Lecture 11 Staphylcocci Flashcards
What are the features of staphylcocci?
- G positive cocci in clusters.
- Staphylos: grape like clusters.
- Facultative anaerobes
- aerobic and anaerobic respiration.
- catalase positive
How is S aureus differentiated from other staphylcocci?
-Coagulase test: allows to differentiate S aureus from other staph
CoNS (coagulase Negative staphylococci).
-golden orange pigment
What are some key features of S. aureus?
- colonizes nasopharynx (30 percent people)
- ß-hemolytic, Coagulase +
- golden orange pigment
- ferments mannitol
- not dangerous until penetrates into skin.
What are some key indicators of S. eperdermidis?
- colonizes skin
- Υ-hemolytic, Coagulase -
- does not ferment mannitol.
What are some indicators of S. saphrophyticus?
- Colonizes the gastrointestinal tract
- Urinary tract infections – SexuallyAactive women
- Υ-hemolytic, Coagulase-
What is the toxin made by S. Aureus that causes skin disease?
- Protein A
- Exfolitin (scalded skin)
What is the effect of Protein A?
Binds to Fc portion of antibody, inhibiting phagocytosis (block attachment to Fc receptors on whit blood cells)
what is the purpose of capsules?
inhibits phagocytosis
what is the effect of coagulase?
Impede progress of leukocytes into infected area by producing clots int the surrounding capillaries.
What is the effect of exfoliatin?
Separates layers of epidermis, causing scalded skin syndrome.
What is the effects of Hyaluronidase?
-Breaks down hyaluronic acid component of tissue, there by promoting extension of infection.
What is the purpose of Leukocidin?
Kills white blood cells by producing holes in their cytoplasmic membrane.
What is the purpose of Lipase?
Breaks down fats by hydrolyzing the bond between glycerol and fatty acids.
What is the purpose of proteases?
Degrade collagen and other tissue proteins.
What are sx of Toxic shock syndrome toxin?
Causes rash, diarrhea, and shock.
What are some diseases caused by S. aureus?
- Skin infections
- bacteremia
- pneuomonia
- Toxin-mediated
- Endocarditis
- Osteomyelitis
What are some skin infections that S. aureus causes?
- Folliculitis, impetigo
- boils, abscess, furuncles
- Cellulitis
What are some toxin-mediated disease caused by S. Aureus?
- Gastro-intestinal intoxication
- scalded skin syndrome
- toxic shock syndrome
How does S. aureus cause folliculitis and abscess?
The organism enters through a hair follicle causing Folliculitis, but once it gets to the subcutaneous tissue, it causes and infection attracting white blood cells.
What causes Staphylococcus to change from a commensal organism to a pathogen?
-Quorom sensing causes toxins to be produced. Staph has a lot of different toxins that can vary between species, 25-30.
What is the the process of Quorom sensing in Staphylcocci?
-AIP (sensing peptide) will bind to receptor once a high enough concentration is met, causing the phosphorylation of Agr A, up regulating the agr operon that contains all the virulance factors.
What are the cytolytic toxins made by S. Aureus?
- alpha (RBCs, leukocytes, excluding neutrophils), beta, delta gamma.
- PVL, PSM
What are the two types of cytolytic toxins made by S. aureus?
- Receptor mediated (Alpha, PVL, gamma) Bi-component. Formation of a defined pore(hexamer to octamer)
- Receptor independent (alpha type PSM) forms short-lived pores.
What are the the general effect of Superantigens?
Causes systemic diseases, not specific to local site.
What are the effects of superantigens created by S. Aureus?
- Exfoliative toxin (scalded skind syndrome)
- Enterotoxins- (food poisoning)
- Toxic shock syndrome (TSST-1)
What major abx have Staphylcocci developed resistance to?
-Penicillin (Used in 1940, resistance rose to 80 percent by 1960, Penicillinase presence).
-Methicillin Beta lactam used to combat resistance Mec A gene regulates resistance. Resistance developed in 1970. At 60 percent resistance.
What is the difference from Hospital MRSA to Community MRSA?
Hospital:
- Abx resistance developed first to many different drugs
- Found in Elderly, immunocompromised, and diabetics
Community:
- abx spreads to community
- Genetically distinct strains
- Generally simple skin infections
- Necrotizing Pneumonia
- In Prisons, Athletes, soldiers, obtained from environmental factors.
What are the respiratory diseases caused by S. Aureus?
- Pneumonia
- Cystic fibrosis
- Community acquired Pneumonia
How was S. Aureus Pneumonia occurring?
- Hospital acquired
- 20-40 percent
- intubation/ ventilator
- Stay at long-term facility
- IV treatment for wounds
- Elderly, Immunocompromised
What is known about Community acquired S. Aureus Pneumonia?
- Necrotizing lung tissue
- younger pts
- preceding influenza like illness
- 30 percent mortality rate
What is known about S. Aureus caused Cystic fibrosis?
- Early association in young children
- Bacterial infection hard to treat because of biofilm
- Increasing MRSA
- Typically replaced by other pathogens
What are the specifics of Exfoliative toxin-mediated skin disease?
- 2 toxins, exfoliatin A and B
- Causes separation of the skin (desquamation)
- Most common in children under 6 (Newborn-Ritter’s syndrome)
- Treatment . (methicillin, Vancomycin, Clindamycin)
What are the specifics of Toxic shock syndrome?
-1980’s
-Extended use of tampons (overnight 8 hr)
-Toxin (TSST-1 strains) causes sytemic infection
-Symptoms:
High fever
Sunburn rash
rapid drop in BP
flu-like sx
How is Toxic shock syndrome treated?
Rapid treatment with abx
-Methicillin, vancomycin, clindamycin
What are some severe outcomes of Toxic shock syndrome?
-organ failure, death
What is the unique about S. Aureus (picnic pathogen)?
- Enterotoxin mediated
- 20 different toxins
- Staphylococcal enterotoxin B (SEB) is a biological warfare weapon.
- Does not need live bacteria to cause disease
What are some sx of the picnic pathogen.
- 30 min- 6 hr onset
- Violent vomiting
- stomach cramping
- Nausea
- Possible Diarrhea
- Rexolve withing 24-48 hours
What are some ways to treat/ prevent the picnic pathogen?
- Fluids (toxin-mediated hard to treat)
- Wash hands prior to food prep
- don’t leave food at room temp
- Use caution with foods at picnics
What are the steps to forming a biolfilm?
- Pre-conditioning of surface
- Attachment
- Cell-to-cell adhesion
- proliferation
- maturation
- dispersion
What are some key features of biofilms?
-partially anaerobic
-slow growing
-cycle of cell dying and replacement
-difficult to treat:
Abx do not penetrate wall
different than planktonic bact
What is endocarditis?
- biofilm infection of the hear tissues
- Both S. aureus and CoNS, faster onset than other bacterial organism
- Due to prior damage to heart
- Common in IV drug users (right side)
How do you treat Endocarditis?
- Prolonged abx therapy
- removal of infected heart valves
What is osteomylitis?
- Biofilm infection of the bone
- most common in children
- Usually found in adults due to IV drug abuse or exposure of bone (severe cellulitis, joint replacement surgery)
What are some treatments of Osteomylitis?
- Prolonged IV abx
- For severe can amputate or debridement.
What is S. epidermidis Disease?
- Biofilm growth requires capsule (polysaccharide intercellular adhesin)
- Hospital acquired infection (Cathether, shunts, heart valves)
How do you treat S. Epidermidis disease?
Remove contaminated device.
