Micro Flashcards
Chocolate Agar
- Factors V (NAD+) and X (hematin)
H. influenzae
Thayer-Martin Agar
Neisseria gonorrhoeae and meningitidis
Bordet Gengou Agar (potato) or Regan Lowe Medium (charcoal, blood, Abx)
Bordatella pertusssis
Tellurite Agar, Loffler Medium
C. diptheriae
Lowenstein-Jensen Agar
M. tuberculosis
Eaton Agar (requires cholesterol)
M. pneumoniae
MacConkey Agar
- Fermentation –> acid –> pink colonies
Lactose-fermenting enterics (E. coli, Klebsiella)
EMB Agar
E. coli
Charcoal yeast extract agar buffered with cysteine and iron
Legionella
Sabouraud Agar
Fungi
Yellow “sulfur” granules
Actinomyces israelii
Yellow pigment
Staph aureus
Blue-green pigment
Pseudomonas aeruginosa
Red pigment
Serratia marcescens
Protein A
- S. aureus
Binds Fc region of IgG –> prevents opsonization and phagocytosis
IgA Protease
- S. pneumo, H. flu type B, Neisseria
Cleaves IgA to colonize respiratory mucosa
M Protein
- Group A Strep
Prevents phagocytosis
- Molecular mimicry
- AI response in rheumatic fever
Type III Secretion System (Injectisome)
- Pseudomonas, Salmonella, Shigella, E. coli
Needle-like protein appendage facilitating direct delivery of toxins from certain gram negative bacteria to eukaryotic host cell
Transformation
- S. pneumo, Hib, Neisseria
Take up naked DNA from environment
- Add deoxyribonuclease –> degrades naked DNA –> no transformation seen
Conjugation
F+ = sex pilus, conjugation F- = no plasmid Hfr = F+ plasmid incorporated into bacterial chromosomal DNA (can bring flanking DNA)
Transposition
Segment of DNA jumps from one location to another (can bring flanking DNA)
- Ex. vanA gene from vancomycin-resistant Enterococcus to S. aureus
Generalized Transduction
Lytic phage infects bacterium –> cleavage of bacterial DNA –> parts of bacterial chromosomal DNA may become packaged in phage capsid –> phage infects another bacterium –> transfers genes
Specialized Transduction
Lysogenic phage infects bacterium –> viral DNA incorporates into bacterial chromosome –> phage DNA excised with some flanking bacterial genes –> DNA packaged into phage capsid –> infects another bacterium
Spore Forming Bacteria
- highly resistant to heat and chemicals
- dipicolinic acid in core
- must autoclave to kill
- Bacillus anthracis (anthrax)
- Bacilus cereus (food poisoning)
- C. botulinum (botulism)
- C. difficile (pseudomembranous colitis)
- C. perfringens (gas gangrene)
- C. tetani (tetanus)
C. diphtheriae
- Diphtheria toxin
ADP-ribosylation –> inactivates EF-2 –> no protein synthesis
- Pharyngitis with pseudomembranes in through and severe LAD (bull neck)
Pseudomonas aeruginosa
- Exotoxin A
ADP-ribosylation –> inactivates EF-2 –> no protein synthesis
- Host cell death
Shigella spp.
