Small G- Pathogens (chlamydiae, rickettsiae, ehrlichia) Flashcards
how small is chlamydiae?
.25 micrometers- .8 micrometers
just at limit of light microscopy
similar in size to some viruses
is chlamydia G+ or G-?
G-
LPS outer membrane and cytoplasmic membrane
does chlamydiae contain peptidoglycan?
no peptidoglycan (murein) in cell walls
- genes are present
- structure analogous to murein can be seen by EM
what type of pathogen is chlamydiae?
- obligate intracellular pathogen (cannot grow outside of host): grow only inside cells or on live tissues
- humans, animals, insects, protozoa
- small genomes (1-1.2 megabases)
*“energy parasites”: depend on host for ATP, auxotrophic for some amino acids
does chlamydiae have a simple development cycle?
NO,
- for infection
- for replication (metabolically active)
what are the 4 species formally recognized in chlamydia classification?
- c. trachomatis (3 biovars: multiple strains in each)
- c. pneumoniae
- c. psittaci
- c. pecorum
- 1 & 2 primarily found in human pathogens
- 3 &4 primarily animal pathogens, but some capable of causing disease in humans
flip for some general facts on chlamydial infections
- leading cause of preventable blindness in THE WORLD
- the MOST common agents of sexually transmitted bacterial infections
- speculation that every living adult has had pneumonia (“walking”) caused by c. pneumoniae
how is chlamydia spread?
- droplet or direct contact infection
- 4 F’s:
- fingers
- flies
- fomites
- fornication
where does chlamydia infect?
mucosal epithelial cells
is chlamydia infection localized or systemic?
localized
-eyes, lungs, genitalia
c. trachomatis infections are infections of the genital tract, what do they cause specifically in men and women?
men: prostitis, epididymitis
women: cervicitis, PID, premature births, pelvic pain, newborn eye/lung infections
both: urethritis, infertility, procitis, arthritis
is c. trachomatis usually asymptomatic in men or women?
WOMEN
chronic and repeat infections can cause sterility and or ectopic pregnancy
are c. trachomatis infections acute or chronic?
either!
there is a silent period- orgs location unknown
T/F: asymptomatic carriage results in most damage and scarring
TRUEIE
what two things can happen to infants during birth if the mother has chlamydia?
infection leading to:
- conjunctivitis
- pneumonia
how is chlamydiae internalized into a cell?
- extracellular
- elementary body (EB) transit form: not metabolically active
- entry of EBs into epithelial cells: masquerade as nutrients, growth factors, hormones to bind to specific receptors
- internalized by receptor-mediated endocytosis (endosomal vesicle that bacteria modifies for growth)
how do the EBs modify the endocytic vesicle?
- maintain pH above 6.2
- prevents vesicle from fusion with lysosomes
*vesicle is also modified with host components (glycolipids) for camouflage
what is a RB (reticulate body)?
metabolically active, in inclusion bodies get released from epithelial cells by exocytosis when reach a certain threshold
infectious EB change into larger intracellular active organisms (RB) which do what?
- synthesize molecules using host metabolites and energy
- divide by binary fission
how to RB uptake nutrients?
- tube-like structures (“drinking straws”) that allow them to feed on the eukaryotic host cell without leaving the inclusion vacuole
- 18-23 hollow tubes that protrude from bacterial cell cytoplasm into host cell cytoplasm
what is trachoma?
c. trachomatis strains that cause:
- inflamm of conjunctiva, can cause blindness, scarring cornea
-spread by direct contact with eye, nose,and throat secretions from affected individuals, or contact with objects such as towels and/or washcloths
what is lymphogranuloma venerum?
- STD
- systemic, invasive infection apparent in the lymph nodes that drain the genital tract
- predominately in developing countries:
- rare in US (200-400 cases)
- more common in africa, asia, india, s. america
T/F: chlamydophila pneumoniae perhaps is the least prevalent chamydial pathogen in the human population
FALSE its the most
50% of people up to the age of 20 have been infected, 80% of older adults
what kind of body response is elicited in chlamydophila pneumoniae infections?
- usually asymptomatic or acute respiratory response
- chronic resp. infections have been associated with asthma, CF, lung cancer
what type of condition is closely associated with chlamydophila pneumoniae infections?
ATHEROSCLEROTIC HEART LESIONS
40-100% of people with the previous have this infection
-usually not problematic unless you have some other disease with it
how are chlamydial infections treated?
- metabolic active RB forms are targets of antimicrobials
- four membrane layer to penetrate
- host cell plasma mem
- inclusion membrane
- chlamydial outer membrane
- chlamydial cytoplasmic mem
- orgs grow slow so antibiotics must be maintained for long time
are EBs susceptible to antibiotic treatement
no because they are not metabolically active
rickettsiae is in what shape?
small G- rods that don’t stain well
what type of pathogen are rickettsiae?
obligate intracellular bacteria
how are rickettsiae transmitted?
zoonoses: infections transmitted from animals to humans
are rickettsiae energy parasites like chlamydiae?
NO they can synthesize some of their own ATP and are capable of INDEPENDENT METABOLISM but they prefer to use host’s
do rickettsiae have flagella or endospores?
nopers
how are rickettsiae cultured?
- in animals
- in embryonated eggs
- in cell cultures in the lab
describe rickettsiae transmission? what is the common vector?
