''Mycoplasma hyopneumoniae'' is a species of
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
known to cause the disease
porcine enzootic pneumonia, a highly contagious and chronic disease affecting pigs. As with other
mollicutes
Mollicutes is a class of bacteria distinguished by the absence of a cell wall. The word "Mollicutes" is derived from the Latin ''mollis'' (meaning "soft" or "pliable"), and ''cutis'' (meaning "skin"). Individuals are very small, typically only 0. ...
, ''M. hyopneumoniae'' is small in size (400–1200 nm), has a small
genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...
(893–920 kilo-base pairs (kb)) and lacks a
cell wall
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mech ...
. It is difficult to grow in laboratories due to its complex nutritional requirements and the high chances of contamination associated with mycoplasma culture. To successfully grow the bacterium, an environment of 5–10% carbon dioxide is required, and the medium should demonstrate an acid colour shift.
This bacterium is a concern in the livestock industry as it causes a significant reduction in the growing weight of pigs. Losses in the U.S. have been previously estimated at 200 million to 1 billion dollars per annum. Porcine enzootic pneumonia is endemic worldwide and ''M. hyopneumoniae'' is present in almost every pig herd.
Treatment of this disease is limited to
antibiotics
An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention o ...
, which are currently ineffective as they do not completely remove the infection.
Vaccines
A vaccine is a biological preparation that provides active acquired immunity
The adaptive immune system, also known as the acquired immune system, is a subsystem of the immune system that is composed of specialized, systemic cells and pro ...
have been found to reduce the severity of the disease but do not prevent the disease from occurring in infected pigs.
Pathogenesis
''Mycoplasma hyopneumoniae'' attaches to the
cilia of
epithelial cells
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercell ...
in the lungs of swine, causing the
cilia to stop beating (ciliostasis), clumping and loss of cilia, eventually leading to
epithelial cell death; which is the source of the
lesions
A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals.
Types
There is no designated classifi ...
found in the lungs of pigs with porcine enzootic pneumonia. This damage impedes normal ciliary clearance and often secondary infections develop. On a cellular level, mononuclear infiltration of peribronchiolar and perivascular areas occurs.
The
immune response
An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. These invaders include a wide variety of different microorganisms including viruses, bacteria, parasites, and fungi which could ...
to ''M. hyopneumoniae'' in pigs is slow and ineffective;
it is also believed to cause much of the damage that is seen in pigs with the disease. This mycoplasma is not known to produce any specifically harmful
toxin
A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849– ...
like many other disease-causing bacteria, but some mildly toxic by-products have been observed.
Conclusions
''Mycoplasma hyopneumoniae'' has been a topic of interest in the scientific community due to the economic impact of porcine enzootic pneumonia. Three separate
strains (232, J & 7448) of this mycoplasma have had their
genomes
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding g ...
sequenced
In genetics and biochemistry, sequencing means to determine the primary structure (sometimes incorrectly called the primary sequence) of an unbranched biopolymer. Sequencing results in a symbolic linear depiction known as a sequence which suc ...
,
making it the most sequenced mycoplasma. Research has been mainly focused on identifying
adhesins with a final goal of developing an effective
vaccine
A vaccine is a biological Dosage form, preparation that provides active acquired immunity to a particular infectious disease, infectious or cancer, malignant disease. The safety and effectiveness of vaccines has been widely studied and verifie ...
that prevents ''M. hyopneumoniae'' from attaching to lung
cilia.
References
External links
* ''Mycoplasma hyopneumoniae''
Wikivetaccessed 13/09/2011
{{Authority control
Swine diseases
Pathogenic bacteria
Bacteria described in 1965
hyopneumoniae