microbio lab quiz 2

respiratory tract normal flora/biota

• Viridans (alpha) Strep

• Coagulase (-) staphylococcus

• Non-pathogenic Neisseria

• Haemophilus

• Corynebacterium

• Some gram-negative rods

• Some yeast

urogenitary tract normal flora/biota

• Lactobacillus

• Alpha strep

• Coagulase Negative Staphylococcus

• Corynebacterium

• Some gram negative rods

skin normal flora/biota

• Coagulase Negative Staphylococcus (may be a potential pathogen; w/ endocarditis)

• Alpha strep

• Corynebacterium

• Some gram negative rods depending on quantity, patient clinical condition, and diagnosis

stool normal flora/biota

• Many gram negative rods

• Possible C diff if patient is NOT exhibiting symptoms

respiratory tract possible pathogens

• Strep pneumonia

• Group A Strep

• Haemophilus Infuenzae

• Pseudomonas aeruginosa

• Klebsiella pneumoniae

• Staphylococcus aureus

• Other gram negative rods

urogenitary tract possible pathogens

• Escherichia coli

• Pseudomonas aeruginosa

• Klebsiella pneumoniae

• Staphylococcus aureus

• Enterococcus

• Other gram negative rods

skin-wound, tissue, misc., body fluids/sites pathogens

• Staphylococcus aureus

• Beta-Hemolytic Streptococcus

• Gram negative rods (i.e. E. coli, Pseudomonas aeruginosa, Klebsiella, etc…)

nasal swabs

often used for infection control purposes; isolate MRSA/MSSA

SELECTIVE: 7.5% NaCl; allows Staphylococcus

DIFFERENTIAL: mannitol + pH indicator (phenol red); fermenter = yellow, non = pink

USE: select for Staphylococcus; yellow = aureus

Staphylococcus aureus tests

HEMOLYSIS: beta

STAIN: Gram-pos. (+) cocci clusters

CATALASE: positive (bubbling)

COAGULASE: positive (clumping)

MRSA/MSSA: large zone = MSSA, small/no zone = MRSA

throat swab

tests for Streptococcus (pyogenes) species, group A; no cough

IMPORTANT: sterile swab tonsils + posterior pharynx

incubate in CO2, 35-37 C

Streptococcus pyogenes tests

HEMOLYSIS: beta

STAIN: Gram-pos. (+) cocci chains

CATALASE: negative (no bubbling)

COAGULASE: negative (no clumping)

BACITRACIN: yes zone = positive (sensitive), no zone = other species

sputum sample

tests for Streptococcus pneumoniae

IMPORTANT: deep cough, NOT SALIVA; sterile container

incubate in 5% CO2, 35-37 C

Streptococcus pneumonia tests

HEMOLYSIS: alpha

STAIN: Gram-pos. (+) diplocci

CATALASE: negative (no bubbling)

OPTOCHIN: clear zone = positive (sensitive), no zone = viridians

urinary tract infection

commonly caused by Escherichia coli; also Proteus mirabilis AND Klebsiella pneumoniae

all 3 stain Gram-neg. (-) rods/bacilli

Escherichia coli morphology

BAP: large, gray smooth colonies; beta-hemolysis

MAC: pink colonies (lactose fermenter)

INDOLE: positive (blue-green)

Proteus mirabilis morphology

BAP: swarming growth (waves)

MAC: clear colonies (non-fermenter of lactose)

INDOLE: negative (no color change)

Klebsiella pneumoniae morphology

BAP: large, mucoid/sticky/capsule

MAC: pink, mucoid colonies (lactose fermenter)

INDOLE: negative (no color change)

urine sample plating

plated on BAP/MAC to differentiate Gram-neg. (-), grows wide range of bacteria

QUANTITATIVE streak; allows colony count for infection severity

blood agar plate (BAP)

TYPE: differential

DIFFERENTIAL: contains RBCs, differentiates based on hemolysis (beta, alpha, non)

MacConkey agar plate (MAC)

TYPE: differential AND selective

DIFFERENTIAL: contains lactose + neutral red indicator; lactose fermenter = pink, non = colorless

SELECTIVE: contains bile salts + crystal violet; inhibits Gram-pos. (+) bacteria

oxidase test

positive = purple color, negative = no color change

POSITIVE: QC = Pseudomonas aeruginosa

NEGATIVE: QC = Escherichia coli

spot indole test

positive = blue-green, negative = no color change

POSITIVE: QC = Escherichia coli

NEGATIVE: QC = Klebsiella pneumoniae

beta-hemolysis

complete clearing/(lysis) around colony

may look like a clear “halo”/zone around isolate

alpha-hemolysis

partial lysis around the colony

appears greenish/brownish zone around the isolate

non-hemolytic

no lysis around (or under) colony

no change in color/appearance of agar

fermentation

MAC (lactose): pink = yes, no color change = no

MSA (mannitol): yellow = yes, no color change (pink) = no

catalase test

POSITIVE: bubbling; QC = Staphylococcus aureus

NEGATIVE: no bubbling; QC = Streptococcus pyogenes

slide coagulase test

POSITIVE: clumping; QC = Staphylococcus aureus

NEGATIVE: no clumping; QC = Staphylococcus epidermis

rapid group A strep test

positive = 2 pink lines in test and control (A antigen present)

negative = 1 pink line in control (no A antigen present)

bacitracin disk test

SENSITIVE: zone (Group A Strep); QC = Streptococcus pyogenes

RESISTANT: no zone (not Group A strep); QC = Streptococcus agalactiae

incubate BAP plate 24 hrs at 35C in non-CO2

optochin disk test

SENSITIVE: zone; QC = Streptococcus pneumoniae

RESISTANT: no zone; QC = Streptococcus viridans

incubate 24-48 hrs at 35C in CO2

urine sample tests

healthy urine should have none, pH = 6.5

• color

• appearance

• glucose

• bilirubin

• ketone

• specific gravity

• blood

• pH

• protein

• urobilinogen

• nitrite

• leukocytes

cefoxitin test

determines if Staphylococcus aureus is methicillin sensitive or resistant

MRSA: resistant; QC = zone <= 19mm

MSSA: sensitive; QC = zone > 20mm

3 way streak, incubate overnight at 35C in non-CO2