Ch 14 - Infection & immunity Flashcards Preview

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Flashcards in Ch 14 - Infection & immunity Deck (69)
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1

Bacterial meningitis: likely organisms in following age groups: neonates- 3 months (3), 1 month - 6 yrs (3), >6 yrs (2)

neonates - 3 months: GBS, listeria, E. coli
1 month - 6 yrs: N. meningitidis, H. influenza, S. pneumoniae
> 6yrs: N. meningitidis, H. influenza

2

Bacterial meningitis: features (8)

Fever, lethargy, poor feeding
Reduced consciousness
Purpuric non-blanching rash
Cushing's triad (ominous sign - reflex response to increased ICP): HTN + altered breathing pattern + bradycardia
Photophobia
Neck stiffness
Kernig/ Brudzinski sign +ve

3

Bacterial meningitis: diagnosis is aided by LP; but when is LP contraindicated? (3)

Raised ICP signs e.g. coma, Cushing triad, papilloedema
Cardiorespiratory instability
focal neurology
Coagulopathy, thrombocytopenia

4

Describe the normal CSF characterstics seen on LP: appearance (1), WBCs (1), Protein (1), Glucose. Then do the same for meningitis: bacterial, viral, TB

Normal: clear, 0-5/mm3, 0.15-0.4 g/L, glucose > 50% of blood
Bacterial: turbid, raised polymorphs, increased protein, reduced glucose
Viral: clear, raised lymphocytes, normal/ slight increase in protein, normal/ slight decrease in glucose
TB: Turbid/viscous, raised lymphocytes, VERY HIGH protein & VERY LOW glucose

5

Management of Meningitis (bacterial) (2)

Febrile child with purpuric rash - dont risk it and give IM Benzylpenicillin + hospital transfer
IV Ceftriaxone

6

Viral meningitis: organisms (3), diagnosis (3)

Much less severe than bacterial & full recovery usual
Organisms: EBV, enterovirus, adenovirus, mumps (now less common due to MMR)
Diagnosis: PCR of CSF, stool cultrue, nasopharyngeal aspirate, throat swabs

7

Encephalitis: causes (4), features (3), management (2)

Causes: direct invasion of cerebrum by neurotoxic virus e.g. HSV, HHV6, post-infectious delayed brain swelling folowing abnormal immune response to an Ag (usually virus) e.g. chicknepox; HIV
Features - clinically cannot distinguish meningitis from encephalitis therefore treat both! Fevers, seizures, altered consciousness
Management - High dose IV acyclovir; HSV encephalitis can be devastating - CT/MRI may show temporal lobes atrophy

8

Toxic shock syndrome: 3 main characteristics, Causes (2), Features (4)

Triad: fever > 39, hypotension, diffuse erythematous macular rash.
Caused by S. Aureus or S. Pyogenes
Toxin can be released from infection at any site and acts as super ag.
Features - mucositis, D & V, renal impairment, liver impairment, clotting abnormalities

9

TSS: management (3)

Transfer to ICU
Surgical debridement of infected tissue
ABs - ceftriaxone & clindamycin (acts on bacterial ribsome to shut off toxin production)
IVIG - neutralize circulating toxin

10

PVL producing S. Aureus: what is the toxin (1), major risk of what (2)

Produces Panton-Valentine Leukocidin which causes recurrent skin + soft tissue infections
but can also cause NEC FASCIITIS & nec haemorrhagic pneumonia following an influenza like illness

11

Necrotizing Fasciitis/ Cellulitis: definition, Causes (2), Features (3), management (2)

Severe subcut infection from skin to fascia and muscle
Causes - PVL producing S. Aureues, S. pyogenes
Features - severe pain, central necrotic tissue, systemic illness
Managent - IVIG, surgical intervention

12

Meningococcal infection - features (3), prevention (1), risk of neuro damage compared to the other meningitis causing organisms

F - purpuric rash, necrotic centre
P - MenA, + Men C vaccine - Men B also available now
Long- term - lowest risk of neuro sequelae out of the 3 main causes of bacterial meningitis

13

Pneumococcal infection - why are young infants particularly at risk? what should be given to high risk infants?

Poor response in infants to encapsulated bacteria (the pneumococcal vaccine has reduced incidence of invasive disease)
Children at increased risk e.g. from hyposplenism should also be given daily prophylactic penicillin

14

Staph/GAS infections: impetigo; defintion, features (4), management (2)

D - localized highly contagious Staph or strep infection
(most common in young children where there is pre-existing skin disease e.g. atopic eczema)
F - lesions start as erythematous macules > become vesicular/ pustular > rupture of vesciles + exudation of fluid leads to characteristic confluent HONEY-COLOURED crusted lesions
M - Topical Abs e.g. Fucidic acid cream, narrow spec abs e.g. flucloxacillin,

15

Staph/GAS infections: Boils

infection of hair follicles/ sweat galnds, usually due to S. Aureus treat with ABs

16

Staph/GAS infections: Periorbital cellulitis - features (3), causes (2), management

D - fever + unilateral eyelid erythema + tenderness + oedema
C - other than strep/staph Hib, local trauma, dental abscess
M - IV abs

17

Staph/GAS infections: Scalded skin syndrome: defintion, features ( 5), management (2)

