Cardiobacterium hominis
Encyclopedia
Cardiobacterium 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 valve
s.
-negative, oxidase
-positive, indole
-producing Gram-negative rod. Its morphology has classically been described as highly pleomorphic and irregularly staining, although homogeneous bacilli with uniform shapes may be seen with the addition of yeast
extract.
and penicillin derivatives such as ampicillin
. However, penicillin-resistant strains, including those that produce beta-lactamase
s, have been described with increasing frequency. Clinical guidelines thus recommend that C. hominis and other HACEK organisms be presumed to harbor ampicillin resistance and therefore be treated with a third-generation cephalosporin
. C. hominis and other HACEK organisms also exhibit in vitro susceptibility to trimethoprim-sulfamethoxazole, fluoroquinolones, and aztreonam
. C. hominis is often resistant to erythromycin
.
Respiratory tract
In humans the respiratory tract is the part of the anatomy involved with the process of respiration.The respiratory tract is divided into 3 segments:*Upper respiratory tract: nose and nasal passages, paranasal sinuses, and throat or pharynx...
. However, it may also rarely cause 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...
, an infection of the heart valve
Heart valve
A heart valve normally allows blood flow in only one direction through the heart. The four valves commonly represented in a mammalian heart determine the pathway of blood flow through the heart...
s.
Microbiology
C. hominis is a catalaseCatalase
Catalase is a common enzyme found in nearly all living organisms that are exposed to oxygen, where it catalyzes the decomposition of hydrogen peroxide to water and oxygen...
-negative, oxidase
Oxidase
An oxidase is any enzyme that catalyzes an oxidation-reduction reaction involving molecular oxygen as the electron acceptor. In these reactions, oxygen is reduced to water or hydrogen peroxide ....
-positive, indole
Indole
Indole is an aromatic heterocyclic organic compound. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring. Indole is a popular component of fragrances and the precursor to many pharmaceuticals. Compounds that contain an...
-producing Gram-negative rod. Its morphology has classically been described as highly pleomorphic and irregularly staining, although homogeneous bacilli with uniform shapes may be seen with the addition of yeast
Yeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...
extract.
Antibiotic sensitivity
Historically C. hominis has been sensitive to penicillinPenicillin
Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....
and penicillin derivatives such as 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...
. However, penicillin-resistant strains, including those that produce beta-lactamase
Beta-lactamase
Beta-lactamases are enzymes produced by some bacteria and are responsible for their resistance to beta-lactam antibiotics like penicillins, cephamycins, and carbapenems . These antibiotics have a common element in their molecular structure: a four-atom ring known as a beta-lactam...
s, have been described with increasing frequency. Clinical guidelines thus recommend that C. hominis and other HACEK organisms be presumed to harbor ampicillin resistance and therefore be treated with 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:...
. C. hominis and other HACEK organisms also exhibit in vitro susceptibility to trimethoprim-sulfamethoxazole, fluoroquinolones, and aztreonam
Aztreonam
Aztreonam is a synthetic monocyclic beta-lactam antibiotic , with the nucleus based on a simpler monobactam isolated from Chromobacterium violaceum. It was approved by the U.S. Food and Drug Administration in 1986...
. C. hominis is often resistant to erythromycin
Erythromycin
Erythromycin is a macrolide antibiotic that has an antimicrobial spectrum similar to or slightly wider than that of penicillin, and is often used for people who have an allergy to penicillins. For respiratory tract infections, it has better coverage of atypical organisms, including mycoplasma and...
.