC; 4 hrs.
• Generally O- antigen is less antigenic than H- antigen.
• Mosaic of two or more antigenic factors.

13. ANTIGENIC STRUCTURE
o Flagellar (H) Antigens
• Present on flagella, Heat and alcohol labile.
• H- antigen of salmonella are genus specific and are not
share with other enterobacteria.
• Strongly immunogenic and associated with the formation of
antibodies following infections and immunization.

14. ANTIGENIC STRUCTURE
o Surface (Vi) Antigens
• Many strains of S. typhi fail to agglutinate with O
antiserum when isolated freshly; due to the presence of
Surface polysaccharide antigen enveloping O antigen.
• Heat labile, tends to be lost on serial sub- culturing.
• Act as a virulence factor inhibiting phagocytosis & resisting
complement activation and bacterial lysis by the alternate
pathway and peroxidase mediate killing.

15. PATHOGENICITY
o Salmonella are strict parasites of Humans as well as animals.
o S. typhi, S. paratyphi A, S. paratyphi B are confined to
humans.
o Some species are host adapted
• For e.g.
 S. abortus-equi found only in horses.
 S. abortus- ovis only in sheeps.
 S. gallinarum in poultry.
o S. typhimuruim have a wide range of hosts affecting animals
humans and birds.

16. ENTERIC FEVER [TYPHOID]
o CAUSATIVE ORGANISMS
• S. enterica subsp enterica ser. Paratyphi – Paratyphoid.
• S. enterica subsp enterica ser. Typhi – Typhoid.
o PATHOGENESIS
• Acquired by ingestion, reaching the gut.
• Attaches to microvilli of the ileal mucosa and penetrate to the
lamina propria and submucosa. Phagocytized by polymorphs and
macrophages.
• Multiplication in Mesenteric lymph nodes to Blood streams via
thoracic duct – bacteremia.

17. ENTERIC FEVER [TYPHOID]
• Bacilli spread to Liver, Gall bladder, spleen, bone marrow,
lymph nodes, lungs and kidney - Further multiplication.
• Multiplies abundantly in gall bladder- continuously
discharged into intestine.
• Attacks Peyer’s patches and lymphoid follicles of ileum-
Necrosis [Typhoid Ulcers].
• Typhoid ulcers leads to complications such as intestinal
perforation and hemorrhage.
• Offset is during 3-4 weeks normally- the intestinal lesions
undergo healing.

18. Typhoid Perforation

19. ENTERIC FEVER [TYPHOID]
o SYMPTOMS
• Fever that starts low and increases daily, possibly reaching
as high as 104.9 F (40.5 C)
• Headache
• Weakness and fatigue
• Muscle aches
• Sweating
• Dry cough
• Loss of appetite and weight loss
• Abdominal pain
• Diarrhea or constipation
• Rash
• Extremely swollen abdomen

20. ENTERIC FEVER [TYPHOID]
Later illness
[If you don't receive treatment, you may]:
• Become delirious.
• Lie motionless and exhausted with your eyes half-closed in
what's known as the typhoid state.
• In addition, life-threatening complications often develop at this
time.
• In some people, signs and symptoms may return up to two
weeks after the fever has subsided.

21. ENTERIC FEVER [TYPHOID]
o CONTAMINATION & TRANSMISSION
• Humans are the only natural source and reservoirs.
• The infection is transmitted by ingestion of food or water
contaminated with feces.
• Shellfish taken from contaminated water, and raw fruit and
vegetables fertilized with sewage.
• Flies may cause human infection through transfer of the
infectious agents to foods.

22. ENTERIC FEVER [TYPHOID]
o TYPHOID CARRIER STATE
Beside the problem of disease process, and important aspect of
typhoid is the prevalence of carrier in treated patients of
typhoid.
• TYPES OF CARRIERS
 Convalescent Carriers.
 Chronic Carriers.
 Temporary Carriers.

