Medical Microbio Practical 1

glucose, maltose, and lactose are examples of what medium?

C-agars

what do c-agar tests tell you?

if it can ferment that specific sugar

what is the pH indicator of c-agars?

phenol red

c-agar positive result

color change from pink to yellow ; gas bubbles

what does the nitrate broth test do?

tests if an organism can reduce NO3 to NO2 OR free N2 gas

if there is a bubble in the Durham tube of the nitrate reduction tests and the organism is not a fermenter, what does it tell you?

organism reduces nitrate to N2

what is added into the nitrate broth if there is no bubble present?

sulfanilic acid (SA) and naphthylamine solution (DMN)

what is a positive test result after adding SA and DMN to the nitrate reduction test? What does it mean?

red broth ; organism reduces nitrate into nitrite

if nothing happens after adding SA and DMN, what is added into the nitrate broth tube?

zinc

what is a positive result after adding zinc and what does it mean?

red broth; organism DOES NOT reduce nitrate.

what is a negative result after adding zinc to the nitrate broth? what does it mean?

no color change ; organism reduces nitrate into something other than nitrite.

what does the motility nitrate agar deep tell you?

motility

what is a positive result of the motility deep?

red throughout

what does the tryptone broth break down?

tryptophan into indole using tryptophanase enzyme

what is the reagent in the tryptone broth test?

kovac's reagent

what does the starch agar test tell you about the organism?

if it produces amylase

what is a positive result of the starch agar test?

clear zone in starch after adding reagent

what is the reagent in the starch test?

gram's iodine

what does the blood agar plate tell you?

if an organism can lyse red blood cells

3 hemolytic patterns of blood agar plate and what they look like

beta: complete hydrolysis; clear zone

alpha: partial hydrolysis; green-brown cloudy hydrolysis

gamma: no hydrolysis of RBC

mechanism of catalase test

H2O2 --\> 2 H2O + O2

what does the catalase test tell you?

if organism can produce catalase

reagent in catalase test

3% H2O2

positive result in catalase test

bubbles

oxidase test tests for

cytochrome oxidase

positive oxidase test

blue test strip within seconds

define avirulent

not pathogenic to humans

define attenuated

microbe virulence factors inactivated

define opportunistic pathogen

may cause disease in immunocompromised

Lab safety: microbe not known to cause disease in healthy adults and pose minimal risk to personnel and environment

BSL 1

examples in BSL 1

bacillus subtilis, pseudomonas aeruginosa

physical environment in BSL 1

PPE worn as needed ; doors to separate work area. from rest of facility

Lab safety: microbes pose moderate hazards to personnel and the environment

BSL 2

physical environment in BSL 2

PPE worn as needed

examples in BSL 2

streptococcus pneumonia, salmonella, MRSA

Lab safety: serious or lethal disease through RESPIRATORY transmission

BSL 3

physical environment in BSL 3

medical surveillance, lab access restricted, PPE required (may need a respirator, work in hood)

Sustained directional airflow (1 way air), self-closing and locking doors, enter through 2 sets of doors

example in BSL 3

M. tuberculosis

Lab safety: exotic organisms are found in

BSL 4

physical environment in BSL 4

specialized PPE required,

positive pressure suits or class III hood,

shower before and after working,

lab in restricted area of building or separate building

examples in BSL 4

Marburg virus, ebola

examples of conventional media

regular broth, slants, plate media

what does a conventional media do?

grows organisms indiscriminately

what does a differential media do?

allows us to see differences macroscopically, -- some organisms will now grow

example of differential media

MacConkey agar - color change around colonies

Which media is used for fastidious (stubborn) growth

enrichment media

a rapid test media is used when \___

need results sooner

benefits of rapid test media

faster and cheaper

examples of organisms grown in enrichment media

streptococcus pneumoniae, francisella, neisseria, haemophilus

uses antigens or antibodies to determine the presence of corresponding antigen or antibody

immunoassays

examples of immunoassays

ELISA, western blot

takes one strand of template DNA and utilizes the high efficiency of polymerase to synthesize limitless quantities of targeted nucleic acid sequence

PCR mechanism

how can PCR be adapted to diagnose different organisms?

change primers

staphylococcus is gram __

positive

gram positive stains

purple

staphylococcus is motile or non-motile

non-motile

staphylococcus reaction to coagulase test?

depends on the organism, can be + or -

what does staphylococcus look like on media?

clusters on media, pairs/triads in broth

what tests are used to identify staphylococcus?

coagulase test,

BAP hemolysis,

MSA (mannitol salt agar),

slide catalase test,

DNase agar,

novobiocin antibiotics

3 medical staphylococcus organisms examined in class

S. aureus, S. epidermidis, S. saprophyticus

causes food posioning, toxic shock syndrome, cellulitis, wound infections, and sepsis

S. aureus

S. aureus can be resistant. what are they called?

MRSA and VISA

what tests can be used to determine methicillin and vancomycin resistance in S. aureus?

monoclonal antibody assays, agar screening plates, nucleic acid amplification protocols

S. aureus hemolysis pattern

beta

S. aureus will have \______ on MSA plate?

yellow colonies

S. aureus coagulase test

positive

S. aureus DNase test

positive

causes endocarditis, bacteremia, UTIs, nosocomial infections

S. epidermidis

S. epidermidis hemolytic pattern

alpha

S. epidermidis coagulase test

negative

S. epidermidis on MSA plate

may appear yellow

is an oppurtunistic pathogen (UTis, wound infections, sepsis)

S. saprophyticus

S. saprophyticus hemolytic pattern

gamma

S. saprophyticus reaction to novobiocin

none. novobiocin resistant

mannitol salt agar plate is (selective/differential) media

selective and differential

what is MSA used for?

to isolate and identify S. aureus

what is MSA plate made of?

high salt content, phenol red, and mannitol

growth on MSA plate indicates

staphylococcus species

red media on MSA plate is evident of

negative for S. aureus

yellow media on MSA plate is evident of

S. aureus or S. saprophyticus

what does the coagulase test test for?

tests for presence of bound coagulase

what reagent is used in coagulase test?

rabbit plasma

how does S. aureus react to coagulase test

positive

what is a positive test in coagulase test

clumps form

what type of media is DNase agar?

differential media

what does DNase test do?

tests for ability to produce Dnase which cleaves DNA or RNA

T/F most-coagulase positive staphylococcus have positive reaction to DNase test

true

DNase test is made of what?

tryptic soy agar and DNA

Reagent in DNase test

1% toluidine blue added after incubation

positive DNase test

red-purple color

Streptococcus is gram __.

positive

Enterococcus is gram __

positive

shape of streptococcus and enterococcus

spherical or ovoid shaped

streptococcus and enterococcus have what reaction to catalase test?

negative

motility of streptococci and enterococci

non-motile

example of group A streptococcus

S. pyogenes

hemolysis of group A streptococcus is…

beta

diseases of group A streptococcus

scarlet fever and strep thorat

where do infections of group A streptococcus begin?

throat or skin

example of group B streptococcus

S. algalactiae