Infection Flashcards
What is pyrexia of unknown origin (PUO)?
PUO is a documented fever persisting for >2 weeks, with no clear diagnosis.
Occult infection is the commonest cause of PUO in adults
Causes include infection, malignancy, vasculitides and drugs, IBD, sarcoidosis, thyrotoxicosis.
What is bacteraemia?
Transient presence of organisms in the blood. Usually causes no symptoms
What is septicaemia?
Clinical picture that results from systemic inflammatory response (SIR) to infection
Inflammation is intended to be a local contained response to infection. In some causes, this goes outwith the boundaries of the local environment so the inflammatory process becomes systemic instead of remaining localised.
Clinical features include:
- fever
- tachycardia
- increased respiratory rate
- hypotension
High mortality rate if untreated
What is the common causative microorganism in biliary tree infection?
Enterococcus faecalis, or E.oli (Gram -ve)
What are the two big microorganisms that cause infection in IVDU?
Staph. Aureus
Pseudomonas
What is toxic shock syndrome? (TSS)
This is caused by staphylococci. These bacteria produce an exotoxin. TSS is characterised by an abrupt onset of fever, rash, diarrhoea and shock.
Associated typically with tampon users, but can occur in anyone including children
What is Waterhouse-Friderichsen syndrome?
Usually caused by Neisseria meningitidis. Rapidly datal illness if untreated. Causes purpuric skin rash and shock. Adrenal haemorrhage (and subsequent hypoadrenalism) may occur.
What are the features, complications and management of measles?
Measles is caused by an RNA paramyxovirus. Spread by droplet.
Period of infectivity is 4 days before and after rash, after which they can return to work/school.
Two stages:
1) Pre-eruptive and catarrhal stage: fever, cough, rhinorrhoea, conjunctivitis and pathogonomic Koplik’s spots (grey spots on buccal mucosa).
2) Eruptive stage: maculopapular rash starts on face, spreads to whole body. Fades after a week.
Complications:
- Gastroenteritis
- Otitis media
- Encephalitis
- Myocarditis
Pregnant ladies need not worry about congenital malformations but there is increased risk of miscarriage as with most infections.
Rarely the virus reactivated before puberty and causes panencephalitis with mental problems and death
Management
Symptomatic.
UK - All kids given MMR vaccine (measles mumps rubella)
What are the features of mumps and its management?
Mumps is caused by paramyxovirus. Spread by droplets. (Same as measles)
Features: Primarily school aged children and young adults.
- Fever
- Headache
- Malaise
- PAROTID SWELLING
- (orchitis, meningitis, pancreatitis, oophoritis, myocarditis, hepatitis)
Management:
Symptomatic treatment.
Children can return to school 5 days after ONSET of swelling.
What are the features and management of Rubella?
Also called ‘german measles’, this is caused by an RNA virus. Peak age of 15 years. Incubation period 2-3 weeks.
Prodrome of malaise, fever, lymphadenopathy.
The pinkish rash on face and trunk after about a week, lasting for 3 days.
Clinical diagnosis but antibodies can be measured
Management:
Symptomatic.
Return to school 6 days after onset of rash
Complications - arthralgia, encephalitis, thrombocytopenia
Congenital rubella syndrome:
Maternal infection during pregnancy may affect the fetus if infection during first trimester when the fetus is most vulnerable:
- heart defects
- cataracts
- microcephaly
- mental handicap
- deafness
(DUMB HEARTLESS BLIND BABY)
What are the three herpes viruses?
Herpes Simplex Virus (HSV)
Varicella zoster virus (chicken pox virus and shingles)
What are the features and management of HSV?
