Infection Flashcards
Sepsis
Life-threatening organ dysfunction due to dysregulated response to infection
Defined by q-SOFA
Altered mental status: GCS <15
RR >22
BP <100
SIRS: WCC < 4 > 12 Temp <36 > 38 HR >90 Resp >20
Symptoms: HR/BP increase, fever/hypothermia, confusion
Signs: purpura fulminans (pneumococcal septicaemia), signs assoc. with specific infections
Ix:
FBC: WBC raised
UEs: renal dysfunction, baseline to see im improves
LFTs: baseline, septic shock can compromise hepatic blood flow
Blood culture
ABG: metabolic status, lactate
CXR: source of sepsis
ECG: exclude ddx e.g. MI, pericarditis
Culture sputum/urine/stool: source of sepsis
Tx:
Sepsis 6: IV fluids, O2 (>94%), IV abx, blood culture, lactate, UO
Gastroenteritis
Inflammation of lining of stomach and SI
Also known as infectious diarrhoea (>3 loose/watery stools in 24 hrs)
Risk fx: Abx use, immunodeficiency
<24 hrs: Viral, Staph.aureus, B.cereus
24-72hrs: Bacterial
>1wk: Giardiasis, Entomeba histolytica (amoebiasis)
Diarrhoea without blood:
Norovirus
12-48hrs post-exposure
Most common cause of GI infectious disease
Contact with infected people
Sx: Acute onset, watery diarrhoea, cramps
Rotavirus Commonest diarrhoea in children 2d incubation Watery diarrhoea and vomiting Tx: supportive. Vaccincation
Enterotoxigenic
Gram -ve bacilli (anaerobe)
1-3d incubation
Most common cause of traveller’s diarrhoea and infants/children (non-bloody)
Clostridium perfringes
Gram +ve bacilli (anaerobe). Produces enterotoxin
Sudden onset diarrhoea, cramps, <24 hrs
Unrefrigerated food, involves bulk-cooked food
Staph aureus
Incubation 30 mins - 6 hrs
Vomiting, abdo cramps
Cooked meats, pastries
B.cereues
Incubation 30 mins - 6 hrs
Vomiting, diarrhoea
Reheated rice
C. botulinum
Pre-formed toxin in food. Improperly processed canned food. Infants. Wounds.
Flaccid paralysis, muscle weakness
Tx: antitoxin
Cholera: Gram -ve aerobic rod (comma shaped) Contaminated water Profuse watery diarrhoea, vomiting, metabolic acidosis Tx: oral rehydration
L. monocytogenes (gram +ve coccobaccili) Unpasteurised milk/cheese Sx: flu-like with/without diarrhoea Complications: septicaemia, meningtitis Tx: Amox+gent
Parasites: Giardia lambliani 1-3 wk incubation Faecal-oral from contaminated water/food Diarrhoea, bloating Tx: metranidazole
Amoebiasis
Entamoeba histolytica
Sx: bloody diarrhoea, colitis, toxic megacolon, amoebic liver abscess (mass containing “anchovy sauce”
Tx: Metranidazole
Bloody diarrhoea
Campylobacter (gram -ve bacilli). Usually C. jejuni
Uncooked meat esp. chicken
Bloody diarrhoea, pain, fever
Complications: Gullian Barre syndrome, reactive arthritis
Tx: fluids. Clarithromycin if severe
Salmonella (gram -ve bacilli)
Contaminated pork/poultry, dairy, pets (lizards)
Sx: bloody/watery diarrhoea, vomiting
Complications: bacteraemia, septic arthritis, osteomyelitis
Shigella (gram -ve anaerobe)
Watery diarrhoea then bloody, tenesmus, fever
1-2d after exposure
Person-person via faecal-oral route
Common in children
Complications: renal failure (part of HUS)
E.coli 0157 (enterohaemorrhagic) Contaminated food/water Produces Shiga-like toxins Bloody diarrahoea, abdo pain, vomiting HUS (haemolytic anaemoia, thrombocytopenia, renal failure)
DDx: IBD, IBS, thyrotoxicosis, drugs, constipation with overflow
Ix: FBC: anaemia (malabsorption) UEs: dehydration Stool sample/culture Sigmoiscopy: inflamed muscosa+psuedomembranes (psuedomembranous colitis Abdo XR (thrumbprinting - IBD)
Tx: Oral/IV rehydration
Notify public health
Bacterial Resp infections
Infants E.coli
Children: RSV (resp syncytial virus)
Young adults: Mycoplasma pneumoniae, S pneumoniae
Older/underlying lung disease: H.influenzae
HIV: P. jirovecii
Typical: Strep. pneumoniae, H. influenzae, Moxarella Catharallis
Atypical: M. pneumoniae, Legionella pneumophilia chlamydophilia psittaci (birds), chlamydiophilia burnetti (Q fever, farm animals)
Most common. S pneumoniae
Sx: quick-onset, cough, fever, pleuritic chest pain,
Sx: Dull percussion, coarse creps, increased vocal resonance
Tx: amoxicillin
Mycoplasma pneumoniae
