Infection Summary Flashcards
Gastroenteritis Presentation
vomiting and diarrhoea (3 or more loose stools a day), + abdominal pain/discomfort (can be quite severe if campylobacter), fever,
bloods in stool can be indicative of a bacterial infection
signs of dehydration:
thirsty, dry mucous membranes: mild, (<5% weight loss)
lethargic, reduced skin turgor, sunken eyes, sunken anterior fontanelle, tachycardia, reduced urine output, reduced tears: moderate (5-10% weight loss)
drowsy, absent urine output, prolonged capillary refill time, weak pulse, low BP (signs of hypovolaemic shock): severe (>10% weight loss)
Gastroenteritis Investigation / diagnosis
stool MC&S, urea and electrolytes
Gastroenteritis Management
oral rehydration therapy given frequently in small amounts; IV fluids if not tolerating oral/nasogastric fluids. Good handwashing to prevent spread. Notify public health if bacterial
Complications of campylobacter infection
Guillain-Barre
Reactive arthritis
What can predispose you to gastroenteritis?
HIV
Omeprazole
Presentation of CDIFF
mild diarrhoea to severe colitis
diarrhoea, fever, abdominal pain
Investigations for CDIFF
stools MC&S, FBC (increased WCC)
Treatment for C. Diff
metronidazole (first line), stool transplant, oral vancomycin (second line), fidaxomicin, surgery may be required, isolation, barrier nursing
prevention: stop AB (cephalosporin, clarithromycin, clindamycin, co-amoxiclav) (fluoroquinolones are also important in the development of c.diff)
Pass medicine note: Clindamycin is historically associated with causing Clostridium difficile but the aetiology has evolved significantly over the past 10 years. Second and third generation cephalosporins are now the leading cause of Clostridium difficile.
What are the complications of C.Diff?
pseudomembranous colitis, toxic megacolon, sepsis
What are the toxins that c.diff produces?
A (enterotoxin) and B (cytotoxin)
Presentation of infectious diarrhoea
fever, diarrhoea (may be bloody), nausea, dehydration, abdominal pain, bloody diarrhoea is more common with Campylobacter, Shigella
What is the diagnosis of infectious diarrhoea?
diagnosis by antigen detection
FBC, U&E, CRP, stool microscopy, culture and sensitivity (MC&S), blood cultures if septic
What is the management of infectious diarrhoea?
majority of cases are self-terminating and require rehydration and electrolyte correction: AB are considered in immunocompromised patients, the very young or the very septic; always liaise with microbiologists
What viruses can cause infectious diarrhoea?
adenovirus, rotavirus in children under 5 years
What are the complications of infectous diarrhoea?
renal failure, septic shock; E. coli is associated with the haemolytic-uraemic syndrome
What are the symptoms / presentation for giardia lamblia?
diarrhoea, malabsorption, failure to thrive
Giardiasis:
a patient develops persistent foul-smelling watery diarrhoea and weight loss after travelling to India. His symptoms have now lasted two weeks. He has no abdominal pain, nausea or fever
What is the investagation for giardia lamblia?
Cysts seen on stool microscopy
What is the treatment for giardia lamblia?
Metronidazole
How is giardia lamblia spread?
Contaminated water
Whet type of organism is giardia lamblia?
Parasite
What bacterium causes the majority of cases of travellers diarrhoea in developing countries?
Enterotoxigenic e.coli
What is the normal reservoir of Ecoli o157 (this is an enterohaemorrhagic bacterium)
2.5% of britich cattle secrete VTEC (verotoxin producing Ecoli)
The reservoir of infectio nis in the gut of herbivores.
The organism has an ectremely low infecting dose.
What are the symptoms of enterohaemorrhagi bacteria?
Initial watery diarrhoea
Becomes blood stained in 70% of cases. Associated with severe and often constant abdominal pain.
Little systemic upset, vomittin or fever.
What is the complication associated with Ecoli o157?
HUS
Haemolytic Uraemic syndrome
Who is affected by HUS?
HUS affects 10-15% of sufferers from this infection
Arises 5-7 days after the onset of symptoms
Most likely i nthe extremes of age, heralded by a high peripheral leucocyte count and may be induced particularly in chgildren by antibiotic therapy
What is the treatment for HUS?
Dialysis if necessary and may be averted by plasma exchange
Antibiotics should be avoided since they can stimulate toxin release.
