Bacillus Flashcards
difference between spores of bacillus and clostridium?
spores of bacillus are of the same width as that of bacteria and do not produce bulge in the bacterial cell wall
what is the difference in motility between bacillus anthracis and other bacilli?
bacillus anthracis is non-motile, most have peritrichous flagella
why is anthrax bacillus historically relevant? #morphology
1st to be-
a) seen under microscope
b) first to be transmitted
c) first to be isolated
d) first to be used for vaccination
what gram stain does bacillus anthracis give? #morphology
gram positive
what acid fast stain does bacillus anthracis give? #morphology
acid fast negative
what part of bacillus anthracis is missing in human tissue but is present in culture?
describe them #morphology
spores
spores are oval/spherical, centrally located, same width as that of vegetative cell
what part of bacillus anthracis is missing in culture but is present in human tissue?
what is it in nature? #morphology
capsule,
it is polypeptide in nature
under what conditions are spores formed?
give two things that encourage spore formation #morphology
unfavourable conditions
distilled water and 2% NaCl
what inhibits formation of spores? #morphology
calcium chloride
what is McFaydean’s reaction used for? #morphology
used for presumptive diagnosis of anthrax
anthrax is a disease primarily for and secondarily for?
animals, humans
describe mechanism of McFaydean’s reaction #morphology
blood films containing anthrax are stained with polychrome methylene blue. After 10-12 seconds, amorphous purple material is noticed around the bacilli.
It represents the disintegrated capsular material which is characteristic of anthrax bacilli.
in cultures, what specific type of appearance do anthrax bacilli colonies have? #morphology
they have a “bamboo-stick appearance”
what does giemsa stain show? #morphology
it stains bacillus purple and capsule red
what is the temperature range for growth of anthrax bacilli?
what is the optimum temp.? #culture
12-45 degree celsius,
35-37 degree celsius
describe anthrax bacilli in nutrient agar media #culture
raised, opaque, greyish white colonies
“medusa head appearance”- interlacing chains of bacilli around the edge of the colonies resembling locks of matted hair
describe anthrax bacilli in blood agar media #culture
non-haemolytic though occasional strains produce narrow zone
describe anthrax bacilli in gelatin stab culture #culture
“inverted fir tree appearance”- liquefied mostly at the top because it is an aerobe
name selective medium for anthrax bacilli
name some components #culture
PLET medium
polymyxin, thallous acetate
solid medium containing pencillin #culture
“string of pearls reaction”- when anthrax bacilli is grown on solid medium containing penicillin, in 3-6 hours the cells become large, spherical and resemble a string of pearls
what is the importance of a string of pearls reaction? #culture
only b.anthracis gives positive but not b.cereus
2 differences between b. anthracis and b. cereus
- string of pearls reaction for b. anthracis
2. gammaphage lysis for b. anthracis
what sugars are fermented by b. anthracis? #biochemicalreactions
glucose, maltose, sucrose
what is the result of anthrax bacilli on catalase test? #biochemical reactions
positive
what is the result of anthrax bacilli on nitrates?
reduces nitrates to nitrites
what is the resistance of anthrax bacilli to heat?
- vegetative state- 60 degree celsius in 30 minutes
2. spore state- dry heat 140 degree celsius 1-3 hours, boiling 10 minutes
2 methods to destroy anthrax bacilli
- 4% potassium permanganate in 15 mins
2. autoclave in 15 mins (121 degree celsius)
2 methods to destroy anthrax bacilli in animal products and wool
- duckering- 2% formaldehyde 30-40 degree celsius for 20mins
- disinfection of wool- 0.25% 60 degree celsius for 6 hours
3 antibiotics that anthrax is susceptible to
penicillin, streptomycin, erythromycin
three antigens of anthrax bacilli and respective nature
- capsular antigen- polypeptide, acts as hapten
- cell wall antigen- polysachharide
- somatic antigen- heat labile protein, acts as antibody
two factors that determines virulence of anthrax
- capsular polypeptide
2. anthrax toxin complex
what does the anthrax toxin complex comprise of?
