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Infectious Agents > Anaerobes > Flashcards

Anaerobes Flashcards

1
Q

What are the 4 major obligate anaerobe pathogens?

A
  • GP spore forming rods (clostridium)
  • GP non-spore forming rods (actinomyces, propionbacterium, eubacterium)
  • GN rods (bacteroides, fusobacterium)
  • GP cocci (peptococcus, peptostreptococcus)
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2
Q

The body’s normal flora is predominantly _________

A

Anaerobic

  • colonize nearly all mucosal surfaces
  • colon: 90% of fecal matter, obligate anaerobes outnumber others by >1000:1
  • obligate anaerobes outnumber others in the mouth by 10:1
  • oropharynx and lower GIT*
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3
Q

Why are obligate anaerobes able to survive in the mouth?

A

Oral/viridans streptococci lower the red-ox potential

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4
Q

Most anaerobic infections are _______ in origin

A

Endogenous

- occur with a break in host defense and low oxygen tension or low red-ox potential is present

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5
Q

Polymicrobial

A

Anaerobic infections containing both obligate and facultative anaerobes due to tissue contamination with multiple species of host’s microflora

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6
Q

What are the 3 synergistic mechanisms used by anaerobes?

A
  • bacteriodes spp. require vitamin K from nonpathogenic streptococci
  • B. asaccharolyticus causes spreading lesions supplied with succinate from klebsiella
  • facultative anaerobes (E. coli) provide a better environment for anaerobes by removing O2 and adding reducing substances throughout the infection —> anaerobes then produce leukotoxins and depleting opsonins and complement
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7
Q

What anaerobe does not produce a putrid odor during infection?

A

Actinomyces

- microaerobic, capnophilic

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8
Q

Bite wounds

A

Commonly involve anaerobes

- pasteruella (not anaerobic), bacteroides, fusobacterium, paptostreptococcus

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9
Q

What type of sample would you take for an osteomyelitis infection?

A

Surgical, should include sequestra, bone from infection, or adjacent soft tissue >1 cubic cm in size
- superficial swabs will be contaminated with secondary opportunists!

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10
Q

What is essential for a preliminary diagnosis of anaerobes?

A

Stained smears

- preferably both a gram stain and cytologic stain (all bacteria will be blue with cytologic)

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11
Q

Specimens from acute bacterial infections usually contain many ________

A

Neutrophils

- exception: when patient is neutropenic from clostridial myonecrosis

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12
Q

What suggests contamination by normal flora?

A

Presence of multiple morphological types of bacteria and epithelial cells, few or no neutrophils

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13
Q

What suggests presence of anaerobes?

A

Multiple morphological types with neutrophils

  • only one or 2 morphologic types: aerobes or facultatives present
  • multiple types plus negative cultures suggests anaerobes
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14
Q

Bacteroides

A
  • GN rods
  • pleomorphic, may be beaded, coccoid, slender
  • stain poorly, difficult to see
  • sometimes bipolar staining
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15
Q

Clostridium

A
  • GP rods
  • large chains
  • spores swell sporangium
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16
Q

Fusobacterium

A
  • GN rods
  • thin, pale, tapered ends
  • cigar/needle shape
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17
Q

Actinomyces

A
  • GP rods
  • small, thin, branched filaments or tangled mats
  • beaded and poorly visible
  • may form sulfur granules
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18
Q

Peptococcus

A
  • GP cocci
  • small, singly, pairs, or clusters in pairs/chains
  • cannot be distinguished from aerobic cocci
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19
Q

What should not be cultured?

A

Specimens that might be contaminated with normal flora

- just assume anaerobes are present

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20
Q

Do anaerobes exist in urine?

A

No!

- urine is toxic/cidal to anaerobes

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21
Q

Acceptable collections

A
  • aspriates from enclosed lesions or body sites normally sterile (potential spaces)
  • TTA, lung aspirates
  • uterine aspirates
  • aspirates of abscesses, deep wound
  • tissue obtained from deep infections during debridement
  • sequestra, bone biopsies, nearby soft tissue
  • blood (not routine)
  • aspirates from occeous bullae or frontal sinuses
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22
Q

Unacceptable collections

A
  • swabs of pus from superficial or draining tracts
  • urine
  • mouth, pharynx, upper airway swabs (should already suspect presence of anaerobes)
  • swabs from vagina, cervix, urethra
  • feces
  • saliva or nasal exudates
  • ear swabs
  • cerebrospinal fluid, nasotracheal, bronchoscopic aspirates
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23
Q

Syringes

A

Should empty of air and cap (stick needle into rubber sterile stopper)

24
Q

Processing

A

Process immediately

  • facultative outgrow anaerobes and syringes absorb air
  • if there is a delay, specimens should be kept at room temp in commercial CO2 filled tubes (will survive 72 hrs)
25
Q

Specimens should not be collected into _____ for transport

A

Thioglycolate broth

26
Q

Culturing anaerobes

A

Methods are expensive and time-consuming, multiple isolates need to be processed leading to longer turnaround time
- cultured on special media and incubated in evacuation replacement anaerobic jars or GasPakTM system, anaerobic glovebox chambers

27
Q

Successful treatments

A
  • aggressive surgery
  • lavage body cavities
  • hyperbaric oxygen therapy
28
Q

When are antimicrobials used?

