week 6 Gastroenteritis and intra abdominal infections Flashcards
Are the bacteria of the commensal flora aerobic or anerobic?
Obligate anaerobic bacteria–> can’t survive in the presence of oxygen
The faecal flora ahs been estimated to have a metabolic capactiy equal to what organ?
The liver
What are the beneficial effects of commensal flora of the gut?
Metabolism,
Colonisation resistance Antibody induction
What might have a profound effect on the composition of gut flora?
Diet
Early years exposure –> bottle fed vs breast fed babies
What vitamins are secreted by the bacteria in the gut?
Vitamin K and B12
Everyone has different flora compisiton in there gut due to different exposure. What is the affect of bottle fed and breast fed on the gut flora?
Bottle fed –> adult microflora
Breast fed babies –> bifidobacteria
When does colonisation of the gut begin?
You are born sterile and colonisation begins at birth
what is the second leading cuase of death in children under 5 years old?
Diarrohea
What are the common bacterial causes of gastroenteritis? (8)
Salmonella,
- Shigella, - E coli - Campylobacter - Vibrio cholerae - Clostridium difficile - Staph aureus - Bacillus cereus
What parasitic causes of gastroenteritis?
Entamoeba hist.
- Giardia lamblia - Cryptosporidium
What virus causes gastroenteritis?
Norovirus
- Rotavirus
what are the presenting complaints of gastroenteritis?
Acute onset Vomiting and/or Diarrhoea – frequency, mucous, blood Abdominal pain Systemic effects – fever etc.
what complications can you get with gastroenteritis?
Dehydration Renal failure HUS Toxic megacolon GBS Salmonella
What are the investigations for gastroenteritis?
Bloods – FBC, U&E, CRP, blood cultures
Abdominal Xray – if severe
Stool
Looking for markers of infection –> detecting bodies reponses
What is the difficulty of investigating the cause of gastroenteritis?
There is so many different organisms in the gut that it is difficult from differentiating between the good and bad organisms.
What tests are done on stools in the analysis of the cause of gastroenteritis?
Ova, parasites and cysts ‘OCP’
Microscopy, culture and sensitivity ‘MC&;S’
Clostridium difficile toxin ‘CDT’
Viral PCR
What is the most common cause of gut infection?
Norovirus
What type of virus is norovirus?
Either Norwalk-like virus, SRSV (small round structured virus
Winter-vomiting disease
What are the main symptoms of norovirus?
Diarrhoea and projectile vomiting
How long does norovirus infection last and what is the management/treatment?
Illness last for 24-48hrs.
No specific treatment just allow the the infection to run its course –> lots of water to prevent dehydration
What is the advice given for people who have been infected by norovirus?
Stay away from work to prevent spreading the disease to other people, and practice good hygiene and handwashing to prevent spread to others.
What vacine has been introduce for children to prevent norovirus infection?
Rotavirus vacine
How does the norovirus spread?
Aerosols –> vomiting, feacal/oral route –> particules
What type of disease is cryptosporidosis? What does it contaminate?
Waterborne disease
Contaminated drinking water, swimming pools, water features, natural waters, animal and human contact, other routes
How can cryptosporidum infection harbour in swimming pools?
Oocyst resistance to chlorine based disinfectants
Why is salad bags a source of contaimnation for cryptosporidiosis?
Washing the salads with contaminated water
What are the two modes of action of bacteria causing gastroenteritis?
Enterotoxin –> the production of toxins that cause the disease
Adherance –> the bacteria it self causes the infection
Give example of enterotxin bacteria that cause gastroenteritis? (6)
Vibrio cholerae Escherichia coil Clostridium perfringens Staphylococcus aureus Bacillus cereus Clostridium difficile
Give 4 examples of adherance bacteria that causes gastroenteritis?
Shigella sonnei / flexneri
Escherichia coil
Campylobacter jejuni
Salmonellae
Other than GI disease what other diseases can E.coli cause?
UTI
What is the major source of E.coli 0157?
Cattle
What type of toxin is produce by E.coli 0157?
Shiga toxin virulence
In what percentage of people who have E.coli 0157 will develop haemolytic uraemic syndrome?
10-15%
What is haemolytic uraemic syndrome?
