Infectious Diseases Flashcards
What is head lice also known as and what is the causative organism
Pediculosis
Nits
Pediculus capitis - parasite
Pathophysiology of head lice
Head lice are small insects that live only on humans, they feed on our blood. Eggs are grey or brown and about the size of a pinhead. The eggs are glued to the hair, close to the scalp and hatch in 7 to 10 days. Nits are the empty egg shells and are white and shiny. They are found further along the hair shaft as they grow out.
How are head lice spread
Head-to-head contact
Symptoms of head lice
Most cases have no symptoms but some complain of:
Itching and scratching on the scalp up to 2-3 weeks after infection
How to diagnose head lice
Fine-toothed combing of wet or dry hair
Management of head lice
Treatment is only indicated if living lice are found
Wet combing with fine combs
Physical insecticide - Dimeticone 4% lotion left on for 8 hours
Chemical insecticide - Malathion
When should household contacts of head lice be treated
Household contacts of patients with head lice do not need to be treated unless they are also affected
What are the two types of herpes simplex virus
HSV-1 and HSV-2
What are the two sensory nerve ganglion that herpes simplex virus infect most commonly
Trigeminal nerve
Sacral nerve
How is genital herpes caused by HSV-1 spread? What about HSV-2?
HSV-1: Oro-genital sex
HSV-2: STI
What are the symptoms of genital herpes
Initial presnetation:
Ulcers or blistering lesions around the genital area
Neuropathic pain (tingling, burning or shooting)
Flu-like symptoms
Dysuria
Inguinal lymphadenopathy
Recurrent episodes usually have more mild symptoms
Investigations for genital herpes
Full history - ask about sexual contacts to establish source of infection
Clinical diagnosis
Viral PCR swab
Management of genital herpes
Oral Acyclovir (valaciclovir or famciclovir as alternatives)
Topical lidocaine 2%
Cleaning with warm salt water
Topical Vaseline
Wear loose clothing
Avoid intercourse with symptoms
Guidelines on treating pregnant women who have genital herpes
Primary attack before 28 weeks gestation = acyclovir followed by prophylactic acyclovir starting from 36 weeks onwards (prevents transmission to baby)
- Caesarean recommended if symptoms are present to avoid spread
Primary attack after 28 weeks = acyclovir followed by regular prophylactic acyclovir
- Caesarean is recommended
If recurrent genital herpes then prophylactic acyclovir from 36 weeks gestation onwards
Symptoms of oral herpes
Prodrome of:
Fever
Malaise
Sore throat
Cervical and submandibular lymphadenopathy
Painful vesicles on a red swollen base in the oral mucosa
Management of oral herpes
Oral acyclovir
Chlorhexidine mouthwash
Pathophysiology of HIV
HIV is a RNA retrovirus
Enters and destroys CD4 T-helper cells
An initial seroconversion flu-like illness occurs within a few weeks of infection
What are the symptoms of HIV seroconversion
Sore throat
Lymphadenopathy
Malaise, myalgia and arthralgia
Diarrhoea
Maculopapular rash
Mouth ulcer
Investigations for HIV seroconversion
HIV antibody and HIV antigen testing - AKA fourth generation testing (first line)
HIV antibodies
- Usually develop 4-6 weeks after infection (99% by 3 months)
p24 antigen
- Viral core protein present 1-3/4 weeks after infection
Combination tests (p24 and HIV antibodies)
- If positive repeat to confirm diagnosis
HIV RNA load
HIV testing in asymptomatic patients should be done 4 weeks after possible infection
- If first test is negative then repeat at 12 weeks
How is HIV monitored?
Testing CD4 count - lower = higher risk of opportunistic infections
Normal range = 500-1200
High risk of opportunistic infections = under 200
Management of HIV
Treatment started as soon as diagnosed
Antiretroviral therapy (ART) = involves at least three drugs:
- 2 nucleoside reverse transcriptase inhibitors (NRTI)
- e.g. tenofovir and emtricitabine
+
- Protease inhibitor
- e.g. indinavir
or
- Non-nucleoside reverse transcriptase inhibitor (NNRTI)
- e.g. nevirapine
AIM = normal CD4 count and undetectable viral load
What are the five features of HIV-associated nephropathy
Massive proteinuria = nephrotic syndrome
Normal or large kidneys
Focal segmental glomerulosclerosis with focal or global capillary collapse on renal biopsy
Elevated urea and creatinine
Normotension
What is the most common opportunistic infection in AIDS
Pneumocystis jiroveci
All patients with CD4 count < 200 should receive PCP prophylaxis
Symptoms of Pneumocystis jiroveci
Dyspnoea
Dry cough
Fever
Very few chest signs
May cause:
Hepatosplenomegaly
Lymphadenopathy
Choroid lesions
Investigations for Pneumocystis jiroveci
CXR: bilateral interstitial pulmonary infiltrates
Exercise induced desaturation
Bronchoalveolar lavage shows pneumocystis jiroveci
Management of pneumocystis jiroveci
Co-trimoxazole
Severe: IV pentamidine
If hypoxic: steroids
What is the most common cause of oesophagitis in patients with HIV
Oesophageal candidiasis
(seen in patients with a CD4 count > 100)
Symptoms of oesophageal candidiasis
Dysphagia
Odynophagia
Treatment for oesophageal candidiasis
Fluconazole
or
Itraconazole
What conditions can patients with a CD4 count (HIV) between 200 and 500 have?