A

High doses for long periods, especially in chronic infections
- tends to recur if all devitalized tissue is not removed

29
Q

What antibiotics are most efficacious?

A
  • penicillins
  • chloramphenicol
  • clindamycin
  • metronidazole
30
Q

What are not effective?

A

Aminoglycosides (gentamycin, amakacin)

- given concurrently to cover GN enterics in mixed infections

31
Q

What is efficacious against broth GN enterics and anaerobes?

A

Some cephalosporins (cefoxitin)

32
Q

What are not useful for anaerobes?

A
  • tetracyclines
  • sulfonamides
  • trimethoprim-sulfonamides
33
Q

Clostridium

A

Aerotolerant anaerobe, easily isolated, produces double zone hemolysis

  • toxins A-E (geographically located, US mainly type A)
  • all toxins cause enteric disease in all domestic animals
34
Q

C. perfringens toxin A

A

Necrotic enteritis in fowl (from wheat diet), myonecrosis, food poisoning, enterotoxemia

35
Q

C. perfringens toxin B

A

Dysentery in lambs, chronic enteritis in older lambs, hemorrhagic enteritis and enterotoxemia

36
Q

C. perfringens toxin C

A

Enteritis necroticans, necrotic enteritis in fowl, hemorrhagic or necrotic enterotoxemia

37
Q

C. perfringens toxin D

A

Enterotoxemia, enterocolitis, enterotoxemia in adult cattle

38
Q

C. perfringens toxin E

A

Enterotoxemia, enteritis

39
Q

C. perfringens toxin A-E all cause

A

Canine and porcine enteritis, possible bovine and equine enteritis

40
Q

C. septicum

A

Abomastitis in sheep, possibly calves

- due to freeze damaged grass

41
Q

What are the 4 requirements for psuedomembranous colitis?

A
  • culture positive
  • toxin B and toxin B both present (ELISA)
  • antibiotic treatment administered before disease
  • present as pseudomembranous colitis
42
Q

C. difficile

A

-Pseudomembranous colitis in lab animals and humans, diarrhea in weaned rabbits

43
Q

C. spiroforme

A

Diarrhea in weaned rabbits

44
Q

C. colinum

A

Ulcerative enteritis (quail disease) in fowl

45
Q

Footrot in sheep

A

Contagious disease of germinal layers of interdigital skin and horn matrix

  • invaded by B. nodosus and F. necrophorum (synergistic infection)
  • multivalent bacterins and pili vaccines are effective for treatment and prevention with footbaths in epsom salts
46
Q

B. nodosus

A

Obligate parasite of hoof epidermis of sheep and cattle

  • persists on normal hoofs for long periods
  • pasture conditions and rainfall in temperate climates predispose
47
Q

Podoermatitis

A

Foot rot caused by F. necrophorum in cattle

  • secondary invader in many conditions of domestic animals
  • main pathogen in equine thrush
48
Q

Bacteriodes melanogenicus

A

Black pigment!

49
Q

Clostridium diseases are both ______ and _______

A

Histotoxic and enterotoxic

50
Q

What are the 2 neurotoxic forms of clostridia?

A
  • tetanus

- botulism

51
Q

How to treat clostridial diseases?

A

Commercial toxoids or killed whole-culture bacterins

  • 6 way clostridial vaccine
  • do not want to isolate/culture clostridia!
52
Q

Blackleg

A

Causes by clostridium chauvoei

  • activation of latent spores deposited in muscle after being transported in blood from liver or intestine
  • young cattle most susceptible due to bruising of large masses
53
Q

Clostridium septicum

A
  • malignant edema
  • braxy
  • participates in blackleg
  • chickens: gangrenous dermatitis
54
Q

Clostridium sordelli

A

Sudden death syndrome in cattle and sheep

- also participates in blackleg

55
Q

Clostridium novyi

A

Dies with any exposure to O2

  • gas gangrene
  • bighead
  • alpha toxin: necrosis of muscle, heart, liver, major VF
56
Q

Black disease

A

Occurs in liver, NOT leg

  • spores of type B germinate and produce tissue necrosis
  • germinate only in liver damaged
  • alpha toxin absorbed and has systemic effects
  • occurs in cattle and horses
57
Q

Clostridium haemolyticum

A

Similar to black disease except:

  • beta causes liver necrosis
  • absorbed toxin causes intravascular hemolysis = bacillary hemoglobinuria or redwater disease

Infectious Agents (44 decks)

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