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Old Y3 Sofia Notes > Infection > Flashcards

Infection Flashcards

1
Q

Define Abscess

A

A painful collection of pus, usually caused by bacterial infection

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2
Q

Explain the aetiology/risk factors of abscess

A
  • They can develop anywhere in the body
  • There are TWO main types of abscess:Skin abscess ; Internal abscess
  • Bacterial infection leads to activation of an immune response and recruitment of neutrophils to the site of infection
  • As the white cells attack the bacteria, surrounding tissue is damaged creating a cavity which fills with pus to form an abscess
  • Pus = mixture of dead tissue + white cells + bacteria
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3
Q

Summarise the epidemiology of abscesses

A
  • Skin abscesses are relatively common
  • IV drug use is a major risk factor for skin abscesses
  • Internal abscesses are less common
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4
Q

Recognise the presenting symptoms and signs of abscesses

A
  • Swollen, pus-filled lump under the surface of theskin with associated fever and chills
  • Internal abscesses are not visible but are characterised by:Pain in the affected area (or referred pain);swinging fevers; malaise
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5
Q

Identify appropriate investigations for abscesses

A

•Ultrasound -can be useful in visualising an abscess

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6
Q

Generate a management plan for abscesses

A
  • Some small skin abscesses may disappear by themselves
  • Incision and Drainage; Before doing this, check to see whether a foreign object is causing the abscess (e.g. needle fragments in IV drug users) ; The abscess is cut open and drained of pus
  • Antibiotics; Can be used alongside incision and drainage
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7
Q

Identify possible complications of abscesses

A

Recurrence

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8
Q

Summarise the prognosis for patients with abscesses

A

GOOD with treatment

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9
Q

Define candidiasis

A

Infection caused by Candida.

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10
Q

Explain the aetiology/risk factors of candidiasis

A
  • Caused by 15 different Candida species
  • Candida albicansis the MOST COMMON cause of candidiasis in humans
  • Main types of candidiasis:Oral candidiasis; Oesophageal candidiasis; Candidal vulvovaginitis; Candidal skin infections; Invasive candidal infections •Risk Factors: Broad-spectrum antibiotics ; Immunocompromise (e.g. HIV, corticosteroids); Central venous lines; Cushing’s disease; Diabetes mellitus; GI tract surgery
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11
Q

Summarise the epidemiology of candidiasis

A

•60% of the healthy adult population are carriers
•Candidiasis occurs in over 80% of people with HIV
•Candida is one of the most common causes of invasive fungal infections in the
Western world

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12
Q

Recognise the presenting symptoms and signs of candidiasis

A
  • Oral Candidiasis: Oral Thrush (pseudomembranous oral candidiasis) - curd-like white patches in the mouth, which can be removed easily revealing an underlying red base. Most common in neonates
    o There are lots of subtypes of oral candidiasis with slightly different features but the main features are: redness of the tongue and mouth, white plaques
  • Oesophageal Candidiasis

o Dysphagia
o Pain on swallowing food or fluids
o It is an AIDS-defining illness

  • Candidal Skin Infections

o Soreness and itching
o Skin appearance can be variable
o Red, moist skin area with ragged, peeling edge and possibly papules and pustule

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13
Q

Identify appropriate investigations for candidiasis

A

Oral Candidiasis - swabs and cultures are not particularly useful because a lot of normal people have candida in their mouth

  • Swabs may be relevant to check for drug-resistance
  • Therapeutic trials of antifungal (e.g. fluconazole) can help with diagnosis
  • Oesophageal Candidiasis: definitive diagnosis is by endoscopy
  • Invasive Candidiasis: blood cultures required if candidaemia is possible
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14
Q

Define cellulitis

A
  • Acute non-purulent spreading infection of the subcutaneous tissue, causing overlying skin inflammation
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15
Q