23. ENTERIC FEVER [TYPHOID]
o TYPES OF CARRIERS
• Convalescent Carriers.
These are the people continue to excrete bacilli for 3 weeks to
3 months after clinical cure.
• Chronic Carriers.
These are people continue to shed bacilli for over a year after
clinical cure.
• Temporary Carriers.
These are people shed bacilli for more than 3 months but less
than a year after clinical cure.

24. ENTERIC FEVER [TYPHOID]MARY MALLON – TYPHOID MARY
Mary Mallon (September 23, 1869 – November 11, 1938),
better known as Typhoid Mary, was the first person in the
United States identified as an asymptomatic carrier of the
pathogen associated with typhoid fever. She was presumed to
have infected 51 people, three of whom died, over the course of
her career as a cook. She was twice forcibly isolated by public
health authorities and died after a total of nearly three decades in
isolation.

25. MARY MALON (TYPHOID MARY) First time on isolation bed

26. ENTERIC FEVER [TYPHOID]
o EPIDEMIOLOGY
• Typhoid fever occurs worldwide, primarily in developing
nations.
• South-central Asia, Southeast Asia, and southern Africa are
regions with high incidence of S. typhi infection (more than
100 cases per 100,000 person years).
• Approx. 200 to 300 cases of S. typhi are reported in the
United States each year.
• In 2000, typhoid fever caused an estimated 21.7 million
illnesses and 217,000 deaths, and paratyphoid fever caused
an estimated 5.4 million illnesses worldwide.

27. ENTERIC FEVER [TYPHOID]
• Outbreaks of typhoid fever are frequently reported from
sub-Saharan Africa, often with large numbers of patients
presenting with intestinal perforations.
• S. Paratyphi A was responsible for a growing proportion of
enteric fever in a number of Asian countries, sometimes
accounting for 50% of Salmonella bloodstream isolates
among patients with enteric fever.

28. Global distribution of Typhoid Fever (2012)

29. ENTERIC FEVER [TYPHOID]
o DIAGNOSIS
• The definitive diagnosis of typhoid fever depends on the isolation of
S. typhi from blood, bone marrow or a specific anatomical lesion.
• The WIDAL test was the mainstay of typhoid fever diagnosis for
decades.
• Ox bile medium (Ox gall) is recommended for enteric fever
pathogens(S. typhi and S. paratyphi), only these pathogens can be
grown on it.
• More than 80% of patients with typhoid fever have the causative
organism in their blood.
• ELISA urine test to look for the causative organism.

30. ENTERIC FEVER [TYPHOID]
o TREATMENT
• Antibiotics- Ampicillin, chloramphenicol, trimethoprim
sulfamethoxazole, amoxicillin, and ciprofloxacin, have been
commonly used to treat typhoid fever in microbiology
• Where resistance is uncommon, the treatment of choice is
a fluoroquinolone such as ciprofloxacin. Otherwise, a third-
generation cephalosporin such as ceftriaxone or
cefotaxime is the first choice.
• Cefixime is a suitable oral alternative.

31. ENTERIC FEVER [TYPHOID]
o PREVENTION
• Vaccines
• Two vaccines are available.
• One is injected in a single dose at least one week before travel.
• One is given orally in four capsules, with one capsule to be
taken every other day.
• Wash your hands.
• Avoid drinking untreated water.
• Avoid raw fruits and vegetables.
• Choose hot foods.

32. SALMONELLA - GASTROENTERITIS
o CAUSATIVE ORGANISMS
• May be caused by any salmonella except S. typhi.
• S. typhimurium is the most common spp.
• Some other common spp. have been S. enteritidis, S haldar,
Sheidelberg, S. agona, S. virchow, S. seftenberg, S. indiana,
S. newport, and S. anatum.

