Infectious Diseases Flashcards
How may cellulitis present?
Erythema Warm or hot to the touch Tense Thickened Oedematous Bullae
What sign can be indicative of a S.aureus cellulitis?
Golden-yellow crust
What are the most common causes of cellulitis?
S.aureus
Group A Strept (S.pyogenes)
Group C Strept (S.dysgalactiae)
What classification can be used to assess the severity of cellulitis?
Eron Classification
Class 1 - no systemic toxicity or comorbidities
Class 2 - systemic toxicity or comorbidity
Class 3 - Significant systemic toxicity or significant comorbidity
Class 4 - Sepsis or life-threatening infection
When should a patient be admitted for IV antibiotics in cellulitis?
Class 3 or 4
What is the first line antibiotic for cellulitis?
Flucloxacillin
If a patient has a penicillin allergy, what antibiotic should be given if they have cellulitis?
Clarithromycin
What type of organism is Neisseria meningitidis?
Gram negative diploccocus
What type of meningitis is associated with a non-blanching rash?
Meningococcal septicaemia
What does the non-blanching rash in meningococcal septicaemia indicate?
DIC
Subcutaneous haemorrhage
In children and adults, what are the most common cause of bacterial meningitis?
Neisseria meningitidis
Streptococcus pneumoniae
In neonates, what is the most common cause of bacterial meningitis?
Group B Streptococcus
How can meningitis present?
Fever Neck stiffness Photophobia Vomiting Headache Altered consciousness Seizures
What are the two special tests that can be used to assess for meningism?
Kernig’s test
Brudzinski test
In the community, what antibiotic should be given prior to transfer to hospital?
Benzylpenicillin (IM/IV)
Under 1: 300mg
1-9 years: 600mg
>10 years: 1200mg
Once admitted to hospital, what two investigations should be performed, ideally before initiating antibiotics in a patient with suspected meningitis?
Blood cultures
Lumber puncture
If meningococcal disease is suspected, what specific blood test should be performed?
Meningococcal PCR
What antibiotic regimen should be commenced in neonates under 3 months if they have bacterial meningitis?
Cefotraxime
Amoxicillin
In people over 3 months old, what antibiotic should be commenced if they have bacterial meningitis?
Cefotriaxone
Along with antibiotics, what other medication should be started in patients with bacterial meningitis and why?
Dexamethasone (QDS for 4 days)
Reduce frequency and severity of hearing loss and neurological damage
What can be used as a prophylaxis treatment in close contacts of a patient with bacterial meningitis?
Single dose of ciprofloxacin
What are the most common causes of viral meningitis?
Herpes simplex virus
Enterovirus
Varicella zoster virus
What drug can be used to treat viral meningitis caused by herpes simplex virus?
Acyclovir
When sending a LP for suspected meningitis, what tests should be requested?
Bacterial culture Viral PCR Cell count Protein Glucose
(Paired serum glucose sample)
What are the complications of meningitis?
Hearing loss Seizures and epilepsy Cognitive impairment and learning disability Memory loss Focal neurological deficits
What bacteria causes tuberculosis?
mycobacterium tuberculosis
What type of bacteria is mycobacterium tuberculosis?
Bacillus
What type of staining is used in the assessment of tuberculosis and how is it described?
Ziehl-Neeson Staining
Acid-fast bacillus
How does TB spread through the body?
Through the lymphatics and blood
What is latent TB?
Immune system encapsulates sites of TB infection and stops the disease progression
How is it described if latent TB becomes reactivated
Secondary TB
How is it described if the immune system is unable to control the TB causing disseminating, severe disease?
Miliary TB
Give some sites of extrapulmonary TB
Lymph nodes - cold abscess Pleura CNS and spine (Pott's disease) Pericardium GI system GU system Bones and joints Cutaneous TB
Describe the BCG vaccine
Interdermal infection of live attenuated TB
Prior to the BCG vaccine, what test needs to be performed?
Mantoux test (get the vaccine if it is negative)
How can TB present?
