Eikenella Species

Eikenella Species

  • Chapter Reference: Chapter 28

  • Eikenella corrodens

    • Classification:

    • Slow growing, gram-negative, non-motile facultative rod

    • Growth Characteristics:

    • Does not grow on MacConkey's agar

    • Normal Microbiota:

    • Found as a part of the normal human microbiota from the Haysec group

    • Isolation:

    • Isolated from dental plaque

    • Infections Associated:

    • Periodontitis

    • Bite wound infections

    • Bacteremia

    • Endocarditis

    • Aspiration pneumonia (as part of mixed infections)

    • Transmission:

    • Person to person via bites or fist wounds

    • Particularly from facial punches

    • Special Risks:

    • Patients with diabetes at higher risk due to daily microtrauma (e.g., glucose monitoring, insulin injections)

    • Other Potential Infections:

    • Meningitis

    • Pneumonia

    • Osteomyelitis

    • Arthritis

    • Cellulitis

    • Postoperative tissue infections (from bacteremia associated with wounds)

    • Environmental Preferences:

    • Grows in a capnophilic environment (high CO2 concentration)

    • Very slow growth on blood agar and chocolate media

    • Limited growth in blood culture media, thioglycolate broth, or brain heart infusion broths

    • Nutritional Requirements:

    • Requires hemin (X factor) and CO2

    • Characteristics:

    • Characteristic bleach-like odor (45% of isolates)

    • Yellow colonies with pittings or corroding of agar

    • Oxidase positive and catalase negative

Pasteurella Species

  • Chapter Reference: Chapter 29

  • Pasteurella multocida

    • Classification:

    • Small gram-negative rod

    • Growth Characteristics:

    • Does not grow on MacConkey's agar

    • Infection Mechanism:

    • Opportunistic; requires disruption of host barriers (typically from cat or dog bites)

    • Common Clinical Presentation:

    • Most often associated with cat bites

    • Drug Susceptibility:

    • Most species susceptible to penicillin

    • Penicillin is the drug of choice for Pasteurella multocida infections

    • Biochemical Characteristics:

    • Oxidase positive

    • Catalase positive

    • Grows well on blood agar and chocolate agar

    • Respiration:

    • Facultative anaerobe

    • Makes ATP by aerobic respiration if oxygen present but can use fermentation if absent

    • Unique Staining:

    • Bipolar staining gives a "safety pin appearance"

Actinobacillus Species

  • Chapter Reference: Chapter 30

  • Actinobacillus

    • Classification:

    • Short to very short gram-negative bacilli

    • Growth Characteristics:

    • Very slow growers; takes almost two days at 35-37°C

    • Does not grow on MacConkey's agar

    • Capnophilic (requires increased CO2)

    • Natural Habitat:

    • Normal microbiota of the nasopharynx or oral cavity

    • Infections Associated:

    • Periodontitis

    • Endocarditis

    • Granulomatous disease in animals

    • Soft tissue infections

    • Infection Mechanisms:

    • Occurs with the introduction into sterile sites (via bites, droplet transmission, or oral manipulation)

    • Culturing:

    • Slow growth, plates should be held for 2 to 7 days

    • Grows on 5% sheep blood agar and chocolate agar

    • Selective media (e.g., Columbia agar with 5% blood) may be used for enhanced recovery and identification

    • Colony Characteristics:

    • Small, sticky, adherent colonies (rough or smooth), non-hemolytic

    • All species are positive for urease

Bartonella Species

  • Chapter Reference: Chapter 32

  • Bartonella Species

    • Classification:

    • Short gram-negative rods

    • Does not grow on MacConkey's agar

    • Grows well on chocolate agar

    • Growth Duration:

    • May take up to 45 days to grow on blood agar

    • Unique Characteristics:

    • Facultatively intracellular; multiplies in red blood cells within reservoir host

    • Transmission Pathway:

    • Arthropod-borne transmission

    • Pathogenesis:

    • Interacts with host cells to proliferate microvascular endothelial cells

    • Ability to cause angiogenesis (formation of new blood vessels)

    • Activates monocyte and macrophage cells to produce angiogenic factors

    • Inhibits endothelial cell apoptosis

    • Bartonella henselae

    • Emerging pathogen

    • Colony appearance: Irregular, dry, white cauliflower-like colonies that pit the agar

    • Associated Infections:

      • Bacteremia

      • Endocarditis

      • Cat scratch disease (transmitted by cats)

    • Symptoms of Cat Scratch Disease:

      • Fever

      • Headache

      • Rash

      • Bone pain (notably in shins, neck, back)

    • Rare Condition:

      • Peliosis hepatitis (multiple blood-filled cavities in the liver)

    • Diagnostic Criteria for Cat Scratch Disease:

    • Must meet at least 3 of the following

      1. History of animal contact

      2. Negative laboratory studies for causes of lymphadenopathy

      3. Characteristic histopathological appearance of a lesion

      4. Positive skin test with Bartonella henselae antigen

    • Detection Methods:

    • Tissue biopsies using Warthin-Starry silver stain

    • Immunofluorescence and immunohistochemical techniques

    • Recommended culturing methodologies:

      • Inoculation onto fresh chocolate agar

      • Co-cultivation with endothelial cell cultures