Week 4/5 - B - Gastroenteritis(Bacillus/Staph/C.Perfringes/Shigella/E.Coli(H.U.S)/Campylobacter/Salmonella/Listeria) Typhoid/cholera

Question 1

Gastroenteritis (aka infectious diarrhoea) = diarrhoea (+/- vomiting) due to enteric infection with viruses, bacteria or parasites Lots of different causes * What is diarrhoea defined as? * What is dysentry defined as? * What is persistent diarrhoea? * What is traveller’s diarrhoea defined as?

Answer 1

* Diarrhoea is defined as >/= 3 unformed / water stools within 24 hours * Dysentry is defined as infectious gastroenteritis with bloody diarrhoea * Persistent diarrhoea is defined as actuely starting diarrhoea lasting >14 days * Traveller’s diarrhoea is defined as diarrhoea starting during, or shortly after, foreign travel

Question 2

What are the additional symptoms of gastroenteritis? What are the different categories of the bristol stool chart?

Answer 2

Gastroenteritis - Diarrhoea, Vomiting, Abdominal cramps, Loss of appetite, Fever, Nausea Bristol stool chart Type 1 - small hard lumps Type 2 - sausage shaped and lumpy Type 3 - sausage shaped and cracked Type 4 - smooth - normal Type 5 - soft blobs Type 6 -fluffy pieces, mushy Type 7 - watery, no solid pieces

Question 3

What are examples of dysentry causing infections?

Answer 3

Shigella E.coli - certain toxins Campylobacter Salmonella

Question 4

What are different risk factors for bacteria to cause gastroenteritis? (asking about food preparation/storage here)

Answer 4

Cross contamination work surfaces/utensils Undercooking (insufficient heat to kill of pathogens), linked to inadequate defrosting of frozen food Improper storage of food (inadequate refrigeration) Poor reheating of food

Question 5

What can infections produce that can survive adverse conditions such as normal alcohol based disinfectants?

Answer 5

Different infections can produce spores that can survive adverse conditions (eg spores produced by C.difficile after antibiotics alter the normal gut flora)

Question 6

Incubation periods can give a clue to the type of causative infection Which infections have an incubation time (ie how long after eating food / contaminated water do symptoms occur) * 1-6 hours * 12-48 hours * 2-14 days

Answer 6

SHORT * Bacillus cerus and staph aureus infections of the GI tract typically have a 1-6 hour incubation period MEDIUM * Shigella, salmonella and clostridium perfringens infections of the GI tract typically have a 12-48 hour incubation period LONG * Campylobacter and E.coli 0157 typically have a 2-14 days incubation period

Question 7

Which bacterial infections are associated with preformed toxins? How does each present? (CLUE - it is the three gram positive gastroenteritis organisms The rest are all basically gram negative bacilli)

Answer 7

Staphyloccous aruerus infections - severe vomiting within 6 hours Bacillus cereus infections - vomiting within 6 hours, diarrhoea after 6 hours Clostridium perfringens infections - diarrhoea and vomiting within 12-48 hours

Question 8

What type of bacteria is bacillus cerus? What is the vehicle of transmission? How are toxins produced with this bacterial infection?

Answer 8

Bacillus cereus is a gram positive aerobic bacilli It is associated with contaminated inadequately refrigerated reheated rice Spores from this bacteria survive cooking and turn into vegetative organisms that produce toxins that are absorbed in the gut

Question 9

What type of bacteria is staph aureus? What is the vehicle of transmission? How are toxins produced with this bacterial infection?

Answer 9

Staphlococcus aureus is a gram positive cocci It is associated with creams and unpasterusised milk/cheese Some strains of staph aueus can produce an enterotoxin (an exotoxin that affects the gut) These toxins are absorbed quickly in the gut and directly act on the vagus nerve and vomiting centre to cause vomiting within 1-2 hours

Question 10

What type of bacteria clostridium perfringens? What is the vehicle of transmission? How are toxins produced?

Answer 10

Clostridium perfringes is a gram positive anaerobic bacillus It is part of the normal gut flora It is associated with inadequately refrigerated reheated meat / gravy Spores can survive cooking, then turn into vegetative organisms, some strains which can produce an enterotoxin

Question 11

Shigella What is the most common type of Shigella bacteria? Which type can cause deadly epidemics in low income countries?

Answer 11

Shigella sonei is the most benign and the only species of shigella seen in the UK There are outbreaks every few years Shigella dysenteriae can cause deadly epidemics in low income countries

Question 12

What is the incubation period of shigella? What is the presentation? What age group is it often spread amonst?