Peaks in winter, children/young adult
Sx: insidious, flu-like symptoms, milder than CXR shows
Sx: CXR involves bil. lower lobes, hyponatraemia
Dx: serology (Mycoplasma-specific Ig), PCR (throat swab, sputum culture), can’t culture
Tx: self limiting, clarithyromycin, no B-lactams (as no cell wall)
Complications: Haemolytic anaemia, Guillian Barre, erythema multiforme (red centre, dark ring around)
Legionella pneumophilia
Acquired by inhalation of aerosoloized water e.g. showers, AC (on holiday)
Sx: 1-2 days mild then high fever, rigors, confusion, hyponatraemia, pleural effusion
Legionaaires disease: rapidly progressing, fever, resp distress, confusion
Ix: Sputum culture: gram -ve coccobacillii Serology Urinary legionella antigen CXR: multi-lobar SIADH, LFTS
Tx: Clary
Severity Assessment:
q-SOFA (assess for sepsis)
CURB-65(confusion, urea>7, RR>30, BP<90/60, >65) (more than 2=severe)
or
Hypoxia on room air OR multi-lobar consolidation CXR = severe
<2 = oral amox
>3 OR CAP+sepsis = IV Amox + IV Clarythromycin
HAP
Pneumonia acquired >48 hrs admission
Usually staph.aureus, gram -ve e.g. enterobacteria, pseudomonas
Tx: >5 days admission: IV doxy, CURB >3: IV Amox + IV Gent
Complications:
Parapnuemonic effusion (bacteria in pleural fluid)
Empyema (pus in pleural space)
Ix: pleural aspirate, chest drain, IV abx
Viral Resp infections
Common cold
Rhinovirus
Pharyngitis
Adenovirus, EBV, HSV,
Group A streptococcus
Viral - nasal symptoms
Bacterial - non nasal symptoms, abrupt onset, no cough white spots tonsils
Croup Resp illness of larynx and trachea characterised by cough, hoarseness, stridor. Children. Parainfluenza virus DDx: epiglottitis Sx: seal-like cough, stridor at night Tx: IV dexamethasone single dose
Bronchiolitis
Acute viral LRTI characterised by acute onset wheeze, cough, SOB
Cause: RSV (resp. syncytial virus)
Tx: O2 >92%, Ribavirin
Palivizumab prophylaxis
Influenza
Most common cause resp. infection.
Acute resp infection caused by influenza A-C
Sx: high fever, headache, cough, runny nose
Common complications: otitis media, sinusitis
Uncommon complications: Reye syndrome, Encephalopathy
Ix: Clinical diagnosis, viral culture (nasopharyngeal swab, sputum), CXR (exclude bacteria pneumonia)
Tx: Oseltamivir (neuraminidase inhibitor), paracetamol
Pyrexia of unknown origin
> 38 over 3 days in hospital, 3 outpatient visits with no obvious source despite 1 weeks investigation in hospital
Causes:
Infection - abscess, UTI
Malignancy - lymphoma
SLE, RA
Risk fx: surgery, immobility, drugs (chemo)
Ix: Bloods, HIV, malaria, TB, blood/sputum cultures, CXR,
Echo (infective endocarditis),
Evaluation:
Travel history, contacts with people who are ill, Work environment, exposure to animals, PMH, drug history
Tx: emperical abx for neutropenic sepsis, immunocompromised
Suspected giant cell arteritis (corticosteroids)
Otitis Media
Infection of middle ear
Accumulation of middle ear secretions leads to environment for bacterial infection
Causes: S.pneumoniae
Sx: fluid in middle ear, fever, hearing loss
Tx: self-limiting, amoxicillin (after 72 hrs)
Cellulitis
Infection of dermis
- Bacteria gains entry of dermal and subcutaenous tissues due to disruption of cutaneous barrier
Causes: Group A Strep pyogenes, Staph.aureus
Risk fx: venous insufficiency, ulcer/wound
Sx: painful, red with indistinct borders, swollen, lower limb
Ix: FBC (raised WBCs), purulent discharge culture, skin biopsy, US (abscess)
DDx: Nec fas, DVT, Gout
Enron Classification
I. Systemically well
II. Systemically unwell which may delay resolution
III. Systemically unwell or comorbidities which may change response to treatment or limb threatening vascular compromise
IV. Septic, life threatening
Tx: Oral flucox (Enrono I) IV flucox (Enron II) IV Ceftrixone (Enron III) Enron III/IV - surgical consideration MRSA+ve - Vanc Penicllin allergy: Clary
Bite injuries - Co-amox
C.diff infection
Gram +ve bacillus (anaerobe)
Produces enterotoxins A and B leading to colitis (inflammation), and formation of pseudomembranes. Due to normal gut flora disrupted due to antibiotic use.
