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
human bite and the organism pits sheep blood agar
Eikenella corrodens
HACEK acronym
-fastidious gram neg cocccobacillary organism
-Haemophilus aphrophilus (not true haemophilus- does not need X or V)
**now called Aggregatibacter aphrophilus
-Aggregatibacter spp
-cardiobacterium hominis
-Eikenella corrodens
-Kingella spp
frequently affect damaged valves & case emboli
infective endocarditis
-majority of cases caused by strep, staph, enterococcus, or fastidious gram neg cocco-bacillary
-staph aureus causes most cases of IE
HACEK general characteristics
-slow growing
-fastidious
-gram neg bacilli
-require increased CO2 (5-10%)
-usual flora in oropharyngeal cavity
-opportunistic in immunocompromised patients
HACEK clinical significance
-IE
-peridontal disease
-dental caries
-infections following dental procedures
lab ID for aggregatibacter (haemophilus) aphrophilus
-small convex white-grey, non-hemolytic colonies on BA
-yellow convex, entire, smooth colonies on chocolate
-poorly staining coccobacilli
-KIA- acid/acid
-only xylose & mannitol are neg
-nitrite; strong reduction
Haemophilus spp
-require hemoglobin for growth
–factor X (hemin)- heat stable
–factor V (NAD)- heat-labile, coenzyme, NAD found in blood
-pleomorphic gram neg bacilli
haemophilus species
-true haemophilus require both X & V
-parainfluenzae only uses factor V
-aphrophilus only used factor X
swollen joints revealing cloudy fluid & gram neg bacilli:
kingella kingae
-septic arthritis
lab ID of aggregatibacter actinomycecomitans
-slow growing, tiny, non hemolytic colonies on BA
-pale-staining gram neg cocco-bacilli
-KIA: acid/acid
-lactose & sucrose neg
-ornithine decarboxylase neg
-nitrate reduced
-indole neg
c. hominis
-endocarditis in patients with underlying valvular heart disease or with prosthetic valves
-aortic valve
-septic arthritis
-gram stain in rosettes
lab ID of c. hominis
-small, clear, smooth, non hemolytic colonies on BA
-gram variable slender bacilli with distinct poles in rosettes
-KIA: acid/acid
-xylose & lactose neg
-nitrates reduced to gas
-indole pos
eikenella corrodens
-soft tissue infections in teeth & trauma
-clenched fist & bite injuries
-exists in dental plague of healthy people
eikenella corrodens characteristics
-gram neg bacillus
-non motile
-non spore forming
-cytochrome pos
-reduced nitrate
-facultative anaerobe
-stimulated growth by 3-10% CO2
lab ID of kingella kingae
-small, entire, transparent colonies on BA with soft beta hemolysis
-gram neg, short, plump coccobacilli
-KIA: alk/alk (non-fermenter)
-oxidase utilization of dextrose & maltose (the rest are neg)
bacillus anthracis
-large, spore-forming aerobic, gram pos in pairs or long chains
-nonmotile, nonhemolytic
-grows rapidly in host & culture
-vegetative & spore
anthrax
-disease of herbivores
-inhalation, cutaneous, GI
-bioterrorism
b. anthracis spores
sporulation requirements: poor nutrient condition, presence of oxygen
spores: very resistant
-lethal dose: 2500-55000 spores
b. anthracis virulence
2 active chains (EF, LF) & one binding chain (PA)
-capsule: poly-D-glutamic acid. antiphagocytic
-EF: increases intracellular cAMP. hypersecretion (edema)
-LF: Zn-dependent peptidase. induced apoptosis & cell necrosis
PA: binding component, combines & delivers EF or LF
b. cereus misc.
-normal in soil
-food-borne intoxications
-in sushi rice if not stored properly (vinegar)
b. cereus characteristics
-large, spore forming, aerobic, gram pos bacillus
-non hemolytic
-motile
-box-car shaped
-stain with malachite green
-food borne transmission (undercooked rice)
-resistant to penicillin
importance of spores
-resistant to heat, drying, pressure & disinfectants
-antibiotic resistant
-survive in hospital environment
-spores are not reproductive (survival)
diagnostic spore form for c. tetani & c. botulinum
tetani: terminal spore
botulinum: sub-terminal spore
lab ID b. cereus
-large, flat, grey-yellow colonies on BA, matte to granular consistency, fimbriated edges & beta hemolysis
-short, gram pos bacilli, singularly or short chains, central or subterminal spores
-catalase pos
-lecithinase produced on egg yolk agar
-casein, starch, gelatin hydrolyzed
lab ID of bacillus anthracis
-flat, spreading, non hemolytic, grey-yellow colonies on BA with ground-glass surface & irregular margins
-tenacious consistency that stands up like whipped egg
-long, gram pos bacilli in chains.