What cells does the HIV virus attack?
Attacks the CD4 cells (T helper cells, macrophages and dendritic cells)
What are the features of the primary infection of HIV?
Usually symptomatic in more than 50% of cases
Incubation period is 2-4 weeks after exposure
Clinical features resemble a glandular fever type of illness (flu like symptoms - (presence of maculopapular rash and oral ulceration strongly suggests primary HIV infection rather than other viral casues of glandular fever.)
What is the progression of HIV after the primary infection?
Chronic phase which can last 2-10 years.
Depletion of CD4 cells and increase viral load
Clinical latelcy follows primary infection - individuals are asymptomatic.
Persistent lymphadenopathy less than 2cm diameter ius a common finding.
What is the differential diagnosis for primary HIV?
EBV
Primary cytomegalovirus infection
Rubella
Primary toxoplasmosis
Secondary syphilis
When does HIV become AIDS?
The development of specified opportunistic infections cancers and severe manifestations of HIV itself.
Can be diagnosed by having a CD4 count that is less than 200/mm3
CDC is the most used category of AIDS defining illnesses
CDC category A for HIV
Primary HIV infection
Asymptomatic
Persistent generalised lymphadenopathy
CDC category B for HIV
Candidiasis (oropharyngeal)
Fever / diarrhoea lasting for over one month
Oral hairy leucoplakia
Cervial dysplasia / carcinoma in situ
Idiopathic thrombocytopenic purpura
Peripheral neurupathy
CDC category C for HIV infection
Candidiasis of trachea, bronchi or lungs
Cervical carcinoma that is invasive
Cryptococcosis - extrapulmonary
Cytomegalovirus disease (outside the liver spleen and nodes)
Herpes simplex chronic ulcers or visceral
HIV encephalopathy
Kaposi’s sarcoma
Lymphoma (cerebral or B cell non hodgkin)
Pneumocystis pneumonia
Recurrent bacterial pneumonia
Cerebral toxoplasmosis
Tuberculosis
How is viral load determined?
Quantitive PCR of HIV - RNA
How is HIV diagnosed?
By detectiong host antibodies (either by point of care tests or by ELISA)
A positive antibody test from two different immunoasays is sufficiennt to confirm infection
Screening may involve testing for p24 antigen in addition to antibodies (incase antibody production hasn’t started yet)
Nucleic acid amplification (usually PCR) of HIV-RNA is carried out on children who’s mothers have had AIDS (the maternal antibodies will live in their system for 15 months and they might not have produced their own antibodies yet).
What are the aims of ART?
Reduce the viral load to an undetectable level for as long as possible
Improve CD4 count to over 200 cells/mm3 so that severe HIV-related disease is unlikely
Improve the quality of life without unacceptable drug toxicity
Reduce HIV transmission
What are the classes of antiretroviral drugs?
Nucleoside reverse transcriptase inhibitors (NRTIs)
Non-nucleoside reverse transcriptase inhibitors (NNRIS)
Protease inhibitors
Integrase inhibitors
Chemokine receptor inhibitor
Give examples for each type of ART
NRTI - abacavir, zidovudine
NNRTI - Efavirenz
PI - Atazanavir
Integrase inhibitors = Raltegravir
Chemokine receptor inhibitor = maraviroc
What is the standard antiretroviral regimen?
Two NRTI’s together
NNRTI
Protease inhibitor
or Integrase inhibitor
Most guidelines from high-income countries allow clonicians to choose a starting regimen of dual NRTIs combined with an NNRTI, or a PI or integrase inhibitor as these three regimens have a similar efficacy.
What must PI’s be co-prescribed with?
Must be co-prescribed with ritonavir - low doses oof ritonavir dramatically increase the concentrations and elimination half-lives of other PI’s by inhibitin gtheir metabolism by cytochroime P450. This increases drug exposure, reducing pill burden and dosing frequency - optimising adherence
When should ART therapy begin?
Following the 2015 BHIVA guidelines it is now recommended that patients start HAART as soon as they have been diagnosed with HIV, rather than waiting until a particular CD4 count, as was previously advocated.
Lymes Disease Presentation:
early: erythema chronicum migrans + systemic features (fever, arthralgia)
CVS: heart block, myocarditis
neuro: cranial nerve palsies, meningitis
What causes Lymes disease
Spirochaete Borrelia Burgdorferi
What is the investigation for Lymes disease?
