Session 9 - Gastrointestinal Tract Flashcards
How many bacteria are there in the GI tract?
• 10^14
Give five functions of normal gut flora
- Synthesise and excrete vitamins
- Prevent colonisation by pathogens
- Kill non-indigenous bacteria
- Stimulate the development of GALT
- Stimulate production of natural antibodies
What vitamins are synthesised and secreted by gut bacteria?
- K
- B12
- Thiamine
Riboflavin
How do gut bacteria prevent colonisation from foreign bacteria?
- Space
* Bacteriosides
Describe the broad categorisation of bacteria present in the GI tract
• Cocci/Bacilli
• Gram Positive/Gram Negative
• Aerobic/Anaerobic (Obligate or facultative)
• Some bacteria form protective endospores
○ Bacillus Anthrax
○ Clostridium Tetani
• Bacteria can stick to surfaces using pili and/or slime
What is an obligate aeorobe? Give 2x examples
- Bacteria must have oxygen
- Pseudomonas
- Mycobacterium TB
What is an obligate anaerobe? 2x examples
- Die in the presence of oxygen
- Bacteroides fragillis
Colstridia
What happens to clostridia in the presence of O2?
• Forms resilient spores
What is a falcultative anaerobes? 2x examples
- Prefer oxygen but can live without it
- Gram -‘ve E.coli
- Gram +’ve Staphylococcus
Give three anaerobic zones in the GI tract
• Parts of the mouth
○ Tounge, deep in taste buds, biofilm between teeth
• Small bowel
Colon
Why can the bacteria of the mouth cause nasty/fatal infections?
• Anaerobic
List five types of bacteria found in the mouth
- Streptococci
- Staphlcocci
- Candida
- Lactobacillus
- Enterococcus
Give a streptococcal bacterium of the mouth and the disease it causes
- Streptococcus mutants
* Dental caries/Gingivitie
Give a stayphylococcal bacterium of the mouth and the disease it causes
- Staphylococcus aureus
* Parotitis
Give a candida infection of the mouth
- Candida albicans
* Oral thrush
What does oral bacteria cause in a malnourished, dehydrated or immunosupressed patient?
• Noma, tissue destruction of the mouth
What are dental caries?
- Tooth decay
* Acid breaks down enamel of teeth
What is oral thrush (oral candiasis)?
• Infection of oral cavity by candida albicans
What is Noma?
• Destruction of oral tissue
Give two types of bacteria found in the nose
• Staphylococcus and streptococcus
What is the nose used as a swabbing place for? What are the other two places used for this swab?
- MRSA screening swabs
* Throat and perineum also used
What bacteria/fungi are found in the throat?
- Strep viridans
- Strep pyogenes
- Strep pnueumonia
- Staphylococci
- Neisseria Meningitidis
- Haemophilus Influenzea
- Lactobacili
- Corynebacterium Diptheriae
- Candida Albicans
What proportion of population is strep viridians found in? Why is it often found in blood?
- 100% of people
* During teeth brushing, dental procedures and general anaethesia
What does strep pyogenes cause?
• Tonsilitis (30%, 70% is viral)
What does strep pneumoniae cause?
Community acquired pneumonia (30%)
What does haemophilus influenzae cause?
• Community acquired pneumonia
What do lactobacili do?
• Make vagina acidic so candida albicans can’t grow
What does corynebacterium do?
Causes diptheria
What does candida albicans do?
• Causes oral/vaginal thrush
What are two causes of tonsilitis?
- Viral - 70%
* Bacterial - 30%
Give three viruses which cause tonsilitis
- Adenovirus
- Rhinovirus
- Epstein-barr virus
Give a bacterium which causes tonsilitis
Strep pyogenes
What is the main bcateria found in the stomach?
• Helicobacteria pyloria
○ At least 50% of world pop infected
○ 10-20% develop gastroduodenal ulcers
Associated with 90% of duodenal and 70% of gastric ulcers
Give the two most common types of bacteria in colon
• Anaerobes
○ Bacteroides
○ Clostridial
Give five bacteria always present in colon
- Bacteroides fragillis
- Bacteroides oralis
- Bacteroides melaninogenicus
- E. Coli – Most common cause of UTI
- Enterococcus faecalis – Second most common cause of UTI
Give 7 bacteria not previously mentioned sometimes found in colon (gram -‘ve)
- Pseudomonas
- Proteus
- Klebsiella
- Salmonella
- Shigella
- Vibrio cholera
- Campylobacter
Despite it being sterile, why are surgical procedures on SI considered dirty?
