STAPHYLOCOCCUS AUREUS: Gram(+) cocci in pairs or clusters.
STAPHYLOCOCCI
STAPHYLOCOCCUS AUREUS: Gram(+) cocci in pairs or clusters.
Name-Derivation: Grape-Like, Yellow-Gold
Epidemiology / At Risk: Normal flora of anterior nares, skin, perineum.
Spread by sneeze and direct contact.
Manifestations:
Cutaneous: Abscess, boil, carbuncle
Bacteremia: Targets kidneys, lungs, hearts, bone. Possible coagulopathy.
The first thing you will see is an isolate abscess in an organ -- a clue that systemic S. Aures infection is occurring.
You may also see petechial hemorrhages in fingernails, toes, and digits.
Osteomyelitis used to occur in children. Septic arthritis occurs in adults, associated with heroin IV-needle use.
Pneumonia: Especially in children, secondary to a viral infection.
Scalded Skin Syndrome: Bullous lesions leading to desquamation in infants.
It is a result of the toxin -- not the bugs themselves. No bugs are found in the lesion.
It will heal without scarring, if treated carefully and not spread.
Toxic Shock Syndrome: Result of TSS-Toxin. High-grade fever, headache, myalgia, hypotension, rash, diarrhea.
Food Poisoning: Abdominal cramps, diarrhea, vomiting, 2-12 hours after eating.
Associated with mayonnaise kept at room temperature, such as at a picnic.
Endocarditis
Processing:
Specimen: From lung, nose, skin. Can also be taken from a food sample.
Stain: Gram(+)
Dead Gram(+) will appear as Gram(-)
Culture:
Blood Agar (non-fecal specimen): Smooth colonies are indicative of polysaccharide.
White or yellow
beta-Hemolytic -- halos or zones of clearance around them.
Mannitol Salt Agar (fecal specimen): Specimen from food poisoning. Used to distinguish S. AURES from S. Epidermidis.
S. AURES ferments mannitol ------> pigmented colony.
Staph likes to grow in the presence of salt, thus it is often found in salty foods.
Broth Medium can be used to initially, to amplify the number of bugs collected.
Identification:
CATALASE(+): Compare to Strep Pneumoniae. It will break down H2O2 in water to see bubbles.
COAGULASE(+): Free Coagulase Test for SPECIES ID. The bug coagulates blood in the absence of calcium.
Place inoculum in rabbit serum with EDTA, to chelate calcium and remove it from reaction.
Clot form after 4 or 20 hours (there are multiple coagulase types) ------> species is Aureus
No clot forms ------> Epidermidis or Saprophyticus
Mannitol Test: ------> S. AURES ferments mannitol resulting in pigmented colonies, while the others don't.
HOT-COLD HEMOLYSIS TEST: Staph Aureus is the only one that has beta-Hemolysin and thus can damage RBC's at a cold temperature (4C). Other Staph bugs can't.
Virulence:
Extracellular Enzymes:
Coagulase: Clumps all the bugs up together ------> antiphagocytic. Impedes host defenses early in infection.
Human plasma contains coagulase-reacting factor (CRF) which allows it to agglutinate with coagulase in the absence of calcium.
Staphylokinase:
Activates plasminogen ------> plasmin, which in turn degrades fibrin.
Enhances dissemination by allowing bug to escape the fibrous gunk it makes with coagulase.
Phage-mediated factor.
Catalase: Inhibits killing by PMN's.
Hyaluronidase: Enhances dissemination; important early on to establish infection.
Lipase: Provides invasive entry. May penetrate sebaceous glands in eyelid and give us a sty.
Nucleases: Permits the reuse of bug and host nucleic acids.
beta-Lactamase
Exotoxins:
HEMOLYSINS:
alpha-Hemolysin: Leads to beta-Hemolysis, or complete hemolysis of WBC's and RBC's
Kills WBC's as well as RBC's
Transposon mediated
Causes pore formation in blood cell membrane.
beta-Hemolysin: Only damages membranes at a cold temperature, 4C; unique to Staph Aureus.
At 37 it alone is not sufficient to produce hemolysis.
gamma-Hemolysin: not much known
delta-Hemolysin: Detergent, or surfactant-like action.
Kills WBC's as well as RBC's.
Panton-Valentine Leukocidin: Causes WBC lysis and divided into two components.
SLOW COMPONENT binds to GM1 ganglioside in PMN membrane.
FAST COMPONENT then uses phosphatidylcholine as a receptor to gain entry.
EXFOLIATIN: Cleaves the stratum granulosum and causes desquamation in Scalded Skin Syndrome.
Protein a: chromosomal.
Protein b: plasmid-mediated.
