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Micro/Immuno Part 2 > Intracellular Bacteria > Flashcards

Intracellular Bacteria Flashcards

1
Q

major intracellular pathogens

A
  • Neisseria
  • Enterics-Shigella, E coli, salmonella, yersinia
  • mycobacter
  • some bacilli (anthrax)
  • legionella
  • listeria
  • rickettsial-rickettsia, ehrlichia, anaplasma and C burnetti
  • chlamydia
  • some systemic fungal infections-histoplasma, cryptococcus
  • all viruses
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2
Q

obligate intracellular

A
  • chlamydia

- Rickettsial-rickettsia, ehrlichia, anaplasma, c burnetti

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3
Q

facultative intracellular

A
  • legionella
  • listeria
  • neisseria
  • mycobacter
  • enterics
  • bacilli
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4
Q

recurring themes in intracellular pathogenesis 1

A
  • use of infected macrophages for transport
  • enterics-typhoid fever
  • mycobacter- TB
  • fungi-histoplasma
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5
Q

recurring themes in intracellular pathogenesis 2

A
  • T3SS
  • enhance phagocytosis by target cell type
  • alter endosome so that fusion fails
  • enterics, legionella, mycobacter
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6
Q

recurring themes in intracellular pathogenesis 3

A
  • actin based motility and cell cell spread
  • virulence factors with names like ActA
  • generate actin tail behind bacteria free in the cytoplasm
  • bacteria can eventually ram though cell membrane into next cell
  • listeria, shigella
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7
Q

recurring themes in intracellular pathogenesis 4

A
  • evasion of humoral immunity, surface defenses
  • enterics-M cells as gateway to exterior surface of intestine, works around colonization resistance and tight junctions on interior surface
  • actin based cell cell spread allows infection of new cells without exposure to humoral immunity
  • CMI required to clear infection
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8
Q

recurring themes in intracellular pathogenesis 5

A
  • effective antibiotic treatment for intracellular replicators must penetrate human cell membrane
  • tetracyclines are first choice
  • contraindicted in pregnancy
  • alternates are azithromycin and chloramphenicol
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9
Q

listeria bacteriology

A
  • small gram pos rod
  • facultatively anaerobic
  • blue green sheen on non-blood agar
  • forms Ls and Vs, resembles corynebacteria
  • tumbling motility by temperature sensitive flagella
  • beta hemolytic
  • grows well in cold
  • environmental- found on animals, plants, soil
  • intracellular life style protects it from antibodies and complement
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10
Q

listeria pathogenesis

A
  • infection from environmentally contaminated food, outbreaks share common meal/food vendor
  • causes gastroenteritis, seldom dangerous to previously healthy
  • patients immunosuppressed, including pregnancy
  • if immunosuppressed- escapes GI tract causes complications of pregnancy. meningitis, abscess, endocarditis, septic arthritis, osteomyelitis, rarely pneumonia
  • mortality is 20-30% in immunosuppressed, low mortality in pregnant women but 22% fetal/neonatal death
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11
Q

listeria pathogenesis 2

A
  • pregnancy- bacteria escape GI and proliferate in placenta
  • particularly in 3rd trimester, when CMI is lowest
  • commonly causes preterm labor, may cause abortion, still birth, intrauterine infection
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12
Q

listeria treatment

A
  • antibiotics are indicated, IV if CNA or bacteremic
  • ampicillin for up to 6 weeks with Gentamicin combo for first week
  • reportable because causes epidemics
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13
Q

listeria prevention

A
  • cook food thoroughly, wash hands, knives, and cutting boards
  • wash raw veggies
  • avoid unpasteurized dairy
  • if pregnant/immunocompromised-reheat leftover or ready to eat foods until steaming (including deli meat)
  • no soft cheeses
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14
Q

