Bacteriology-Bacillus | Quick Revision Notes for NEET-PG

Spread the love

Gram positive sporing rods/bacillus,motile by peritrichous flagella except B. anthracis(non-motile)

They are facultative anaerobs/aerobs.

Spores are common contaninants of culture media

In humans and animals(zoonotic) diseases are caused by 2 pathogens-

  1. B. anthracis
  2. B. cereus

Bacillus anthracis

  • Largest pathogenic bacterium
  • Spore wall 1st discovered by Robert Koch in this organism
  • Koch postulates were based on B. antharcis
  • 1st to be isolated in pure culture
  • 1st pathogenic bacteria seen under microscope
  • Anthracis is the 1st bacterial disease for which vaccine was prepared by louis Pasteur
  • Anthracis is the 1st communicable disease found to be transmitted by infected blood.
  • Anthracis is the 1st infectious disease for which a serological test was devised k/a Ascoli’s Thermoprecipitin test

Selective media – PLET medium

  • Polymyxin B
  • Lysozyme
  • EDTA
  • Thallous acetate medium

Microscopic appearance-

  • Box-cart appearance
  • Bamboo appearance
  • Strings of  pearls(in medium containing penicillin)

Culture appearance

  • Frosted glass appearance
  • Inverted fir tree appearance-seen in gelatin liquefaction
  • Medussa head colonies

Virulence Factors-

  • Capsule
    1. Polypeptide in nature
    2. Poly-a-glutamate capsule
    3. Anti-phagocytic capsule
    4. Demonstrated by MC Fadyean reaction(bacilli stained with polychrome methylene blue)
  • Toxin
    1. Made up of 3 fragements
      1. Fragement1/Edema factor
      2. Fragement 2/protective -Binds to host cell
      3. Fragement 3/lethal factor

 Fragement 1+2 -cause increase in cAMP causing edema

 Fragement 2+3 -cause cell death(Necrosis)


  • It is a zoonotic disease affecting sheep and cattle
  • Caused by B.anthracis
  •  Man gets infection from animal by 3 Is- Ingestion,Infection and Inhalation
  • It is of 3types

Cutaneous anthrax/Hide porter’s disease

Inhalational/pulmonary Anthrax

/wool sorter’s disease

Intestinal anthrax

Characterized by malignant pustules that turns into

black scab within 7-10 days of pustule formation.

(central necrotic lesion surrounded by edema)

Hallmrak-Haemorrhagic mediastinitis

-symmetric widening of mediastinum

Characterised by necrotic lesions in intestine

95% of cases of anthrax are cutaneous


Oropharyngeal antrax has also been reported

Sore throat/difficulty breathing, death occurs due to difficulty

in breathing as the throat swells.

Occurs due to exposure of skin to spores after handling sick animals or contaminated animal products. Spores gain access through tiny breaks in the skin

Occurs due to inhalation of spores

Due to swallowing of spores

Seen in farmers ,veterinarians and surgeons

Seen in workers working in animal hides infected with spores

Occurs due to ingestion of meat of an animal who has died from anthrax

Bacillus cereus

  • Motile non-capsulated bacillus
  • Cause food poisning and sometimes,opportunistic infections like endocarditis,bacteremia,etc
  • Food poisning is of 2 types

Emetic type

Diarrhea type

Incubation time-1-6 hrs

(median incubation period is 1hr)

Incubation time-8 to 16 hrs

Due to intake of preformed heat stable emetic toxin in boiled /fried Chinese rice

Due to intake of meat and vegetables containing

organisms which releases heat labile enetrotoxin

Purely toxic food poisoning

Causes Toxic-infective food poisning

By types-1,3,5

By types-2,6,8,9,10,12


Culture medium used- MYPA(Mannitol Egg Yolk Polymyxin B Agar)


Don't miss out!
Subscribe To Newsletter

Receive notification for future posts including medical notes, latest pdf uploads and much more in your mail to always stay updated!

Invalid email address
Give it a try. You can unsubscribe at any time.

Leave a Reply

Close Menu