Staphylococcus

Question 1

Staph are all..

Answer 1

catalase positive

Gpos cocci in clusters

Question 2

Staph groups

Answer 2

Staph aureus

Staph epidermidis

Staph saprophyticus

Question 3

Staph aureus features

Answer 3

• basic habitat nares of nose
• produces yellow pigment
• beta-hemolytic
• coagulase positive (forms fibrin clots in plasma)
• catalase positive
• Protein A virulence factor (blocks Fc-IgG interaction preventing phagocytosis and complement activation)
• produces toxin related diseases

Question 4

Staph aureus infections

Answer 4

• Toxin disease
  
  • Toxic shock syndrome (TSST-1)
  • Food poisoning (staph aureus enterotoxin)
  • Scalded Skin Syndrome (Exfoliatin)
• Infectious diseases
  
  • Skin infections (impetigo)
  • Pneumonia
  • Endocarditis
  • Osteomyelitis
  • Abscesses

Question 5

Toxic shock syndrome

Answer 5

Toxin: TSST-1

fever

shock

red rash

diffuse red erythema (sun burn)

after weeks desquamation of palms and soles

diarrhea

tampons or surgical wound packing

Question 6

Staph food poisoning

Answer 6

food handler contaminates food and often when food is left at room temp for several hours (picnic)

staph grows in food and makes enterotoxin (ingest pre-formed toxin to get sick)

illness develops 3-6 hours later

NV and abdominal cramps

multiple sick people

classic food is mayonaise (potatoe or egg salad)

Question 7

Scalded skin syndrome

Answer 7

Staph Exfoliative toxin (exfoliatin)

occurs in newborns 3-7 days old

fever, diffuse erythema starting at the mouth

sloughing of skin (toxin destroys keritnocyte attachments in stratum granulosum only)

Damage in intraepidermal and heals completely without scarring

Nikolsky’s sign (skin slips off with gentle tug)

Question 8

Bullous impetigo

Answer 8

Bullous type is caused by Staph aureus

honey colored crusted lesions

bullous impetigo is a variant of impetigo with bullae (fluid-filled sacs)

occurs in children and easily spread

S. aureus exfoliative toxin strains

Question 9

Staph pneumonia

Answer 9

rare cause of lobar pneumonia

classically occuring as a post-infectious pneumonia (following influenza)

Question 10

Staph endocarditis

Answer 10

• classic cause of acute endocarditis featuring
  
  • rapid onset of symptoms
  • very ill pts
  • often no pre-existing valve disease
• Contrast with subacute endocarditis caused by Strep viridans
  
  • slower onset
  • less sick patient
  • prior valve abnormality

Question 11

Subacute endocarditis

Answer 11

• subacute endocarditis caused by Strep viridans
  
  • slower onset
  • less sick patient
  • prior valve abnormality
• As opposed to Staph acute endocarditis

Question 12

Staph bacteremia

Answer 12

common cause is central lines

most important prevention technique is the sterile technique

• wash hands
• gloves
• sterile insertion practices

Question 13

Staph osteomyelitis

Answer 13

• Staph is a common cause of osteomyelitis
• in children often occurs in long bones
  
  • femur
  • tibia
  • fibula
• in adults
  
  • usually spine
• hematogenous spread
• spread from skin soft tissues
• Trauma (surgery)
• symptoms
  
  • localized pain +/- fever
• Dx: imaging (CXR, CT or MRI)

Question 14

Classic causes of Osteomyelitis

Answer 14

• Child
  
  • staph aureus (hematogeonous spread)
• Sickle Cell patient (functionally asplenic)
  
  • Salmonella (hematogenous spread)
• TB pts
  
  • Pott’s Disease (vertebrae/spine)
• Diabetic
  
  • Polymicrobial from foot ulcer
• bedbound pts
  
  • polymicrobial from pressure sores

Question 15

Staph cellulitis

Answer 15

infection of deep dermis and subcutaneous fat

Most often cause by beta-hemolytic strep but S aureus can also cause it

Use antibiotics that cover staph and strep

Question 16

Staph abscesses

Answer 16

• Bacteria and inflammatory cells (pus)
• walled off in deep tissues
• skin abscesses are commonly caused by Staph aureus
  
  • furuncle= boil; infection of hair follicle
  • carbuncle= multiple boils clustered together
• Tonsilar abscesses
• mainstay of treatment is incision and drainage

Question 17

Staph aureus antibiotics

Answer 17

• most staph are resistant to pennicllin
• produce beta-lactamases
• antistaphylococcal penicillins
  
  • Dicloxacillin
  • Nafcillin
  • Oxacillin
• First generation cephalosporins
  
  • Cephalexin
• Beta-lactam + inhibitor
  
  • Amoxicillin/Claulanate

Question 18

MRSA antibiotics

Answer 18

• Resistant to all beta-lactams (altered penicillin binding proteins)
• important hospital acquired bacteria
  
  • sometimes can be community acquired
• Vancomycin or Daptomycin are the antibiotics of choice
• can also use Linezolid

Question 19

Staphylococcus epidermidis features

Answer 19

• normal skin flora
• not normally pathogenic but
  
  • blood culture contaminant (needle or IV contaminated with S. epidermidis)
  • infects prosthetic materials in blood (catheters, pacemakers, prosthetic valves and joints)
    
    • surface molecules aid in adherance
    • produce biofilms
• Often Methicillin resistant
• Tx: Vancomycin

Question 20

Staphylococcus epidermidis treatment

Answer 20

***Vancomycin***

As it is often Methicillin resistant

Question 21

Staphylococcus saprophyticus features

Answer 21

• Cause of UTIs (especially in sexually active women)
  
  • most are caused by E. coli (90%)
    
    • others are Proteus, Klebsiella, S. saprophyticus
• Key features
  
  • sexual activity (honeymooner’s cystitis)
  • Nitrite negative on urine dipstick (E. coli is nitrite positive)
• Treated with UTI antibiotics
  
  • Fluoroquinolones
  • SMX-TMP
  • Nitrofurantoin