HACEK organisms Flashcards
What does HACEK stand for?
Haemophilus spp. (influenzae, para inf, hemolyticus, para hemo)
Aggregatibacter spp. (segnis, aphrophilus, actinomycetemcomitans)
Cardiobacterium hominis
Eikenella corrodes
Kingella kingae
What are the HACEK organisms known for?
*Commensals of the human oropharynx-typically cause opportunistic infections
*FASTIDIOUS meaning they are slow-growing and require specific conditions to grow
*GRAM NEGATIVE RODS
*Rarely associated with SUBACUTE infective endocarditis (<1-3%)
*May also cause BSI, abscesses around head and neck (similar to S. angionosus)
Haemophilus species grow on what?
Chocolate agar because it has hemin (from lysed RBCs) and NAD
nicotinamide adenine dinucleotide-celullar resp
Characteristics of Haemophilus influenzae on a gram stain?
Gram negative
Tiny cocco bacilli
Requires NAD and Hemin so only grows on chocolate
Easily decolorize and may be overlooked
What diseases does Haemophilus influenzae
cause?
Mainly causes disease in children <5 yr old or adults >65
Ear and eye infections- Otitis and conjunctivitis
Epiglottitis
Meningitis
Bloodstream infection
Pneumonia
A normal flora of the resp tract
Is there a vaccine against Haemophilus influenzae?
YES
Vaccines reduced TYPE B (meningitis) infections significantly since early 90s.
Strains without a capsule are non-typeable
If a patient has been vaccinated and still gets sick, the first suspicion is decreased immune responses
Haemophilus parainfluenzae
Higher rates of infective endocarditis compared to H. influenzae!!
Requires NAD, but not hemin
Only grows on chocolate
causes similar diseases as H. influenzae:
Otitis and conjunctivitis (mostly children)
Epiglottitis
Bloodstream infection
Meningitis
Infectious/septic arthritis
Pneumonia
Culture characteristics of Aggregatibacter spp. and name the 3 spp
- Grow on BAP and CAP
- Small colonies with brown star center, look like nips
- on gram stain the cells may aggregate and look like artifacts
A. actinomycetemcomitans
A. aphrophilus
A. segnis
Which Aggregatibacter species is most commonly isolated from abscesses, especially in oral cavity and oropharynx?
Aggregatibacter aphrophilus!
Which Aggregatibacter species is a caustive agent of periodontal disease and causes aggressive periodontal disease? Teeth loss in months!
Aggregatibacter actinomycetemcomitans
Cardiobacterium hominis
- forms star shaped clumps
*infective endocarditis
*grows on BAP and CAP
Eikenella corrodens
- most commonly associated with abscesses involving HUMAN BITES. (clenched-fist injury)
- other oral microbes (strep) may be present too in bites
*common in patients with cancers of the head and neck
*also common in insulin-dep diabetics and IVDU who lick needles
*colonies on CAP are flat and spready
How Is Kingella kingae detected?
PCR of synovial fluid only!
Disease associated with Kingella kingae?
Septic arthritis from hematogenous spread from oropharynx.
Most common in 6mon-5 year olds
May be spread from person to person
When to suspect HACEK organisms in endocarditis?
1) Subacute endocarditis presentation
2) Risk factors (IVDU, prosthetic valve, poor dentition)
3) Poorly staining, delicate Gram-negatives with characteristic arrangements in blood culture
(culture negative endocarditis)
4) No growth on MacConkey