Rickettsia bacteriology

A
  • very short rods
  • hard to stain-gram neg
  • all except c burnetti (Q fever) are vectored by arthropods (reservoirs maintain infection in environment)
  • easily enter blood stream
  • obligate intracellular-binary fission inside cells, need tissue culture
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15
Q

RMSF

A
  • vectored by dog tick
  • common in eastern US
  • invades and multiplies in vascular endothelium
  • virulence factors OmpA&B, T4SS, Phospholipase A2, ActA all cause blood vessels to burst and make tiny dots that is the rash
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16
Q

Omp A and B

A

adhesion

17
Q

T4SS

A

entry into cells

18
Q

phospholipase A2

A

escape from endosome

19
Q

ActA

A

actin based cell cell spread

20
Q

RMSF diagnosis

A
  • headache
  • fever
  • myalgia
  • vasculitis-rash begins in extremities and spreads to trunk-common but not universal
  • may progress to delerium, coma, DIC, edema, circulatory collapse (18% untreated mortality)
  • actually most common on east coast
  • patient may not recall tick bite
  • can be diagnoses immunochemically in lab
21
Q

treatment for spotted fever

A
  • doxycycline works so well that treatment failure suggests misdiagnosis but unsafe in pregnancy
  • AAP allows for chilren
  • chloramphenicol is alternate for pregnant and allergic
  • prevention-protective clothing and insect repellant
22
Q

chlamydia replication

A
  • elementary body gets into cell, in endosome, prevents fusion via its T3SS
  • elementary body changes to reticulate body
  • reticulate body divides and multiplies
  • some change back to EBs
  • inclusion granule has both
  • can either bud off or burst in cell and cause cell to burst
  • reticular bodies don’t survive long on their own
23
Q

elementary bodies

A
  • small
  • infectious
  • rigid outer membrane
  • rugged
  • bind to receptors on epithelium of lung or mucus membrane and initiate infection
24
Q

reticulate bodies

A
  • non-infectious intracellular form
  • metabolically active
  • replicating
  • synthesizes its own DNA, RNA, and proteins, but requires ATP from host
  • fragile gram neg membrane
  • inclusions accumulate 100-500 before release
25
Q

genital chlamydia

A
  • 4 million infections per year-most commong
  • > 10% in sexually active adolescent females
  • often asymptomatic-male reservoirs
  • most commonly local mucosal inflammation and discharge-urethritis or vaginitis or cervicitis
  • infection increases risk of acquiring HIV
  • pregnant woman infected can pass the infection to their infants during delivery
  • can lead to PID-chronic pain and ectopic pregnancy
  • can lead to reactive arthritis
26
Q

reactive arthritis

A
  • secondary to immune mediated response
  • may present as asymmetric polyarthritis, urethritis, inflammatory eye disease, mouth ulcers, circinate balanitis and keratoderma blennorrhagica
  • 80% of affected patients are human leukocyte antigen B27 positive
27
Q

genital chlamydia diagnosis and exam

A
  • women-easily induced endocervical bleeding, mucopurulent endocervical discharge, intermenstrual bleeding, dysuria, abd pain
  • men-urethral discharge, urinary frequency/urgency, dysuria, scrotal pain/tenderness, perineal fullness
28
Q

urogenital chlamydia

A
  • test for co-incident chlamydia in all STD patients
  • physical findings are often sufficient for diagnosis, but labs:
  • cytologic-for infant ocular trachoma, cell sample stained with giemsa or IF
  • isolation in cell culture-grows well in variety of cell lines, always do culture if case has legal implications
  • chlamydial ribosomal RNA by hybridization with DNA probe-simpler and less expensive, but more likely to give false positive

ELISA and PCR from urine or exudate possible, serology not useful-past infection too common

29
Q

treatment for chlamydia

A
  • intracellular
  • doxy or azithromycin
  • erythromycin or amoxicillin-test the cure
  • can be hidden behind gonococcal-test panel
  • reinfeciton common-treat partners

Micro/Immuno Part 2 (17 decks)

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