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Mycoplasmas and ureaplasmas

ISSN 2398-2977

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Synonym(s): Mollicutes

Introduction

Classification

Taxonomy

  • Class:Mollicutes.
  • Order:Mycoplasmatales.
  • Family:Mycoplasmataceae.
  • Genera:Mycoplasma: a)Mycoplasma(over 60 species). b)Ureaplasma(single species with serotypes).

Etymology

  • Gk:myco- fungus;plasma- form;mycoplasma- a fungus form;ureaplasma- a form which requires urea.

Significance

Active Forms

Active Form 1

Morphology

  • Plates are examined under low power objective of a light microscope every other day for up to one week incubation for typical fried egg appearance of the colonies.
  • Organisms vary from coccoid to pleomorphic or filamentous forms.
  • Stain weakly gram negative, however, are devoid of a cell wall.

Taxonomy

  • Smallest prokaryotic cells capable of self replication.
  • No cell wall but are contained within a plasma membrane.
  • Rowanowsky stains are more successful than Gram stain.
  • Distinguished on basis of host species.
  • Definitive identification based on serology .

Color

  • Colorless.

Tolerances

Humidity
  • Plates should be incubated in a humid atmosphere often with increased CO2 concentration .
  • The organisms can survive in the environment in humid conditions for several days.
Ultraviolet
  • Sensitive to sunlight.

Development

Growth
  • Plates should be incubated in a candle jar or under increased carbon dioxide concentration.
  • Fastidious, have exacting nutritional requirements, require absence of inhibitory factors and an isotonic medium.
Reproduction
  • Usually divide by binary fission but a lag in cytoplasmic division may yield multinucleated filaments which then fragment into individual cells.
Longevity
  • Can survive for several days in a moist environment, or in a dry environment if protected from sunlight.

Resting Forms

Clinical Effects

Epidemiology

Habitat

  • Occur as free-living saprophytes or parasites of animals.
  • Found on mucous membranes of the gastrointestinal, genital and respiratory tracts.
  • Both pathogenic and non-pathogenic mycoplasmal organisms are found on the mucous membranes of animals as commensals.

Lifecycle

  • Reproduce by binary fission, sometimes after formations of filaments.
  • Double-stranded DNA genome.

Transmission

  • Aerosol, venereal or vertical.
  • Infections may be exogenous or endogenous.

Pathological effects

  • Pathogenesis may involve immune-mediated tissue damage and formation of autoantibodies.
  • May be latent and clinical disease precipitated by stress.
  • Adhere to mucous membranes; some have structures for attachment.
  • Remain extracellular and produce various toxins and enzymes that damage and destroy host cells, eg hemolysins and proteases.
  • Infection often occurs in respiratory tract. Mycoplasmal organisms cause ciliary paralysis which may result in secondary infection by other micro-organisms .
    diseases caused
    • Horses: pneumonia, pleuritis   Lung: pleuropneumonia - bacterial (pleuritis)  , pericarditis   Heart: pericarditis  -M. felis.
    • Primates: atypical pneumonia -M. pneumonie; genital tract infections -M. hominis; urethritis -U. urealyticum.
    • Birds: respiratory disease, joint infections, respiratory disease -M. gallisepticum,M. meleagridis, M. synoviae, M. iners.
    • Cattle: contagious bovine pleuropneumonia -M. mycoidessub sppmycoides(small colony type) and other spp; mastitis, athritis, otitis interna -M. bovis.
  • Goats: septicemia, arthritis, mastitis -M. mycoidessub sppmycoides(larger colony type)M. capricolum, M. putrifaciens.
  • Swine: Enzootic pneumonia, arthritis, polyserositis -M. hypopneumoniae, M. hyorhinis, M. hyposynoviae.

Other host effects

  • Many are commensals on mucous membranes, especially upper respiratory, lower alimentary and genitourinary tracts.

Control

Control via chemotherapies

Diagnosis

Useful samples

  • Tissue/exudate/mucosal scrapings/joint fluid/mastitic milk.

Specimen storage

  • Must be kept refrigerated and processed within 2 days of collection.

Transport of samples

  • Special transport media containing protein are required.
  • Trypticase soy broth supplemented with 0.5% bovine albumin and penicillin (200 U/ml) to suppress bacterial overgrowth is often used.
  • Organisms are very susceptible to drying, therefore specimens and swabs should be placed immediately into transport medium.
  • Package according to mailing regulations   Transportation of diagnostic specimens  .

Field diagnosis

  • Direct examination of specimen is usually not productive, except in the case of milk samples, conjunctival swabs and cell cultures where large numbers of organisms may be present.

Laboratory diagnosis

  • Demonstration of the characteristic fried-egg colonies on solid media , either from primary inoculation or subculture from broth. Dienes stain to differentiate mycoplasmas from other bacteria.
  • Differentiation between the 2 genera of veterinary importance (MycoplasmaandUreaplasmaby urease test -Mycoplasmaspp urease-negative,Ureaplasmaspp urease-positive).
  • Species identification performed by testing with specific immune sera.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Wood J L N, Chanter N, Newton J R et al (1997) An outbreak of respiratory disease in horses associated with Mycoplasma felis infection. Vet Rec 140 (15), 388-391 PubMed.
  • Morley P S, Chirino-Trejo M, Petrie L et al (1996) Pericarditis and pleuritis caused by Mycoplasma felis in a horse. Equine Vet J 28 (3), 237-240 PubMed.
  • Weisburg W G, Tully J G, Rose D L et al (1989) A phylogenetic analysis of the mycoplasmas - basis for their classification. J Bacteriol 171 (2), 6455-6467 PubMed.

Other sources of information

  • Yamamoto R (1990) Mollicutes. In: Review of Veterinary Microbiology. Eds: E L Biberstein &Y C Zee. Boston: Blackwell Scientific. pp 213-221. ISBN 0 86542 085 8.