#Staph

Question 1

Which bugs make up your class of gram positive cocci?

Answer 1

Staphylococcus

Streptococci

Enterococci

Question 2

Based on morphology, how do you distinguish Staph from Strept and Entero?

Answer 2

See below

Question 3

Which enzyme does Staph have that Strept and Entero don’t?

Answer 3

Catalase

Question 4

Staph can be further divided into coagulase +ve and coagulase -ve. Which Staph spp is in each category?

Answer 4

S. aureus (coag +ve)

Coagulase-negative staphylococci

S. epidermidis et al. (Device-related infections)

S. saphrophyticus (UTI)

S. lugdenensis (Native-valve endocarditis)

Question 5

How do you determine if Staph is coagulase +ve or -ve?

Answer 5

Coag test: place down fibrinogen then a colony of each organism. If +ve, takes fibrinogen to insoluble fibrin which is clumpy, and if neg, you get a milky substance

Question 6

Which bug has the white colonies and which one has the yellow colonies?

What does the area of black around the yellow colonies indicate?

Answer 6

S aureus - yellow

S epidermidis - white

Staph aureus – gold (the area of black can actually be seen thru = beta hemolysis)

Epidermidis doesn’t have same level of beta hemolysis

Question 7

What 2 factors does S. aureus have that allow it to evade the host immune system?

Answer 7

Has polysaccharide capsule – avoid phagocytosis

Protein A – binds antibodies at Fc region, rendering the Ab inactive

Question 8

Protein A belongs to a group of adhesion molecules for Staph. What’s the group called?

Answer 8

“Microbial surface components recognizing adhesive matrix molecules”

Includes Protein A

Question 9

Describe the functions of the following enzymes:

Coagulase

Hyaluronidase

Answer 9

Promotes bacterial spread/invasion thru tissues:

Coagulase – microthrombus formation (provides an environment where the organism can actually live and seed)

Hyaluronidase - hydrolyzes hyaluronic acid

Question 10

How does having the catalase enzyme improve bacterial survival for Staph?

Describe the functions of the following enzymes involved in tissue destruction:

Fibrinolysin

Lipase

Nuclease

Answer 10

•Improves bacterial survival

Catalase - removes hydrogen peroxide

•Tissue Destruction

Fibrinolysin - dissolves fibrin clots

Lipases - hydrolyzes lipids

Nucleases - hydrolyzes DNA

Question 11

What is the role of cytotoxins in Staph virulence? Name the 2 types of cytotoxins produced by S. aureus

Answer 11

Cytotoxins:

Hemolysins (RBCs) and Leukocidin (WBCs)

Lyse cell membranes (of specific cell lines)

Destroy leukocytes, erythrocytes, macrophages

Question 12

Describe the function of cytolytic peptides in S. aureus

Answer 12

Recruit then lyse neutrophils

**Overproduced in community-associated MRSA**

Question 13

Name the syndrome/condition ass’d with each of the following toxins:

Exfoliative toxins

Enterotoxin

Toxic Shock Syndrome Toxin I

Answer 13

Exfoliative toxins >> Scalded Skin Syndrome

Enterotoxin >> Food Poisoning

Toxic Shock Syndrome Toxin I >> Sepsis

Question 14

Cutaneous pyogenic diseases caused by Staph aureus include impetigo, folliculitis, furuncles, carbuncles and wound infections. Describe each of the above

Answer 14

Impetigo – honey crusted surface-level infection seen in children (due to staph or strept)

Folliculitis – Staph aureus can progress to folliculitis where the follicles (hair) are inflamed

Furuncle – infected and inflamed follicle that spreads further)

Carbuncles – multiple furuncles

Wound infections – from incisions, for example

Question 15

Invasive pyogenic conditions caused by S. aureus include pneumonia, ___, osteomylitis and ___, all of which can result from skin infection or direct inoculation

Answer 15

Invasive pyogenic conditions caused by S. aureus include pneumonia, endocarditis, osteomylitis and septic arthritis, all of which can result from skin infection or direct inoculation

Question 16

How do you evaluate endocarditis in a Staph infection and what is the treatment?

