Staph

Question 1

What is implicated in nasal and skin colonization

Answer 1

Adhesins and wall techoic acids

Question 2

Leading cause of nasocomial infx

Answer 2

Staph aureus

Question 3

Latrogenic infx

Answer 3

Due to activity of doctors or therapy

Question 4

Colonization (4Ds)

Answer 4

Diabetics
Dialysis patients
Damaged skin
AIDS

Question 5

Transmission is via

Answer 5

Direct contact skin to skin

Contact with fomites (contaminated objects)

Question 6

General characteristics

Answer 6

Pyogenic non motile
Non sporing
Gram positive
Aerobes or facultative anaerobes

Aureus n lugdunesis are most virulent

Question 7

Coagulase

Answer 7

Bacterial surface enzyme
Converts fibrinogen to fibrin

2 types free and bound

Free is secreted extracellular

Bound is clumping factor. Associated with cell wall

Question 8

Device related and urinary tract infx commonly caused by

Answer 8

Staph epidermidis haemolyticus and saprophyticus

Question 9

Focal infections

Answer 9

Anterior eye infx
Cutaneous infx
Catheter infx

Question 10

Toxin producing strains

Answer 10

Food posing
Toxic shock syndrome
Scalded skin syndrome

Question 11

Disseminated infx due to bacteremia

Answer 11

Post eye infx
Pneumonia
Endocarditis
Septic arthritis

Question 12

Factors facilitating colonization

Answer 12

Binds nasal epithelial ligands
Clumping factor b, iron regulated surface determinant a

Resist antimicrobial peptides
Aureolysin / staphlokinase / protein f

Question 13

Atopic dermatitis

Answer 13

Chronic and intermittent skin inflammation associated with allergic rx
Accompanied with elevate serum igE levels

S aureus colonizes 40-90% of patients

Question 14

MRSA

Answer 14

Methicillin resistant

Most important in hospitals

Question 15

Coagulase test

Answer 15

Only S aureus is positive bc it has free coagulase

Question 16

Virulence is determined by 2 regulatory genes

Answer 16

Accessory gene regulator agr (part of quorum sensing) (influence biofilm)
Staph accessory regulator sar

Question 17

Catalase test

Answer 17

Positive organisms rapidly make bubbles when exposed to a solution containing hydrogen peroxide

All staph contain catalase

Question 18

Genome

Answer 18

Core
Accessory due to acquisition of info from horizontal transfer (has pathogenicity islands)
Foreign

Question 19

PBP2a

Answer 19

Insensitive to penicillin and beta lactam

Makes cell wall peptodoglycan even when normal penicillin binding proteins are inhibited

Question 20

MSCRAMMS

Answer 20

Mediate adherence to host tissues

Key role in initiation of endovascular infections, bone and joint infections and prosthetics infection

Question 21

Virulence factors

Answer 21

Phagocytic inhibitors (protein a)
Surface proteins for climbing (clump factor, collagen binding protein, coagulase)
Exotoxins (toxic shock, exofoliation, super antigens)
Membrane damaging toxins (haemolysins, leukotoxins, leukocidins)
Invasins (kinases, hyaluronidase, staphulkinae, lipase)

Question 22

Protein a

Answer 22

Prevents opsoniZation and phagocytosis

Bind Fc part of IgG

Binds to von Willebrand factor - which is present at damage site of epithelium

Question 23

Coagulase

Answer 23

Exotocin that forms fibrin around bacteria and protects from phagocytosis

Production is synonymous with invasive pathogenic potential

Question 24

Clumping factor

Answer 24

Surface protein
Responsible for adherence of organisms to fibrinogen and fibrin

Role in wound and foreign body infx

Question 25

Haemolysins

Answer 25

Produced to disable immune defenses Destroy neutrophils, RBCs, macrophages and platelets Alpha subtype is pore forming toxin causing leukocyte destruction

Question 26

Leucocidins

Answer 26

Destroy leucocytes

Question 27

Staph mechanism

Answer 27

Makes proteins to burrow thru tissues and metastasize other sites Hyaluronidase is spreading factor Protease destroys tissue proteins Staphylokinase causes fibrinolysis Lipase degrades fats and oils that help colonize sebaceous gland

Question 28

Staph aureus has a capsule

Answer 28

Causes frustrated phagocytosis | Peptidoglucan cel wall has endotoxin like activity and impt on causing infx

Question 29

Exfoliative toxins are exotoxins

Answer 29

Cause skin to slough off Super antigens They are enterotoxins

Question 30

Hallmark pathology

Answer 30

Pyogenic inflammation Local destructiveness Cause abscess formation Initial response is polymorphonuclear leukocyte (PMN) response and subsequent infiltration of macrophage and fibroblasts

Question 31

Skin infections

Answer 31

Abscess, faruncle Carbuncle: deep subcutaneous infx that spreads and burrows into skin sinuses Impetigo : contagious infx around Lithuania where postules may form (epidermis) Folliculitis: yellow postule with narrow red margin (superficial dermis) Fsruncle: deep dermis, infx of hair follicle and surrounding skin

Question 32

CNS impacts

Answer 32

Spread by blood or adjacent structures followed by sinusitis Cause brain abscesses then aortic valve endocarditis then papilledema Staph causes spinal epidural abscess Causes intracranial thrombophlebitis

Question 33

Endovascular infx

Answer 33

Hear valves Acute endocarditis had 50% mortality Most common cause of acute osteomyelitis

Question 34

Trojan horse mechanism of blood borne transmission

Answer 34

Tissue innoculation to Bloodstream (dissemination) Tissue metastatic infection (bone heart and prosthetics)

Question 35

Gastroenteritis

Answer 35

Due to one of 8 types of toxins Need to replace fluid electrolyte loss Food poisoning

Question 36

Toxic shock syndrome

Answer 36

Due to exotoxin release High fever vomiting diarrhea rash Redness Of mucosa

Question 37

In relation to eye fibronectin

Answer 37

Binds corneal cells | Mediated by fibronectin binding Pretoria in bacterial