15) Microbiology of GI Tract Flashcards by Oliver Blake

What are obligate aerobes?

Give an example

Must have oxygen to survive e.g Pseudomonas and Mycobacterium TB

How well did you know this?

Not at all

Perfectly

What are obligate anaerobes?

Give an example

Die in the presence of oxygen e.g. Bacteroides fragilis, clostridial organisms

How well did you know this?

Not at all

Perfectly

What are facultative anaerobes?

Give an example

Prefer oxygen but can live without it e.g. many gram-negative enteric bacteria such as E. Coli and gram-positive skin-dwellers such as Staphylococcus

How well did you know this?

Not at all

Perfectly

What can clostridial organisms do to survive in oxygen?

Produce spores

How well did you know this?

Not at all

Perfectly

What are the anaerobic zones of the GIT?

Parts of mouth - deep in taste buds, between teeth, gingival crevice areas
Small bowel
Colon

How well did you know this?

Not at all

Perfectly

Why are human colonic bacteria important?

Synthesize and excrete vitamins that are absorbed by host e.g vit K, B12 and thiamine
Prevent colonisation by pathogens
Kill non-indigenous bacteria
Stimulate development of GALT (caecum and Peyer’s patches)
Stimulate production of natural antibodies

How well did you know this?

Not at all

Perfectly

What are some features of bacteria that can allow them to survive and infect the GIT?

Endospores e.g. bacillus anthrax, clostridum tetani
Pili - adhere to epithelia
Biofilm

How well did you know this?

Not at all

Perfectly

Why are biofilms on a prosthetic surface particularly dangerous?

No bloody supply close so difficult to get drugs to surface

How well did you know this?

Not at all

Perfectly

What shape are the endospores of C. tetani?

Terminal drumstick

How well did you know this?

Not at all

Perfectly

Give some examples of gram positive aerobic cocci:

Staphylococci, streptococci and enterococci

How well did you know this?

Not at all

Perfectly

Give some examples of gram negative aerobic cocci:

Neisseria meningitidis and gonorrhoeae

How well did you know this?

Not at all

Perfectly

Give some examples of gram positive aerobic bacilli:

Corynebacterium (diphtheria)
Bacillus (anthrax)
Lactobacillus
Mycobacterium TB

How well did you know this?

Not at all

Perfectly

Give some examples of gram positive anaerobic bacilli:

Clostridia (tetani, perfringens, difficile)

How well did you know this?

Not at all

Perfectly

Give some examples of gram negative enteric bacilli:

colon normal flora

E.coli, pseudomonas, klebsiella, salmonella, shigella, camplylobacter, helicobacter pylori 
Bacteroides fragilis (anaerobic)

How well did you know this?

Not at all

Perfectly

Give some examples of gram negative non-enteric bacilli:

all aerobic

H. influenza, bordetella pertussis (whooping cough), brucella

How well did you know this?

Not at all

Perfectly

What are the majority of mouth bacteria?

Anaerobes

How well did you know this?

Not at all

Perfectly

What is noma/cancrum oris?

Bacteria causing tissue destruction, if individual is malnourished, dehydrated or immunocompressed

How well did you know this?

Not at all

Perfectly

What causes oral thrush and how can it be treated?

Candida albicans

Amphotericin lozenges

How well did you know this?

Not at all

Perfectly

What risk factors are there for oral thrush?

Newborns (immune system not developed)
Diabetes 
Antibiotics
Steroids
Immune deficiency

How well did you know this?

Not at all

Perfectly

What is dental caries and what organism causes it?

Teeth colonised by mouth bacteria and Strep. mutans

Causes cavities and teeth to break down

How well did you know this?

Not at all

Perfectly

What bacteria causes parotitis?

S. aureus

What is Ludwig’s angina and what causes it?

Potentially life-threatening cellulitis or connective tissue infection of the floor of the mouth
Streptococci

What are the three swab sites for MRSA screening?

Nose, throat and perineum

What are the main bacteria found in the nose?

Staphylococcus and streptococcus

What are some of the main bacteria found in the throat?

Strep viridans Strep pyogenes Staphylococci Neisseria meningitidis

When can Strep. viridans become a problem?

Dental procedures and teeth brushing where it can enter blood stream and stick to prosthetic surfaces

What percentage of tonsillitis is caused by viruses?

70% - adenovirus and rhinovirus

Which bacteria can cause tonsillitis?

Strep. pyogenes

What is quinsy?

Abscess between tonsil and wall of throat making eating and breathing hard

What are the main bacteria of the colon?

Anaerobes, particularly bacteroides and clostridial species, E. coli and enterococcus faecalis

Why is there a high risk of infection in gut surgery?

Abnormal numbers of bacteria

What prophylactic antibiotics can be given to reduce wound infections?

Metroniadazole and broad spectrum antibiotic (gentamicin or cephalosporin) Co-amoxiclav

What is faecal peritonitis?

Faeces in peritoneal cavity, bacteria can enter blood | High mortality

What is a perianal abscess?

Glands in anal canal infected causing abscess around anus

What is an example of a normal vaginal commensal?

Lactobacillus

How does lactobacillus stop other micro-organisms from growing?

Converts glycogen into lactic acid, providing acidic environment

What happens if antibiotics kills lactobacillus?

Vaginal thrush

What organism is the most common cause of UTIs? | What is the next most common?

E. coli | Enterococcus faecalis

What would you be looking for on a MSU gram stain?

Gram neg bacilli (E. coli) | Gram pos cocci (Enterococci)

What is bacteraemia?

Bacteria rapidly cleared from bloodstream by liver/spleen macrophages, no symptoms

What is septicaemia?

Bacteria aren't cleared and multiply in bloodstream

What does clostridium tetani cause?

Tetanus

What does clostridium dificile cause?

Pseudomembranous colitis

What does clostridium perfringes cause?

Gas/wet gangrene

What causes gastroenteritis?

Consumption of contaminated food or drink

What organisms can cause gastroenteritis?

Salmonella, campylobacter, listeria

What are the symptoms of gastroenteritis?

Vomiting and diarrhoea

What cause cholera and what are the symptoms?

Vibrio cholera leading mass movement of water and salt into lumen by secretion Rice water diarrhoea and dehydration

What can helminth infestations cause?

Malabsorption

What can protozoal infections cause?

Giardia and cryptosporidium cause gastroenteritis

What cause traveller's diarrhoea?

E. coli

What is the pathogenesis of traveller diarrhoea?

Heat stable or labile toxins released by E. coli resulting in watery diarrhoea Usually self limiting