Vectored Bacterial Infections

Question 1

reservoir

Answer 1

whatever life forms the pathogen is adapted to infect. the pool of hosts in which the pathogen is maintained

Question 2

vector

Answer 2

transmits between individuals in the reservoir

Question 3

borrelia burgdorferi (lyme disease) bacteriology

Answer 3

motile spirochete. flat-wave, not spiral. stainable with giemsa, silver stain, immuno fluorescence, and visible by standard microscopy. tick-borne on most common in US. small mammal reservoirs for nymphs, large mammals for adults. requires 24h attachment to transmit

Question 4

b. burgdorferi pathogenesis

Answer 4

begins with injection by tick. asymptomatic clearance posible. 6 months, organism spread. get rash, anti-spirochete/autoantibodies raised. persistent skin infection established. after 1 yr, immune/neuro things happen. HLA-DR4 and HLA-DR2 lead to lyme arthritis. 90% of untreated/undertreated cases report some neuro sequelae. reinfections occur

Question 5

b. burgdorferi exam stage 1

Answer 5

get history of outdoor activity. stage 1: erythema migrans expanding rashes at or near bite. bulls eye only in minority. rash around a still attached tick is hypersensitivity. flu-like constitutional symptoms. coinfection with erlichia or babesioa lead to high fever

Question 6

b. burgdorferi exam stage 2

Answer 6

musculoskeletal and/or neuro symptoms. intermittent arthritis, episodes last about a week and recur. if in europe, may get blue rash on ear or nipple. also get ACA, fibrosing skin process on extremities. neuroborreliosis with cranial neuropathy, memingitis, or rarely encephalopathy may need MRI. rarely cardiac involvement: arrhythmia or transient block. rarely opthalmic symptoms

Question 7

b. burgdorferi exam stage 3

Answer 7

chronic lyme disease. arthritis, subacute encephalopathy, chronic progressive encephalomyelitis, late axonal neuropathies, fibromyalgia, patient may recall earlier episodes of bell palsy, aseptic meningitis

Question 8

b. burgdorferi diagnosis: Lab

Answer 8

serology, ELISA, and IFA can confirm exposure, but not until 6-8 weeks later. patients who got briefly available lyme vaccine will be seropositive. seropositivity remains long term, and is not useful for testing the cure. positive titers can be confirmed by western blot. seronegativity is pretty reliable. elevated synovial and spinal fluid cell counds may suggest current activity. organisms may be culturable from the tick. examine CSF if neuro symptoms. PCR can be used

Question 9

what factor most complicates the development of a lyme vaccine

Answer 9

immunological: antibodies raised against lyme disease are not protective!

Question 10

b. burgdorferi treatment

Answer 10

treat patients who present with erythema migrans. attempt empiric treatment of patients who are seropositive with symptoms unless pregnant. amoxicillin or doxycycline, or ceftriaxone, cefuroxime, axetil. 10-30 days. dont add steroids. Jarisch herxheimer reaction expected

Question 11

relapsing fever bacteriology

Answer 11

louse-borne. From B. recurrentis, the vector is pediculus corporis. reservoir is humans. transmitted by louse curshing/inoculation by scratching. tick-borne are B.hermsii, turicatae, parkeri, duttonii, and others. reservoirs are many mammals and reptiles. usually transmitted by bite of infected tick.

Question 12

relapsing fever pathogenesis

Answer 12

spirochetes access vasculature, disseminate to spleen, bone marrow, liver, lungs, kidney, and CNS. IL10 response and neutralizing antibodies clear sepsis, leading to fever. spirochestes vary surface antigens, and eventually come back. fever repeats. louse borne have average of 1 relapse, tick have 3 relapses average. tick-borne can mess with pregnancy

Question 13

relapsing fever diagnosis: Exam

Answer 13

two or more episodes of 3-5 days of high fever, then a well week in between. in louse borne, also see jaundice, petechiae, hemoptysis, epistaxis, and CNS involvement.

Question 14

relapsing fever diagnosis: Lab

Answer 14

peripheral blood smear: spirochetes visible by microscopy, with wright or giemsa stain if blood taken during febrile period. can also visualize with IF, dark field, wet mounts, silver stained biopsies. CSF: mononuclear pleocytosis. can be cultured in special liquid medium. PCR and ELISA available

Question 15

relapsing fever treatment

Answer 15

tetracycline, doxycycline, erythromycin, penicillin G used in adults. erythromycin in kids and pregnant bitches. IV penicillin or ceftriaxone for meningitis. louse-borne takes one dose, tick-borne treat for 7-10 days. will see jarisch herxheimer rxn

Question 16

rickettsial pathogens similarities/differences to borrelia

Answer 16

similar: arthropod vectors, mammalian reservoirs, tetracycline sensitivity. unlike: small cocci to short rods, intracellular replication

Question 17

rickettsia bacteriology

Answer 17

very short rods. hard to stain. all (except Q fever) are vectored by arthropods. easily enter bloodstream and progress to bacteremia. obligate intracellular paracites. binary fission inside cells.

