respiratory tract infections Flashcards
what are the the common normal microbiota of the RT?
(common >50% of people)
- bacteroides spp.
- Candida albicans
- oral streptococi
- haemophilus influenza
what are the normal microbiota of the RT found in the latent state in in tissues?
- herpes simplex virus type I
- epstein Barr Virus
- cytomegalovirus
- mycobacterium
what are the normal microbiota of the RT that are only occasionally found?
(occasional <10% in normal people)
- streptococcus pypgenes
- streptococcus pneumoniae
- neisseria meningiditis
what are the main respiratory tract host defences?
- saliva
- mucus
- cilia
- nasal secretions
- antimicrobial peptides
- alveolar macrophages
what are examples of the normal microbiota found in the nasal passages and sinuses?
- fermicutes
- actin bacteria
- staphylococcus epidermis
- haemophilus spp
- staphylococcus aureus
what are the normal microbiota found in the oral pharynx?
- prevotella
- fusobacterium
- candida spp
- haemophilus
- neisseria
- streptococcus
what are the normal microbiota found in the Lower respiratory tract?
- pseudomonas
- streptococcus
- prevotella
common cold:
actual name?
tranmission?
causative agents?
seasonal?
name = acute coryza
transmission = aerosol, virus- contaminated hands
causative agents = 40% rhinovirus (>100 serotypes)
30% coronaviruses (>3 serotypes)
coxsackie virus A
Echovirus
Parainfluenza
seasonal = early autumn and mid/late spring
why are colds less common in summer?
because uV light tends to kill the pathogens.
clinical features of common cold?
- tiredness
- slight pyrexia
- malaise
- sore nose & pharynx
- profuse, watery nasal discharge
- sneezing in early stages
- secondary bacterial infection occurs in minority
describe the pathogenesis of the common cold?
what are the viral and bacterial causative agents for acute pharyngitis and tonsillitis?
virus:
- Epstein-Barr virus
- cytomegalovirus
- HSV1
- rhinovirus
- coronavirus
- adenovirus
bacteria:
- streptococcus pyogenes
- haemophilus influenza
describe the cytomegalovirus (CMV)
- transmission in body secretions and organ transplants
- usually asymptomatic
- virus can reactivate and cause disease when cell-mediated immunity is compromised
- diagnose secondary infection using IgM in the blood
- diagnose CMV pneumonitis using CMV Ag in BAL
- treatment with ganciclovir, foscarnet, cidofovir
describe Epstein- Barr virus?
- replicated specifically in B lymphocytes (CD21)
- causes glandular fever
- transmitted by saliva and aerosol
- usually occurs in 2 peaks:
1-6 years old
14-20 years old
incubation period: 4-8 weeks
illness= 4-14 days
clinical features of glandular fever?
- fever
- headache
- malaise
- sore throat
- anorexia
- palatal petechiae
- cervical lyphadenopathy
- mild hepatitis
- swollen tonsils
- white exudate
- petechiae on the soft palate
tonsilitis:
causes
transmission?
treatment?
caused by= streptococcus pyrogenes
tranmission= by airborne droplets and contact
- confection occurs mainly in children
- 15-20% become asymptomatic carriers
- treat with penicillin
what does strep. progenies havee an increasing resistance to in tonsillitis?
erythromycin and tetracycline
clinical features of tonsillitis?
- fever
- pain in throat
- enlargement of tonsils
- tonsils lymphadenopathy
streptococcus pyogenes
- group A streptococcus
- gram positive cocci in chains
- cultured in blood agar
- haemolytic activity ue to exotoxin streptomycin
- susceptible to treatment with penicillin
complications of streptococcus pyogenes ?
parotitis?
- caused by mumps virus
- paramyxovirus family
- transmission by droplet spread and fomites
- communicable in 2 days before disease onset
- diagnosis is based on clinical features - IgM serology can be performed in doubtful cases from saliva, CSF or urine.
who does parotitis normally effect?
clinical features?
- primarily effects school aged children and young adults
- clinical features:
- fever
- malaise
- headache
- anorexia
- trismus
- severe pain and swelling of parotid glands
parotits:
treatment?
prevention?
complications?
treatment:
- mouth care
- nutritional
- analgesia
prevention:
- active immunisation
- measles mumps rubella vaccine (MMR)
complications:
- CNS involvement
- epididymo orchitis
acute epiglottis?
- caused by haemophilus influenza
- most often seen in young children
- 88% reduction in England and Wales since advent of Hib vaccine in 1992
clinical features of acute epiglottis?
- high fever
- massive oedema of the epiglottis
- severe airflow obstruction resulting on breathing difficulties
- bacteraemia
haemophilus influenza
how to diagnose acute epiglottisis
- do not examine throat or take throat swabs as this will precipitate obstruction of airway
- blood cultures to isolate H influenza
treatment of acute epiglottis?
- life threatening emergency
- requires urgent endotracheal intubation
- intravenous antibiotics (ceftriiaxone or chloramphenicol)
diphtheria?
- rare in developed countries as a result of vaccination
- usually a childhood disease
- may affect adults in countries where childhood vaccination uptake is poor
- present in 3-5% of healthy throats
- incubation 2-7 days
clinical diphtheria?
- sore throat
- fever
- formation of pseudomembrane
- lymphadenopathy
- oedema of anterior cervical tissue (bull neck)
diphtheria?
diagnosis:
treatment:
prevention:
diagnosis= made on clinical ground as therapy is usually urgently required
treatment=
- prompt anti-toxin therapy administered intramusculary
- concurrent antibiotics
- strict isolation
prevention:
- childhood immunisation with toxoid vaccine
- booster dose given if travelling to endemic area if > 10 years have elapsed since primary vaccine
corynebacterium diptheriae?
