GI Session 9 Flashcards
What are obligate anaerobes?
Microbes that will die in the presence of oxygen e.g. Bacteroides fragilis, clostridia
What do clostridia have that can enable them to survive in oxygen containing environments?
They can form spores
What are facultative anaerobes?
Prefer oxygen but can live without it e.g. G-ve enteric bacteria like E.coli and G+ve skin dwellers like staph
Where are the anaerobic zones of the GI tract?
Deep in taste buds
Biofilm between teeth and gingival crevice areas
Small bowel
Colon
Where do anaerobic bacteria live in pts with periodontal disease?
Periodontal pockets
Why are human colonic bacteria necessary?
Synthesise and secrete vitamins e.g. K, B vitamins, thiamine
Prevent colonisation by pathogens
Kill non-indigenous bacteria
Stimulate development of MALT in caecum and Peyer’s patches
Stimulate production of natural antibodies
What defence mechanisms do bacteria have against the GI tract?
Endospores
Bacterial pili and slime for adhesion
Why is bacterial slime particularly effective at a prosthetic surface?
No blood supply so Abx cannot be delivered to lowest layers of film
What are obligate aerobes?
Microbes that must have oxygen e.g. Pseudomonas, M.TB
What microbes are found in the mouth?
Anaerobes: Streptococci Staphylococci Candida Lactobacillus Enterococcus
When can mouth flora cause tissue destruction?
If an individual is malnourished, dehydrated, immunocompromised or systemically unwell
What diseases can result from imbalance of mouth flora?
Noma/cancrum oris
Oral thrush
Dental caries
Gingivitis
What commensals are found in the nose?
Staph
Strep
Lots more
Where in the body is good for MRSA screening?
Nose
Throat
Perineum
What are the throat commensals?
Strep viridans Strep pyogenes Strep pneumoniae Staph Neisseria meningitidis H.influenzae Lactobacillus
Which spthroat commensals are universally found in the population?
Strep viridans
Staph
Neisseria meningitidis
How can strep throat lead to asphyxiation?
Lymph node infection –> cellulitis –> Ludwig’s angina –> compressed larynx
What happens after brushing your teeth duets thelresende of strep viridans?
Temporary bacteraemia
Describe the aetiology of tonsillitis.
70% viral - adenovirus, rhinovirus, EBV
30% bacterial - strep pyogenes
What is quinsy?
When an abscess develops on the tonsils –> stridor and deviated uvula
What percentage of the world’s population are infected with H.pylori in the stomach?
50%
What are the colon commensals?
Bacteroides fragilis/oralis/melaninogenicus E.coli Enterococcus faecalis Pseudomonas Proteus Klebsiella Salmonella Shigella Vibrio cholera Campylobacter Lactobacillus Clostridial sp.
Why is all gut surgery ‘dirty surgery’?
Because the gut is only ever operated on when the bacterial content is abnormal
What is the possible consequence of all gut surgery being ‘dirty’?
Wound infection, dehiscence
What must prophylactic Abx used in GI surgery be active against?
Anaerobes
G+ve
G-ve
What are the universal colon commensals?
Bacteroides fragilis/oralis/melaninogenicus
E.coli
Enterococcus faecalis
What is faecal peritonitis?
Faeces in peritoneum which has no defence mechanism –> 50% mortality
What is the pathogenesis of Perianal abscess formation?
Blockage of anal gland –> passage of faeces impaired –> abscess formation
Why must bacteroides remain in the rectum?
Cannot survive in oxygen
What causes 75% of UTI?
E.coli
What is the second commonest cause of UTI?
Enterococcus faecalis
What is lactobacillus?
Normal vaginal commensal which converts glycogen–> lactic acid to prevent other bacteria and Candida albicans from growing
How do broad spectrum Abx lead to development of vaginal thrush?
Kill lactobacillus so Candida albicans can grow
Why do pts with lower abdominal pain need urgent MSU gram stain?
To determine whether they have a UTI of appendicitis
What does each possible outcome of the MSU gram stain of a pt with lower abdominal pain indicate?
G-ve bacilli –> E.coli –> UTI or appendicitis
G+ve bacilli –> lactobacillus –> contamination from vagina
G-ve cocci –> gonococcus –> contamination from urethritis
G+ve cocci –> enterococcus –> UTI or appendicitis
What causative agent is characterised by green pus formation?
Pseudomonas aeruginosa
What environment does pseudomonas aeruginosa favour?
Moist or fluid
What do all clostridia species produce?
Spores
What are the consequences of clostridia tetani infection?
Lock jaw –> risus sardonicus
Opisthotonos
Resp muscle spasm (larynx) –> death
What results from clostridia difficile infection?
Pseudomembranous colitis
What results from clostridia perfringens infection?
Gas or wet gangrene due to anaerobic digestion of glucose –> ethanol and carbon dioxide
Why does gas gangrene indicate immediate amputation?
Very dangerous cardiac endotoxins are released simultaneously
