Introduction to bacteria and disease

Question 1

a) example of acute bacterial diseases
b) example of chronic bacterial disease
c) example of bacterial disease involving a carrier

Answer 1

a) pneumonia, gastroenteritis
b) syphilis, tubercilosis
c) typhoid

Question 2

Modes of transmission
a) direct contact - horizontal
b) direct contact - vertical
c) indirect contact

Answer 2

a) sexual contact (syphilis, gonorrhoea), respiratory tract in air-borne droplet (upper: pharyngitis, scarlet fever, diptheria ; lower: whooping cough, tuberculosis, pneumonia, plague), contamination of own flora (UTI from GI tract), contact with skin/eyes (boils, impetigo, fasciitis, conjunctivitis, leprosy, anthrax)
b) transplacental (syphilis), parturition (gonorrhoea)
c) inanimate objects (nonsocomial - hospital acquired: UTI from catheterisation, surgical wound, burn infection) - caused by opportunistic pathogens (Staph aureus (MRSA), Pseudomonas aeruginosa), food (intoxication: Staph food poisoning, botulism ; infection: salmonellosis, E. coli 0157), water (faecal-oral: cholera, dysentry, typhoid ; respiratory - from air-con: Legionnaires’ disease), animal - zoonoses (livestock: brucellosis, leptospirosis, E. coli 0157 ; wild animals: Lyme disease), soil via wound - spores (tetanus, gas gangrene)

Question 3

Define (+ example)
a) endemic
b) epidemic
c) pandemic

Answer 3

a) disease that occurs regularly at low or moderate frequency (dental caries)
b) sudden appearance of disease, or increase above endemic level (diptheria)
c) global epidemic (cholera)

Question 4

Disease outbreaks (+ examples)
a) point source outbreaks (+ Legionnaires)
b) continuous source outbreaks
c) propagated outbreaks

Answer 4

a) arises from a single origin (food poisoning, nosocomial infections
Legionnaires disease (pneumonic disease caused by Legionella pneumophilia) contracted from aircon units
b) point source outbreak can become continuous source if the source is not eradicated (typhoid - carrier, travellers’ diarrhoae, food-borne infections, hospital acquired Staphylococci
c) host-to-host transmission results in even greater numbers of infections (whooping cough, tuberculosis, gonorrhoea, dysentry, cholera, typhoid)

Question 5

Plague as an example of point source, continuous source and propagated outbreaks

Answer 5

Bubonic plague caused by Yersinia pestis, spreads from rodents (point/continuous source) to humans, in which the disease becomes pneumonic (propagated person-to-person)

Cycle of Y. pestis in causing plague