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M & D > Lab 1 > Flashcards

Lab 1 Flashcards

1
Q

GAS

A

Group A streptococci or streptococcus pyogenes

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2
Q

GBS

A

Group B streptococci or Streptococcus agalactiae

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3
Q

viridans streptococci

A

streptococcus species that are a- haemolytic or gama- haemolytic and cannot be categorized using lancefield antigen grouping

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4
Q

streptococcal arrangements

A

genera Enterococcus and Lactcoccus

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5
Q

gonococcus

A

Neisseria gonorrhoeae

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6
Q

meningococcus

A

Neisseria meningitidis

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7
Q

pneumococcus

A

Streptococcus pneumoniae

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8
Q

Diagnosis

A

is a conclusion or decision based on a careful examination of relevant information

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9
Q

The evaluation process of hypothesis

A

A valid hypothesis has three characteristics.

1) it is testable
2) it is unbiased
3) it is repeatable

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10
Q

What are the assumptions of CFUs

A

that each colony arises from a single living cell
(note however, two ajacent cells may clump their colonies together to apper as one.)

that all living cells will produce colonies
(note VBNC cells may exist)

thatthat all cells within a colony are genetically identical to each other and to the original single cells

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11
Q

Selective Media

A

inhibits the growth of some groups of organims from growing while allowing others groups to grow

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12
Q

Differential Media

A

can distinguich between different types of bacteria based on biochemical changes in the media after inoculationa nd incubation

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13
Q

differential and selective properties of Manitol Salt Agar

A

selects for halophiles and inhibits non-halophiles.

Of the salt tolerant organisms that grow, the medium differentiates those that caan ferment the carbohydrate mannitol from those that cannot ferment mannitol

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14
Q

Purpose of a four quadrent streak plate

A

isolate CFUs by streaking different cell densities (decreasing) across each quatrent of an agar plate

Often selective media is used to help isolate a specifc microbe

some also can tell the difference between microbes are are thus selective and differential

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15
Q

Blood agar

A

differential based on haemolytic traits

TSA with %5 sheeps blood

haemolysins= haemolytic enzymes dyscolour the surrounding media from the break down of the RBCs

Haemoglobin -> metemoglobin (green and opaque)
= alpha haemolysis

complete distruction of haemoglobin (translucent yellow)
= beta haemolysis

no breakdown (agar remains the same)
=gamma haemolysis

Note: Blood agar is an enriched medium and can help to accelerate the growth of fastidious organisms

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16
Q

The Gram stain

A

primary stain = crystal violet with iodine which acts as a mordant to enhance the colour (makes a complex with CV and is harder to wash away)

decolourization with ethanol removes CV-iodine from Gram- cells (this strips away the lipids of the outer membrane which allows the CV to leak out)

secondary stain = safranin to stain G- pink

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17
Q

false negative gram stain

A

G+ is pink

because the result appers to be G- when the organism is G+ (ie a false result)

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18
Q

False positive gram stain

A

G- is purple

because the organism falsely appersa G+

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19
Q

Problems with Bacillus and Staphylococus Gram stains

A

give false negatives after 24 hrs because they lose their resistance to the decolourization step

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20
Q

Catalase test

A

During aerodic respiration, aerobic, facultative anaerobic and microaerophilic bacteria use O2 as a TEA

Some e- leak from the ETC and form superoxide and hydrogen peroxide

to combat this these organisms use superoxide dismutase and catalase hydrolaze to turn these products to oxygen and water

superoxide dismutase catalyzes the reaction of superoxide to hydrogen peroxide

The inability of anaerobes to dismantle superoxide shows us why oxygen is toxic to these organisms

Catalase + organisms will result in vigourus bubbling immediately after the addition of hydrogen peroxide

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21
Q

What is the purpose of blood agar

A

good indication of G+ cocci like Streptococcus species

and to promote the growth of fastidious organisms

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22
Q

What is the purpose of the catalase test

A

differentiate catalase positive organisms like Staphylococcus species from catalase negative Streptococcus species

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23
Q

What is the purpose of the Coagulase test

A

differentiation of Staphylococcus species.

