Anaerobes Flashcards
facultative anaerobes can grown both aerobically and anaerobically
true or false
true
strict obligate anaerobes cannot tolerate more than what percentage of oxygen
0.5%
what is toxic to obligate anaerobes?
oxygen and it’s derivatives
aerotolerant anaerobes grow poorly in what environment? They grow well in what environment?
ambient air (21% O2)
anaerobic conditions
gram positive bacilli spore formers (anaerobic)
Clostridium botulinum
C. difficile
C. perfringes
C. septicum
C. tetani
gram positive bacilli non spore formers (anaerobic)
Actinomyces israelii
Bifidobacterium
Eubacterium lentum
Lactobacillus
Cutibacterium (Propionibacerium) acnes
Cutibacterium (Propionibacerium) propionicus
gram negative bacilli (anaerobes)
Bacteriodes fragilis grp
Campylobacter ureolyticus
Fusobacterium mortiferum
Fusobacterium necrophorum
Porphyromonas
Prevotella
gram positive cocci (anaerobes)
Peptostreptococcus anaerobius
Peptoniphilus asaccharolyticus
all spore forming anaerobic bacteria are in what genus?
Clostridium
exogenous diseases
caused by organisms/ toxins/ spores outside the body
enter through ingestion/ trauma
endogenous diseases
infections caused by hosts normal flora
clues of anaerobic infection
infection near mucosal surface
foul smelling discharge
necrotic tissue
black exudates that fluoresce red w/ UV light
most common anaerobic bacteria that cause infection
Bacteriodes fragilis
pigmented Prevotella
Porphyromonas
Fusobacterium nucleatum
Clostridium perfringens
anaerobic cocci
anaerobic specimen collection- good ones
sterile body fluids (CSF, blood, BM, synovial, ascitic)
tissue biopsies
trans tracheal aspirates
aspirated exudates from deep absecess
super pubic aspirates
anaerobic specimen collection- bad ones
swabs
stool
exudates from superficial wounds
respiratory samples
vaginal, cervical, urethra
the absence of leukocytes in a gram stain of anaerobe rules out an anaerobic infection
true or false?
false- some anaerobic bacteria produce necrotizing toxins that destroy leukocytes so they may not be present on the smear
anaerobic media- brucella blood agar
supports growth of almost all obligate and facultative anaerobes when incubated anaerobically
anaerobic media- BBE agar
bacteriodes bile esculin agar
selective and differential
used to isolate and ID Bacteriodes fragilis grp
BBE agar components
gentamicin (inhibits facultative)
bile (inhibits most anaerobic)
esculin (turns brown to black when hydrolyzed)
anaerobic media- KVLB
kanamycin-vancomycin- laked blood agar
supports growth of Bacteriodes and Prevotella
KVLB components
kanamycin inhibits GNR
vancomycin inhib. GP
laked blood encourages Prevotella to produce brown/black piment
anaerobic media- PEA agar
supports growth of nearly all obligate anaerobes (GP & GN) and GP facultative anaerobes when incubated anaerobically
anaerobic media- thioglycolate broth
non selective broth
contains reducing substances (thio, cysteine, sodium sulfite) and agar which limits O2 circulation from top of tube
anaerobic media- chopped meat/ cooked meat broth
enriched media that supports growth of most anaerobes
aerotolerance testing
determines if isolate can grow aerobically, anaerobically, or both\
CHOC- aerobic incubation
ANABA- anaerobic incubation
which anaerobic bacteria will grow in 20% bile?
Bacteroides fragilis
catalase test for anaerobic bacteria
uses 15% H2O2
Lecithinase test
tests ability of organism to degrade lecithin to insoluble diglycerides
inoculate EYA 24-72 hrs anaerobically
positive is white opaque zone in agar surround growth
id’s Clostridium
lipase
tests ability of organism to degrade triglycerides into glycerol and free fatty acids
inoculate EYA incubate 1-7 days
positive is pearly iridescent sheen on agar surface on growth (“oil on water”)
reverse CAMP test
organism in question is streaked down center of plate and GBS streaked perpendicular to test organism; incubated anaerobically 24-48 hrs.; positive is arrowhead shaped zone of enhanced hemolysis
alpha toxin in Clostridium perfringes works w/ beta hem. GBS
Clostridium vs. Bacillus
both: produce spores; GPB
Clostridium: catalase =; anaerobic
Bacillus: catalase +; aerobic
Clostridium perfringens infections
bacteremia
cellulitis
intra-abdominal abscesses
female genital tract infec
gas gangrene
food poisioning
Clostridium perfringens identification
GPB boxcar shaped
sometimes has spores
ANABA double zone of hem.
