2.1 Mmi Exam3: Musculoskeletal 2

Front 1

Gram + Staphylococci produce ________

what are the three major medically important staphylococci?

Back 1

catalase

S. aureus,

S. epidermidids,

S. saprophyticus

Front 2

where is S. aureus carried in 30% of the population?

Back 2

anterior nares

(also common on body skin & perineum)

Front 3

If someone contracts S. aureus in the hospital, what is the most likely source?

Back 3

medical personnel

(resistant to drying, reinfection common)

Front 4

which staphylococcus is sensitive to novobiocin?

which is resistant?

Back 4

sensitive: epidermidis

resistant: saprophyticus

Front 5

which member of the staph family is more likely to cause prosthetic infections?

UTI's in young sexually active females? Osteomyelitis & septic arthritis?

Back 5

prosthetic: epidermidis
UTI: saprophyticus
osteomyelitis: Aureus

Front 6

what two pathogens create biofilms?

what can they cause due to their ability to create biofilms?

Back 6

strep viridans and staph epidermidis.

Both can cause subacute bacterial endocarditis.

Front 7

what is antigenic and relatively specific for S. aureus (contained in the cell wall of S. aureus)?

Back 7

ribitol-Teichoic acid

Front 8

what is S. aureus's virulence factor that binds to the Fc portion of IgG molecules?

Back 8

Protein A

Front 9

what is the function of Protein A?

Back 9

blocks Fc binding to Fc receptor on phagocytes, preventing phagocytosis

Front 10

what is the pathogenesis of osteomyelitis via staph aureus?

Back 10

1) colonization: via adhesins (bind to laminin, fibrinonectin, etc)
2) invasion: via staphylokinase, hyaluronidase, & other extracellular enzymes
3) resistance to phagocytosis: protein A & coagulase, produces catalase.
4)resistance to immune responses: antigenic variance
5) Toxins: release of toxins--- hemolysins, leukocidin

Front 11

What toxins does S. aureus release?

Back 11

alpha-toxin

exfoliatin

PTSAgs (Pyrogenic Toxin superantigens)

Staphylococcal enterotoxins (GI disturbance)

TSST-1 (toxic shock syndrome toxin)

Front 12

Which toxin in only produced by S. aureus (coag pos staph)?

What does it do?

Back 12

alpha-toxin

creates transmembrane pores

(allows other molecules to be released into cell)

Front 13

what is the function of exfoliatin?

Back 13

works between stratum spinosum and stratum granulosum causing intracellular splitting of the epidermis (detaching) causing global denutation.

Front 14

why are (PTSAgs & TSST-1) superantigens called superantigens?

Back 14

bc the superantigen binds outside the MHC molecule & outside of the V-beta region of the T cell. Therefore the specificity is loss they can bind to anything. This will cause a mass proliferation of inflammatory cells- IL-1, TNF-alpha.

= induce toxic shock syndrome

Front 15

what is the difference between the triggering points of gram negative shock and toxic shock syndrome?

Back 15

gram negative shock is triggered by LPS (ie all the inflammatory cytokines are induced by the LPS).

toxic shock syndrome: all of the inflammatory cytokines are triggered by TCR. (can be caused by both s. aureus & strep pyrogenes)

Front 16

What organisms show beta-hemolysis on sheep blood agar?

Back 16

Staphylococcus sp.

Streptococcus sp. (groups A & B)

Front 17

The catalase test can be used to differentiate btwn staph & strep, which will be +?

Back 17

Catalase enzyme is produces by staphyloccus sp ONLY

Front 18

ONLY staph aureus ferments on what medium? what color does this medium turn?

Back 18

mannitol salt agar. Turns from red to yellow.

Front 19

what are the coagulase negative staphylococci?

Back 19

s. epidermidis and s. saprophyticus

(only S. aureus will be coag positive)

Front 20

How does coagulase work?

Back 20

it breaks down fibrinogen to fibrin making a mechanical barrier around it which allows it to evade phagocytosis.

Front 21

How can you differentiate btwn the two coagulase negative staphs (s. epidermidis & s. saprophyticus)?

Back 21

Novobiocin discs

zone of inhibition= sensitivity= S. epidermidis

no zone= resistance= S. saprophyticus

Front 22

S. Aureus diagnosis:

Back 22

*Microscope: Gram + cluster of grapes (purple)

*Blood agar: overnight growth

*Catalase Test: Positive

Coagulase: Positive

Mannitol=salt agar: red--> yellow, mannitol fermenting

(* these are same for all staph)

Front 23

S. aureus was initially treated w/ penicillin, but developed resistance via _______________

Back 23

penicillinase or beta-lactamase

^ breaks down penicillin by opening the beta-lactam ring & preventing drug action

Front 24

what is the mechanism of penicillin resistance?

