Infectious diseases Flashcards
SBA 6
42 year old man
Previous pnemocystic pneumonia and oral ulcers
Presents with purple purpural lesion on nose
Which is the causative organism for this skin lesion?
E HHV8
Kaposi sarcoma
Herpes Simplex Virus
Definition
Types
Epidemiology - How common?
Aetiology and two phases
Presentation- symptoms and signs of HSV1
Presentation - symptoms and signs of HSV2
Investigations
Management
Herpes Simplex Virus
Definition
- Infection of HSV 1 and 2. Infection can be dormant and re inflammation is triggered by physical/emotional stress or immunosuppression.
Epidemiology - How common?
Very common
90% adults seropositive for HSV1 by 30 years
Aetiology
- Primary infection occurs
- Virus becomes dormant in trigeminal and sacral root ganglia
- Reactivates if stress/immunosupression
Two phases
Latent phase: Dormant chronic infection, no infectious virions present= asymptomatic
Lytic phase: Active infections- viral replication and transport to skin
Presentation- symptoms and signs
of HSV1
- Gingivostomatitis, cold sores [herpes labialis]
- Herpetic whitlow [blister on finger]
- Herpes simplex meningitis/encephalitis
- Eczema herpeticum [emergency]
- Keratoconjunctivitis
- Systemic infection
HSV2
- Genital herpes- chronic/life long
- Flu-like prodrome
- Vesicles/papules around genitals/anus
- Urethral discharge
- Shallow ulcers
- Dysuria
- Fever and malaise
Investigations
- Clinical diagnosis
- Viral culture/PCR
Management
- Acyclovir [Topical, oral, IV]
SBA 1
Which organism is the most common cause for herpes labialis?
HSV-1
A 32 year old librarian presents to GP with a history of sharp tingling around his lips followed by a painful ulcer on the side of his mouth. O/E he has cervical lymphadenopathy and a blister on his finger. What is the pathogen?
A.Varicella Zoster Virus
B.Epstein-Barr Virus
C.Herpes Simplex Virus 1
D.Herpes Simplex Virus 2
Cytomegalovirus
C.Herpes Simplex Virus 1
SBA 4
50 year old man
Shingles rash
Which of following is not true?
A.This condition is Shingles
B.May occur due to stress
C.The rash may present bilaterally
D.Tingling in a dermatomal
distribution
E. The rash is painful
C The rash may present bilaterally
Shingles v unlikely to present bilaterally
How do heterophile antibodies form?
EBV can escape lymphatics, go to blood, infect B cells
Don’t contribute to symptoms
Methods of HIV transmission
- placenta, birth, breastfeeding ^ doesn’t happen often anymore - - -
What are the four stages of an untreated HIV infection? Presentation - symptoms and signs of HIV
- [below 200 CD4 T cells- illnesses] HIV only present due to complications/opportunistic infections due to low levels of CD4 T cells
Which disease characteristically causes ring enhancing lesions on CT head?
Toxoplasma gondi
What are the AIDS definining opportunitistic illnesses/pathogens?
What is seen on CXR in pneumocystic pneumonia?
Reticulonodular shadowing
SBA 7
47 y old HIV positive patient presents with:
Weakness of right leg
Headache
Fever
Confusion worsening over last few weeks
CT head shows multiple ring enhancing lesions
What organism is most likely to be causing this?
A.Plasmodium falciparum
B.Neisseria meningitidis
C.Toxoplasma gondii
D.Herpes Simplex Encephalitis
E.Pox virus
C Toxoplasma gondi
SBA 9
Most common causative agent for someone with a runny nose, sneezing and coughing?
A Rhinovirus
B Coronavirus
C Influenza
D Parainfluenza
E Respiratory syncytial virus
A Rhinovirus
SBA 10
37 y old
Lump posterior of neck= hot, erythematous and painful
Most likely causative agent?
A.Streptococcus pyogenes
B.Staphylococcus aureus
C.Mycobacterium Tuberculosis
D.Parasitic infection
E.Pseudomonas Aeruginosa
B Staphlococcus aurerus
[Strep pyogenes also can cause skin lumps but less likely]
What are tumours associated with HIV?
