Microbiology Flashcards
If a biliary infection is suspected, what is the 1ary imaging technique?
Abdominal US
Define acute bacterial gastroenteritis
An illness of <14 days duration characterised by the presence of diarrhoea (3 or more loose stools per day or bloody stools). It is typically self-limiting.
What is the cause of acute bacterial gastroenteritis?
Ingestion of food or water contaminated by GI flora
Give some common pathogens causing bacterial gastroenteritis
- Campylobacter
- Salmonella
- Shigella
- E. coli
- Clostridium perfringens
Symptoms of bacterial gastroenteritis?
- Diarrhoea
- Abdominal pain/cramps
- N&V
- Fever
Eating what is a big risk factor for bacterial gastroenteritis?
Raw or undercooked foods
Which occupation is a risk factor for bacterial gastroenteritis?
Farmers or workers in the meat industry
Which ages are a risk factor for bacterial gastroenteritis?
<5 y/o
>60 y/o
Is antibiotic therapy recommended in acute bacterial gastroenteritis?
No - most patients with acute gastroenteritis have no adverse complications from acute gastroenteritis and derive no benefit from antibiotic therapy
What management is suggested for bacterial gastroenteritis?
Rehydration
Which 3 groups of patients do require antibiotics for bacterial gastroenteritis?
- Pregnant women
- Immunosuppressed
- Symptoms lasting >7 days
Who should cases of infective gastroenteritis be reported to?
PHE (particularly those involving food handlers)
What is C. difficile infection?
Infection of the large bowel by C. difficile
What is C. difficile infection?
Infection of the large bowel by C. difficile
Symptoms of C. difficile infection?
- Fever
- Abdominal pain
- Loose stools
Describe stool appearance in C. difficile infection
Green
Slimy
Maloderous
One major risk factor for C. difficile infection is previous antimicrobial therapy. Which antibiotics are the biggest risk factors?
The ‘C’ drugs: ciprafloxacin, cephalosporins, co-amoxiclav, clindamycin (and quinolones)
Give other risk factors for C. difficile infection
- Old age (>65 y/o)
- Hospitalised patients
- Previous antimicrobial therapy
- Long duration of antibiotic use (>7 days)
- Multiple antibiotic courses
- Severe underlying disease
- Presence of nasogastric tube
- Non-surgical GI procedures
- PPIs
What are the 2 diagnostic criteria for C. difficile infection?
- Presence of loose stools (type 5-7)
- Positive C. diff test (or clinical suspicion while awaiting results)
What is the 1ary test for C. difficile infection?
Stool sample
What is the non antimicrobial treatment for C. diff infection?
Fluid resuscitation and electrolyte replacement as appropriate
Which policies need to be instigated in a C. diff infection?
Immediate instigation of isolation policy and Clostridium Difficile Infection Control Policy.
Is antibiotic therapy used to treat symptomatic C. diff infection?
Yes most often
What are the 2 most commonly used antibiotics in treating C. diff infection?
Oral vancomycin
Oral fidaxomicin
Why are oral antibiotics, not IV, used to treat C. diff infection?
When given orally they only work in the intestines and NOT absorbed (this is where the infection is)
Which antibiotic is most effective in life threatening C. diff infection?
Oral vancomycin
Do serum levels of oral vancomycin need to be monitored? Why?
No - serum levels do not need to be monitored when given orally as it is NOT absorbed
What bacteria is resistant to vancomycin?
VRE (vancomycin resistant enterococci).
What is the mechanism of action of fidaxomicin?
Inhibits bacterial RNA polymerase
Does Fidaxomicin or Vancomycin cause less disruption to the normal gut flora?
Fidaxomicin (therefore less capacity for C. Difficile spores to germinate)
What is the function of the gut microbiome?
Aid digestion, regulate the immune system and protect against infection
How does the gut microbiome protect against infection?
Is composed of around 39 trillion bacteria which provide a physical barrier to more harmful bacteria, and compete for space and nutrients which limit the potential for pathogenic bacteria to multiply.
How does antibiotic use lead to C. diff infection?
Antibiotic use causes disruption of the gut microbiome and therefore results in a disbalance of bacteria population → which creates an ecological niche for C. difficile spores to germinate.
What is colonisation resistance?
Intestinal microbiota protects itself against incursion by new and often harmful microorganisms.
Which class of antibiotics lead to the most frequent allergic reactions?
Beta-lactams
What information is important to get from a patient history regarding antibiotic allergies?
- What antibiotics has the patient reacted to in the past?
- When did the reaction take place?
- How long after administration?
- What is the nature of the reaction? → rash vs anaphylaxis (if rash, then describe: maculo-popular, pustular, urticarial etc.)
- Did the reaction resolve on cessation of the antibiotics?
What type of allergic reaction is typically mediated by penicillin specific IgE?
Type 1 (<1 hour)
What is cholecystitis?
Inflammation of the gallbladder
What is cholecystitis?
Inflammation of the gallbladder
What is the most common cause of cholecystitis?
Cystic duct obstruction from cholelithiasis (calculous cholecystitis) i.e. gallstones
What is acalculous cholecystitis?
An inflammatory disease of the gallbladder without evidence of gallstones or cystic duct obstruction.
Who is acalculous cholecystitis seen primarily in?
Critically ill patients
What clinical signs might be found in cholecystitis?
- Positive Murphy’s sign
- RUQ guarding/pain
- Jaundice
- Fever
Which LFTs may be elevated in cholecystitis?
ALT & AST
What imaging cause be used to demonstrate bile duct dilatation and/or stones in cholecystitis?
Ultrasound
What is complicated acute diverticulitis?
Acute diverticulitis accompanied by abscess, fistula, bowel obstruction or perforation
Treatment of complicated acute diverticulitis?
Broad spectrum antibiotics (until blood cultures come back)
Potential drainage of abscess
What are MDR organisms?
Multidrug-Resistant Organisms
Give some examples of MDR organisms
ESBL
VRE
MRSA
How should the patient be kept if MDR organisms are identified?
In source isolation (ESBL and VRE and tramissible)
