SALMONELLA

Who is Salmonella named after?

D.A. Salmon (1885)

What was the first isolated Salmonella originally called?

Hog cholera bacillus (Salmonella choleraesuis)

Approximately how many serovars of Salmonella exist?

Over 2,000

Name some typical Salmonella species.

S. cholerasuis, S. enteritidis, S. gallinarum, S. typhi, S. typhimurium

Name an example of atypical Salmonella.

S. salamae

Name an example of Salmonella arizonae and related organisms.

S. arizonae

What are the criteria for naming Salmonella species?

Disease produced, animal host, place of isolation

Give examples of naming based on host/disease/place.

S. cholerasuis, S. dublin

Does Salmonella have a capsule?

No

Does Salmonella have flagella?

Yes, peritrichous

Does Salmonella have fimbriae?

Yes

Which Salmonella species are non-flagellated?

S. gallinarum and S. pullorum

What is the oxygen requirement of Salmonella?

Aerobic and facultative anaerobic

On which media does Salmonella grow?

BGA, MCA, Bismuth Sulfite Agar

What is the typical colony size of Salmonella?

1–4 mm (small colonies)

What is used for selective enrichment of Salmonella?

Tetrathionate Broth and Sodium Selenite

At what temperatures can Salmonella grow?

37°C and can grow at 43°C

Does Salmonella produce gas from glucose fermentation?

Yes

Does Salmonella ferment lactose?

No

What is phage typing used for?

Epidemiological typing based on sensitivity to specific bacteriophages

What are the main antigens of Salmonella?

O antigen (somatic), H antigen (flagellar), Vi antigen (capsular, in S. typhi)

What is the O antigen?

Somatic antigen from lipopolysaccharide; designated by Arabic numbers

What colony variations exist due to O antigen?

Smooth (S) colonies and Rough (R) colonies; rough may lose O antigen and reduce virulence

What is the nature of the H antigen?

Heat-labile protein

What is the H antigen composed of?

Flagellar protein (flagellin)

What phases can H antigen exhibit?

Monophasic or diphasic

What is phase variation in Salmonella called?

Andrewes phase variation

Which genes code for flagellin in phase 1 and phase 2?

H1 - phase 1 flagellin; H2 - phase 2 flagellin

Which antigen is unique to Salmonella typhi?

Vi antigen

What is the main transmission route of Salmonella?

Fecal–oral

What are common poultry infection sources of Salmonella?

Contaminated feed, egg transmission (vertical), fecal contamination

What is the carrier state of Salmonella?

Infected animals shed organisms intermittently in feces or milk

What is the worldwide distributed species of Salmonella?

S. typhimurium

Give examples of host-adapted Salmonella species.

S. abortus equi, S. abortus ovis, S. cholerasuis, S. dublin, S. gallinarum, S. paratyphi (A, C), S. pullorum, S. typhi

Give examples of non-host-adapted Salmonella species.

S. anatum, S. derby, S. newport, S. tennessee, S. typhimurium

What factors predispose animals to Salmonella infection?

Young age, poor sanitation, overcrowding, inclement weather, wild birds and rodents

What is the heat resistance of Salmonella?

Most killed at 56°C for 10–20 minutes; exception: S. senftenberg

What is the general pathogenesis of Salmonella?

Begins as enteric infection, may spread to bloodstream

Where does Salmonella colonize in the intestine?

Distal small intestine and colon

What host defenses inhibit Salmonella colonization?

Normal intestinal flora, fusiform bacteria producing volatile organic acids, blocked attachment sites

What predisposing factors enhance intestinal colonization?

Antibiotics, diet changes, water deprivation, reduced intestinal peristalsis

Describe the invasion of intestinal epithelium by Salmonella.

Penetrates brush border, enters epithelial cells, multiplies, reaches lamina propria, phagocytosed and trapped in regional lymph nodes

What tissue responses occur during Salmonella invasion?

Villous tips contract, neutrophil infiltration

How does Salmonella cause fluid exsorption?

Inflammation stimulates prostaglandins → activates adenylate cyclase → secretion of water, bicarbonate, chloride

What additional factors contribute to fluid exsorption in Salmonella infection?

Increased vascular permeability; enterotoxin similar to E. coli LT toxin

What histological findings indicate Salmonella infection?

Acute ileitis and colitis; neutrophils in feces

What causes S. septicemia?

Endotoxin release (Lipid A of LPS)

What are the effects of S. septicemia?

Fever, hemorrhage, leukopenia followed by leukocytosis, hypotension, shock, hypoglycemia

Which Salmonella species are important in cattle?

S. dublin (host-adapted), S. typhimurium (worldwide)

What are the reservoirs of Salmonella in cattle?

Carrier animals; adult cows infect calves

Which Salmonella species cause poultry diseases?

S. pullorum and S. gallinarum

What diseases do S. pullorum and S. gallinarum cause?

Bacillary White Diarrhea (S. pullorum) and Fowl Typhoid (S. gallinarum)

Which animals are susceptible to Bacillary White Diarrhea?

Young chicks

How is Bacillary White Diarrhea transmitted?

Transovarial transmission; incubator contamination

What are clinical signs of Bacillary White Diarrhea?

Chicks gather near heat, loss of appetite, sleepy appearance, diarrhea, death within hours

What lesions are seen in Bacillary White Diarrhea?

Meningoencephalitis; caseous lesions in lungs, gizzard, and heart muscle

Which animals are affected by Fowl Typhoid?

Chickens and turkeys (mainly adult birds)

How is Fowl Typhoid transmitted?

Vertical transmission, feces, broken eggs, tick Argas persicus

What are clinical signs of Fowl Typhoid?

Weakness, drowsiness, drooping wings, hyperexcitability, paresis, diarrhea

What pathology is associated with Fowl Typhoid?

Rapid anemia, leukocytosis, hemorrhages, necrosis in liver and heart, enlarged spleen

What are the effects of Paratyphoid (Salmonella Typhimurium) in birds?

Enteritis, diarrhea, septicemia

What special features does Paratyphoid infection have?

May localize in ovaries, transmitted through eggs

What signs are seen in squabs infected with Paratyphoid?

Death soon after hatching, swollen wing joints, unable to fly (megrims), gelatinous exudate in joints

What type of immunity is mainly involved against Salmonella?

Cell-mediated immunity

What type of parasite is Salmonella?

Facultative intracellular parasite

What vaccines are used against Salmonella?

Live attenuated vaccines, bacterins

What antibodies are directed against Salmonella?

Humoral antibodies against O antigen

What serological methods are used for Salmonella diagnosis?

Serological tests, agglutination test, antiglobulin test, ELISA

What are the major Salmonella species?

S. bongori, S. enterica

Name the subspecies of Salmonella enterica.

I - enterica; II - salamae; IIIa - arizonae; IIIb - diarizonae; IV - houtenae; VI - indica