The toxin doesn’t just affect the epithelial cells but also the RBc–>
Toxin causes premature destruction of the red blood cells which then clog the body’s filtering system, the kidneys, causing hemolytic-uremic syndrome (HUS).
How does E.coli cause diarrohea?
Toxin act on epithelial cells and cause massive activation of ion channels.
This causes huge amount of ions to be released from the gut lumen and therefore the lumen becomes really salty –> body tries to fix this but by diliuting the salty liquid causes diarrohea
Is salmonella a enterotoxin or adherance bacteria?
Adherance bacteria
What disease does salmonella cause? (3)
Typhoid –> Can spread outside of the GI tract and
Paratypoid strains stick in the GI tract only
Food poisining
What is the general treatment of gastroenteritis?
Supportive management
Generally avoid antibiotics
May increase duration of salmonella carriage
May worsen E. coli HUS
What are the different strains of salmonella?
S. typhi
S. paratyphi
S. enteritidis
S. typhimurium
When do you give antibiotics to treat gastroenteritis?
in very young & very old
Campylobacter – prolonged or severe symptoms
Invasion (e.g. positive blood cultures)
Why should you not give antibiotics to treat infection caused by bacteria that release toxins?
By killing the bacteria you will cause toxin to be released which will make it even worse
What percentage of patients will get antibiotic associated diarrohoea?
5-30%
What affect does antibiotics have on gut microflora ?
Change in metabolism (change levels of carbohydrates / bile acids) of what is happening in the gut
Overgrowth of pathogenic organisms
What organisms cause antibiotic assoicated diarrohoea?
Clostridium difficile --> accounts fo 10-25% C. perfringens, S, aureas, Candida spp, Klebsiella spp, Salmonella spp
What is the symtpoms of AAD?
Symptoms range from mild diarrhoea to pseudomembranous colitis
- Can lead to Toxic megacolon, perforation, shock
What is the main cause of pseudomembranous colitis?
C.difficile
What strain of C.difficile cause death in the young?
Non-NAP1
What antibiotics pose a high risk of C.difficile infection?
cephalosporins
clindamycin
What antibiotics pose a medium risk of C.difficile infection?
ampicillin/amoxycillin
co-trimoxazole
macrolides
fluoroquinolones*
What antibiotics pose a low risk of C.difficile infection?
aminoglycosides metronidazole anti-pseudomonal penicillins + b- lactamase inhibitor Tetracyclines rifampicin vancomycin
What are the control measures for C.difficile infection?
Early warning system to identify changes in local epidemiology
Reduce risk of transmission
Early isolation/cohorting of patients with diarrhoea
Environmental cleaning, chlorine
Hand hygiene soap & water
Examine/optimise/reduce overall antibiotic use
Limit high risk agents in high risk patients
Feedback CDI & antibiotic data on a regular basis
What is the current treatment of C.difficile infection?
oral metronidazole / oral vancomycin
New treatment –>
NEW – oral fidaxomicin –> V. expensive but good
What is alternative way of treating C.diff rather than giving antibiotics?
Faecal transplant
what is the definition of intra-abdominal infection?
Presence of micro-organim in a normally-sterile site within the abdominal cavity.
Sterile sites
Peritoneal cavity
Hepatobillary trea
Why is gastroenteritis not a example of intra-abdominal infection?
Because the bowel lumen is not a sterile site
What part of the GI tract below the oesophagus is suppose to be sterile?
The stomach and the proximal small intestine.
Due to the production of the bile which inhibits growth.
The distal intestinal flora reflects that of large intestine and is not sterile
What organisms are found in the proximal part of the small intestine?
A few aerobic bacteria and Caninda spp (yeast)
What type of flora is there in the distal part of the small intestine?
Very similar to the large intestine
What does large intestine mainly contain?
95-99% of the large intestine is made up of anaerobic bacteria –> don’t offer encounter in infection
What aerboic baceteria are fonnd in the large intestine?
Enterobacteriaceae (enteric Gram-negative bacilli, coliforms)
Gram-positive cocci (mainly enterococci)
What are the sources of intra-abdominal infection?
Gastrointestinal content
Blood
External
What are the 3 different mechanisms of intra abdominal infection?
Translocation of micro-organisms from inside the lumen of the GI tract to outside the peritoneal cavity.
