Unit 9: Unusual Organisms

HACEK (AACEK) GROUP

Acronym consisting of the first initial of each genus represented in this group: Aggregatibacter actinomycetemcomitans, Aggregatibacter aphrophilus, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae.

Capnophilic

The need for an increased CO2 environment.

Endocarditis

Infection of the heart, often caused by members of the HACEK group that have a predilection for attachment to heart valves, usually damaged or prosthetic.

AGGREGATIBACTER ACTINOMYCETEMCOMITANS

Found as normal oral flora in humans and is the most common cause of endocarditis in the HACEK group.

Characteristics of Aggregatibacter actinomycetemcomitans

GNCB, pleomorphic, non-motile, needs increased CO2 for optimal growth, small round colonies, and shows star formation in center of colonies after 48 hrs incubation.

AGGREGATIBACTER APHROPHILUS

Very low incidence of pathogenicity, implicated most often as causative agents of endocarditis, found in dental plaque and gingival scrapings.

CARDIOBACTERIUM HOMINIS

Only species in genus, NF of nose, mouth, and throat, may be present in the GI tract, and infects the aortic valve more frequently than other HACEKs.

Characteristics of Cardiobacterium hominis

GNB, pleomorphic, grows well on BAP and CHOC, colonies are small, slightly alpha-hemolytic, round, glistening, and opaque after 48 hours.

Aggregatibacter actinomycetemcomitans Isolation

Isolated from blood, lung tissue, abscesses of the mouth, and sinuses.

Characteristics of Aggregatibacter actinomycetemcomitans Growth

Prolonged incubation leads to granular growth (bread crumb or puff balls along tube of liquid media).

AGGREGATIBACTER APHROPHILUS Requirements

Requires X factor only and is nonhemolytic on horse blood.

CARDIOBACTERIUM HOMINIS Characteristics

Glucose (+), Sucrose (+), Lactose (-), Oxidase (+), Catalase (-), Indole (+), Urease (-), Nitrate (-).

CARDIOBACTERIUM HOMINIS Growth

After 48 hours, may produce 'pitting' on agar and shows no growth on MacConkey.

KINGELLA KINGAE

Important pathogen in children: Associated with blood, bone and joint infections.

KINGELLA KINGAE in adults

Endocarditis predominates.

KINGELLA KINGAE Morphology

Short, GNB; Small, soft zone of beta hemolysis; May 'pit' agar; Several days to grow (2-3 for visualization); Grows better in increased CO2 environment.

KINGELLA KINGAE Characteristics

Glucose (+), Maltose (+), Oxidase (+), Lactose (-), Catalase (-), Indole (-), Urea (-), Nitrate (-), Biochemically inert: lack of biochemical reactions.

KINGELLA KINGAE Treatment

Penicillin (Drug Of Choice), Ampicillin, Oxacillin, Ciprofloxacin, Cephalosporins, and Erythromycin.

CAPNOCYTOPHAGA Species

1. C. ochracea, 2. C. gingivalis, 3. C. sputigena, 4. C. haemolyticus, 5. C. granulose.

CAPNOCYTOPHAGA and Periodontitis

C. ochracea, C. gingivalis, and C. sputigena are implicated in periodontitis (gum disease).

CAPNOCYTOPHAGA Isolation

C. hemolyticus and C. granulose isolated from dental plaque.

CAPNOCYTOPHAGA Causes

Sepsis in patients with systemic infections such as leukemia and granulocytopenia (low granulocytes) who have oral ulcers; Juvenile periodontal disease; Endocarditis.

Capnocytophaga characteristics

GNB, fusiform-shaped bacilli with one rounded end and one tapered end, occasional filamentous form.

Capnocytophaga growth

Grows well on BAP and Choc, no growth on MAC.

Capnocytophaga colony appearance

After 48-72 hr incubation colonies are opaque, shiny, nonhemolytic, pale-beige or yellow color.

Capnocytophaga motility

Although flagella are usually absent, can produce a gliding motility (outgrowth of colony or haze on agar).

Bartonella henselae

Agent of 'Cat-Scratch Fever', first associated with cats in 1939.

Bartonella henselae symptoms

Begins as a papule or pustule at the primary inoculation site; regional tender lymphadenopathy develops in 1 to 2 weeks after appearance of lesion.

Bartonella quintana

Main reservoir is humans; causes Trench fever, Chronic bacteremia, endocarditis and bacillary angiomatosis.

Legionella

Ubiquitous in nature, many species found in soil, air, air-conditioning vents.

Legionella pneumophila

Causative agent of 'Legionnaires' Disease' and 'Pontiac Fever'.

Legionnaires' Disease

Febrile disease with pneumonia, 10-20% mortality rate.

Pontiac Fever

Febrile disease without pulmonary involvement, self-limiting, nonfatal infection.

Legionella characteristics

Short, pleomorphic GNB; fastidious organism which does not grow well on routine media.

Legionella growth requirements

Specific growth requirements: iron, cystine, pH 6.9-7.0.

GEMELLA

Normal flora of human oral cavity and upper respiratory tract; have been isolated from cases of endocarditis, wounds, and abscesses.