Explain the aetiology/risk factors of cellulitis

A 
* Often results from: 
o Penetrating injury 
o Local lesions (e.g. insect bits) 
o Fissuring (e.g. anal fissures) 
* These allow pathogenic bacteria to enter the skin 
* Most common organisms 
o Streptococcus pyogenes 
o Staphylococcus aureus 
o NOTE: beware of MRSA 
* Cellulitis of the orbit (orbital cellulitis) is usually caused by Haemophilus influenzae 
* Risk Factors 
o Skin break 
o Poor hygiene 
o Poor vascularisation of tissue (e.g. due to diabetes mellitus)
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16
Q

Summarise the epidemiology of cellulitis

A

VERY COMMON

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17
Q

Recognise the presenting symptoms of cellulitis

A
  • History of cut, scratch or injury
  • Periorbital Cellulitis - painful swollen red skin around the eye
  • Orbital Cellulitis - painful or limited eye movements, visual impairment
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18
Q

Recognise the signs of cellulitis on physical examination

A 
* Lesion 
o Erythema 
o Oedema 
o Warm tender indistinct margins 
o Pyrexia - may suggest systemic spread 
* NOTE: exclude the presence of an abscess (aspirate if pus suspected) 
* Periorbital 
o Swollen eye lids 
o Conjunctival infection 
* Orbital Cellulitis 
o Proptosis 
o Impaired visual acuity and eye movements 
o Test for RAPD , visual acuity and colour vision
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19
Q

Identify appropriate investigations for cellulitis

A
  • Bloods - WCC, blood culture
  • Discharge - sample and send for MC&S
  • Aspiration (if pus is suspected)
  • CT/MRI - if orbital cellulitis is suspected (helps assess posterior spread of infection)
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20
Q

Generate a management plan for cellulitis

A
  • Medical
    o Oral penicillins (e.g. flucloxacillin) or tetracyclines are effective
    o If hospital-acquired - treat empirically based on local guidelines and change depending on the sensitivity of cultured organisms
  • Surgical
    o Orbital decompression may be needed in orbital cellulitis (EMERGENCY)
  • Abscess
    o Aspirate
    o Incision and drainage
    o Excised completely
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21
Q

Identify possible complications of cellulitis

A
  • Sloughing of overlying skin
  • Orbital cellulitis - may cause permanent loss of vision, spread to the brain, abscess formation, meningitis, cavernous sinus thrombosis
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22
Q

Summarise the prognosis for patients with cellulitis

A
  • Good prognosis
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23
Q

Define herpes simplex

A
  • Disease resulting from HSV1 or HSV2 infection
24
Q

Explain the aetiology/risk factors of herpes simplex

A
  • Transmitted via close contact (e.g. kissing, sexual intercourse) with an individual that is shedding the virus
  • Pathophysiology
    o After primary infection, the virus will become dormant (within nerve ganglia)
    o Reactivation may occur in response to physical and emotional stresses or immunosuppression
    o The virus causes cytolysis of infected epithelial cells leading to vesicle formation
25
Q

Summarise the epidemiology of herpes simplex

A
  • 90% of adults are seropositive for HSV1 by 30 yrs
  • 35% of adults > 60 yrs are seropositive for HSV2
  • More than 1/3 of the world population have recurrent HSV infections
26
Q

Recognise the presenting symptoms of herpes simplex

A
  • HSV1 - primary infection is often asymptomatic
  • Possible symptoms of primary HSV1 infection:
    o Pharyngitis
    o Gingivostomatitis (eating might be painful)
    o Herpetic whitlow (abscess at the end of the finger caused by infection with HSV - it is very painful)
  • Symptoms of reactivation of HSV1:

o Prodrome of perioral tingling and burning
o Vesicles appear - they will ulcerate and crust over
o Complete healing within 8-10 days
* Symptoms of HSV2:
o Painful blisters and rash in the genital, perigenital and anal area
o Dysuria
o Fever
o Malaise
* Symptoms of HSV encephalitis:
o Usually caused by HSV1 so causes HSV1 type symptoms
* Symptoms of HSV keratoconjunctivitis
o Watering eyes
o Photophobia

