Spirochetes Flashcards by Tiffany Irizarry

Characteristics of Spirochetes

Slender, helically coiled bacteria
Motile by endoflagella
Stain poorly with the Gram stain
Inactive biochemically
Microscopy:  dark-field, phase contrast, or fluorescence microscopic examination
Relatively unstable in the environment

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Characteristics of Leptospira Species

Slender, coiled spirochetes with hook-shaped ends
Obligate aerobes
Shed in urine of infected animals

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Differentiation of Leptospira species

Based on DNA homology
Nine species are recognized
Within a specie there may be multiple sero-vars
L. interrogans serovar canicola
L. interrogans serovar icterohemorrh

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Leptospira Epidemiology

Maintenance hosts
Rodents and small mammals
Infections are usually subclinical
Persistent shedding of leptospires in urine
Incidental hosts
Infections range from mild to severe
Transmission
Ingestion of contaminated water
Through skin and mucosal abrasions

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Leptospires of Pathogenesis

Leptospires are destroyed by gastric acid
Hematogenous spread
Dissemination to multiple organs
Nephritis 
Interstitial nephritis
 Immune complex-mediated renal damage (Type 3)
Anemia, icterus, and hemoglobinuria
Some serovars produce potent hemolysins
Hemorrhage
Vasculitis

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Leptospires of Pathogenesis part 2

CNS
Reproductive tract
Fetal death followed by resorption
Abortion
Birth of weak offspring
Immunity
Antibody-mediated

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Canine Leptospirosis

Icterus
Hemorrahages
Swollen Necrotic Liver

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Bovine and Equine Leptospirosis

Dark Swollen Kidney

Interstitial Nephritis

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Diagnosis of Lepto in Kidney

Direct fluorescent antibody stain of leptospires in the kidney

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Human leptospirosis

Synonyms

Weil’s disease; Fort Bragg fever; Swineherd’s dis-ease

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Human Leptospirosis

Transmission

Exposure to contaminated water

Exposure to infected animals

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Human Leptospirosis

Clinical Findings

Fever, anemia, jaundice, meningitis, nephritis, etc

Mortality: 10-15%

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Borrelia Characteristics

Largest of the spirochetes
Microaerophilic
Grow slowly—generation time of ≥ 18 hours
Arthropod-borne blood parasites
Vectors:  Ticks

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Borrelia burgdorferi

Lyme disease in humans, domestic and wild mammals
Vectors
Mice, deer, and ticks

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Lyme Disease

Pathogenesis

Bacteremia
Multiplication in the joints, brain, eyes, heart, etc
Role of immune complexes in development of arthritis, etc

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Lyme Disease

Dogs

Fever, arthritis, renal, cardiac, and CNS complications

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Lyme Disease

Horses and cattle

Arthritis, encephalitis, nephritis, hepatitis, LAMENESS etc

Lyme Disease in Humans

Transmission

Mostly by the nymph
Must remain attached for at least 36-48 hours
Removal of ticks

Lyme Disease in Humans

Clinical Findings

Characteristic “bulls eye” skin rash
Arthritis, headache, lymphadenopathy, etc
Complications: cardiac and neurologic signs

Lyme Disease Serology

Detection of IgM [2 weeks PI] or IgG [≥ 30 days PI] antibody
Indirect fluorescent antibody test
ELISA test
Positive test is confirmed with a Western blot assay

Borrelia coriaceae

Causes Epizootic bovine abortion

Epizootic bovine abortion

Transmission

Ornithodoros coriaceus

Epizootic bovine abortion

Clinical Findings

Cow—asymptomatic infection
Late-term abortion
Birth of weak calf

Brachyspira Species

Anaerobic spirochetes

Habitat: intestines of swine

Brachyspire hyodysenteriae

Swine Dysentery (bloody scours) in pigs

``` Reservoirs Rodents and carrier swine Transmission Fecal-oral transmission Virulence factors β-hemolysin and cytolysin ```

Swine Dysentery | Pathogenesis

Weaners and grower pigs Disease of the large intestines and rectum Necrosis and erosion of mucosa of large intes-tines, especially colon Mucohemorrhagic enteritis Chronic form—diphtheritic inflammation of the colon, cecum, and rectum

Characteristic of Bartonella henselae

``` Short, gram-negative, aerobic rods Fastidious growth requirements Organism grows very slowly Commensal of the oropharynx of healthy cats No disease in cats ```

Cat Scratch Disease

Cat to cat transmission is by Ctenocephalides felis No direct cat to cat transmission Humans: cat bite, scratch[es], contact with contaminated feces of cat fleas or cat saliva

Cat Scratch Disease | Clinical Finding

Papular lesions Chronic lymphadenitis May be self-limiting Parinaud's Oculoglandular Syndrome

Cat Scratch Disease | Diagnosis

History and clinical signs Serology: detection of B. henselae antibodies PCR: Detection of B. henselae DNA in tissues

Cat Scratch Disease | Treatment

Tetracyclines

Coxiella Burnetiis

Gram-negative, rickettsia-like organism Obligate intracellular bacterium Produces an endospore-like structure Resistant to heat, sunlight and many chemical disinfectants Low virulence Q [query] fever in humans; infection in do-mestic animals ** Only organism that is not transmitted by arthropod**

Coxiella burnetii | Reservoirs

Domestic and wild mammals; variety of arthro-pods | Cattle, sheep, and goats are the main reservoirs of infection for humans

Coxiella burnetii | Transmission

Arthropod transmission Inhalation Ingestion

Coxiella Burnetii in Ruminants

Transmission Inhalation, arthropod transmission, etc Nonpregnant animals Mostly inapparent infections Shed large numbers of organisms in urine, feces, milk and other body fluids Pregnant animals Shed billions of organisms in placental discharges Sporadic abortions in sheep and goats; rarely cattle

Q Fever in Humans

Inhalation of organisms; unpasteurized milk

Q Fever in Humans | Pathogenesis

Replication in vascular endothelium, respiratory epithelium, serosal epithelia, and in renal epithelia Widespread vasculitis and infarction of many organs Diffuse granulomas in many organs

Q Fever in humans | Clinical Findings

Fever, chills, headache, interstitial pneumonia, endocarditis, and hepatitis

Q Fever in Humans | Serology

Detection of C. burnetii antibodies | ELISA, IFA

Q Fever in Humans | Treatment

Doxycycline and tetracycline

Q Fever in Humans | Vaccination

Inactivated vaccine for people at risk