Back 24

chromosome (G) mediated- coating of beta lactamase enzymes

Front 25

how does penicillin inhibit cell wall synthesis?

Back 25

by binding to transpeptidases (penicillin binding protein,PBP)

Front 26

what is the function of transpeptidase?

Back 26

catalyze the crosslinking of peptidoglycans

Front 27

T/F

if penicillin can reach the transpeptidase, it can still inactivate it.

Back 27

true

Front 28

A semi-synthetic penicillin, methicillin, was created to treat penicillin resistant s. aureus.

How did S. aureus then become methicillin resistant S. aureus or MRSA?

Back 28

S. aureus acquired a gene encoding for a different type of transpeptidase (PBP), with a reduced affinity for the beta-lactam antibiotics (penicllin & methicillin can no longer bind PBP), thus allowing cross-linking

Front 29

what is the mechanism of MRSA?

Back 29

plasmid mediated transduction

Front 30

what is the DOC for tx of MRSA?

what problem is arising?

Back 30

vancomycin; vancomycin resistant MRSA.

Front 31

what does vancomycin directly bind to? what does it inhibit?

Back 31

terminal AA side chain (NOT PBP)

*it inhibits the crosslinking of peptidoglycans, PBP cannot bind to side chain

Front 32

what is vancomycin resistance?

Back 32

when the terminal chain of the AA is changed and vancomycin can't bind.

Front 33

how is multidrug resistance acquired?

Back 33

via plasmid mediated transposition which involves the transposon

Front 34

what do you give a patient who is methicillin sensitive?

Back 34

nafcillin or oxacillin

Front 35

what do you give a pt who is methicillin resistant?

Back 35

vancomycin

Front 36

What do you give pt who is methicillin AND oxacillin resistant?

Back 36

Linezolid or Levoflaxacin + rifampin

Front 37

what do you give a pt who is vancomycin resistant?

Back 37

streptogramin (dalfopristin and guinupristin in combo)

or

Daptomycin

Front 38

After Staph Aureus what is the 2nd MC cause of ALL osteomyelitis?

Back 38

strep. Pneumonia

Front 39

what pathogen causes osteomyelitis after trauma or surgery?

Back 39

Group strept A (s. pyrogenes)

Front 40

what causes osteomyelitis in neonates?

Back 40

S agalaciae (GBS)

Front 41

what causes osteomyelitis in older infants, children and adults?

Back 41

S. viridans

Front 42

what causes osteomyelitis in pts with hemolytic disorders?

Back 42

S. Viridans

Front 43

what are the three types of streptococci that are lancefield antigens?

ALL of these organisms are involved in _________

Back 43

S. pyogens, S. agalactiae, S. pneumoniae

osteomyelitis

Front 44

Which sp. are beta-hemolytic streptococci?

Back 44

Group A strep: S. pyrogenes

&

Group B strep: S. agalactiae

(staph are also beta-hemolytic)

Front 45

Which streptococcus is bacitracin sensitive?

Back 45

Group A Streptococcus

Front 46

what is the confirmatory test for group B streptococcus?

Back 46

CAMP test

(*characteristic arrowhead = CAMP +)

Front 47

which sp. are alpha-hemolytic (partial hemolyisis) streptococci?

Back 47

S. pneumoniae & S. viridans

Front 48

how do you differentiate s. viridans from s. pneumonia?

Back 48

optochin disc. Pneumonia is sensitive to optochin.

*or bile test, pneumonia is autolytic & bile will become clear= + result*

Front 49

what is the only gram positive diplococci?

(ALL strep are gram positive)

Back 49

S. Pneumoniae

(s. agalactiae & S. pyrogenes are both arranged in chains)

Front 50

what virulence factors of streptococcus binds to surface molecules like fibronectin?

Back 50

Protein F, M protein and Lipoteichoic acid

Front 51

what is the essential virulent factor for streptococcus pyogenes?

what does it do?

Back 51

M protein; it degrades C3b (an opsonin) and allows evasion of phagocytosis.

Front 52

what is serotype detection used for?

what protein is essential for this serotyping?

Back 52

difference between pyogenes and pneumoniae (streptococcal).

M protein

Front 53

what strain of M protein causes post streptococcal glomerulonephritis?

Back 53

M12

Front 54

Rheumatic fever is a complication of ___________.

It occurs when pathogenic Ags cross-react w/ antigenic epitopes on cardiac & joint tissue.

how do you confirm the diagnosis of rheumatic fever?

