Lecture 3 - Gram Negative Bacteria

Question 1

Enterotoxigenic E. Coli

Answer 1

• Most common cause of bacterial diarrhea in developing countries.
• Responsible for travelers diarrhea.
• Have Bacterial surface proteins (colonization factors) are heat-stable and heat-labile enterotoxins.

Question 2

Enteropathogenic E. Coli

Answer 2

• Diarrhea in infants and children

- Defined by presence of LEE (cluster of virulence genes) and absence of shiga/enterotoxins.

Question 3

Enteroaggregative E. Coli

Answer 3

• Stacked brick arrangement
• Highly variable genes
• Chronic Diarrhea and growth retardation in children

Question 4

Shiga Toxin Producing E. Coli

Answer 4

• Inactivates ribosomes, inhibiting protein synthesis.

- Ingestion of <100 bacteria can cause disease

Question 5

Enteroinvasive E. Coli

Answer 5

Rare, invades colon epithelium to produce diarrhea and occasionally dysenteric symptoms (fever, cramps, blood/leukocytes in stool)

Question 6

Salmonella

Answer 6

• Attaches to mucosa of small intestine and invade microfold cells as well as RBCs.
• Spreads via fecal-oral or contaminated food.

Question 7

Salmonella Typhi

Answer 7

Only salmonella with low ID50

Question 8

Salmonella Clinical Diseases

Answer 8

• Gastroenteritis: most common salmonellosis
• Septicemia
• Enteric Fever: Salmonella Typhi causes typhoid
• Asymptomatic Colonization: Typhoid and paratyphoid strains can maintain chronic colonization for years after symptoms

Question 9

Shigella

Answer 9

• Invaded and replicated in colon cells
• Large virulence plasmid encodes adherence genes
• 4 Main Species: Shigella dysenteriae(produces shiga), Shigella flexneri, Shigella boydii, Shigella sonnei.
• Shigellosis: Abdominal cramps, diarrhea, bloody stool, fever

Question 10

Yersinia

Answer 10

• Resist phagocytosis by Type III secretion system
• F1 gene and plasminogen activator protease gene encode virulence.
• Causes plague

Question 11

Pneumonic Plague

Answer 11

Shorter incubation with higher mortality rate

Question 12

Yersinia Enterocolitica

Answer 12

• Causes enterocolitis, very rare, usually only in children.
• Pseudoappendicitis is the main complication.
• Y. Pseudotuberculosis can also cause same symptoms
• Psychrotrophs (can survive extremely low temp)

Question 13

Klebsiella

Answer 13

Causes nosocomial lobar pneumonia, STDs that mimic syphilis, donovanosis

Question 14

Proteus

Answer 14

Proteus mirabilis causes UTIs and kidney stones

Question 15

Other Enterobacteriacae

Answer 15

Enterobacter, citrobacter, Morganella, Serratia, rare in patients with good immunity

Question 16

Enterobacteriacea Diagnosis

Answer 16

• Cold enrichment for Yersinia
• E coli culturing
• Enteropluri tube for biochemical detection
• Test for presence of Shiga
• PCR

Question 17

Vibrio

Answer 17

Gram negative rods that are oxidase positive, primarily found in water.

Question 18

Vibrio Vulnificus

Answer 18

• Infection when skin lacerations/abrasions come in direct contact with contaminated salt water.
• Redness, swelling, pain, bullae, sepsis, and necrotizing fasciitis.

Question 19

Pseudomonas

Answer 19

• Gram negative rod found in soil, decay, vegetation, water.
• Highly resistant, can grow in distilled water, have adhesins, toxins, and many antibiotic resistance genes.
• Blue green tint make it easy to identify

Question 20

Pseudomonas Diseases

Answer 20

• Tracheobronchitis
• Necrotizing bronchopneumonia
• Skin infections (green nail, folliculitis)
• UTIs, swimmers ear, eye infections
• Bacteriemia

Question 21

Campylobacter

Answer 21

Most common cause of bacterial gastroenteritis in developed and developing countries

Question 22

Helicobacter

Answer 22

• H. Pylori

- Gastritis, peptic ulcers, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue B-Cell lymphomas.