ID - Infection/Micro OSCE Flashcards
Antimicrobial Resistance
Innate - lack of target, membrane impermeabilityAcquired:1 - Drug inactivation - beta-lactamases (staph and pseudomonas)2 - Reduce permeability - Pseudomonas impermeable membrane3 - Efflux of drugs - mainly gram negatives (Pseudomonas pumps out penicillins, tetracyclines and quinolone)4 - alteration of molecular target (altered cell wall substrate with VRE)Molecular: sporadic mutations, release of free DNA, bacteriophages (viruses), plasmids, transposons
Mx:1 - Antimicrobial stewardship 2 - Use of local Microguide 3 - Micro sampling prior to starting abx4 - rigorous infection control
How does Necrotising fasciitis present?
Life-threatening infection of the deep fascia and subcut fat
Diff Dx: trauma/burn, SJS/TEN, cellulitis
Features: pain!!, erythema, features of gangrene, systemic (low BP, shock)
Type 1 - polymicrobial
Type 2 - group A strep
Inx: CT/MRI/US - but may not have time —— Surgery!
Mx: ABCDE, analgesia, septic screen, abx - clindamycin and taz, early surgical review
Others: ICU, IVIG and hyperbaric O2
PVL staph
Staph which produces a toxin ‘Panton Valentine Leukocidin’ which is toxic to WBCs.Necrotizing pneumoniaMx: linezolid, clindamycin, rifampicin +/- IVIG
What is the evidence for colliods in sepsis?
6S trial - increased mortality and RRT with HES
CHEST - increased RRT with HES
SAFE - non-sig trend to benefit with albumin
ALBIOS - no mort diff with albumin but decreased pressor requirement
Sepsis and EGDT
Rivers - decreased mort but issues with trial| ProCESS, ARISE and PROMISE - all show no benefit from EGDT
Sepsis and BP targets
SEPSISPAMMAP 80-85 vs 65-70No mort difference, increased AF with higher targetPts with chronic HTN less likely to increase Creat or need RRT in higher group
Whatis the evidence for the use of specific vasopressors in sepsis
VASST - NA vs NA and VP - no mort diff but VP is NA sparing
VANISH - VP vs NA - no difference (also inc hydrocortisone vs placebo)
LeoPARDS - Levosimendan - no difference
Whatis the evidence of steroids in Sepsis
CORTICUS - Hydrocortisone vs placebo - no diff
HYPRESS - Hydrocortisone vs placebo - no diff
ADRENAL - Hydrocortisone vs placebo - no mort diff but decreased shock and ICU stay
APROCCHSS - Hydrocortisone and Fludrocortisone - decreased mort and less pressors
How can Tetanus present
Clostridium tetani Spores in soil, enter broken skin, release toxin ‘tetanospasmin’ Binds irreversibly and blocks inhibitory neurotransmitters - unopposed motor and autonomic activity
Autonomic:
Sympathetic storm - HTN, tachy, dysrhythmias
Sudden CVS collapse - low BP, brady Sweating, hyper secretions, high temp
ICU:Analgesia and sedationMVSupport autonomic disturbances```
Mx:
Control Musc spasm - benzos, opiates, prop, NMB
Wound debridement
Abx - metronidazole
Tetanus IG
Tetanus vaccine
Mg - dampens sympathetic cascade```
How can Catheter-related bloodstream infection be prevented?
Prevention:Replace lines placed in an emergencyUse chlorhex - full asepsis Remove when they are not needed Subclavian
Dx - line cultures positive and blood cultures positive but with less numbers than line
Anti-fungal
Why increased in ICU? - Immunosuppression - Invasive devices - Broad spectrum abxRFS: as above plus - high apache score, co-morbidites, RRT, TPNInvasive fungal infection - bloodstream or deep site - generally felt to be from 3 sitesDx:Fungal culturesFever despite abx therapy - neg microbiology Mx:1 - Azoles - fungistatic - inhibit ergosterol synthesis - gd for most candida species - not effective against aspergillus2 - Echinocandins - fungicidal against candida, static against aspergillus - inhibit glucan synthesis3 - Polyenes - Amphotericin - binds ergosterol and causes cell death - dose limited by renal toxicity - broad spectrum All cause QT prolongationAzoles and echinocandins cause liver toxicity
Anti-virals
Aciclovir: - Nucleoside analogue - HSV - neurotoxicity and nephrotoxicity Ganciclovir: - Neucleoside derivative - CMV - myelosuppression, neurotox, hepatic toxFoscarnet: - non-competitive inhibitor of DNA polymerase - resistant CMV/HSV - nephrotoxOseltamvir: - Neuraminidase inhibitor - flu - rash, hepatitis, low pltsNRTIs: - false nucleotide - lactic acidosis, hepatic steatosis NNRTIs: - binds to and inhibits reverse transcriptase - hepatotoxicity PI: - Prevents processing of HIV proteins - SJS and dyslipdaemiaFusion inhibits - blocks fusion of HIV into cells - GI SERemdesavir - Pro-nucleotide - metabolised into an adenosine analogue which interferes with RNA synthesis in viruses - Originally created to treat hep C and RSV (doesn’t) but can be helpful in Ebola and now COVID
HIV
Cytopathic retrovirus infects and kills CD4 t-helper cells resulting in immunosuppression
Classification: 1 - acute seroconversion 2 - assymptomatic infection 3 - persistent generalised LNs 4 - symptomatic HIV
ICU: 1 - Resp failure - PJP 2 - TB 3 - CVS disease - increased in HIV 4 - Liver failure - meds or HepB/C 5 - GI - CMV colitis 6 - Renal failure - HIV assoc. nephropathy 7 - Neuro complications - enceph, meningitisImmune reconstitution: - Start HAART - immune function recovers and responds to acquired infections causing severe inflammatory response
How can PJP present
Yeast like fungus
Slow, indolent course of progressive SOB, fever and dry cough Hypoxia and diffuse opacities on CXR
Dx: BAL or induced sputum
Mx: IV co-trimoxazole and steroids
TB
Mycobacterium tuberculosis - aerobic bacilli, acid fastRFs: - Immunosuppression: HIV, DM, Tx, malnutrition, smoking, ETOH - Exposure factors: close contacts, travelDx: - Clinical: fever, wt loss, night sweats, cough - Inx: cavitation lesions - Micro: sputum/BAL, PCR, other sitesICU: - Resp failure - Massive haemoptysis - DIC - cardiogenic shock from pericardial effusion - meningitis
Meds: RIPE 1 - Rifampicin - Hepatotoxicity 2 - Isoniazid - Heptotox, peripheral neuropathy 3- Pyrazinamide - Hepatotoxic 4 - Ethambutol - Optic nerve tox
