Micro Flashcards
Antigen for gram neg and gram pos
Gram neg - LPS, the outer membrane (endotoxin)
- lipid A induces TNF and IL-1
Also have periplasmic space where B-lactamases are located
Gram pos - the cell wall
- lipoteichoic acid incudes TNF and IL-1
Normal content of capsule, and exception
Polysaccharide layer
Except Bacillus anthracis - D-glutamate
- edema factor, lethal factor, protective antigen
Sopre chemical composition
Dipicolinic acid
Encapsulated organisms
Even Some Pretty Nasty Killers Have Shiny Bodies, it’s Cool!
E coli Strep pneumo Pseudomonas aeruginosa Neisseria meningitidis Klebsilella pneumoniae Haemophilus influenzae type B Salmonella typhi group B strep Cryptococcus neoformans
SHiNE SKiS Strep pneumo H flu type B N meningitides E coli Salmonella Klebsiella group b Strep
Asplenic pts can’t opsonize as well - vaccinate against Strep pneumo, N meningitides, and H flu type B
Capsule is anti-phagocytic Capsule + protein conjugate is vaccine antigen - promotes T cell activation, subsequent class switching
Quelling reaction
test to determine if bacteria have capsule
- anti-capsular serum added to bacteria - capsule appears swollen under microscope
Ziehl-Neelsen stain
Carbol Fuchsin - analine dye - binds mycolic acid
- acid fast bacteria stain
Stains: Nocardia, Mycobacteria, and the protozoa Cryptospodium oocysts
How it works: stain with carbolfuchsin, decolorize with acid alcohol, counterstain with methylene blue - acid fast will retain stain
Bacteroides fragilis
Gram neg rob; anaerobe; below the diaphragm
Produce beta-lactamase; operons controlled by inversion
Necrotizing fasciitis, foul smelling; liver and other abscess, surgical incision infxn
Colonizes human flora
diabetic foot ulcer - diminished blood supply facilitates growth of anaerobes
Rx - imidazoles - metronidazole; lincosamides
- resistant to penicillins
CGD have what infection?
recurrent catalase positive organisms cuz NADPH oxidase deficiency - can’t form superoxide radical so can’t kill organism with catalase cuz these organism can just break down the H2O2 that is around
Ex:
- Nocardia, Pseudomonas, Listeria, Aspergillus, Candida, E coli, Staphylocci, Serratia
Biofilm producing organisms
S epidermidis - prosthetic, indwelling caths
Strep mutans, sanguinis - dental plaques
P aeruginosa - CF pneumonia, contact lenses
Viridans strep - endocarditis
H flu non-typeable - otitis media`
Corynebacterium diphtheriae
Diphtheria via exotoxin made by B-prophage that inhibits protein synthesis via ADP-ribosylation of EF2 (like exotoxin A of P aeurinosa)
- pseudomembranous pharyngitis, lymphadenopathy/bull neck, myocarditis, arryhthmias
Lab diagnosis - gram pos rod, metachromatic granules, positive Elek test for toxin, black colonies on cystine-tellurite agar
Toxin gets from pharynx to cardiac and cerebral tissues/cortical neurons
Tx: antitoxin, penicillin/erythromycin, DPT vaccine
Only gram pos with endotoxin
Listeria monocytogenes
- actin polymerization, intracellular spread from cell to cell, avoids antibodies
- tumbling motility
- ampicillin treatment
- listeriolysin O is pore forming toxin to lyse vacuolar membrane, activated within acidified phagosomes
Unpasteurized dairy, deli meats, transplacental and vaginal transmission
Nocardia vs actinomyces
Nocardia - gram pos aerobe - long, branching filaments resembling fungi - weakly acid fast - found in soil - pulmonary infxns in immunocompromised - cutaneous infxns in immunocompetent after trauma - treatment - sulfonamides Actinomyces - gram pos anaerobe - normal oral flora - oral/facial abscesses with sinus tracts - yellow sulfur granules - treat with penicillin
Tuberculosis damage is lung hypersensitivity type?
Delayed type (IV) - Th1 cells stimulate macrophages and CD8 T cells
If sarcoidosis, PPD negative
IGRA has fewer false positives
Mycobacterium tuberculosis factors
Cord factor inhibits macrophage maturation and induces release of TNF-a
Sulfatides inhibit phagolysosome fusion
Th1 cells and macrophages contain TB in granuloma
MAC prophylaxis with azithromycin when CD4 below 50
Leprosy
Lepromatous - Th2, low cell mediated immunity
Tuberculoid - Th1, high cell mediated immunity
