Respiratory infections Flashcards
What are parameters of CURB65 score?
Confusion Urea >7 RR >30 BP - systolic <90 or diastolic <60 Age >65
not validated for use in immunocompromsied patientd
What is risk of mortality for these CURB65 score?
0 or 1
2
3-5
0 or 1 - low risk, community treatment
2 - intermediate 3-15% risk mortality. Consider hospital care
3-5 - high risk. >15% mortality. May need ITU support
How long can legionella urinary antigen test remain positive?
Can remain positive for few weeks, even after being antibiotics. So can still be useful as diagnostic tool
only detects serotype 01
When should we suspect atypical pathogens?
in outbreak settings
infections in otherwise healthy individuals
atypicals - legionella, mycoplasma, chlamydia spp
Patients with COPD.
What are indications for long term antibiotic prophylaxis?
frequent exacerbations with sputum production
prolonged exacerbations
exacerbations requiring hospitalization
What are risks of influenza in pregnancy?
miscarriage
small-for-gestational age
increased risk of severe infection requiring ITU support
risk of secondary bacterial infection
21 year old returns from Saudia Arabia, with fever, cough, SOB.
CXR shows bilateral pulmonary infiltrates
What are potential diagnoses?
MERS-CoV
SARS-CoV
Hanta virus pulmonary syndrome
influenza - including avian influenza
Legionella
Mycoplasma
Coxiella burnetti
Chlamydia spp
Cryptococcus
Histoplasma
Tularaemia
Melioidosis
21 year old returns from Saudia Arabia, with fever, cough, SOB.
CXR shows bilateral pulmonary infiltrates
Tests positive for influenza. What are next steps?
Continue respiratory precautions
send for flu typing - assess for H5N1 or H7N9
treat with oseltamivir 75mg BD 5 days
in TB treatment, when is it considered
MDR-TB
XDR-TB
MDR-TB - if resistant to both isoniazid and rifampicin
XDR-TB - resistant to above, plus fluoroquinolone, plus injectable e.g amikacin
What are quick tests which can give idea about TB resistance in sample?
Gene Xpert (Cepheid) firstly confirms M. TB present
sputum processed to detect major mutation in rpoB, which accounts for 98% resistance against rifampicin
42 year old man with 18 weeks history of cough. CXR normal
Suspect pertussis.
Patient has had all vaccinatons in childhood
Wife is 36 weeks pregnant
How to diagnose pertussis?
Nasopharyngeal culture/ PCR
Pertussis IgG - if raised can suggest recent infection, as long as not immunised in past year
Clinical diagnosis - “whoop” cough or paroxysms of cough, for >14 days
42 year old man with 18 weeks history of cough. CXR normal
Suspect pertussis.
Patient has had all vaccinatons in childhood
Wife is 36 weeks pregnant
What is treatment?
Antibiotics reduce transmission, and so mostly used as public health measure
azithromycin 5 days
co-trimoxazole 14 days
no benefit is started after 21 days of symptoms
42 year old man with 18 weeks history of cough. CXR normal
Suspect pertussis.
Patient has had all vaccinatons in childhood
Wife is 36 weeks pregnant
Children aged 6 + 8 at home
What prophylaxis is recommended for family?
Prophylaxis for all household contacts, who have had contact within 21 days of patient, and at risk e.g health conditions, pregnant, unvaccinated. Combination of antibiotics and vaccination
Do not need prophylaxis if had vaccine booster within past 5 years
- Children vaccinated ages 2, 3, 4 months - would not require antibiotic prophylaxis, as vaccinated
- Unvaccinated, or no recent vaccination - give antibiotics, and vaccinate
- Pregnant mother - erythromycin safer in pregnancy. Mother should have had pertussis booster during pregnancy
Patient with pertussis
What are treatment options with someone with protracted cough?
Very little evidence, but these have been tried -
corticosteroids
b-eta agonists
antihistamines
pertussis immunoglobulin
What are benefits of using Taz/ gent in neutropenic sepsis?
Normally neutropenic as on chemotherapy, so at risk of certain organisms
Antibiotics will cover most organisms including pseudomonas
Patient with AML. Presents SOB - treated for neutropenic sepsis
CT chest shows patchy consolidation bilaterally, nodules, and halo sign
What are possible diagnoses?
Non-infective -
pulmonary oedema
leukaemic infiltration
drug toxicity
Viral - Influenza RSV parainfluenza adenovirus CMV
Chlamydia
Mycoplasma
Legionella
PCP
Cryptococcal
Nocardia
Aspergillus - nodules, halo sign, air crescent, all suggest angioinvasive aspergillus infection
How to diagnose pulmonary aspergillus infection?
BAL
culture for fungi
Beta-2-glucan
galactomannan
aspergillus PCR
PCP PCR
What is treatment of choice for pulmonary aspergillus?
Voriconazole
Ambisome
capsofungin
23 year old with CF.
Increase SOB.
Known colonised with pseudomonas and staph aureus
Recent sputum grew Stenotrophomonas maltophilia
What is the significance of this?
Stenotrophomonas maltophilia was originally classified as a pseudomonas, and is an environmental bacteria found in soil. Gram negative, non-fermenter
Resistant to beta-lactams and carbapenems
recognised as opportunistic pathogen in immunocompromised
Patient with CF, what bacteria do we need to look for in sputum?
These species require special testing
pseudomonas
S maltophilia
Haemophilus influenzae
Staph aureus
Burkholderia
Aspergillus
TB
Fungi
If sputum culture psoitive, difficult to know if this organism is colonising airway, or causing infection
in CF patients, inhaled antibiotics can be used
What are examples of this?
What are benefits?