Question 18

most rickettsia infect humans ______

Answer 18

by accident!

Question 19

rocky mountain spotted fever pathogenesis

Answer 19

reproduce by binary fission only within host cells. invades and multiplies in vascular endothelium. virulence factors include OmpA and B (adhesion), type 4 secretion system (entry), phospholipase A2 (escape from endosome), ActA (actin-based cell-cell spread). rash happens when leakage from blood vessels occurs

Question 20

rocky mountain spotted fever diagnosis/presentation

Answer 20

begins headache, fever, myalgia. vasculitis: rash begins on extremities and spreads to trunk. May progress to delerium, coma, DIC, edema, circulatory collapse. most common on east coast. lab diagnosis by immunochemical methods

Question 21

treatment for rocky mountain spotted fever

Answer 21

doxycycline works so well that failed treatment suggests misdiagnosis. Chloramphenicol for prego people.`

Question 22

mediterranean spotted fever

Answer 22

shows with eschars (red sores with black spots in middle). transmitted by dog tick, common in europe, africa, central asia. begins with eschar at site of bite. severe cases can arise in old, alcoholics, G6PD deficient. same treatments as RMSF

Question 23

epidemic typhus

Answer 23

humans are normal host and reservoir. vectored by body louse, sometimes head or pubic lice. organisms come from previous human’s blood, multiplies in louse alimentary tract. bacteria multiply in vascular endothelium leading to vasculitis

Question 24

epidemic typhus symptoms

Answer 24

abrupt onset of fever and chills. generalized lymphadenopathy. abrupt onset unremitting headache. macular, macropapular, or petechial rash on day 4-7. begins on trunk and spreads out, opposite of RMSF. CNS symptoms are dullness, delerium, coma. uncommon: deafness/nonproductive cough. untreated course 2 weeks, mortality from vascular collapse or pneumonia.

Question 25

typhus patient history

Answer 25

louse bite, natural disaster or war, medical and military personnel, overcrowding, lack of personal hygiene. cold weather = epidemic typgus, warm weather = murine and scrub typhus

Question 26

brill-zinsser disease

Answer 26

recrudescent typhus. mechanisms of latency and reactivation are unknown. less severe than initial course. risk factors include malnutrition and improper or incomplete antibiotic therapy. may be seen in US among geriatric patients who had typhus during WWII.

Question 27

murine typhus

Answer 27

milder than epidemic typhus. accidental transmission to humans of cat/rat typhus. southern and southwest US

Question 28

scrub typhus

Answer 28

humans are accidental hosts to leptotrombidium akamushi vector and O. tsutsugamushi bacterium. milder than epidemic. 60% eschar forms at bite site. regional lymph node and pulmonary involvement common (cough)

Question 29

diagnosis of typhus

Answer 29

begin antibiotics before final confirmation. confirm with immunofluorescence assay or enzyme immunoassay or PCR.

Question 30

treatment of typhus

Answer 30

doxycycline or chloramphenicol. for recrudescent disease, a second course of antibiotic therapy is usually curative. azithromycin and rifampicin have been shown to be effective in small trials conducted in areas with known doxycycline resistance (thailand).

Question 31

E. chaffeensis bacteriology

Answer 31

tiny gram negative. obligate intracellular. reselmbles rickettsia. replicates in cytoplasm of white blood cells. forms clusters called morulae.

Question 32

human monocytic ehrlichiosis symptoms

Answer 32

often asymptomatic. symptoms may appear a week after bite: severe headache, myalgias, fever, shaking chills, GI symptoms. elderly or immunocomproised are at risk for severe ehrlichiosis, may develop meningitis or disseminated intravascular coagulation. co-infection of two tick-borne pathogens transmitted by the same vector do happen.

Question 33

human monocytic ehrlichiosis diagnosis

Answer 33

travel to endemic area, hiking. do a CBC (will see neutropenia, lymphocytopenia, or thrombocytopenia.) serum transaminases. morulae. confirm by PCR or immunostaining

Question 34

human monocytic ehrlichiosis treatment

Answer 34

doxycycline immediately! fluoroquinolones may be effective, chloramphenicol is not!

Question 35

human granulocytic ehrlichiosis and human granulocytic anaplasmosis

Answer 35

identified in wisconsin. clusters of small bacteria in neutrophils.

Question 36

anaplasma bacteriology

Answer 36

small, gram neg. obligate intracellular. reside in early endosome of white blood cells. grow into morulae. ehrlichia, anaplasma, and C. pneumoniae only organisms known to grow within neutrophils. ehrlichia, anaplasma, and C. pneumoniae only organisms that grow in neutrophils

Question 37

human granulocytic anaplasmosis diagnosis

Answer 37

present with fever, headache, myalgia, malaise, absence of skin rash. CBC shows penia of neutro, lympho, and thrombo. Serum transaminases. morulae. confirm by PCR or immunostain. rule out babesiosis and lyme.

Question 38

human granulocytic anaplasmosis treatment

Answer 38

doxycycline. chloramphenicol is not effective, fluoroquinolones may be.