HACEK organism
Encyclopedia
A HACEK organism is one of a set of slow-growing Gram negative bacteria
that form a normal part of the human flora.
They are a frequent cause of endocarditis
in children.
involving native valves and are the most common gram-negative cause of endocarditis among people who do not use IV drugs. They have been a frequent cause of culture-negative endocarditis. Culture negative refers to an inability to produce a colony on regular agar plates; this is because these bacteria are fastidious (require a specific nutrient).
In addition to valvular infections in the heart, they can also produce other infections such as bacteremia, abscess, peritonitis, otitis media
, conjunctivitis, pneumonia, arthritis and osteomyelitis, and periodontal infections.
, a third generation cephalosporin
(penicillin
-based) antibiotic. Ampicillin
(a penicillin
) and low-dose gentamicin
(an aminoglycoside
) is another therapeutic option.
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
that form a normal part of the human flora.
They are a frequent cause of endocarditis
Endocarditis
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or even on intracardiac devices...
in children.
Organisms
The name is formed from their initials:- HaemophilusHaemophilusNot to be confused with Haemophilia.Haemophilus is a genus of Gram-negative, pleomorphic, coccobacilli bacteria belonging to the Pasteurellaceae family. While Haemophilus bacteria are typically small coccobacilli, they are categorized as pleomorphic bacteria because of the wide range of shapes they...
(Haemophilus parainfluenzaeHaemophilus parainfluenzaeHaemophilus parainfluenzae is a species of Haemophilus.It is one of the HACEK organisms....
) - AggregatibacterActinobacillusActinobacillus is a genus of gram-negative, immotile and nonspore-forming, oval to rod-shaped bacteria occurring as parasites or pathogens in mammals, birds, and reptiles. It is a member of the Pasteurellaceae family. The bacteria are facultatively aerobic or anaerobic, capable of fermenting...
(Aggregatibacter actinomycetemcomitansAggregatibacter actinomycetemcomitansAggregatibacter actinomycetemcomitans is an oral commensal found also in severe infections in the oral cavity, mainly the periodontium. A. actinomycetemcomitans, previously Actinobacillus actinomycetemcomitans, is a gram negative facultative non-motile rod. It is also associated with non-oral...
, Aggregatibacter aphrophilus) - Cardiobacterium hominisCardiobacterium hominisCardiobacterium hominis is a Gram-negative rod commonly grouped with other bacteria into the HACEK group. It is one of several bacteria normally present in the respiratory tract. However, it may also rarely cause endocarditis, an infection of the heart valves.-Microbiology:C. hominis is a...
- Eikenella corrodensEikenellaEikenella corrodens is a fastidious gram-negative facultative anaerobic bacillus. It was first identified by M. Eiken in 1958, who called it Bacteroides corrodens.-Microbiology:...
- Kingella (Kingella kingaeKingella kingaeKingella kingae is a species of gram-negative aerobic coccobacilli. First isolated in 1960, it was not until the 1990s that culture techniques improved enough for it to become recognized as a significant cause of infection in young children...
)
Presentation
All of these organisms are part of the normal oropharyngeal flora, which grow slowly, prefer a carbon dioxide–enriched atmosphere, and share an enhanced capacity to produce endocardial infections, especially in young children. Collectivelly they account for 5-10% of cases of infective endocarditisEndocarditis
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or even on intracardiac devices...
involving native valves and are the most common gram-negative cause of endocarditis among people who do not use IV drugs. They have been a frequent cause of culture-negative endocarditis. Culture negative refers to an inability to produce a colony on regular agar plates; this is because these bacteria are fastidious (require a specific nutrient).
In addition to valvular infections in the heart, they can also produce other infections such as bacteremia, abscess, peritonitis, otitis media
Otitis media
Otitis media is inflammation of the middle ear, or a middle ear infection.It occurs in the area between the tympanic membrane and the inner ear, including a duct known as the eustachian tube. It is one of the two categories of ear inflammation that can underlie what is commonly called an earache,...
, conjunctivitis, pneumonia, arthritis and osteomyelitis, and periodontal infections.
Treatment
The treatment of choice for HACEK organisms in endocarditis is ceftriaxoneCeftriaxone
Ceftriaxone is a third-generation cephalosporin antibiotic. Like other third-generation cephalosporins, it has broad spectrum activity against Gram-positive and Gram-negative bacteria. In most cases, it is considered to be equivalent to cefotaxime in terms of safety and efficacy...
, a third generation cephalosporin
Cephalosporin
The cephalosporins are a class of β-lactam antibiotics originally derived from Acremonium, which was previously known as "Cephalosporium".Together with cephamycins they constitute a subgroup of β-lactam antibiotics called cephems.-Medical use:...
(penicillin
Penicillin
Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....
-based) antibiotic. Ampicillin
Ampicillin
Ampicillin is a beta-lactam antibiotic that has been used extensively to treat bacterial infections since 1961. Until the introduction of ampicillin by the British company Beecham, penicillin therapies had only been effective against Gram-positive organisms such as staphylococci and streptococci...
(a penicillin
Penicillin
Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....
) and low-dose gentamicin
Gentamicin
Gentamicin is an aminoglycoside antibiotic, used to treat many types of bacterial infections, particularly those caused by Gram-negative organisms. However, gentamicin is not used for Neisseria gonorrhoeae, Neisseria meningitidis or Legionella pneumophila...
(an aminoglycoside
Aminoglycoside
An aminoglycoside is a molecule or a portion of a molecule composed of amino-modifiedsugars.Several aminoglycosides function as antibiotics that are effective against certain types of bacteria...
) is another therapeutic option.