Infection Flashcards
Infective gastroenteritis
Inflammation of stomach and intestines due to infection
- 3+ stools in 24 hours +1 (fever, vomiting, abdominal pain, blood/mucus)
Non-inflammatory gastroenteritis
Secretory enterotoxin mediated. Watery diarrhoea.
- Enterotoxigenic E. Coli (travellers)
- Bacillus
- Staph aureus
- Rotavirus
- Norovirus
- Giardia
- Cryptosporidium
- Vibrio cholera
Inflammatory gastroenteritis
Toxin damage and mucosal destruction. Bloody diarrhoea + pain/fever etc
- E. Coli (SLT)
- Campylobacter
- Shigella
- Salmonella
- Staph aureus
- Entamoeba histolytica
- Adenovirus
- C. Diff - prevent (4C’s)
Infective gastroenteritis investigations
- Assess hydration
- Inflammatory features (bloods)
- Routine stool culture (campylobacter, E. Coli O157, Salmonella, Shigella)
- Specific stool culture
- PCR (viral)
- Stool microscopy (parasite)
- Blood culture
- Renal function
- Imaging
Infective gastroenteritis management
- Hygiene (prevention)
- Rehydration
- Fasting
- Antimicrobials
- Tx of complications
- Metronidazole for parasitic
Haemolytic-uraemic syndrome (HUS)
- Acute renal failure
- Haemolytic anaemia
- Thrombocytopenia
Bloody diarrhoea, fever, vomiting, weakness following E. Coli O157 infection
Post-campylobacter infection
- Polyneuritis
- Reactive arthritis
Sepsis-3
Life-threatening organ dysfunction (q-SOFA>2) due to dysregulated host response to infection (usually bacterial)
Sepsis mechanism
- Breach of integrity of host barrier
- Bacterial toxin release
- Mediator release
- Effects of excessive mediators
- Exotoxin: Th1 -> pro-inflammatory -> septic shock + MODS
- Endotoxin: Th2 -> anti-inflammatory -> immunoparalysis
qSOFA
Systolic BP < or = 100 mmHg
Altered mental status
RR > or = 22
Sepsis investigations
Bloods:
- FBC
- LFTs
- Coagulation
- U&Es
- CRP
- lactate
Sepsis-6
ABCDE Take 3: - Blood cultures - Serum lactate - Urine output Give 3: - IV antibiotics - IV fluids - Oxygen
Septic shock
Fluid refractory hypotension requiring vasopressors to maintain MAP >65 mmHg with serum lactate >2 mmol/L
HIV virological mechanism
- Viral surface glycoproteins (gp120) bind to CD4 glycoprotein on host cell surface
- Virus penetrates host cell and releases RNA
- Reverse transcription
- Transcribed DNA incorporated into host genome
HIV aetiology and spread
- Sexual transmission
- Blood exposure - IVDU, needlestick, transfusion
- Vertical transmission
- Organ donation
HIV symptoms
- Weight loss
- Lymphadenopathy
- Opportunistic infection: thrush, skin, oral
- (Primary infection) Flu-like
HIV investigations
- Serum (acute/recovery phase) - antigen/antibody presence
- CD4 lymphocyte count (<200 -> symptomatic)
- PCR assay (viral load)
HIV management
Lifelong antiretroviral therapy
- Reverse transcriptase inhibitors
- Integrase inhibitor
- Protease inhibitor
Prevention:
- Education and behaviour
- Pre- and post-exposure prophylaxis
Blood or body fluid exposure
Hand hygiene
Encourage bleeding
Hep B > Hep C > HIV
Pyrexia of Unknown Origin
> 38 degrees
- Caused by pyrogens acting on the hypothalamic thermoregulatory centre (vasoconstriction, decreased peripheral heat loss)
PUO classifications
- Classical
- Nosocomial
- Neutropenic
- HIV associated
Staphylococcus aureus bacteraemia
- Gram +ve cocci in bloodstream (toxin or non-toxin mediated)
- Any infection, broken skin
- Examination: fever, hypotension, tachycardic/pnoea
- Microscopy, cultures and imaging
- IV antibiotic therapy
Outbreak
2 or more cases of infection linked in time and place
- IPC: prevent
- Surveillance: detect and identify
Infection chain
- Infectious agent
- Reservoir
- Portal of exit
- Transmission
- Portal of entry
- Susceptible host
Breaking infection chain
- Diagnose and treat
- Cleaning, disinfection and sterilisation
- Hand hygiene, PPE, resp hygiene
- Hand hygiene, PPE, cleaning etc, isolation, food safety
- Hand hygiene, PPE, first aid, removal of devices (e.g. catheter)
- Immunisations, education
Mode of transmission examples
- Direct contact: E. Coli
- Aerosol: COVID, influenza
- Ingestion: campylobacter, norovirus, C. diff
- Vector-borne: Lyme, malaria
Influenza virology
RNA virus
- Surface proteins haemagglutin antigen (attach host cell) and neuraminidase antigen (virion release)
- Antigenic shift (H/N mutations)
Influenza transmission
Seasonal - winter
- Airborne (droplet)
- Contact
Influenza symptoms and complications
Incubation: 2-4 days - Fever - Cough - Fatigue/myalgia (weakness) - Headache - Sore throat Note: influenza like illness (WHO) - fever and cough in <10 days
Complications: acute bronchitis, pneumonia (CURB65), peri/myocarditis, polyneuritis
Influenza investigations
Viral nose/throat swabs Blood culture CXR Bloods ABG
Influenza management
- Oxygen if needed (<92%)
- Neuraminidase inhibitors: Oseltamivir
- Vaccination, PPE and hand/resp hygiene
Fungal infections
Opportunistic!!
- Impaired immune system
- Chronic disease
- ICU
Fungal species
Aspergillus
Candida
Cryptococcus
Aspergillus infection
Invasive pulmonary aspergillosis
- Acute, Sub-acute, Chronic (>3 mth), Allergic
- Airborne
Aspergillosis symptoms
- Fever
- Chest pain
- Cough
- Haemoptysis
- Dyspnoea
Aspergillosis investigations
- Sputum culture
- Biopsy
- CT chest
- Blood cultures
- Bloods (IgG/E)
Candida infection
Candidiasis
- Mucocutaneous: moist areas
- Invasive (gut commensal)
Risk Factors:
- Antibiotic use
- Impaired immune system - neonate, illness
- Chronic disease
- Medical devices/surgery
Candida investigations
- Fever + chills that doesn’t improve with antibiotics
- Bloods
- Blood cultures
- Clinical: oral candidiasis (thrush) etc
Cryptococcus infection
Cryptococcosis
- Aerosol from environment
- Organism can cross blood-brain barrier (cryptococcal meningoencephalitis)
Cryptococcosis symptoms
From asymptomatic to pneumonia (chest pain, cough, fever)
- Headache
- Confusion
- Visual disturbances
- Coma
Cryptococcosis investigations
CSF
- Culture (and cryptococcus antigen)
- Protein (high)
- Glucose (low)
Blood
- Culture and antigen
Antifungals
IV (…azoles)
- Amphotericin B formulations
- Azoles
- Echinocandins
- Flucytosine
Zoonosis
Infections that are naturally transmitted between vertebrae animals and humans
- Virus: rabies, ebola, yellow fever
- Bacterias: salmonella, campylobacter, Toxoplasma
- Parasites
- Fungi
Rabies
Viral zoonose
- Bite of infected animal (dogs, bats etc)
