Bacterial Infections Part 1 Flashcards Preview

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Flashcards in Bacterial Infections Part 1 Deck (24):
1

Staphylococcal Infections (Pyogenic)

- S. aureus: skin infections, osteomyelitis, pneumonia, endocarditis
- S. epidermidis: Opportunistic infections in IV drug abusers and in patients with catheters or prosthetic heart valves.
- S. saprophyticus: UTIs

2

Staphylococcal Virulence Factors

- Toxins that damage host cell membranes (hemolysins), induce skin sloughing (exfoliative toxins), vomiting (enterotoxins), or shock (super antigens)

3

Streptococcal Infections

- Classified by pattern of hemolysis on blood agur:
--Beta is complete or clear hemolysis
--Alpha is partial or green hemolysis
--gamma has no hemolysis

4

Beta-hemolytic streptococci

- Group A (S. pyogenes) causes pharyngitis, scarlet fever, impetigo, rheumatic fever, necrotizing fasciitis, and glomerulonephritis.
- Group B (S. agalactiae) colonizes female genital tract and causes chorioamnionitis in pregnancy.

5

Alpha Hemolytic Streptococci

- Includes Strep Pneumoniae, a common cause of adult community acquired pneumonia and meningitis.

6

Major cause of dental caries

Strep. Mutans.

7

Streptococcal Virulence Factors

- Capsules (Pyogenes and Pneumoniae)
- M-proteins that inhibit complement (progenies)
- Exotoxins that cause fever and rash (progenies) in scarlet fever
- Pneumolysiin destroys host-cell membranes and damages tissues (pneumoniae)

8

Streptococcal INfection Findings

- Diffuse interstitial neutrophilic infiltrates with minimal host tissue destruction except for some progenies that has been dubbed "flesh-eating bacteria".

9

Diptheria

- Corynebacterium Diptheriae: Slender Gram-positive rod with clubbed ends, passed as aerosol or through skin exudates.

10

Diptheria Findings

- Oropharyngeal fibrinosupporative exudate, makes an exotoxin that injures heart, nerves, and other organs.
- Toxin is phage-encoded in two parts (A and B) that blocks protein synthesis.
--B BINDs to cell surface and gets A in.
--A blocks protein synthesis by ADP ribosylation and inactivation of elongation factor-2.

11

Listeriosis

- L. Monocytogenes is Gram-positive, intracellular that causes food poisoning.
- Causes sepsis and meningitis in elderly and immosuppressed

12

Listeriosis Mechanism

- Expresses leucine-rich proteins that called internal ins that bind epithelial E-cadherin and promote internalization.
- Bacillus then uses listeriolysin O and two phospholipases to degrade the phagolysosome membrane.

13

Listeriosis Findings

- Resting Macrophages internalize but do not kill Listeria, the phages have to be activated by interferon gamma.
- Evokes exudative inflammation with neutrophils.

14

Anthrax

- Spore forming Gram positive bacillus that humans contract through contaminated animal products or powdered spores.

15

Anthrax Findings

- Necrotized lesions filled with neutrophils nd macrophages.
- Cutaneous: Painless, pruritic papules that become edematous vesicles followed by black eschar.
- Inhalation leads to sepsis, shock, and death.
- GI: contracted by eating contaminated meat, causes severe, bloody diarrhea.

16

Antrax Toxin

- Composed of B subunit involved in toxin endocytosis and A subunits of two different types:
--Edema Factor converts ATP to cyclic adenosine monophosphate (cAMP) that causes cellular water efflux.
--Lethal Factor: protease that causes cell death by destroying mitogen-activated protein kinase kinases.

17

Nocardia

- Aeroboic Gram-positive bacterium growing in branched chains that stain with acid-fast protocols.
- Found in soil and cause opportunistic infections in immunocompromised hosts.

18

Nocardia Findings

- N. asteroides causes indolent resp infections, often with CNS spread. N. brasiliensis infects skin.
- Elicits suppurative responses with granulation tissue and fibrosis.

19

Neisserial Infections

- Aerobic, Gram-negative diplococci that have growth requirements (sheep blood-enriched (chocolate) agar.

20

N. Meningitidis

- Bacterial meningitis in children younger than 2.

21

N. Gonorrhoeae

- Second most common STI.
- In men causes urethritis, in women is asymptomatic and can lead to PID, infertility, and ectopic pregnancy.
- Neonatal Infection can cause blindness.

22

Neisserial Virulence Factors

- Capsule that inhibits opsonization and antigenic variation.
-- Adhesive pili undergo genetic recombination.

23

Whooping Cough

- Bordetella pertussis, Gram-negative coccobacillus.
- Paroxysms of violent coughing.
- Causes laryngotracheobronchitis with mucosal erosion and mucopurulent exudates.

24

Whooping Cough Virulence

- Expression regulated by Bordetella virulence gene (bvg)
--Hemagglutinin binds to resp epithelium carbs and macrophage Mac-1 integrins.
-- Pertussis toxin ADP ribosylates and inactivates guanine nucleotide-binding proteins so G proteins cannot transduce signals, and bronchial epithelium are paralyzed.