Back 54

group A strep (pyrogenes) pharyngitis

if the pt has either 2 major criteria conditions or one major and 2 minor criteria.

Front 55

what is included under the major criteria for Rheumatic Fever?

Back 55

carditis (mitral & aortic valve damage)

arthritis,

chorea,

subcutaneous nodules,

erythema marginatum

Front 56

what is included under the minor criteria for Rheumatic Fever?

Back 56

fever, joint pain, electrical changes in the heart, presence of certain proteins in the blood.

Front 57

Rheumatic fever tx:

Back 57

Tx Strep: Penicillin-G + 5 yr maintanence dose

+ any symptoms;

Pain & inflammation: Aspirin

Carditis: steroids

Chorea: Diazepam or haloperidol

Front 58

__________ also contains Lancefield antigen (D) & was previously referred to as Strep group D, gamma-hemolytic (no hemolysis)

Back 58

enterococcus

Front 59

which pathogen is a normal intestinal/genitourinary flora that is able to withstand high bile and salt?

Back 59

enterococci

*thus infection occur after procedures involving these areas

Front 60

what are the 2 common enterococci species

Back 60

E. faecalis

E. faecium

Front 61

what is the medium of choice for enterococcus growth?

Back 61

bile esculin agar

** no other bacteria can survive on this, turn agar BLACK!

Front 62

where do you usually encounter enterococcal infections?

Back 62

hospital settings

Front 63

three pathogens can cause subacute endocarditis, what are they?

Back 63

strept viridans, staph aureus, and enterococcus

Front 64

Enterococci are responsible for

nosocomial-UTIs

Intra-abdominal infections

Blood stream infections

& Osteomyelitis due to ______________

Back 64

osteomyelitis due to contaminated open wound & prosthetic joints

Front 65

T/F

enterococci is resistant with B-lactams.

Back 65

TRUE

they are relatively resistant to B-lactams and aminoglycosides.

Front 66

what are the agents of choice for minor enterococcus infections?

Back 66

penicillin and ampicillin (PARADOXICAL)

(*major infections= penicillin + vancomyocin)

Front 67

An elderly man is suspected to have BPH. After undergoing an exploratory cystoscopy he comes down with bacteremia resulting osteomyelitis (or endocarditis). What is the likely pathogen responsible?

Back 67

Enteroccoci

Front 68

Osteomyelitis following clenched-fist bite wound of the proximal phalanx is indicated by......

Back 68

-concurrent bone erosion & subperiosteal bone deposition (found on x-ray)

&

-discharging sinus on dorsum of proximal phalanx

Front 69

what pathogen can cause osteomyelitis following a dog or cat bite?

what about human bites?

Back 69

Pastruella multicolor;

kingella kingae & eikenella corrodens

Front 70

Both K. Kinage & E. corrodens are ________ positive

Back 70

oxidase

Front 71

how do you differentiate kingella kingae from einkella corrodens?

Back 71

einkella corrodens has lysine decarboxylase and ornithin decarboxylase.

Kingella kingae does not.

Front 72

when ornithine is present in the medium, what color does the solution change?

Back 72

ornithine: purple = Einkella

Front 73

what type of selective media is helpful for recovering kingella kingae?

Back 73

a selective media containing clindamycin or vancomycin

*short gram - rods w/ square ends

Front 74

what makes Kingella kingae different from all the other kingella's?

Back 74

it's beta-hemolytic

Front 75

what does a mature colony of Eikenella corrodens grow on? what color will it be?

Back 75

grows on blood & chocolate agar, requires hemin for growth

yellow in-grown colonies

Front 76

Why does Eikenella corrodens smell like bleach?

Back 76

produces hypochlorite

Front 77

Eikenella produces gram - rods, that may twitch, on what type of selective medium?

Back 77

selective medium containing clindamycin

Front 78

both Einkella corrodens and Kingella Kingae are susceptible to what?

However, due to slow growth, bites are usually tx w/ what while waiting to identify the organisms?

Back 78

B-lactam antibiotics, tetracycline and quinolones

3rd-generation cephalosporin

Front 79

In addition to osteomyeltis, what else do Einkella infections cause?

Back 79

septic arthritis

endocarditis

Front 80

Einkella corrodens & what kingella species are part of the HACEK group of atypical endocarditis orgnanisms?

Back 80

Kingella dinitrificans

Front 81

HACEK group (E. corrodens & K. dinitrificans) are the most common cause of gram - endocarditis in _______________

Back 81

non IV drug users

(HACEK organisms are all in the oral cavity)