BSCI 424 — PATHOGENIC MICROBIOLOGY — Fall 2000

Summary of Clinically Important
Non-Spore Forming Anaerobes

  Heterogeneous group of opportunistic pathogens that are normal flora of skin and mucosal membranes

  Slow growth on artificial medium and fastidious nutritional requirements

  Typical sites of anaerobic infection:

 Blood (septicemia)

  Central nervous system (brain abscesses)

  Head, neck, dental and orofacial

  Thoracic

  Intraabdominal

  Obstetric-gynecologic

  Soft tissues

  Abscesses of other sites

  General features of anaerobic infections:

 Caused by endogenous opportunistic pathogens introduced into normally sterile body sites and therefore not transmissible from person-to-person

  Polymicrobic (polymicrobial) (mixed anaerobes or anaerobes and aerobes acting synergistically) (see WebLinked image)

  Sites of infection have reduced partial pressure of oxygen (PO₂) usually from compromised host defense or trauma

  Abscess formation and tissue necrosis

  Require broad-spectrum and long-term antimicrobial therapy and often either surgical debridement or surgical removal of necrotic tissue(s) and abscess(es)

  Clinical features of anaerobic infections:

 Site and history suggestive of anaerobic infection (see above); proximity to mucosal surface

  Foul-smelling discharge (exudate)

  Necrotic tissue

  Gas in tissue or discharge (exudate) 

  Black discoloration of exudates

  Clinical features of gas gangrene or myonecrosis

Anaerobic Gram-Positive Cocci:

  Vagina predominantly colonized by anaerobic Gram-positive cocci as opposed to other body sites where anaerobic Gram-negative bacilli predominate

  Peptostreptococcus (see WebLinked image)

  Normally flora of oral cavity, gastrointestinal and genitourinary tracts and skin and spread into normally sterile sites

  Brain abscesses; sinusitis; endocarditis; osteomyelitis; pleuropulmonary, intraabdominal and pelvic infections; sort tissue infections

  Infections are commonly polymicrobial with both aerobic and anaerobic organisms

  Usually susceptible to penicillin

Anaerobic Gram-Negative Cocci:

  Veillonella (see WebLinked image)

  Rare opportunistic infections; low virulence potential

  Normal flora of oral cavity, dental plaque, upper respiratory tract and small intestine

  Associated with long-standing gingivitis in dental patients

Anaerobic Gram-Positive Bacilli:

  Actinomyces (see separate dedicated WebPage)

  Lactobacillus (see separate dedicated WebPage)

  Mobiluncus

  Gram-positive cell wall, but stain Gram-negative or variable

  Abundant in women with bacterial vaginosis (vaginitis) but of uncertain etiology

  Propionibacterium (see separate dedicated WebPage)

  Bifidobacterium (see WebLinked image)

  Rare opportunistic infections; low virulence potential

  Normal flora of large intestine

  Eubacterium (see WebLinked image)

  Rare opportunistic infections; low virulence potential

  Normal flora of large intestine and dental plaque

  Rothia

  Rare opportunistic infections; low virulence potential

  Normal flora of dental plaque

Anaerobic Gram-Negative Bacilli:

  Anaerobic Gram-negative bacilli are predominant normal flora in most anaerobic body sites

  Bacteroides (see separate dedicated WebPage)

  Prevotella (formerly classified as Bacteroides)

  Extremely small, bile-sensitive, sacchorolytic bacilli

  Normal flora of upper respiratory tract, mouth and vagina

  Associated with head and neck, upper respiratory tract, intraabdominal (may lead to septicemia) and gynecological (genital tract) (may lead to septicemia) infections

  Porphyromonas (formerly classified as Bacteroides)

  Pigmented (purple) asaccharolytic bacilli ("porphyro" is from the Greek for purple)

  Normal flora of mouth and genitourinary tract

  Associated with head and neck, pleuropulmonary and upper respiratory tract infections

  Fusobacterium (see WebLinked image; see WebLinked image)

  Elongated "fusiform" bacilli

  Normal flora or oral cavity, large intestine and genitourinary tract

  Associated with head and neck, pleuropulmonary and intraabdominal infections which may lead to bacteremia

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