Colistin tobramycin aztreonam levofloxacin amikacin
antibiotics get directly to site of infection - higher concentration
less systemic side effects
What is rationale behind isolating CF patients on hospital admission?
Reduce their risk of exposure to infections
CF patient may have multidrug resistant organism e.g pseudomonas, so prevents spread of this
Cryptococcus can cause pulmonary infection in immunocompromised.
What are two species?
C neoformans - associated bird droppings
C gattii - associated with trees and surrounding soil
Any patient with pulmonary cryptococcus should have lumbar puncture to see if any CNS involvement. As this influences duration of treatment
What is treatment for cryptococcal infection?
Ambisome and flucytosine
fluconazole maintenance for 6-12 months
Blood culture machine flags positive, but no organism seen on gram stain.
Patient being treated for LRTI
What is possible explanation?
Strep pneumoniae do not culture well. Bacteria die, and do not gram stain well
Consider sending streptococcal urinary antigen test to clarify
How to differentiate strep pneumoniae from other streptococci biochemically?
Gram pos cocci
alpha-haemolysis
susceptibility to optochin - viridans group strep are resistant
Which organisms are most common cause of sinusitis/ otitis media?
Strep pneumoniae
Haemophilus influenzae
Moraxella catarrhalis
Which organisms cause otitis externa?
staph aureus
pseudomonas
relatively benign condition, but can become malignant otitis externa, and spread from ear to temporal bone. Occurs in diabetics/ immunocompromised
What are most common causes of conjunctivits?
Adenovirus
HSV
VZV
Strep pneumoniae
Haemophilus influenzae
Moraxella catarrhalis
Chlamydia trachomatis - neonates
Epiglottitis is life threatening emergency, usually children?
What are common causes?
Haemophilus influenzae - most common
Strep pneumoniae
Staph aureus
incidence decreasing with use of Hib vaccine
Which viruses cause “common cold”
rhinoviruses
enteroviruses
coronaviruses
adenoviruses
Which viruses cause croup?
parainfluenza is most common cause
RSV
influenza
parainfluenza
metapneumovirus
croup is severe URTI seen in children
RSV most common cause bronchiolitis
What are benefits of antibiotics in GAS pharyngitis?
Reduce risk of sequelae
Reduce durations of symptoms
Reduce transmissibility e.g between school children
Why does GAS infection in throat/ skin have different outcomes for long term sequeale?
> 150 types of GAS, with different M antigen on cell wall
M1/ M3 associated rheumatic fever
M12/ M49 associated glomerulonephritis
rheumatic fever only follows after pharyngitis, and never after skin infection. This is thought to be due to different M type causing infection. Occurs 1-5 weeks after initial infection
glomerulonephritis can occur after pharyngitis/ cellulitis
GAS pharyngitis
What is cause of associated skin rash?
Scarlet fever
Due to Streptococcal pyrogenic exotoxin (SPE) A-C, having a super-antigen effect
GAS
What is included in Centor score?
score used in pharyngitis symptoms for 3 days or less
score out of 5
Age <13
Exudate on tonsils
Lymphadenopathy
Cough
Temp >38.0 degC
Child with GAS confirmed, and starting treatment.
Who requires close contact prophylaxis?
No prophylaxis - close contacts asymptomatic
Symptomatic contacts should be treated
What is treatment of GAS?
Amoxicillin
Erythromycin
Azithromycin
CAP
Blood culture positive
What are features to help classify colony as strep pneumoniae?
gram
catalase
haemolysis
optochin susceptibility
gram pos
catalase neg
haemolysis - alpha
optochin susceptibility - susceptible
Sputum culture
What are cut offs for neutrophils and epithelial cells per low powered field?
> 25 neutrophils
<10 epithelial cells
high epithelial cell number suggests oropharyngeal contamination,. So difficult to assess if organism causing infection or not
What is are the major virulence factors of strep pneumoniae?
polysaccharide capsule - allows it to evade phagocytosis
pneumolysin - acts on alveoli causing direct damage leading to oedema/ inflammation
What are steps to help prevent pneumococcal infection?
23-valent polysaccharide vaccine
prophylactic antibiotics for those who cannot have vaccine/ vaccine wont work e.g splenectomy
Patient with three pneumoccocal infections in 2 months. Each treated with antibiotics.
What are possible explanations for this?
Wrong diagnosis - unlikely in this case
Wrong treatment - resistance
Wrong treatment - duration of treatment too short
Complication - abscess not adequately penetrated by antibiotics
Re-infection - possible common source. Less likely with pneumococcal
Bordetella pertussis is bacteria, but blood tests often reveal lymphocytosis.
Why is this?
Pertussis disease is mediated by toxins
Lymphocytes increase in response to toxins
Lymphocytosis is classical feature of pertussis infection
What are diagnostic tests for pertussis?
Often based on clinical history
Sputum/ NPA taken within first 14 days - culture and PCR
What are three stages of pertussis infection?
catarrhal - similar flu like symptoms to any URTI
paroxysmal
convalescent
Pertussis disease is toxin mediated.
What are benefits of antibiotics?
Reduce bacterial load, which reduces symptom duration, and transmission rate
What is treatment of pertussis?
When does it need to be started?
Macrolides
need to start treatment within 21 days
Pertussis
From public health perspective, how long do children need to be off school?
Children with suspected, epidemiologically linked or confirmed pertussis should be excluded from schools or nurseries for five days from commencing appropriate/ recommended antibiotic therapy or for 21 days from onset of symptoms (in those who are not treated)
When is pertussis vaccine given?
8 weeks
12 weeks
16 weeks
causing most severe disease in young children, so given early
DTaP/IPV/Hib/HepB combination vaccine
Pertussis
What are hospital infection control policies?
droplet precautions - highly communicable
until had 5 days of antibiotics
or until 21 days after symptom onset