S. aureus produces the coagulase enzyme which converts fibrinogen to fibrin

the ability for SA to trigger coagulation allows a clot to form around and protect the colony from host defenses

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24
Q

bound-coagulase

A

clumping factor

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25
Q

coagulase as a extracellular // exoenzyme

A

free coagulase // coagulase-reacting factor

26
Q

Coagulase slide test

A

only detects bound coagulase, since the one to two minutes it takes for a positive test is not sufficient for significant levels of exoenxyme to be released

27
Q

DNase Test Agar

A

tests for exoenzymes = DNase that can hydrolyze DNA into oligonucleotides

contains peptides as an energy and carbon source, DNA and toluidine blue with forms complexes with DNA but not nuclotides

+ test = plate turns from blue to clear around the colony

28
Q

What is the purpose of the DNase Test agar

A

differential and selective media

Toluidine blue will inhibit the growth of some G+ cocci. and with Staphylococcus, heavy innoculation is needed to overcome this.

Staphylococcus aureus is a strong positive for this test (clear agar)

Staphylococcus epidermidids is a weak positive

This agar can also differentiate between Serratia species (+) from Enterobacter species (-) and Moraxella (+) from Neisseria (-)

29
Q

Mannitol salt agar

A

has pheol red which is yellow below pH 6.6, orange at pH 6.6 and red above 7.2 and fushia above 8.

the carbohydrate mannitol when fermented produces organic acids which lower the plates pH

30
Q

Novobiocin Susceptibility Test

A

Novobiocin is an aminocoumarin antibiotic produced by the actinomycete Streptomyces niveus

Aminocoumarins inhibit bacterial gyrase from using ATP to manipulate circular chromosomes, preventing DNA replication

done via a Kirby-Bauer antibiotic suseptibility assay (paper disk), and done on enriched Mueller-Hinton agar

Novobiocin is effective against Staphylococcus epidermidis but not Staphylococcus saprophyticus

(this is usually done after the catalase test to differentiate the two since these guys are both -ve)

31
Q

Lancefield antigen serotyping

A

The classification of Streptococci based on serotyping via antigens

32
Q

Group A Strep

A

Streptococcus pyogenes

33
Q

Streptococcus with no Lancefield groups

A

Streptococcus pneumoniae

34
Q

Are enterococcus and Lactococcus part of the Streptococcus genus?

A

No, they were reclassified in 1984

35
Q

Group B Strep

A

Streptococcus agalactiae

36
Q

CAMP test

A

detects the haemolytic substance (CAMP factor) that is produced by Streptococcus afalactiae; A group B streptococcus.

Detects beta haemolytic streptococcus producing CAMP factor, can be transferred via HGT but is rare enough that this is a good indicator of Group B Strep.

37
Q

CAMP test Synergy

A

CAMP factor reacts synergistically with the B-haemolysin that is produced by Staphylococcus aureus

when drawn in a T shape with group B strep, an area of synergy will be present.

38
Q

Bacitracin Suseptibility test

A

Bactracin is a narrow spectrum antibiotic that inhibits the growth of Staphylococcus aureus, Staphylococcus, epidermidis, and Streptococcus pyogenes.

S. pyogens unlike most other b-haemolytic streptococcus species is not resistant and thus this antiobiotic can be used as an identification tag of Group A Strep.

39
Q

Bile esculin Test

A

esculin is a glycoside that can be hydrolyzed by Enterococcus spcies and streptococcus bovis group amound the streptococci.

This hydrolysis is usually done in the presence of bile salts

Cow bile is added and inhibits the growth of most streptococci.

Upon esculin hydrolysis, the ferric citrate indicator is oxidized to form a brown ppt indicating a positive result

40
Q

Streptococcus bovis group

A

S. equinus

S. galloolyticus

S. infantarius

S. alactolyticus

41
Q

What tests differentiate between Streptococci and Staphylococci

A

Gram stains

42
Q

What test can be used to help to identify human staphylococcal pathogens

A

Catalase

Coagulase

DNase

Mannitol Salt Agar

Novobiocin Susceptibility

43
Q

What tests can be used for the identificaiton of human Streptococcal Pathofens

A

Lancefield Antigen serotyping

CAMP

Bacitracin suceptibility

Bile Esculin

44
Q

What test can be used for the identificaiton of Streptococcus pneumoniae

A

Viridan Streptococci

Optochin susceptibility

Bile solubility

Negative stains

45
Q

Viridan Streptococci

A

need to determine if A-haemolytic strep is Strp pneumoniae because it is the most pathogenic

