03 - Gram + cocci - Staphylococcus aureus, epidermidis, saprophyticus, Flashcards
What are the Factors to Consider in the Determination of a Pathogen?
Types of patients
Mode of infection acquisition
Geographic distribution and/or “work” environment
- Types of patients
a. Normal patient b. Patient with compromising or predisposing factors
(1) Surgery or trauma
(2) Immunoincompetence or Immunosuppression – e.g. cancer or AIDS patient
(3) Diabetic
(4) Alcoholism or drug use
(5) Pregnancy
- Mode of infection acquisition
a. Community acquired
b. Hospital acquired – Nosocomial infection
- Geographic distribution and/or “work” environment
a. Insect vectors / climate
b. Farm & ranch
c. Construction work
Two Types of patients? Examples of second type?
a. Normal patient b. Patient with compromising or predisposing factors
(1) Surgery or trauma
(2) Immunoincompetence or Immunosuppression – e.g. cancer or AIDS patient
(3) Diabetic
(4) Alcoholism or drug use
(5) Pregnancy
What are two Modes of infection acquisition?
a. Community acquired
b. Hospital acquired – Nosocomial infection
- Geographic distribution and/or “work” environment
a. Insect vectors / climate
b. Farm & ranch
c. Construction work
Describe Staphylococcus aureus
a. Gram-positive cocci in clusters
b. Large, yellowish beta hemolytic colonies
Staphylococcus aureus is an Etiologic agent of:
- Invasive tissue infections
- Food Poisoning
- Toxic Shock syndrome
- Scaled skin syndrome
- Septicemia / bacteremia
- Bone and Jone infections
- Pneumonia / Lower Respiratory & Lung Abscess Infections
Describe Staphylococcus aureus as an invasive tissue infection:
? % of invasive tissue infections along with?
P F F C I W T
(THINK OF BETTER ACRONYM)
causes about 90% of invasive tissue infections (along with group A Streptococcus)
(a) ** Pyogenic = Pus- producing = Abscess forming
(b) Folliculitis - infection of the hair follicle
(c) Furuncles (boils) - deep seated infections (subcutaneous tissue involved) in and around the hair follicle
(d) Cellulitis – similar to folliculitis/boils in skin or tissues but spreads beneath the skin
(e) Impetigo - superficial skin infection characterized by small “blisters”/pustules followed by a thin crust over the area
(f) Wound and internal tissue infections (abscess) - especially after surgery or trauma; often due to external contamination
(g) Tissue damage due to numerous invasive enzymes and toxins. Some invasive infections can be very severe.
Describe Staphylococcus aureus as a Food poisoning:
due to ingestion of _______
(a) Certain strains of bacteria produce enterotoxin when growing at ___ or higher for _ to _ hours
(b) Commonly affected foods are ____________
(c) Bacterial growth on food produces ________
(d) Clinical symptoms: nausea, vomiting, abdominal cramps, and watery diarrhea within 1 to 6 hours; lasts from a few to about 24 hours
due to ingestion of pre-formed heat-stable enterotoxin (an exotoxin that affects the intestinal tract) (types A, B, C, etc, e.g. “SEB”)
(a) Certain strains of bacteria produce enterotoxin when growing at 28C or higher for 2 to 4 hours
(b) Commonly affected foods are cooked or processed meat (especially ham), salads, and cream-filled desserts
(c) Bacterial growth on food produces no change in flavor or odor
(d) Clinical symptoms: nausea, vomiting, abdominal cramps, and watery diarrhea within 1 to 6 hours; lasts from a few to about 24 hours
Describe Staphylococcus aureus as Toxic shock syndrome:
(a) Certain strains produce Toxic Shock Syndrome Toxins (TSST) (____ mediated) - toxin probably causes massive and unregulated stimulation of the immune system
(b) Produces acute illness with high fever, diffuse rash, hypotension, and skin desquamation (1-2 weeks after onset), plus several other features
(c) Infection associated with use of highly absorbent _____ (about 75% of cases) (absorption of fluids causes change of microbial growth environment resulting in change of host-microbe dynamics) or with focal or surgical wound infections in men or non-menstruating women
(d) Tests for toxin usually not performed in routine microbiology labs
(a) Certain strains produce Toxic Shock Syndrome Toxins (TSST) (plasmid mediated) - toxin probably causes massive and unregulated stimulation of the immune system
