Bact GI 2

Question 1

Describe the characteristics of Enteropathogenic E. Coli (EPEC)

Answer 1

• Gram Negative facultative anaerobe
• Moderately invasive
• *SMALL INTESTINE DISEASE**
• Symptoms: Watery Diarrhea due to tissue destruction (microvilli)

Question 2

Describe the Pathogenesis of EPEC

Answer 2

Adhesins:

• BfpA (bundle forming pilus) initiates binding
• Type III secretion system of Tir
• No toxins released which results in WATERY DIARRHEA
• Attaching and Effacing of EPEC forms a lesion (AE lesion) and loss of microvilli

Question 3

Describe the Diagnosis and Treatment of EPEC

Answer 3

Culture and biochemical tests:
- Ferments Lactose (red on MacConkey Agar)
- Indole Positive
**PCR is used to identifiy EPEC**
Treatment: Supportive therapy

Question 4

Describe characteristics of Enterotoxigenic E. Coli (ETEC)

Answer 4

• Gram negative, Faculatative anaerobe
• NON-invasive
• *SMALL INTESTINE DISEASE**
• -> “TRAVELERS Diarrhea” = associated with travel to developing countries and consumption of contaminated water/ice (T for travelers)

Question 5

Describe the pathogenesis of ETEC

Answer 5

1) Adherence to epithelial cell via Fimbraie
2) produces two types of toxins:
- LT - heat LIABLE toxin (AB toxin and increase cAMP)
- ST - heat STABLE toxin (NON-AB toxin, does NOT enter cell, increase cGMP)
3) NON invasive just cause WATER DIARRHEA

Question 6

Describe diagnosis and treatment of ETEC

Answer 6

DIAGNOSIS:
- Clinical history
- DNA probes to detect LT and ST encoding genes in clinical samples/cultures
TREATMENT: Supportive therapy

Question 7

Describe characteristics of Salmonella Typhi

Answer 7

• Gram negative, Facultative anaerobe
• Motile rods, flagellated (H-antigen)
• Acid Tolerant
• INTRACELLULAR pathogen
• HIGHLY adapted to humans ( humans are the only reservoir)
• Fecal-oral transmission (need a lot of bacteria to cause disease)
• *INFLAMMATORY SMALL INTESTINE**

Question 8

Describe the clinical manifestations of S. Typhi

Answer 8

Clinical manifestations occurs 13 days after incubation
SYMPTOM PROGRESSION:
- Fever with headache
- Rising fever over 3 days
- TYPHOID fever (prolonged fever, 4 weeks)
- Followed by GI symptoms (chronic colonization of Gall bladder, reinfection of intestines)
Shedding of S. Typhi in stool

Question 9

Describe the pathogenesis of S. Typhi

Answer 9

1) Bacteria invade and replicate in M (microfold) cells of Peyer’s patches in the small intestine
2) Pili mediate the attachment of bacteria to gut cells; Type II secretion systems facilitate entry into cells and spread to adjacent cells resulting in Bacteremia

Question 10

Describe the Diagnosis and treatment of S. Typhi

Answer 10

DIAGNOSIS: Culture of stool and blood samples on selective media
TREATMENT: ANTIBIOTIC THERAPY based on susceptibility profile (Broad spectrum cephlosporin or Fluoroquinolones, trimethoprim-sulfamethoxazole)
PREVENTION: Avoid potential sources of infection, vaccination for travelers to endemic areas.

Question 11

Describe the characteristics of NONTYPHOIDAL Salmonella

Answer 11

• Gram negative, Facultative anaerobe
• Motile rods, flagellated (H antigen)
• Acid tolerant
• INTRACELLULAR pathogens
• *SMALL INTESTINE INFLAMMATORY DISEASE**
• Infection due to contaminated food (poultry, eggs, dairy products, etc)

Question 12

Describe the Clinical manifestations of Nontyphoidal salmonella

Answer 12

Clinical manifestations occur between 6-48h Post ingestion

• Nausea and vomiting followed by abdominal cramps and WATERY diarrhea
• Persistant diarrhea for 3-4days (with or without blood) (loose stool –> severe dysentery-like stool)
• Spontaneous resolution within 7 days
• 50% of cases present with fever*

Question 13

describe the pathogenesis of Nontyphoidal salmonella

Answer 13

1) inital stages of infection similar to S. Typhi pathogenesis
- -After entry into macrophage 2 scenarios
1) Rapid killing of macrophage via multiple mechanisms (massive inflammatory response that confines infection or active fluid excretion)
2) carriage in macrophage (IMMUNOCOMPROMISED PATIENTS)
- systemic dissemination, bacteremia
- focal infections - arthritis, osteomyelitis, endocarditis etc.

Question 14

Describe the diagnosis and treatment of Nontyphoidal salmonella

Answer 14

DIAGNOSIS: - Serology (detection of anti-Vi antigen ab
- Culture from blood and stool using selective/differential media (Non-lactase fermenting + produces H2S)
TREATMENT:
- SALMONELLA GASTROENTERITIS - antibiotics NOT recommended
- Salmonella systemic infection - Antibiotic therapy depending on resistance profile
NO VACCINE AVAILABLE

Question 15

Describe the characteristics of Campylobacter Jejuni

Answer 15

• Gram negative rod (CURVED or “Sea-gull SHAPED)
• Microaerophilic
• Many animal reservoirs
• Invasive
• *INFLAMMATORY SMALL INTESTINE DISEASE**

Question 16

describe the clinical manifestations of Campylobacter Jejuni

Answer 16

• Ulceration and acute enteritis (Watery Diarrhea to severe cases of diarrhea)
• Sepsis
• LONG incubation time (2-11days)
• Sequelae (guillain-barre syndrome)

Question 17

Describe Sequelae caused by Campylobacter Jejuni

Answer 17

• *Guillain-Barre Syndrome (GBS)**
• heterogeneous syndrome
• Acute immune-mediated polyneuropathy
• PROGRESSIVE, fairly symmetric muscle weakness accompanied by absent or depressed deep tendon reflexes
• Symptoms vary from difficulty walking to nearly complete paralysis

Question 18

Describe the Diagnosis and treatment of Campylobacter Jejuni

Answer 18

DIAGNOSIS: Culture in selective media in a MICROAEROPHILIC ENVIRONMENT
Treatment:
- supportive therapy
- Antibiotic therapy for ONLY invasive disease and based on susceptibility profile (Macrolide)