Oral thrush
Shingles
Hairy leucoplakia
Kaposi sarcoma
What conditions can patients with a CD4 count (HIV) between 100 and 200 have?
Pneumocystis jiroveci pneumonia
Cerebral toxoplasmosis
HIV dementia
Cryptosporidiosis
What conditions can patients with a CD4 count (HIV) between 50 and 100 have?
Aspergiliosis
Oesophageal candidiasis
Cryptococcal meningitis
Primary CNS lymphoma
What conditions can patients with a CD4 count (HIV) less than 50?
Cytomegalovirus retinitis
What organism causes Kaposi sarcoma in patients with HIV?
HHV-8
How does Kaposi sarcoma present in patients with HIV
purple papules or plaques on the skin or mucosa
Haemoptysis if respiratory involvement
Treatment of Kaposi sarcoma in HIV
Radiotherapy and resection
Most common cause of diarrhoea in HIV patients
Cryptosporidium - intracellular protazoa
Treatment of diarrhoea in HIV patients
Supportive
How to prevent STI spread of HIV
Condoms
ART therapy
What monitoring should patients with HIV undergo
Monitoring of cardiovascular risk factors - blood lipids
Yearly cervical smears - increased risk of HPV infection and cervical cancer
Can a mother breastfeed if she has HIV
Yes, if mother is adamant and viral load is undetectable
Otherwise, advise not to
What is the mode of delivery if a woman has a HIV viral load of >50, <50 and <400?
<50 = normal vaginal
>50 = consider a pre-labour caesarean
>400 = pre-labour caesarean
IV zidovudine should be started 4 hours prior to c-section
If the viral load of HIV is unknown or >1000 what should be done?
IV zidovudine given during labour and delivery
What are neonates given if the mother has a HIV viral load of <50 and >50?
<50 = oral zidovudine for 2-4 weeks
>50 = Triple ART for 4-6 weeks
What should HIV positive pregnant women be offered during pregnancy
ART - whether they were taking it before or not
What factors reduce vertical transmission of HIV
Maternal ART
C-section
Neonatal ART
Bottle feeding
What is post-exposure prophylaxis (in the context of HIV)? What drugs are used?
Can be used after exposure to reduce the risk of transmission
emtricitabine/tenofovir (Truvada) and raltegravir for 28 days.
What patients should be screened for MRSA?
All patients awaiting elective admission
All emergency admissions
How should a person be screened for MRSA
Nasal swab and skin lesions/wounds
One a carrier of MRSA is identified, what should be done?
Suppressive therapy:
Nose: mupirocin 2% in white soft paraffin, tds for 5 days
Skin: chlorhexidine gluconate, od for 5 days, apply all over but especially in axilla, groin and perineum
What antibiotics are commonly used for MRSA
1st line = vancomycin or teicoplanin
then
Linezolid - reserved for resistant cases
What is the causative agent in Lyme disease and what is it spread by
Borrelia burgdorferi - spread by ticks
What are the symptoms of Lyme disease
Erythema migrans - ‘bulls eye’ rash seen at the site of the bite
- Typically develops 1-4 weeks after initial bite
- Painless and more than 5cm in diameter
Systemic features:
Fever
Headache
Lethargy
Arthralgia
What are the later features (after 30 days) of Lyme disease
Cardiovascular:
Heart block
Peri/myocarditis
Neurological:
Facial nerve palsy
Radicular pain
Meningitis
Investigations for Lyme disease
Clinical if erythema migrans present
Enzyme Linked Immunosorbent Assay (ELISA) antibodies to Borrelia burgdorferi = 1st LINE
Management for Lyme disease
Asymptomatic:
- If tick present then remove with tweezer as close to skin as possible
Symptomatic:
Doxycycline (amoxicillin alternative)
Ceftriaxone if disseminated disease
What is the Jarisch-Herxheimer reaction?