Answer 16

If Staph is found in the blood stream, you do an echocardiogram to see if there’s pathology in the heart valves

Treatment: Requires high antibiotic levels given IV to treat endocarditis

Question 17

Which Staph toxin mediated syndrome results from dissemination of exfoliative toxins leading to splitting of the stratum granulosum and subsequent sterile blisters and skin scalding?

Answer 17

Staphylococcal scalded skin syndrome

Happens commonly in babies

Colonization on umbilical cord or infection

Common in people without immunity, due to exotoxin dissemination such that the stratum granulosum starts to split (translation: the superficial skin is literally coming apart)

No scarring because its higher up in skin layer

Question 18

A localized form of Staph Scalded Skin Syndrome is ___. It results from local spread from infected wound. The disyndrome is characterized by blisters with bacteria, inflammatory cells and systemic symptoms

Answer 18

Bullous Impetigo

(see below)

**note that this is basically SSSS in adults**

Question 19

___ is characterized by acute onset N/V, diarrhea and abd pain w/o fever

Answer 19

Staphylococcal Food Poisoning

Due to ingestion of pre-formed toxin (no real invasion)

Enterotoxins are heat and acid stable; interact with vagal emetic receptors (N/V)

Self limited illness

Treatment is supportive

Question 20

Staphylococcal ___ ___ Syndrome is an acute onset syndrome that is characterized by a diffuse erythematous rash, fever and hypotension. The most common cause of this syndrome is ___

Answer 20

Staphylococcal Toxic Shock Syndrome is an acute onset syndrome that is characterized by a diffuse erythematous rash, fever and hypotension. The most common cause of this syndrome is TSST1.

**Can be production of toxin but generally result of progressive tissue infection

TSST1 is a superantigen that leads to septic shock**

Question 21

Coag negative Staph (e.g. Staph epidermidis) has many of the same virulence factors as S aureus except 2. Name 2 differences between these 2 bugs

Answer 21

Coag negative Staph forms a slime layer (biofilm) and it has no (or very few) toxins

**Not same tissue destruction seen with S. aureus**

Question 22

S epidermidis is known to cause infection of ___ material

UTIs and pyelonephritis are commonly ass’d with ___ (Staph type) infection

S ludgenensis can be found in infections of (native/prosthetic) heart valves

Answer 22

Infections of prosthetic material (that #biofilm)

S epidermidis is known to cause infection of prosthetic material

UTIs and pyelonephritis are commonly ass’d with S saphrophyticus (young women with fancy UTIs smell like safron) infection

S ludgenensis can be found in infections of native heart valves

Question 23

When would you give empiric therapy?

Which antibiotic would you give if the patient is relly sick and you suspect bacteremia or an invasive infection?

Which antibiotic would you give if the patient is not that sick and has a skin/soft tissue infection?

Answer 23

Empiric therapy: when you don’t yet know the organism that’s the cause of disease

•Is the patient sick?

–YES, suspect bacteremia/invasive infection: vancomycin, daptomycin [not in pneumonia]

•maybe linezolid, ceftaroline

–NO: outpatient skin/soft tissue: clindamycin, TMP/SMX, doxycycline, linezolid

•maybe dalbavancin or oritavancin

Question 24

For definitive Staph treatment, the 1st line of therapy if the bug is susceptible is __

Answer 24

•FIRST line:

–Anti-staphylococcal penicillins

–Oxacillin, cefazolin

Question 25

Vancomycin and daptomycin are a __ line of Staph treatment for resistant Staph or in case of penicillin allergy

Answer 25

2nd line of treatment

Question 26

What is the first line of treatment for Staph infection in an outpatient setting if it’s susceptible?

Answer 26

•FIRST line:

–Anti-staphylococcal penicillins

–e.g. Dicloxacillin, cephalexin

Question 27

Which drugs would you give as a second line of treatment in case of resistant Staph infection/allergy to penicillin in an outpatient setting?

Answer 27

•Second line:

– Clindamycin, TMP/SMX, doxycycline (CA-MRSA)

– Linezolid, dalbavancin, oritavancin

Question 28

How can you tell the difference between a skin/soft tissue infection caused by Staph aureus vs Streptococcus?

Answer 28

see below