L7.2 Anaerobic +ve and Atypical organisms Flashcards
why is a mollicute an atypical organism
very small
no cell wall
why are rickettsia, coxiella and chlamydia atypical organisms
very small
obligate intracellular
what bacterium are in the mollicutes
mycoplasma
ureaplasma
what phylum of bacteria are mollicutes
tenericutes
low GC
soft skinned no cell wall
are mollicutes sensitive to antibiotics
resistant to those targeting cell wall as haven’t got one
what shape are mollicutes
pleomorphic
coccoid and rod
what is important to consider for mollicutes contamination
very small so can pass through filters - cell culture contaminants
what do mollicutes require
sterols
vitamins
nucleic acid precursors
are mollicutes saprophytic or parasitic
both
what is characteristic of mycoplasma pneumoniae
extracellular - smallest free living bacterium
where does mycoplasma pneumoniae infect
mostly mild upper respiratory tract infections
less opften atypical pneumonia and tracheobronchitis
other manifestations are rare (cardiac, neurologic, skin)
who does mycoplasma pneumoniae infect
worldwide; primarily infects school age children
what are the virulence factors for m. pneumoniae
P1 adhesin protein
superantigen proteins in cell membrane
toxins
how is mycoplasma pneumoniae spread
nasal secretions
how can mycoplasma pneumoniae infect again
immunity not life-long- can get again as adult
where do Mycoplasma hominis, Mycoplasma genitalium and Ureaplasma urealyticum colonise
genitourinary tract
how many people carry Mycoplasma hominis
15%
how many people carry Ureaplasma urealyticum
45-75%
what does M. genitalium and U. urealyticum cause
non-gonococcal urethritis
what does M. hominis cause
pelvic inflammatory disease (female upper genital tract infection) pyelonephritis (kidney inflammation)
what group are rickettsiaceae and anaplasmataceae in
rickettsiales - alpha proteobacteria
what group are coxiellaceae in
gamma proteobacteria
what is the difference in the cell wall for orientia
no peptidoglycan
what is the difference in the cell wall for rickettsia
minimal peptidoglycan
what do orientia and rickettsia cause
various forms of typhus and related diseases, depending on species
what is the reservoir for orientia and rickettsia
animals/arthopods
how do orientia and rickettsia invade cells
phagocytosis
escape from phagosome (phospholipase!)
Multiply in cytoplasm until cell dies (typhus group) or are constantly released (spotted fever group)
how if orientia and rickettsia diagnosed
microscopy
microimmunofluorescence (uses antibodies against LPS and OM proteins)
PCR-based assays, depending on species
what is the treatment for orientia and rickettsia
tetracycline, fluoroquinolones, chloramphenicol, depending on species
what does coxiella burnettii cause
causes Q fever
most are asymptomatic or mild flue-like symptoms
5% hepatitis, pneumonia, fevers
Chronic Q fever: can lead to endocarditis (significant mortality; mostly predisposed patients, e.g. immuno-suppressed)
what are the different coxiella burnettii variants
small cell variants (stress resistant)
large cell variants (metabolically active)
how is coxiella burnettii diagnosed
serological methods (immunofluorescence antibody and ELISA)
what type of pathogen is coxiella burnettii
intracellular
what are the reservoirs for coxiella burnetti
arthropods
birds
mammals: farm animals and pets
how is coxiella burnetti spread
resistant form can survive for years in soil, milk, faeces
infection via inhalation of contaminated material
what is an infectious dose of coxiella burnetti
≤10 bacteria
how is coxiella burnetti diagnosed
serological methods immunofluorescence antibody and ELISA
what is the treatment for coxiella burnetti
doxycyline; vaccines for humans and animals available
what is chlamydiaceae
obligate intracellular parasite
how do chlamydiaceae get energy
believed to use host ATP
what size are chlamydiaceae and why is this important
small can pass through 0.45uM filters
what are the 2 forms of chlamydiaceae in the lifecycle
elementary bodies
reticulate bodies
what is the chlamydiaceae lifecycle
elementary bodies invade in vacuole/phagosome, multiply in there convert to reticulate bodies
all in RB state = inclusion bodies (as vacuoles so big)
convert back to EB
cell lyse infect
cycle start again
what is the biovars of chlamydia trachomatis
trachoma (and urogenital infections) lymphogranuloma venereum (LVG)
what infection does chlamydia trachomatis cause
trachoma: infection of the eye (conjunctiva)
urogenital infections
what is the chlamydia trachomatis trachoma infection cause
scar inner surface of eye lids = eyelids turn inwards = erosion/ulceration of cornea = blindness
what is the chlamydia trachomatis urogenital infection cause in men
urethritis, epididymitis, infertility
how is chlamydia trachomatis transmitted
sexual transmission
what are the symptoms of chlamydia trachomatis
mainly asymptomatic
80% women
25% men
what is the chlamydia trachomatis disease spread in body like
progressive - genital ulcer may lead to, swelling of lymph nodes which may rupture, forming fistulas
what is the chlamydia trachomatis, chlamydia pneumoniae and chlamydia psittaci diagnosis
culture (requires viable cells)
serology, now routinely nucleic acid amplification tests (NAATs)
glycogen accumulation in inclusions of C. trachomatis
what does chlamydia pneumoniae cause
community acquired pneumonia
who does chlamydia pneumoniae infect
may be subclinical but more severe in elderly and asthmatics
60-80% of people worldwide become infected, but uncommon in childhood
what does chlamydia psittaci cause
ornithosis – from birds
flu-like symptoms
more severe systemic infection
what is the treatment for chlamydia trachomatis, chlamydia pneumoniae and chlamydia psittaci
doxycycline
macrolides
are clostridium spore forming
yes
what metabolism do mollicutes have
saccharolytic or proteolytic
what are the clinical manifestations of clostridium
gas gangrene
food poisoning
tetanus
antibiotic associated diarrhoea
where is clostridium perfringens a commensal
human and animal gut
what is the shape of clostridium perfringens
rod
what is the growth of clostridium perfringens like
rapid- fastest growing organism
what does clostridium perfringens make
toxins
haemolytic enzymes
what are the lethal toxins of clostridium perfringens
alpha
beta
epsilon
iota toxin
what is the the effect of clostridium perfringens type A
causes most human infections
largest amount of alpha toxin
effect of clostridium perfringens alpha toxin
lecithinase (phospholipase C), lyses many cell types - causes massive haemolysis, tissue destruction etc.