27
Q

Recognise the signs of herpes simplex on physical examination

A
  • HSV1 Primary Infection
    o Tender cervical lymphadenopathy
    o Erythematous, oedematous pharynx
    o Oral ulcers filled with yellow slough (gingivostomatitis)
o Herpetic whitlow 
* Herpes Labialis (reactivation affecting the mouth) 
o Perioral vesicles/ulcers/crusting 
* HSV2 
o Maculopapular rash 
o Vesicles 
o Ulcers 
o All of these are found on the external genitalia, anal margin and upper thighs 
o Others: inguinal lymphadenopathy, pyrexia 
* HSV2 Encephalitis 
o Signs of encephalitis 
* HSV Keratoconjunctivitis

o Dendritic ulcer on the iris (better visualised with fluorescein)

28
Q

Identify appropriate investigations for herpes simplex

A
  • Diagnosis is usually CLINICAL

* Vesicle fluid can be sampled and sent for electron microscopy, PCR

29
Q

Define HIV

A
  • Infection with the human immunodeficiency virus (HIV)
30
Q

Explain the aetiology/risk factors of HIV

A
  • HIV is transmitted by:
    o Sexual intercourse
  • Heterosexual intercourse is the MOST COMMON mode of transmission
  • Homosexuals are at greater risk in the West
    o Blood (and other bodily fluids)
  • Mother to child (intrauterine, childbirth, breastfeeding)
  • Needles
  • Blood transfusions
  • Organ transplantation
  • Pathophysiology

o HIV enters CD4+ lymphocytes by binding to their gp120 receptors
o Reverse transcriptase allows the incorporation of HIV genetic material into the host genome
o This leads to dissemination of HIV, cell death and eventual T-cell depletion

31
Q

Summarise the epidemiology of HIV

A
  • Increasing in incidence in Africa and Asia
32
Q

Recognise the signs and presenting symptoms of HIV

A
  • There are THREE phases of HIV:
    o Seroconversion
  • Self-limiting
  • Fever
  • Night sweats
  • Generalised lymphadenopathy
  • Sore throat
  • Others: oral ulcers, rash, myalgia, headache, encephalitis, diarrhoea
    o Early/Asymptomatic
  • Apparently well
  • Some may have persistent lymphadenopathy
  • Progressive minor symptoms (e.g. rash, oral thrush, weight loss)
    o AIDS
  • Syndrome of secondary diseases resulting from immunodeficiency
  • Direct Effects of HIV Infection
    o Neurological: polyneuropathy, dementia
    o Lung: lymphocytic interstitial pneumonitis
    o Heart: cardiomyopathy, myocarditis
    o Haematological: anaemia, thrombocytopaenia
    o GI: anorexia, wasting
    o Eyes: cotton wool spots
  • Secondary effects resulting from immunodeficiency
    o Bacterial Infection: TB, skin infections, pneumococcal infections
    o Viral: CMV, HSV, VZV, HPV, EBV
    o Fungal: pneumocystic jirovecii pneumonia, Cryptococcus, candidiasis, invasive aspergillosis
    o Protozoal: toxoplasmosis, cryptosporidia
    o Tumours: Kaposi sarcoma, SCC, non-Hogkin’s lymphoma, Hodgkin’s lymphoma
33
Q

Identify appropriate investigations for HIV

A
  • HIV testing - HIV antibodies, PCR for viral RNA, CD4 count, viral load
  • Others
    o Pneumocystic pneumonia - CXR
    o Cryptococcal meningitis - brain CT or MRI, LP
    o CMV (colitis) - colonoscopy and biopsy
    o Toxoplasmosis - brain CT or MRI
    o Cryptosporidia - stool microscopy
34
Q

Define infectious mononucleosis

A
  • Clinical syndrome caused by primary EBV infection

o AKA glandular fever

35
Q

Explain the aetiology/risk factors of infectious mononucleosis

A
  • EBV is a gamma-Herpes virus (dsDNA)
  • It is found in the pharyngeal secretions of infected individuals and is transmitted by close contact (e.g. kissing, sharing eating utensils)
  • EBV infection of the epithelial cells of the oropharynx leads to B cell infection
  • The infected B cells disseminate EBV across the body leading to a humoral and cellular immune response
  • Atypical lymphocytes in the peripheral blood are a classic feature of infectious mononucleosis
  • EBV remains latent in lymphocytes
  • Reactivation may occur following stress or immunosuppression
36
Q

