micro Flashcards
mechanisms of abx resistance
may be intrinsic
evoked or evolved
- inactivation - enzyme production e.g. beta lactamase
- target site modification - structural changes to bacterial components e.g. ribosomes
- decreased cell wall permeability - structural changes
- active expulsion - efflux pumps
common resistant organisms
MRSA: sensitive to vanc / teic
C.diff
VRE: linezolid, tigeycline
ESBL (e.coli / klebsiella): carbapenem
Carbapenemase producing enterobacteracae CPE
Pseudomonas: piptaz, quinolones, carbapenems
antimicrobial stewardship
infection control, judicious abx management
optimise drug choice, timing, dose and duration to eradicate infection and reduce negative effects of antimicrobials (nosocomial infection, resistant organisms)
strategies in antimicrobial stewardship
- involvement of microbiologist
- cultures prior to starting
- isolating patients with resistance organisms
- formulary restriction
- optimisation - de-escalation, short courses, enteral conversion
- restrictive antibiotic strategies
- dose optimisation - avoid subtherapeutic doses
- education and training
PCT for de-escalation
bactericidal activity of antibiotics
Minimum inhibitory concentration MIC - concentration of antimicrobial required to completely inhibit visible growth
time-dependent killing - bactericidal when concentration above MIC consistently
concentration dependent killing - bactericidal when peak concentration above a certain level
AUC / MIC - concentration and time dependent killing effects
SDD
selective decontamination digestive tract
SDD reduce overall mortality by 6%
Pyrexia in critical care
- infection responsible for 73% pyrexia
- < 72hrs likely to be non-infectious post SAH or elective surgery
Systematic consideration of sources
A - dental abscesses, tonsilitis, sinusitis
B - Pneumonia, tracheitis, empyema
C - IE
D - meningitis, encephalitis, cerebral abscess
E - cellulitis, nec fas, septic arthritis, ifnected pressure sore
F - UTI, pyelonephritis
G - cholecytisits, peritonitis, diverticulitis, appendicitis
GU - PID, epidymo-orchitis, prostatitis
considerations invesitgating PUO
- fever - onset, severity, course
- systemic sx - weight loss, night sweats, skin lesions
- vaccination
- unwell contacts
- activities - travel, country, alcohol, drugs, animals
- relevant diseases - HIV, malignancy, sickle cell
considerations of managing bacterial infection
- suspected source - broad, narrow spectrum, tissue penetration
- duration in hospital
- previous cultures
- positive cultures
- toxin production
- severity of illness - septic, stable
- extracorporeal circuits
- route of adminsitration
- guidelines / micro advice
stopping abx
individualised
clinical improvement - e.g. improved gas exchange, resolving pyrxexia
prolonged courses indicated in some situations - IE, osteomyeletis
biomakers
Common viruses in critical care
orthomyxoviridae - infuenza ABC
Coronaviridae - SARS, MERS, covid-19
Herpesviridae - HSV, VZV, CMV, EBV
paramyxoviridae - RSV, measles, mumps
flaviviridae - dengue
filoviridae - ebola
virus classification
DNA or RNA surrounded by protein capsid. capsid helical, icosahedral or complex. some have outer envelope or are naked
RNA
- icosahedral naked - picornavirus. enveloped - flavivirus
- helical enveloped - coronavirus, orthomyxovirus
- complex -retrovirus
DNA
- icosahedral naked - parvovirus
- icosahedral enveleoped - herpes
challenges of fungal infections in critical care
- insidious presentation - hard to diagnose
- prolonged courses of treatment
- significant side effects of treatment
- high mortality
types of fungal infections
moulds : aspergillus
yeasts : candida, cryptococcosis
dimorphic : histoplasma
primary: immunocompetent patients. abundant spores and some innate virulence
secondary : opportunistic, less innate virulence but cause disease in immune impaired
risk factors for fungal infection
- icu admission
- immunocompromised
- respiratory compromise - CF, COPD
- invasive procedures
- broad spectrum antibiotics
- gut contamination
invasive candidiasis
commonest fungal infection in ICU
usually superficial colonisation but candidaemia has high mortality
haematagenous spread - heart, liver, brain, eyes
echo / ophthalmology review
positive blood cultures need detailed assessment
fluconazole / anadilafungin treatment
aspergillus
- invasive pulmonary aspergillosis
- chronic cavitatory aspergillosis
- extra pulmonary aspergillosis
- allergic bronchopulmonary aspergillosis - steroids, antifungals
- aspergilloma
- angio- invasion e.g. massive haemoptysis
other fungal infections
PCP
- progressive dyspnoea, dry cough, exertion desaturation, air leaks
crpytococcus
- pulmonary cryptococcosis - infiltrative pneumonia
- meningoencephalitis - slow progressive
- relatively immune modulation - inflammation / immune reconstitution on treatment
mucormycosis
- disseminated infection, angio invasion, necrosis
fungal disease investigations
- mc/s relevant fluid / tissue
- beta d glucan - most infections
invasive candidiasis - blood culture
- serum mannan / anti-manna
- fundoscopy
- pcr
aspergillosis - serum / bal galactomannan - relatively specific
- CT chest - air crescent, halo sign
- histology
PCP - sputum / bal per
- cxr / ct
anti fungal classes
polyenes - amphotericin b - cell wall damage . cryptococcosis
azoles - voriconazole (aspergillosis), fluconazole (candida)- inhibit cell wall synthesis.
