Bacteriology

Question 1

What is the characteristic colony appearance of Bacillus anthracis when grown on culture media?

Answer 1

Mucoid or smooth colonies due to the presence of a capsule

Bacillus anthracis grows on most media at 37℃.

Question 2

What is the appearance of Bacillus anthracis in gelatin medium?

Answer 2

Inverted fir tree appearance

Question 3

What type of anthrax accounts for 95% of cases seen in humans?

Answer 3

Cutaneous anthrax

Question 4

Where are common sites for cutaneous anthrax infection?

Answer 4

Face, neck, hands, arms, and back

Question 5

What is another name for cutaneous anthrax due to its association with dock workers?

Answer 5

Hide porter’s disease

Question 6

What is the lesion called that occurs in cutaneous anthrax?

Answer 6

Malignant pustule

Question 7

What are the characteristics of the lesion in cutaneous anthrax?

Answer 7

Starts as a papule, becomes vesicular, congested, oedematous, with a central necrotic lesion covered by a black eschar

Question 8

What are the potential severe outcomes of cutaneous anthrax?

Answer 8

Fatal septicaemia or meningitis in 10-20% of cases

Question 9

How is inhalational anthrax contracted?

Answer 9

Inhalation of spores from dust of wool, hair, or hides

Question 10

What severe conditions can result from inhalational anthrax?

Answer 10

Hemorrhagic mediastinitis and sepsis

Question 11

What is the primary virulence factor of Bacillus anthracis?

Answer 11

Capsule composed of poly-d-glutamic acid

Question 12

What are the components of anthrax toxin?

Answer 12

Protective antigen, oedema factor, and lethal factor

Question 13

What type of animals are primarily affected by anthrax?

Answer 13

Herbivores such as goats, sheep, cattle, and horses

Question 14

How can humans become infected with Bacillus anthracis?

Answer 14

Contact with infected animals or their products

Question 15

What are the routes of entry for anthrax in humans?

Answer 15

• Injured skin (cutaneous anthrax)
• Inhalation (pulmonary anthrax)
• Ingestion of undercooked meat (gastrointestinal anthrax)

Question 16

What is the fatality rate associated with pulmonary anthrax?

Answer 16

High fatality rate

Question 17

What is the treatment of choice for anthrax in humans?

Answer 17

Ciprofloxacin

Question 18

What is the recommended prophylaxis for potential exposure to B. anthracis?

Answer 18

Ciprofloxacin or doxycycline for 4 weeks with vaccines

Question 19

What laboratory methods are used for the identification of Bacillus anthracis?

Answer 19

• Direct fluorescent antibody (DFA) test
• ELISA
• PCR

Question 20

What is the appearance of Bacillus anthracis colonies on blood agar?

Answer 20

Ground glass appearance with no haemolysis

Question 21

Describe the ‘medusa head’ appearance of Bacillus anthracis colonies.

Answer 21

Edges of the colony appear as long, interlacing chains of bacilli

Question 22

What are some preventive measures for anthrax?

Answer 22

• Disposal of animal carcasses by burning or deep burial
• Decontamination of animal products
• Protective clothing for handling infected materials
• Active immunization of domestic animals

Question 23

What are some other Bacillus species associated with human disease?

Answer 23

• Bacillus cereus
• Bacillus thuringiensis
• Bacillus sphaericus

Question 24

What is the diagnostic criterion for Bacillus cereus in stool samples?

Answer 24

Presence of ≥10⁵ bacteria/gram of stool

Question 25

What are the two forms of food poisoning caused by Bacillus cereus?

Answer 25

* Emetic disease * Diarrhoeal disease

Question 26

What is the incubation period for the emetic form of Bacillus cereus food poisoning?

Answer 26

1-6 hours

Question 27

What is the incubation period for the diarrheal form of Bacillus cereus food poisoning?

Answer 27

8-16 hours

Question 28

What is the bamboo-stick appearance associated with?

Answer 28

Gram-positive bacilli of Bacillus anthracis

Question 29

What is the typical clinical presentation of anthrax meningitis?

Answer 29

Haemorrhagic cerebrospinal fluid (CSF)

Question 30

What is the laboratory identification reaction for Bacillus anthracis?

