Infectious Diseases Flashcards
Gram-negative, lactose-fermenting bacillus and a common cause of UTI.
E Coli.
(Responsible for 75-95% of UTI, but a normal commensal of large intestine. Transfer to urinary tract can be via bloodstream / lymphatics / direct extension e.g. vesicocolic fistula / ascending transurethral route most common - esp. in women).
Gram-Positive, alpha-haemolytic diplococcus that causes lobar pneumonia.
Streptococcus pneumonias.
(90% of pneumonia due to Strep. pneumoniae. Colonies described as “draughtsman shaped” due to their sunken centre. Homeless and alcoholics with poor social/medical care are v prone to lobar pneumonia).
Gram-positive, anaerobic, cytotoxin producing bacillus causing pseudomembranous colitis.
Clostridium difficile.
(Toxigenic strain. C diff produces two toxins: Toxin A - enterotoxin responsible for gut symptoms, Toxin B - cytotoxin with cytopathic effect in cell cultures).
S-shaped urease-positive bacillus, major cause of chronic gastritis and peptic ulcer disease. Stains poorly with gram stain.
Helicobacter pylori.
H. pylori is a flagellate bacillus that produces urease and colonises the gastric antrum.
Helicobacter pylori is associated with an increased risk of developing which conditions?
- Chronic gastritis.
- Duodenal ulcer.
- Gastric adenocarcinoma.
- Primary gastric lymphoma.
How is Helicobacter pylori tested for?
- Serology for IgG antibodies.
- Urea breath test.
- Endoscopy: rapid urease test, microbiological culture, histological identification in gastric biopsy.
How is Helicobacter pylori best visualised?
Modified Giemsa stain.
Gram negative coliforms.
- E. Coli
- Klebsiella
- Enterobacter
- Proteus
Which antibiotic are most gram negative coliforms and Pseudomonas aeruginosa sensitive to?
- Gentamicin.
- Aztreonam.
Extended spectrum beta lactamases are resistant to most of which antibiotic?
Penicillins e.g. co-amoxiclav, piperacillin tazobactam, aztreonam.
Which antibiotics do extended spectrum beta-lactamases have sensitivity to?
- Temocillin.
- Pivemcillinam.
- Meropenem.
Anaerobes are generally sensitive to which antibiotics?
- Metronidazole.
- Co-amoxiclav, Clindamycin, Pip-tazobactam, Meropneme.
Gram positives e.g. Staph aureus, Streptococci and Enterococci are sensitive to?
Vancomycin.
Beta-haemolytic streps are sensitive to?
- Penicillin.
- Flucloxacillin.
Which investigations are needed for infection of the CNS?
- Blood cultures.
- Bacterial and viral throat swabs.
- EDTA for bacterial PCR.
- CSF sample if safe to do so.
Which organisms are likely to cause epiglottitis?
- Haemophilus influenza.
- Streptococci.
Which organisms are likely to cause meningitis in someone >60 y/o?
Listeria, meningococcus, pneumococcus.
Which investigations are needed for pneumonia?
- Blood cultures.
- Viral throat swab.
- Sputum for bacterial culture.
- BAL or tracheal aspirates if clinically indicated (PCR for legionella or PCP).
Likely causative organism in someone with acute native valve endocarditis?
Staph. aureus.
Likely causative organism in someone with subacute native valve endocarditis?
- Viridans streptococci.
- Enterococci.
Likely causative organism in someone with prosthetic valve endocarditis?
- MRSA.
- Coagulase negative Staphylococci.
What microbiology samples should be taken from someone with a central venous catheter related infection?
- blood cultures from peripheral site and the line using strict aseptic technique.
- Swab exit site if infected.
Likely causative organism in someone with peritonitis / biliary tract sepsis / intra-abdominal infection?
- Polymicrobial coliforms.
- Anaerobes.
- Enterococci.
Likely causative organism in someone with spontaneous bacterial peritonitis?
- Coliforms +/- anaerobes.
- Strep. pneumonia.
Investigations in someone with suspected E. Coli 0157 infection?
- FBC, U+Es, LDH, CRP.
- Blood film (fragmented blood cells in HUS).
Likely causative organism in a female with uncomplicated UTI?
- Coliforms.
- Enterococci.
Likely causative organism in a male with UTI (not catheter related)?
- Coliforms.
- Enterococci.
Likely causative organism in someone with complicated UTI / pyelonephritis urosepsis?
- Coliforms.
- Pseudomonas aeruginosa.
- Enterococci.
Likely causative organism in someone with cellulitis?
- Staph. aureus.
- Group A and other beta-haemolytic Streptococci.
Likely causative organism in someone with acute diabetic foot infection?
Staph aureus.
Likely causative organism in someone with acute on chronic polymicrobial diabetic foot infection?
- Staph. aureus.
- Coliforms.
- Anaerobes.
Why is Ceftriaxone used in CNS infections?
- Need for high CSF levels to be maintained.
- Easy dosing (twice daily).
Listeria is resistant to X but sensitive to Y.
- X - Cephalosporin.
- Y - Amoxicillin.