Seen after initiating antibiotics. symptoms are:
Fever
Rash
Tachycardia
What are the different classifications of necrotising fasciitis
Classified according to the causative organism:
Type 1 - caused by mixed anaerobes and aerobes (often occurs post-surgery in diabetics)
Type 2 - caused by streptococcus pyogenes
What are the risk factors for developing necrotising fasciitis
Recent trauma
Burns
Soft tissue infections
Diabetes - particularly if patient is on SGLT-2 inhibitors
IV drug users
Immunosuppression
What is the most commonly affected site for necrotising fasciitis
Perineum - Fournier’s gangrene
What are the features of necrotising fasciitis
Acute onset
Pain, swelling and erythema at affected site
Extremely tender over infected tissue with hypoesthesia to light touch
Skin necrosis and crepitus/gas gangrene are late signs
Fever
Tachycardia
What is staphylococcal toxic shock syndrome
Severe systemic reaction to staphylococcal exotoxins, the TSST-1 superantigen toxin
What is the main cause of staphylococcal toxic shock syndrome
Infected tampons
Symptoms of staphylococcal toxic shock syndrome
Fever > 38.9
Hypotension - systolic < 90
Diffuse erythematous rash
Desquamation of rash - especially of the palms and soles
GI symptoms - diarrhoea and vomiting, hepatitis
Renal failure
Thrombocytopenia
Mucus membrane erythema
CNS involvement - confusion
Management of staphylococcal toxic shock syndrome
Removal of infection focus - retained tampon
IV fluids
IV antibiotics
What is a perianal abscess
Collection of pus within the subcutaneous tissue of the anus that has tracked from the tissue surrounding the anal sphincter.
Risk factors for perianal abscess
Male
Over 40
Crohn’s disease
Diabetes
Malignancy
Cause of perianal abscess
Generally colonised by gut flora such as E.coli
Symptoms of perianal abscess
Pain around the anus made worse by sitting
Hardened tissue in the anal region
Pus like discharge from the anus
May have features of systemic infection if long standing
Investigations for perianal abscess
Clinical
MRI is gold standard
Treatment of perianal abscess
Surgical incision and drainage under local anaesthetic
Antibiotics if features of systemic infection
What diseases are the most common cause of abdominal cavity fistula
Diverticular disease
Crohn’s disease
What are the four types of fistula
Enterocutaneous
Enteroenteric/enterocolic
Enterovaginal
Enterovesicular
What is chicken pox cause by
Varicella zoster virus
How is chicken pox spread
Via respiratory route
How long are people with chicken pox infectious for
4 days prior to rash
5 days after rash
Symptoms of chicken pox
Fever initially
Itchy rash starting on head/trunk before spreading
Initially macular then papular then vesicular
Management of chicken pox
Supportive
Trim nails
Calamine lotion
What is the school exclusion guidelines for chicken pox
Until lesions have crusted over
(usually 5 days after rash appeared)
What is a complication of chicken pox and what increases the chance of this complication
Secondary bacterial infection of the lesions
NSAIDs increase the chance
Group A streptococcal soft tissue infection may occur resulting in necrotising fasciitis
Complications of chicken pox
Pneumonia
Encephalitis
Disseminated haemorrhagic chicken pox
Arthritis, Nephritis, Pancreatitis
What type of organism is Clostridium difficile
gram-positive, rod shaped, anaerobic bacteria
What are the causes of C.diff infection
PPIs and Antibiotics (begin with letter C):
Clindamycin
Ciprofloxacin
Cephalosporins
Carbapenems (meropenem)
What toxins does C.diff produce
toxin A
toxin B
Mode of transmission of C.diff
Faecal-oral
Symptoms of C.diff infection
Diarrhoea
Abdominal pain
Severe:
Dehydration
Fever, tachycardia and hypotension (systemic symptoms)
How do we differentiate between mild, moderate, severe and life threatening C.diff infection
Mild: Normal WCC
Moderate: raised WCC & typically 3-5 loose stools a day
Severe: raised WCC or acutely raised creatinine, temp above 38.5 or severe colitis
Life threatening: Hypotension, ileus or toxic megacolon
Investigations for C.diff infection
Stool sample and test for:
C.diff antigen (glutamate dehydrogenase) –> if positive does not necessarily mean it is producing toxins
A and B toxins - by PCR or enzyme immunoassay
How to manage C.diff infection
First episode:
Oral vancomycin (fidaxomicin 2nd line)
Recurrent episode:
Within 12 weeks of initial - oral fidaxomicin
