Bacterial Infections Part 1 Flashcards Preview

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Flashcards in Bacterial Infections Part 1 Deck (24):

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


Staphylococcal Virulence Factors

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


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


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.


Alpha Hemolytic Streptococci

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


Major cause of dental caries

Strep. Mutans.


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)


Streptococcal INfection Findings

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



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


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.



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


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.


Listeriosis Findings

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



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


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.


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.



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


Nocardia Findings

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


Neisserial Infections

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


N. Meningitidis

- Bacterial meningitis in children younger than 2.


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.


Neisserial Virulence Factors

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


Whooping Cough

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


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.