Answer 12

Shigella has an incubation period of 12-48 hours It presents with watery or bloody diarrhoea, pain, tenesmus and often fever It usually occurs amongst vulnerable young children

Question 13

What is the transmission of shigella? How does it affect the patients gut? - will it invade into blood? How is it managed?

Answer 13

Transmission is human to human spread Invades intestinal mucosa causing severe inflammation. Will not invade further than mucosal layer. (NEVER SEEN IN BLOOD CULTURES) Shigella sonei is a self-limiting infection (ciprfloxacin can be used from other species such as Shigella dysenteriae)

Question 14

Escherichia coli 0157 There are different serotypes of E.coli infections One serotype is E.coli O157:H7 What does the O stand for? What does the H stand for?

Answer 14

O157 refers to the O (somatic) antigen on the surface of the organism - surface antigen present (ie it is a specific serotype of the usually benign E.coli) The H refers to flagellar antigen

Question 15

What do different serotypes of E.coli 0157 eg E.coli O157:H7, produce that gives its name, STEC?

Answer 15

E.coli 0157 produces verotoxins which are SHiga-like due to the similarity with Shigella dysenteriae Therefore it is given the name Shiga-toxin producing E.coli (STEC) * (used to be known as vertoxin producing E.coli - VTEC) * (aka enterohaemorrhagic E.coli - EHEC)

Question 16

How does the shiga toxin affect the patients body? (seen in shigella dysenteria or verotoxins which are shiga like seen in eg E.coli O157:H7)

Answer 16

* The toxins bind to absorptive enterocytes on the limunal surface of the large intestine * They then enter the cell and irreversibly inhibit protein synthesis causing death of enterocytes * They then enter the bloodstream via damaged epithelium and cause the death of vascular endothelial cells leading to platelet aggregation and fibrin clots This can lead to a microangiopathy (disease of the capillaries) as the toxins are carried to the kidneys

Question 17

What is the syndrome caused in severe E.coli O157 infections? What are the triad of symptoms in this condition?

Answer 17

E.coli O157 can cause Haemolytic uraemic syndrome Haemolytic uraemic syndrome is generally seen in young children and produces a triad of: acute kidney injury (due to thombosis because of platelet aggregation/fibrin clot)- increased blood urea microangiopathic haemolytic anaemia thrombocytopenia

Question 18

How does haemolytic uraemic syndrome present?

Answer 18

Presents with abdominal pain, bloody diarrhoea, fever, pallor, petechia (haemorrhages in the skin), oliguria (due to the acute kidney injury) Usually in children

Question 19

Which age group is haemolytic uraemic syndrome commonly seen in?

Answer 19

Haemolyic uraemic syndrome is seen in children <5 years and elderly patients It is the most common cause of renal failure in children <5 years in the UK

Question 20

What is the presentation of E.coli O157? What is the vehicle of transmission?

Answer 20

Presentation is bloody diarrhoea and abdominal pain Vehicle is from beef (part of normal gut flora in cattle) - beef becomes contaminated at slaughter so greater risk from minced meat and hamburgers

Question 21

What is the treatment of an E.coli infection? Why are antibiotics not used?

Answer 21

Treatment is supportive only Antibiotics contraindicated as they can increase release of the toxin

Question 22

Campylobacter Campylobacter infection is the most common cause of bacterial GI infection What is the incubation of the disease? What is the vehicle of infection? How does it affect the gut?

Answer 22

Campylobacter has an incubation period of 1-14 days The vehicle of infection is undercooked meat (poultry), water and unpasteurised milk It causes inflammation of the colon and rectum It can invade the colon and occasionally get into the bloodstream

Question 23

What is the presentation of cambylobactera? What types of cambylobacter is the common human pathogenic strain? What is the management?

Answer 23

Campylobacter normally presents with bloody dirrhoea, pain, fever and headache within 2 weeks of infection Cambylobacter jejuni is the common strain of the gram negative bacilli Management is self-limting - supportive care

Question 24

SALMONELLA What is the agreed species name for all food poisoning salmonella? ie non-typhoidal salmonella What is the incubation period? WHat is the presentation?

Answer 24

Agreed name for non-typhoidal salmonella is salmonella entericus It has an incubation period of 12-48 hours Presents with diarrhoea and vomiting, blood in stool and fever

Question 25

What is the vehicle for salmonella enterica infections? How does it affect the gut?

