Microbiology Lab – Midterm – Flashcards

Streptococcus pneumoniae

- alpha hemolysis

- Optochin susceptible

- aerotolerant anaerobes / obligate fermenters / some capnophiles (CO2)

- prefer BA plate

Corynebacterium diphtheria

(w/ L. monocytogenes)

- can show BETA hemolysis (we didn't see any)

- on Tellurite, black growth

- facultative anaerobes

- slow growth (except on Loeffler's slant)

Haemophilus influenzae

- requires X factor (heme) and V factor (NAD)

- therefore they must grow on CA or around Staph colonies

H. parainfluenzae

- requires V factor only, so will grow around V strips all the way

- can look a lot like H. influenzae

- facultative anaerobes

Listeria monocytogenes

- can show soft beta hemolysis (we didn't see)

- growth on tellurite is grey-black

- facultative anaerobe

Staphylococcus aureus w/S. epidermis

- S. aureus: beta hemolysis, larger

- S. epidermis: no hemolysis, small

- facultative anaerobes

- hardy, salt-tolerant and drying-tolerant

Staph. saprophyticus

- no hemolysis

- facultative anaerobe

Strep pyogenes (Grp A)

- beta hemolysis 100% when anaerobic incubation

- aerotolerant anaerobe

- prefers BA plate

Strep. agalactiae (Grp B)

- beta hemolysis

- aerotolerant anaerobe

- used to visualize mycobacteria, which have high MW lipid cell walls that repel gram staining, and are slow-growing

- mycobacteria show up as beaded, slender, pink rods, usually stuck together in clumps

- used to differentiate S. saprophyticus from S. aureus and S. epidermis

- S. saprophyticus is the only one of these that is RESISTANT

- used to differentiate S. aureus from S. epidermis and

S. saprophyticus

- S. aureus is POSITIVE

- used to differentiate between GPC

- Staph is catalase POS, and

Streps are all catalase NEG

- complete lysing of RBCs

- exhibited by:

- Staph. aureus

- Strep pyogenes (A) - 100% when anaerobic incub.

- Strep agalactiae (B)

- Corynebacterium diphtheria (possible)

- Listeria monocytogenes (possible)

"Beta A DiffLisAur" (Strep B & A, Diph, List, S. aureus)

- exhibited by:

Strep pneumoniae

viridans Streptococci

Tests you could do:

- catalase? if NEG, it's a strep...

- optochin test? if susceptible, it could be pneumo, and you should do bile solubility

exhibited by:

• Staph. epidermidis, Staph. saprophyticus
• Enterococcus
• Neisserias & Moraxella (GC, MC, MX)
• C. pseudodiphtheria
• H. influenzae, H. parainfluenzae

• Staph aureus (nares)
• Staph epidermidis (skin)
• Strep pneumo (10-30% of throats)
• viridans Strep
• Enterococcus (fecal)
• N. meningitidis (3-15% of URTs)
• Moraxella catarrhalis
• diphtheroids
• L. monocytogenes (environmental & intestinal)
• H. influenzae & parainfluenzae (URT)

• Staph spp.
• C. diptheria & C. pseudo
• L. monocytogenes
• Haemophilus spp.

-Neisseria gonorrhea

-Neisseria meningitidis

• N. gonorrhea (CA, CO2)
• H. influenzae (X/V factor so CA), H. para (V only, still CA)
• N. meningitidis (BA, CO2)
• Strep Grp A, B, pneumo, viridans (BA preferred)
• Enterococcus (aerotolerant, but hardier)
• C. diphtheria (slow)
• Staph. aureus / epidermidis, Listeria monocytogenes

• Staph. saprophyticus
• Enterococcus

• Grp B Strep (neonatal)
• Strep pneumoniae
• N. meningitidis (hematogenous)
• L. monocytogenes (rare, foodborne)
• H. influenzae

Brains Have No Problem Listening!