Sx: watery diarrhoea, fulminant (sudden, severe) colitis
Causes: Co-amox, cephalosporins (ceftriaxone), clindamycin Ix: FBC Stool PCR Stool immunoassay toxins A and B Abdo XR: colonic dilation, air in bowel Sigmoidoscopy: psuedomembrane formation
Severity: Colonic dilation: >6cm WCC >15 Creatinine > 1.5x baseline Immunosuppressed Temp >38.5
Tx: oral metronidazole
Severe: oral vanc
Causative abx stopped, isolate within 2hrs, healthcare staff use PPE, handwashing
Meningitis
Bacterial: N.meningitidis, Pneumococcal/S. pneumoniae, H. influenzae
Viral: Enterovirus, HSV, VZV,
Fungal: Cryptococcosis
Protozoan: Toxoplasmosis
Neonates: Group B Strep (Strep. agalactiae), E.coli Young adult: H.influenzae Adults: N.meningitidis Elderly: S. pneunominae Immunocompromised: Listeria monocytoenes
Acute: bacterial, viral
Sub-acute: Listeria, TB
Sx: Neck stiffness, headache, fever, vomiting,
reduced GCS, rash (macular then peticheal - meningococcal)
Pneumococcal:
Seizures, cranial nerve palsies
Ix:
Blood cultures
Throat culture
LP (cell count, gram stain, culture, PCR)
CT before LP if: GCS<12, papilloedema, immunocompromised, seizures
LP:
Bacterial: Neutrophils, Protein Raised, Glucose <50%,
Viral: Lymphocytes, Protein Raised, Glucose normal
Tx: IV Ceftriaxone
If BM suspected ADD IV dexamethasone
If Listeria IV Amox (21 days)
Viral meningitis
Enterovirus, HSV-2
- No confusion
Tx: Aciclovir if immunocompromised
Viral Encephalitis
Sx: confusion, seizures, fever
HSV-1
IV Aciclovir
TB meningitis
M. tuberculosis
Sx: gradual onset, cranial nerve palsies (III, IV, VI), hemiplegia
HSV infections
HSV 1 : cold sore at lip (herpes labialis)
HSV 2: genital herpes
HSV-3: VZV
HSV-4: EBV
HSV-5: CMV
HSV-6: Roseola infantum (febrile without rash) - most common cause of hospital visits in infants
HSV-8: Kapsoi’s sarcoma
Cutaneous manifestations of HSV:
Herpes gladiatorum - rash on chest, neck, legs - wrestlers,rugby players
Herpetic Whitlow - infection on finger
Tx: Aciclovir
VZV:
Transmitted by resp droplets. 14-21d incubation.
Sx: fever, malaise, rash (itchy, crusts in 48hrs, infectious 1/2 day pre- and 5 day post (when scabbed)
Complications: encephalitis
Shingles: dermatomal reactivation of dormant virus in sensory nerve roots. Sx: painful, rash in dermatomal distribution.
