Anaerobic Infection Flashcards

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1
Q

Require complete absence of oxygen is?

A

Obligate/ strict anaerobe

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2
Q

Classification of anaerobes?

A
  1. Spore forming anaerobes
  2. Non-spore-forming anaerobes
  3. Spirochaetes
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3
Q

Predisposing factors for Anaerobic Infections?

A
  1. Trauma
  2. Impaired blood supply
  3. Presence of other organisms
  4. Foreign bodies
  5. Disruption of barriers
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4
Q

Features of anaerobic infections?

A
  1. Production of a large amount of foul-smelling pus.
  2. Proximity of lesions to mucosal surface or portal of entry. 3. Failure to isolate organisms from pus by the usual aerobic methods (sterile pus).
  3. Infection associated with necrotic tissue, deep seated abscesses or closed space , e.g. brain
    abscess.
  4. Gas formation in the surrounding tissues detected as crepitations.
  5. Failure to respond to conventional antimicrobial therapy. 7. Presence of special character, e.g. Sulphur granules seen by the naked eye in the pus in case of actinomycosis
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5
Q

anaerobic infections Presence of special character?

A

Sulphur granules seen by the naked eye in the pus in case of actinomycosis

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6
Q

Common types of anaerobic infections?

A

Respiratory tract infections

Central nervous system infections

Intra-abdominal and pelvic infection

Wounds and soft tissue infections

Bacteremia and endocarditis

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7
Q

Laboratory diagnosis of Anaerobic Infections?

A
  1. Specimen
    II. Macroscopic examination
    III. Microscopic examination
    IV. Culture
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8
Q

Laboratory diagnosis of Anaerobic Infections

I. Specimen?

A

 Adequate clinical specimens are collected and transported, as soon as
possible, to the laboratory, preferably before antibiotic therapy.
 Best samples are taken by disposable closed syringe or on swab with
reduced transport media.
 The samples should be taken, as deep as possible , away from atmospheric
oxygen and as much sample as possible.

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9
Q

Treatment of anaerobic infections

?

A

Surgical treatment:
Antimicrobial therapy:
3. Treatment of the aerobic organisms accompanying anaerobes, in a
mixed infection, is also necessary.

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10
Q

drainage of pus from abscesses, debridement, and

removal of necrotic tissues may be sufficient. ?

A

Treatment of anaerobic infections

1. Surgical treatment

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11
Q

Spore-forming Anaerobes ?

A

Clostridia

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12
Q

•Large, Gram-positive, spore-forming bacilli.
•The position of the spore within the vegetative cells is useful
in identifying the species

A

Clostridium
 Microbiological features:
 Morphology:

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13
Q

Clostridium Microbiological features?

A

-Morphology:

•Large, Gram-positive, spore-forming bacilli.
•The position of the spore within the vegetative cells is useful
in identifying the species

  • Culture characteristics:

• Anaerobic

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14
Q

Clostridium Natural habitat ?

A

 Soil  Intestinal tract of animals & humans

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15
Q

Clostridium Important species?

A

 Clostridium perfringens: Gas gangrene & Food poisoning
 Clostridium tetani: Tetanus
 Clostridium botulinum: Botulism

 Clostridium difficile: (superinfection).

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16
Q

Gram positive large rectangular bacilli
 Oval sub-terminal non bulging spores
 Spores are rarely seen

A

Clostridium perfringens Morphology

17
Q

Clostridium perfringens

Culture?

A

Anaerobic organism.

Colonies on blood agar are surrounded by complete haemolysis

18
Q

Biochemical reactions Clostridium perfringens

?

A

Ferments sugars with production of acid & gas.

19
Q

Clostridium perfringens

 Virulence factors?

A

Alpha-toxin: lecithinase

Theta-toxin: cytolysin

Others

20
Q

Clostridium perfringens Virulence factors:
 Alpha-toxin: lecithinase?  Theta-toxin: cytolysin
? Others?

