Flashcards in 15) Microbiology of GI Tract Deck (52)
What are obligate aerobes?
Give an example
Must have oxygen to survive e.g Pseudomonas and Mycobacterium TB
What are obligate anaerobes?
Give an example
Die in the presence of oxygen e.g. Bacteroides fragilis, clostridial organisms
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
What can clostridial organisms do to survive in oxygen?
What are the anaerobic zones of the GIT?
Parts of mouth - deep in taste buds, between teeth, gingival crevice areas
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
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
Why are biofilms on a prosthetic surface particularly dangerous?
No bloody supply close so difficult to get drugs to surface
What shape are the endospores of C. tetani?
Give some examples of gram positive aerobic cocci:
Staphylococci, streptococci and enterococci
Give some examples of gram negative aerobic cocci:
Neisseria meningitidis and gonorrhoeae
Give some examples of gram positive aerobic bacilli:
Give some examples of gram positive anaerobic bacilli:
Clostridia (tetani, perfringens, difficile)
Give some examples of gram negative enteric bacilli:
(colon normal flora)
E.coli, pseudomonas, klebsiella, salmonella, shigella, camplylobacter, helicobacter pylori
Bacteroides fragilis (anaerobic)
Give some examples of gram negative non-enteric bacilli:
H. influenza, bordetella pertussis (whooping cough), brucella
What are the majority of mouth bacteria?
What is noma/cancrum oris?
Bacteria causing tissue destruction, if individual is malnourished, dehydrated or immunocompressed
What causes oral thrush and how can it be treated?
What risk factors are there for oral thrush?
Newborns (immune system not developed)
What is dental caries and what organism causes it?
Teeth colonised by mouth bacteria and Strep. mutans
Causes cavities and teeth to break down
What bacteria causes parotitis?
What is Ludwig's angina and what causes it?
Potentially life-threatening cellulitis or connective tissue infection of the floor of the mouth
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?
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?
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)
What is faecal peritonitis?
Faeces in peritoneal cavity, bacteria can enter blood
What is a perianal abscess?
Glands in anal canal infected causing abscess around anus
What is an example of a normal vaginal commensal?
How does lactobacillus stop other micro-organisms from growing?
Converts glycogen into lactic acid, providing acidic environment
What happens if antibiotics kills lactobacillus?
What organism is the most common cause of UTIs?
What is the next most common?
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?
What does clostridium dificile cause?
What does clostridium perfringes cause?
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?
What can protozoal infections cause?
Giardia and cryptosporidium cause gastroenteritis
What cause traveller's diarrhoea?