Summarise the epidemiology of infectious mononucleosis

A
  • COMMON
  • TWO age peaks:
    o 1-6 yrs
    o 14-20 yrs
37
Q

Recognise the presenting symptoms of infectious mononucleosis

A
  • Incubation period: 4-8 weeks
  • Abrupt onset of symptoms:
    o Sore throat
    o Fever
    o Fatigue
    o Headache
    o Malaise
    o Anorexia
    o Sweating
    o Abdominal pain
38
Q

Recognise the signs of infectious mononucleosis on physical examination

A
  • PYREXIA
  • Oedema and erythema of the pharynx
  • White/creamy exudate on the tonsils
  • Palatal petechiae
  • Cervical/generalised lymphadenopathy
  • Splenomegaly
  • Hepatomegaly
  • Jaundice (5-10%)
  • Widespread maculopapular rash (in patients who have received ampicillin)
39
Q

Identify appropriate investigations for infectious mononucleosis

A
  • Bloods
    o FBC - leucocytosis
    o LFTs - high AST/ALT
  • Blood Film - lymphocytosis with atypical lymphocytes
  • Heterophil Antibody Test (aka Monospot Test, Paul Bunnell Test)
    o Based on EBV antigens being similar to antigens on RBCs of many animals but NOT humans
    o Mixing blood of an EBV-positive human with animal blood will make the animal’s red cells aggregate and precipitate out of solution
    o May give false-negatives in the early stages of infection before antibodies are generated
  • Throat swabs - exclude streptococcal tonsillitis
  • IgM or IgG to EBV viral capsid antigen
  • IgG against Epstein-Barr nuclear antigen (EBNA)
40
Q

Generate a management plan for infectious mononucleosis

A
  • Bed rest
  • Paracetamol and NSAIDs - helps with fever, malaise
  • Corticosteroids in SEVERE cases
  • IMPORTANT: do NOT give AMPICILLIN or AMOXICILLIN if infectious mononucleosis is suspected - nearly 100% of patients with glandular fever develop a maculopapular rash
  • Advice - avoid contact sports for 2 weeks (because of risk of rupturing your spleen)
41
Q

Identify possible complications of infectious mononucleosis

A
  • Lethargy for several months
  • Respiratory - airway obstruction from oedematous pharynx, secondary bacterial throat infection, pneumonitis
  • Haematological - haemolytic or aplastic anaemia, thrombocytopenia
  • GI/Renal - splenic rupture, fulminant hepatitis, pancreatitis, mesenteric adenitis, renal failure
  • CNS - Guillain-Barre syndrome, encephalitis, viral meningitis
  • EBV-associated malignancy - Burkitt’s lymphoma (in sub-Saharan Africa), nasopharyngeal cancer, Hodgkin’s lymphoma

Summarise the prognosis for patients with infectious mononucleosis

  • Most make uncomplicated recovery (within 3 weeks)
  • Immunodeficiency and death are VERY RARE
42
Q

Define malaria

A
  • Infection with protozoan Plasmodium
  • FIVE types of Plasmodium:
    o Plasmodium falciparum - MOST SERIOUS
    o Plasmodium vivax
    o Plasmodium ovale
    o Plasmodium malariae
    o Plasmodium knowlesi
43
Q

Explain the aetiology/risk factors of malaria

A
  • Transmitted by the bite of the female Anopheles mosquito
  • The protozoa grow in red blood cells
  • Life Cycle

o Injection of sporozoites into the blood stream by mosquito
o Invasion and replication in hepatocytes
o Parasites reinvade the blood and enter red blood cells
o They replicate within red blood cells and develop ring forms
o Red blood cells rupture and release merozoites, which reinfect other red blood cells
o Gametocytes are taken up when another mosquito feeds, and develop into sporozoites in the gut of the mosquito
o They then move to the salivary gland of the mosquito to be transmitted with the next bite
* Some populations have innate immunity to malaria:
o Sickle cell trait
o G6PD deficiency
o Pyruvate kinase deficiency
o Thalassemia

