Term
|
Definition
• Bacteria which are obligate intracellular parasites
• Small gram (–) coccobacilli (0.3–0.5 μm)
• Cell membrane similar to gram (–) bacteria with LPS and peptidoglycan
• Spread by arthropod vectors – Lice,fleas,mites,andticks
• The rickettsial diseases of man are usually broken down according to the arthropod vector |
|
|
Term
| Rickettsiae vs ehrlichia vs coxiella |
|
Definition
• Rickettsia (11 species)
– Do not multiply within vacuoles and do not parasitize white blood cells
• Ehrlichia (2 species)
– Do not multiply within vacuoles, but do parasitize white blood cells
• Coxiella (1 species)
– Grows in vacuoles of host cells |
|
|
Term
|
Definition
– Ehrlichosis
– E. chaffeensis |
|
|
Term
|
Definition
– Rocky Mountain spotted fever
– Wild rodents
– R. rickettsia |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
• Coxiellaburnetiidiffersfromotherrickettsiainthatit is enclosed in a persistent vacuole during growth and division
– 6 to 10 daughter cells will form within a host cell before the cell ruptures and releases them
• No arthropod vector • Causes Q fever |
|
|
Term
| Prevention of tick borne illnesses |
|
Definition
• Avoidtick-infested areas.
– Wear protective clothing and use repellants.
– Ticks are difficult to eradicate as they can survive for 4 years without feeding.
• Remove ticks carefully |
|
|
Term
| Pathogenesis of rickettsia |
|
Definition
• During the first few days of incubation period:
– Localreactioncausedbyhypersensitivitytotickorvectorproducts
• Bacteria multiply at the site and later disseminate via lymphatic system.
• Bacteria are phagocytosed by macrophages (first barrier to rickettsial multiplication).
• After 7–10 days, organisms disseminate and replicate in the nucleus or cytoplasm of endothelial cells, causing vasculitis.
• After 2–6 days, a maculopapular rash develops, first on the extremities, including palms and foot soles, and spreading to the chest and abdomen.
• If left untreated, the rash will become petechial with hemorrhages in the skin and mucous membranes due to vascular damage as the organism invades the blood vessels.
• Death may occur during the end of the second week due to kidney or heart failure. |
|
|
Term
|
Definition
| entry, elementary body, initial body, morula, release |
|
|
Term
| pathogenicity of ehrlichia |
|
Definition
• Transmission
– To man, via the arthropod saliva, through a bite
• Arthropod vectors
– Rickettsia multiply in the epithelium of the intestinal tract
– They are excreted in the feces, but occasionally gain access to the arthropod’s salivary glands
• Mammalian host
– Found in the endothelium of the small blood vessels of the brain, skin, and heart |
|
|
Term
| Rickettsia Rickettsii disease/bacterial factors, transmission, risk, symptoms, geography/season, control |
|
Definition
• Disease/bacterial factors
– Rocky Mountain spotted fever
– Intracellular parasite that multiples in host cytoplasm
• Transmission
– Ticks are primary reservoir and vector
• Risk?
– Requires 24–48 hour exposure to feeding tick
– Individuals younger than 19 years old are usually at risk
– Males affected twice as often as females
•Symptoms
– Fever, chills, headache, myalgias, rash
• Geography/season
– Western hemisphere, southeast Atlantic, and south-central U.S.
– April–September • Control
– Tetracycline and chloramphenicol
– Avoid tick-infested areas – Insect repellent
– Remove ticks
– 35% mortality rate |
|
|
Term
| Rickettsia Prowazekii disease/bacterial factors, transmission, vector, geography/season, risk, control |
|
Definition
• Disease/bacterial factors
– Louse-borne typhus, Brill- Zinsser disease
• Transmission
– Humans are primary reservoir
– Inoculation through break in skin via body louse
• Vector
– Human body louse, squirrel • fleas
• Geography/season
– Central and SouthAmerica – Noseason
• Risk?
