Corynebacterium And Bacillus Multiple Choice Question And Answers

Question 1. A child with bull neck and membrane over tonsil. What is mechanism of the toxin responsible for this condition?

1. Increased cAMP
2. Inhibits GABA neurons
3. Inhibits Elongation Factor-2

Answer. (3) (Inhibits Elongation Factor-2)

• A child with bull neck and membrane over tonsil….suggestive of diphtheria
• Diphtheria toxin inhibits Elongation factor-2, which leads to inhibition of translation step of protein synthesis.

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Question 2. Which Corynebacterium carries toxin similar to that causing diphtheria toxin?

1. C.auris
2. C.jivelai
3. C.ulcerans

Answer. (3) (ulcerans)

BDS Notes	Dental Materials	Medicinal Chemistry
Clinical Medicine And Surgery	Pathology	General Medicine
Face Anatomy	Anatomy	Public Health Dentistry
Abdomen And Pelvis	Microbiology	Basic Dental Materials

Question 3. True about Corynebacterium diphtheriae:

1. All types produce toxin
2. Toxin production is dependent upon critical concentration of iron
3. Coded by plasmid
4. Inhibit cAMP

Answer. (2) (Toxin production is dependent upon critical concentration of iron)

1. Optimum con of iron (0.1 mg/L) is required for expression of diphtheria toxin.
2. Among the biotypes of C.diphtheriae, all most all strains of gravis, 95–99% strains of intermedius and 80–85% strains of mitis are toxigenic.

Question 4. Protein synthesis is inhibited by the toxin(s) of:

1. Pertussis
2. Cholera
3. Pseudomonas
4. Diphtheria
5. Shiga toxin

Answer. (3, 4, 5) (Pseudomonas, Diphtheria, Shiga toxin)

• Toxin that increases cAMP: Pertussis toxin, Cholera toxin, heat-labile toxin of coli, Anthrax toxin (edema factor)
• Toxin that increases cGMP: Heat-stable toxin of coli
• Toxin that inhibits protein synthesis:
  • By inhibiting ribosome: Shiga toxin and Verocytotoxin of coli
  • By inhibiting elongation factor 2-Diphtheria toxin and Pseudomonas toxin
• Neurotoxin:
  • Blocks the release of glycine and GABA: Tetanospamsin
  • Blocks the release of acetylcholine: botulinum toxin

Question 5. Metachromatic granules are seen in: (DNB Dec 2011)

1. Corynebacterium
2. E.coli
3. Yersinia
4. Pseudomonas

Answer. (1) (Corynebacterium)

• Metachromatic Granule is produced By C.diphtheriae, C.xerosis

Question 6. The type of diphtheria with highest mortality is:

1. Pharyngeal
2. Nasal
3. Laryngeal
4. Conjunctival

Answer. (3) (Laryngeal)

Formation of extensive pseudomembrane over larynx carries the risk of airways obstruction.

Question 7. True about diphtheria is:

1. Cause cranial nerve palsies in 2nd and 3rd weeks
2. Treatment with erythromycin
3. It is a gram-negative organism
4. Passive immunization is harmful and should not be tried

Answer. (1) (Cause…)

• Manifestations may appear during the first or second week of illness, typically beginning with dysphagia and nasal dysarthria and progressing to other signs of cranial nerve involvement.
  About other options
  Option b: Prompt administration of diphtheria antitoxin is critical in the management of respiratory diphtheria.
• Antibiotics have no role once the toxin is formed and are mainly used to prevent transmission to other susceptible contacts.
• Procaine penicillin G given for treatment and erythromycin given for carriers.
• Option c: C.diphtheriae is a gram +ve bacilli
• Option d: Passive immunization is critical in the management of respiratory diphtheria.