44
Q

Summarise the epidemiology of malaria

A
  • Endemic in the tropics

* 250 million people worldwide

45
Q

Recognise the presenting symptoms of malaria

A
  • Feverish traveller (incubation period can be up to 1 year)
  • Symptoms are CYCLICAL:
    o High fever
    o Flu-like symptoms
    o Severe sweating
    o Shivering cold/rigors
  • NOTE: the interval between cycles of symptoms are slightly different in different types of malaria
  • Cerebral Malaria Symptoms:
    o Headache
    o Disorientation
    o Coma
46
Q

Recognise the signs of malaria on physical examination

A
  • Pyrexia
  • Anaemia (haemolytic)
  • Hepatosplenomegaly
47
Q

Identify appropriate investigations for malaria

A
  • Thick/Thin Blood Films
    o Thick for quantifying
    o Thin for identifying type of malaria
* Bloods 
o FBC - haemolytic picture 
o U&Es 
o LFTs 
o ABG 
* Urinalysis -check for blood or protein
48
Q

Define varicella zoster

A
  • Primary infection is called varicella (chickenpox). Reactivation of the dormant virus (found in dorsal root ganglia), causes zoster (shingles).
    o NOTE: varicella zoster is also known as herpes zoster
49
Q

Explain the aetiology/risk factors of varicella zoster

A
  • VZV is a herpes ds-DNA virus
  • Highly contagious
  • Transmission by aerosol inhalation or direct contact with vesicular secretions
50
Q

Summarise the epidemiology of varicella zoster

A
  • Chicken pox peak incidence: 4-10 yrs
  • Shingles peak incidence: > 50 yrs
  • 90% of adults are VZV IgG positive
51
Q

Recognise the presenting symptoms of varicella zoster

A
  • Chickenpox

o Prodromal malaise
o Mild pyrexia
o Sudden appearance of intensely itchy spreading rash mainly affecting face and trunk
o Vesicles weep and crust over
o New vesicles appear
o Contagious from 48 hrs before the rash until after the vesicles have all crusted over (7-10 days)
* Shingles

o May occur after a period of stress
o Tingling/hyperaesthesia in a dermatomal distribution
* Dermatomal because the rash remains dormant in the dorsal root ganglia and reactivation makes the virus travel down the sensory axon to produce a dermatomal shingles rash
o Painful skin lesions
o Recovery: 10-14 days

52
Q

Recognise the signs of varicella zoster on physical examination

A 
* Chickenpox 
o Maculopapular rash 
o Areas of weeping and crusting 
o Skin excoriation (from scratching) 
o Mild pyrexia 
* Shingles 
o Vesicular maculopapular rash 
o Dermatomal distribution 
o Skin excoriation
53
Q

Identify appropriate investigations for varicella zoster

A
  • Usually CLINICAL diagnoses
  • Vesicle fluid may be sent for electron microscopy viral PCR (RARELY necessary)
  • Chicken pox in an adult with previous history of varicella infection may require HIV testing
54
Q

Generate a management plan for varicella zoster

A 
* Chickenpox 
o Children - treat symptoms 
o Adults - consider aciclovir 
* Shingles 
o Aciclovir, valaciclovir, famciclovir 
* Prevention 
o Varicella Zoster Ig (VZIG) - may be considered in immunosuppressed or pregnant
55
Q

Identify possible complications of varicella zoster

A 
* Chickenpox 
o Secondary infection 
o Scarring 
o Pneumonia 
o Encephalitis 
o Congenital varicella syndrome 
* Shingles 
o Postherpetic neuralgia 
o Zoster ophthalmicus (rash in the ophthalmic division of the trigeminal nerve)

o Ramsay-Hunt syndrome

  • DEFINITION: reactivation of VZV in the geniculate ganglion causing zoster of the ear and facial nerve palsy. Vesicles may be seen behind the pinna of the ear or in the ear canal
    o Sacral zoster
    o Motor zoster
56
Q

Summarise the prognosis for patients with varicella zoster

A
  • Depends on complications

* Worse in pregnancy, elderly and immunocompromised

Old Y3 Sofia Notes (9 decks)

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