– Personsincrowded, unsanitary conditions
– Close contact with infected persons
Control
– Tetracyclines, chloramphenicol
– Louse control |
|
|
Term
| Rickettsia Typhi disease/bacterial factors, transmission, reservoir, vectors, geography/season, control, risk |
|
Definition
• Disease/bacterial factors – Strict intracellular pathogen
• Transmission
– Break in skin via infected flea
• Reservoir
– Rodents, cats, opossum, raccoons, and skunks •
• Vectors
– Rat and cat fleas
• Geography/season
– Global; southeast and gulf states of U.S.
• Control
– Tetracyclines, chloramphenicol
– Control of rodent vectors
• Risk?
– People in crowded areas infested with rodents |
|
|
Term
| Coxiella Burnetii disease/bacterial factors, reservoirs, transmission, geography/season, control, risk |
|
Definition
• Disease/bacterial factors
– Strict intracellular pathogen
– Multiplies in cytoplasmic vacuole
– Stable in harsh environments
• Reservoirs
– Sheep, goats, ticks, mammals, birds
• Transmission
– Inhaled airborne particle
– Contaminated unpasteurized milk
• Geography/season
– Global; rare in Canada and U.S.
– Not seasonal
• Control
– Tetracycline or chloramphenicol
• Risk?
– Livestock handlers
– Patients with prosthetic or damaged heart valves |
|
|
Term
| Ehrlichia Chaffeensis disease/bacterial factors, transmission, geography/season, control |
|
Definition
• Disease/bacterial factors – Ehrlichiosis
– Strict intracellular parasite – Vector lone star tick?
– Symptoms resemble RMSF
•Transmission
– Break in skin via infected tick
• Geography/season
– Common in Southeast, Mid- Atlantic, and south-central U.S.
– Most common May, June, July
• Control
– Tetracycline or
chloramphenicol
– Control of tick vector |
|
|
Term
| Laboratory Diagnosis of Rickettsiae-gram stain, special stains, culture and isolation, serologic testing |
|
Definition
• Presumptive of rickettsia-like organisms in tissue or blood
• Gram stain
– Stain poorly with gram’s stain. Although the organisms are gram-negative, they only weakly take the counter stain, safranin.
• Special stains
– Infected tissue may be stained with:
• Giemsa: bluish purple organisms
• Castaneda: blue organism against a red background
• Macchiavello stains: organisms are bright red against the blue background of the tissue
– Fluorescent-labeled antibody used to stain biopsy tissue.
• Culture and isolation
– Difficult and dangerous because of the highly infectious nature of
Rickettsiae
• Serologic test
– Weil-Felix test: based on cross-reactivity between some strains
of Proteusand and Rickettsia
– Complement fixation: not very sensitive; time consuming
• Positiveresultsat14daysafterinfection
– Indirect fluorescence (EIA): more sensitive and specific; allows discrimination between IgM and IgG antibodies, which helps in early diagnosis
– Direct immunofluorescence: the only serologic test that is useful for clinical diagnosis, 100% specific and 70% sensitive, allowing diagnosis in 3–4 days into the illness |
|
|
Term
| rickettsia confirmation testing |
|
Definition
• Serological reaction (Weil-Felix reaction) in which the titer of the agglutinins in the patient’s serum against the Proteus strains OX-19, OX-2, and OX-K are determined.
• These Proteus strains have no etiological role in rickettsial infections, but appear to share antigens in common with certain Rickettsia. |
|
|
Term
|
Definition
• Doxycycline is the drug of choice for treatment of all tick-borne rickettsial diseases in children and adults.
– Empirictherapyshouldbeinitiatedpromptlyinpatientswithaclinical presentation suggestive of a rickettsial disease.
– Tick-bornerickettsialdiseasesrespondrapidlytodoxycycline,andfever persisting for > 48 hours after initiation of therapy should prompt consideration of an alternative or additional diagnosis, including the possibility of coinfection.
• Doxycycline is recommended by the American Academy of Pediatrics and CDC as the treatment of choice for patients of all ages, including children aged < 8 years, with a suspected tick-borne rickettsial disease.
