Gram Negative Rods Flashcards
Intestinal Mechanism of Defenses that Bacteria Must Overcome
Gastric acid (kills many bacteria) Intestinal motility (removes bacteria) Normal flora (antibiotics) Mucosal immunity (IgA) Inflammation (phagocytes, complement)
Cell types of intestine that bacteria interact with
Enterocytes
M Cells-specialized for transcytosis of antigens
Macrophages and neutrophils
Three Types of Intestinal Infections
- Non-inflammatory
- Inflammatory
- Penetrating
Non-inflammatory diarrhea
Watery diarrhea w/o fever or WBCs in feves
Caused by exotoxins that stimulate NaCl movement from enterocyte to lumen
Vibrio cholerae and toxin-producing E. coli (enterotoxic and enteropathogenic E. coli)
Vibrio Cholera
Enterobacteria: Gram negative rod, peritrichous flagella, oxidase negative
O1 serotype causes non-inflammatory intestinal infection leading to watery diarrhea
Virulence factor=exotoxin–>permanently activates Gs to stimulate AC–>increased cAMP causing increased Cl- transport
Grow on TCBS
Therapy: oral or IV rehydration; antibiotics can be give to shorten the disease
Three Types of E. Coli that cause diarrhea
- Enterotoxigenic E. Coli (ETEC)
- Enteropathogenic E. Coli (EPEC)
- Shiga toxin producing E. Coli (STEC)
Enterotoxigenic E. Coli
Gram negative rod
Adheres to intestinal mucosa via pili
Has two exotoxins distinguished by heat sensitivity (labile toxin and stable toxin); works like cholera, but because there is less toxin, effects are less severe
Cause of traveler’s diarrhea
Enteropathogenic E. Coli
Enterobacteria; Gram negative rod
Adheres to surface of enterocytes and uses Type III secretion system
Brush border disappears
Alters cytoskeleton!! Pedestal that cups bacterium is produced
Inflammatory Diarrhea
Bacteria invade wall; look for lactoferrin
Caused by Gram negative rods Shigella, Salmonella, and invasive E. coli, and campylobacter
Causes diarrhea that is bloody and has WBCs in feces; fever
Types III secretion system; invade and kill enterocytes
Virulence is caused by adhesions, cytotoxins, and sometimes cell invasion
Diarrhea from production of inflammatory mediators by enterocytes and neutrophils
Shigella
Enterobacteria, Gram negative rod
Also Shiga toxin producing E. Coli (STEC)
Causes inflammatory enteritis
Only infects humans; identical to E. Coli; invade enterocytes via basolateral surface to cause phagocytosis by Type III; polymerization of actin
Hemolytic-uremic syndrome (HUS)-microvascular damage in kidney, red cell lysis
Causes low volume stools with blood, WBCs, mucus, cramps
4 species defined by O-antigen
Non-typhoidal Salmonella
Gram negative rod, enterobacteria causing inflammatory infection
Infection from animals to people usually through contaminated food
Go from lumen, through M cells, and invade enterocytes
Cause apoptosis of macrophages through type III system, which causes non-bloody diarrhea, fever, nausea, vomiting
Campylobacter
Gram negative rod; enterobacteria causing inflammatory intestinal infection
Rods are curved
Associated with GBS
From contaminated food
Helicobacter
Gram negative rod; enterobacteria causing inflammatory intestinal infection
Chronic infection/inflammation–>stomach cancer, gastric lymphoma
Live below mucus layer, so avoid stomach acid
Urease converts urea to ammonia
Diagnose with biopsy, breath test (administer radiolabeled carbon; presence of urease from helicobacter will cause exhalation of radiolabeled CO2)
Treat with antibiotics and PPI to reduce gastric acid
Enterobacteria Yersinia
Gram negative rod, enterobacteria causing penetrating intestinal infection
Moves from intestine to lymph nodes; painful inflammation
Type III system
Grows in refrigerated animal products (milk, blood)
Typhoidal Salmonella
Gram negative rod, enterobacteria that causing penetrating intestinal inflammation
Multiplies in phagocytic vacuoles after penetrating intestine via M cells
Can be carried for several years in the gallbladder
UTI
Usually caused by E. Coli; attach to urinary tract with pili
Causes urgency, frequency, and dysurina
Ascending
Klebsiella
Gram negative rod, enterobacteria
Causes necrotizing pneumonia; bloody sputum
Special stain for capsule; major virulence factor
Haemophilus Influenzae
Gram negative rod, respiratory pathogen
Special growth requirements=NAD and hemin, so can grow on chocolate agar
Only infects humans; upper airways
Virulence factors: capsule, IgA protease, iron acquisition
Causes otitis media, sinusitis, epiglottitis, pneumonia, meningitis, septic arthritis
Vaccine against type b
Bordetella Pertussis
Gram negative rod, respiratory pathogen
Grows on blood agar with charcoal
Only infects humans; spreads via respiratory route
Virulence factors: fimbriae, filamentous hemaggultinins, adhesins, toxins
Toxins= tracheal cytotoxin, adenylate cyclase toxin, pertussis toxin
Key diagnostic feature=lymphocytosis
Prevention of DTaP
Legionella Pneumonphila
Gram negative rod, respiratory pathogen
Use direct fluorescent antibody stain
Grow on BCYE agar…very fastidious
Colonizes warm bodies of water in protozoan host; spreads in aerosol from water supply (A/C, water taps, shower heads)
Brucella
Gram negative rod, zoonotic
From unpasteurized dairy and livestock
Systemic febrile illness
Pasteurella multocida
Gram negative coccobacillus, zoonotic
In oral flora of cats and dogs, so associated with animal bites
Can progress into soft tissue infection
Francisella tularensis
Gram negative rod, zoonotic
Transmission by rabbits
Highly infectious
Tularemia:
Ulceroglandular-formation of an ulcer at the site of skin infection; lymphadenopathy; most common
Oculoglandular-eye is site of inoculation; lymphadenopathy
Oral or pharyngeal-contaminated food/water
Respiratory infection
Yersinia Pestis
Gram negative rod, zoonotic
From rodent to flea to human; multiplies in human lymph node to cause the black plague
Can spread human to human via sputum
Bacteria spreads to blood, lungs and meninges
Safety pin appearance
Virulence factors: phagocyte paralysis, Fe acquisition, capsule
Pseudomonas Aeruginosa
Gram negative rod, zoonotic; obligate oxidizer
In biofilm, which can live on biotic or abiotic surfaces and is very hard to kill; found in contaminated water
Virulence factors: extracellular polysaccharides, pili, LPS, extracellular enzymes, exotoxin, type III secretion system
Multiple mechanisms of antibiotic resistance; bacteria in middle do different things than bacteria on outside
Opportunist infection; Nosocomial infection
Seen in CF patients