- taken from lumbar puncture / spinal tap

potential pathogens:

• Grp B strep (neonates)
• H. influenzae (young children)
• N. meningitidis (children, young adults)
• Strep pneumoniae* (older adults)
• Listeria monocytogenes (rare)

- Staph epidermis (occasional, often a contaminant but can be acq. nosocomial)

- Grp A Strep (necrotizing fasciitis; can be w/ or w/o S. aureus in erysipelas)

- Enterococcus

LOOK FOR:

- Strep. pneumoniae

- Staph aureus (tho could be normal microbiota)

- H. influenzae(tho could be normal microbiota)

Contaminants from mouth if improper collection:

- Neisseria

- viridans Strep

- viridans Streptococci are RESISTANT

- typical fecal microbiota

- they're aerotolerant anaerobes, but hardier

- can cause wound infx, sometimes UTI

- no hemolysis

- Catalase NEG (maybe pseudo)

- Bile Esculin POS (black on slant)

- NaCl 6.5% POS (color chg)

 can confirm

- Catalase NEG

- alpha hemolytic, very tiny colonies

- Optochin resistant

- Bile Solubility - NEG

confirms it

- Pneumonia* also Meningitis

- colonies have mucoid appearance, small, white, alpha hemolytic

- Catalase NEG

- Optochin susceptible

- to confirm do:

- used to differentiate Strep pneumo from other alpha-hemolytic Strep

- put a drop of sodium deoxycholate onto isolated colonies on a plate, and incubate 15 mins.

- differentiates Grp B Strep from other Strep spp.

- positive test indicated by deep purple color after incubation and addition of ninhydrin reagent

- Grp B Strep is Sodium Hippurate POS

- beta-hemolytic, colonies have slight orange pigmentation, small, creamy

- Catalase NEG

- Bacitracin RESISTANT

- Sodium Hippurate Hydrolysis - POS (purple)

(B is more HIP than A)

- toxins!!!

- white colonies, remain intact when pushed w/loop

- Catalase NEG

- beta hemolysis

- Bacitracin susceptible

-The Neisserias

- M. catarrhalis

- tests for activity of cytochrome c oxidase (part of ETC of some bacteria)

- moisten filter paper with oxidase reagent, transfer test colony to paper and POS result is purple color change

- SELECTIVE media containing Abx that inhibit growth of organisms that might outcompete N. gonorrhea (it's a slow grower)

- C = colistimethate (for G-)

- N = nystatin (for yeasts)

- N. gonorrhoeae

- H. influenzae
(H. flu will also grow in satellite colonies around Staph)

CTA slants (Cystine Trypticase soy agar)

- used to differentiate between N. gonorrhoeae,

N. meningitidis, and M. catarrhalis

- you'd use it if you had Oxidase POS organisms & you want to narrow it down

- color change from pink to yellow if positive

- Glu - GC & MC, but not MX

- Mal - MC only

- Lac - neither

- Suc - neither

- growth on NA, without CO2 incr

- sugar degradation test - NEG for all

- GC, MC and MX are all oxidase POS

- ALPHA hemolysis

- bile SOLUBLE

- optochin SUSCEPTIBLE

Urease Test

- L to R: POS, NEG, NEG or not inoc

- tests for organisms ability to produce urease; urease hydrolyzes urea and releases NH3, raising pH of medium

- pH raised = more alkaline = pink result (POS)

- we use to differentiate between GPRs:

- C. pseudodiphtheria is Urease POS

- C. diphtheria & L. monocytogenes are Urease NEG

Not inoculated

NG

A - C diph and L mono

AG

NC

- C. diphtheria  is (A) for Glu and Mal

- C. pseudo is (NC) for all

- L. mono is (A) for Glu and Mal

- tests an orgs ability to reduce nitrate to nitrite, NO, N2O, N2

- nitrate A/B detect nitrite

- red color change after adding reagents A/B indicates (+) result.

- If no (+) result, add zinc, which tests for remaining nitrate

- if red color change results after adding zinc, we can conclude a (-) test

- Orgs that are (+) C. diph and C. pseudo (L. mono is negative)

- spirillum volutans

- Cryptococcus (yeast)

- often nosocomial

Toxin-producing strains:

- N. meningitidis