Basic Concepts Flashcards by Kevin Hanneken

4 divisions of protozoa

Sporozoa, flagellates, amoebae, and ciliates

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3 main groups of helminths

Nematodes, tapeworms, and flukes

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Steps of Gram stain

Fixation, crystal violet, iodine, alcohol (decolorization), safranin (counter stain)

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Temp range for psychrophiles

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Temp range for thermophiles

45-60 C

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Temp range for stenothermophiles

> 60 C

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Cholera toxin expressed by?

Vibrio cholerae

Requires lysogenic conversion

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Steps of Gram stain

Fixation, crystal violet, iodine, alcohol (decolorization), safranin (counter stain)

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Temp range for mesophiles

20-45 C

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Diff b/w true / primary pathogens and opportunistic / secondary pathogens

True / primary pathogens are able to infect normal hosts

Opportunistic / secondary infections exploit compromised host defenses

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Quorum sensing

Regulation of gene expression in response to fluctuations in cell-population density

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Penicillins
Type of AB
Mechanism
Specific drugs

Beta lactams
Cell wall inhibitor via binding to peptidoglycan-forming proteins (called penicillin binding proteins [PBPs]).
Dicloxacillin (antistaphylococcal), Ampicillin. Pipercillin

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Diptheria toxin expressed by?

Corynebacterium diphtheriae

Requires lysogenic conversion

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Cholera toxin expressed by?

Vibrio cholerae

Requires lysogenic conversion

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IgA
Secreted from?
What does it do?

Secreted from respiratory epithelium

Prevents attachment of organisms to epithelium

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What does Clostridium difficile do?

Causes pseudomembranous colitis after AB treatment kills normal bowel microbiota

Diff b/w true / primary pathogens and opportunistic / secondary pathogens

True / primary pathogens are able to infect normal hosts

Opportunistic / secondary infections exploit compromised host defenses

Trimethoprim-sulfamethoxazole (TMP-sulfa)
Mechanism
Use

Folic acid inhibitor (targets nucleic acids in different fashion).
Used against Gram (-) bacteria such as E coli and staphylococci.

Penicillins
Type of AB
Mechanism
Specific examples

Beta lactams
Cell wall inhibitor via binding to peptidoglycan-forming proteins (called penicillin binding proteins [PBPs]).
Dicloxacillin (antistaphylococcal), Ampicillin. Pipercillin

Cephalosporins
Type
Mechanism
Comparison to penicillin
Specific drugs

Beta lactams
Inhibits cell wall synthesis.
More resistant to inactivation by beta-lactamases than penicillins
Cephalexin, cefoxitin, ceftriaxone, cefepime, ceftaroline (Generation 1-5)

Vancomycin
Type
Mechanism
Use

Glycopeptide
Inhibits cell wall synthesis.
Works against methicillin-resistant Staph aureus (MRSA). Should be reserved for beta-lactam resistant infections or people allergic to beta lactams.

Catalase rxn
Staph
Strep

H2O2 –> H2O + O2
Staph are catalase positive
Strep are catalase negative

Aminoglycosides
Mechanism
Use
Specific drugs

Target 30S ribosomes to inhibit protein synthesis.
Only useful against aerobic organisms. Treat Gram (-) bacteria.
Getamicin and tobramycin.

Macrolides
Mechanism
Use
Specific drugs

Target 50S ribosomes to inhibit protein synthesis.
Good for people allergic to beta lactams.
Erythromycin and azithromycin

Fluoroquinolines Mechanism Specific drugs and uses

Target DNA gyrase (topoisomerase) to inhibit DNA synthesis. Ciprofloxacin used for Gram (+). Moxifloxacin used for Gram (-).

Things to ask about during history

* Timing and nature of fevers (constant, nightly, rigors, sweats) * Contact w/ others who are ill * Predisposing factors (diabetes, immunosuppression, COPD) * Recent or recurrent infection * Travel history * Animal contacts * Recent or current antimicrobial therapy

Important parts of physical exam

Temp, lymphadenopathy, skin (trauma, ulcers, line sites, rashes), organ systems

What is acid-fast stain used for?

TB diagnosis

Which 2 organisms are only bacteria 100% susceptible to penicillin?

Strep pyogenes (GAS) and Treponema pallidum (syphilis)

Kirby Bauer susceptibility test

Put AB on culture and measure diameter of death

Advantages vs disadvantages of identification via nuclei acid sequence detection

* Advantages – More rapid (hrs vs days), greater sensitivity, antigens can still be detected after tx w/ AB kills bacteria * Disadvantages – inability to do further tests (such as susceptibility / strain testing)

IgM

Produced when px first encounters pathogen and disappears quickly. Unable to cross placenta.

IgG

Formed later in response to pathogen and remains elevated for long periods of time

EMB

Eosin methylene blue. Agar specific for gram-negative rods. Inhibits growth of Gram (+) bacteria