MIP: Gram Positive Pathogenic Bacteria Flashcards
What TLR detects peptidoglycan and lipoproteins in Gram + bacterial cell walls?
2
What TLR detects flagella?
5
What are the major subdivisions of the Gram Positive Cocci?
Staphylococcus, Streptococcus, and Enterococcus facalis
Why can’t acid-fast organisms be Gram stained?
They have lipoarabinomannan (LAM) in their cell walls
Why are acid-fast bacteria difficult to treat?
They have a very slow doubling time and they have a high mutation rate and LAM
Where is Staph aureus found?
It is part of normal and transient flora in humans and is foudn in moist pllaces (skin, armpit, nasopharynx, nares, groin)
Why is S. aureus an apt name?
Many strains produce the anti-oxidative gold pigment, staphoxanthin
What hemolysis pattern is seen with S. aureus?
Beta-hemolysis
What is the action of coagulase?
Converts fibrinogen to fibrin and coagulates plasma
True or False: Coagulase is found in all Staphylococcus bacteria.
False- not in epidermis or saprophyticus
What is the selectivity and differential capacity of a mannitol agar plate? How will S. aureus streak?
The selective component is salt, and the differential components are mannitol and phenol red; S. aureus turns the plate from red to yellow
What is the spectrum of disease that is caused by S. aureus?
Boils, furnicules, styes, impetigo, osteomyelitis, cellulitis, mastitis, UTIs, acute endocarditis, meningitis, TSS, food poisoning, scaleded skin syndrome, pneumonia, empyema, septic arthritis
What host factors increase susceptibility to Staph aureus infection?
Breaches in the skin, immunological defects, foreign bodies, close quarters coupled with poor hygiene, previous damage to tissues
How does S. aureus’s Protein A work?
It binds to the Fc portion of IgG and prevents its binding to phagocyte and facilitating of phagocytosis
What is an abscess?
Collection of pus (caused by neutrophil degranulation)
What is a furuncle? A carbuncle?
A furuncle is an abscess into subcutaneous tissue and a carbuncle is multiple contagious abscesses
How do you treat abscesses, furuncles, and carbuncles?
Incising the wound, draining it, and antibiotic therapy
What S. aureus toxin causes hemolysis and necrosis of the skin?
Alpha toxin
What is cellulitis?
Infection of subcutaneous layers of skin
What is Scalded Skin Syndrome?
Charecterized by fever, large bullae, and an erythematous macular rash, all induced by epidermolytic exotoxins (exfoliatin A and B) which are proteases that cleave desmoglein-1 and can cause detachment within the epidermal layer
What is Impetigo?
A very contagious infection in which small vesicles develop into pustules which crust over to become honey-colored and flaky
What is the cause of food poisoning?
Staph contaminates food and secretes enterotoxins (SEA, SEB, SEC1) stimulating the vagus nerve endings in the stomach and causing super-antigen effects that result in excess of IL-2
What is the cause of toxic shock syndrome?
The secretion of TSST-1 by Staph that acts as a super-antigen
What are the symptoms of Toxic Shock Syndrome?
Fever, nausea, vomiting, and diarrhea followed by rash and exfoliation–> blood pressure drops, Multi System Organ Failure, death
How can S. aureus cause osteomyelitis and endocarditis?
S. aureus can hijack a neutrophil by resisting destruction following phagocytosis, and it is safe from antibiotics and now can be spread through the neutrophil throughout the body
What are the symptoms and signs of Pediatric Osteomyelitis?
Limp, bone pain, fever, leukocytosis, and elevation of erythrocyte sedimentation rate and C-reactive protein
What is the leading cause of pediatric septic joints?
Staph aureus
What is a Brodie abcess?
Subacute osteomyelitis where the abcess becomes surrounded by bone tissue
What is infective endocarditis? What is the difference between acute and chronic?
Inflammation of heart valves or around congenital heart defects that shows up as bacteremia and fever from colonization of a valve; Acute is due to staph aureus and more severe presenting than chronic, which is caused by coagulase-negative staph infections
What is Panton-Valentine leukocidin?
A protein made by staph in the lungs that forms pores in cells that line the alveolar space, allowing fluid to accumulate inside of the tissue. PVL also causes activation of PMNs and macrophages and PMN necrosis– causes hemorrhagic, necrotic pneumonia
How does Staph epidermis appear on sheep blood agar?
Small white non-hemolytic colonies
True or False: Staph epidermis is coagulase negative and catalase positive
True
How could you chemically distinguish between a Staph and Strep infection?
Staph will bubble in hydrogen peroxide and strep does not
Where can staph epi be found?
Plastic catheters and tubing, septicemia, endocarditis
What are the hemolysis patterns that are exhibited by strains of Streptococcus?
Alpha hemolysis (erythrocytes not destroyed, but greenish discoloration due to organisms’ effect on hemoglobin; Beta-hemolysis (erythrocyte destruction); gamma hemolysis (non-hemolytic)
What are Lancefield Classifications based on?
Antigenic variation of C-carbohydrates and Glycerol Teichoic Acid
Bacitracin can be used to distinguish what two types of Strep?
Group A from Group B
What Group is Streptococcus pyrogenes?
Group A
What are the hallmarks of pharyngitis?
Fever, cough, pain, and pus
What is pharyngitis?
Pharyngeal inflammation and petechiae of soft palate, tonsils, with possible hard palate involvement
What is the algorithm for diagnosing strep?
If more than one of the following criteria are met (tonsilar exudates, tender cervical adenopathy, absence of cough, fever) then do a rapid strep test. If the test is positive then treat with antibiotics
What are the Streptococcal Pyrogenic Exotoxins?
SpeA, SpeB, and SpeC
What is Scarlet fever and what is its cause?
A bacterial illness that often [resents with a distinctive rash made up of tiny pink-red spots that cover the whole body and it is caused by SpeA by Group A Strep
How can acute rheumatic fever be part of post-streptococcal sequelae?
A region of the M protein shares some epitope with heart muscle–> molecular mimicry
What are the theories of the pathophysiology of Post-Streptococcal glomerulonephritis?
IgG-streptococcal antigen complexes depositing on glomerular tissue or Cross-reactivity between unidentified strep antigens and glomerular membrane components