- Shiga toxin
Inactivates 60S ribosome by removing adenine from rRNA
- GI mucosal damage –> dysentery
- Enhances CK release –> HUS
- INVADES host cells
EHEC
- Shiga-like toxin
Inactivates 60S ribosome by removing adenine from rRNA
- Enhances CK release –> HUS (O156:H7)
- Does NOT invade host cells
ETEC
- Heat labile and heat stable toxin
Heat LABILE: overactivates adenylate cyclase –> increased cAMP –> increased Cl- secretion in gut and H2O efflux
Heat STABLE: overactivates guanylate cyclase –> increased cGMP –> decreased reabsorption of NaCl and H2O in gut
- Watery diarrhea
Bacillus anthracic
- Edema toxin
Mimics adenylate cyclase enzyme –> increased cAMP
- Edematous borders of black eschar in cutaneous anthrax
Vibrio cholerae
- Cholera toxin
Permanently activates Gs –> overactivates adenylate cyclase –> increased cAMP –> increased Cl- secretion in gut and H2O efflux
- Voluminous rice-water diarrhea
Bordatella pertussis
- Pertussis toxin
Disables Gi –> overactivates adenylate cyclase –> increases cAMP –> impairs phagocytosis –> permits survival of microbe
- Whooping cough
Clostridium tetani
- Tetanospasmin
Protease that cleaves SNARE –> inhibits vesicular fusion –> no NT release
- Spastic paralysis, risus sardonicus, “lockjaw”
- Prevents release of inhibitory (GABA and glycine) NT from Renshaw cells in spinal cord
Clostridium botulinum
- Botulinum toxin
Protease that cleaves SNARE –> inhibits vesicular fusion –> no NT release
- Flaccid paralysis, floppy baby
- Prevents release of stimulatory (ACh) at NMJ
Clostridium perfringens
- Alpha toxin
Phospholipase (lecithinase) –> degrades tissue and cell membranes
- Myonecrosis (gas gangrene)
- Hemolysis (“double zone” of hemolysis on blood agar)
Streptococcus pyogenes
- Streptolysin O
- Exotoxin A
Streptolysin O: degrades cell membrane –> Lyses RBC –> contributes to beta-hemolysis
- Host Ab against toxin (ASO) used to dx rheumatic fever
Exotoxin A: binds to MHC II and TCR outside of Ag binding site –> overwhelming release of IL-1, IL-2, IFN-gamma, TNF-alpha –> toxic shock syndrome
Staph aureus
- Toxic shock syndrome toxin (TSST-1)
- Exfoliative toxin
- Enterotoxin
- TSST-1: binds to MHC II and TCR outside of Ag binding site –> overwhelming release of IL-1, IL-2, IFN-gamma, TNF-alpha –> toxic shock syndrome
- Exfoliative toxin: scalded skin syndrome
- Enterotoxin: food poisoning
Endotoxin
- Macrophage activation –> IL-1/6 (fever), TNF-alpha (fever and hypotension), NO (hypotension)
- Complement activation –> C3a (HA release –> hypotension, edema), C5a (neutrophil chemotaxis)
- Tissue factor activation –> coagulation cascade –> DIC
Catalase positive
Staph
Coagulase positive
Staph aureus
Novobiocin resistant
Staph saprophyticus
Novobiocin Sensitive
Staph epidermidis
Catalase negative
Strep
Alpha hemolytic
- Partial reduction –> greenish/brown w/o clearing around growth
Strep viridians, Strep pneumo
Optochin resistant
Strep viridans
Optochin sensitive
Strep pneumo
Beta hemolytic
- Complete lysis of RBCs –> clear area surrounding colony on blood agar
Strep agalactiae (Group B), Strep pyogenes (Group A), Staph aureus
Bacitracin resitatnt
Group B strep
Bacitracin sensititve
Strep pyogenes (Group A)
Staph aureus
- Protein A
- TSST-1 (superantigen), exfoliative toxin, enterotoxin
Most common cause of septic arthritis in adults
Staph aureus
Most common cause of osteomyelitis
Staph aureus
R sided (tricuspid) endocarditis in IV drug user
Staph aureus
Secondary pneumonia after influenza infection
Staph aureus
Staph epidermidis
Normal flora of skin
Prosthetic devices and IV catheters
BIOFILMS
Staph saprophyticus
Uncomplicated UTI in young sexually active women (2nd to E. coli)
Strep pneumo
Lancet-shaped diplococci
Encapsulated
IgA protease
No virulence without capsule
Most common cause of meningitis
Strep pneumo
Most common cause of otitis media in children
Strep pneumo
Most common cause of pneumonia
Strep pneumo
- Rusty sputum
most common cause of sinusitis
Step pneumo
Strep pneumo vaccine
- Adults: polysaccharide w/o protein (23 valent) –> T cell independent –> IgM
