Enterobacteriaceae III

Question 1

Frequent passage of stool containing blood and mucus, straining and painful defecation

Answer 1

Dysentary

Question 2

Shigella:
S. sonnei, S. flexneri, S. dysenteriae, S. boydii

Disease
Pathogenesis
Diagnosis
Treatment

Answer 2

Dysentary (voluminous watery stool) - common cause of outbreaks (foodborne, daycare centers, contaminated water) - also fever, abdominal cramps

Invades colonic epithelial cells and survives low gastric pH, multiplies in small intestine cells, spreads to adjacent cells, causes inflammation and ulceration and destroys colonic mucosa

Stool culture, assay for Shiga toxin, fecal leukocytosis

Antibiotics, replace lost fluids, avoid antimotility agents

Question 3

Shigella species that is foodborne

Answer 3

S. sonnei

Question 4

Shigella species that is sexually transmitted during male-male sex

Answer 4

S. flexneri

Question 5

What is the infectious dose of shigella?

Answer 5

10-100 organisms (VERY LOW)

Question 6

What population is incidence of Shigella infection highest in?

Answer 6

Kids ages 1-4

Question 7

What are possible immunologic complications of enteric infection?

What HLA type has highest risk?

Answer 7

Post-infection reactive arthritis (ReA) (aka Reiter’s syndrome) - arthritis, urethritis, conjunctivitis
- HLA-B27 assoc w/ risk

Erythema nodosum - nodular lesions that lack discrete borders

Question 8

Inflammation where tendon attaches to bone

Answer 8

Enthesopathy

Question 9

Small hard nodules on soles of feet

Answer 9

Keratoderma blenorrhagica

Question 10

Two types of infections caused by Salmonella

Answer 10

Gastroenteritis (nontyphoidal)

Typhoid or enteric fever (not typphus)

Question 11

Salmonella gastroenteritis
Sources of infection
Symptoms
Treatment

Answer 11

• Food items (raw poultry, eggs, dairy), peanut butter
• Pets - turtles, lizards, etc.

Nausea, vomiting, diarrhea (non-bloody)
Fevers, cramps, chills ,headache

Treatment: antibiotics only for at-risk patients

Question 12

Salmonella - pathogenesis (3 routes)

Answer 12

Intestinal: Ingested, passes to intestine through M cells, bacterial mediated endocytosis

Typhoid fever: bacteria pass through mucosa, enter Peyer’s patches, invade macrophages and spread

Enterocolitis: intestinal invasion and neutrophil recruitment triggers inflammation

Question 13

Salmonella gastroenteritis

Answer 13

slide 27

Question 14

Salmonella bacteremia occurs much higher in what population?

Answer 14

HIV patients, if recurring, it’s an AIDS-defining illness

Question 15

What bacteria causes typhoid fever? What is the reservoir for these organisms? Where in the body do bacteria disseminate?

Answer 15

Salmonella typhi and Salmonella paratyphi

Reservoir: humans and primates only

Spread to spleen, bone marrow, gall bladder

Question 16

What condition?

• Enterocolitis w/ or w/o diarrhea
• Low grade fever –> high grade
• Headache, malaise, chills, muscle pains
• Bradycardia
• Rose spots

Diagnosis?
Complications?
Lab findings?

Answer 16

Enteric fever

Diagnosis: blood or bone marrow biopsy

Complications: Delirium, psychosis, intestinal perforation

Lab: Leukopenia, anemia, elevated LFTs

Question 17

What types of antibiotics are ineffective against intracellular bacteria?

What antibiotics is often used instead?

Answer 17

Aminoglycosides

Quinolones, 3rd gen cephalosporins)

Question 18

What vascular complication can result from Salmonella infection?

Answer 18

Mycotic aneurysm of aorta

Question 19

What is chronic carriage? Risk factors for it?

Answer 19

Defined as persistence of organism in stool for > year

Risk: biliary abnormalities

Question 20

Yersinia enterocolitica

Pathogenesis

What does it mimic?
What toxin does it produce?
Symptoms?
Increased risk for infection?
Diagnosis
Antibiotics

Natural host?

Answer 20

Ingestion followed by mucosal ulcerations in terminal ileum, necrosis of Peyer’s patches, enlargement of mesenteric nodes

Mimics appendicitis

Heat-stable toxin (similar to Shiga toxin)

Symptoms: Diarrhea, fever, vomiting, ab pain, bloody stools, mesenteric adenitis (fever, RLQ pain, leukocytosis)

Risk: Iron overload

Diagnosis: routine culture, cold enrichment

Antibiotics: for septic patients

Natural host: zoonotic! (often isolated in pig GI tract)

Question 21

What species of Yersinia can grow at 4 degrees Celsius?

Answer 21

Y. enterocolitica - grows well on refrigerated blood products (meat)

Question 22

Yersinia pestis

What disease?
Stains?
How is it transmitted?
Symptoms?

Answer 22

Plague

Bipolar staining - “safety pin” appearance

Bite of infected flea - bacteria proliferate in regional LN’s

Symptoms: fever, chills, weakness, headache, bubos (intensely painful, swollen node), bacteremia –> septic shock, purpura, necrosis of fingers and toes from vessel blockage

Question 23

3 clinical forms of plague

Answer 23

Bubonic - bubos
Septicemic
Pneumonic - rapid, hemorrhagic pulmonary failure

Question 24

Pathogenesis of pneumonic plague

Answer 24

Bacteria from blood invade lung and cause pneumonia, coughing creates aerosols which can spread to other people

Question 25

What has a higher mortality rate? Bubonic or pneumonic plague?

Answer 25

Pneumonic