NICE recommend that Lyme disease can be diagnosed clinically if erythema migrans is present
enzyme-linked immunosorbent assay (ELISA) antibodies to Borrelia burgdorferi are the first-line test
if this test is positive or equivocal then an immunoblot test for Lyme disease should be done
What are later complications of Lyme Disease?
Acrodermatitis chronica atroficans (ACA) - this is atrophy of the skin, often has involvement of the peripheral nervous system causing polyneuropathy
Lymphocytoma can also be caused (also chronic)
neuroborreliosis
What is the management of asymptomatic tick bites?
tick bites can be a relatively common presentation to GP practices, and can cause significant anxiety
NICE guidance does not recommend routine antibiotic treatment to patients who’ve suffered a tick bite
What is the management of Lymes disease?
Management of suspected/confirmed Lyme disease
doxycycline if early disease. Amoxicillin is an alternative if doxycycline is contraindicated (e.g. pregnancy)
ceftriaxone if disseminated disease
Jarisch-Herxheimer reaction is sometimes seen after initiating therapy: fever, rash, tachycardia after first dose of antibiotic (more commonly seen in syphilis, another spirochaetal disease)
What type of virus is Rabies?
RNA rhabdovirus (specifically a lyssavirus)
What are the features of Rabies?
prodrome: headache, fever, agitation
hydrophobia: water-provoking muscle spasms
hypersalivation
Negri bodies: cytoplasmic inclusion bodies found in infected neurons
What is the treatment for Rabies?
There is now considered to be ‘no risk’ of developing rabies following an animal bite in the UK and the majority of developed countries. Following an animal bite in at-risk countries:
the wound should be washed
if an individual is already immunised then 2 further doses of vaccine should be given
if not previously immunised then human rabies immunoglobulin (HRIG) should be given along with a full course of vaccination. If possible, the dose should be administered locally around the wound
What is the diagnostic test for rabies?
PCR to check for lyssavirus in the CSF
What is rat fever?
Leptospirosis
What are the clinical features of Influenza
2-4 days incubation period (1-7)
temperature up to 41° (38-40) for 3 days (1-5), 2 of the following:
cough (sore throat, rhinorrhoea),
myalgia,
headache,
malaise.
Predominance of systemic symptoms. Less common symptoms include tiredness, chills, headache, sore throat, runny nose, sneezing, nausea, vomiting, diarrhoea, loss of appetite, aching muscles, limb or joint pain
What is the treatment for influenza?
influenza A or B, both for treatment or prophylaxis, start within 48 hours of onset of symptoms/contact: oseltamivir, zanamivir
What are the complications of influenza?
common:
RESP: acute bronchitis, secondary bacterial pneumonia
less common:
RESP: primary viral pneumonia,
CV: myocarditis/pericarditis,
CNS: transverse myelitis/ Guillain Barre, myositis & myoglobinuria
What is tha pathogen associated with bronchiolitis?
RSV (respiratory syncytial virus) (75-80% of cases)
Mycoplasma and adenoviruses are also causes
Who often gets bronchioloitis?
Babies less than 1 years old = peak incidence is 3-6months
Maternal IgG protects gainst RSV
More common in winter
When is bronchiolitis more serious?
When there is bronchopulmonary dysplasia in premature babies
CF
Congenital heart disease
What are the features of bronchiolitis?
coryzal symptoms (including mild fever) precede:
dry cough
increasing breathlessness
wheezing, fine inspiratory crackles (not always present)
feeding difficulties associated with increasing dyspnoea are often the reason for hospital admission
When do NICE recommend immediate referral whenm there is a case of bronchiolitis?
apnoea (observed or reported)
child looks seriously unwell to a healthcare professional
severe respiratory distress, for example grunting, marked chest recession, or a respiratory rate of over 70 breaths/minute
central cyanosis
persistent oxygen saturation of less than 92% when breathing air.
When should clinicians refer to th hospital if there is a case of bronchiolitis according to NICE?
a respiratory rate of over 60 breaths/minute
difficulty with breastfeeding or inadequate oral fluid intake (50-75% of usual volume ‘taking account of risk factors and using clinical judgement’)
clinical dehydration.
What are the investigations for bronchiolitis?
immunofluorescence of nasopharyngeal secretions may show RSV
CXR: may show hyperinflation/patchy infiltrative change
What is management for bronchiolitis?
