Infectious Disease Flashcards
What is kaposis sarcoma caused by?
Caused by HHV-8
Presents as purple or plaques on the skin or mucosa (eg; GI and resp tract)
Skin lesions mag later ulcerate
Resp involvement may cause massive haemoptysis and pleural effusion
Radiotherapy and resection
What is legionella, what are the features and the treatment?
Legionnaire’s disease is caused by the intracellular bacterium Legionella pneumophilia. It typically colonizes water tanks and hence questions may hint at air-conditioning systems or foreign holidays. Person-to-person transmission is not seen
Features flu-like symptoms including fever (present in > 95% of patients) dry cough relative bradycardia confusion lymphopaenia hyponatraemia deranged liver function tests pleural effusion: seen in around 30% of patients
Diagnosis
urinary antigen
Management
treat with erythromycin/clarithromycin
What investigations would you do for meningitis?
FBC CRP Coagulation screen Blood culture Whole blood PCR Blood glucose Blood gas Lumbar puncture if no signs of raised ICP
How do you manage meningitis in the community?
All patients should be transferred to hospital urgently.
If patients are in a pre hospital setting (ie: GP surgery) and meningococcal disease is suspected then IM benzylpenicillin may be given, as long as this doesn’t delay transit to hospital
What would you give for someone aged <3 months with meningitis?
IV cefotaxime + amoxicillin
What would you give for someone with meningitis aged 3 months- 50 years?
IV cefotaxime
What would you give for someone aged >59 years with meningitis?
IV cefotaxime + amoxicillin
What would you give for meningococcal meningitis?
IV benzylpenicillin or cefotaxime
What should you use if someone has an immediate hypersensitivity reaction to penicillin?
Chloramphenicol
How do you manage contacts of meningitis?
prophylaxis needs to be offered to household and close contacts of patients affected with meningococcal meningitis. Prophylaxis should also be offered to people who been exposed to respiratory secretion, regardless of the closeness of contact
people who have been exposed to a patient with confirmed bacterial meningitis should be given prophylactic antibiotics if they have close contact within the 7 days before onset
oral ciprofloxacin or rifampicin or may be used. The Health Protection Agency (HPA) guidelines now state that whilst either may be used ciprofloxacin is the drug of choice as it is widely available and only requires one dose
the risk is highest in the first 7 days but persists for at least 4 weeks
meningococcal vaccination should be offered to close contacts when serotype results are available, including booster doses to those who had the vaccine in infancy
for pneumococcal meningitis, no prophylaxis is generally needed. There are however exceptions to this. If a cluster of cases of pneumococcal meningitis occur the HPA have a protocol for offering close contacts antibiotic prophylaxis. Please see the link for more details
What is malaria caused by?
Plasmodium Protozoa which is spread by the female anopheles mosquito
Plasmodium falciparum causes nearly all episodes of severe malaria
Plasmodium vivax is the most common cause of benign malaria
What is the pathophysiology behind sepsis?
Where the body launches a large immune response to infection which causes systemic inflammation and affects the functioning of the organs in the body.
The bacteria or other pathogens are recognised by macrophages, lymphocytes and mast cells. These cells release vast amounts of cytokines like interleukins and tumor necrosis factor to alert the immune system of an invader. These cytokines activate other parts of the immune system. This immune activation leads to further release of chemicals such as nitrous oxide that causes vasodilation. This full immune response causes inflammation throughout the body.
Many of the cytokines cause the endothelial lining of the blood vessels to become more permeable, this causes fluid to leak out of the blood and into the extracellular space, leading to oedema and reduction in intravascular volume
Activation of the coagulation system leads to deposition of fibrin throughout the circulation further compromising organ and tissue perfusion. It also leads to consumption of platelets and clotting factors as they are being used up to form the clots within the circulatory system. This leads to thrombocytopenia, haemorrhages and an inability to form clots and stop bleeding. This is called disseminated intravascular coagulopathy (DIC).
Blood lactate rises due to hypoperfusion of tissues that starves the tissues of oxygen causing them to switch to anaerobic respiration. A waste product of anaerobic respiration is lactate.
What is severe sepsis?
Severe sepsis is defined when sepsis is present and results in organ dysfunction, for example:
Hypoxia Oliguria Acute Kidney Injury Thrombocytopenia Coagulation dysfunction Hypotension Hyperlactaemia (> 2 mmol/L)
What are the risk factors for sepsis?
Any condition that impacts the immune system or makes the patient more frail or prone to infection is a risk factor for developing sepsis:
Very young or old patients (under 1 or over 75 years)
Chronic conditions such as COPD and diabetes
Chemotherapy, immunosuppressants or steroids
Surgery or recent trauma or burns
Pregnancy or peripartum
Indwelling medical devices such as catheters or central lines
What is the presentation of sepsis?
The National Early Warning Score (NEWS) is used in the UK to pick up the signs of sepsis. This involves checking physical observations and their consciousness level:
Temperature Heart rate Respiratory rate Oxygen saturations Blood pressure Consciousness level Other signs on examination:
Signs of potential sources such as cellulitis, discharge from a wound, cough or dysuria
Non-blanching rash can indicate meningococcal septicaemia
Reduced urine output
Mottled skin
Cyanosis
Arrhythmias such as new onset atrial fibrillation
Whats is often the first sign of sepsis?
There are a few key points worth being aware of:
High respiratory rate (tachypnoea) is often the first sign of sepsis
Elderly patients often present with confusion or drowsiness or simply “off legs”
Neutropenic or immunosuppressed patients may have normal observations and temperature despite being life threatening unwell
What Ix should you do for sepsis?