- Kids: conjugated to protein (7 valent) –> robust response of T cells and B cells –> IgG
Strep viridans
Dental caries (mutans and mitis) Subacute bacterial endocarditis at DAMAGED heart valves (sanguinis) Makes dextrans --> bind to fibrin-platelet aggregates on damaged heart valves
Strep pyogenes (Group A Strep)
PYR + M protein --> rheumatic fever ASO titer detects infection Pharyngitis --> rheumatic fever and PSGN Scarlet fever
Most common cause of erysipelas (rash)
Strep pyogenes
Acute Rheumatic Fever
- Strep pyogenes
Polyarthritis, carditis, subcutaneous nodules, erythema marginatu, sydenham chorea
Scarlet Fever
- Strep pyogenes
Blanching, sandpaper-like body rash
Strawberry tongue
Circumoral pallor
Erythrogenic toxin +
Strep agalactiae (Group B Strep)
- Pneumonia, meningitis, & sepsis in babies
- CAMP factor –> enlarges area of hemolysis formed by S. aureus
- Hippurate test +
- PYR+
Most common cause of neonatal meningitis
Strep agalactiae
Strep bovis
Subacute endocarditis
COLON CANCER
Enterococci
UTI, biliary tract infections, subacute endocarditis
PYR +
VRE –> nosocomial infections
Ca grow in 6.5% NaCl and bile
Bacillus anthracis
Spore-forming rod
Anthrax toxin
Polypeptide capsule (D-glutamate)
Cutaneous anthrax –> black eschar
Pulmonary anthrax –> pulmonary hemorrhage, mediastinitis, shock (WOOL, GOAT HAIR)
Edema factor –> increases cAMP –> inhibits phagocytosis
Lethal factor –> protease –> cleaves MAPK –> tissue necrosis
Bacillus cereus
Reheated rice syndrome
Spores
Cereulide (preformed toxin)
Clostridium tetani
- PUNCTURE WOUND
Tetanospasmin –> blocks release of inhibitory GABA And glycine from Renshaw cells in spinal cord –> spastic paralysis
Rx: antitoxin +/- vaccine booster, diazepam, wound debridement
Clostridium botulinum
- Adults: improper food canning (preformed toxin)
- Babies: honey (spores)
Produces heat-labile toxin (protease) that inhibits ACh release –> flaccid paralysis
Rx: antitoxin
Clostridium perfringens
- Motorcycle accidents
- Penetrating wound form military combat
Alpha toxin (lecithinase) --> myonecrosis and hemolysis Spores in undercooked food --> heat-labile enterotoxin --> food poisoning (late onset)
Clostridium difficile
- Clindamycin or ampicillin use
- PPI use
Toxin A: enterotoxin –> binds to brush border of gut
Toxin B: cytotoxin –> actin depolymerization –> cytoskeletal disruption –> diarrhea –> pseudomembranous colitis
Dx: stool toxins via PCR
Rx: metronidazole or oral vancomycin
Corynebacterium diptheriae
Exotoxin encoded by beta-prophage –> ADP-ribosylation of EF-2 –> inhibits protein synthesis
Psuedomembranous pharyngitis
Dx: metachromatic (blue and red) granules, Elek test+ (toxin)
Black colonies on cystine-tellurite agar
Diphtheria vaccine
Toxoid
IgG response against exotoxin B
Listeria monocytogenes
Pregnant women
Rocket tails - actin polymerization –> IC movement and cell-to-cell spread
Tumbling motility
Rx: ampicillin
Nocardia
Aerobe
Acid fast
Pulmonary infections (IC), cutaneous infections after trauma
Rx: sulfonamides
Actinomyces
Anaerobe Oral/facial abscess Yellow sulfur granules PID w/ IUDs Rx: penicillin
Mycobacterium tuberculosis
Caseating granulomas with central necrosis and Langerhans giant cells
Cord factor –> serpentine cord –> inhibits mac maturation, induces release of TNF-alpha
Sulfatides –> inhibit phagolysosomal fusion
Acid fast (mycolic acid)
Lowenstein Jensen medium
Mycobacterium leprae
Cool temperatures
Armadillo reservoir
Lepromatous: low cell-mediated immunity, humoral Th2 response, numerous acid fast bacilli
Tuberculoid: high cell-mediated immunity, largely Th1-type immune response, rare acid fast bacilli
Rx: dapsone, rifampin, clofazimine
Utilizes maltose
N. meningitidis
Doesn’t utilize maltose
N. gonorrhoeae
Moraxella
Grows in 42 C
Campylobacter jejuni
Grows in alkaline media
Vibrio cholerae
Produces urease
H. pylori
Fast lactose fermenter
Klebsiella
E. coli
Enterobacter
Slow lactose fermenter
Citrobacter
Serratia
H2S production on TSI agar
Salmonella
Proteus
Neisseria
VPN agar (Thayer Martin)
Metabolize glucose