Question 8. The special stain used to identify diphtheriae in a throat swab is:

1. Albert’s stain
2. Giemsa stain
3. Gram’s stain
4. India ink

Answer. (1) (Albert’s stain)

Question 9. In a completely and adequately immunized child against Diphtheria, the throat swab was collecteIt showed the presence of Corynebacterium diphtheria like organisms on Albert staining. These organisms can have one of the following properties on further laboratory processing:

1. It can grow on Potassium tellurite medium
2. It would show a positive Elek’s gel precipitation test
3. It can be pathogenic to experimental guinea pigs
4. It can produce cytotoxicity in tissue cultures

Answer. (1) (It can grow on Potassium tellurite medium)

• This child is a carrier for C.diphtheriae.
• Adequate vaccination can prevent the disease but not the colonization.
  ‘Mass immunization might result in disappearance of toxigenic strains from many populations but has no effect on carriage of nontoxigenic strains.’
• Since the child is completely vaccinated, antitoxin level in serum can always neutralize the toxin but it can not prevent the colonization of nontoxigenic strain.
• So, the organism can be grown on Potassium tellurite medium but since it might be a nontoxigenic strain, so any test to detect the toxigenicity will be negative.

Question 10. A 12-year-old child presents with fever and cervical lymphadenopathy. Oral examination shows a grey membrane on the right tonsil extending to the anterior pillar. Which of the following medium will be ideal for the culture of the throat swab for a rapid identification of the pathogen?

1. Nutrient agar
2. Blood agar
3. Loffler’s serum slope
4. Lowenstein-Jensen medium

Answer. (3) (Loffler’s…)

• Rapid identification of diphtheria: Loffler’s serum slope (6–8 hour)
• Best media for isolation in carriers/contacts/convalescent: PTA (48 hour)
• Metachromatic granules best develops on: Loffler’s serum slope

Question 11. Metachromatic granules seen in: (NEET pattern-based) diphtheriae

1. C.Mycoplasma
2. Gardnerella
3. Chlamydia
4. Staphylococcus

Answer. (1, 3) (diphtheriae, Gardnerella)

Question 12. DOC for diphtheria carrier:

1. Erythromycin
2. Tetracycline
3. Penicillin
4. DPT

Answer. (1) (Erythromycin)

• DOC or carriers of diphtheria: Erythromycin

Question 13. Diphtheria carriers are diagnosed by:

1. Throat culture
2. Gram’s staining
3. Albert’s stain
4. Schick’s test

Answer. (1) (Throat culture)

• Carriers harbor the diphtheria bacilli in throat, hence can be effectively diagnosed by throat culture.

Question 14. A farmer who is also having dairy farm with history of handling cows, presented to the dermatology OPD with ulcer over forearm with central black eschar. True statement regarding the likely causative organism:

1. Coagulase positive
2. McFadyean’s reaction positive
3. Naglers positive
4. Satellitism positive

Answer. (2) (McFadyean’s reaction positive)

• Farmer with animal exposure followed by developing ulcer with eschar—suggestive of cutaneous anthrax
• Bacillus anthracis shows positive McFydean’s reaction due to presence of capsule.

Question 15. Wool sorter disease is:

1. Cutaneous anthrax
2. Pulmonary anthrax
3. Intestinal anthrax

Answer. (2) (Pulmonary anthrax)

Question 16. Eschar is formed by which of the following organism

1. B.henselae
2. B.anthracis
3. B.Staph aureus
4. E.coli

Answer. (2) (anthracis)

Question 17. An abattoir worker presented with a malignant pustule on his hand that progressed to form an ulcer. Smear was taken from the ulcer and sent to laboratory for investigation. The diagnosis is:

1. Cutaneous anthrax
2. Carbuncle
3. Ulcerating melanoma
4. Infected rodent ulcer

Answer. (1) (Cutaneous anthrax)

• Malignant pustule is the characteristic feature of cutaneous anthrax

Question 18. True about anthrax:

1. Cause by Gram-positive bacilli
2. Soil reservoir
3. Spore formation takes place inside the body
4. More common in carnivorous than herbivores
5. Penicillin is drug of choice

Answer. (1, 2) (Cause by Gram-positive bacilli, Soil reservoir)

• Option a: Bacillus anthracis is a Gram-positive bacilli
• Option b: Reservoir is animal and soil. Animal gets infection by inhalation of spores in soil
• Option c: Spore formation never takes place inside the body
• Please remember ‘spore formation takes place in unfavorable conditions and human body is a favorable environment for the organism like Bacillus anthracis causing anthrax and Clostridium perfringens causing gas gangrene.’
• Option d: Anthrax is more common in herbivores like sheep and cattle than carnivorous
• Option e: Jawetz 24/e p205 and 25/e p167 says- ‘Ciprofloxacin is recommended for treatment; penicillin G, along with gentamicin or streptomycin, has previously been used to treat anthrax.’