-terminal & subterminal spores
-catalase pos
-reference lab for ID
clostridium perfingens
-gram pos, non motile, obligate anaerobes, spore forming, capsulated, rounded end bacilli
-spores are oval, central or subterminal, not bulging
-grows best on glucose or glucose blood agar
-self limiting gastroenteritis or clostridial myonecrosis
-produce alpha, beta, epsilon toxins
-all types produce alpha-toxin (phospholipase)
gangrene causative agent
c. perfringens pathogenesis
cellulitis: subcutaneous tissue infection, discolored skin, gas formation, edema, no necrosis
suppurtative myostits: fascilitis, pus in muscles, no necrosis
clostridial myonecreosis: gas gangrene, life-threatening, muscle necrosis, fast spreading, tachycardia & systemic fever, intravascular hemolysis, shock, organ failure
-super fatal
camp reactions
-regular arrow head is strep streaked with staph aureus
-gram pos bacilli have a synergistic zone that is small & rectangular (Listeria identification)
c. perfringens ID
-double zone of hemolysis
-robertson’s media(cooked meat medium): blackening of meat with strict anaerobes
-clots litmus milk (stormy fermentation: acid gas curd)
c. difficile
-gram pos, spore forming bacillus
-grows on selective media in 2 days & smells like horse poop
-strict anaerobe, motile, difficult to culture
-normal gut flora
-relatively drug resistant
cdif & antibiotics
antibiotics (vanco, clindamycin, cephalosporins, penicillins, beta-lactams) reduce all other bacteria in the intestinal track and allow for overgrowth of c. difficile, leading to CDI
c. dificille virulence
-toxigenic strains produce 2 large protein exotoxins that are associated with virulence (toxins A & B)
-toxin A (enterotoxin) damages tight junctions which increase the permeability of gut epithelial layer. chemoattractant for PMNs
-toxin B (cytotoxin) destroys cytoskeleton, kills enterocytes
pseudomembranous colitis (antibiotic resistant colitis)
-fever, abdominal pain, bloating, cramping
-fulminant watery diarrhea with WBC
-inflammatory plaque on gut wall
-progresses to toxic megacolon (fatal)
anaerobic bacteria
-toxic forms of oxygen get neutralized by superoxidase dismutase, catalase, peroxidase
-anaerobic bacteria do not produce these and cannot survive in the toxic oxygen
c. botulinum
-strict anaerobe, gram pos bacillus,
-found in soil, animal feces
c. botulinum virulence
-botulinum toxin
-toxins A, B, E, & F cause human disease
-A & B associated with foods
-E associated with fish products
c. botulinum pathogenicity
-absorbed through gut, carried via blood, binds presynapses of motor neurons in PNS & CNS
-block release of acetlylcholine
-protease that cleaves proteins
infant botulism
-first month of life
-ingestion of honey causes botulism in infants
lab diagnosis of botulinum
-culture from feces
-definitive diagnosis = detection of toxin
-ELISA & PCR
c. tetani
-anaerobic, gram pos, slender bacilli
-spherical, terminal spores giving drum stick appearance
-no capsules
-motile with flagella
c. tetani virulence
-2 exotoxins: tetanolysin, tetanospasmin
-tetanolysin: damages tissues surrounding infection and optimizes conditions for bacterial multiplication
-tetanospasmin (tetanus toxin): plasmid-coded neurotoxin responsible for disease
-released upon cell lysis after bacterial overgrowth (anaerobic conditions).
-antigenic and neutralized by its antitoxin. toxoid form used for vaccine
c. tetani pathogenicity
-unlike c. perfringens, c. tetani is not invasive
-remains localized
-germination of spores aided by: necrotic tissue, calcium salts, pyogenic infections
-tetanopasmin blocks GABA causing muscle spasms (spastic paralysis)
c. tetani lab diagnosis
-anaerobic culture of tissues, not required for ID
-RCM broth: tetani turns meat particles black
-blood agar with polymyxin B
clostridia spores & ID of organism
central spore: c. bifermentans
sub-terminal: c. perfringens
oval & terminal: c. tetrium
spherical & terminal (drum stick): tetani