Investigations for HIV? First line Other tests
FIRST line
- ELISA, confirmed with Western blot
- Serum HIV rapid test
- Serum HIV DNA PCR - infants
- CD4 count – indicates immune status, assists staging process
- Serum viral load (HIV RNA) millions of copies/mL
Second line
- Drug resistance test – to determine therapy
- Serum hepatitis B and C serology
- Treponema pallidum haemagglutination test screening for syphilis
- Tuberculin skin test – TB
- FBC, U+E, LFTs
SBA 3
A 6-year old girl presents with a fever of 38.5, fatigue and a maculopapular rash on her face and trunk. Other children at school present with similar symptoms.
How should this patient be managed?
A.Hydration and NSAIDs.
B.Give oral acyclovir
C.Consider oral valaciclovir if within 24 h of rash onset
D.Paracetamol and Calamine lotion
E.Vaccinate with Varicella Immunoglobulin
A.Paracetamol and Calamine lotion
How do you differentiate between viral and bacterial infection causing a sore throat?
Centor criteria??
What is this rash?
Shingles
Varicella zoster
Table of the eight human herpes viruses
A wild medical student presents with sore throat and tonsillar exudates, posterior cervical lymphadenopathy and his basic observations are 38.9oC, HR is 90bpm and oxygen saturation on air is 99%. On examination there is splenomegaly.
His condition is most likely due to which of the following?
A.EBV
B.Streptococcus pyogenes
C.Adenovirus
D.Covid-19
E.Candida
A. EBV
Varicella zoster
Definition
Epidemiology
Presentation
- Chickenpox
- Shingles
Investigations
Management:
- Chickenpox
- Shingles
Prevention
Complications
Varicella zoster
Definition
Infection of varicella zoster
Primary infection=chickenpox
Secondary reactivation in the dorsal root ganglion= shingles/zoster
Epidemiology
Chickenpox= 4-10 years
Shingles >50 years
90% of adults have antibodies
Presentation
- Chickenpox
- Prodromal malaise
- Fever- mild
- Maculopapular vesicular pruritic rash- face and trunk
- Infectious for 48hrs before rash appears and until vesicles have crusted over- 7-10 days usually
- Shingles
- Tingling in a dermatomal distribution
- Unilateral painful rash/skin lesions in dermatomal distribution
- May occur due to stress
- Recovery takes 10-14 days
Investigations
Clinical diagnosis
Consider viral serology and PCR, ELISA [but rare]
Management:
- Chickenpox
- Children
- Paracetamol
- Calamine lotion
- Antihistamines
- Adults
- Acyclovir, valacyclovr, famacyclovir if within 24hr of rash onset
- [There’s a person called val in the fam]
- Shingles
- First line: valacyclovr, famacyclovir
- Second line: acyclovir
- if within 72hr of rash onset
- Give for 7 days
Prevention
Antibodies/vaccine available for:
Pregnant women
Immunocompromised
Complications
Chickenpox
Sepsis
Pneumonia
Encephalitis
Haemorrhagic complications
Shingles
Meningoencephalitis
Myelitis
Cranial nerve palsies
Vasculopathy
Gastrointestinal ulcers
Pancreatitis
Hepatitis
Sepsis
Infectious mononucleosis
Definition
Aetiology
Presentation
Pathogenesis
Investigations
Management
Prognosis
EBV specific antibody
Infectious mononucleosis
Definition
Clinical condition resulting from primary infection with EBV virus
Also known as glandular fever
Aetiology
Transmission route: saliva/ resp droplets [eg. coughing, kissing]
Presentation
Fever
Lymphadenopathy- posterior cervical nodes
Pharyngitis + tonsilar exudate
HEPATOSPLENOMEGALY
Atypical lymphocytosis
Pathogenesis
EBV infects cells in throat- pharyngitis
Viral DNA incorporated into DNA of host cells
Virions enter lymphatic system
EBV enters B lymphocytes- some become latent and some have productive infection
Infected B lymphocytes produce random immunoglobulins eg heterophile antibodies
T cells destroy these lymphocytes
Latent infected B cells are not attacked by T cells- become immortal
Investigations
Temperature + basic obs
Full blood count - high WCC/lymphocytes- [highest in week two + three]
Blood film- Atypical lymphocytosis [large nuclei]
Heterophile antibodies- Monospot test [doesn’t affect symptoms/disease progression]
EBV specific antibodies
Real time PCR- EBV DNA detection
Management
Supportive symptomatic treatment- Paracetamol/ibuprofen
Corticosteroids if severe: obstructive pharyngitis, severe tonsil swelling, haemolytic anaemia
Contraindicated: amoxicillin/ampicillin= causes widespread maculopapular rash
Prognosis
95% recover with no complications in 3-21 days
EBV specific antibody
Early stages: EBV VCA [viral capsule antigen] IgM
Late stages + acute primary infection: EBV VCA IgG
Past infection: EBNA IgG [Epstein Barr nuclear antigen]
[Remember IgG = gone, IgM= iMMediate]
A 13-year-old female patient presents to A&E with difficulty speaking.