After 12 weeks - oral vancomycin OR fidaxomicin
Life threatening:
Oral vancomycin AND IV metronidazole
Define sepsis
Where the body launches a large immune response to an infection causing systemic inflammation and organ dysfunction
What is the difference between sepsis and septic shock
Septic shock is when the arterial blood pressure drops despite adequate fluid resuscitation resulting in organ hypoperfusion
Define shock
Insufficient tissue perfusion
What are the different types of shock
Septic shock
Hemorrhagic shock
Neurogenic shock - most commonly after a spinal cord transection - peripheral vasoconstrictor can be used to return vascular tone to normal
Cardiogenic shock - the main cause is ischaemic heart disease
Anaphylactic shock - from nuts, drugs or venom (wasp sting)
How is septic shock diagnosed
Low mean arterial pressure (below 65mmHg) despite fluid resuscitation (requiring vasopressors - noradrenaline)
Rasided serum lactate - more than 2mmol/L
What is the SOFA score used for? What does it take into account
Sepsis-related organ failure assessment (SOFA)
Can be used to assess the severity of organ dysfunction in sepsis, takes into account:
Hypoxia
Increased O2 requirements
Requiring mechanical ventilation
Low platelets (thrombocytopenia)
Reduced GCS
Raised bilirubin
Reduced BP
Raised creatinine
Risk factors for developing sepsis?
Anything that causes immune dysfunction, frailty, or a predisposition to infection:
Very young or old patient s(under 1 or over 75)
Chronic conditions such as COPD or diabetes
Chemotherapy, immunosuppressants or steroids
Surgery, trauma, or burns
Pregnancy and childbirth
Indwelling medical devices - catheter or central lines
How is sepsis identified?
Using the National Early Warning Score (NEWS2) score, six things are measured:
Temperature
Blood pressure
Heart rate
Respiratory rate
Oxygen sats
Consciousness level
Additional signs of infection also checked for:
Signs of sources - cellulitis, cough, dysuria, wound
Reduced urine output
Mottled skin
Cyanosis
New onset arrhythmias
Non-blanching rash (meningococcal septicemia)
What is often an early sign of sepsis
Tachypnoea
How can elderly patients present with sepsis
Confusion
Drowsiness
When would patients with sepsis have normal observations despite being life-threateningly unwell
Neutropenic or immunocompromised patients
Investigations for sepsis
Sepsis 6:
Take 3:
Serum lactate
Blood cultures
Urine output - measure hourly
Give 3:
Oxygen to maintain O2 sats 94-98% (88-92% for COPD patients)
Empirical broad-spectrum antibiotics
IV fluids
Blood tests
FBC
U&Es - check for AKI
LFTs - check for the source of infection
CRP
Blood glucose - for hypo/hyperglycemia
Blood cultures - assess for bacteremia
Blood gas - for lactate
Urine dipstick and culture
CXR
CT scan if intra-abdominal infection/abscess is suspected
LP for meningitis or encephalitis
Treatment for sepsis
Administer O2 - aim for 92-94% (88-92% in COPD)
IV fluids - bolus of 500ml crystalloid over less than 15 mins
Broad-spectrum antibiotics
What are the red flag criteria to initiate sepsis 6 immediately
Respons to voice or pain only/unresponsive
Acute confusional state (low GCS)
Systolic BP <= 90mmHg (or drop of 40 from normal)
HR > 130
RR >= 25
Need oxygen to keep SpO2 >= 92
Non-blanching rash/mottled/ashe/cyanotic
Not passed urine in last 18 hours or urine output <0.5ml/kg/hr
Lactate > 2mmol/L
Recent chemotherapy
What is neutropenic sepsis
Refers to sepsis in someone with an absolute neutrophil count below 0.5 x 109/L (or likely to fall to this level)
What can cause neutropenic sepsis
Immunosuppressants or anti-cancer treatment:
Methotrexate
Sulfasalazine
Chemo
Carbimazole
Hydroxychloroquine
Infliximab
Rituximab
Clozapine
What is the treatment of neutropenic sepsis
Tazocin (piperacillin with tazobactam)
What is the causative organism of mumps
RNA paramyxovirus
How is mumps spread
Droplets
How long are patients with mumps infective for
7 days before and 9 days after parotid swelling starts
What are the symptoms of mumps
Fever
Malaise
Muscular pain
Parotitis - presents as earache or pain on eating - unilateral then becomes bilateral in 70% of patients
How to prevent mumps
MMR vaccine
Management of mumps
Rest
Paracetamol for high fever/discomfort
Notifiable disease
Complications of mumps
Orchitis
Hearing loss
Meningoencephalitis
Pancreatitis
What type of virus is the influenza virus
RNA virus
Who is the influenza vaccine free to?
