Lecture 6.2: Enterobacteriaceae Flashcards
What is the structure of Enterobacteriaceae?
- Family of gram-negative bacteria
- Rod-shaped
- Most have flagella and fimbriae (pili) -peritrichous
- Do not form spores
- Some have capsules
Physiology of Enterobacteriaceae? (7)
- Grow rapidly and have simple nutritional requirements
- Facultative anaerobes
- They ferment glucose, reduce nitrate
- Catalase positive
- Oxidase negative unlike other gram-negative rods
- Pathogenic members of E. do not ferment lactose
- Pathogenic members of E. are resistant to bile salts
Virulence Factors of Enterobacteriaceae (6)
- Flagellar H antigen
- Capsular K or Vi antigen
• Liposaccharide (LPS)
- O antigen
- Core polysaccharide (present in all E.)
- Lipid A (responsible for endotoxin activity)
- Siderophores
- Type III secretion system
- Antimicrobial Resistance
Species of Salmonella that cause Gastroenteritis? (4)
- S. enteritidis
- S. typhimurium
- S. montevideo
- S. wien
What Salmonella species most commonly causes Gastroenteritis?
• Primarily caused by S. enteriditis
Gastroenteritis via Salmonella: Symptoms
- Nausea
- Vomiting
- Diarrhoea
- Fever
- Abdominal Cramps
- Symptoms may persist for 2-7 days
Gastroenteritis via Salmonella: Treatment
- Rehydration
* Cephalosporins if infection spreads to blood stream
How does Salmonella infect a host?
1) It attaches to mucosa (epithelial cells) of small intestine
2) This triggers endocytosis of Salmonella
3) It then remain in the endocytic vesicles where it replicates
4) S. enterica produce enterotoxins and kill host cells
5) This causes inflammation, cramps, diarrhoea and fever in host
6) It may also enter bloodstream and lead to septicaemia
Species of Salmonella that cause Enteric Fever (Typhoid Fever)? (2)
- S. typhi
* S. paratyphi (paratyphoid fever)
How is Typhoid Fever contracted?
Originates from ingestion of food and water contaminated with human excreta and through contact with infected person
What is Typhoid (Enteric) Fever? Symptoms?
- Acute, life-threatening illness caused by S. typhi
- High fever (within 10 to 14 days)
- Headache (within 10 to 14 days)
- Myalgia (within 10 to 14 days)
- Malaise (within 10 to 14 days)
- At least a week of constipation and abdominal cramping
How long do symptoms of Typhoid Fever persist?
3-4 weeks
Diagnosis of Typhoid Fever
- Stool
- Blood
- Bone Marrow
- Urine Sample Analysis
Treatments for Typhoid Fever
- Antibiotics (fluoroquinolones, chloramphenicol, cephalosporins)
- Vaccinations are also available
How does S.typhi infect a host? (6)
- Ingestion of contaminated food or water
- Invade small intestine and enter bloodstream
- Carried by white blood cells to liver, spleen, and bone marrow
- Multiply and re-enter the bloodstream
- Invade gallbladder, biliary system & lymphatic tissue of the bowel
- Then pass into the intestinal tract
Typhoid Fever: Stage 1
• A slowly rising temperature
• Relative bradycardia (unusually slow heart rate)
• Malaise (discomfort or uneasiness)
• Headache
• Cough
• In ¼ of cases, epistaxis (acute hemorrhage from the nostril, nasal cavity, or
nasopharynx)