Chronic, gradually worsening symptoms
Lethargy Fever Night sweats Cough ± haemoptysis Lymphadenopathy Erythema nodosum Spinal pain - in spinal TB (Potts disease)
What are the two tests to assess for an immune response to TB?
Mantoux test
Interferon Gamma Release Assay
What does the Mantoux test look for?
What does it indicate?
Previous immune response to TB
Previous vaccination
Latent TB
Active TB
Describe how a Mantoux test is performed
Tuberculin is injected into the transdermal space
Causes a bleb to form
If >5mm after 72 hours = positive
Need to assess for active disease
Describe how an Interferon-Gamma Release Assay is performed
Sample of blood is mixed with antigens from TB
Previous contract with TB = WBC sensitised to antigens –> release interferon-gamma
What is the role of IGRA test in patients who have a positive Mantoux test with no active disease?
Latent TB
What are the potential CXR appearances in primary TB
Patchy consolidation
Pleural effusions
Hilar lymphadenopathy
What are the potential CXR appearances in reactivated TB?
Patchy/nodular consolidations with cavitation
How might miliary TB look on CXR
Millet seeds
What are the three ways to collect culture samples in the investigation of TB?
- Sputum
- Mycobacterium blood culture
- Lymph node aspiration or biopsy
How can Latent TB be managed in an otherwise healthy patient?
No treatment
How can Latent TB be managed in patients who are at risk of reactivation?
Isoniazid and rifampicin for 3 months
OR
Isoniazid for 6 months
What drugs are used in the management of active TB?
Rifampicin - 6 months
Isoniazid - 6 months
Pyrazinamide - 2 months
Ethambutol - 2 months
Alongside, Rifampicin, Isoniazid, Pyrazinamide and Ethambutol, what other drug should be prescribed and why?
Pyridoxine (prophylaxis against the peripheral neuropathy caused by isoniazid)
What are some side effects of Rifampicin?
Red/orange secretions
Potent induce of cytochrome p450
Hepatotoxicity
What is the side effects of Isoniazid?
Peripheral neuropathy (co-prescribe pyridoxine) Hepatotoxicity
What is the side effect of pyrazinamide?
Hyperuraemic –> gout
Hepatotoxicity
What is the side effect of ethambutol?
Reduced visual acuity
Colour blindness
What type of virus is HIV?
RNA Retrovirus
Give some examples of AIDS defining illnesses
Kaposi's Sarcoma PCP Cytomegalovirus infection Candiadiasis (bronchial, oesophageal) Lymphomas TB
How long may an antibody test for HIV be negative after a potential exposure?
3 months
How is HIV screened for in hospital?
Antibody blood test
In HIV PCR testing, what antigen is tested for?
p24 antigen
What type of testing gives the viral load of HIV?
HIV RNA PCR testing
What is the normal range for CD4 cells?
500-1200 cells/mm3
What CD4 count is considered as end stage HIV/AIDS?
<200 cells/mm3
Define viral load in regards tro HIV
Number of copies of HIV RNA per ml of blood
Who is offered ART?
Anyone with a diagnosis of HIV regardless of CD4 levels or viral load
What is the aim of treatment in HIV?
Achieve a normal CD4 count and an undetectable viral load
What is the recommended starting regimen in HIV treatment?
2 NRTIs (nuclease reverse transcriptase inhibitors) - tenofovir, emtricitabine 1 other agent
What are the classes of HIV ARTs?
Protease inhibitors
Integrase inhibitors
Nuclease reverse transcriptase inhibitors
Non-nucleoside reverse transcriptase inhibitors
Entry inhibitors
What should be given as prophylaxis against PCP and at what CD4 count should this be initiated?
Co-trimoxazole
CD4 <200/mm3
How often should a female patient with HIV attend cervical screening?
Every year
What vaccinations should a person living with HIV have?
annual influenza pneumococcal (5-10y) Hep A and B Tetanus Diphtheria Polio
What type of vaccines should be avoided in people living with HIV?
Live
How long should a newborn be given ART if they are born to a HIV positive mother?
4 weeks
How long post-exposure can post-exposure prophylaxis to HIV be given?
Within 72 hours
combination ART for 28 days