echinocadins - inhibit b glucan synthesis - caspo / anadulofungin
flucytosine - incoproated in rna
anti fungal side effects
fluconazole / voriconazole - liver, qtc, cytochrome p450
anidulafungin - liver
amphotericin - renal, eleectrolyte
anti fungal prophylaxis
- neutropenia
- ALF
- HIV
- follow transplant
- gi perforation
nosocomial infection definition
- infection after 48hrs admission
- within 3 days of hospital discharge
- within 30 days of an operation
common, preventable, increase mortality and morbidity
factors predisposing to nosocomial infection
patient
- elderly
- malnutiriton
- alcohol
- chronic lung disease
- diabetes
disease
- surgery
- trauma
- burns
treatments
- invasive procedures - intubation, catheters, drains
- transfusion
- antimicrobials
- immunosuppression
- prolonged LOS
Nosocomial infection examples
Blood stream / central line associated / catheter related
- CRBSI - bloodstream infection attributed to intravascular catheter (quantitative culture of tip or difference in growth between catheter and peripheral blood cultures).
- CLABSI - lab confirmed BSI in patient with indwelling central line < 48 hrs prior to development of infection, unrelated to another infection
- coagulase neg staph, staph aureus, candida
Pneumonia
- pseudomonas, staph aureus, enterobacter, klebsiella
catheter associated UTI
- pseudomonas, enterococci, E Coli
Surgical site infections
- staph, coagulase negative staph, enteroccoci
line infection prevention / managament
minimise insertion / evaluate need
catheter type - abx impregnated, minimal lumens, dedicated PN
site - subclavian > IJ > femoral
ANTT on insertion
optimum care - disinfect, flushes
replacement - avoid routine
management
- catheter removal - sepsis, persistently positive cultures, persistent symptoms
- precious lines may be treated medically
other factors preventing nosocomial infection
- hand hygiene
- PPE
- VAP bundles
- Antimicrobial stewardship
- line care
HIV
Human immunodeficiency virus
retrovirus infecting CD4 T cells
viral RNA transcribed into DNA by viral reverse transcriptase enzymes
chronic progressive immune deficiency
HIV diagnosis
serological test HIV-1 p24 antigen
may be positive from day 18
antibody test positive from 3 months
HIV stages
0 - early - CD4 count negative
1 - Acute - CD 4 > 500
2 - chronic - CD4 200-499
3 - AIDS - CD4 < 200 or OI
Opportunistic infections (AIDS defining)
Bacteria: mycoplasma - TB, MAC, recurrent pneumonia
Fungal: PCP, oesophageal candidiasis, cryptococcus
Viral: CMV retinitis, oesophagitis. HSV pneumonitis
Parasitic: toxoplasmosis
Neoplastic: Kaposi sarcoma
HIV presentations to critical care
- complications of disease
- significant side effects of treatment
- pathology not directly related
sepsis and respiratory failure commonest, followed by CNS issues
Severe opportunistic infections tend to occur in patients previously not known to have HIV or those with restricted access to HAART
HAART classifications
NRTIs: lamivudine, zidovudine, tenofovir
NNRTI: efavirenz
integrase inhibitors: raltegravir
Protease inhibitors: lopinavir
HAART side effects
Most can cause hepatitis
lactic acidosis: zidovudine
AKI: tonofaviar
TEN: tenofovir
Immune reconstitution inflammatory syndrome
IRIS
inflammatory disorders associated with paradoxical worsening of infectious conditions following ART initiation
worsening of treated condition or unmasking of OI