what causes clostridium perfringens double zone haemloysis
alpha and theta toxins
where does clostridium perfringens infect
soft tissue
what is cellulitis
localised gas formation in soft tissue
what is suppurative myositis
pus in muscle planes
what is myonecrosis
rapid muscle tissue destruction, gas gangrene
how can you become infected by clostridium perfringens
food poisoning
meat products with high spore (type A) numbers - survive heating and germinate if food not cooled
what does clostridium perfringens type C cause
clostridial necrotizing enteritis
tissue destruction in jejunum
what is the treatment for myositis and myonecrosis
must be initiated immediately
surgical removal of tissue and high dose penicillin
how is myositis and myonecrosis diagnosed
microscopy/culture (rapid growth)
what is the metabolism of clostridium tetani
proteolytic
what is clostridium tetani sensitive to
oxygen
what are the spores of clostridium tetani like
highly heat resistant
ubiquitous in soil, manure
what toxin does clostridium tetani have
tetanospasmin - heat labile neurotoxin
what is the lethal dose of clostridium tetani
2.5ng/kg
what does the clostridium tetani tetanospasmin do
blocks neurotransmitter release of inhibitory synapses = spastic paralysis
death by asphyxia/sudden cardiac arrest
what is the treatment for clostridium tetani
tetanus immunoglobulin, antibiotics (penicillin)
potent vaccine exists
where is clostridium tetani
ubiquitous
what does clostridium tetani contaminate
water food
what are the clostridium tetani toxins
7 main toxin types A-G
which clostridium tetani toxins are associated with human disease
A, B, E, F
how are clostridium tetani protected in digestive tract
complexed with non toxic proteins
effect of clostridium tetani toxin
inactivates proteins needed for acetylcholine release = no n=muscle excitation = flaccid paralysis = respiratory failure
what are the types of clostridium tetani infection
foodborne botulism
infant botulism
wound botulsim
what is infant botulism from
spores in honey, dust
what is the treatment for clostridium tetani
removed undigested food, give antitoxin and intensive therapy
what does clostridium difficle cause
antibiotic associated diarrhoea
how does clostridium difficle infect
spores spread infection
where is clostridium difficle a normal part of flora
gut of healthy individuals
2/3 babies
3% young adults
what disrupts the clostridium difficle to cause infection
heavy colonisation of gut following disruption of microflora:
antibiotics
chemotherapy
colonic obstruction
what toxins does clostridium difficle make
toxin A - enterotoxin
toxin B - sytotoxin
what is the effect of the clostridium difficle toxins
mucosal inflammation
apoptosis
diarrhoea
what is different about the clostridium difficle toxins
synergistic, but A or B-negative isolates both appear to be able to cause disease
what are the clostridium difficle diagnostics
immunoassay for toxin in stool/ nucleic acid amplification tests (NAATs)
what is the treatment for clostridium difficle
discontinue antibiotics (mild cases) metronidazole or vancomycin faecal transplants are an option! microflora from healthy = injected into gut
what makes an organism atypical
size
cell wall
life cycle
which group is
clostridium
low GC
firmicutes
what is the ‘respiration’ of clostridium
strictly anaerobic - oxygen tolerance varies
anaerobic cocci examples
Peptostreptococcus
how are chlamydia trachomatis biovars grouped
subdivided in serovars (based on Major Outer Membrane proteins), associated with specific diseases
what are bacterial stain are rickettsia, coxiella and chlamydia
negative
what is the chlamydia trachomatis urogenital infection cause in women
women: urethritis, cervicitis, pelvic inflammatory disease, infertility or ectopic pregnancy
what is the chlamydia trachomatis urogenital infection cause in babies
transmission to baby at birth: infant pneumonia, conjunctivitis, middle ear infection