GI 9 infection Flashcards
What are the different types of anaerobes?
Obligate and facultative - Obligate die in the presence of oxygen. Facultative prefer oxygen but can live without it e.g.. many gram-neg enteric bacteria such as E. Coli and gram-pos skin dwellers such as Staphylococcus
Where are the anaerobic zones in the GIT?
Parts of the bout - on the tongue deep in tast buds, fluid films including biofilm between teeth, gingival crevice areas and in people with peridontal disease they live in peridontal pockets
Small bowel
Colon
How were mitochondria developed in evolution?
At some stage an aerobic bacterium was taken into an anaerobic bacterium and formed an organelle which later became a mitochondrium
What do human colonic bacteria do?
Synthesize and excrete vitamins that are absorbed by host. Vit K, B12, thiamine and many other Bs.
Prevent colonisation by pathogens
kill non-indignous bacteria
Stimulate development of MALT (in caecum and Peyer’s patches)
Stimulate production of natural antibodies
What problems do ‘germ-free’ animals develop?
Vitamin deficiencies, esp K and B12
Increased susceptibility to infectious disease
Poorly developed immune system, esp in GIT
Lack of natural antibody or natural immunity to bacterial infection
What are the 2 common endospores?
Bacilus anthrax
Clostridium tetani
How do E coli stick to the bladder wall?
Using pili
What are the common anaerobes in the mouth?
Streptococci staphylococci candida lactobacius enterococcus 700 species therefore human bite can be fatal
WHat is Noma/cancrum oris?
Mouth bacteria can cause tissue destruction if individual is malnourished, dehydrated, immunocompromised or systemically unwell
What microorganism causes oral thrush?
Candida albicans
What are the risk factors for oral thrush?
Newborns Diabetes Antibiotics Inhaled steroids Immune deficiency
What is the treatment for oral thrush?
Amphotericin lozenges
Nystatin suspension
What causes dental caries/gingivitis?
The teeth are colonised by the mouth bacteria plus Strptococcus mutans
What usually causes Ludwig’s angina?
Usually strptococcal
What microorganism usually causes parotitis?
Staph aureus
What are the 2 common bacteria in the nose?
Staphylococcus
Streptococcus
(many others)
What are teh 3 sites for MRSA screening swabs?
Nos, throat and perineum
What microorganisms are always in the throat?
Strep viridans
Staphylococci
Neisseria meningitidis
WHat other microorganisms are common in the throat?
Strp pyogenes Strep pneumoniae Haemophilus influenzea Lactobacilli Corynebacterium diptheria Candida albicans
What is the significance Strep viridans?
Non-pathogenic throat commensal
During procedures such as teeth brushing, dental procedures and general anaesthesia, may enter blood stream
May stick to prostheses such as heart valves, vascular grafts, orthopardic implants and cause infection. Prostheses don’t have the anti-bacterial sticking armour that cells have
What is the difference between bactereamia and septicaemia?
Bacteraemia - the bacteria are rapidly cleared from the bloodstream (by liver/spleen macrophages). No symptoms produced
Seticaemia - bacteria are not cleared, multiply in the blood stream. Sepsis symptoms develop
What microorganisms commonly cause tonsillitis?
70% viral - andenovirus, rhinovirus, Epstein-barr
30% bacterial mainly Strp pyogenes (Beta-haemolytic)
What is quinsy?
Complication of tonsillitis. Collection of pus develops between the back of one of your tonsils and the wall of your throat
What is oesophageal candidiasis?
Opportunistic infection of the oesophagus by candida albicans. Usually in immunocompromised patients
WHat % of people infected with h pylori develop gastric/duodenal ulcers?
10-20%
What bacteria are always present in the colon?
Bacteroides fragilis, bacteroides oralis, bacteroides melaninogeicus (95-99%)
E Coli
Enterococcus faecalis
What are the other common colonic bacilli?
-ve: Pseudomonas Proteus Klebsiella Salmonella Shigella Vibrio cholera Campylobacter \+ve: Lactobacillus
What is ‘dirty surgery’?
Operation on the gut. High risk of wound infection
What is wound dehiscence?
Surgical complication in which wound opens along surgical sutures
What types of organisms for prophylactic antibiotics need to cover?
Anaerobes
Gram-negative bacilli and gram-positive cocci
What is usually used to treat surgical wound infection (prophylactically)?
Metroniadazole kills anaerobes. So one regimen is metroniadazole plus a broad spectrum sntibiotic such as gentamicin or a cephalosporin
Alternatively, co-amoxiclav
What type of antibiotic is Augmentin?
Penicillin
What is the mortality rate of faecal peritonitis?
50% even in fit young people
What colonic bacteria may be present on perineal skin?
Bacteroides - cannot survive oxygen
E coli - can survive
Enterococcus faecalis - can survive
Lactobacillus - can survive
What is Lactobacillus?
Gram + bacillus. Normal vaginal commensal. Converts glycogen to lactic acid. Acid environment prevents other bacteria and candida albicans growing
What broadspectrum antibiotic treatment kills lactobacilli?
Lactobacillus acidophilus
Leads to vaginal thrush
What bacteria are usually present in the colon?
Bacteroides fragilis, Bacteroides oralis, Bacteroides melaninogenicus (95-99%)
E coli
Enterococcus faecalis
What are the 3 types of Clostridia and what do they cause?
Tetani - drumstick appearance due to presence of endospores. Causes tetanus
Difficile - Pseudomembranous colitis
Perfringens - Gas/wet gangrene
What is risks sardonicus?
Lock jaw/abnormal sustained spasming of the facial muscles producing a characteristic smile.
What is opisthotonus?
Severe hyperflexion - “bridging” or “arching”
Explain the mechanism by which Clostridium perfringens causes gas/wet gangrene.
Anaerobic digestion of glucose leads to ethanol + CO2 (fluid plus gas) therefore wet or gas gangrene.