These will produce a green tinge on blood agar

Includes a and g haemolytic streptococcus that includes the mutans group, the anginosum group, the bovis group, the mitis group, and the salivarius group;
organisms that are commonly found in the moutn, upper respiratory tract and urogenital tract

46
Q

Optochin susceptibility test

A

optochin can be used to treat Streptococcus pneumonia infections

S pneumonia is susceptible to optochin, but most other a haemolytic streptococcus are resistant (ie the virdans streptococci)

any clearing around the disk = susceptibility = Taxo P = S. pneumonia

47
Q

Bile solubility test

A

differentiates between pathogenic streptococcus pneumoniae and other a haemolytic streptococcal species

the activate of an autolytic enzyme that induces cell death is increased in the presence of bile salts (sodium desoxycholate= bile salt lowers the surface tensi9on of the plasma membrane and causes S. pneumoniae to digest its own cell wall.)

CELLULAR DEBRIS FROM LYSED CELLS lead to a decrease in turbidity and thus a potitive result

48
Q

Negative stains

A

utalizes an acidic stain that does not penetrate the negatively charged cell wall of bacteria

cell remains clear

useful for observation of spirochetes

heat fixed, as opposed to methanol to maintain structural integrity

also is useful for the dection of capsules

49
Q

Tests for the examination of normal Flora

A

Chocolate agar

Tellurite agar

Sabouraud agar

SIngle step Staphylococcus (4S) agar

TSY+G agar

Mitis Salivarius-bacitracin agar

50
Q

Chocolate Agar

A

non-selective enriched media

casein, peptone, haemoglobin and corn starch

RBC is already lysed from heat treatment

used for the growth of fastidious organisms like pathogenic Neisseria species or Haemophilus species that require X and V blood factors

51
Q

Tellurtie Agar

A

Potassium tellurite inhibits most Gram+ and Gram- organisms, some Staphylococcus species, some Enterococcus species and most Cornebacterium species are able to reduce tellurite to tellurium to produce a grey/ black colony

most other species cannot grow on this

peptone as a carbon source

52
Q

Sabouraud Agar

A

for the growth requirements of yeast and fungi

incubated at room temp to encourage the fungi to grow (heaat = bad)

no selective or differential properties

53
Q

4S Agar

A

SIngle step Staphylococcus (4S) agar
= Baird Parker agar

based ont he ability of Staphylococcus aureus to grow and produce lecithinase in the presence of a high salt conc. and potassium tellurite

the agar has an egg yolk emulsion that will break down in the presence of lecithinase

the reduction of tellurite to telluride will give the colonies a grey colour

SA will produce characteristic grey colonies with white halos

Staphylococcus saptrophyticus may also produce this colony morphology but can be differentiated but the longer incubation time

54
Q

TSY+G Agar

A

enriched medium

Tryptic soy broth with Yeast and glucose

used to culture Propionibacterium acnes, an aerotolerant anaerobic Gram+ non-motile bacillus that is frequently found on the skin

55
Q

Propionibacterium acnes

A

an aerotolerant anaerobic Gram+ non-motile bacillus that is frequently found on the skin

grows well in anerobic enviroments like blocked pores and can cause acne vulgaris and folliculitis

co-infection and inflammation with staphylococcus species lead to disease, and the by product propionic acid decreases skin pH to 3/5 and supresses the growth of other commensal microbes

56
Q

Mitis Salivarius-bacitracin Agar

A

MSB agar

selective and differential medium

selevtive against G+ b/c of Crystal violet
selective agaisnt G- b/c of tellurite

contains trypan blue with will cause most Streptococcus and Enterococcus species to develop a blue colony morphology

57
Q

S mutans MSB agar

A

Indicative of Streptococcus mutans whihc will produce a raised, conves, undulate, opaque, pale-blue colonie that are granular “frosted-glass” sinc ethe colonies produce EPS from the sucrose in the medium

58
Q

S salivarius MSB agar

A

Streptococcus salivarius forms large, pale-blue, mucoid colonies that are glistening “gum-drop” in apperance

59
Q

S mitis MSB agar

A

Streptococcus mitis forms small, flat, hard colonies, blue in colour with a domed centre

60
Q

Enterococci MSB agar

A

Enterococci produce blue-black shiny and slightly raised colonies

M & D (18 decks)

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