4 days ago she experienced a sore, painful throat, which progressively got worse. She has difficulty swallowing.
On examination there is bilateral tonsillar exudate. There are 3 tender swellings on the anterior border of the sternocleidomastoid muscle.
Her observations are: T 39.1, HR 90, BP 113/68, SpO2 97%.
What is the most likely diagnosis?
A.Infectious mononucleosis
B.Viral tonsillitis
C.Common cold
D.Bacterial tonsillitis
E.Chickenpox
D.Bacterial tonsillitis
Anterior lymph nodes - not posterior lymph nodes= so infectious mononucleosis
HIV
Infection
Transmission
Stages of infection
Presentation
Investigations
Other tests
HIV
Infection process
Retrovirus
Envelope glycoprotein [gp120] binds to CD4 and CCR5
Reverse transcriptase makes viral DNA
Incorporated into viral genome
Viral proteins/virions replicate
T Cell death
Transmission
Sexual contact
Blood/organ transfusion
IV drugs
Pregnancy/childbirth/breast feeding
Occupational
Stages of infection
Seroconversion
4-8 weeks after infection
Fever, night sweats, lymphadenopathy, sore throat, rash, oral ulcers, myalgia, headache, encephalitis, diarrhoea
Early/asymptomatic
18 months to 15 years
Persistent lymphadenopathy + minor symptoms
AIDS
Secondary diseases reflecting severe immunodeficiency
CD4 cell count <200/mm3
Presentation
Opportunistic infections due to immunocompromisation:
Bacterial: Mycobateria, staphylococcus, salmonella, encapsulated organisms
Viral: HHV8/Kaposi Sarcoma, VZV- recurrent shingles, HSV, CMV, HPV- warts, EBV- oral hairy leukoplakia, papovavirus- leukoencephalopathy
Fungal - Cryptococcus, invasive aspergillus, pneumocystis pneumonia, candida
Protozoa- toxoplasma,cryptosporidia, microsporidia
[Ring lesions in CT brain- toxoplasma gondii
Pneumonia- causes CXR infiltrates]
Investigations
ELISA- Western blot
Serum HIV rapid test
Serum HIV DNA PCR [infants]
CD4 count- monitor immune status + staging
Serum viral load [HIV RNA]- millions of copies
FBC, U+E, LFT
Other tests
Drug resistance
Serum hep B and C serology
Syphilis screening
TB - tuberculin skin test
Hairy Leukoplakia
Definition
Aetiology
Hairy Leukoplakia
Definition
Irregular white painless plaques on lateral tongue- cannot be scraped off
Aetiology
Caused by EBV
Happens in HIV patients or people immunosuppressed because of organ transplants
Candidiasis
Definition
Epidemiology
Aetiology
Conditions/Types
Risk factors [for each type]
Symptoms [for each type]
Investigations
Other investigations to exclude differentials or risk factors
Candidiasis
Definition
Infection with candida species
Thrush
Epidemiology
V common
Oral candiasis- 40-70% of adults and children
Aetiology
Dimorphic fungus infection
Candida albicans - commonly causes thrush
Conditions/types of candida infection
Oral candidiasis/oesophageal trush
Vulvovaginitis/balanitis
Diaper rash
Infective endocarditis
Disseminated candiasis [in blood stream, multiple organs affected]
Risk factors
Oral candidiasis/oesophageal thrush-> immunocompromised/steroid inhalers
Vulvovaginitis/balanitis-> diabetes, antibiotic use
Infective endocarditis-> IV drug use
Disseminated candiasis-> immunocompromise/neutropenia
Symptoms
Oral candidiasis/oesophageal thrush- dysphagia
Vulvovaginitis/balanitis- itching, soreness, redness, thick cottage cheese discharfe