• Delay in treatment of tick-borne rickettsial diseases can lead to severe disease and death.
• In persons with severe doxycycline allergy or who are pregnant, chloramphenicol may be an alternative treatment for Rocky Mountain spotted fever
– However, persons treated with chloramphenicol have a greater risk for death compared with those treated with doxycycline.
• Chloramphenicol is not an acceptable alternative for the treatment of ehrlichiosis or anaplasmosis.
• Data on the risks of doxycycline use during pregnancy suggest that treatment at the recommended dose and duration for tick-borne rickettsial diseases is unlikely to pose a substantial teratogenic risk
• Prophylactic use of doxycycline after a tick bite is not recommended for the prevention of tick-borne rickettsial diseases.
• Treatment of asymptomatic persons sero-positive for tick-borne rickettsial disease is not recommended, regardless of past treatment status, because antibodies can persist for months to years after infection.
• The sulfonamides stimulate rickettsial growth and thus are contraindicated in the treatment of these diseases |
|
|
Term
| gram negative spirochetes |
|
Definition
• Gram-negative spirochetes
– Spirochete from Greek for “coiled hair”
• Extremely thin and can be very long
• Tightly coiled helical cells with tapered ends
• Motile by periplasmic flagella (aka, axial fibrils or endoflagella)
• Outer sheath encloses axial fibrils wrapped around protoplasmic cylinder
– Axial fibrils originate from insertion pores at both poles of cell
– May overlap at center of cell in Treponema and Borrelia, but not
in Leptospira
– Differing numbers of endoflagella according to genus and species |
|
|
Term
| Treponema species and diseases |
|
Definition
pallidum ssp. pallidum- Syphilis
(also Bejel, Yaws, Pinta) |
|
|
Term
| Borrelia species and disease |
|
Definition
burgdorferi (Lyme disease)- rodents deer domestic pets hard-shelled ticks are reservoir, hardshelled tick lxodes is vector
recurrentis (relapsing fever endemic, tick-borne) humans are reservoir, body louse/pediculus humanus is vector
Borrelia spp. (relapsing fever epidemic), rodents and soft-shelled ticks are reservoir, soft-shelled tick ornithodoros is vector |
|
|
Term
| leptospira species and disease |
|
Definition
| interrogans, Leptospirosis |
|
|
Term
|
Definition
• Too thin to be seen with light microscopy in specimens stained with gram stain or Giemsa stain
– Motile spirochetes can be seen with dark-field microscopy
– Staining with antitreponemal antibodies labeled with fluorescent dyes
• Intracellular pathogen
• Cannot be grown in cell-free cultures in vitro
– Koch’s postulates have not been met
• Do not survive well outside of host
– Care must be taken with clinical specimens for laboratory culture or testing |
|
|
Term
| Treponema Pallidum Epidemiology |
|
Definition
• Transmitted from direct sexual contact or from mother to fetus
• Not highly contagious (~30% chance of acquiring disease after single exposure to infected partner) but transmission rate dependent upon stage of disease
• Long incubation period during which time host is noninfectious
– Useful epidemiologically for contact tracing and administration of preventative therapy
• Prostitution for drugs or for money to purchase drugs remains central epidemiologic aspect of transmission |
|
|
Term
|
Definition
• Tissue destruction and lesions are primarily a consequence of patient’s immune response.
• Syphilis is a disease of blood vessels and of the perivascular areas.
• In spite of a vigorous host immune response, the organisms are capable of persisting for decades.
– Infection is neither fully controlled nor eradicated
– In early stages, there is an inhibition of cell-mediated immunity
– Inhibition of CMI abates in late stages of disease, hence late lesions tend to be localized |
|
|
Term
| Syphilis virulence factors |
|
Definition
• Outer-membrane proteins promote adherence
• Hyaluronidase may facilitate perivascular infiltration
• Antiphagocytic coating of fibronectin
• Tissue destruction and lesions are primarily result of host’s immune response (immunopathology) |
|
|
Term
| Pathogenesis of T. Pallidum— Primary Syphilis |
|
Definition
• Primary disease process involves invasion of mucus membranes, rapid multiplication, and wide dissemination through perivascular lymphatics and systemic circulation.