Question 19. Inverted fir tree appearance is characteristic:

1. Bacillus anthrax
2. Haemophilus influenzae
3. Yersinia pestis
4. Brucella

Answer. (1) (Bacillus anthracis)

• Inverted fir tree appearance in gelatin stab culture seen by Bacillus anthracis
• Bacillus anthracis laboratory findings 

Question 20. Anthrax bacilli differs from Anthracoid bacilli by being:

1. Noncapsulated
2. Strict aerobe
3. Nonmotile
4. Haemolytic colonies on blood agar

Answer. (3) (Nonmotile)

• Anthrax bacillus is capsulated, nonmotile and produce nonhemolytic colony on blood agar.
• Both Anthrax bacilli and Anthracoid bacilli are strict aerobe.

Question 21. All are true about cutaneous anthrax except:

1. Extremely painful
2. The whole area is congested and edematous
3. Central crustation with black eschar
4. Satellite nodule around inguinal region

Answer. (1) (Extremely painful)

Cutaneous lesions in Anthrax are painless.

Question 22. A person working in an abattoir presented with a pustule on his hand that progressed to form an ulcer. Smear is taken from the ulcer and sent to laboratory for investigation. Which of the following is the best stain to determine the causative agent of the ulcer?

1. Trichrome methylene blue
2. Carbol fuschin
3. Acid fast stain
4. Calcoflour white

Answer. (1) (Tric…)

• This is a case of Cutaneous anthrax (Points in favor abattoir occupation, pustule and ulcer on hand)
• Provisional diagnosis of Anthrax: demonstration of Capsule by polychrome methylene blue (M’ fadyean reaction)
• Confirmed diagnosis by immunofluorescence microscopy
• Cutaneous anthrax (Hide porter’s disease): MC (95%), but usually self limiting
• Occupation associated: Dock worker, butcher, abattoir, farmer.

Question 23. Bacillus anthracis, false statement is:

1. Gram-negative
2. Bacilli in long chain
3. Nonhemolytic colony in blood agar
4. Medusa head appearance on nutrient agar

Answer. (1) (Gram-negative)

Bacillus anthracis is gram-positive bacilli.

Question 24. Medusa head colony is seen in:

1. Bordetella pertussis
2. Bacillus anthracis
3. Bartonella henselae
4. Bacteroides species

Answer. (2) (Bacillus anthracis)

Question 25. Characteristic of Bacillus cereus food poisoning is:

1. Presence of Fever
2. Presence of Pain abdomen
3. Absence of Vomiting
4. Absence of Diarrhea

Answer. (2) (Presence…)

• Fever is not a consistent feature of cereus food poisoning.
• Abdominal cramps may be seen in both emetic and diarrheal type of cereus food poisoning.

Question 26. Incubation period for cereus:

1. 1–6 hrs
2. 8–16 hrs
3. 24 hrs
4. > 24 hrs
5. Weeks

Answer. (1, 2) (1–6 hrs, 8–16 hrs)

Emetic type: IP 1–5 hour
Diarrheal type: IP 8–16 hour

Question 27. Chinese restaurant syndrome after eating fried rice and vanilla sauce is due to:

1. Clostridium perfringens
2. Bacillus cereus
3. Staphylococcus aureus
4. Clostridium botulinum

Answer. (2) (Bacillus cereus)

• Chinese restaurant syndrome means: Food poisoning within 1–6 hr of consumption of Chinese fried rice ………… Most probable agent is Bacillus cereus.