LAB Flashcards
Staphylococcus
gram stain/shape:
in clinical specimens generally appear:
catalase:
stain shape: GPC
in clinical specimens generally appear: in clusters (or short chains, pairs and singles)
catalase: positive
the most useful way of distinguishing S. aureus from other Staph?
coagulase positive test (after the catalase test distinguishes it from other GPC)
Coagulase negative Staph
S. saprophyticus and S. epidermidis
S. aureus cases what clinical manifestations
skin abcesses to pneumonia and endocarditis
S. epidermidis is often caused by
a cause of baceremia in neutrophenic patients relating to indwelling catheters, shunts and prosthetic devices
a common cause of UTIs in young, sexually active women?
S. saprophyticus
how do you distinguish between S. saprophyticus and S. epidermitis (both GPC, Cat +, coag negative)
Novobiocin:
S. epidermidis is “Se”nsitive
S. Saprophyticis is resistant
Micrococcus
species closely related to Staph that at cat + and coag neg. they are rarely pathogenic, but like S. epidermidis they can infect prosthetic hardware/be difficult to treat in this setting
All Strep and Enteroccoci are
Gram stain:
catalase:
in clinical specimens and fluid culture they grow in:
GPC
cat neg
grow in straps or pairs
S. pneumoniae (pneumococcus) is a frequent cause of:
pneumonia, meningitis and sepsis
S pyogenes, group A strep, is a frequent cause of
pharyngitis, cellulitis, and rheumatic fever
S. agalactiae (grp B strep) is a common cause of
neonatal meningitis
Enteroccoci are normally found in the
colon
unlike Strep, Enterococci can grow in…
hile bile, high salt envts (strep only grows in high bile envt)
Enterococcal infections are often associated with
UTIs and GI disorders
Haemophilus
size:
Gram stain/shape:
Haemophilus
size: small
Gram stain/shape: pleomorthic gram-neg rods
how can you distinguish between different Haemophilus species?
the nutrient growth factors required for them to grow
X factor
hemin- comes from blood or its constituents and it’s presence is required for the growth of some Haemophilus and not others
V factor
NAD- comes from blood or its constituents and it’s presence is required for the growth of some Haemophilus and not others
does H influenzae, the most common Haemophilus pathogen, require factor V, factor X or both for growth? what about the often isolated, but rarely pathogenic H. Parainfluenzae?
H. Influenzae: Both
H. Parainfluenzae: requires only V
Neisseria
Gram/shape:
aerobic/anaerobic/other:
oxidase:
Gram/shape: Gram neg diplococci
aerobic/anaerobic/other: strict aerobes
oxidase: positive
Nisseria species most difficult to grow. Why?
N. Gonorrhoea, because it thrives in a limited T range and needs ample moisture, CO2 and rich non-acidic medium
N mengitidis requires what to grow:
rich media and extra CO2
Moraxella:
Gram/shape:
like Nisserai, they’re:
Gram/shape: Gram neg diplococci
aerobic/anaerobic/other: strict aerobes
oxidase: positive
Moraxella Catarrhalis, once considered a nonpathogenic Neisseria and a part of normal mouth flora, now appears to be an occasional cause of:
sinusitis and other serious disease
how are Neisseria and Moraxella distinguished given that they’re both gram neg diploccoci, strict aerobes that are oxidase positive?
sugar fermentation tests
Bacitracin is used to distinguish between what and what?
Beta-hemolytic Strep (Group A vs Group B) B-Bras Bacitracin B-strep (agalaciae) Resistant A-strep (pyogenes) Sensitive
most bacteria that can grow aerobically and have a high O2 tolerance posses what in contrast to streptococci or enterococci which are facultative anaerobes that are incapable of using oxygen metabolically
catalase- a heme enzyme that decomposes hydrogen peroxide into H2O and O2
S. aureus colonies are the only Staph that usually look…
yellow or beige (as the name aureus implies)
How do these look different on an blood agar
Alpha-hemolysis:
beta hemolysis:
Gamma-hemolysis
Alpha-hemolysis: green
beta hemolysis: clear
Gamma-hemolysis: the absence of any rxn on blood cells in the agar
Optochin test
differentiates between S. pneumoniae (susceptible) from other alpha-hemolytic strep (resistant)
oxidase test
put test species on a piece of bibulous paper, add a few drops of oxidase reagens, if the culture is oxidase positive, the dye will be oxidized and the colonies will turn pink to red to black
Cystein tryptic agar (CTA) differentiates between Nisseria and Moraxella by
because it shows if you can produce acid from metabolizing glucose, maltose, sucrose and lactose. acid production is indicated by the presence of yellow
S. aureus: cellular morphology: colonial morphology: hemolytic rxn: catalase: identifying tests:
S. aureus: cellular morphology: GPC in clusters colonial morphology: creamy to yellow hemolytic rxn: Beta catalase: + identifying tests: coagulase
S. epidermidis cellular morphology: colonial morphology: hemolytic rxn: catalase: identifying tests:
