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Bacillus
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- 1Describe bacillus speciesRod shaped, gram positive (in young cultures, look GN when they age), large (3-9um), can grow in chains
- 2Additional info regarding bacillus e.g. spore forming? aerobe or anaerobe? catalase?Spore-forming bacteria
Aerobes or facultative anaerobes
Catalase positive
Oxidase negative
Some motile (not B. anthracis)
Some beta-haemolytic on blood agar (not B. anthracis) - 3Where is it distributed and what is its main habitat?Widely distributed in the natural environment
Main habitat is soils (of all kinds)
Can contaminate anything not in sterile environment, e.g. food - 4What are the growth properties like for bacillus species?Under optimal conditions of growth, Bacillus species exhibit generation times of about 25 minutes.
Easily isolated and readily grown in the laboratory.
Grow well at room temperature and most common incubator temperatures.
Grow on wide variety of media. - 5Detail the surface structure of bacillus speciesCapsule
Contain either poly-D or L-gluramic acid
Or carbohydrate capsule
S-layer (Proteinaceous surface layer)
Peptidoglycan sheeting (several layers)
+ proteins on outer surface of plasma membrane.
Gram +ve cell wall made of peptidoglycan containing DAP.
Flagella - 6Describe the endospores e.g. where are they formed, how long do they last, are they resistant to anything ?Formed intracellularly
Eventually released as free spores
Most durable type of cell found in nature
Remain viable for extremely long periods of time
Resistant to heat, radiation, disinfectants and desiccation - 7Bacillus species are an opportunistic pathogen, state the most common infections.Anthrax – B. anthracis
Food poisoning – B. cereus
Traumatic infection:
Eye infections – via foreign body
After road traffic accidents – soil into wounds - 8What are some uses of bacillus species?Production of antibiotics
e.g. bacitracin from B. licheniformis or B subtilis
Production of vitamins –
e.g. vitamin B12 and B2 from B. megaterium, biotin and riboflavin from B. subtilis
Validation of disinfectants (B. cereus), monitoring of fumigation (B. subtilis), heat sterilization or radiation processes - 9State some other usesActive ingredient of probiotics
In various clinical tests:
uric acid assay
chlamydia detection assay
Production of industrial enzymes:
amylases, proteases and glucanases for food & alcohol industries - 10What are the two plasmids found in B. Anthracisand what do they encode?pX01 - encodes Lethal Factor (LF), oedema factor (EF) and protective Ag (PA).
pX02 - encodes antiphagocytic poly-D-glutamic acid (capsule) - 11What are the virulence factors of anthrax?Capsule – poly-D-glutamic acid which protects the bacterium from phagocytosis.
Anthrax toxin.
EF inhibits the immune response.
LF can cause a number of cell types to produce TNF-alpha, leading to septic shock. - 12What is cutaneous anthrax?->95% human cases (~80% of cases recover without treatment)
-via abrasion, cut, insect bite
-small pimple/papule develop within 2-3 days
-vesicles next 24hrs, followed by ulceration of the central papule which dries (black eschar) resolve 2-6weeks
-20% develop septicaemia and die - 13Describe GI anthrax-rare, mainly in Africa, Middle East, Central & Southern Asia
-ingestion of undercooked meat from anthrax infected animals
-incubation period : 2-5days
-2 clinical forms; abdominal & oro-oesophageal anthrax - 14Symptoms of the two types of GI anthrax?- Abdominal : Fever, haematemesis, bloody diarrhoea, septicaemia, death.
-Oro-oesophageal : sore throat, dysphagia, fever, cervical lymphadenopathy, oedema. - 15Describe inhalational anthrax-Flu-like Sx (Prodromal phase): mild fever, malaise, myalgia, fatigue, non-productive cough (2-5 days)
-acute dyspnoea, stridor, fever, cyanosis
-50% (if untreated) meningitis
-Mortality rate >95%
-X-ray : lungs clear but expanded mediastinum - 16Where tests are performed in the lab to diagnose anthrax?Gram stain
Capsule formation (bicarbonate agar)
Colony morphology (“medusa head” appearance, non-haemolytic on sheep blood)
Wide zone of lecithinase on egg yolk agar.
Gama-bacteriophage testing
Indirect hemagglutination
ELISA (serology)
Ascoli (precipitation) test - 17Treatment and prevention of anthrax?Destruction of clothing etc. by burning
Antimicrobial soap
Boiling items in water for >30 mins
Early antibiotic treatment essential (fluorquinolones (ciprofloxacin), doxycycline, vancomycin, erythromycin, penicillin).
Vaccines:
Acellular (BioThraxUSA)
Live attenuated (Russia) - 18Describe B. CereusGm+ aerobic or facultatively anaerobic
Rod shape bacilli
Spore forming
Ubiquitous in environment - 19What is the reservoir?Environment: soil, sediments, dust, vegetation. Food: cereal products, herbs and spices, dried foods, milk and dairy products, meat and meat products.
- 20What toxins does B. cereus produce?Produces 6 toxins:5 enterotoxin
i) Hemolysin BL (Hbl)
ii) Non hemolytic enterotoxin (Nhe)
iii) Enterotoxin T (BceT)
iv) Enterotoxin FM (EntFM)
V) Enterotoxin K (EntK)
Emetic toxin - 21What types of illness does it cause?Causing food borne illness & opportunistic infections
6 broad group:
Local infections – burns, traumatic / post surgical wounds, eye
Bacteraemia and septicaemia
CNS infections – meningitis, abscesses, shunt assoc infections
Respiratory infections
Endocarditis & pericarditis
Food poisoning – toxin induced emetic & diarrhoeagenic syndromes - 22What are the risk groups for non-food poisoning related infections?Neonates
IVDU (injection & heroin)
Immunocompromised pt (HIV, cancer)
Artificial prostheses (orthopedic implants, cerebrospinal shunts) - 23Describe the diarrhoea syndrome associated with B. CereusProfuse diarrhoea & cramping
Resembles Clostridium perfringens
Onset 8-16 h after ingestion of contaminated food (toxin formed in gut)
Mixture of 2 or more proteins with 36-45kD
Heat labile
Meats, vegetables, sauces - 24What lab tests diagnose B. Cereus?Culture on blood agar – large, flat, granular, ground glass,beta haemolytic colonies
Motile
Penicillin resistant
Resistant to bacteriophage γ
M’Fadyean stain –ve
(polychrome methylene blue) - 25What is the treatment for B. Cereus?Resistant to β lactam agent & 3rd gen cephalosporin.
Susceptible to aminogycosides, clindamycin, vancomycin, chloramphenicol and erythromycin.
B cereus food poisoning usually self limiting.
It can be prevented by good kitchen practices & safe cooking and storing of food.
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- Human Pathogens Fichas sobre Bacillus, creado por Zack Cooper el 22/12/2018.
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- Zack Cooper
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