Infection/Micro Flashcards
Antimicrobial Resistance
Innate - lack of target, membrane impermeability
Acquired:
1 - Drug inactivation - beta-lactamases (staph and pseudomonas)
2 - Reduce permeability - Pseudomonas impermeable membrane
3 - 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 abx 4 - rigorous infection control
Necrotising fasciitis
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 pneumonia
Mx: linezolid, clindamycin, rifampicin +/- IVIG
Sepsis and fluids
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
SEPSISPAM
MAP 80-85 vs 65-70
No mort difference, increased AF with higher target
Pts with chronic HTN less likely to increase Creat or need RRT in higher group
Sepsis and vasopressors
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
Sepsis and steroids
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
Tetanus
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 sedation
MV
Support autonomic disturbances
Mx: Control Musc spasm - benzos, opiates, prop, NMB Wound debridement Abx - metronidazole Tetanus IG Tetanus vaccine Mg - dampens sympathetic cascade
CRBSI
Prevention: Replace lines placed in an emergency Use 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 abx RFS: as above plus - high apache score, co-morbidites, RRT, TPN
Invasive fungal infection
- bloodstream or deep site - generally felt to be from 3 sites
Dx:
Fungal cultures
Fever despite abx therapy - neg microbiology
Mx:
1 - Azoles - fungistatic - inhibit ergosterol synthesis - gd for most candida species - not effective against aspergillus
2 - Echinocandins - fungicidal against candida, static against aspergillus - inhibit glucan synthesis
3 - Polyenes - Amphotericin - binds ergosterol and causes cell death - dose limited by renal toxicity - broad spectrum
All cause QT prolongation
Azoles and echinocandins cause liver toxicity
Anti-virals
Aciclovir:
- Nucleoside analogue - HSV - neurotoxicity and nephrotoxicity
Ganciclovir:
- Neucleoside derivative - CMV - myelosuppression, neurotox, hepatic tox
Foscarnet:
- non-competitive inhibitor of DNA polymerase - resistant CMV/HSV - nephrotox
Oseltamvir:
- Neuraminidase inhibitor - flu - rash, hepatitis, low plts
NRTIs:
- false nucleotide - lactic acidosis, hepatic steatosis
NNRTIs:
- binds to and inhibits reverse transcriptase - hepatotoxicity
PI:
- Prevents processing of HIV proteins - SJS and dyslipdaemia
Fusion inhibits
- blocks fusion of HIV into cells - GI SE
Remdesavir
- 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, meningitis
Immune reconstitution:
- Start HAART - immune function recovers and responds to acquired infections causing severe inflammatory response
PJP
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 fast
RFs:
- Immunosuppression: HIV, DM, Tx, malnutrition, smoking, ETOH
- Exposure factors: close contacts, travel
Dx:
- Clinical: fever, wt loss, night sweats, cough
- Inx: cavitation lesions
- Micro: sputum/BAL, PCR, other sites
ICU:
- 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