Largely supportive
humidified oxygen is given via a head box and is typically recommended if the oxygen saturations are persistently < 92%
nasogastric feeding may be need if children cannot take enough fluid/feed by mouth
suction is sometimes used for excessive upper airway secretions
CPAP/ ventilation if severe
Ipratropium inhalers may help
Palivizumab (monoclonal Ab) given monthly as primary prophylaxis during RSV season to at-risk infants (ie: chronic lung disease, congenital heart disease)
What are the complications of bronchiolitis?
chronic wheeze, bronchiolitis obliterans (adenovirus)
What organism causes amoebic dysentry?
Entamobea Histolytica
What organism is most likely to cause invasive pulmonary aspergillosis?
A. fumigatus
What are the risk factors for invasive aspergillosis?
Neutropenia
Solid organ or allogenic stem cell ttransplant
Corticosteroids
Leukaemia and other haemotological malignancies
Cytotoxic chemotherapy
Advanced HIV disease
Severe COPD
Critically ill patients on intensive care units
Chronic granulomatous disease
What are the findings on CT that would indicate invasive pulmonary aspergillosis?
Dense, well circumscribed lesions with or without a halo sign
Air crescent sign
Cavity
When is an immunocompromised patient heavily suspected of having invasive pulmonary aspergillosis?
If they develop fever, new resp symptoms, (particularly pleural pain or haemoptysis) or a pleural rub.
What are the features of tracheobronchial aspergillosis?
Involvement is characterised by the formation of fungal plaques and ulceration
What are mycological ways to diagnose aspergillosis?
Using sputum, BAL fluid or bronchial brush to find one of the following:
Fungal elements indicating mould of aspergillus
Culturing a mould of aspergillosus
What blood test can be done to look for invasive pulmonary aspergillosis?
Detection of aspergillus cell wall components (galactomannan and B-1,2-glucan) in blood or BAL fluid and aspergillus DNA by PCR.)
What is treatment choice for invasive pulmonary aspergillosis?
Voriconazole
Second line agents include liposomal amphotericin, caspofungin or posaconazole.
What is sub-acute or chronic pulmonary aspergillosis?
Non-invasive complication of chronic lung disease such as COPD, TB, opportunistic mycobacterial disease or fibrotic lung disease
What disease does chronic pulmonary aspergillosis closely mimic?
TB
What are the features of chronic pulmonary aspergillosis?
Cough (with or without haemoptysis), weight loss, anorexia and fatigue over months or years
Associated fever, night sweats and elevated inflammatory markers
What are radiological features of chronic or subacute pulmonary aspergillosis?
Thick walled - cavities (predominantly apical)
Pulmonary infiltrates
Pleural thickening and later fibrosis
What are the three different dsecriptive names of chronic pulmonary aspergillosis?
CNPA (chronic necrotising)
Cavitatory
Fibrosing
What are the features of malaria?
fever
rigors
aching bones
adbo pain
headache
dysuria
frequency
sore throat
cough
fatigue
myalgia
nausea
vomiting
Signs:
none, splenomegaly, hepatomegaly, mild jaundice, anaemia, tachycardia
What are the investigations for malaria?
thick and thin blood films (Giemsa, Field’s stain)
schizonts on a blood film
quantitative buffy coat (QBC) - this is a fluorescence microscopy based malaria diagnostice test
rapid antigen tests (OptiMal and parasight F)
FBC (anaemia), raised ESR, raised CRP, U&E, LFT
What are the organisms that cause malaria?
Plasmodium falciparum
Plasmodium vivax
Plasmodium ovale
Plasmodium malariae
Plasmodium falciparum causes nearly all episodes of severe malaria. The other three types, of which Plasmodium vivax is the most common, cause ‘benign’ malaria
What are protective factors for malaria?
G6PD deficiency
HLA-B53
absence of Duffy antigens
Sickle cell anaemia
What are the features of severe malaria?
schizonts on a blood film
parasitaemia > 2%
hypoglycaemia
acidosis
temperature > 39 °C
severe anaemia
complications as below
What are the complications of malaria?
Complications
- cerebral malaria: seizures, coma
- acute renal failure: blackwater fever, secondary to intravascular haemolysis, mechanism unknown
- acute respiratory distress syndrome (ARDS)
- hypoglycaemia
- disseminated intravascular coagulation (DIC)
What might make you more likely to suffer from malaria?
Pregnancy
Previous splenectomy