Lecture 3 - Gram Negative Bacteria Flashcards
Enterotoxigenic E. Coli
- 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.
Enteropathogenic E. Coli
- Diarrhea in infants and children
- Defined by presence of LEE (cluster of virulence genes) and absence of shiga/enterotoxins.
Enteroaggregative E. Coli
- Stacked brick arrangement
- Highly variable genes
- Chronic Diarrhea and growth retardation in children
Shiga Toxin Producing E. Coli
- Inactivates ribosomes, inhibiting protein synthesis.
- Ingestion of <100 bacteria can cause disease
Enteroinvasive E. Coli
Rare, invades colon epithelium to produce diarrhea and occasionally dysenteric symptoms (fever, cramps, blood/leukocytes in stool)
Salmonella
- Attaches to mucosa of small intestine and invade microfold cells as well as RBCs.
- Spreads via fecal-oral or contaminated food.
Salmonella Typhi
Only salmonella with low ID50
Salmonella Clinical Diseases
- 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
Shigella
- 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
Yersinia
- Resist phagocytosis by Type III secretion system
- F1 gene and plasminogen activator protease gene encode virulence.
- Causes plague
Pneumonic Plague
Shorter incubation with higher mortality rate
Yersinia Enterocolitica
- 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)
Klebsiella
Causes nosocomial lobar pneumonia, STDs that mimic syphilis, donovanosis
Proteus
Proteus mirabilis causes UTIs and kidney stones
Other Enterobacteriacae
Enterobacter, citrobacter, Morganella, Serratia, rare in patients with good immunity
Enterobacteriacea Diagnosis
- Cold enrichment for Yersinia
- E coli culturing
- Enteropluri tube for biochemical detection
- Test for presence of Shiga
- PCR
Vibrio
Gram negative rods that are oxidase positive, primarily found in water.
Vibrio Vulnificus
- Infection when skin lacerations/abrasions come in direct contact with contaminated salt water.
- Redness, swelling, pain, bullae, sepsis, and necrotizing fasciitis.
Pseudomonas
- 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
Pseudomonas Diseases
- Tracheobronchitis
- Necrotizing bronchopneumonia
- Skin infections (green nail, folliculitis)
- UTIs, swimmers ear, eye infections
- Bacteriemia
Campylobacter
Most common cause of bacterial gastroenteritis in developed and developing countries
Helicobacter
- H. Pylori
- Gastritis, peptic ulcers, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue B-Cell lymphomas.
