GPC, HACEK, Spore-formers Flashcards
staph spp. characteristics
-skin & mucous membranes
-cocci in clusters
-gram pos
-no spores or flagella
-may have capsules (VISA)
MIC for staph spp.
MIC >2 & <8 is not considered officially resistant
-VISA is the range between 2 & 8 on E test
staph aureus
-large, round, opaque colonies
-facultative anaerobe
-can withstand high salt, ph, temp
staph aureus virulence factors
-hemolysins
-leukocidin: PVL produced from bacteriophage, PVL pos staph = deadly pneumonia
-enterotoxin: GI distress
-exfoliative toxin: epidermis from dermis
-TSST: fever, vomiting, shock, systemic organ damage
enzyme virulence of staph aureus
-coagulase
-hyaluronidase: digests connective tissue
-staphylokinase: digests blood clots
-DNAase
-lipases
-penicillinase: inactivates penicillin
local staphylococcal disease
-local to systemic
-localized cutaneous infections: invade through skin, wounds, follicles, or glands
*folliculitis
*furuncle- boil
*carbuncle- lesions from clusters of furuncles
*impetigo- bubble-like swelling (babies). herpes infection
systemic staphylococcal diseases
-osteomyelitis
-bacteremia (endocarditis)
toxigenic staphylococcal diseases
-food intoxication: heat stable enterotoxins, GI distress
-scalded skin syndrome: bright red flesh, blisters.
-TSS: shock & organ failure
other staphs
-epidermidis: skin & mucous membranes, endocarditis, UTI, bacteremia
-hominis
-capitis
-saprophyticus
ID of staph
-isolated from pus, tissue, sputum, urine & blood
-cultivation, catalase, biochemical testing, coagulase
catalase test
-staph is catalase pos
-strep is catalase neg
coagulase test
-coagulase pos: staph aureus
-coagulase neg: other staph spp.
MRSA
-methicillin resistant staph aureus
-contains mecA gene
-resistance to all beta-lactam antibiotics
general characteristics of strep
-gram pos, spherical/ovoid cocci in chains (pairs)
-non-motile
-can form capsules & slime layers
-facultative anaerobes
-catalase neg but have peroxidase system
-parasitic forms are fastidious
-small, non-pigmented colonies
-sens to drying, heat & disinfectants
alpha vs beta hemolysis in strep
-beta hemolysis; complete hemolysis (groups A, B, C, G, & D)
-alpha hemolysis; partial hemolysis (strep pneumoniae, viridans group strep)
strep pyogenes
-beta hemolytic
-most serious strep
-strict parasite
-inhabits throat & nose
virulence of strep pyogenes
-C-carbohydrates: protect against lysozyme
-fimbriae: adherence
-M protein: resistance to phagocytosis
-hyaluronic acid capsule: provokes no immune response
beta hemolytic strep pyogenes virulence factors
-streptolysin: hemolysins, SLO & SLS cause cell & tissue injury
-pyogenic toxin: fever & rash
-superantigens: mono & lymph stimulants- tissue necrotic factor
impetigo
superficial lesions that break & form highly contagious crust. epidemics in schools- associated with insect bites, poor hygiene, & crowded living conditions
erysipelas
pathogen that enters through a break in the skin and eventually spreads to the dermis & subcutaneous tissue
strep pharyngitis
strep throat
strep clinical disease
systemic infections:
-scarlet fever; strep pyogenes carrying a prophage that codes for pyrogenic toxin
-septicemia
-pneumonia
-streptococcal toxic shock syndrome
long term complications of group A strep
-rheumatic fever: manifests as carditis with extensive valve damage, arthritis, chorea, fever
-acute glomerulonephritis: increased bp, heart failure, chronic leading to kidney failure
group B strep
-normal human flora
-can be transferred to child during birth
-most prevalent cause of neonatal pneumonia, sepsis & meningitis
-33% fatal in infants
group D strep
-enterococcus faecalis, faecium, durans
-strep gallolyticus; colon cancer
-opportunistic
endocarditis
subacute bacterial endocarditis
-preexisting heart disease at high risk
-colonization of heart by forming biofilms
-meningitis
-intra-abdominal infections
-gingivitis & dental abscesses
strep pneumoniae
-60-70% of all bacterial pneumonias
-small, lancet shaped cells in pairs & chains
-blood or chocolate agar
-die in O2
-all pathogenic strains form large capsules
-alpha hemolytic & P disk
viridan strep
-oral or bowel flora
-alpha (green) hemolytic