''Cardiobacterium valvarum'' is a
Gram-negative
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...
bacteria of the
Cardiobacterium
''Cardiobacterium'' is a Gram-negative bacillus (rod-shaped) bacterium commonly grouped with other bacteria into the HACEK group. Species of ''Cardiobacterium'' include ''Cardiobacterium hominis
''Cardiobacterium hominis'' is a Gram-negative ...
genus that can cause
infective endocarditis
Infective endocarditis is an infection of the inner surface of the heart, usually the valves. Signs and symptoms may include fever, small areas of bleeding into the skin, heart murmur, feeling tired, and low red blood cell count. Complications ...
. They belong to the
HACEK
The HACEK organisms are a group of fastidious Gram-negative bacteria that are an unusual cause of infective endocarditis, which is an inflammation of the heart due to bacterial infection. HACEK is an abbreviation of the initials of the genera of t ...
group of fastidious bacteria that are present in normal oropharyngeal flora that can develop into
infective endocarditis
Infective endocarditis is an infection of the inner surface of the heart, usually the valves. Signs and symptoms may include fever, small areas of bleeding into the skin, heart murmur, feeling tired, and low red blood cell count. Complications ...
.
Microbiology
The only other identified
Cardiobacterium
''Cardiobacterium'' is a Gram-negative bacillus (rod-shaped) bacterium commonly grouped with other bacteria into the HACEK group. Species of ''Cardiobacterium'' include ''Cardiobacterium hominis
''Cardiobacterium hominis'' is a Gram-negative ...
species is ''
Cardiobacterium hominis
''Cardiobacterium hominis'' is a Gram-negative bacillus (rod-shaped) bacterium commonly grouped with other bacteria into the HACEK group. It is one of several bacteria that is normally present in the mouth and upper part of the respiratory trac ...
''.
Cardiobacterium
''Cardiobacterium'' is a Gram-negative bacillus (rod-shaped) bacterium commonly grouped with other bacteria into the HACEK group. Species of ''Cardiobacterium'' include ''Cardiobacterium hominis
''Cardiobacterium hominis'' is a Gram-negative ...
species are pleomorphic
Gram-negative
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...
bacteria rod-shaped bacteria that are
catalase
Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting t ...
-negative and
oxidase
In biochemistry, an oxidase is an enzyme that catalyzes oxidation-reduction reactions, especially one involving dioxygen (O2) as the electron acceptor. In reactions involving donation of a hydrogen atom, oxygen is reduced to water (H2O) or hydro ...
-positive. When compared morphologically, the two
Cardiobacterium
''Cardiobacterium'' is a Gram-negative bacillus (rod-shaped) bacterium commonly grouped with other bacteria into the HACEK group. Species of ''Cardiobacterium'' include ''Cardiobacterium hominis
''Cardiobacterium hominis'' is a Gram-negative ...
species are indistinguishable in culture and
Gram stain
In microbiology and bacteriology, Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. The name comes from the Danish ...
, however, differ in growth patterns. ''C.valvarum'' is more
fastidious
A fastidious organism is any organism that has complex or particular nutritional requirements. In other words, a fastidious organism will only grow when specific nutrients are included in its medium. The more restrictive term fastidious microorgan ...
than
''C. hominis'', and are non-
hemolytic
Hemolysis or haemolysis (), also known by several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may occur in vivo o ...
. ''C.valvarum'' is also differentiated by the fact that they do not produce
indole
Indole is an aromatic heterocyclic organic compound with the formula C8 H7 N. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered pyrrole ring. Indole is widely distributed in the natural environmen ...
.
Isolates of ''C. valvarum'' show optimal growth by day 3 under standard 5% incubation conditions on 5% sheep blood but scant growth on chocolate agar.
Identification
Members of the
HACEK
The HACEK organisms are a group of fastidious Gram-negative bacteria that are an unusual cause of infective endocarditis, which is an inflammation of the heart due to bacterial infection. HACEK is an abbreviation of the initials of the genera of t ...
group are difficult to identify through conventional methods. 16S ribosomal RNA genotyping is the necessary method of identifying ''C.valvarum'. C.valvarum'' bears numerous phenotypic similarities with ''
Pasteurella multocida
''Pasteurella multocida'' is a Gram-negative, nonmotile, penicillin-sensitive coccobacillus of the family Pasteurellaceae. Strains of the species are currently classified into five serogroups (A, B, D, E, F) based on capsular composition and ...
'' and is frequently misidentified. The phenylphosphonate reaction and MALDI-TOF mass spectrometry can be used to distinguish the two species.
The
Cardiobacterium
''Cardiobacterium'' is a Gram-negative bacillus (rod-shaped) bacterium commonly grouped with other bacteria into the HACEK group. Species of ''Cardiobacterium'' include ''Cardiobacterium hominis
''Cardiobacterium hominis'' is a Gram-negative ...
species are broadly susceptible to
beta-lactam
A beta-lactam (β-lactam) ring is a four-membered lactam. A ''lactam'' is a cyclic amide, and ''beta''-lactams are named so because the nitrogen atom is attached to the β-carbon atom relative to the carbonyl. The simplest β-lactam possible is ...
,
trimethoprim-sulfamethoxazole
Trimethoprim/sulfamethoxazole, sold under the brand name Bactrim among others, is a fixed-dose combination antibiotic medication used to treat a variety of bacterial infections. It consists of one part trimethoprim to five parts sulfamethoxazo ...
,
fluoroquinolone
A quinolone antibiotic is a member of a large group of broad-spectrum bacteriocidals that share a bicyclic core structure related to the substance 4-quinolone. They are used in human and veterinary medicine to treat bacterial infections, as wel ...
s, and
aztreonam
Aztreonam, sold under the brand name Azactam among others, is an antibiotic used primarily to treat infections caused by gram-negative bacteria such as ''Pseudomonas aeruginosa''. This may include bone infections, endometritis, intra abdominal ...
. Current clinical guidelines recommend that ''C.valvarum'' infection be treated with a 4-week course of
ceftriaxone
Ceftriaxone, sold under the brand name Rocephin, is a third-generation cephalosporin antibiotic used for the treatment of a number of bacterial infections. These include middle ear infections, endocarditis, meningitis, pneumonia, bone and joint ...
or
ciprofloxacin
Ciprofloxacin is a fluoroquinolone antibiotic used to treat a number of bacterial infections. This includes bone and joint infections, intra abdominal infections, certain types of infectious diarrhea, respiratory tract infections, skin infec ...
.
References
Gammaproteobacteria
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