- rocky mountain wood tick and american dog tick
- once infected, a tick can carry the pathogen for life
- adult ticks feed on large mammals, including humans, larval and nymph forms feast on small rodents
- most tick species require blood meal before developing into next life stage
- during feeding as larva or nymph, ticks may become infected with the R. rickettsii bacteria
- bacteria pass on the infection to humans as adult ticks, during blood meal
- bacteria spread via bloodstream
how do rickettsiae attach for spread and multiplication?
- attach to VASCULAR ENDOTHELIAL CELLS (small blood vessels): induce endocytosis
- once inside, presumably lyse the phagosome (PHOSPHOLIPASE) and enter the cytosol
- engulfed through receptor mediated endocytosis
- mode of exit from cell VARIES
where does rickettsiae replicate?
cytosol
how does R. prowazekii exit the cell?
lysis
how does R. rickettsii exit the cell?
- gets extruded from the cell through local projections (filopodia)
- actin in the host cell associates with R. rickettsii and the actin helps to “push” the bacteria thru the filopodia
how does R. tsutsugamushi exit the cell?
- exits by budding thru the cell membrane
- remains enveloped in the host cell membrane as it infects other cells
- binds to neighboring cells=merging of membranes
T/F: the degree of injury to the host is proportional to the number of intracellular bacteria
TRUE
how are hemorrhagic spots created in infections with rickettsiae?
from lysis of cells resulting in the leakage of blood (rash)
can rickettsiae travel to the heart and brain?
for sure
T/F: 10% of patients will clear the infection even before antimicrobial treatment
75%%%%%
what are the 3 typhus group fevers caused by?
- R. prowazekii
- R. typhi
- Orientia (formeraly rickettsia) tsutsugamushi
describe the fever from R. prowazekii
typhus fever purplish rash, RECRUDESCENT typhus (reactivation of the dormant agent seen in US), transmitted by human lice
describe the fever from R. typhi
more prevalent and wide spread, MURINE TYPHUS, transmitted by rats and rat fleas
describe the fever from orientia tsutsugamushi
SCRUB TYPHUS, variety of antigenic types, NO RASH
what type of pathogen is Ehrlichia?
obligate intracellular bacteria
how is Ehrlichia transmitted?
by lone star tick
what immune cells does Ehrlichia infect?
- monocytes and macrophages
- human granulocytic ehrlichiosis (HGE) and human monocytic ehrlichiosis (HME)
what symptoms arise from infection with Ehrlichia?
fever, malaise, headache and myalgia
how does Ehrlichia develop first?
develops first as reticulate cells (RC) and then as dense-core cells (DC)
how are rickettsioses diagnosed?
- problematic:
- during 1st visit, pts don’t typically have fever or rash, and may not be aware of tick bite
- require eukaryotic cell cultures or innoculation of animals
- handling is notoriously hazardous
- clinical diagnostic tests
- antibody titers
- fluorescent antibody assay
- complement fixation
- latex agglutination
what is mycoplasma?
-smallest organisms capable of growth on cell-free media
what does mycoplasma require?
sterol (cholesterol) because bacteria don’t have a cell wall
what characteristic appearance does mycoplasma have?
fried egg appearance
does mycoplasma grow in small or large colonies and at a fast or slow rate?
small and slow
what does mycoplasma lack?
cell wall (no murein) so not sensitive to penicilin
where is mycoplasma found?
humans, other mammals, and birds
what are the 4 mycoplasma species that cause disease?
- m. pneumoniae: prototype mycoplasma, primary atypical pneumonia
- m. genitalium
- m. hominis
- ureaplasma urealyticum
* *2-4 are genitourinary tract infections
T/F: some mycoplasmas are part of the normal human oral flora
TRUEEE
what is the only reservoir of m. pneuominae?
humans
-unlike pneumococci, prolonged asymptomatic colonization is uncommon
are m. pneumoniae infections contagious?
mild and moderately contagious
spread through close-contact group
passed by respiratory droplets
describe “walking pneumonia.”
primary atypical pneumonia not cleared by penicillin, presents differently because just affecting respiratory epithelium
what epithelium does m. pneumoniae adhere to?
respiratory epithelium: terminal adhesion structures, tip-mediated attachment organelle
what are the main cells of the inflammatory response to mycoplasmas?
lymphocytes
what is unusual about the spread of mycoplasmas?
- largely limited to the respiratory mucosa that lines the airways
- doesn’t get into the lung alveoli
- bronchopneumonia
do mycoplasmas cause a lot of tissue destruction?
- no highly destructive of tissues, but ciliary function of bronchioles is impaired
- tissue toxic substances may include H2O2
- inflamm mediators
what other damage can mycoplasmas cause?
- hemolytic anemia
- IgM=cold hemagglutinins
- at lower temps, these antibodies cause RBCs to stick together & partial lysis, @ mucosal surfaces
- detectable in 50% of cases
- clinically significant hemolysis is rare
- encephalitis: spread to brain
- erythma multiforme (rash): systemic
which of the genital mycoplasmas is the newest emerging human pathogen, what can it cause, and where is it isolated from?
m. genitalium:
- urethritis, cervicitis, endometritis, PID
- isolated from synovial and resp fluids
- a lot like m. pneumoniae
which two genital mycoplasmas are frequently associated with disease in newborns?
- m. hominis and u. urealyticum
- commonly found in resp and genitourinary tracts
- present in most of the sexually active population
how are m. hominis and u. urealyticum isolated in newborns and do they always cause disease?
spinal fluid and they only cause disease in susceptible individuals