(b) Produces acute illness with high fever, diffuse rash, hypotension, and skin desquamation (1-2 weeks after onset), plus several other features
(c) Infection associated with use of highly absorbent tampons (about 75% of cases) (absorption of fluids causes change of microbial growth environment resulting in change of host-microbe dynamics) or with focal or surgical wound infections in men or non-menstruating women
(d) Tests for toxin usually not performed in routine microbiology labs
Scalded skin syndrome
(a) Certain strains produce exfoliatin toxins – destructive to epithelial cells
(b) Causes _______ in children under 5 yr
i. Initially a localized red rash, often following conjunctivitis or upper respiratory tract infection
ii. Followed by large flaccid _____ which rupture and sheets of epidermis peel off to reveal moist, red, “scalded” dermis
(c) Bacteria are not recovered from the bullae; only from the initial infection
(a) Certain strains produce exfoliatin toxins – destructive to epithelial cells
(b) Causes Toxic Epidermal Necrolysis (TEN) in children under 5 yr
i. Initially a localized red rash, often following conjunctivitis or upper respiratory tract infection
ii. Followed by large flaccid bullae which rupture and sheets of epidermis peel off to reveal moist, red, “scalded” dermis
(c) Bacteria are not recovered from the bullae; only from the initial infection
Septicemia/bacteremia – ________ infection resulting from _____________ which invade the bloodstream and spread to numerous body sites – typically life-threatening unless rapidly treated with effective antimicrobics
bloodstream
deep, poorly draining infections
Pneumonia / Lower Respiratory & Lung Abscess infections (less than about 2% of all pneumonias), especially following ______
viral respiratory infections or in patients with altered host defenses
The following are common with:
- Invasive tissue infections
- Food Poisoning
- Toxic Shock syndrome
- Scaled skin syndrome
- Septicemia / bacteremia
- Bone and Jone infections
- Pneumonia / Lower Respiratory & Lung Abscess Infections
(THINK OF ACRONYM)
Staphylococcus aureus
Virulence factors of Staphylococcus aureus:
(1) Several toxins & invasive enzymes, including ____, ____, _____, and a variety of ______.
(2) Adhesive Matrix Molecules – produce biofilms
(3) Quorum-sensing regulators
(4) Superantigens (toxins) – enhance effects of toxins
(5) Pathogenicity of various strains is largely due to genes carried on _____ and ______________.
(6) Resistant to multiple antimicrobics
(1) Several toxins & invasive enzymes, including coagulase, fibrinolysin, lipase, and a variety of proteases.
(2) Adhesive Matrix Molecules – produce biofilms
(3) Quorum-sensing regulators
(4) Superantigens (toxins) – enhance effects of toxins
(5) Pathogenicity of various strains is largely due to genes carried on plasmids and lysogenized viral genes.
(6) Resistant to multiple antimicrobics
Beta-Lactamase, MRSA, VRSA, MDR, etc
Staphylococcus aureus is Resistant to multiple antimicrobics
(a) _________ – Most strains (e.g. 85%) are resistant to most beta- lactam antibiotics (penicillins and cephalosporins) due to beta-lactamase enzymes coded by genes carried on plasmids.
(b) _____ (about 30%, percentage increasing) – Resistant to all beta-lactam antibiotics due to mutated penicillin- binding proteins
(c) ______ resistance developing (e.g. VISA, VRSA)
(d) ________ – strains that are resistant to an exceptionally large number of antimicrobic types – Very problematic and serious infections.
(e) [Treatment of MRSA – e.g. vancomycin, linezolid, & tigecycline]
(a) Beta-lactamase (penicillinase) – Most strains (e.g. 85%) are resistant to most beta- lactam antibiotics (penicillins and cephalosporins) due to beta-lactamase enzymes coded by genes carried on plasmids.
(b) Methicillin Resistant Staphylococcus aureus (MRSA) (about 30%, percentage increasing) – Resistant to all beta-lactam antibiotics due to mutated penicillin- binding proteins
(c) Vancomycin resistance developing (e.g. VISA, VRSA)
(d) Multiply Drug Resistant (MDR) – strains that are resistant to an exceptionally large number of antimicrobic types – Very problematic and serious infections.
(e) [Treatment of MRSA – e.g. vancomycin, linezolid, & tigecycline]
