Chapter 1.5 Staphylococci Flashcards
Where are staphylococci commonly living in normal individuals?
Nasopharynx and skin
What are the 3 major pathogenic species of staphylococci?
Staphylococci aureus, staphylococci epidermidis, and staphylococci saprophyticus
What is the shape of staphylococci?
They lie in grape-like clusters on Gram stain
What test is positive for staphylococci?
Catalase test
*different than streptococci which have negative catalase test
How can staphylococcus aureus be differentiated from beta-hemolytic streptococci?
Since they all are beta-hemolytic the difference is that staphylococcus aureus shows a golden pigment on sheep blood agar
What species of staphylococcus is an actual pathogen?
Staphylococcus aureus which is coagulate positive
What staphylococcus are present if the coagulate test is negative?
Staphylococcus epidermidis or staphylococcus saprophyticus
What proteins are present in staphylococcus aureus that disable our immune defense?
Protein A, coagulase, hemolysins, leukocidins, penicillin are, and novel penicillin binding protein
What proteins of staphylococcus aureus tunnel through tissue?
Hyaluronidase, staphylokinase, lipase, protease
What exotoxins are present in staphylococcus aureus?
Exfoliatin, enterotoxin, and toxic shock syndrome toxin
What is Exfoliatin?
Exotoxin of staphylococcus aureus
Causes skin to slough off (scalded skin syndrome)
What are enterotoxins?
Exotoxin of staphylococcus aureus
Cause food poisoning resulting in vomiting and diarrhea
What is toxic shock syndrome toxins (TSST-1)?
Exotoxin of staphylococcus aureus
More deadly that beta-hemolytic streptococci
Causes toxic shock syndrome
Pyrogenic toxin called a superantigen
What is the mechanism is Toxic shock syndrome?
Toxic shock syndrome toxin of staphylococcus aureus binds to the MHC Class II molecule on APC and causes massive T elk response and outpouring of cytokines causing symptoms
What are the symptoms of toxic shock syndrome?
Sudden onset of high fever, nausea, vomiting, watery diarrhea
Few days after- diffuse erythematous (red) rash
Palms and soles undergo fine peeling of the skin
Associated with septic shock
What diseases are caused by exotoxin release?
Gastroenteritis (food poisoning), toxic shock syndrome, scalded skin syndrome
What diseases result from direct organ invasion by staphylococcus aureus?
Pneumonia, meningitis, osteomyelitis, acute bacterial endocarditis, septic arthritis, skin infections, bacteremia/sepsis, urinary tract infection
What is the mechanism of gastroenteritis caused by staphylococcus aureus?
Staph. Aureus grows on food and releases exotoxin. Food is ingested and stimulates peristalsis causing nausea, vomiting, diarrhea, and abdominal pain that lasts 12-24 hours.
What is the mechanism of Toxic shock syndrome?
When tampons are left in place for a long time, Staph. Aureus is stimulated to release TSST-1. TSST-1 penetrates vaginal mucosa and stimulates TNF and IL-1
*men and nonmenstrating women can also be affected
What can cause toxic shock syndrome that is not related to tampon-use?
Infected surgical wounds, cutaneous and subcutaneous infections, and infections following childbirth or abortion can be the foci for staph. aureus to release TSST-1
What is Staphylococcal scalding skin syndrome and who does it affect?
Staph. aureus strain that produces exfoliatin toxin that usually affects neonates with local infection of recently severed umbilicus or older children with skin infection
What is the clinical presentation of staphylococcal scaling skin syndrome?
Cleavage of epidermis with fine sheets of skin peeling off to reveal moist red skin
What are the clinical manifestations of community-acquired bacterial pneumonia caused by staphylococcus aureus?
Abrupt onset of fever, chills, and lobar consolidation of the lung with rapid destruction of the lung parenchyma resulting in cavitations (holes) in the lung
What can be found in the pleural space in pneumonia from staphylococcus aureus?
Effusion and empyema (pus)
What are the clinical manifestations of patients with meningitis, celebrities, brain abscesses caused by staphylococcus aureus?
High fever, stiff neck, headache, obtundation, coma, and focal neurological signs
What are the clinical manifestations of osteomyelitis from staphylococcus aureus?
Bone infection usually in boys under 12 y/o
Warm, swollen tissue over the bone
Systemic fever
Shakes
What is the clinical presentation of acute endocarditis from staphylococcus aureus?
Sudden onset of high fever
Chills
Myalgias (bad flu)
What is the difference between acute endocarditis found in staphylococcus aureus vs streptococcus Viridans and group D streptococci?
Staphylococcus aureus- sudden onset
Streptococus Viridans and group D streptococci- more gradual onset
What is the clinical manifestation of septic arthritis caused by staphylococcus aureus?
Invasion of synovial membrane causes closed infection of joint cavity
Patient complains of acutely painful, red, swollen joint with decreased ROM
What is the most common pathogen that causes septic arthritis in pediatric age and in adults over 50?
Staphylococcus aureus
What would be the lab results of a patient with septic arthritis from staphylococcus aureus?
Synovial fluid is yellowish and turbid with huge number of neutrophils and a + gram stain
What is the difference in skin infections from Streptococus pyogenes and staphylococcus aureus?
Clinically impossible to differentiate the 2
What is the clinical manifestation of impetigo?
Infection occurs on face, especially around the mouth
Small vesicles lead to pustules that crust over and become honey-colored, wet and flaky
*from strep. or staph
What is cellulitis?
Deeper infection of cells that is hot, red, shiny and swollen
Cause by strep and/or staph
What is an abscess?
Collection of pus
What is the clinical presentation of an infection of the hair follicle?
Single, pus filled crater with a red rim
*caused by staph or strep
What is a furuncle?
An infection of a hair follicle that penetrates deep into the subcutaneous tissue
*skin manifestation of staph or strep
What must a physician do if the abscess is significant?
Surgically drain it
What is the clinical presentation of a blood and catheter infection caused by staph. aureus?
Bacteremia, sepsis, septic shock, and endocarditis
What is MRSA?
Methicillin-Resistant Staphylococcus Aureus
Where does MRSA most commonly develop?
In the hospital where broad spectrum antibiotics are used
How is MRSA transferred from patient to patient?
By hand contact of health care workers
What are the general characteristics of staphylococcus epidermidis?
Found in normal bacterial flora
Is coagulase-negative
Usually lives in skin without causing disease
When does staphylococcus epidermidis become pathogenic?
In compromised hospital patients with Foley urine catheters of intravenous lines that become infected when the organism migrates from skin along the tubing
How can staphylococcus epidermidis be harmful in prosthetics devices?
Cause infection by adhering to the prosthetic materials
Ex. Prosthetic joints, prosthetic heart valves, and peritoneal dialysis catheters
What is the leading cause of urinary tract infections (after E.coli)?
Staphylococcus saprophytius
Who is a staphylococcus saprophyticus infection common in?
Sexually active young woman
