Lab Quiz 5

difference between Staphylococcus and Streptococcus: Shape

• Staphylococcus & streptococcus: cocci

difference between Staphylococcus and Streptococcus: ram reaction

• Staphylococcus & streptococcus: gram +

difference between Staphylococcus and Streptococcus: arrangement

• Staphylococcus: clusters

• Streptococcus: chains

difference between Staphylococcus and Streptococcus: where found in the body

• Staphylococcus: skin, nasal passage

• Streptococcus: mouth, throat, GI tract, vaginal area

difference between Staphylococcus and Streptococcus: catalase reaction

• Staphylococcus: + (lives on skin)

• Streptococcus: - (aerotolerant anaerobe)

difference between Staphylococcus and Streptococcus: reaction to cold or dryness

• Staphylococcus: not sensitive/resistant

• Streptococcus: sensitive

difference between Staphylococcus and Streptococcus: salt tolerance

• Staphylococcus: osmotolerant

• Streptococcus: not osmotolerant

difference between S. epidermidis and S. aureus (staphylococcus): % of humans that carry it

• S. epidermidis: 100% carries it

• S. aureus: 25-20% (50% for healthcare workers)

difference between S. epidermidis and S. aureus (staphylococcus): pathogenicity

• S. epidermidis: no

• S. aureus: can be pathogenic

difference between S. epidermidis and S. aureus (staphylococcus): normal flora

• S. epidermidis: yes

• S. aureus: can be or 2/3 of people carry sometimes

difference between S. epidermidis and S. aureus (staphylococcus): fermenter of mannitol (sugar)

• S. epidermidis: no

• S. aureus: no

difference between S. epidermidis and S. aureus (staphylococcus): coagulase reaction

• S. epidermidis: -

• S. aureus: +

virulence factors of s. aureus

1. coagulase

2. beta-hemolysin

3. staphylokinase

coagulase as a virulence factor

• forms clots (97% of staph)

• helps protect the bacteria from the immune system

beta-hemolysin as a virulence factor

digests RBC and uses the contents for food and multiplies

staphylokinase as virulence factors

• dissolves clot

• helps for the spread of bacteria to neighboring tissue

Levels of staph infection

1. folliculitis

2. abscess

3. furuncle

4. carbuncle

5. systemic → sepsis

6. pneumonia

7. necrotizing fasciitis

8. common cause of food poisoning

9. toxic shock syndrome

folliculitis

pimple; infected hair follicle

abscess

localized region of pus surrounded by inflamed tissue

furuncle

boil; multiple local focal points of infection

carbuncle

subcutaneous; deep in the tissue (causes a fever)

purpose of MSA

to presumptively identify staphylococcus aureus and select for the growth of salt tolerant bacteria

beef extract, peptones in MSA

MSA: general growth

sodium chloride (7.5%) in MSA

MSA: high salt concentration → selective for osmotolerant bacteria

D-mannitol for MSA

MSA: sugar for fermentation - differential b/c S. aureus can ferment it

Phenol red in MSA

MSA

• pH indicator

• yellow = acidic

• red/pink = basic

• orange = neutral

meaning of yellow agar in MSA

• + result

• acidic pH, osmotolerant

• mannitol was fermented → possible S. aureus (confirm w. coagulase test)

• yellow colonies can be micrococcus - nonpathogenic

meaning of red or pink agar in MSA

• - result

• basic pH, osmotolerant

• mannitol was not fermented; used peptones and raise the pH

• no s, aureus, but an osmotolerant organism like s. epidermidis

meaning of no growth in MSA

• - result

• no osmotolerant

purpose of coagulase test

to test whether bacteria produce coagulase (like s. aureus - can be a confirmatory test)

substrate of coagulase test

• fibrinogen (l)

• clotting factor that is liquid and source is rabbit plasma (liquids part of blood)

various enzymes in coagulase test

coagulase (exoenzyme)

product in coagulase test

fibrin clot (s)

result of solid in coagulase test

• + result

• there is fibrin clot and confirmed for s. aureus

meaning of liquid in coagulase test

• - test

• there is no fibrin clot and s. aureus is not present

beta-hemolysis in throat culture

• complete destruction of RBCs (get clear zones around colonies)

• group A and B strep

• sensitive to bacitracin

• pathogenic and 50% are carriers

• can cause step throat and scarlet fever

• can cause flesh eating necrotizing fasciitis and form of toxic shock

alpha-hemolysis in throat culture

• partial desruction of RBCs (get green zones around colonies)

• Streptococcus pneumoniae

• sensitive to O2

gamma-hemolysis in throat culture

• no damage to RBCs (no change to agar)

• S. mutans and group D strep

purpose of throat culture

rapid test to differenciate S. aureus (catalase +) from S. pyogenes (catalase -)

group B strep: beta-hemolytic

may be found as normal flora in GI

25% females - vaginal or anal carriers

women screened 35-37 weeks prior to birth

pathogen in immunocompromised patients

50% mortality rate for newborns if not treated immediately

neonatal pathogen → pneumonia, sepsis, meningitis

group D step: gamma- hemolytic

Enterococcus faecalis

• 100% carried as normal flora

• can be outside of GI tract: sepsis and periotoneal cavity

• Vancomycin resistant enterococcus has become a major nosocomial pathogen

non-lancefield

• Streptococcus mutans (gamma-hemolysis)