HSV1:
- Herpetic stomatitis with buccal ulceration, fever and local lymphadenopathy
- Herpetic whitlow: damage to skin over a finger allows access of the virus, allowing irritating vesicles to form (i.e. if you touch sore area of skin allowing virus to enter the cut)
- Keratoconjuncivitis (inflammation of both conjunctiva and cornea)
- Acute encephalitis
- Disseminated infection in the immunocompromised
HSV2:
- Transmitted sexually
- Genital ulcers (can also occur in HSV1)
- Fever
- Lymphadenopathy
- Anorectal infection in homosexuals
- Systemic infection in immunocompromised
Recurrent HSV infections occur when virus lies dormant in ganglion cells and is reactivated by trauma, illness, UVR. This leads to recurrent labialis (cold sores) or recurrent genital herpes.
Diagnosis: clinical but HSV DNA PCR can be done
Management: Oral aciclovir for 5 days - only beneficial if used while ulcers still forming, useless later…
What are the features and management of varicella zoster virus (VZV)
This is the chickenpox virus. It is primary infection with VZV that causes chicken pox, which may produce a mild childhood illness. Note that chicken pox can be very severe in adults and immunocompromised.
Features:
- 2 to 3 weeks incubation
- Prodrome of fever headache malaise
- Rash on face, salp, trunk begins as macules and develops into papules and vesicles, which heal with crusting.
- VERY ITCHY
- Complications include pneumonia and CNS involvement. CNS involvement presents as acute truncal cerebellar ataxia
Diagnosis: clinical but viral DNA PCR can be done
Management: No treatment in healthy children. Over 16 y/o given antiviral therapy with aciclovir is they present within 3 days because risk of severe disease is increased.
If pregnant and exposes to VZV, give zoster immunoglobulin (ZIG) and aciclovir if they do go on to develop chickenpox.
Papule is flat circumscribed alterations in skin color. Papule is a solid, elevated lesion with no visible fluid which may be up to ½
cm. in diameter. Vesicles are circumscribed epidermal elevations in the skin containing clear
fluid and less than ½ cm
What are the features of herpes zoster (shingles)
After VZV primary infection, the virus remains dormant in the dorsal root ganglia/CN ganglia, and if it reactivates, it causes shingles.
A person with shingles (particularly if rash is weeping) can actually cause chickenpox in a non-immune individual after close contact and touch.
Features:
-pain and tingling in a dermatomal distribution precedes the rash by a few days. The rash consists of papules and vesicles in the same dermatome. The commonest sites are the lower thoracic dermatomes and the opthalmic division of the trigeminal nerve (V1)
Management:
Oral aciclovir ASAP. Main complication is post-herpetic neuralgia (PHN) which can be severe and last for years - ridiculous isn’t it! What a pain! - Treat this with carbamazepine or phenytoin (yes it is an anti-epileptic). PHN can be reduced by prompt aciclovir treatment.
What are the features of infectious mononucleosis and Epstein-Barr virus (EBV)?
Infectious mononucleosis (glandular fever) is caused by the EBV and predominantly affects young adults (kissing disease). Transmitted in saliva and aerosol.
Major cause for hairy leukoplakia in patients with AIDS, Burkitt’s lymphoma, nasopharyngeal carcinoma, post-transplant lymphoma and the immunoblastic lymphoma of AIDS patients.
Features:
- Fever
- Headache
- Sore throat
- transient macular rash (usually if given amoxicillin inappropriately thinking it is just a sore throat)
- Cervical lymphadenopathy
- Splenomegaly
- Mild hepatitis
Rare Cx - splenic rupture, myocarditis, meningitis.
REMEMBER THAT CMV, TOXOPLASMOSIS AND ACUTE HIV PRODUCT SIMILAR ILLNESS.
Investigations:
- Atypical lymphocytes on peripheral blood film strongly suggest EBV
- Detection of heterophile antibodies is diagnostic test of choice. ( Heterophile antibodies are antibodies produced against poorly defined antigens)
- Paul bunnell reaction: the antibodies agglutinate sheep red cells (Monospot test for horse red cells)
Management: No treatment. Corticosteroids if neuro involvement, or when there is tonsillar enlargement causing obstruction and if there is severe thrombocytopenia or haemolysis
