Biomedical Engineering Reference
In-Depth Information
core (hence the prefix “actino”) and resembling fungal hyphae (hence the suf-
fix “mycosis”). Actinomyces species inhabit normal mouths, and sulfur gran-
ules are frequently found in the tonsillar crypts of healthy individuals.
Several species closely related to Genus Actinomyces can produce an
allergic disease of the lung after chronic inhalation (e.g. Micropolyspora
faeni and less commonly Saccharopolyspora rectivirgula). This disease,
which is not a true infection, is known by a number of different names,
including farmer's lung.
Genus Arcanobacterium contains Arcanobacterium haemolyticum,
formerly assigned to a different genus, as Corynebacterium haemolyticum.
Arcanobacterium haemolyticum is a cause of pharyngitis.
Actinobacteria
Actinomycetale
Corynebacterinae
Corynebacteriaceae
*Corynebacterium
Dermatophilaceae
*Dermatophilus
Mycobacteriaceae
*Mycobacterium
Nocardiaceae
*Nocardia
*Rhodococcus
Members of Class Corynebacterineae share a distinctive and complex cell
wall composition. Most species contain mycolic acids in their cells walls,
linked to peptidoglycans. Class Corynebacterineae, like all the members
of Class Actinobacteria, are Gram-positive. Class Corynebacterineae (particu-
larly Genus Mycobacteria and Genus Nocardia) resist decolorization with acid.
The term “acid fast” refers to this property, in which the Gram stain
is “fastened” to the cell wall. Mycolic acid contributes to “acid-fastness.”
Pathologists employ so-called acid-fast stains (technically, the organism is
acid-fast, not the stains) to identify pathogenic organisms in this group.
Class Corynebacterium, a subclass of Class Corynebacterineae, contains
several pathogenic species.
Corynebacterium minutissimum causes erythrasma, a skin rash.
Corynebacterium jeikeium, which is normally confined to skin, tracks into
blood via indwelling devices, causing opportunistic nosocomial infections
(e.g., sepsis, endocarditis) in immune-compromised patients, particularly
those who have received bone marrow transplants [57].
Corynebacterium diphtheriae is the cause of diphtheria, a disease that
occurs where vaccination is underutilized. The disease usually presents as a
sore throat, covered with a characteristic membrane. The term diphtheria has
its root in the Greek work, “diphthera” meaning two leather scrolls, referring