- PA (protective antigen) factor
- OF (oedema factor)
- LF (lethal factor)
function of PA
binds to receptor on target cell surface and provides attachment site for OF or LF
function of OF
Oedema factor is an adenyl cyclase which causes intracellular accumulation of cAMP causing oedema
function of LF
causes cell death
how does capsular polypeptide cause virulence
controlled by plasmid and inhibits phagocytosis
describe pathogenesis of anthrax in animals
in cattle and sheep by ingestion of spores
not by direct animal-to-animal contact
infected animal released bacilli from mouth, nose, rectum
how are humans affected by anthrax? name 3 routes. what’s common between them?
humans are affected secondarily by animals 1. cutaneous 2. pulmonary 3. intestinal common- septicemia and meningitis
cutaneous anthrax-
- etiology
- affected sites
- characteristic features
- prognosis
- by entry of spores into abraded skin- farmers and people holding carcasses
- face, neck and hands
- formation of pustule, acute inflamm. reaction causing congestion and oedema with central lesion called “black eschar”/malignant pustule
- generally resolves by itself, sometimes fatal septicemia
pulmonary anthrax-
- etiology
- affected sites
- characteristic features
- prognosis
- inhalation of dust or filaments of wool in factories; “wool sorter’s disease”
- lungs
- haemorrhagic bronchopneumonia, septicemia HIGH FATALITY
intestinal thorax-
- etiology
- characteristics
- prognosis
- rare in man, by eating improperly cooked meat
- violent enteritis with bloody diarrhoea
- high case fatality
what are the steps in lab diagnosis?
- specimen collection
- microscopy
- culture
- serology
- inoculation
- PCR
specimen collection in anthrax
cutaneous anthrax: swabs, fluid or pus- from pustules
pulmonary anthrax: blood samples
intestinal anthrax: peritoneal fluid or faecal samples
microscopy in anthrax
positive gram stain,
DFA (direct flourescent antibody test)
cell wall antigen test
mc-faydean’s reaction
inoculation in anthrax
white mouse/guinea pig die with 36-48 hours
serology in anthrax
ASCOLI’S THERMOPRECIPITIN TEST:
tissues ground up in saline and boiled for 5 mins, then extract is layered over anti-anthrax serum in a narrow tube- rings appears at the junction of 2 liquids within 5 minutes
when is ascoli’s thermopreciptin important?
for rapid diagnosis when sample is putrid
polymerase chain reaction is used for?
confirmation of anthrax bacillus
2 medicines for treatment of anthrax
doxycycline
ciproflaxin
prophylaxis of anthrax
factory hygiene, sterilisation of animal products
vaccines for humans- PA vaccines and live attenuated vaccines
vaccines for animals- Sterne vaccine
what are the 2 types of PA vaccine?
AVA (adsorbed) and AVP (precipitated)
what is sterne vaccine composed of?
spores of non-capsulated avirulent strain
route of administration of PA vaccines? doses?
intramuscular, 5 doses for AVA and 4 doses for AVP
requires annual booster
route of administration of live attenuated vaccines?
subcutaneous
what are anthracoid bacilli/pseudoanthrax baciili?
aerobic spore bearing bacilli resembling b. anthracis
name 3 anthracoid bacilli
- lichenforms- food poisoning
- stearothermophilus- autoclave testing
- subtilis- eye infection
what does bacillius cereus cause? types?
food poisoning
1. short incubation period and 2. long incubation period
features of short incubation period food poisoning
- acute nausea and vomiting
- 1-5 hours
- from cooked rice in Chinese restaurants
- RARE diarrhoea
features of long incubation food poisoning
- acute abdominal pain and diarrhoea
- 8-16 hours later
- RARE vomiting
- contaminated food
pathogenesis in B. Cereus is because of?
enterotoxin production: diarrhoeal type- e. coli type enterotoxin and emetic type- staphylococcal type enterotoxin
3 differences between B. Cereus and B. Anthracis?
- non-motile/motile
- no lysis/lysis by gammaphage
- no DFA test/ DFA test
- non-capsulated/capsulated
