Small G- Pathogens Flashcards
characteristics of Chlamydiae
small
G-
is peptidoglycan (murein) found in walls of Chlamydiae?
no
structure analogous to murein seen in EM
True or false? Chlamydiae can only grow inside cells or live on tissues?
True - obligate intracellular pathogen
True or false? Chlamydiae produces its own energy
False, “energy parasite” which depends on host for ATP
auxotrophic for some AAs
T/F? Chlamydiae have a very simple developmental cycle
False, complex developmental cycle
What are the four species of Chlamydiae?
C. trachomatitis
C. pneumoniae
C. psittaci
C. pecorum
Which Chlamydiae species are primarily human pathogens?
C. trachomatitis
C. pneumoniae
General implications of Chlamydiae:
leading cause of preventable blindness
most common STI
leading cause of walking pneumoniae
how is chlamydiae transmitted?
droplet or direct contact
infect mucosal epithelium
how is chladmydiae spread?
4 Fs fingers flies fomites fornication
true or false? chladmydial infections are usually localized
true; eyes, lungs, genitalia (with exception of LGV which is invasive)
C. trachomatitis infection characteristics
usually asymptomatic in females
may be acute or chronic
genital tract infections
Describe process of C. trachomatitis invasion
EB enters epithelial cells disguised as nutrients, hormones, GFs
EBs internalized by receptor-mediated endocytosis
EBs modify endocytic vesicle
EB changes to larger, active form (RB) which synthesizes materials using host energy; divides by binary fission
C. trachomatitis: How do EBs modify endocytic vesicle?
maintain pH above 6.2
prevent vesicle fusion with lysosomes
modified with host glycolipids for camouflage
C. trachomatitis: how do RBs get their nutrients?
~20 drinking straws protrude from bacterial cell cytoplasm into host cell cytoplasm that let them feed on eukaryotic host cell without leaving inclusion vacuole
This chlamydial disease is characterized by inflammation of conjunciva which can cause blindness and scarring of cornea:
Trachoma - a strain of C. trachomatitis
spread by direct contact
Lymphogranulom venerum characteristics
STD
systemic, invasive (genital lymph nodes)
seen mostly in developing countries
C. pneumoniae characteristics
most common
usually asymptomatic or acute respiratory response
one can directly observe ___________ in majority of patients with atherosclerotic heart lesions
C. pneumoniae
Chlamydiae treatment
antimicrobial drugs that target metabolically active RB
maintain abx for a long time b/c organisms grow slowly
what are the 4 membrane layers a drug must penetrate when treating Chlamydiae?
host cell plasma membrane
inclusion membrane
chlamydial outer membrane
chlamydial cytoplasmic membrane
Rickettsiae is gram:
negative
Rickettsiae shape:
rods
Rickettsiae growth environment:
obligate intracellular bacteria
Rickettsiae transmission:
zoonoses - animal to human transmission
Rickettsiae energy source:
able to synthesize own ATP; independent metabolism
not an energy parasite like Chlamydiae BUT may lack some metabolites necessary for growth
Which pathogen is capable of independent metabolism and can synthesize its own ATP, Chlamydia or Rickettsiae?
Rickettsiae
Rickettsiae possess flagella or endospores?
no
How is Rickettsiae cultivated?
in animals, embryonated eggs, or cell cultures in lab
Rickettsial diseases
diseases caused by tick bites, flea feces, chigger bites
Ticks and Rickettsiae transmission
tick can carry pathogen for life once infected
adult ticks feed on large animals/humans
babies feed on rodents (often infected during this time)
blood meal required before next life stage
ticks most often pass on infection to humans during what time?
blood meal as adults
Once infected, Rickettsiae bacteria spreads via
bloodstream
Spread and multiplication of Rickettsiae
attach to vascular endothelial cells (sm. blood vessels)
induce endocytosis
once inside, lyse phagosome (phospholipase) and escape … enter cytosol
How do Rickettsiae exit host cell?