resp failure - worsening of PCP
HLH
management of ART
if already taking then continue where possible
adjust doses according to organ failure
commencing de novo individualised decision
- immediate - severe acute OI
- < 2 weeks other OI
- delayed - T
PCP management
BAL, PCR, beta d glucan, CT for diagnosis
mx septrin
steroids if pao2 < 9
TB
AFB, MC/S, PCR
tissue biopsy
Mx RIPE 2 months then 9 months RI
steroids if CNS
cerebral toxoplasmosis
altered mental state, seizures
parasite
IgG serology, CSF/blood PCR t.gondii
pyrimethamine, sulphadizeine, leucovorin
HIV risk factors
- MSM
- IVDU
- Prisoners
- Patients from areas of high prevalence
- sex workers
ICU testing - AIDS defining OI, indicator conditions - CAP, invasive pneumocococcal disease
- GBS
- unexplained fever, weight loss, chronic diarrhoea
- malignant lymphoma
- VZV, HBV, HCVm candidaemia
Malaria
life threatening tropical infection
protozoa transmitted by mosquitoes
plasmodium falciparum in nearly all serious illness
Vivax / ovale / malaria less severe
risk factors
- travel to endemic areas - Africa, Asia, Latin America
- mosquito bites
- poor compliance with chemoprophylaxis
Malaria pathophysiology
life cycle depends on mosquito and humans
1. human liver stage - human bitten by mosquito, parasites travel to liver, mature into schizonts, hepatocytes rupture and merozoites are released in bloodstream
2. merozoites infect erythrocytes, multiple into trophozoites and onto schizonts. erythrocytes rupture - further merozoites into blood
3. mosquito stage - gametocytes in mosquito undergo sexual reproduction and produce eggs, release sporozoites into mosquito saliva
malaria diagnosis
suspicion, history
presents 12-14 days after inoculation
fever, altered mental state, seizures, jaundice
blood film - thick and film microscopy
- thick = organism
- thin = quantified parasitaemias
severe malaria
B : pulmonary oedema, SPO2 < 92%
C: Shock, SBP < 80
D : GCS < 11, seizures, glucose < 2.2
F : creat > 265
G : Bili > 50
H : Hb < 70
I : pataistaemia > 10%
malaria treatment
parenteral if paristaemia > 2% or jaundice
anyone witht evidence of severe disease IV
Artesunate 2.4mg/kg 12hrly 3 doses then daily
Quinine if artesunate not available 20mg/kg then 10mg/kg
Supportive Mx of complications
- ARDS
- Cerebral malaria - anti epileptics, airway control
- AKI - RRT if required
- Anaemia - restrictive transfusion
- Coagulopathy - products as indicated
varicella zoster virus
mild fever, maculopapular rash, vesicular, scab
10-21 day incubation. infectious 2 days before rash until crusted
complications - arthritis, secondary bacterial infection, pneumonitis, encephalitis, facial nerve palsy
Dengue fever
virus transmitted by mosquitoes
4-7 day incubation
fever, headache, myalgia
sever disease = dengue haemorrhage fever
acute vascular permeability - hypoproteinaemia, hypovolaemia, effusions, dengue shock
abnormal haemostats - haemorrhage, thrombocytopenia
Leptospirosis
leptospirosis spirochetes
rodent , cattle, dog urine
direct / mucosal contact
5-14 day incubation
asymptomatic, flu like illness to MOD
positive culture / pcr
can cause vasculitis, renal, liver, myocarditis
doxycycline / IV penicillin / cephalopsorins
Toxoplasmosis
protozoal infection
T.gondii
food, congenital, zoonotic (cat faeces)
flu like illness, retinitis, lymphadenopathy
pyrimethamine, sulphanmide