Produce IgA protease
Gonococci: IC (within neutrophils), no vaccine (Ag variation of pilus), Fitz-Hugh-Curtis Syndrome
Meningococci: polysaccharide capsule, maltose fermenter, vaccine, Waterhouse-Friderichsen syndrome
Haemophilus influenze
IgA protease
Chocolate agar - V (NAD+), X (hematin)
Most common cause of mucosal infections (otitis media, conjunctivitis, bronchitis)
Nontypeable (unencapsulated) H. flu
Cause of epiglottitis
- drooling, inspiratory stridor
H. flu
Hib vaccine
Type b capsular polysaccharide + PRP conjugated to diptheria toxoid
- Given between 2 and 18 mo
Bordatella pertussis
Pertussis toxin (disables Gi)
Tracheal cytotoxin (cleaves cilia epi of resp tract)
Whooping cough
Vaccine (Tdap, DTap)
Lymphocytic infiltrate from immune resopnse
Legionella pneumophila
Gram stains poorly - use silver stain Charcoal yeast extract medium with iron and cysteine Dx: Ag in urine HYPONATREMIA Water sources (AC) Pneumonia + diarrhea + hyponatremia
Legionnaires’ Disease
- Legionella pneumophila
Sever pneumonia, fever, GI, and CNS sx
Smokers, chronic lung DZ
Pontiac Fever
- Legionella pneumophila
Mild flu-like syndrome
Pseudomonas aeruginosa
Non-lactose fermenting Pyocyanin (blue-green) Grape-like odor Endotoxin (fever, shock) Exotoxin A (inactivates EF-2) Phospholipase C (degrades cell membranes) Pyocanin (generates ROS) Mucoid polysaccharide capsule --> biofilm formation
Malignant otitis externa
Pseudomonas
Can spread to mastoid, temporal bones
Increased risk in elderly, IC, DM
Ostemyelitis in diabetics and IV drug users
Pseudomonas
Most common cause of respiratory failure in CF patients
Pseudomonas
Mucoid polysaccharide capsule –> biofilm formation
Burn patients
Pseudomonas
Hot tub folliculitis
Pseudomonas
Ecythema gangrenosum
Pseudomonas
Rapidly progressive necrotic cutaneous lesion
Seen in IC
Proteus mirabilis
Swarming motility
Urease + –> staghorn struvite stones
Fish odor
Helicobacter pylori
Flagellated
Catalase +, oxidase +, urease +
Dx: urea breath test, fecal antigen test
Produces ammonia –> alkaline environment
Colonizes stomach antrum
Risk of gastric adenocarcinoma and MALT lymphoma
Leptospira interrogans
Spirochete
Water contaminated with animal urine
Leptospirosis
- Leptospira interrogans
Flue-like sx, myalgias (CALVES), jaundice, photphobia with conjunctival suffusion (erythema w/o exudate)
Surfers and in tropics (Hawaii)
Weil Disease (Icterohemorrhagic Leptospirosis) - Leptospira interrogans
severe form with jaundice and azotemia from liver and kidney dysfunction, fever, hemorrhage, anemia
Borrelia burdorferi
Lyme DZ Vector: Ixodes deer tick Reservoir: mouse NE US Erythema migrans AV block Bells palsy Encephalopathy Chronic arthritis
Treponema pallidum
Painless chancre Dark field microscopy VDRL + Maculpapular rash on palms and soles Condyloma lata VDRL/RPR+, confirm with FTA-ABS Gummas Aortitis (vasa vasorum destruction) Neurosyphilis (tabes dorsalis) Argyll Robertson pupil Broad-based ataxia, + Romberg, Charcot joints
Congenital Syphilis
rhagades, snuffles, saddle nose, notched teeth, mulberry molars, short maxilla, saber shins, CNIII deafness
VDRL false positives
Viral infection
Drugs
Rheumatic fever
Lupus and leprosy
Anaplasma spp.
Anaplasmosis Ixodes tick (live on deer and mice)
Bartonella spp.
Immunocompetent –> Cat scratch DZ –> fever, LAD (stellate granulomas w/ central necrosis)
IC –> bacillary angiomatosis –> raised red vascular lesions
Borrelia recurrentis
Relapsing fever
Louse (variable surface Ag)
Brucella spp.
Brucellosis undulant fever –> organomegaly, osteomyelitis
Unpasteurized dairy, vets, ranchers, slaughter houses
Campylobacter
Bloody diarrhea
Feces from infected pets/animals, contaminated meats/foods/hands
Chlamydiophila psittaci
Psittacosis
Parrots, other birds
Coxiella burnetii
Q fever (no rash) Aerosols of cattle/sheep amniotic fluid
Eherlichia chaffeensis
Ehrlichiosis
Amblyomma (Lone Star tick)
Francisella tularensis
Tularemia
Rabbits, ticks, deer flies
Type IV HSN
Pasteurella multocida
Cellulitis, osteomyelitis
Animal bite, cats, dogs
Mouse like odor