Miscellaneous Pathogenic Organisms

Gardnerella vaginalis infection

• Vaginosis

• Polymicrobic disease associated with anaerobic bacteria, malodorous discharge

• Infections indicated by the presence of Clue cells which are squamous epithelial cells covered with bacilli

Gardnerella vaginalis biochemicals

• BAP: non-hemolytic

• Inhibition: inhibits alpha strep

• Beta-hemolytic growth on V agar (human blood and Tween 80)

• Odor: fishy smell when KOH is added to vaginal secretions

How can you presumptively identify Gardnerella vaginalis

• Gram stain: small GPB (variable)

• Catalase negative

• Beta-hemolytic on V agar

Streptobacillus moniliformis infection and spread

• Normal flora: rodents

• Clinical infections:

  • Rate bite fever

  • Haverhill fever - ingestion of contaminated milk or water (contaminated with rat droppings)

Streptobacillus moniliformis biochemicals

• Gram stain: pleomorphic GNB, forming long, looped curved filaments, can have distinctive beaded-necklace shaped forms

• Isolated from blood, synovial fluid, ascites fluid

• SPS: sensitive, recovery from blood culture bottle impeded

• Thio: growth at the bottom of the tube in the form of "fluff balls” or bread crumbs

• Rogosa medium: specific, rarely used

Aggregatibacter general characteristics

• Normal flora: mouth

• Isolated from: blood, lung tissue, sinuses, oral abscesses

• Clinical infection: endocarditis

• Gram stain: small GNB or GNCB

• Atmosphere: requires increased CO2, 24-48 hours

Aggregatibacter aphrophilus

• Colony morphology: yellow, opaque zone in the center

Aggregatibacter actinomycetemcomitans

• Colony morphology: 4-6 pointed star, 48 hour incubation

Cardiobacterium

• Normal flora: respiratory, GI tracts

• Associated with: endocarditis, patients with pre-existing conditions, dental procedures

• Gram stain: GNB, one round end, one tapered end, form rosettes

• BAP: alpha-hemolytic, pits agar

• MAC: no growth

• Oxidase positive

• Indole positive

Capnocytophaga

• Normal flora: oral cavity

• Associated with:

  • Juvenile periodontitis

  • Endocarditis

• Microaerophilic/Capnophilic - CO2 loving

• Usually isolated on anaerobic culture

• Gram stain: fusiform GNB

• Gliding motility: not swarming

Chromobacterium violaceum

• Natural environment: soil and water in tropical and subtropical climates

• Gram stain: GNB, can be curved like Vibrio

• Colony morphology: violet pigment

• Broth cultures: uniform turbidity with violet pellicle

• Odor: almonds

• Glucose fermenter: oxidase +/-

Calymmatobacterium (now Klebsiella) granulomatis

• Donovanosis, granuloma inguinale, granuloma venerem

• Associated with: chronic progressive granulomatous disease involving skin, tissue of genitals, inguinal, and anal areas

• Specimen: scrapings of lesion, puncture biopsies

• Gram Stain: pleomorphic GNB, bipolar staining

• Identification: intracellular GNB in histiocytes “Donovan bodies”

Spirillum minus (Spirillum minor)

• Clinical infection: rat bite fever

• Closely related to Campylobacter

• Gram stain: GNB with 2-3 spirals

• Does not grow on artificial media

• Identification

  • Microscopic

  • Animal inoculation

Bartonella bacilliformis

• Endemic: mountainous regions of Columbia, Peru, Ecuador

• Vector: transmitted by mosquitoes

• Etiologic agent for Carrion’s disease

  • Oroya fever - stage 1, hemolytic anemia (high fatality in conjunction with Salmonella)

  • Verruga peruana - stage 2, cranberry-like skin eruptions, rarely fatal

• Gram stain: GNCB, parasitize RBCs (they burst!)

Bartonella henselae

• Cat scratch fever

• Transmitted by insects, lice, cat fleas

• Isolate from skin nodules/lesions or blood

• Isolation rate low, serology and molecular methods used