Translocation of microorganism along a lumen
Translocation of microorganims from extra-intestinal source
What are the different types of translocation across a wall? Give example of each
Perforation–> most common
Perforated appendix, perforated diverticulum, bowel cancer and perforated ulcer.
Loss of integrity –> ischemia due to blood vessel being blocked that leeds to stragulation then hernation and this caues leakage to the peritoneal cavity.
Surgery –> seeding at operation or anastomeses leak.
What are the different types of translocation along a lumen?
Blockage
Cholecystitis, cholangitis, hepatic abscess
Iatrogenic
Instrumentation (e.g. ERCP)
Who are most likely to get a perforated appendix?
Disease mainly of children and young adults
What is the symptom of perforated appendix?
Severe and generalised pain
What can be a consequence of perforated appenix?
Shock
What might perforated appendix form?
Form appendix mass.
Which is Inflamed appendix with adherent covering of omentum and small bowel.
What happens during perforated appendix?
Obstruction of lumen of the appendix. Caused by
1) Lymphoid hyperplasia or faecal obstruction
2) Results in stagnation of luminal contents, bacterial growth and recruitment of inflammatory cells
3) Build up of intraluminal pressure may result in perforation
4) Escape of luminal contents into peritoneal cavity is “peritonitis”
What is the treatment for perforated appendix?
Surgery: appendicectomy
Antibiotics: cefuroxime & metronidazole for 5 days
What is a diverticulum/
Hernation of mucosa/submucosa through muscular layer.
Occurs in the sigmoid and descending colon.
How common is asymptomatic diverticulum and to who’m does it occur in?
50% over 70yrs
What are the complications of diverticulum?
Diverticulitis
Perforation
Pericolic abscess
What complication may be caused by bowel cancer?
Intraperitoneal and/or bloodstream infection is an infrequent complication
What blood stream infections occur in a person with bowel cancer?
Especially associated with Clostridium septicum and Streptococcus gallolyticus (formerly S. bovis) bloodstream infection
What is the thought of the cause of intra-abdominal infection for a person with bowel cancer?
Presumably caused by loss of bowel wall integrity due to abnormal malignant tissue
What symptoms would a bowel cancer patient with intra-abdominal infection present with?
May follow symptoms consistent with bowel malignancy
e.g. weight loss, alteration of bowel habit, blood in stool etc
How could ischaemia cause intra-abdominal infection?
Interruption of intestinal blood supply:
Strangulation
Arterial occlusion
Post-operative ( aneurysm repair)
Gut wall loses structural integrity
Allows translocation of the luminal content
What are the different causes of post operative infection?
Seeding at operation
Anastomotic leak
Acute infection
Intraperitoneal abscess
How is seeding in operation reduced?
Bowel preparationa nd prophylatic antibiotics
What is cholecystitis?
Inflammation of the gallbladder wall –> chemical inflammation
Is bacterial infection cause of cholecystitis?
Bacterial infection may be cause or result of cholecystitis
Cultures positive in c. 50-75% of cases
What is cholecystitis assoicated with?
Associated with obstruction of the cystic duct
What is the cause of obstruction of the cystic duct in cholecystitis?
Gallstones (90%)
Other causes
Malignancy, surgery, parasitic worms
Very occasionally no obstruction
What is the presentation of cholecystitis?
Fever, right upper quadrant pain, mild jaundice (Common bile duct remains patent)
What is emphysematous cholecystitis?
Intramural gas in gallbladder wall
What is the Empyema of the gallbladder?
Complication of cholecystitis?
What is the cause of Empyema of the gallbladder? How does it present it self?
Frank pus in gallbladder
Presentation is as for cholecystitis but septic presentation:
Severe pain
High fever
Chills and rigors
What is cholangitis?
Inflammation/infection of biliary trea ( hepatic and common bile duct)
What is the cause of cholangitis?
Mainly obstruction of common bile duct
Can follow instrumentation (e.g. endoscopic retrograde cholangio-pancreatography, ERCP)
Presentation of cholangitis?
Fever (rigors), jaundice and right upper quadrant pain
Presentation may be non-specific
What are the different routes of causing Pyogenic liver abscess?
Biliary obstruction
Direct spread from other intra-abdominal infections
Haematogenous
Penetrating trauma
Idipoathic normally found this way
What are the two haematogenous routes for causing pyogenic liver abscess?
