Staphylococcus aureus Flashcards
What are the two types of patients?
Normal Patient
Patient with compromising or predisposing factors
Patients with compromising or predisposing factors are due to these 5 things?
Surgery or trauma
Immunoincompetence or immunosuppression
Diabetic
Alcoholism or drug use
Pregnancy
What are the two modes of infection acquisition? (two ways you acquire infectious disease)
Community acquired
Hospital acquired
What are the three geographic distribution and/or “work” environments?
(places to acquire infections?)
Insect vectors/ climate
Farm & ranch
Construction Work
Is Staphylococcus aureus gram + or gram -?
Gram +
Cocci in clusters
What causes about 90% of invasive tissue infections?
Staphylococcus aureus
True/ False
Staphylococcus aureus pyogenic
True
What is folliculitis?
What microbe causes this?
Infection of the hair follicle
Staphylococcus aureus
What is a furnuncle? What microbe causes this?
Deep seated infections (subcutaneous tissue involved) in and around the hair follicle.
Staphylococcus aureus
What is cellulitis? What microbe causes this?
Similar to folliculitis/boils in skin or tissues but spreads beneath the skin.
Staphylococcus aureus
What is impetigo? What microbe causes this?
Superficial skin infection characterized by small “blisters”/pustules followed by a thin crust over the area
Staphylococcus aureus
Staphylococcus aureus is the etiologic agent of?
Invasive tissue infections Food poisoning Toxic Shock Syndrome Scalded Skin Syndrome Septicemia/bacteremia Bone and joint infections Pneumonia/Lower Respiratory & Lung Abscess infections
Staphylococcus aureus can cause this especially after surgery or trauma often due to external contamination?
Wound and internal tissue infections (abscess)
Staphylococcus aureus can cause this due to numerous invasive enzymes and toxins.
Tissue damage. Some invasive infections can be very severe.
Staphylococcus aureus food poisoning is due to ingestion of this?
pre-formed heat-stable enterotoxin. Its an enterotoxin that affects the intestinal tract (types A,B,C, etc SEB).
What are the commonly affected foods of Staphylococcus aureus that causes food poisoning?
Cooked or processed meat (especially ham), salads, and cream filled desserts.
What are the clinical symptoms of food poisoning caused by Staphylococcus aureus
Nausea
Vomiting
Abdominal cramps
Watery diarrhea
Food poisoning symptoms of Staphylococcus aureus start within how many hours and last to about how many hours?
Starts within 1-6 hours and lasts from a few hours to about 24 hours.
True or False
Staphylococcus aureus growth on food produces no change in flavor or odor.
True
Food Poisoning:
What are the conditions Staphylococcus aureus (certain strains) will produce enterotoxin?
When growing at 28C or higher for 2 to 4 hours.
Certain strains of Staphylococcus aureus produce Toxic Shock Syndrome Toxins (TSST). The TSST toxin probably causes?
Massive and unregulated stimulation of the immune system.
TSST produces what symptoms?
Acute illness with: High fever Diffuse rash Hypotension Skin desquamation
What is TSST infection normally associated with?
Use of highly absorbent tampons (about 75% of cases) or with focal or surgical wound infections in men or non-menstruating women.
In TSST, how does the tampon cause infection?
Absorption of fluids causes change of microbial growth environment resulting in change or host-microbe dynamics.
True or False
TSST test for toxins is usually performed in routine microbiology labs.
False
What does Scalded Skin Syndrome cause in children under 5?
Toxic Epidermal Necrolysis (TEN)
Strains of scalded skin syndrome produce what kind of toxins? and they are destructive to?
Exfoliatin Toxins
Destructive to epithelial cells
What are the symptoms of Toxic Epidermal Necrolysis in children under 5?
Initially a localized red rash, often following conjunctivitis or upper respiratory tract infection.
Followed by large flaccid bullae.
The bullae of scalded skin syndrome do what?
Rupture and sheets of epidermis peel off to reveal moist, red, “scalded” dermis.
True or False
Bacteria are recovered from the bullae and not from the initial infection.
False
Staphylococcus aureus
Bloodstream infection resulting from deep, poorly draining infections which invade the bloodstream and spread to numerous body sites.
Septicemia/
Bacteremia
Is septicemia/bactermia life-threatening?
Yes, unless rapidly treated with effective antimicrobics.
Staphylococcus aureus:
These infections are common following device implantation or trauma.
Bone and joint infections (osteomyelitis & septic arthritis)
Staphylococcus aureus:
This can happen following viral respiratory infections or in patients with altered host defenses.
Pneumonia/ Lower Respiratory & Lung Abscess infections (about less than 2% of all pneumonia)
What are the virulence factors of Staphylococcus aureus
Several toxins & invasive enzymes, including coagulase, fibrinolysis, lipase and a variety of proteases
Adhesive Matrix Molecules
Quorum-sensing regulators
Super antigens (toxins)-enhance effects of toxins
Pathogenicity of various strains is largely due to genes carried on plasmids and lysogenized viral genes.
Resistant to multiple antimicrobics
What antimicrobics are Staphylococcus aureus resistant to?
Beta-lactams (85%)
Vancomycin (developing- VISA, VRSA)
And probably others
Why are most strains of Staphylococcus aureus resistant to Beta-lactams?
Due to beta-lactamase enzymes coded by genes carried on plasmids.
What are Multiply Drug Resistant (MDR)?
Strains (of Staphylococcus aureus?) that are resistant to an exceptionally large number of antimicrobic types. - very serious infections.
What is an example of the drug combo for MRSA?
Vancomycin, linezolid, & tigecycline
What are some of the laboratory work done for a laboratory diagnosis?
Culture and biochemical identification- coagulase positive
Antigenic identification/confirmation of the lab culture.
Antimicrobic susceptibility test needed (Beta-lactamase, MRSA, MDR)