GEMELLA Characteristics

Morphology: GPC - chains, pairs, clusters, tetrads; Alpha or non-hemolytic; resemble colonies of Viridans Streptococci; thin cell walls, easily decolorized, can appear as gram negative; Oxidase (-); Catalase (-); PYR - variable.

GEMELLA Species

Four species have been associated with clinical infections: G. haemolysans, G. morbillorum, G. bergeriae, G. sanguinis.

LEUCONOSTOC

Morphology: GPC, irregular coccoid morphology, pairs and chains; Alpha or non-hemolytic; Habitat: plants, vegetables, dairy products; low virulence: need immunocompromised host; Oxidase (-); Catalase (-); PYR (-).

LEPTOSPIRA INTERROGANS

Contracted accidentally by man who comes in contact with contaminated water and animal urine or who are bitten by infected animal.

What are the two forms of LEPTOSPIRA?

Both free living (saprophytic) and pathogenic forms exist.

What is the pathogenic species of LEPTOSPIRA?

L. interrogans

What is the saprophytic species of LEPTOSPIRA?

L. biflexa

How can the saprophytic form of LEPTOSPIRA be distinguished from the pathogenic form?

The saprophytic form can grow at 10 degrees C or lower; the pathogenic form cannot.

LEPTOSPIRA Pathogenicity

Pathogenic form rapidly invades the bloodstream after entry and spreads throughout all sites in the body such as the CNS and kidneys.

BORRELIA RECURRENTIS

Causative agent of 'Relapsing Fever'; transmitted via louse or tick.

BORRELIA RECURRENTIS Diagnosis

Do direct exam on peripheral blood using Wright or Giemsa stain; look for spirochete (1 drop of blood with 1 drop of 0.85% saline); Darkfield microscopy - organism moves rapidly.

BORRELIA RECURRENTIS Symptoms

As antibody is produced, reemergence results in 2 to 15 days after infection; patients have an abrupt onset of fever, headache, and myalgia that lasts for 4 to 10 days.

MYCOPLASMAS

Smallest free living organisms, which can be cultured on artificial media.

MYCOPLASMAS Genera

Two Genera: (1) Mycoplasma (respiratory and urogenital) and (2) Ureaplasma (urogenital; can hydrolyze urea).

MYCOPLASMAS Habitat

Microbial flora of humans (oropharynx, upper respiratory tract and genitourinary tract).

Mycoplasma pneumoniae

May cause bronchitis, pharyngitis, or a relatively common respiratory infection known as Primary Atypical Pneumonia or 'walking pneumonia'.

Mycoplasma hominis

Found in lower genitourinary tracts in ~50% of healthy adults; can invade the upper genitourinary tract and cause salpingitis, pyelonephritis, pelvic inflammatory disease (PID), or postpartum fevers.

Ureaplasma urealyticum

Does not cause disease in the female lower genital tract but has been associated with ~10% of cases of nongonococcal urethritis (NGU) in men, as well as with upper female genitourinary tract disorders.

Structure of Mycoplasmas

No cell wall, pleomorphic.

Staining of Mycoplasmas

Dienes or Giemsa, Gram Stain not acceptable.

Culture of Mycoplasmas

Difficult to grow; need hypertonic, enriched media: heart infusion agar, 10% horse serum, yeast extract.

Penicillin G

Added to medium to prevent bacterial overgrowth; suppresses contaminating bacteria that do have cell walls; does not affect mycoplasma since it does not have a cell wall.

Growth characteristics of Mycoplasmas

Solid media: 'Fried Egg Colony' observed under 40x magnification; Broth: Faint turbidity; floating colonies.

Identification of Mycoplasmas

Source of specimen important: M. pneumoniae from respiratory tract; U. urealyticum from genital site.

Treatment for Mycoplasmas

Erythromycin (DOC), Tetracycline.

ELISA

Antigens from the sample to be tested are attached to a surface; a matching antibody is applied over the surface so it can bind the antigen.

Obligate Intracellular Bacteria

Use host's cell for reproduction which is similar to viruses.

Chlamydia

Obligate intracellular bacteria that do not produce own ATP; rely heavily on their host cell for energy.

C. trachomatis

One of the three species of Chlamydia that cause human infection.

C. pneumoniae

One of the three species of Chlamydia that cause human infection.

C. psittaci

One of the three species of Chlamydia that cause human infection.

Chlamydial Life Cycle

Elementary body (EB): extracellular, metabolically inert, infective form; Reticulate body (RB): intracellular growth, replicative form; entire life cycle takes 48-72 hours.

Rickettsia

Infects wild animals; Man is accidental host

Rickettsia identification methods

Biopsy of tissue, Serological, Enzyme Immunoassays, PCR with sequencing

Ehrlichia chaffeensis

Disease: Human monocytic ehrlichiosis

EHRLICHIA EWINGII

Vector: Ticks (Lone Star Tick -Amblyomma americanum)

ANAPLASMA

Disease: Human granulocytic anaplasmosis

COXIELLA BURNETTI

Causative agent of 'Q Fever'

KLEBSIELLA GRANULOMATIS

Formerly called Calymmatobacterium granulomatis