Complications: Ramsay Hunt Syndrome (VZV reactivating in facial nerve: ipsilateral facial palsy, tinnitus)
Tx: oral aciclovir
EBV: Targets B lymphocytes and squamous epithelial cells of oropharynx
Sx: infectious mono in adults: sore throat, fever, lymphadenopathy (post. triangle of neck), palatal petichiae, splenomegaly, hepatomegaly, jaundice
Ix: Monospot test: non-EBV heterophile antibody
Blood film: atypical lymphocytes |
Tx: supportive. NO Amoxicillin - causes macuclopapular rash
MRSA
Resistant to all B-lactams due to mecA gene which encodes for a low affinity penicillin binding protein
Tx: Vanc, Teicoplanin
STIs
Gonorrhoea
Nisseria gonorrhoea - gram -ve diplococcus
Sx: men: urethral discharge, dysuria
women: vaginal discharge, pelvic pain
Ix: NAAT (nucleic acid amplification) test - male urine, female vulvovaginal swab
Culture (urethral, cervical, rectal)
Tx: IM Ceft + Oral azithromycin
Complications: PID, infertility, epididymitis, prostatitis, disseminated gonorrhoea - arthritis, rashes
Chlamydia Trachomatis Sx: Aysmptomatic Complications: PID, infertility Tx: Doxy or azithromycin Lymphogranuloma venereum - painless ucler, proctitis causing constipation, rectal bleeding, inguinal bubos (painful)
Syphillis Triponema pallidum Sx: primary: painless ulcer (chancre) - seconary: rash, fever - tertiary: gumma (non-cancerous growth), neurological - ataxia, seizures Ix: serology Tx: IM benzypenicillin
Chancroid
Haemophilus ducreyi
Painful genital ulcer. Unilateral inguinal lymphadenoapthy
Viral STIs:
HPV (6,11 most common) (HPV 16,18: cervical cancer)
Ano-genital warts
Tx: topical imiquimod, cryotherapy
HSV:
Sx: flu-like. Papules around genitals, anus which form painful vesicles. Bilateral inguinal lymphadenopathy.
Tx: aciclovir
Molloscum contaginosum Pox virus Pearl-like smooth papules on groin If on face - indicates immunosuppressed Self limiting
Pelvic inflammatory disease N. gonorrhoea, C.trachomatis Sx: lower abdo pain, vaginal discharge, fever, cervical/uterine tenderness Ix: Vaginal discharge microscopy Laparoscopy Tx: IM Ceftriaxone + oral doxy
Bacterial vaginosis Gardenerella vaginisis Sx: fishy, thin, white discharge Ix: gram stain Clue cells, pH >4.5 Not STI but can increase risk Tx: Oral/topical Metronidazole
Trichomonas vaginosis vaginal discharge, itch Ix: NAAT Tx: metranidazole Complications: increased risk of pre-term delivery
Candidiasis
Cottage cheese discharge, itch, burning
Tx: azoles
Fever from traveler
Short incubation <10d: Dengue, gastroenteritis
Med inc (10d-21d): Malaria, HIV, eneteric fever, Q fever
Long (>21d): Malaria, HIV, TB, viral hepatitis
Ix: Thick and thin blood film, HIV test, FBC (decreased lymphocytes - viral, eosinophilia - parasites), blood cultures
Dengue Fever
Day biting Aedes mosquito
Can lead to haemorrhagic fever - form of DIC
Sx: incubation 3-14d, high grade fever, retro-orbital pain
Severe: shock, organ involvement (transaminases >1000)
Ix: LFTs (raised transaminase), raised platelets
Tx: supportive. IV crystalloids severe.
Enteric fever
Salmonella typhi/paratyphi
Transmitted: faecal-oral
Sx: headache, arthalgia, fever, relative bradycardia (compared to degree of fever), constipation, rose spots
Complications: Osteomyelitis (esp. in sickle cell), meningitis
Tx: IV azithromycin
TB
Mycobacterium tuberculosis
Sx: cough, lowe-grade, fever, night sweats, weight loss
Clubbing, erythema nodosum, painless cervical lymphadenopathy
Miliary TB: haematogenous dissemination leads to foci of granulotamous tissue throughout lung
CNS TB: haematogenous spread leading to foci of infection to brain or SC. Foci can form tuberculomas (ring enhancing on MRI) and rupture leads to meningitis
Active infection - occurs when containment by immune system isn’t enougn. From primary or reactivation of latent infection. Transmission via inhalation of aerosol droplets
Latent TB - infection without disease due to containment via immune system (granuloma formed prevents bacteria grwoth/spread). Aysmptomatic and non-infectious.
Risk fx reactivation: HIV, immunosuppressants (inc. corticosteroids), organ transplant
Ix: Latent Mantoux test (tuberculin skins test) Interferon gamma assay Active: CXR - linear opacities in upper lobe Sputum smear - acid fast bacilli Sputum culture NAAT test - M. tuberculosis
Tx: RIPE (4 for 2, 2 for 4) all drugs for 2 mnths, first 2 drugs for 4 mnths
Rifampicin
CYP inducer
Orange bodily fluids
Isoniazid
Peripheral neuropathy
Pyridoxine added (vit B6)
Pyrazinamide
Gout, hepatitis
Ethambutol
Optic neuritis, visual acuity needs to be checked before
Lyme disease
Burrelia Burgdoferi (spread by ticks)
Sx: erythema migrans (bulls eye rash), fever, arthalgia
Ix: clinical diagnosis is erythema migrans present
ELISA to antibodies burrelia burgdorferi
Tx: Doxy
