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Micro - Haemophilus influenza (intro (colonises upper resp tract…
Micro - Haemophilus influenza
haemophilus spp
pleomorphic gram -ve bacilli/coccobacilli
stain faintly
facultative anaerobes (for max growth add 5% CO2)
fastidious
have special nutritional requirements
factor X (haemin) or factor V (NAD) or both - present in blood
typically visible colonies after overnight incubation
intro
notifiable
causes RTIs, meningitis, BSI
NOT A CAUSE OF INFLUENZA
needs both X and V factors
2 strains: capsulated + non-capsulated
colonises upper resp tract (nasopharynx) of healthy people
5% carry capsulated
25-80% carry non-capsulated
human only
increased risk of infection: under 4y/o, immunocompromised
spread via inhalation of resp droplets + direct contact with resp secretions
capsulated type
virulent
severe
facilitates invasion + haemotogenous spread
6 strains (a-f)
typed using antisera against specific polysaccs
type B (Hib)
vaccine preventable
purified capsular polysacc conjugated with protein carrier
@ 2,4,6 months + booster @ 13 months
routine in Ire
most associated with systemic disease
due to PRP (polyribosyl ribitol phosphate)
no Ig-PRP complex to activate complement
antiphagocytic polysacc in capsule
meningitis
sequelae = intellectual disabilities, deafness, seizures
if intxed mortality = 90%
cellulitis
RTIs in early childhood (acute epiglottitis + pneumonia)
sepsis (often secondary to meningitis)
septic arthritis
attaches to cells via pili + fibriae
non-capsulated type
less invasive
mainly resp + mucosal infections
acute + chronic otitis media
recurrent sinusitis
CAP
exacerbation of acute + chronic bronchitis
esp in patients with chronic pul disease (COPD/CF)
impaired cilia + increased mucous predispose to biofilm formation + bacterial invasion
also in patients with recent/current viral infection
no vaccine
Dx
blood for culture + PCR
CSF
if visibly turbid = bacterial meningitis
culture
PCR
microscopy
joint fluid in septic arthritis
aspirate area of cellulitis
do antibiotic susceptibility testing too
laryngeal/epiglottic swab for culture
contraindicated in young children (may precipitate airway obstruction)
Tx
20% produce beta-lactamases
inpatient
IV co-amoxiclav (combination of amoxicillin, a β-lactam antibiotic, + potassium clavulanate, a β-lactamase inhibitor) for RTI
IV 3GC (cefotaxime/ceftriaxione) for meningitis/BSI
outpatient: oral co-amoxiclav or macrolide (azithromycin/clarithromycin)
Other haemophilus strains
H ducreyi
causes chancroid (STI)
Aggregatibacter aphrophilus
HACEK
unusual cause of endocarditis
colonises upper resp tract