Arrange blood tests for patients with suspected sepsis:
Full blood count to assess cell count including white cells and neutrophils
U&Es to assess kidney function and for acute kidney injury
LFTs to assess liver function and for possible source of infection
CRP to assess inflammation
Clotting to assess for disseminated intravascular coagulopathy (DIC)
Blood cultures to assess for bacteraemia
Blood gas to assess lactate, pH and glucose
Additional investigations can be helpful in locating the source of the infection:
Urine dipstick and culture
Chest xray
CT scan if intra-abdominal infection or abscess is suspected
Lumbar puncture for meningitis or encephalitis
What is the sepsis 6?
Three Tests:
Blood lactate level
Blood cultures
Urine output
Three Treatments:
Oxygen to maintain oxygen saturations 94-98% (or 88-92% in COPD)
Empirical broad spectrum antibiotics
IV fluids
What is neutropenic sepsis?
Neutropenic sepsis is a very important medical emergency. It is sepsis in a patient with a low neutrophil count of less than 1 x 109/L.
Low neutrophil counts are usually the consequence of anti-cancer or immunosuppressant treatment. Medication that may cause neutropenia include:
Anti-cancer chemotherapy
Clozapine (schizophrenia)
Hydroxychloroquine (rheumatoid arthritis)
Methotrexate (rheumatoid arthritis)
Sulfasalazine (rheumatoid arthritis)
Carbimazole (hyperthyroidism)
Quinine (malaria)
Infliximab (monoclonal antibody use for immunosuppression)
Rituximab (monoclonal antibody use for immunosuppression)
What is cellulitis?
Cellulitis is an infection of the skin and the soft tissues underneath. The skin normally acts as a very effective physical barrier between the environment and soft tissues. When a patient presents with cellulitis look for a breach in the skin barrier and a point of entry for the bacteria. This may be due to skin trauma, eczematous skin, fungal nail infections or ulcers.
What is the presentation of cllulitis?
The skin will demonstrate changes:
Erythema (red discolouration) Warm or hot to touch Tense Thickened Oedematous Bullae (fluid-filled blisters) A golden-yellow crust can be present and indicate a staphylococcus aureus infection
What are the causes of cellulitis?
Staphylococcus aureus
Group A Streptococcus (mainly streptococcus pyogenes)
Group C Streptococcus (mainly Streptococcus dysgalactiae)
What is the classification system NICE recommend for cellulitis?
Eron classification
What is the treatment for cellulitis?
Flucloxacillim
What is the cause of bacteria tonsillitis?
Group A streptococcus- streptococcus pyogenes
What is used to establish whether tonsillitis is bacterial or viral?
The Centor Criteria are used to estimate the probability that tonsillitis is due to a bacteria infection, and therefore requires antibiotics. A score of < 3 indicates they are unlikely to benefit from an antibiotic and antibiotics should not routinely be given. A score of ≥ 3 gives a 40 – 60 % probability of bacterial tonsillitis and it is appropriate to offer antibiotics. One point is given for each of the following:
Fever > 38ºC
Tonsillar exudates
Absence of cough
Tender anterior cervical lymph nodes (lymphadenopathy)
What is the treatment of bacterial tonsilitis?
Penicillin V (also called phenoxymethylpenicillin) for a 10 day course is typically first line.
Alternatives antibiotics and for a broader spectrum of activity:
Co-amoxiclav
Clarithromycin
Doxycycline
What is the presentation of otitis media?
It is difficult to distinguish between bacterial and viral otitis media. It presents with ear pain. Examination will reveal a bulging red tympanic membrane. If the ear drum perforates there can be discharge from the ear.
What is the management of otitis media?
Otitis media usually resolves within 3-7 days without antibiotics. If systemically unwell consider admission.
An appropriate initial antibiotic in the community:
Amoxicillin
Alternatives in penicillin allergy:
Clarithromycin
Erythromycin
Second line if not responding to amoxicillin after 2 days:
Co-amoxiclav
What is sinusitis?
Again sinusitis can be bacteria or viral. NICE recommend providing an antibiotic if the patient is systemically very unwell however most patients do not require an antibiotic.
Sinusitis usually last 2-3 weeks and resolves without treatment.
What is the management of sinusitis?
Symptoms for less than 10 days: No antibiotics.
No improvement after 10 days: 2 weeks of high-dose steroid nasal spray
No improvement after 10 days and likely bacterial cause: consider delayed or immediate prescription of antibiotics
Penicillin V (also called phenoxymethylpenicillin) for a 5 day course is typically first line.
Alternatives in penicillin allergy:
Clarithromycin
Erythromycin (pregnancy)
Doxycycline
Second line if not responding after 2 days:
Co-amoxiclav
How do you treat spontaneous bacterial peritonitis?
Piperacillin/Tazobactam (Tazocin) is often first line
Cephalosporins such as cefotaxime are also often used
Levofloxacin plus metronidazole is an common alternative in penicillin allergy
What is septic arthritis?
Septic arthritis is where an infection occurs within a joint. This could be in a native joint, meaning the persons own joint, or in a joint replacement. Infection in a joint is an emergency as the infection can quickly begin to destroy the joint and cause systemic illness. Septic arthritis has a mortality of around 10%.
It is a common and important complication of joint replacement. It occurs in around 1% of straight forward hip or knee replacements. This percentage is higher in revision surgery.
What is the presentation of septic arthritis?
Septic arthritis is where an infection occurs within a joint. This could be in a native joint, meaning the persons own joint, or in a joint replacement. Infection in a joint is an emergency as the infection can quickly begin to destroy the joint and cause systemic illness. Septic arthritis has a mortality of around 10%.
It is a common and important complication of joint replacement. It occurs in around 1% of straight forward hip or knee replacements. This percentage is higher in revision surgery.