33. Electron Micrograph of Salmonella typhimurium

34. SALMONELLA - GASTROENTERITIS
o PATHOGENESIS
• Transmits from animal to human. Acquired by ingestion of
food items infected with a high concentration of the
bacteria.
• In healthy adults, the acidity of the stomach can kill the
bacteria if they are present in a low concentration.
• Once in the intestines, the bacteria invade the cells lining
the intestine.
• The initial presence of bacteria ruffles the host cell's
membrane creating an efficient route to obtain necessary
macromolecules. This is known as macropinocytosis.

35. SALMONELLA - GASTROENTERITIS
• An enterotoxin results in the release of fluids from the cell
into the lumen (Responsible for the diarrhea and vomiting
symptoms) and the release of endogenous pyrogens causing
fever.
• The cytotoxin is responsible for the disintegration of the
cytoplasm. It accomplishes this by inhibiting protein
synthesis and causes calcium ions to rush in.
• The bacteria can move to the liver or spleen, where they are
able to replicate.

36. SALMONELLA - GASTROENTERITIS
• After replication, they can migrate back to the intestines where
they can be expelled and transmitted to new hosts.
• The bacteria reproduce extremely quickly causing illness due
to the sheer number of foreign bacteria present.
• At the peak of infection, there can be up to one
billion Salmonella bacteria present per gram of feces.

37. SALMONELLA - GASTROENTERITIS
Electron photomicrograph Salmonella typhimurium invading guinea pig ileal epithelial cells

39. SALMONELLA - GASTROENTERITIS
o SYMPTOMS
• Begins 12 to 72 hours after consuming a contaminated food
or beverage.
 Fever.
 Abdominal cramps.
 Diarrhea; Diarrhea is often mucopurulent (containing mucus or
pus) and bloody. Dehydration.
 Dehydration.
• Lasts anywhere from 4-7 days.

40. SALMONELLA - GASTROENTERITIS
• CONTAMINATION & TRANSMISSION
• Eggs and products containing raw eggs.
• Undercooked poultry and handling of the raw meat.
• Raw red meat and some products intended to be eaten raw.
• Unpasteurized milk and products thereof.
• Cross-contamination of all foodstuffs is possible
if Salmonella is present in the environment. Undercooking
food or keeping food in a warm environment, increases the risk
of infection.

41. Electron micrograph of Salmonella in the pores of a lettuce leaf (Pseudo-color)

42. SALMONELLA - GASTROENTERITIS
o EPIDEMIOLOGY
• They are estimated to cause 94 million cases of
gastroenteritis and 115,000 deaths globally each year.
• Travelers with salmonellosis were most likely to report
visiting the following countries: Mexico (38% of travel-
associated salmonellosis), India (9%), Jamaica (7%), the
Dominican Republic (4%), China (3%), and the
Bahamas (2%).
• Salmonella infection and carriage has been reported
among internationally adopted children.

43. SALMONELLA - GASTROENTERITIS
o DIAGNOSIS
• About 90% of isolates are obtained from routine stool
culture.
• Also obtained from blood, urine, and material from sites
of infection.
• Isolates of salmonellae are needed for serotyping and
antimicrobial susceptibility testing.

44. SALMONELLA - GASTROENTERITIS
o TREATMENT
• Fluoroquinolones are often employed for empiric treatment
of patients with moderate to severe travelers’ diarrhea.
• Azithromycin and rifaximin are also commonly used.
o PREVENTION
• No vaccine is available against non- typhoidal infections.
• Frequent hand washing, especially after contacting animals
or their environment.
• Traditional Precautions taken while travelling.

45. SALMONELLA - GASTROENTERITIS
o REFERENCES
• http://www.webmd.com/a-to-z-guides/typhoid-fever#1
• https://www.cdc.gov/salmonella/general/
• https://www.foodsafety.gov/poisoning/causes/bacteriavirus
es/salmonella/
• http://www.who.int/mediacentre/factsheets/fs139/en/
• http://wwwnc.cdc.gov/travel/yellowbook/2016/infectious-
diseases-related-to-travel/salmonellosis-nontyphoidal
• http://www.ehagroup.com/resources/pathogens/salmonella/

46. THANK YOU