Basic Concepts Flashcards
4 divisions of protozoa
Sporozoa, flagellates, amoebae, and ciliates
3 main groups of helminths
Nematodes, tapeworms, and flukes
Steps of Gram stain
Fixation, crystal violet, iodine, alcohol (decolorization), safranin (counter stain)
Temp range for psychrophiles
Temp range for thermophiles
45-60 C
Temp range for stenothermophiles
> 60 C
Cholera toxin expressed by?
Vibrio cholerae
Requires lysogenic conversion
Steps of Gram stain
Fixation, crystal violet, iodine, alcohol (decolorization), safranin (counter stain)
Temp range for mesophiles
20-45 C
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
Quorum sensing
Regulation of gene expression in response to fluctuations in cell-population density
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
Diptheria toxin expressed by?
Corynebacterium diphtheriae
Requires lysogenic conversion
Cholera toxin expressed by?
Vibrio cholerae
Requires lysogenic conversion
IgA
Secreted from?
What does it do?
Secreted from respiratory epithelium
Prevents attachment of organisms to epithelium
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
