Exam 4: Intro and Gram + cocci Flashcards
What is exotoxin?
it is secreted by gram + or - bacterium not the surround fluid following lysis of bacterial cell. bacteria must colonize tissue to produce enough exotoxin to be harmful
Most exotoxins are proteins. What does this mean?
- the immune system can produce antibodies
- they are denatured by heat
Exotoxins are released by every gram _____ (+ or -) genera except ______.
+, listeria
exotoxins have specific targets and usually do not cause ____ or ____.
fever or generalized inflammation
Type of exotoxin that acts on nerves or motor endplates to cause paralysis
neurotoxin
type of exotoxin that acts on gastrointestinal tract to cause diarrhea
enterotoxin
type of exotoxin that causes damage to a variety of cell types by either interfering with cell mechanisms or causing cell lysis
cytotoxins
What is endotoxin?
Lipid A, the toxin portion of the lipopolysaccharide which is part of the outer membrane of gram - bacteria
The immune response to endotoxin is due to _____.
innate immune response
*this means there is no specific target
Can endotoxins be destroyed by heat?
no, they are heat stable
What are the major categories of gram positive cocci?
- staphylococcus
- streptococcus
Which of the staphylococcus species has a golden pigment?
staph aureus
*Aureus is a gold coin of ancient rome
How do you differentiate between staph aureus and staph epidermidis in order to make a diagnosis?
staph aureus is coagulase positive while staph epidermidis is coagulase negative
Which of the staphylococcus species is an opportunistic pathogen?
staph epidermidis
What bacterial species causes the following pathogenesis:
- furuncles, carbuncles and build
- folliculitis
- toxic shock syndrome
- scalded skin syndrome
- pneumonia
- osteomyelitis
- MRSA
staph aureus
Why is treatment of staph infections (both aureus and epidermidis) so difficult?
both species produce penicillinase and so are resistant
Are the gram positive cocci (staphylococcus and streptococcus) part of normal flora?
yes
What bacterial species is part of the normal flora of female genital tract?
streptococcus agalactiae
How are streptococci species classified?
by hemolysis patterns - how they rupture or destroy red blood cells
hemolytic pattern in which there is partial hemolysis with green cast around colonies of bacteria?
alpha hemolytic
hemolytic pattern in which there is complete hemolysis creating clear area around colonies
beta hemolytic
hemolytic pattern in which there is no hemolysis
gamma hemolytic
lance field groups are sometimes used to classify what bacteria?
streptococci
the more inclusive way to classify strep is to divide into 4 groups:
- lactic streptococci (non pathogenic, gamma hemolytic)
- fecal streptococci (enterococci)
- viridans streptococci (alpha hemolytic, tooth decay)
- beta hemolytic streptococci
what is the major streptococcal pathogen?
strep pyogenes
identifying features of strep pyogenes?
- produces pyrogenic exotoxin
- has a hyaluronic acid capsule
- has fibrils called M protein on cell surface
What bacterial species causes the following pathogenesis:
- pharyngitis
- impetigo
- cellulitis
- erysipelas AKA st. Anthony’s fire
- scarlet fever
- rheumatic fever
- glomerulonephritis
strep pyogenes
What gram positive cocci species are beta hemolytic
strep pyogenes
strep agalactiae
What is the hemolytic pattern of strep pneumoniae?
alpha hemolytic
What bacterial species is an important cause of neonatal meningitis, pneumonia, sepsis that leads to high mortality rate?
strep pneumoniae
What bacterial species has a major virulence factor of a polysaccharide capsule?
strep pneumoniae
If strep pneumoniae is part of the normal flora, how does it cause infection?
if invasive strain moves to lower lungs, it can cause pneumonia
other than pneumonia, what other pathologies can strep pneumoniae cause?
meningitis, otitis media, sinusitis
How is the strep pneumoniae diagnosis made?
Quellung reaction