• Streptococcus pneumoniae (alpha-hemolytic)

purpose of CAMP test

to identify and confirm the presence of group B strep

positive result for CAMP test

look for triangular zone of enhanced beta-hemolysis (synergistic)

purpose of bile esculin agar

to select for the growth of Enterococcus for presumptive indentification

pentones in bile esculin agar

bile esculin agar: general growth

oxgall (bile slats) in bile esculin agar

bile esculin agar: inhibit gram +, except enterococcus (selective)

sodium azide in bile esculin agar

bile esculin agar: inhibit gram - (selective)

esculin in bile esculin agar

bile esculin agar: special food source that contains glucose → E. faecalis can metabolize it (differential)

ferric citrate inbile esculin agar

bile esculin agar: turn brown with esuletin (product of esuclin metabolism); regent already in media

positive result in bile esculin agar

dark brown color = esculin digested

negative result in bile esculin agar

no brown color = esculin not digested

chart of species of Streptococcus

species of Streptococcus: streptococcus pneumoniae

• alpha hemolysis (green)

• non-lancefield

• optochin sensitivity

species of Streptococcus: streptococcus pyogenes

• beta-hemolysis (yellow)

• group A strep

• bacitracin sensitivity

species of Streptococcus streptococcus algalactiae

• beta-hemolysis (yellow)

• group B strep

• CAMP positive

species of Streptococcus: enterococcus faecalis

• gamma-hemolysis (red)

• group D strep

• bile esculin positive

species of Streptococcus: streptococcus mutans

• gamma-hemolysis (red)

• non-lancefield

• negative for all tests

purpose of plaque assay of viral titre

to determine the titer (PFU/mL) of the original phage stock solution

clear zone in plaque assay of viral titre

area of cell death known as a plaque b/c virus killed the bacteria

calculations for serial dilution

1. add 0.1 mL stock to 9.9 mL water to get 10

2. use formula stock culture/total fluid → 0.1 mL/10 mL

3. rearrange to scientific notation → 10^-2

4. for next dilution, 10^-2 × 10^-2 = 10^4 (when multiplying exponents, you add them together)

5. continue until plates are complete

PFU

plaque forming unit (the number of clear zones that developed on the plate

Titer

PFU/Final Dilution Factor (FDF)

Plaque assay

can be used to enumerate viruses that lyse their host cells. The host cells and virus are incubated together for a short time to allow the virus to attach to and enter the host cell. Then the mixture in plated within a semi-solid agar plate.

general characteristics of fungi

• eukaryotic (have a nucleus) with chitin in cell walls

• heterotrophic

• nonphotosynthesis

• unicellular or multi cellular

• reproduce by asexual or sexual spores and prefer moist, slightly acidic environments

What are two general categories of fungi

1. yeast

2. molds

mycology

study of fungi

yeast

unicellular, round/oval, reproduce by budding/fission, and form smooth, creamy colonies

molds

multicellular, composed of hyphae (filaments) forming a mycelium, and reproduce using spores.

candida albicans

• medically important yeast

• causes yeast infection = candidiasis

• vaginal area, mouth (causes thrush)

• normally comes and goes

• systemic in blood may result in endocarditis (may live 3-4 days)

• antifungles usually work (nystatin)

• most susceptible to Candida infections: diabetics, those w/ immunodeficiency, catheterized patients, infants, individuals taking antimicrobial medications

saccharomyces cerevisiae

• important non-pathogenic yeast

• name means “sugar fungus that makes beer”

• brewers yeast - used to produce beer, wine, and bread

• fermentation produces CO2 gas and ethanol (alcohol)

rhizopus stolonifer

• black bread mold

• hyphae are coenocytic (multinucleated cells)

• reproduce asexually (sporangiospore) or sexually (zygospore)

penicillium notatum

• medically important mold

• spores are green and hyphae are white

• can cause a lung infection in immunocompromised patients

• some strains are used to make blue cheese and brie cheese

aspergillius niger

• medically important black mold

• black spores on top, yellow hyphae on bottom

• names b/c it was thought to resemble an aspergillum which is a holy water sprinkler in the catholic church

• most common mold (in wall sometimes)

• causes lung infection - aspergillosis. Can cough up fungal balls which are not contagious

• other species can be used to make soy sauce and soy paste

PFU

plaque forming unit (the number of clear zones that develop on the plate

Titer

PFU/Final Dilution Factor (FDF)

calculating titer example

yeast simple stain of wet mouth of S. Cerevisiae

wet mount of S. Cerevisiae

Rhizopus stolonifer: reproduce asexually

sporangiospore

Rhizopus stolonifer: reproduce sexually

zygospore

Penicillium notatum: reproduce asexually

conidiospores

conidiophore

(in certain penicillum notatum & Aspergillus niger) a conidium-bearing hypha or filament.

septae hyphae v. aseptae hyphae

• septae = fungal filaments (hyphae) that are divided into individual cells by cross-walls called septa

• aseptae = fungal filaments that lack internal cross-walls (septa), resulting in a continuous, multinucleated (coenocytic) cytoplasm within the tube-like structure

coenocytic

multinucleated cells

rhizopus stolonifer plate

rhizopus slide culture

rhizopus stolonifer (sporangiophores)

rhizopus stolonifer (zygospores)

aspergillus niger plate

aspergillus niger - side culture

aspergillus niger - condiospores

penicillum notatum plate

penicillium - side culture

penicillum - condiospores