lecithinase positive
reverse CAMP positive
boxcar GPB anaerobic double zone hem on ANABA presumptive ID
Clostridioides difficile infections
antibiotic associated diarrhea and pseudomembranous colitis
30% neonates
3-5% healthy adults
Clostridium perfringens double zone hemolysis toxins
smaller zone (complete): theta-toxin (heat and labile toxin)
outer zone (partial): phospholipase C- an alpha toxin responsible for lecithinase + on EYA
C. difficile identification
GPB straight chains
spores- oval, subterminal, swelling of cells
CCFA media presumptive ID of C. difficile
smell like horse manure
fluoresce chartreuse
Clostridioides difficile toxins
toxin a
toxin b
tests done on toxins for ID
toxin B of C. difficile cytotoxicity test
toxin b present will cause cytopathic effect in human fibroblast tissue cultures
antitoxin added to test system prevents this effect (neutralizes action of toxin)
Clostridium botulinum infections
botulism (neurotoxins that cause descending flaccid paralysis)
Clostridium botulinum identification
hard to culture- may need to send off
specimens to send: stools, food items, serum, wound material
Clostridium septicum infection
muscle necrosis
bacteremia
leukemia/ lymphoma/ large bowel carcinoma
Clostridium septicum identification
ANABA: gray glossy translucent; beta hem w/ rhizod margin “medusa head”
GS: GP & GN with age
lecithin =
lipase =
indole=
esculin+
Clostridium tetani infections
tetanus (lockjaw)
produces neurotoxin- tetanospasmin- that causes muscle spasms
C. tetani identification
present in mixed cultures in wounds
difficult to grow
swarming colony
GS: terminal spores
Clostridium sordellii infections
gas gangrene
myonecrosis
(IV drug abuse black tar heroin)
7 exotoxins: lethal toxin and hemorrhagic toxin are most virulent
Clostridium sordellii identification
GS: subterminal/free spores
translucent- opaque w/ mottled internal
spread over agar
lecithinase +
lipase=
indole +
urea+
Actinomyces infections
A. israelii opportunistic pathogen affects head, neck, chest, abdomen
IUDs
lesions are suppurative and form draining sinus tracts
pus can have sulfur granules
Actinomyces identification
GS: straight/ curved GPR or filaments with true branching
modified acid fast- partial acid fast =
spiderlike/ wooly/ molar tooth apperance
red, pink, tan, yellow, gray
nitrate +
catalase =
Cutibacterium spp. infections
opportunistic- normal skin flora
skin
conjunctiva
bone
joints
cns
assoc. w/ surgical procedures or foreign bodies
Cutibacterium identification
C. acnes: GS- diphtheroid/ club; chinese letter
catalase +
indole +
GP anaerobic diphtheroid catalase + indole + presumptive ID
Eggerthella (Eubacterium) infections
normal mouth & intestinal tract flora
not a usual pathogen but Eggerthella lenta most commonly isolated from clinical specimens
Eggerthella identification
pleomorphic GPB in pairs/ clumps
small circular translucent
biochemically inert
catalase=
indole=
nitrate=
E. lenta nitrate+
Bifidobacterium infections
opportunistic pathogen
mouth and intestinal tract
Bifidobacterium identification
GPB variable from coccobacilli to branching rods
catalase =
indole=
nitrate=
esculin+
Anaerobic gram positive cocci generas
Anaerococcus
Atopobium
Coprococcus
Finegoldia
Gemella
Parvimonas
Peptococcus
Peptoniphilus
Peptostreptococcus
3 most common clinical anaerobic GPC species
Finegoldia magna
Peptostreptococcus anaerobius
Parvimonas micra
anaerobic GPC that is indole+ and SPS resistant can be presumptively ID’d as…
Peptoniphilus asaccharolyticus
Most common clinical GNB anaerobic bacteria genera
Bacteriodes
Prevotella
Porphyromonas
Fusobacterium
Bacteriodes fragilis identification
more resistant to antimicrobial agents
GS: GNR pleomorphic
resistant to kanamycin, vancomycin, colistin, and bile (20%)
growth stimulated by bile (BBE agar) turn medium brown or black due to esculin hydrolysis
Campylobacter ureolyticus identification
thin GNR with rounded ends
may pit the agar
kanamycin, colistin, bile susceptible
vancomycin resistant
catalase=
indole=
nitrate+
Prevotella identification
may be pigmented (enhanced on KVLB; fluoresce red)
coccobacilli/ pleomorphic rods
grow on KVLB but not BBE
resistant to kanamycin, vancomycin
bile susceptible
non pibmented fluoresce pink orange or chartreuse
must be id’d by biochemical tests
Porphyromonas identification
fastidious
require hemin and vit K for growth
prod brown/black pigmented colonies
fluoresce red
kanamycin, colistin resistant
bile susceptible
indole +
not grow on KVLB
Fusobacterium identification
GNR
rancid odor (prod. butyric acid)
susceptible to kanamycin, colistin
resistant to vancomycin
nitrate=
catalase=
Fusobacterium nucleatum detection
most commonly isolated species
thin fusiform GNR
bread crumb like colony, smooth ground glass/ speckled
fluoresces chartreuse
susceptible to bile
indole+
lipase=
Fusobacterium necrophorum identification
pleomorphic GNR- globular and swollen and bizarre shapes
fluoresce chartreuse
indole +
bile susceptible
lipase+
Fusobacterium mortiferum identification
pleomorphic globular swelling bizarre forms
Veillonella spp. identification
anaerobic GNC (only one)
reduce nitrate
fluroesce red
inhibited by bile, kanamycin, colistin
vancomycin resistant
AST for anaerobic bacteria- 2 tests approved by CLSI
agar dilution
broth microdilution panels
Finegoldia magna
Gpc
Vancomycin s
kanamycin v
Colistin r
