Anaerobes Obligate Anaerobes - PowerPoint Presentation

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Anaerobes

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Obligate Anaerobes

only grow in the absence of oxygen (O2)

Aerotolerant / Microaerophilic anaerobes grow in reduced concentration of oxygen (~5% O2), but grow best under strict anaerobic conditions

Environmental Conditions

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Peptostreptococcus

Vieonella

??? Get correct spelling Anaerobic cocci

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Peptostreptococcus

(

Peptoniphilus) spp. Intestinal gram positive cocci

Key reactions

Nitrate (+)

SPS –sensitive

Indole (-)

P.

assacharolyticus

Form tetrads or pairs

Key reactions

:

SPS resistant, Indole (+), Nitrate (-)

P.

anaerobius

Elongated

Produce sweet odor due to the presence of

isocaproic

acid

Causes:

Head, neck , genital and gut infections

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Viellonella

species

Key reactions

Nitrate (+)

Non-fluorescent, may pigment red

Causes :

Endocarditis

and

bacteremia

Indigenous to

oral cavity, upper respiratory, G.I

and

genitourinary tract

Kanamycin (S )

Vancomycin (R )

Colistin

(S)

Small

Gram negative

cocci

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Clostridium species

Others ????? Positive Bacilli

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Clostridium

spp.

Gram positive rods

Causes :

Food poisoning

Gas gangrene(

myonecrosis

)

Neoplasm s

Lock jaw

Pseudomembraneous

colitis

Spore formers

Found commonly in stool specimen

Produce Virulence factors

that are responsible for infections

Four common species

Clostridium

perfringens

Clostridium difficile

Clostridium

tetani

Clostridium botulism Other Clostridium

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Appearance: box-shaped gram positive rod

Two zone beta hemolytic on SBA

Produces alpha and Theta toxinKey reactions:Lecthinase (+), nitrate (+) Reverse camp with group B Strep.Stormy fermentation of litmus milkKanamycin (S ), Vancomycin (S), Colistin (R)Causes:Gas gangrene, Food poisoning (Enterotoxin A), Soft tissue infections in diabetics and Necrotizing bowel disease Clostridium perfringens

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Subterminal spore Chartreuse fluorescence

Key reactions

Ferment fructoseLecthinase (-), Lipase (-)Causes:Pseudomonas colitis and Antibiotic associated diarrhea (AAD) due to enterotoxin A and BClostridium difficile

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Toxin: tetanospasmin

(

neurotoxic exotoxin)Motile, swarms Appearance: Gram positive rods. Produce terminal spores that appear as drumsticks Biochemical reactions:Lipase (-), Indole (+)Causes:Lockjaw, respiratory failure and tetanus neonatorum Clostridium tetani

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Toxin: botulin

Key reaction:

Lipase (+)Causes:Botulism: Inhibits acetlycholine release from motor neuronsClostridium botulism

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Clostridium

novyi

Beta hemolytic Key reactions:Lecithinase (+), lipase (+), indole (-), urease (-)Causes: Gas gangrene (myonecrosis) and toxic shockRapid swarmerCharacteristic:

medusa head, subterminal sporesKey reactions:Lipase (-), Indole (-)

Causes

:

Neoplasm of the colon, breast

leukemia, lymphoma,

enterocolitis

.

myonecrosis

Other Clostridium spp.

Clostridium

septicum

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Lactobacillus

Gram positive

Non-spore forming bacilliNormal flora in the oral cavity, G.I. and female genital tract

Protect

female genital tract

Produce lactic acid

to

lower vaginal pH

Infections caused

:

Bacterial

vaginosis

Pelvic inflammatory disease

Key reactions

Catalase (-)

Cephalosporin (R)

Vancomycin (R )

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Proprionibacterium

acnes

Gram positive Non-spore forming bacilli (appear as diptheroids)Normal flora of the skin

Can cause

:

Subacute

bacterial

endocarditis

Bacteremia

Reactions

Catalase (+)

Indole (+)

Nitrate (+ )

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Bacteroides

fragilis

Bacteroides ureolyticusFusobacterium nucleatumFusobacterium

necrophorumOther

Fusobacterium

Porphyromona

spp.

Prevotella

spp.

Negative Bacilli

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Bacteroides

fragilis

Key reactions

Catalase (+)

Indole (-)

Nitrate (-)

Bile tolerant, Non-motile

Causes :

Inflammation of the intestinal wall

Septic abortion

Thrombosis

G.I. infections

Gram negative rod

Penicillin (R )

Kanamycin (R )

Vancomycin (R )

Colistin

(R )

Clindamycin

(S)

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Bacteroides

ureolyticus

Key reaction

Urease (+)

Bile sensitive, Non-motile

Causes :

Respiratory infections

Intestinal tract infections

Gram negative rod

Kanamycin (S )

Vancomycin (R )

Colistin

(S)

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Fusobacterium

nucleatum

Key reactions

Lipase (-)

Indole (+)

Causes :

Metastatic brain abscess

Fusiform

Gram negative bacilli

Kanamycin (S )

Vancomycin (R )

Colistin

(S)

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Fusobacterium

necrophorum

Key reaction

Lipase (+)

Causes :

Pertonsillar

abscess in children and young adult

Pleomorphic

filamentous gram

negative rod

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Prevotella

melaninogenica Gram negative coccobacilli

Produces foul odor

Slow producer of

protoporphin

Causes :

Lung and dental infections

Normal flora in the oral, G.I and vaginal area

Kanamycin (R )

Vancomycin (R )

Colistin

(S)

Penicillin (R)

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Acceptable specimens :

Aspirates from sterile site deep wounds , bodily fluids (except urine, sputum and saliva), and suprapubic bladder aspirates

Primary media: Brucella (CDC or Schaedler) blood agar- contains hemin, vitamin K and yeast extract. Detect hemolysis in anaerobesSpecial media:Bacteroides bile esculin (BBE) agar- contains gentamycin (inhibits facultative aerobic gram negative rods ) and 20% bile. Laked Kanamycin Vancomycin (LKV) blood agar – identify pigmented gram negatives . (Kanamycin inhibits facultative gram negative rods and

Vancomycin inhibits gram positive rods)Phenyl-ethyl Alcohol (PEA) plate : inhibits swarming

Cycloserine cefoxitin fructose (CCFA) agar

:

selective for Clostridium difficile

Egg yolk agar-

selective for Lecithinase and lipase production

Thioglycollate broth

: provides reduced O2 environment

Specimen transport and processing

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Identification tests :

Catalase test

: distinguish aerotolerant anaerobes from anaerobic organisms Indole: identify organisms that produce tryptophanase (Note: media needs to contain tryptophan) Nitrate test:Urea test: identify organisms that produce urease. Observe pH change. Urea is converted to ammoniaIncubate media in anaerobic gas chambersContains H2, N2, carbon dioxide , palladium catalyst and desiccants (absorb water) Keep media for 7 days Specimen transport and processing

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Metronidazole – best treatment

. Confirms the presence of an anaerobe

Clostridium infection: Use antitoxins , antibiotics (i.e. Chloramphenicol, pipercillin, imipramine or ampicillin/sulbactam) and supportive therapy Clinical Treatment