From mesenteric infection
via hepatic portal vein
From systemic intravascular infection
via hepatic artery
What is intra-peritoneal abscess?
Localised area of peritonitis with build-up of pus.
For example Subphrenic, subhepatic, paracolic, pelvic
What are the predisposing factors for intra-peritoneal abscess?
Perforation Cholecystitis Mesenteric ischemia/bowel infarction Pancreatitis/pancreatic necrosis Penetrating trauma Postoperative anastomotic leak
What are the different types of perforation that cause intra-peritoneal abscess?
Peptic ulcer
Perforated appendix
Perforated diverticulum
Is the development of intra-peritoneal abscess fast acting or slow?
Can be a complication that occurs up to several months after the presenation of the predisposing factor
What is the non specific presenation of intra-peritoneal abscess?
Sweating, anorexia, wasting
High swinging pyrexia
What are the localising features of intra-peritoneal abscess?
Subphrenic abscess –> accumulation of infected fluid between the diaphragm, the liver and the spleen.
Pelvic abscess
What are the features of subprenic abscess? (5)
Pain in shoulder on affected side,
Persistent hiccup,
Intercostal tenderness, Apparent hepatomegaly (liver displaced downwards, Ipsilateral lung collapse with pleural effusion
What are the 2 features of pelvic abscess?
Urinary frequency
Tenesmus –> a continual or recurrent inclination to evacuate the bowels
What is spontaenous bacterial peritonitis?
presented by people with chronic liver disease who have bacteria in there peritoneal (no reason for perforation to occur )
Infection of ascitic fluid
What is the cause of amoebic abscess?
Entamoeba hstolytica?
What is the cause of hydatid cyst ?
Echinococcus granulosus
Parasite in the liver and causes cyst development
How is Illeocaecal tuberculosis found?
Cause by M.tuberculosis
Very similar symptoms to TB and found by Ct scan
`What 2 aerobic gram negative bacilli causes intra-abdominal infection?
Enterobacteriaceae (coliforms) –> predominantly E.coli
Pseudomonas spp.
`What 2 anaerobic Gram negative Bacilli causes intra-abdominal infection?
Bacteroides spp.,
Prevotella spp.
What 2 aerobic Gram positive cocci causes intra-abdominal infection?
Enterococcus spp.
Occasionally milleri-group streptococci
What aerobic Gram positive bacilli causes intra-abdominal infection?
Clostridium spp.
What is the cause of Liver abscess?
Usally poylmicrobial –> multipel cases
Infections secondary to haematogenous spread or trauma may not involve normal GI flora
What does it mean by sterile in terms of liver abscess?
The cause of liver abscess is one that is not grown in the lab. It is not one of the usual organisms encountered and therefore does not grow.
Where does the flora causing hepatobiliary tract infection orignate from?
It is usually flora from the lower GI.
How do you diagnose intra-abdominal infections?
History
Examination
Investigations
Blood tests
Imaging
Microbiological
What blood tests are done for intra-abdominal infections?
Full blood count: neutrophilia/neutropenia
C-reactive protein: raised
Liver function tests: abnormal in hepatobiliary disease
What imaging do you do in inta-abdominal infections and waht might you see?
Chest x-ray
Consolidation, pleural effusion adjacent to infected area (e.g. subphrenic abscess)
Abdominal ultrasound
Abdominal masses
Free fluid
Dilated bile ducts
Abdominal CT scan
Higher definition than ultrasound
What samples are tested in microbiological investigations for intra-abdominal infection?
Blood
Peritoneal fluid
Ultrasound/CT guided drainage fluid
What test are done in the microbiological investigations for intra-abdominal infection?
Microscopy, culture and sensitivity testing
How is intra-abdominal infections treated?
Treat underlying condition
e.g. resection, anastomosis, abscess drainage, biliary drainage
Start Smart… Best guess (empirical) antibiotics cover probable infections.
Then focus –> narrow possible spectrum based on culture results
Oral switch –> after 48h
What broad based Ab given to patients under the age of 65 with intra-abdominal infection?
Cefuroxime & metronidazole
What broad based Ab given to patients over the age of 65 with intra-abdominal infection?
Piperacillin/tazobactam
