Chapter 10-11 Intro Staphylococcus Flashcards
what do the different gram stains reflect
a fundamental differentiation based on permeability, presence or absense of outer membrane and cell wall thickness
what are the 4 typical cell types
- gram positive rods
- gram positive cocci
- gram negative rods
- gram negative cocci
do gram positive rods have more in common with gram positive cocci or gram negative rods
gram positive cocci
what group does staphylococci fall under
gram positive cocci
what group does streptococci fall under
gram positive cocci
where are staphylococci found and what type of infections is it associated with
-skin infections and wounds
- carbuncles
-abscesses
-leading to life threatening deep tissue infections
-osteomyelitis
-endocarditis
- severe intoxications
-food poisoning
what are the groups of streptococci and what do they do
-alpha: S. pneumoniae
-beta: groups A-T, group A most prevalent in human disease
describe the type of microbe streptococci id
oxygen tolerant anaerobes
what are the major gram negative cocci
-neisseria meningitidis
- neisseria gonorrhea
what are the major gram positive rods
- non spore forming aerobic rods - corynebacterium diptheriae and related diptheroids
- spore forming rods
what are the aerobic spore forming rods of gram positive rods
bacillus anthracis
what are the anaerobic spore forming rods of gram positive rods
- clostridium species
- c. botulinum, c. tetani, c.perfringens, c. difficile
what are the major gram negative rods
- enteric bacteria
- enterobacteriaceae
-escherichia coli, salmonella spp, shingella spp, yersinia, pseudotuberculosis - vibrio cholerae, camyplobacter jejuni, helicobacter pylori
what are the major non-enteric gram negative rods
- pseudomonas aeurginosa
-haemophilus influenzae - bordetella pertussis
- brucella abortus
- legionella penumophila
what type of microbe is enterobacteriaceae
facultative anaerobes
what are the strictly anaerobic gram negative rods
bacteroids gragilis
where is bacteriodes fragilis found
-most common organism in the intestine
- gingival pockets
example of acid fast bacteria
mycobacterium tuberculosis
- M. leprae
what are examples of spriochetes
-treponema pallidum (syphilis)
- leptospira spp (hemorrhagic fever)
- borrelia recurrentis ( relapsing fever)
- borrelia burgdorferi (lyme disease)
what are the strictly intracellular bacteria
- chlamydia trachomatis
- chlamydia pneumoniae
- rickettsiae (rocky mountain spotted fever)
- ehrlichia (arthropod borne)
- coxiella burnetti (Q fever)
what is the most common STD
chlamydia trachomatis
what are the characteristics of staphylococcus
-gram positive cocci
- catalase positive
what type of microbe is staphylococcus aureus and what does that mean about O2
facultative anaerobe
- O2 can be used
what does a catalase do
reduced the potential of phagocytes to kill
what does a coagulase do
binds prothrombin: fibrinogen is cleaved -> anti-phagocytic fibrin coating
the tissue invasive potential of staphylococcal infections is directly proportional to ______
coagulase proudction
what does clumping factor do
fibrinogen binding protein: cell surface proteins that bind to foreign materials and ECM
what does protein A do
anti-phagocytic
- competes with neutrophils for Fc protion of opsonizing IgGs
what does leukocidin do
secretion: inhibits phagocytosis by granulocytes by forming pres in phagosomal membranes and kills phagocytes
what does staphylokinase do
converts plasminogen to plasmin, increasing invasion by digesting fibrin clots and cleaves C3b and IgG to inhibit phagocytosis
what does beta lactamase do
enzymatic digestion of penicillins
what do alpha hemolysins do
pores are hemolytic, leukocytic, destroy skin, cause smooth muscle paralysis
what do beta hemolysins do
- beta hemolysins are cytolytic sphingomyelinases that destroy nerves
what do gamma hemolysins do
lyse related leukocicin on neutrophil lysosomal membranes
does staph aureua do hemolysis
yes beta
does staph epidermidis do hemolysis
no
what microbe causes impetigo
S. aureus
what is empyema
collection of pus in a naturally existing anatomical cavity
what are pyogenic infections and wjat is it caused by
pus forming
- massive amounts of neutrophils and other leukocytes are lysed by bacterial factors and release their lysosomal contents in attempting phagocytic killing of the staphylococci
how does bacteremia fever progress
folliculitis -> furuncles -> carbuncles
-> systemic bacteremia fever
what do superantigens do
override the specificity of the T cell response
what is the cause of gastrointestinal upset typical of food poisoning
enterotoxins
what happens in toxic shock syndrome
- TSST: mass activation of T cells leads to large production of inflammatory cytokines
are enterotoxins heat stable
yes cooking doesnt help
describe exfoliative toxin
heat stable, chromosomal
describe exfoliative toxin B
heat labile, plasmis
what is Toxic shock syndrome caused by
increased oxygenation of vagina by tampons and foreign surface adhesion caused massive growth
what is staphylococcal scalded skin syndrome caused by and what is it
-exfoliative toxins A, B
- causes loss of layers of the skin
when is nosocomial staphylococci of concern
surgery, implant and instrument risk
what type of microbe is a nosocomial infection caused by
coagulase negative S epidermidis
what microbe causes endocarditis
- acute: 60% S aureus
- if artificial heart vavles 80% S. epidermidis
what microbe is involved in dental extraction risk
S epidermidis
what is the most frequent cause of bacterial arthritis
S. aureus
what is the epidemiology of staphylococcus aureus
- skin + mucosa + aerosols
- surface survival - nosocomal
- high temperature and salt resistant
how many beta lactamase (plasmid) are penicillin resistant
> 90%
what causes methicillin resistance
penicillin binding protein 2a
what percentage of hospital strains of staph aureus are MRSA
50%
what percentage of community strains are MRSA
20%
what are the coagulase negative staphylococci
S. epidermidis or S. saprophyticus
describe the coagulase negative staphylococci
- thick cell wall, slime capsule: S. saprophyticus: urease secretion -> acute cystitis
- opportunistic hospital pathogens