– Occurs prior to development of the primary lesion
• 10–90 days (usually 3–4 weeks) after initial contact, the host mounts an inflammatory response at the site of inoculation resulting in the hallmark syphilitic lesion, called the chancre (usually painless) .
– Chancre changes from hard to ulcerative with profuse shedding of spirochetes
– Swelling of capillary walls and regional lymph nodes with draining
– Primary lesion heals spontaneously by fibrotic walling-off within 2 months, leading to false sense of relief |
|
|
Term
| Pathogenesis of T. Pallidum— Secondary Syphilis |
|
Definition
• Secondary disease 2–10 weeks after primary lesion
• Widely disseminated mucocutaneous rash
• Secondary lesions of the skin and mucus membranes are highly contagious
• Generalized immunological response |
|
|
Term
| Pathogenesis of T. Pallidum— Latent Stage Syphilis |
|
Definition
• Followingsecondarydisease,hostenterslatent period
– First 4 years = early latent
– Subsequent period = late latent
• About40%oflatelatentpatientsprogresstolate tertiary syphilitic disease |
|
|
Term
| Pathogenesis of T. Pallidum— Tertiary Syphilis |
|
Definition
• Tertiary syphilis characterized by localized granulomatous dermal lesions (gummas) in which few organisms are present
– Granulomas reflect containment by the immunologic reaction of the host to chronic infection
• Late neurosyphilis develops in about one-sixth of untreated cases, usually more than 5 years after initial infection
– Central nervous system and spinal cord involvement – Dementia, seizures, wasting, etc.
• Cardiovascular involvement appears 10–40 years after initial infection with resulting myocardial insufficiency and death |
|
|
Term
| Pathogenesis of T. Pallidum— Congenital Syphilis |
|
Definition
• Congenital syphilis results from transplacental infection
• T. pallidum septicemia in the developing fetus and widespread dissemination
• Abortion, neonatal mortality, and late mental or physical problems resulting from scars from the active disease and progression of the active disease state |
|
|
Term
| gumma in skin or soft tissue |
|
Definition
| granuloma, has epitheloid cell, multinucleate giant cell, t cells, mycobacteria |
|
|
Term
| Syphilis Diagnosis testing |
|
Definition
• Dark field microscopy
• Screening tests
– Rapid plasma reagin (RPR)
• Detects antibody to cardiolipin- cholesterol-lecithin antigen
– Venereal disease research laboratory (VDRL)
• Test of choice for CSF?
– Treponema pallidum enzyme immunoassay (TP-EIA)
• Detects specific treponemal antigen
• Replacing RPR and VDRL (can be used on CSF)
• Measuring disease activity
– Use RPR and VDRL
– Rise shortly after chancre appears and peak during secondary syphilis
– Treatment hastens decline in levels |
|
|
Term
| syphilis confirmatory tests |
|
Definition
• Confirmatory tests
– Fluorescent treponemal antibody absorption (FTA-ABS)
– Microhemagglutination test for antibodies to T. pallidum (MHA-TP)
– T. pallidum particle agglutination assay (TP-PA)
• All positive screening tests must be confirmed with one of the above tests |
|
|
Term
| prevention and treatment of syphillus |
|
Definition
• Penicillin remains drug of choice
– WHO monitors treatment recommendations
– 7–10 days continuously for early stage
– At least 21 days continuously beyond the early stage
• Prevention with barrier methods (e.g., condoms)
• Prophylactic treatment of contacts identified through epidemiological tracing |
|
|
Term
|
Definition
• Associated with poverty, crowding, and warfare
• Arthropod vectors
– Louse-borne borreliosis = epidemic relapsing fever (Borrelia recurrentis)
• Transmitted person-to-person by human body lice (vectors) from infected human reservoir
• Infect host only when louse is injured ,e.g.,during scratching
• Therefore, a single louse can only infect a single person
• Lice leave host that develops a fever and seek normal-temperature host
– Tick-borne borreliosis = endemic relapsing fever (Borrelia
spp.)