Diaper rash
Infective endocarditis
Disseminated candiasis- fever, hypotension, leucocytosis
Investigations
Clinical diagnosis
Basic obsevations + examinations
Swabs useless- b/c commensal in a lot of people anyway
Other investigations to exclude differentials or risk factors
Urinalysis- UTI
Random/fasting blood glucose + glucose tolerance test- diabetes
HIV antibodies
Vaginal pH- STIs
Management
Antifungal [-azole]
Microconazole oral gel
Nystatin suspension
For vulvovaginal- intravaginal cream/pessary or oral antifungal
For oesophageal/systemic- amphotericin B
HIV associated tumours
Kaposi’s sarcoma
- may present as a pink or violaceous [purple] patch on the skin or in the mouth
- AIDS defining condition
- Caused by HHV8
Squamous cell carcinoma
[particularly cervical or anal due to HPV]
Lymphoma
Tonsilitis
Definition
Epidemiology
Aetiology
- viral
- bacterial
Signs
Symptoms
Investigations
How to distinguish between viral and bacterial?
Tonsilitis
Definition
Acute inflammation of the parenchyma of the palatine tonsils
Epidemiology
V common
More common in children- five to fifteen y/o
Aetiology
- viral: rhinovirus, coronavirus, adenovirus [associated with infectious mononucleus infection too]
- bacterial: group A streptococcus, mycoplasma pneumoniae, neisseria gonorhhae
Symptoms and signs
Pain on swallowing
Tonsilar exudate
Tonsilar swelling/enlargment and erythema
Sudden onset sore throat
Fever >38C
Anterior cervical lymphadenopathy
Investigations
Clinical diagnosis- history, exam, basic obs
How to distinguish between viral and bacterial?
Centor criteria
Fever>38C
Tonsilar exudate
Anterior cervical lymphadenopathy/lymphadenitis- painful
No cough
Common cold
Definition
Epidemiology
Aetiology
Investigations
Signs
Symptoms
Management
Common cold
Definition
Mild, self limiting, viral upper resp tract infection
Epidemiology
V common
Aetiology
Viral infection
In order of most to least common viruses:
Rhinovirus [50%]
Coronavirus
Influenza
Parainfluenza
Respiratory syncitial virus
Signs and Symptoms
Runny nose
Sneezing
Cough
Sore throat
Fever
Headache
Malaise
Investigations
Clinical diagnosis
FBC, throat swab, sputum culture, CRP, CXR- consider but rare
Management
Symptomatic supportive:
Analgesia
Antipyretic
Hydration
Decongestant [oxymetazozline nasal, ipratropium nasal]
Sometimes: anti tussive, antihistamine
Abscess
Definition
Aetiology
Types
Table of presentations
Investigation
Management
Complications
Abscess
Definition
Collection of pus in a tissue, organ or cavity created by fibrosis
Aetiology
Usually bacteria
- External [on skin]= Staph aureus
Rarely - parasites, foreign objects
Types
External- Skin
- Cutaneous
- Subcutaneous
Internal
- Lung
- Brain
- Kidneys
- Perianal [diabetes, IBD]
- Tonsils
- Teeth
- Incisional
Signs and symptoms
- External
Erythema
Hot
Painful
Oedema/swelling
Loss of function
- aka dolor, calor, rubor, tumor, functio laetia
- Internal
Systemic signs
Fever
Pain
Investigation
Clinical diagnosis- history, exam, obs
Ultrasound can help
Management
External/uncomplicated:
Aspiration
Incision and drainage
Severe/multiple infection sites/cellulitis/sepsis/rapid progression:
Antibiotics
Incision and drainage
Excision if severe