ENTEROTOXINS A, B, C1, C2, D: Affects the GI-tract in S. AURES food poisoning.
They are heat stable -- heating (or reheating) food does not denature the toxin.
Toxic-Shock Syndrome (TSS) Toxin: It is a superantigen.
Cell-Associated:
Protein A: Binds the Fc portion of IgG, all four subclasses.
It is antiphagocytic, anticomplement, antigenic, and mitogenic for T-Cells.
It activates cell-mediated immunity and Type IV hypersensitivity response.
Peptidoglycan: Confers hardiness and activates Alternative Complement pathway.
Teichoic Acids: They act as a phage receptor.
Ribitol Phosphate (Polysaccharide A) results in a lot of antigen-antibody complex formation ------> immediate type hypersensitivity.
Surface Polysaccharides: Adhesins, antiphagocytic.
Vaccine / Prevention: Wash your hands!
Treatment: Antibiotics do not work!
STAPHYLOCOCCUS EPIDERMIDIS: Gram(+) cocci in pairs or clusters.
Epidemiology / At Risk: Normal flora of skin, mucous membranes.
Can be spread via catheters and may lead to bacteremia. We can treat the catheter tips with antibiotics and heparin in order to counteract the S. EPIDERMIDIS surface glycocalyx, and prevent it from interacting with platelets.
Manifestations: OPPORTUNISTIC
Endocarditis
Bacteremia
Local infection involving catheters.
Processing:
Stain:
No hemolysis
Does not ferment mannitol.
Broth can be used for amplification.
Identification:
CATALASE(+)
COAGULASE(-): Use Free-Coagulase Test to distinguish from S. AURES.
MANNITOL(-): Does not ferment mannitol.
NO PROTEIN-A, so it does not capture the Fc portion of IgG.
Virulence:
SURFACE GLYCOCALYX: Surface slime is antiphagocytic and interacts with platelets in order to gain entry in IV catheters. Adhesin.
Teichoic Acid
STAPHYLOCOCCI SAPROPHYTICUS:
Epidemiology / At Risk: Sexually transmitted.
Manifestations: Common pathogen in symptomatic UTI's. It adheres selectively to transitional epithelium.
Identification: Same as S. EPIDERMIDIS, except Urease(+)
Virulence:
Urease: Enable survival in urinary tract.
Tropic for urinary transitional epithelium.
Lysostaphin is lethal to S. AURES and other bugs.
STAPHYLOCOCCUS AUREUS: Gram(+) cocci in pairs or clusters.
Name-Derivation: Grape-Like, Yellow-Gold
Epidemiology / At Risk: Normal flora of anterior nares, skin, perineum.
Spread by sneeze and direct contact.
Manifestations:
Cutaneous: Abscess, boil, carbuncle
Bacteremia: Targets kidneys, lungs, hearts, bone. Possible coagulopathy.
The first thing you will see is an isolate abscess in an organ -- a clue that systemic S. Aures infection is occurring.
You may also see petechial hemorrhages in fingernails, toes, and digits.
Osteomyelitis used to occur in children. Septic arthritis occurs in adults, associated with heroin IV-needle use.
Pneumonia: Especially in children, secondary to a viral infection.
Scalded Skin Syndrome: Bullous lesions leading to desquamation in infants.
It is a result of the toxin -- not the bugs themselves. No bugs are found in the lesion.
It will heal without scarring, if treated carefully and not spread.
Toxic Shock Syndrome: Result of TSS-Toxin. High-grade fever, headache, myalgia, hypotension, rash, diarrhea.
Food Poisoning: Abdominal cramps, diarrhea, vomiting, 2-12 hours after eating.
Associated with mayonnaise kept at room temperature, such as at a picnic.
Endocarditis
Processing:
Specimen: From lung, nose, skin. Can also be taken from a food sample.
Stain: Gram(+)
Dead Gram(+) will appear as Gram(-)
Culture:
Blood Agar (non-fecal specimen): Smooth colonies are indicative of polysaccharide.
White or yellow
beta-Hemolytic -- halos or zones of clearance around them.
Mannitol Salt Agar (fecal specimen): Specimen from food poisoning. Used to distinguish S. AURES from S. Epidermidis.
S. AURES ferments mannitol ------> pigmented colony.
Staph likes to grow in the presence of salt, thus it is often found in salty foods.
Broth Medium can be used to initially, to amplify the number of bugs collected.
Identification:
CATALASE(+): Compare to Strep Pneumoniae. It will break down H2O2 in water to see bubbles.
COAGULASE(+): Free Coagulase Test for SPECIES ID. The bug coagulates blood in the absence of calcium.