D - separation of epidermal skin through granular cell layers by exfloiative Staph toxin
F - tender flaccid bullae which rupture to show moist erythematous base, wide spread erythema + skin tenderness. Nikolsky sign - area of epidermis separates on gentle pressure
M - Flucloxacillin, analgesia, fluid balance

18

Staph/GAS infections: Scarlet fever: features ( 5), management (1), complications (3)

Caused by S. pyogenes
F - tonsilitis, fever, head sparing blanching punctate rash, furred tongue with enlarged papillae
M - Penicillin V/ Azithromycin
C - otitis media, post-strep GN, rheumatic fever

19

Human herpes viruses: HSV: type 1 & 2, treatment (1), ginivostomatitis - features (3), skin manifestations (2), eye disease (2), CNS infection (1)

HSV1 - oral/skin, HSV-2 genital
T - Acyclovir (viral DNA polymerase inhibitor)
Gingivostomatitis - most common primary HSV in children, vesicular lesions on lips, gums and tongue > progress to painful ulceration with bleeding + high fever. Child is miserable, resolves in 2 weeks. Treat symptomatically, acyclovir if requried
Eye disease - blepharitis (inflammation of eye lids) or conjunctivitis, can extend to involve cornea and lead to loss of vision
CNS - encephalitis

20

Human herpes viruses: VZV: avg incubation period (1), features (5), complications (4), management (3)

VZV is spread by resp droplets - highly infectious during viral shedding. Avg incubation period of 14 days.
F: start with fever, headache, malaise. 200-500 lesions appear on head & trunk, then progress to peripheries. Starts as papules > vesicles > pustules > crusts
Appear in crops for 3-5 days - if new rashes still forming after 10 days consider T cell defect
C - scar formation/ secondary infection if scratching, encephalitis, TSS, nec fasc. Also purpura fulminans (way more common with mengococcus) occurs due to vasculitis in skin + subcut tissue, due to production of anti-VZV abs which cross react with Protein S - inactivating it > dysregulation of fibrinolysis & increased risk of clotting
M - IV acyclovir, PO valaciclovir, VZIG if immunodeficient

21

Human herpes viruses: VZV - shingles; definition, features (2), recurrent shingles indicative of what?

D - reactivation of latent VZV (uncommon in children)
F - vesicular eruption in dermatomal distribution of sensory nerves - NOT associated with neuralgic pain
Recurrent/ multidermatomal shingles indicates T cell defect

22

Human herpes viruses: EBV: features (5)

EBV (also involved in pathogenesis of burkitt) has particular tropism for B cells and pharyngeal epithelial cells. Transmission is by oral contact, most infections subclinical. But sometimes can get a syndrome with:
F - fever, malaise, cervical lymphadenopathy, tonsillopharyngitis (usually quite severe - limiting oral ingestion), splenomegaly, hepatomegaly, petechiae in soft palate, maculopapular rash

23

Human herpes viruses: EBV diagnosis (3), management (2)

D - atypical lymphocytes on blood film, positive monospot test, anti-EBV IgM & IgG
M - symptomatic, steroids if airway obstruction due to tonsillopharyngitis (rare), dont give amoxicillin because can cause maculopapular rash (should resolve within 1-3 months)

24

Human herpes viruses: CMV; features (4), diagnosis (2), management (3)

CMV usually transmitted by saliva/ genital secretions/ breast milk. Causes mild/ subclin infections in normal hosts. Is imp in immunocompromised and fetus
F - retinitis, colitis, hepatitis, encephalitis, pneumonitis
D - atypical lymphocytes (owls eye inclusions), monospot negative
M - ganciclovir, Foscarnet, Cidofovir

25

Human herpes viruses: HHV 6/7 - Roseola Infantum; features (4)

F - high fever + malaise for few days > generalized macular rash appearing as fever wanes. May have febrile convulsion (commonest cause of febrile convulsions)

26

Human herpes viruses: HHV 8 - associated with what (1)

Kaposi sarcoma in HIV co-infected

27

Parvovirus B19: transmission (3), clinical syndromes (4)

Transmission - resp secretions from viraemic parents, vertical transmission mother to fetus, transfusion of contaminated blood products
B19 infects the erythroblastoid red cell precursors in BM & can cause range of clinical syndromes:
Asymp infection - common
Erythema infectiosum - most common; viraemic phase - fever, malaise, headache myalgia. Week later get 'slapped cheek' rash > progresses to maculopapular 'lace'like rash on trunk & limbs
Aplastic crisis - most serious consequence occurs in haemolytic anaemias (increased RBC turnover) & immunocomprised
Fetal disease - fetal hydrops + death due to anaemia

28

Enteroviruses: generally cause (2), transmission (1)

They are mostly asymp/self-limiting
Usually cause fever and rash on trunk (blanching) + shin petechiae
Transmission is Faecal-oral

29

Enteroviruses: HFMD (coxsackie A16 & enterovirus 71): features (2), management

Painful oral vesicles followed by palms/soles/ buttocks, mild systemic features
manage with fluids and analgesia

30

Enteroviruses: Herpangina (Coxsackie) ; features (4) management

Vesicular ulcerated lesions on soft palate and uvula causing anorexia, dysphagia & fever
manage with fluids and analgesia