-
what are the 2 subunit toxins of corynebacterium diphtheria?
Subunit A = ACTIVE, responsible for clinical toxicity
Subunit B = (Binding), transports toxin to receptors on myocardial and peripheral nerve cells
laryngitis and tracheitis:
- where may these infections spread down from?
-what are its usual origins?
- what will it cause in adults?
- what will it cause in children?
what bacteria will cause whooping cough?
bordetella pertussis
what is the spread of whooping cough like?
- 90% cases in children <5 years old
- > 50 million cases worldwide annually
- 600,000 deaths world wide annually
- uncommon in developing countries
how is whooping cough spread and what is the incubation period?
transmission is by airborne droplets
incubation period is 1-3 weeks
clinical features of whooping cough?
2 stages?
- catarrhal stage (1 weeks)
- paroxysmal stage (1-4weeks)
catarrhal stage:
- highly contagious
- malaise
- mucoid rhinorrhoea
- conjunctivitis
PARYOXYSMAL STAGE OF WHOOPING COUGH?
1-4 weeks
- paroxysms of coughing with a classic inspiratory “whoop”
- lumen of respiratory tract is compromised by mucus secretion and mucosal edema.
Diagnosis of whooping cough?
- clinically by characteristics”whoop”
- bacterial isolation from nasopharyngeal swabs
- nucleic acid amplification tests (NAATs)
treatment and prevention of whooping cough?
treatment:
- in catarrhal stage can be treated with erythromycin
- in paroxysmal stage, antibiotics have no effect
- isolation
- supportive care.
prevention:
- vaccination (whole cell vaccine)
bordetella pertussis
- gram negative aerobic coccobacillus
- human pathogen
- attaches to and replicated in the ciliated respiratory epithelium
- does not invade deeper structures
- specific attachment is due to surface components
what are toxic factors if the bordetella pertussis?
- pertussis toxin
- adenylate cyclase toxin
- tracheal cytotoxin
- endotoxin
describe the incidence of whooping cough?
- whole heat killed vaccine introduced in 1958
- epidemics at approx 4 year intervals
- concern over vaccine side effects led to reduced vaccine uptake and large epidemic in 1978-9.
acute bronchitis?
due to what infections?
due to what secondary infections?
- inflammation of the trachaebronchial tree
- usually due to infection:
rhinovirus
coronavirus
adenovirus
mycoplasma pneumoniae
secondary infection:
- streptococcus pneumoniae
- haemophilus influenza
what is chronic bronchitis characterised by?
- characterised by a cough and excessive mucus secretion in tracheobronchial tree
- not attributed to a specific disease such as TB, bronchiectasis, asthma.
- anatomical disturbances of the respiratory system:
- immune deficit- SCID
- ciliary deficit: kartegener syndrome, smoking
- excessively thick mucus: cf
bronchiolitis
- restricted to children to <2 years
- bronchioles have such a fine bore
- infection may lead to epithelial cell necrosis
- mainly caused by RSV (75%)
what bacteria will cause pneumonia?
streptococcus pneumoniae
pneumonia?
inflammation of the substance of the lungs
describe the characteristics on pneumonia ?
- confirmed on chest radiograph
- most common cause of infection related death in the Uk and USA
- caused by a wide range of micro organisms
- indistinguishable symptoms.
- laboratory identification of microbial cause is challenging
- access to LRT by inhalation of aerosolised microbes or by aspiration of normal flora of the URT
describe the difference in pneumonia is children and adults?
children:
- mainly viral
- notates may develop pneumonia cause by chlamydia trachomatis acquired Fromm mother during brith
adults:
- mainly bacterial
- aetiology varies with age, underlying disease, occupational and geographic risk.
aetiology classification:
viral pneumonia, common causes?
aetiology classification:
bacterial pneumonia- common causes?
what are bacteria associated with atypical pneumonia- variants that fail to respond to treatment with penicillin?
anatomical classification of pneumonia?
- lobar pneumonia:
involvement of distinct region of the lung
bronchopneumonia:
- diffuse, patchy consolidation
- associated with bronchi and bronchioles
interstitial pneumonia:
- invasion of lung interstium
- usually characteristic of viral infection
necrotising pneumonia:
- lung abscesses and destruction of parenchyma
streptococcus pneumonia clinical features:
initially?
followed by?
initially=
- abrupt onset
- rigors
- fever
- malaise
- tachycardia
- dry cough
followed by=
- productive cough with rust sputum
- spiky temp
- lobular consolidation
clinical features of mycoplasma pneumonia?
- fever
- dry cough
- dyspnoea
- lymphadenopathy
haemophilus influenza clinical features
- mainly occurs in children
- consolidation or patchy bronchopneumonia
- persistent purulent sputum and malaise
legionella pneumophila:
cause
clinical features
laboratory diagnosis of legionnaires disease?
measles
- clinical features
- one of the leading causes of death globally
clinical features:
- fever
- runny nose
- koplik’s spots
- characteristic rash
- may result in neurological complications
- can cause giant cell (Hecht’s) pneumonia in the immunocompromised - usually fatal
measles virus
- paramyxovirus
- spread via aerosol
- multisyetm infection
- replicates in LRT
- incubation 10-14 days
measles:
diagnosis
treatment
prevention
diagnosis =
serology for measles specific IgM
- virus isolation
- viral RNA detection
treatment:
- if severe, ribavirin treatment
- antibiotics for secondary bacterial infections
prevention:
- immunisation with highly effective, live, attenuated MMR vaccine
3 types of influenza
endemic
epidemic
pandemic
what are the genetic changes that influenza will undergo during the
