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Micro/Immuno Part 2 > Intracellular Bacteria > Flashcards

Flashcards in Intracellular Bacteria Deck (29):

major intracellular pathogens

-Enterics-Shigella, E coli, salmonella, yersinia
-some bacilli (anthrax)
-rickettsial-rickettsia, ehrlichia, anaplasma and C burnetti
-some systemic fungal infections-histoplasma, cryptococcus
-all viruses


obligate intracellular

-Rickettsial-rickettsia, ehrlichia, anaplasma, c burnetti


facultative intracellular



recurring themes in intracellular pathogenesis 1

-use of infected macrophages for transport
-enterics-typhoid fever
-mycobacter- TB


recurring themes in intracellular pathogenesis 2

-enhance phagocytosis by target cell type
-alter endosome so that fusion fails
-enterics, legionella, mycobacter


recurring themes in intracellular pathogenesis 3

-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


recurring themes in intracellular pathogenesis 4

-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


recurring themes in intracellular pathogenesis 5

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


listeria bacteriology

-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


listeria pathogenesis

-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


listeria pathogenesis 2

-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


listeria treatment

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


listeria prevention

-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


Rickettsia bacteriology

-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



-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


Omp A and B




entry into cells


phospholipase A2

escape from endosome



actin based cell cell spread


RMSF diagnosis

-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


treatment for spotted fever

-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


chlamydia replication

-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


elementary bodies

-rigid outer membrane
-bind to receptors on epithelium of lung or mucus membrane and initiate infection


reticulate bodies

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


genital chlamydia

-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


reactive arthritis

-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


genital chlamydia diagnosis and exam

-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


urogenital chlamydia

-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


treatment for chlamydia

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