Place inoculum in rabbit serum with EDTA, to chelate calcium and remove it from reaction.
Clot form after 4 or 20 hours (there are multiple coagulase types) ------> species is Aureus
No clot forms ------> Epidermidis or Saprophyticus
Mannitol Test: ------> S. AURES ferments mannitol resulting in pigmented colonies, while the others don't.
HOT-COLD HEMOLYSIS TEST: Staph Aureus is the only one that has beta-Hemolysin and thus can damage RBC's at a cold temperature (4C). Other Staph bugs can't.
Virulence:
Extracellular Enzymes:
Coagulase: Clumps all the bugs up together ------> antiphagocytic. Impedes host defenses early in infection.
Human plasma contains coagulase-reacting factor (CRF) which allows it to agglutinate with coagulase in the absence of calcium.
Staphylokinase:
Activates plasminogen ------> plasmin, which in turn degrades fibrin.
Enhances dissemination by allowing bug to escape the fibrous gunk it makes with coagulase.
Phage-mediated factor.
Catalase: Inhibits killing by PMN's.
Hyaluronidase: Enhances dissemination; important early on to establish infection.
Lipase: Provides invasive entry. May penetrate sebaceous glands in eyelid and give us a sty.
Nucleases: Permits the reuse of bug and host nucleic acids.
beta-Lactamase
Exotoxins:
HEMOLYSINS:
alpha-Hemolysin: Leads to beta-Hemolysis, or complete hemolysis of WBC's and RBC's
Kills WBC's as well as RBC's
Transposon mediated
Causes pore formation in blood cell membrane.
beta-Hemolysin: Only damages membranes at a cold temperature, 4C; unique to Staph Aureus.
At 37 it alone is not sufficient to produce hemolysis.
gamma-Hemolysin: not much known
delta-Hemolysin: Detergent, or surfactant-like action.
Kills WBC's as well as RBC's.
Panton-Valentine Leukocidin: Causes WBC lysis and divided into two components.
SLOW COMPONENT binds to GM1 ganglioside in PMN membrane.
FAST COMPONENT then uses phosphatidylcholine as a receptor to gain entry.
EXFOLIATIN: Cleaves the stratum granulosum and causes desquamation in Scalded Skin Syndrome.
Protein a: chromosomal.
Protein b: plasmid-mediated.
ENTEROTOXINS A, B, C1, C2, D: Affects the GI-tract in S. AURES food poisoning.
They are heat stable -- heating (or reheating) food does not denature the toxin.
Toxic-Shock Syndrome (TSS) Toxin: It is a superantigen.
Cell-Associated:
Protein A: Binds the Fc portion of IgG, all four subclasses.
It is antiphagocytic, anticomplement, antigenic, and mitogenic for T-Cells.
It activates cell-mediated immunity and Type IV hypersensitivity response.
Peptidoglycan: Confers hardiness and activates Alternative Complement pathway.
Teichoic Acids: They act as a phage receptor.
Ribitol Phosphate (Polysaccharide A) results in a lot of antigen-antibody complex formation ------> immediate type hypersensitivity.
Surface Polysaccharides: Adhesins, antiphagocytic.
Vaccine / Prevention: Wash your hands!
Treatment: Antibiotics do not work!
STAPHYLOCOCCUS EPIDERMIDIS: Gram(+) cocci in pairs or clusters.
Epidemiology / At Risk: Normal flora of skin, mucous membranes.
Can be spread via catheters and may lead to bacteremia. We can treat the catheter tips with antibiotics and heparin in order to counteract the S. EPIDERMIDIS surface glycocalyx, and prevent it from interacting with platelets.
Manifestations: OPPORTUNISTIC
Endocarditis
Bacteremia
Local infection involving catheters.
Processing:
Stain:
No hemolysis
Does not ferment mannitol.
Broth can be used for amplification.
Identification:
CATALASE(+)
COAGULASE(-): Use Free-Coagulase Test to distinguish from S. AURES.
MANNITOL(-): Does not ferment mannitol.
NO PROTEIN-A, so it does not capture the Fc portion of IgG.
Virulence:
SURFACE GLYCOCALYX: Surface slime is antiphagocytic and interacts with platelets in order to gain entry in IV catheters. Adhesin.
Teichoic Acid
STAPHYLOCOCCI SAPROPHYTICUS:
Epidemiology / At Risk: Sexually transmitted.
Manifestations: Common pathogen in symptomatic UTI's. It adheres selectively to transitional epithelium.
Identification: Same as S. EPIDERMIDIS, except Urease(+)
Virulence:
Urease: Enable survival in urinary tract.
Tropic for urinary transitional epithelium.
Lysostaphin is lethal to S. AURES and other bugs.
