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Microbiology > Gram Negative Rods > Flashcards

Gram Negative Rods Flashcards

1
Q

Intestinal Mechanism of Defenses that Bacteria Must Overcome

A 
Gastric acid (kills many bacteria) 
Intestinal motility (removes bacteria)
Normal flora (antibiotics)
Mucosal immunity (IgA)
Inflammation (phagocytes, complement)
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2
Q

Cell types of intestine that bacteria interact with

A

Enterocytes
M Cells-specialized for transcytosis of antigens
Macrophages and neutrophils

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3
Q

Three Types of Intestinal Infections

A
  1. Non-inflammatory
  2. Inflammatory
  3. Penetrating
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4
Q

Non-inflammatory diarrhea

A

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)

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5
Q

Vibrio Cholera

A

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

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6
Q

Three Types of E. Coli that cause diarrhea

A
  1. Enterotoxigenic E. Coli (ETEC)
  2. Enteropathogenic E. Coli (EPEC)
  3. Shiga toxin producing E. Coli (STEC)
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7
Q

Enterotoxigenic E. Coli

A

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

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8
Q

Enteropathogenic E. Coli

A

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

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9
Q

Inflammatory Diarrhea

A

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

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10
Q

Shigella

A

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

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11
Q

Non-typhoidal Salmonella

A

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

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12
Q

Campylobacter

A

Gram negative rod; enterobacteria causing inflammatory intestinal infection

Rods are curved

Associated with GBS

From contaminated food

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13
Q

Helicobacter

A

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

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14
Q

Enterobacteria Yersinia

A

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)

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15
Q

Typhoidal Salmonella

A

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

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16
Q

UTI

A

Usually caused by E. Coli; attach to urinary tract with pili

Causes urgency, frequency, and dysurina

Ascending

17
Q

Klebsiella

A

Gram negative rod, enterobacteria

Causes necrotizing pneumonia; bloody sputum

Special stain for capsule; major virulence factor

18
Q

Haemophilus Influenzae

A

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

19
Q

Bordetella Pertussis

A

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

20
Q

Legionella Pneumonphila

A

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)

21
Q

Brucella

A

Gram negative rod, zoonotic

From unpasteurized dairy and livestock

Systemic febrile illness

22
Q

Pasteurella multocida

A

Gram negative coccobacillus, zoonotic

In oral flora of cats and dogs, so associated with animal bites

Can progress into soft tissue infection

23
Q

Francisella tularensis

A

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

24
Q

Yersinia Pestis

A

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

25
Q

Pseudomonas Aeruginosa

A

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

Microbiology (10 decks)

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