''Corynebacterium amycolatum'' is a
gram-positive, non-spore-forming, aerobic or facultatively anaerobic bacillus capable of fermentation with propionic acid as the major end product of its glucose metabolism. One of its best known relatives is ''
Corynebacterium diphtheriae
''Corynebacterium diphtheriae'' is the pathogenic bacterium that causes diphtheria. It is also known as the Klebs–Löffler bacillus, because it was discovered in 1884 by German bacteriologists Edwin Klebs (1834–1912) and Friedrich Löffl ...
'', the causative agent of
diphtheria. ''C. amycolatum'' is a common component of the natural flora found on human skin and mucous membranes, and therefore is an occasional contaminant in human blood cultures but can rarely cause infections such as endocarditis.
Identification
First described in 1988, ''C. amycolatum'' is one of the diphtheroid most often isolated from clinical samples. However, it is often difficult to differentiate from other fermentative corynebacteria such as ''C. minutissimum'' and ''C. xerosis'', both of which are known human pathogens. One method of differentiation, however, is by observing the cell wall. Unlike other members of this genus, ''C. amycolatum'' lacks
mycolic acid, long fatty acids usually found in the cell wall. ''C. amycolatum'' also differs in its colony morphology; the species characteristically produces flat, whitish-gray, matte or waxy colonies on Schaedler blood agar. Its antibiotic sensitivity may also aid in its identification; the organism is generally resistant to multiple antibiotics. Because of its relatively new status as a pathogen, however, no standard laboratory tests yet identify ''C. amycolatum''.
Disease
''C. amycolatum'' has been shown to cause
pneumonia,
peritonitis,
empyema, infectious endocarditis, and fatal sepsis, most of which occur as
nosocomial infections. As an opportunistic pathogen, the bacterium is pathogenic in immunocompromised patients, mostly infecting those with underlying heart defects or intravascular devices. ''Corynebacterium'' endocarditis usually infects the left side of the heart in males, though ''C. amycolatum'' has shown a predilection for women.
While cases of disease have been small in number, this underreporting could be due to misdiagnosis of ''C. amycolatum'' as ''C. xerosis'', which is a known human pathogen.
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Treatment
For the few cases thus far, vancomycin or daptomycin has been used in tandem with rifampicin
Rifampicin, also known as rifampin, is an ansamycin antibiotic used to treat several types of bacterial infections, including tuberculosis (TB), mycobacterium avium complex, ''Mycobacterium avium'' complex, leprosy, and Legionnaires’ disease. ...
for a duration ranging from four weeks to six months. Valve replacement was also required in some cases of infectious endocarditis. Due to its recent pathogenic status, however, few treatments have been tested, and an optimal treatment regimen has yet to be established.
Antibiotic resistance
One of ''C. amycolatum's'' characteristic traits is its resistance
Resistance may refer to:
Arts, entertainment, and media Comics
* Either of two similarly named but otherwise unrelated comic book series, both published by Wildstorm:
** ''Resistance'' (comics), based on the video game of the same title
** ''T ...
to a wide range of antibiotics. Various strains tested have shown resistance to beta lactam antibiotics, lincosamides, macrolides
The Macrolides are a class of natural products that consist of a large macrocyclic lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, may be attached. The lactone rings are usually 14-, 15-, or 16-membered. Macro ...
, and quinolones
Quinolone may refer to:
* 2-Quinolone
* 4-Quinolone
* Quinolone antibiotic
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 ar ...
. Multiple drug-resistant strains were mainly isolated from wounds of patients treated in departments of general surgery and vascular surgery. However, the bacterium was shown to be particularly sensitive to glycopeptide and lipopeptide antibiotics.
References
External links
Type strain of ''Corynebacterium amycolatum'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q5173759
Corynebacterium
Gram-positive bacteria
Bacteria described in 1988