• In infection, bacteria will be present and cause a high risk of wound infection
How is surgical wound infection reduced in GI surgery?
• Prophylactic antibiotics which can cover anaerobes, gram -‘ve and gram +’ve bacilli.
Give an antibiotic which kills anaerobes?
• Metronizasole
Give two broad spectrum antibiotics
- Gentamicin
* Cephalosporin
Give the antibiotics used in antibiotic prophylaxis for GI surgery
- Metronidazole
- Gentamicin
- Cephalosporin
What are two surgical complication of GI surgery?
- Faecal peritonitis
* Perianal abscess
What is faecal peritonitis?
• As a high mortality rate, even in young, fit people, due to the huge numbers of bacteria floating free in the peritoneum
What is a perianal abscess?
• Glands in the anal canal produce mucus for lubrication to aid with passing faeces. Infection of them leads to abscess around the anus - perianal abscess
What is the normal flora of the vagina?
• Lactobacillus (Gram +’ve Bacilli) is a normal vaginal organism
What is lactobacillus?
• Baccilus which converts glycogen into lactic acid, providing an acidic environment to prevent other bacteria and candida albicans from growing
What three gut bacteria are found on the perineal skin?
- E.coli
- Enterococcus faecalis
- Lactobacillus
What is bacterioides fragillus not found on perineal skin?
Obligate anaerobes
Why do the majority of UTI’s occur in women?
• Much shorter distance from the anus to the urethra
What is the most common causative organisms of UTI?
- E.coli
- Enterococcus faecalis
- Thereafter gram -‘ve bacteria (Klebsiella, proteus, pseudomonas)
Name three clostridia bacilli
- Tetani
- Difficile
Perfringens
What does clostridia tetani cause?
Tetanus
What does clostridium difficle cause?
• Pseudomembranous colitis
○ Severe inflammation of the colon
○ Arises after anti-biotic treatment
○ Produces spores which are present in hospital
What does clostridium perfringens cause?
- Gas/Wet gangrene
* Anaerobic digestion of glucose leads to ethanol + CO2, thus wet or gas gangrene
List four types of gastrointestinal infection
- Noro-virus
- Gastroenteritis
- Cholera
- Intestinal parasites
What is norovirus?
• A viral infection which causes a short bout of vomiting and diarrhoea
What is gastroenteritis?
- May follow consumption of food or drink contaminated with organisms or toxins
- Vomiting and diarrhoea common symptoms. Rapid onset.
What are the three most common organisms which cause gastroenteritis?
- Salmonella
- Campylobacter
- Listeria
- Staphylococcus
Clostridium
What organism causes cholera?
• Vibrio cholerae
What occurs in cholerae?
- Vibrio cholerae causes increase in permeability of the ileum, leading to massive movement of water and salt into lumen by active secretion
- Leads to very serious diarrhoea
What does stool in cholera look like?
Cloudy white “rice wate”, as it is made up of intestinal secretions and mucus.
What does cholera cause?
Rapid, severe dehydration
How can cholera be managed?
• Oral rehydration solution
What is the difference between bacteraemia and septicaemia?
- Bacteraemia, bacteria are rapidly cleared from blood stream and no symptoms are produced
- Sepitcaemia, bacteria are not clearing and multiply in the blood stream. Sepsis symtpoms may develop.
discuss the common causes of “travellers diarrhoea”
• Enterotoxinogenic E. Coli is a major cause of travellers diarrhoea in developing countries
Caused by heat stable or labile toxins produced from this serotype, which results in severe cholera like watery diarrhoea
What are 5 causes of inflammatory bowel disease?
- Ulcerative colitis
- Chrohn’s disease
- Diversion Colitis
- Diverticular Colitis
- Radiation, drugs, infectious diseases, ischaemic colitis