A

Alpha-toxin: lecithinase
= It lyses cell membrane lecithin

Theta-toxin: cytolysin
= direct vascular injury

Others
= Haemolysins, collagenases, proteases, lipases

21
Q

Pathogenesis of Clostridium perfringens

?

A

All clostridial wound infections occur in an anaerobic tissue environment caused by
an impaired blood supply secondary to trauma, surgery, foreign bodies,
malignancy
 Usually polymicrobic because the source of wound contamination (faeces, soil) is
polymicrobic.

22
Q

Clostridium perfringens
 Clinical findings
?

A

A- Gas Gangrene (Clostridial myonecrosis)

B- Anaerobic Cellulitis

23
Q

Symptoms of Clostridium perfringens

?

A

As the clostridia multiply → exotoxins are liberated into the surrounding
tissue → more local tissue necrosis & systemic toxemia .  Infected muscle is discolored (purple mottling) & edematous & produces a
foul-smelling exudate & gas bubbles which cause crepitations.  Severe shock with massive hemolysis & renal failure is usually the ultimate
cause of death.

24
Q

Clostridium perfringens Diagnosis ?

A

Specimen: taken from the depth of the wound & examined rapidly.

25
Q

Clostridium perfringens Treatment & prevention:

?>

A

Correction of the anaerobic conditions:
• Drainage & Surgical removal of dead tissues
 Penicillin is the drug of choice
 Hyperbaric oxygen therapy may limit the spread of infection.

26
Q

Gram positive rod  Bulging terminal spore (drumstick appearance )  Most strains are motile

A

Clostridium tetani

Morphology

27
Q

Strict anaerobe
 Grows well on ordinary & cooked meat media.
 On blood agar, → swarm with surrounding zones of β-
hemolysis

A

Culture of Clostridium tetani

28
Q

Clostridium tetani

 Virulence factors:

A

Tetanospasmin toxin”

29
Q

Tetanus Pathogenesis?

A

Most cases result from lacerations or small puncture
wounds, contaminated with Cl. tetani spores.
 Ingestion of tetanus toxin does not produce the disease.
 The spores germinate , in the traumatized tissue, (the
blood supply is cut off & ischemia results, producing an anoxic
anaerobic environment, with low redox potential).
 A puncture wound can also cause spores to be injected
deeply into the tissue, offering anaerobic medium.
 The vegetative cells of Cl. tetani grow locally in the
necrotic tissue → release of tetanospasmin toxin.

30
Q

Tetanus Neonatal tetanus ?

A

mother lacks
immunity & the umbilical stump becomes
contaminated with Cl. tetani spores

31
Q

Tetanus Prevention?

A

I. Active immunization:
 Toxoid is given to infants in the first year of life: the triple
vaccine (DPT) is given at the age of 2, 4 & 6 months by IM injection.

II. Passive immunization Human tetanus immunoglobulin (HTIG)

32
Q

Non-spore-forming anaerobes

?

A

Bacteroides

33
Q

Gram-ve bacilli, highly pleomorphic  Capsulated (virulence factor)→ antiphagocytic.

A

Bacteroides

34
Q

The commonest pathogen among Bacteroides species

?

A

B. fragilis

35
Q

released from the colon into blood → multiplies rapidly →
?

Bacteroides

A

bacteremia

36
Q

If introduced into the abdominal cavity →

Bacteroides

A

abdominal abscess

37
Q

Drug resistance is common (beta lactamase production)  Preoperative antibiotics are given to prevent surgical wound
contamination with ?.

A

Bacteroides

38
Q

Gram+ve bacilli, having the typical morphology of diphtheroides.  Their metabolic products include propionic acid from which the
genus name is derived. ?

A

Propionibacterium Morphology

39
Q

Normally present in human skin, hair, oropharynx & GIT . It is the major contributor to the complex pathogenesis of acne vulgaris.
?

A

P. acne