Salmonella, Shigella, Yersinia

3 primary human intestinal pathogens that are NOT normal GI flora

Salmonella, Shigella, yersinia

Salmonella found in and transmitted by

• GI tracts of animals

• contaminated or undercooked animal products

Shigella transmission

human carriers coupled with improper sanitary conditions and poor personal hygiene

Yersinia transmission

By animals

3 main species of Salmonella

Salmonella enteritidis, Salmonella choleraesuis, Salmonella typhi

4 forms of Salmonellosis

1. acute gastroenteritis or food poisoning (vomiting + diarrhea)

2. typhoid fever

3. nontyphoidal bacteremia

4. carrier state following infection

Salmonella appearance on MAC and Hektoen/XLD

• MAC: clear, colorless (lactose =)

• Hektoen/XLD: black centers

Salmonella:

• Indole

• VP

• Urease

• PAD

• H2S

• KCN

• indole =

• VP =

• urease =

• PAD =

• most H2S + (EXCEPT Salmonella paratyphi A)

• no growth in KCN

Gastroenteritis (Salmonellosis)

• eating contaminated food/water

• usually self limiting

• S. enteritidis serotypes

Bacteremia (Salmonellosis)

prolonged fever and intermittent bacteremia

Describe carrier state of Salmonellosis

• harbored in gallbladder (site of chronic carriage)

• microbes excreted in feces (either continuously or intermittently)

Transmission of Typhoid Fever

• poor sanitation

• bad water purification systems

• carriers

Symptoms of typhoid fever

• prolonged fever

• bacteremia

• RES involvement

• dissemination to other organs

When do you observe the microbes in typhoid fever???

• 1st week: in blood

• 2nd/3rd week: stool

Complications of typhoid fever

• necrosis

• pneumonia

• meningitis

• osteomyelitis

• endocarditis

• abscesses

Salmonella:

• lactose

• indole

• VP

• TDA

• urease

• gas made from glucose ferm

• H2S

• decarb

• sugars

• lactose =

• indole =

• VP =

• TDA =

• urease =

• gas from Glu + (except S. typhi)

• H2S +

• decarb + (typically)

• variable sugars

3 important subspecies of Salmonella enterica

S. typhi, S. choleraesuis, S. paratyphi

For salmonella, lysine decarb RULES OUT __

S. paratyphi

Salmonella: Ornithine decarb RULES OUT __

S. typhi

Salmonella: Trehalose fermentation RULES OUT __

S. choleraesuis

Salmonella Virulence factors

• fimbriae

• ability to traverse intestinal mucosa

• enterotoxin involved in gastroenteritis

• O and H antigens

• Capsular antigen Vi (similar to K)

Onset of Salmonella gastroenteritis

• 8-36 hrs after eating contaminated food

• nausea, vomiting, fever, chills

• watery diarrhea, abdominal pain

• usually self limiting

Antibiotics for Salmonella gastroenteritis

• chloramphenicol

• ampicillin

• trimethoprim-sulfamethoxazole

Clinical features of enteric fevers (salmonella)

• prolonged fever

• bacteremia

• Involvement of Reticuloendothelial system (particularly liver, spleen, intestines, mesentery)

• dissemination to mult. organs