Answer 30

M’Fadyean’s reaction

Question 31

What is the significance of the 'duckering' process in preventing anthrax?

Answer 31

Destroys spores on animal products using 2% formaldehyde solution

Question 32

What is C. botulinum?

Answer 32

C. botulinum is a bacterium that causes botulism, an intoxication associated with inadequate food preservation. ## Footnote It produces a potent neurotoxin that affects the neuromuscular junction.

Question 33

What is the primary method for diagnosing C. botulinum infection?

Answer 33

Diagnosis is essentially clinical and may involve specimens such as suspected food, faeces, vomitus, or wound specimens.

Question 34

What type of culture medium is used for C. botulinum?

Answer 34

Anaerobic culture of faeces on neomycin blood agar shows beta haemolytic colonies for most strains.

Question 35

Where are C. botulinum spores commonly found?

Answer 35

Spores are found in soil, sediments of lakes, ponds, coastal waters, decaying vegetation, and intestinal tracts of birds, mammals, and fish.

Question 36

What foods have been implicated in C. botulinum infections?

Answer 36

Home-canned foods, hams, sausages, fish, liver paste, honey, meat products, and vegetables.

Question 37

What is the mechanism of action of the botulinum toxin?

Answer 37

The toxin attaches to the neuromuscular junction and blocks the release of acetylcholine, resulting in flaccid paralysis.

Question 38

What are the preliminary symptoms of adult botulism?

Answer 38

Weakness, dizziness, dryness of mouth, nausea, and vomiting.

Question 39

What are the neurological symptoms of adult botulism?

Answer 39

Double vision, inability to swallow, speech difficulty, bulbar paralysis, constipation, and bilateral descending weakness of peripheral muscles.

Question 40

What is infant botulism?

Answer 40

Infant botulism occurs in the first year of life and is caused by ingestion of spores in contaminated honey.

Question 41

What is the treatment for infant botulism?

Answer 41

Patients typically recover with supportive therapy alone.

Question 42

What is wound botulism?

Answer 42

Wound botulism develops from contaminated wounds and has symptoms similar to foodborne botulism with a longer incubation time.

Question 43

What is the treatment for C. tetani infection?

Answer 43

Treatment includes nursing in a dark quiet room, human tetanus immunoglobulin, antibiotics (penicillins and metronidazole), and wound care.

Question 44

How is C. perfringens associated with necrotic enteritis?

Answer 44

Necrotic enteritis, also known as Pigbel, is caused by C. perfringens type C, which produces a β toxin.

Question 45

What are the symptoms of C. perfringens infection?

Answer 45

Severe abdominal pain, bloody diarrhoea, and vomiting.

Question 46

How is C. difficile primarily diagnosed?

Answer 46

Diagnosis involves clinical assessment and laboratory isolation of C. difficile from implicated food and stool.

Question 47

What are the two major toxins produced by C. difficile?

Answer 47

Toxin A (enterotoxin) and Toxin B (cytotoxin).

Question 48

What is the primary cause of antibiotic-associated colitis?

Answer 48

C. difficile causes antibiotic-associated colitis, also known as pseudomembranous colitis.

Question 49

What is the most potent toxin produced by C. botulinum?

Answer 49

Toxin A is the most potent known poison and is also used in cosmetic treatments like Botox.

Question 50

What is the treatment for C. difficile-associated diarrhoea?

Answer 50

Stop the offending antibiotic, administer oral metronidazole or vancomycin, and provide fluid replacement.

Question 51

What are the characteristics of Clostridium spp.?

Answer 51

Gram-positive bacilli, anaerobes, motile except for some strains, and produce oval or spherical spores under anaerobic conditions.

Question 52

What is the typical appearance of C. tetani spores?

Answer 52

C. tetani spores have a terminal drumstick appearance.

Question 53

What is the appearance of C. perfringens in Gram stain?

Answer 53

Large Gram positive, encapsulated bacilli.

Question 54

What is the characteristic symptom of gas gangrene associated with C. perfringens?

Answer 54

Crepitus in the subcutaneous tissue and muscle.