mechanism varies
- cell lysis
- extrusion from cell through local projections (filopodia)
- budding through cell membrane
How do Rickettsia leave host cell through filopodia?
host cell actin associates with bacteria and helps push it through host cell cytoplasm via filopodia
“comet like tail”
Describe host injury in Rickettsiae
proportional to # of intracellular bacteria
cell lysis results in blood leakage = rash (hemorrhagic spots)
organism can travel to other vessels (heart and brain)
most patients clear infection before antimicrobial tx
Typhus group fevers
R. prowazekii
R. typhi
Orienta tsutsu
R. prowazekii characterized by
typhus fever
recrudescent typhus (reactivation of dormant agent)
transmitted by lice
reservoir in humans and flying squirrels
R. typhi is characterized by
more prevalent and widespread
murine typhus
transmission via rats and rat fleas
Orientia tsutsu (Rickettsiae) is characterized by
scrub typhus
no rash
Ehrlichia growth environment:
obligate intracellular bacteria
how is Ehrlichia transmitted?
Lone star tick
What cells does Ehrlichia mainly infect?
macrophages and monocytes
Implications of Ehrlichia infection
fever, malaise, headache, myalgia
Human granulocytic ehrlichiosis (HGE)
Human monocytic ehrlichiosis (HME)
Spread and multiplication of Ehrlichia
Develop in host cell vacuoles as reticulate cells (RC)
then as dense core cells (DC)
How do Ehrlichia bacteria exit host cell?
exit host cell following rupture of morula and host cell cytoplasmic membrane
Why is Rickettsioses diagnosis difficult?
Asymptomatic and not aware of tick bite at first visit
Handling is hazardous
Diagnosis of Rickettsioses
eukaryotic cell cultures or inoculation of animal antibody titers fluorescent antibody assay complement fixation latex agglutination
Smallest organism capable of growth on cell-free media
Mycoplasma
Has a “fried egg” appearance when grown on cell-free media
Mycoplasma
Characteristics of mycoplasma
smallest organism that can grow on cell-free media
requires sterol (present in cell membrane)
small, slow growing colonies
no cell wall (no murein)
not sensitive to penicillin
found in other mammals and birds
T/F? Mycoplasma is susceptible to penicillin
False, not sensitive to penicillin
T/F? Mycoplasma possess a thick cell wall
false, no cell wall (no murein)
T/F? Some mycoplasms are part of normal human flora
true
Four mycoplasma species that are capable of causing disease
M. pneumoniae
M. genitalium
M. hominis
Ureaplasma urealyticum
This is known as the prototype mycoplasma
M. pneumoniae
primary atypical pneumonia
M. genitalium, M. hominis, and Ureaplasma urealyticum are responsible for
genitourinary tract infections
Reservoir for M. pneumonia
humans only - prolonged asymptomatic colonization is unlikely
T/F? Prolonged asymptomatic M. pneumoniae is common
False
How are M. pneumoniae infections spread?
close-contact groups
passed thru respiratory droplets
moderately contagious mild infection
Walking pneumonia is also known as _________ and is not cleared by _________
primary atypical pneumonia
penicillin
M. pneumoniae mode of entry
adhere to respiratory epithelium - terminal adhesion structures
tip-mediated attachment organelle
M. pneumonia adhere to respiratory epithelium via
terminal adhesion structures
Main cells of inflammatory response in M. pneumoniae
lymphocytes
T/F? Infection with M. pneumoniae is unlikely to spread
True ; limited to respiratory mucosa (doesn’t get into lung alveoli)
T/F? Infection with M. pneumoniae is highly destructive
False; but does impair ciliary function
may produce tissue toxic substances like H2O2
Other damage caused by M. pneumoniae infections
Hemolytic anemia
Encephalitis
Erythema multiforme (rash)
Hemolytic anemia seen in M. pneumoniae infections
IgM = cold hemagglutinins which cause RBCs to stick together in cold temperatures
M. genitalium is isolated from:
synovial and respiratory fluids
M. hominis and U. urealyticum mostly associated with
diseases in newborns
