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First step for unknown identification
obtain a pure culture
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Second step for unknown identification
gram stain
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Info you get from a gram stain (3)
Gram reaction, cell shape, cell arrangement
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why must cells be in log phase for gram staining?
old cultures of gram positive bacteria may appear as gram negative because there is not enough nutrients left after log phase and they can't retain crystal violet
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What 4 genus can fix nitrogen?
Rhizobium, azobacter, cyanobacter, clostridium
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Symbiosis
living together
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Commensalism
the microbe benefits but the host is unaffected
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Mutualism
both organisms benefit
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Parasitism
microorganism benefits and the host suffers
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nitrogen fixation
conversion of atmospheric nitrogen into usable compounds
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Plants that nitrogen fix
leguminous (pea, bean, soybean, alfalfa, clover)
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Bacteria that nitrogen fix
rhizombium and bradyrhizobium (G - rods)
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Staphylocoocus feed on
saprophyte and parasite of the skin and mucus membrane
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Staphylococcus gram
positive cocci in clusters (grapes)
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Staphyloccocus morphology
medium sized, off white to yellow-orange colonies
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staphylococcus oxygen requirement
facultative anaerobe
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Staphylococcus NaCl
tolerant
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Do staph produce catalase
yes
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Pathogenic staph
staph aureus
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Staph aureus
Wound infections, pnemonia, toxic shock syndrome, food poisoning
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Non pathogenic staph
staph epidermidis and staph saprophyticus
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Staph epidermidis
nosocomial infections
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Staph saprophyticus
Urinary Tract Infections
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Do pathagenic or non pathegenic staph produce coagulase?
pathogenic
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Coagulase
clots blood plasma to get past the hosts defense
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Streptococci food
saprophytes and parasites
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Strep gram
Gram + cocci in chains or pairs
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Strep oxygen requirement
facultative anaerobe
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Strep fermentation
lactose fermenters
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Strep morphology
small, white, drop-like, mucoid, unpigmented colonies
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Does strep produce catalase?
no
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does Strep have salt tolerance?
no
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Hemolysins
extracellular enzymes that lys RBC
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Alpha hemolysins
partially lyse RBC and reduce hemoglobin to methemoglobin
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Beta hemolysins
completley lyse RBC
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Gamma hemolysins
no lysis
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Does pathogenic or non-pathogenic staph produce hemolysins?
pathogenic
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Group A Strep example
S. pyogenes
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S. Pyogenes disease
Strep throat
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Group A strep hemolysis
beta
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Group B strep example
S. agalactiae
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S. Agalactiae diseases
impetigo, acute endocarditis, meningitis
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Group B strep hemolysis
beta
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Group C strep diseases
less serious
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Group C strep hemolysis
Beta
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Group D strep
enterococci
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Group D strep hemolysis
Beta-- may also be alpha or gamma
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Group D strep diseases
endocarditis, meningitis, UTI
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Viridians hemolysis
alpha
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viridians disease
opportunistic
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Pneumococci hemolysis
alpha
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pneumococci diseases
pneumonia
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Staph tests
Mannitol Sugar Agar (MSA), Coagulase test, Novobiocin test
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Strep Tests
Hemolytic, Bile solubility, antibiotic susceptability, CAMP, Bile- esculin hydrolysis, NaCl tolerance
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Mannitol Salt Agar Test
selects for staph due to high salt concentration and indicates mannitol fermentation by color change to yello
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Coagulase Test
detects enzyme coagulase which converts fibrinogin to fibrin forming a clot. if a clot is formed, coagulase is present and the staph is pathogenic
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Novobiocin sensitivity test
determines between non-pathogenic staph; s. epidermidis is resistant to novobiocin and will continue to grow in its presence
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Hemolytic Test
determines hemolysis of Strep
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Bile Solubility Test
Bile Salts lyse only strep pneumoniae; if the unknown is lysed then it is pneumonia
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Antibiotic Susceptibility Tests
determines resistance to antibiotics to determine between groups of strep
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Group A strep are sensitive to___
Bacitracin
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Strep Pneumonia are sensitive to___
Optochin
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Group C strep are sensitive to___
SXT
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Bile-esculin hyrdolysis Test
Group D strep hydrolyzes bile esculin into esculetin and glucose; esculetin is detected by adding ferric citrate
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NaCl Test
Group D strep are salt resistant and will grow in NaCl broth making it turbid
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