Lecture 11 & 12 Klebsiella, Enterobacter, Proteus, Serratia and Vibrio

Question 1

Describe the role of Klebsiella as an opportunistic pathogen

Answer 1

Common in soil and water. Klebsiella pneumoniae In GIT of 1/3 of humans, however this increases in hospitalised patients.
Secondary invader of lungs and causes bacterial pneumonia, UTIs, wound infections and septicaemia.

Question 2

Describe the role of Enterobacter as an opportunistic pathogen

Answer 2

Widely distributed in soil, water, on plants and in sewage and dairy products.
Several species can act as opportunistic pathogens and can cause UTIs, septicaemia, pneumonia and wound infections.

Question 3

Describe the role of Proteus as an opportunistic pathogen

Answer 3

Common in GIT of humans, highly motile and swarm on agar. Occasionally cause UTIs.

Question 4

Describe the role of Serratia as an opportunistic pathogen

Answer 4

Forms red pigments, found in water, soil, GIT of insects and occasionally humans. Can only cause infections in hospitals (Nosocimal infections)

Question 5

Describe the pathogenecity of cholera due to Vibrio cholorae

Answer 5

Causes cholera (diarrhoea, vomiting), infects humans only and is spread through faecal-oral route especially in unsanitary conditions.

Question 6

Describe the mode of action of the cholera toxin

Answer 6

The cholera toxin is an enterotoxin which causes permenant activation of adenyl cyclase in epithelial cells lining small intenstine and disrupts normal fluid uptake. It is encoded by a lysogenic, filamentous bacteriophage called CTX omega.

Question 7

Describe the classical and El Tor biotypes of vibrio cholerae regading infectivity, proliferation, resistance to dehydration and feature.

Answer 7

Infectivity - Classical is medium, El Tor is high
Proliferation - Classical is slow, El Tor is faster
Resistance to dehydration - classical is low, El Tor is higher
Feature - Classical gives a more severe disease, El Tor has higher environmental fitness.

Question 8

Describe the pathogenesis of gastroenteritis due to Vibrio parahaemolyticus

Answer 8

Free living in sea water and marine animals, causes over 50% of food poisoning in Japan. Incubation period is 10-20 hours.
When ingested causes acute gastroenteritis with watery diarrhoea that lasts a week.