Lecture 7

Question 1

Major microbial causes of diarrhoeal disease in NZ

Answer 1

Campylobacter, Salmonella, Yersinia, VTEC/STEC, Shigella

Question 2

Major microbial causes of diarrhoeal disease in developing countries

Answer 2

Cholera: water-borne, 11% of <5y.o. deaths, 1.5mil dead/year (120,000 cholera, 600,000 rotaviruses), 2billion cases per year (5mi Cholera) of diarrhoeal disease, 2nd leading infectious cause of death in children under 5

Question 3

Major microbial causes of diarrhoeal disease in the developing and developed world

Answer 3

Campylobacter: food-born

Question 4

Major microbial causes of diarrhoeal disease in the developed world

Answer 4

Clostridium difficile: hospital acquired

Question 5

Cholera causative agent

Answer 5

Vibrio cholera

Question 6

Diagnostic of Cholera

Answer 6

Gram-negative, comma shaped rod, oxidase positive (produces cytochrome C)

Question 7

Souce of Cholera

Answer 7

Reservoirs, contaminated drinking water (e.g. following Haiti earthquake and in developing countries without effective water and sewerage treatment), Shellfish in coastal waters

Question 8

Route of transmission of Cholera

Answer 8

water-borne (contaminated water supplies), human carriers (faecal oral route)

Question 9

risk factors for infection of Cholera

Answer 9

unsafe drinking water (usually in developing countries or if there’s a natural disaster)

Question 10

Colonisation area of Cholera

Answer 10

Intestines

Question 11

key virulence factors of Cholera

Answer 11

pilus and AB5 toxin (1 activity sub-unit, 5 binding sub-units)

Question 12

The action of the AB5 toxin of Cholera making it a virulence factor

Answer 12

causes chloride secretion by cells which have taken up the AB5 toxin

Question 13

early symptoms of Cholera

Answer 13

tired, dry skin, thirsty, headache

Question 14

progression of symptoms of Cholera

Answer 14

decreased urine output, dark urine, vomitting (intoxifications, nausea, 1-2L/day), diarrhoea (acute, watery, bloody(dysentery), severe(x6/day), rice water stool (<20L/day)), dehydration leading to shock, abdominal pain, fever

Question 15

What sample is tested to diagnose Px with Cholera?

Answer 15

Stool

Question 16

treatment options for Cholera

Answer 16

• oral rehydration therapy or IV line (clean water, salts, sugar = oral rehydration salts (ORS))
• antibiotics for severe cases and moderate cases - doxycycline - reduced shedding (reduces transmission), cheap, kills V.cholera, use after vomiting phase, reduces the duration of symptoms

Question 17

prevention options for Cholera

Answer 17

good hygiene and improved sanitation, safe drinking water

Question 18

The causative agent of campylobacteriosis

Answer 18

Campylobacter jejuni

Question 19

Diagnostics of Campylobacter jejuni

Answer 19

Gram negative, spiral rod, oxidase positive, catalase positive (microaerophilic)

Question 20

Source of Campylobacter jejuni

Answer 20

uncooked meat (esp. chicken - part of chicken gut flora –> contaminates more than 50% of the carcass)

Question 21

The mortality rate of Campylobacter jejuni infections

Answer 21

1 in 5,000-10,000

Question 22

route of transmission of Campylobacter jejuni

Answer 22

food-borne

Question 23

risk factors for Campylobacter jejuni infections

Answer 23

uncooked meat, children and immunocompromised more susceptible

Question 24

area of colonisation of Campylobacter jejuni

Answer 24

intestines

Question 25

virulence factors of Campylobacter jejuni

Answer 25

flagella, OM (outer membrane) adhesins, pili - for colonisation LPS (lipopolysaccharide) - for immune evasion and inflammation CLT (cholera-like toxin) increases water secretion, CDT (cytolethal distending toxin) leads to cell death - toxins for cell damage

Question 26

is Campylobacter jejuni more of a problem in developing, developed countries or both?

Answer 26

Developed countries due to poor cooking of meat

Question 27

progression of symptoms due to Campylobacter jejuni infection

Answer 27

diarrhoea (bloody), abdominal cramps, fever, bacteremia (neonates and immunocompromised adults), 3-21day duration, 2-11days incubation (infection --> symptomatic)

Question 28

Sequellae (complications after infection) of Campylobacter jejuni

Answer 28

autoimmune sequellae: cross-reacting antibodies, Guillain-Barre syndrome (1 in 1000, myelin sheath affected), Reactive arthritis (1 in 100)

Question 29

Sample tested for identification of Campylobacter jejuni presence

Answer 29

stool

Question 30

Culturing conditions and results of Campylobacter jejuni

Answer 30

Blood agar, 5% O2, 10% CO2, 42degree, result = appearance of water-like droplet colonies after 24h

Question 31

treatment options for Campylobacter jejuni

Answer 31

fluid and electrolyte replacement, pain relief, teach good hygiene - antibiotics recommended if severe, prolonged, if risk/actual spread to blood (bacteremia), or if immunocompromised. antibiotics reduce the severity and duration but affect commensal gut flora too - macrolides (azithromycin, erythromycin) increase bacterial resistance

Question 32

preventative options for Campylobacter jejuni

Answer 32

anti-diarrhoeal drugs: not recommended as they stop flow in the G.I. tract --> concentrate toxins/pathogens in the G.I. tract --> increase contact time with intestinal mucosa - okay for watery diarrhoeal control and with antimicrobial therapy food hygiene: cook food thoroughly, reheat thoroughly, clean utensils, store correctly (refrigerate)