• Sporadiccases
•Transmitted by soft body ticks (vectors) from small mammal reservoir
• Ticks can multiply and infect new human hosts
• Relapsing fever (aka, tick fever, borreliosis, famine fever) – Acute infection with 2–14 day (~ 6 days) incubation period – Followed by recurring febrile episodes
– Constant spirochaetemia that worsens during febrile stages |
|
|
Term
|
Definition
• Lyme disease was recognized as a syndrome in 1975 with outbreak in Lyme, Connecticut
• Transmitted by hard body tick (Ixodes spp.) vectors
– Nymph stage are usually more aggressive feeders
– Nymph stage generally too small to discern with unaided eye
– For these reasons, nymph stage transmits more pathogens
• White-footed deer mice and other rodents, deer, domesticated pets, and hard-shelled ticks are most common reservoirs
• Lyme disease characterized by three stages
– Initially a unique skin lesion (erythema chronicum migrans [ECM]) with general malaise • ECM not seen in all infected hosts • ECM often described as bull’s-eye rash • Lesions periodically reoccur
– Subsequent stage seen in 5–15% of patients with neurological or cardiac involvement
– Third stage involves migrating episodes of nondestructive, but painful, arthritis
• Acute illness treated with penicillin or tetracycline |
|
|
Term
| Leptospirosis Pathogenesis |
|
Definition
• Leptospirosis
– Also called Weil’s disease in humans
• Direct invasion and replication in tissues
• Characterized by an acute febrile jaundice and immune complex glomerulonephritis
• Incubation period usually 10–12 days with flu-like illness usually progressing through two clinical stages
– Leptospiremia develops rapidly after infection (usually lasts about 7 days) without local lesion
– Infects the kidneys and organisms are shed in the urine, (leptospiruria) with renal failure and death not uncommon
• Hepatic injury and meningeal irritation is common |
|
|
Term
| Leptospirosis Epidemiology |
|
Definition
• Mainly a zoonotic disease
– Transmitted to humans from a variety of wild and domesticated animal hosts
– In the U.S., most common reservoirs are rodents (rats), dogs, farm animals, and wild animals
• Transmitted through breaks in the skin or intact mucus membranes
• Indirect contact (soil, water, feed) with infected urine from an animal with leptospiruria
• Occupational disease of animal handling |
|
|
Term
| Leptospirosis Clinical Syndromes |
|
Definition
• Mild virus-like syndrome
• (Anicteric leptospirosis) Systemic with aseptic meningitis
• (Icteric leptospirosis) Overwhelming disease (Weil’s disease)
– Vascular collapse
– Thrombocytopenia
– Hemorrhage
– Hepatic and renal dysfunction
NOTE: Icteric refers to jaundice (yellowing of skin and mucus membranes by deposition of bile) and liver involvement. |
|
|
Term
| Leptospirosis clinical progression |
|
Definition
anicteric leptospirosis- septicemic 3-7 days (first stage) then immune 0 days - 1 month (second stage)
1st stage- myalgia, HE, ab pain, comitting, conjunctival suffusion, fever
2nd stage- meningitis, uveitis, rash fever,
pos in blood then csf (these 2 pos in 1st 10 days) then urine (pos after 1st week)
Lceteric leptospirosis (Well's syndrome)
first stage 3-7 days septicemic
second stage 10-30 days immune
both stages- jaundice, hemorghage, renal failure, myocarditis
pos in blood then urine (after 1st week) |
|
|
Term
| leptospirosis prevention/treatment |
|
Definition
• Do not swim or wade in water that might be contaminated with animal urine, or eliminate contact with potentially infected animals.
• Treatment
– Doxycycline or penicillin |
|
|