Answer 25

The vehicle of infection is farm animals especially undercooked poultry (same as campylobacter however incubation period is different), also undercooked eggs It causes inflammation of the ileum and colon - multiplyin in the gut and causing mucosal damage (decreases fluid absorption, increases fluid excretion) It can invade the gut and enter the bloodstream

Question 26

What is the management of a salmonella infection? If either salmonella or campylobacter result in systemic illness (flu like symptoms –> fevers, rigors, flu), what can be given?

Answer 26

Usually self limting Can give ciprofloxacin if systemic illness symptoms appear

Question 27

Listeria monocytogenes Listeria monocytogenase is associated with which foods? Which groups of patients can there be severe infections in?

Answer 27

Listeria monocytogenes is associated with unpasteruised milk products, refrigerated pate, soft cheeses, cold meat Infections are usually mild - fever, muscle aches, diarrhoea Can be severe in immunosuppressed and pregnant

Question 28

How is listeria diagnosed? What is the treatment?

Answer 28

Listeria is best diagnosed from a sterile surface Treatment is with amoxicillin +/- gentamicin

Question 29

Which gastroenteritis infections would you test for in stool cultures? Which would you use stool toxins to test for?

Answer 29

Stool cultures * Shigella * Campylobacter * Salmonella * E.coli * Cholera Stool toxins * E.coli O157 - shiga toxin (verotoxin) * C.difficile - if glutamate dehydrogenase positive, test for toxin A and B

Question 30

Which gastroenteritis conditons would you use viral PCR to test for?

Answer 30

Rotavirus * Mainly in children * Incubation about 2 days, lasts about a week Norovirus (winter vomiting although basically annual now) * Any age * Incubation less than a day, lasts 2/3 days

Question 31

What is the most common cause of Traveller’s diarrhoea? What is the most common cause of persistent traveller’s diarrhoea? How does it present?

Answer 31

Most common cause of travellers dirrhoea - enterotoxigenic E.coli Presents with watery diarrhoea and abdominal cramps Most common cause of persistent traveller’s diarrhoea - giardia lambia (lasting >14 days) - usually from contaminated water Presents with diarrhoea, flatulence, bloating, malabsorption

Question 32

How is traveller’s diarrhoea typically treated? How is Giardia lambia diagnosed and treated?

Answer 32

Travellers diarrhoea - typically self limiting lasting less than one week Giardia lambia - Diagnose with three separate stool samples for ova and parasites Treat with week of metronidazole (or single dose tinidazole)

Question 33

Enteric fever - what causes this? It is most common in those returning from indian subcontinent or SE asia

Answer 33

Enteric fever aka typhoid or paratyphoid fever Typhoid and paratyphoid fever are caused by Salmonella typhi and Salmonella paratyphi respectively.

Question 34

What is the vehicle of transmission in enteric fever? How does enteric fever initially present?

Answer 34

Enteric fever is usually transmitted faecal oral route from contaminated water/food Incubation period is about 10-20 days Bacteria invade the intestinal mucosa and then dissemination occurs without a primary diarrhoeal response High fever, headache , arthralgia, rash

Question 35

What is the rash that appears in enteric fever known as? When does diarrhoea appear as a symptom?

Answer 35

Rose spots are red macules 2-4 millimeters in diameter occurring in patients with enteric fever on the patient’s trunk Diarrhoea is uncommon and usually causes constipation

Question 36

What is the treatment of enteric fever?

Answer 36

IV ceftriaxone or Azithromycin tend to be the antibiotics of choice

Question 37

What bacterium causes cholera? When are these infections common? What is the symptoms?

Answer 37

Cholera is caused by vibrio cholerae (another gram negative bacillus) Infections are common in disaster or war situations Symptoms are the classic Rice water stools, vomiting , dehydration

Question 38

How is cholera spread? What is the treatment of cholera?

Answer 38

Cholera is spread via faecally contaminated water/poor sanitation FLUID AND ELECTROLYTE REPLACEMENT = ESSENTIAL (oral rehydration solution) Antibiotics not recommended unless severe

Question 39

What are the two gastroenteritis that are rarely contagious? Antibiotic treatment is not usually needed for people with gastroenteritis symptoms, as infection is usually self-limiting. If symptoms are severe (high fever, bloody and/or high-output diarrhoea) or the person is immunocompromised or persisitent, what can be given (for eg campylobacter, salmonella, shigella)?

Answer 39

Campylobacter and E.coli 0157 are rarely spread person to person Usually a macrolide eg clarithromycin or a fluoroquinolone eg cirpfloxacin if antibiotics are needed