Aged 65 or over
Young children
Pregnant women
Chronic health conditions - COPD, HF, DM
Healthcare workers and carers
What are the symptoms of influenza
Fever
Lethargy and fatigue
Anorexia - loss of appetite
Muscle and joint aches
Headache
Dry cough
Sore throat
Coryzal symptoms
How do you differentiate between the common cold and a flu
Flu = abrupt onset, fever and muscle aches and lethargy
Common cold - gradual onset, no fever
How to diagnose influenza
Viral nasal or throat swabs aresent for PCR analysis
In which patients do you treat influenza
Chronic disease of respiratory, cardiac, renal, hepatic, or neurological nature
Diabetes
Immunosuppression
Morbid obesity
What is the management of influenza
1st line = oseltamivir
2nd line = zanamivir
Needs to be started within 48 hours of onset
What si the post-exposure prophylaxis options for influenza? Which patients can receive this
Oral oseltamavir 75mg OD for 10 days
Inhaled zanamivir 10mg OD for 10 days
Given if:
Initial treatment started within 48 hours
Increased risk - chronic disease or immunosuppression
Not vaccinated
Complications of influenza
Viral pneumonia
Sinusitis, otitis media and bronchitis
Worsening of chronic condition
Febrile convulsions
Encephalitis
What measures can be put into place pre-operatively to reduce the risk of surgical site infections
Use electric clippers to remove bodily hair
Antibiotic prophylaxis if placement of prosthesis or valve, contaminated surgery or clean-contaminated surgery
Give single dose IV antibiotics on anesthesia (give earlier if tourniquet used)
What measures can be put into place intra-operatively to reduce the risk of surgical site infections
Prepare skin with chlorhexidine
Cover the surgical site with a dressing
What measures can be put into place post-operatively to reduce the risk of surgical site infections?
Tissue viability advice for management of surgical wounds healing by secondary intention
What is gangrene
A serious medical condition characterised by the death of body tissue due to a lack of blood supply, infection, or both
What are the causes of gangrene
Interruption of blood supply leading to tissue ischemia and necrosis. Can occur due to:
Arterial occlusion - Atherosclerosis, thrombosis, or embolism can obstruct blood flow
Infection
Trauma - can compromise blood supply and introduce pathogens
Chronic conditions - diabtetes
What are the three types of gangrene
Dry
Wet
Gas
What is dry gangrene usually caused by? What is the appearance?
Chronic ischemia (usually due to PAD)
Characterized by:
Dry, shrivelled and blackened tissue
Clear demarcation between necrotic and live tissue
Typically painless due to nerve damage
What is wet gangrene usually caused by? What is the appearance?
Sudden lack of blood supply combined with infection
Characterised by:
Swollen,moist and blistered tissue
Foul odour
Systemic symptoms - fever and malaise
Severe pain and erythema of affected area
Can lead to sepsis
What is gas gangrene usually caused by? What is the appearance?
Caused by infection with Clostridium bacteria - which produces gas and toxins
Characterised by:
Severe pain and swelling
Crepitus due to gas production
Rapid onset of systemic symptoms - tachycardia, hypotension and shock
Management of gangrene
Surgical intervention - debridement, amputation (if necessary) and revascularization
Antibiotics - empirical broad-spectrum
Supportive - IV fluids, analgesia
Hyperbaric oxygen therapy - used in some cases of gas gangrene to enhance O2 delivery to tissue and inhibit anaerobic bacterial growth
What antibiotics are recommended for gas gangrene
High-dose penicillin and clindamycin
What is the causative agent in Covid-19
SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2)
How is Covid-19 spread
Respiratory droplets
Contact with contaminated surfaces
Symptoms of Covid-19
Fever
Cough
Fatigue
Loss of taste or smell
Myalgia
Nausea
Diarrhoea
If severe:
SOB
Chest pain
Confusion
Cyanosis
Investigation for Covid-19
Reverse transcription PCR (RT-PCR)
Antigen test
Serological test - detect antibodies
Imaging:
CXR - may show bilateral infiltrates
CT scan - can reveal ground glass opacities and consolidation
Management of Covid-19
General:
Isolation
Supportive - hydrations, antipyretics, oxygen
Pharmacological:
Antivirals - remdesivir
Corticosteroids - dexamethasone
Supportive:
Oxygen therapy
How to prevent Covid-19
Vaccine
Mask-wearing
Hand hygiene
Social distancing