cellular morphology: GPC in clusters colonial morphology: white hemolytic rxn: none catalase: + identifying tests: coag neg, novobiocin sensitive
S. saprophyticus cellular morphology: colonial morphology: hemolytic rxn: catalase: identifying tests:
cellular morphology: white to yellow colonial morphology: white to yellow hemolytic rxn: none catalase: + identifying tests: coag neg, novobiacin resistant
S. pyogenes (Group A) cellular morphology: colonial morphology: hemolytic rxn: catalase: identifying tests:
cellular morphology: gram + cocci in chains
colonial morphology: grayish to white translucent
hemolytic rxn: Beta
catalase: negative
identifying tests: bacitracin sensitive
Group B strep (agalactiae) cellular morphology: colonial morphology: hemolytic rxn: catalase: identifying tests:
cellular morphology: gram + cocci in chains
colonial morphology: grayish to white translucent
hemolytic rxn: Beta
catalase: negative
identifying tests: bacitracin resistant
S. pneumoniae cellular morphology: colonial morphology: hemolytic rxn: catalase: identifying tests:
S. pneumoniae
cellular morphology: gram + cocci in pairs
colonial morphology: grayish to white translucent
hemolytic rxn: alpha
catalase: negative
identifying tests: optochin sensitive (unlike all the other alpha hemolytic or viridans grp)
Non-hemolytic Strep and Enterococcus cellular morphology: colonial morphology: hemolytic rxn: catalase: identifying tests:
cellular morphology: gram + cocci in chains
colonial morphology: grayish to white translucent
hemolytic rxn: non-hemolytic (gamma)
catalase: negative
identifying tests: bile esculin (+ for gamma strep and enterococcus) and high NaCL (positive growth for enterococcus but not group d strep)
H influenzae cellular morphology: colonial morphology: hemolytic rxn: catalase: identifying tests:
H influenzae
cellular morphology: gram + coccobaccili, pleomorphic
colonial morphology: gray, translucent, small
hemolytic rxn: gamma
identifying tests: factor X (hemin) +, Factor V (NAD) +
H. haemolyticus cellular morphology: colonial morphology: hemolytic rxn: catalase: identifying tests:
H. haemolyticus
cellular morphology: gram + coccobaccili, pleomorphic
colonial morphology: gray, translucent, small
hemolytic rxn: beta
identifying tests: factor X (hemin) +, Factor V (NAD) +
H. parainfluenzae cellular morphology: colonial morphology: hemolytic rxn: catalase: identifying tests:
cellular morphology: gram + coccobaccili, pleomorphic
colonial morphology: gray, translucent, small
hemolytic rxn: gamma
identifying tests: factor X (hemin) -, Factor V (NAD) +
what is the cause?
5 yo w/sore hroat, fever, swollen glands. Redness, edema and grayish white exudate
culture: GPC, beta hemolytic, bacitran sensitive
Grp A strep (pyogenes), which can also cause cellulitis and necrotizing fasciitis
what is the cause:
elderly (79 yo) woman w/ chest pain, difficulty breathing, cough and fever
sputum culture: GPC in pairs, alpha hemolysis, optichin sensitive
S. pneumoniae
what is the cause:
hospitalized pt with urinary catheter dvps a UTI
urine culture: GPC in chains, cat neg, bile +, NaCL +
Enterococcus
what is the cause:
2 days post surgery, pt notices area around incision = red and swollen and extremely painful
culture cloudy fluid from wound: GPC in clusters, cat +, coag +
S aureus– common on skin and gets in via an encision
what is the cause:
hospitalized pt with an IV catheter dvps a fever. Skin arnd IV entry site is red and swollen
culture from the tip of the catheter: GPC, cat +, coag -, novobiocin -
S. epidermidis– grows on biofilms on plastics
what is the cause:
young, sexually active woman dvps abdo pain/dysuria (pain upon peeing)
urine culture: GPC, cat +, coag -, novobiocin resistant
S. saprophyticus
what is the cause:
23 yo mas with dysuria and urethral discharge
discharge = cultured: gram neg diplococci, doesn’t ferment maltose, oxidase +
N. gonnhorhea– diplococci (“the clap”)
what is the cause:
55 yo w/hist of rheumatic fever who presents with fever, malaise and splinter hemorrhage (sign of endocarditis)
culture: GPC, y-hemolytic, bile +, NaCl -
Grp D. strep
what is the cause:
a bad sinus infection sends an 18 yo pt to doctor
culture: GP coccobacilli, gray, translucent, small culture, gamma hemolytic, required factor V and X
H. influenzae
HMS student- upper respiratory infection
culture: Gram neg, no growth on blood agar, growth on chocolate agar, small gray and translucent, grows around factor V
H. parainfluenzae
N gonorrhea is gram neg. diplococci, looks gray, white or yellowish, is y-hemolytic, is oxidase negative and metabolizes which sugars?
just glucose
N meningitidis is gram neg. diplococci, looks gray, white or yellowish, is y-hemolytic, is oxidase negative and metabolizes which sugars?
glucose and maltose
Moraxella is gram neg. diplococci, looks gray, white or yellowish, is y-hemolytic, is oxidase negative and metabolizes which sugars?
NONE!
