Cocci Flashcards
cocci
- spherical
- 1 micron diameter
- non-spore forming
- human restricted
- gram staining
- twos, chains, clumps
- alpha,beta,gamma hemolytic
- strep, staph, neisseria
streptococci
- gram positive
- catalase negative
- grows in chains
- classified by Lancefield or hemolytic abilities
- cell wall has pili
Group A strep
- sore throats
- gram positive
- beta hemolytic
- sensitive to bacitratcin
- reacts to group A antiserum, rapid test to carb antigen but false negatives are common
- S. pyrogenes
Lancefield classification
-based on carbohydrate antigens found in the cell wall
group A virulence
- pili-pathogenicity island
- M protein
- streptokinase
- streptodornase
- hyaldronidase
- pyrogenic toxin
- erythrogenic toxin
reservoir and transmission of group A
- spreads from oropharynx to tonsils/floor of mouth or to middle ear/mastoids/meninges
- reservoir is carriers
- transmitted by direct contact
post strep conditions
- skin infection from M49-pain, blood and protein in urine-post strep nephritis
- sore throat from M18-fever, arthritis, endocarditis-rheumatic fever
- occur after infection
- lesions are sterile (but there are antibodies in blood)
- sydenhams chorea-neurological symptoms
Group B strep
- gram pos, catalase neg, beta hemolytic, resistant to bacitracin, positive CAMP test, reacts to Group B antiserium
- S. agalactiae
Group B virulence
capsule-prevents phagocytosis
reservoir and transmission
- genital tract of 25% of women
- neonatal to baby- can lead to meningitis
prevention of group B CDC recommendations
- offer penicillin prophylaxis to pregnant women is
- vaginal/rectal swab shows group B at 35 weeks or previous baby with group B
- fever
- membranes ruptured for over 18 hours
S. pneumoniae
- pneumococci, dipplococci
- gram pos, catalase neg, alpha hemolytic, sensitive to bile
virulence of pneumococci
- capsule-prevents phagocytosis
- antigen as well, stimulates opsonization
- 80 types
- basis of typing sera and vaccines
- basis of polyvalent antibody reaction-quellung
*reservoir-5-50% of throats
pathogenesis of bacterial pneumonia
- natural resistance to lung infection from mechanical clearance by mucus/cilia
- inhibition of mechanical clearance leads to disease
- smoking
- virus
- allergy
- immobility
- mechanical-tumors/foreign bodies
- depressed cough reflex-alcohol/narcotics
- L sided heart failure
management of bacterial pneumonia
- offer vaccine to susceptible groups
- identify and treat the underlying cause
- antibiotic sensitivity tests
- antibiotics
S viridans
-gram pos, catalse neg, alpha hemolytic, bile resistant
reservoir and transmission of S viridans
- mouth- 100%
- transmission from person to person
virulence of S viridans
- sugar metabolizing enzymes
- some increase MW, dental plaque, bactermia and endocarditis
- others break down to acids-decalcification
- bacteremia managed by prophylactic antibiotics at dentist
enterococcus fecalis
- gram pos, catalase neg, gamma hemolytic, resistant to bile, or reacts to group D antiserum
- normal flora of colon
- resistant to penicillin-use penicillin and aminoglycosides
peptostreptococcus
- gram pos, catalase neg, gamma hemolytic, sensitive to bile
- found in abscesses with a mixture or organisms, not primary pathogens
- normal flora of mouth, resp tract, female genital tract, bowel
staphylococci
- gram positive
- catalase positive
- accumulated mutations
- 6 resistance genes, at least 8 strains in existence now
S. aureus
- gram pos, catalase pos, coagulase pos, beta hemolytic
- phage typing or DNA typing
virulence of S aureus
- protein A-binds immunoglobulins
- capsule-prevents phagocytosis
- coagulase-makes things clot
- DNAse
- Enterotoxin
- Exfoliatin
- Leukocidin
- TSS Toxin
- MRSA
reservoir and transmission of S aureus
- carriers on nose and skin
- direct contact with infected person or carrier, or indirectly by fomites
prevention and treatment of S aureus
- wash hands, cover lesions, food hot, remove carriers from ICU, OR, nurseries, isolate, treat carriers
- drain abscesses to remove dead tissue and bacteria
- antibiotics-use penicillin pr oxacillin, methicillin
- MRSA use vancomycin
S epidermidis
- gram pos, catalase pos, coagulase neg
- gamma hemolytic
- normal flora of skin and mucous membranes
- attaches to nylon and plastic- can infect IV caths, IV lines, shunts
prevention and treatment of S epidermidis
- change catheters on schedule
- use gold or surgical stainless steel for decorative piercings
- peripheral catheters-72-96hrs
- emergency caths-within 48 hours
- iv tubing 72 hrs
- blood transfusion sets-within 24 hrs
S saprophyticus
- gram pos, catalase pos, non hemolytic, coagulase neg
- can cause UTI
gram neg cocci
- chocolate agar
- add to maltose
- fermentation is N. meningitidis, no fermentation is N. gonnorhoeae
N. meningitidis
gram neg, fermentation pos
- capsule (vaccine), LPS
- resp tract of 5% of people, transmitted by droplets
- vaccine/penicillin
N. gonorrghoeae
- gram neg, fermentation neg
- pili, LOS
- can be found in neutrophils
- sexual or neonatal transmission
- chronic infection may be asymptomatic
- ceftiaxone and doxycyline
- usually resistant to penicillin
- no vaccine
