2. Bacterial diseases

Question 1

Intrinsic sources of bacteria, list 6 non-sterile sites

Answer 1

Bacteria already part of us
Nasal cavity and sinuses 
Upper respiratory tract
Mouth
Large intestine
Skin
Lower genital tract

Question 2

Extrinsic sources of bacteria

Answer 2

Portals of entry:
Expected: Normal (harmless) microbiota entering via an expected route (new-born infant and maternal microbiota)
Unexpected: Normal microbiota entering unusual site e.g. cut in skin

Question 3

List 5 routes of infection

Answer 3

Upper respiratory tract
Faeco-oral (enteric)
Urogenital tract
Skin
Intravenous

Question 4

List 7 Sources of bacteria

Answer 4

Upper resp tract (intrinsic + extrinsic)
Lower GI tract (intrinsic + extrinsic)
Sexual/urogenital tract (intrinsic + extrinsic)
Skin (intrinsic + extrinsic)
Nosocomial (all the above) 
Food + water
Animals

Question 5

Pathogenicity

Answer 5

ability to cause DISEASE

Question 6

Opportunistic bacteria

Answer 6

only cause disease when conditions are really permissive

Question 7

Commensal bacteria

Answer 7

Don’t cause disease

Question 8

Infectivity- List 5 features favouring initiation of infection

Answer 8

Transmission to host
Ability to colonise host
Tropism– Find unique niche (in or outside cells)
Replicate
Immune evasion at site of colonisation or niche

Question 9

Virulence- List 4 features that enhance disease causation and damage

Answer 9

Toxin production
Enzymes that degrade host molecules
Interruption of normal host processes
Complete immune evasion

Question 10

Infectious dose

Answer 10

No. of bacteria required to initiate an infection

Question 11

List 5 things Infectious dose can be affected by

Answer 11

Route of transmission
Ability to colonise host
Tropism and motility
Replication speed
Immune evasion at site

Question 12

What distinguishes pathogens from non- pathogens?

Answer 12

Ability to resist phagocytic killing

Question 13

2 Features that enhance disease causation:

S. pneumoniae

Answer 13

Toxin production

Degradation of host molecules

Question 14

2 Features that enhance disease causation:

S. aureus

Answer 14

Interference with host cell function

Immune evasion

Question 15

Give 2 examples of Mouth: droplet transmitted bacteria

Answer 15

Tonsillitis: Streptococcus pyogenes

Meningococcal septicaemia: Neisseria meningitidis

Question 16

Upper to lower respiratory tract and beyond examples

Answer 16

Streptococcus pneumoniae,
Streptococcus milleri,
Haemophilus influenzae

Question 17

List 3 Gram negative COCCI

Answer 17

Neisseria:
–Meningitidis-> Meningitis
–Gonorrhoeae-> Gonorrhoeae
Haemophilus influenzae-> Pneumonia

Question 18

List 4 Gram negative RODS

Answer 18

E. coli ->UTI and Diarrheal infections
Salmonella spp. ->Diarrheal infections and Typhoid
Vibrio cholerae
Shigella -> Dysentery

Question 19

List 5 Gram positive COCCI

Answer 19

Staphylococcus aureus 
Streptococcus:
–Group A= S. pyogenes
-> Sore throat
–Group B= S. agalactiae
-> Neonatal infections
–Viridans strep= dental bacteria
->Harmless 
–Pneumococcus= S. pneumoniae

Question 20

List 2 Gram positive RODS

Answer 20

Clostridium -> Diarrhoea

Listeria spp. ->Febrile illness