Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae is a species of bacteria known to cause the disease porcine enzootic pneumonia, a highly contagious and chronic disease affecting pigs.[2] As with other mollicutes, M. hyopneumoniae is small in size (400–1200 nm), has a small genome (893–920 kilo-base pairs (kb)) and lacks a cell wall.[3] 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.

Mycoplasma hyopneumoniae
Scientific classification
Domain:
Bacteria
Division:
Firmicutes
Class:
Mollicutes
Order:
Mycoplasmatales
Family:
Mycoplasmataceae
Genus:
Mycoplasma
Species:
M. hyopneumoniae
Binomial name
Mycoplasma hyopneumoniae
Maré and Switzer, 1965.[1]

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.[4] Porcine enzootic pneumonia is endemic worldwide and M. hyopneumoniae is present in almost every pig herd.[5] Treatment of this disease is limited to antibiotics, which are currently ineffective as they do not completely remove the infection. Vaccines have been found to reduce the severity of the disease but do not prevent the disease from occurring in infected pigs.[6]

Pathogenesis

M. hyopneumoniae attaches to the cilia of epithelial cells 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 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 to M. hyopneumoniae in pigs is slow and ineffective;[5] 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 like many other disease-causing bacteria, but some mildly toxic by-products have been observed.[7]

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 sequenced,[8][9] making it the most sequenced mycoplasma. Research has been mainly focused on identifying adhesins with a final goal of developing an effective vaccine that prevents M. hyopneumoniae from attaching to lung cilia.

References
  1. Maré, CJ; Switzer, WP (August 1965). "New species: Mycoplasma hyopneumoniae; a causative agent of virus pig pneumonia". Veterinary Medicine, Small Animal Clinician. 60: 841–6. PMID 14323369.
  2. Whittlestone, P. 1979. Porcine Mycoplasmas, p. 133–166. In J. G. Tully and R. F. Whitcomb (ed.), The Mycoplasmas, vol. II. Academic Press, Inc., New York.
  3. Tajima, M; Yagihashi, T (September 1982). "Interaction of Mycoplasma hyopneumoniae with the porcine respiratory epithelium as observed by electron microscope". Infection and Immunity. 37 (3): 1162–9. PMC 347662. PMID 7129633.
  4. Clark, LK; Armstrong, CH; Freeman, MJ; Scheidt, AB; Sands-Freeman, L; Knox, K (1991). "Investigating the transmission of Mycoplasma hyopneumoniae in a swine herd with enzootic pneumonia". Veterinary Medicine (USA). 86: 543–50.
  5. Minion, FC (1 June 2002). "Molecular pathogenesis of mycoplasma animal respiratory pathogens". Frontiers in Bioscience. 7 (1–3): d1410–22. doi:10.2741/minion. PMID 12045010.
  6. Haesebrouck, F; Pasmans, F; Chiers, K; Maes, D; Ducatelle, R; Decostere, A (3 June 2004). "Efficacy of vaccines against bacterial diseases in swine: what can we expect?". Veterinary Microbiology. 100 (3–4): 255–68. doi:10.1016/j.vetmic.2004.03.002. PMID 15145504.
  7. Geary, SJ; Walczak, EM (May 1985). "Isolation of a cytopathic factor from Mycoplasma hyopneumoniae". Infection and Immunity. 48 (2): 576–8. PMC 261383. PMID 3988348.
  8. Minion, FC; Lefkowitz, EJ; Madsen, ML; Cleary, BJ; Swartzell, SM; Mahairas, GG (November 2004). "The genome sequence of Mycoplasma hyopneumoniae strain 232, the agent of swine mycoplasmosis". Journal of Bacteriology. 186 (21): 7123–33. doi:10.1128/JB.186.21.7123-7133.2004. PMC 523201. PMID 15489423.
  9. Vasconcelos, AT; Ferreira, HB; Bizarro, CV; Bonatto, SL; Carvalho, MO; Pinto, PM; Almeida, DF; Almeida, LG; Almeida, R; Alves-Filho, L; Assunção, EN; Azevedo, VA; Bogo, MR; Brigido, MM; Brocchi, M; Burity, HA; Camargo, AA; Camargo, SS; Carepo, MS; Carraro, DM; de Mattos Cascardo, JC; Castro, LA; Cavalcanti, G; Chemale, G; Collevatti, RG; Cunha, CW; Dallagiovanna, B; Dambrós, BP; Dellagostin, OA; Falcão, C; Fantinatti-Garboggini, F; Felipe, MS; Fiorentin, L; Franco, GR; Freitas, NS; Frías, D; Grangeiro, TB; Grisard, EC; Guimarães, CT; Hungria, M; Jardim, SN; Krieger, MA; Laurino, JP; Lima, LF; Lopes, MI; Loreto, EL; Madeira, HM; Manfio, GP; Maranhão, AQ; Martinkovics, CT; Medeiros, SR; Moreira, MA; Neiva, M; Ramalho-Neto, CE; Nicolás, MF; Oliveira, SC; Paixão, RF; Pedrosa, FO; Pena, SD; Pereira, M; Pereira-Ferrari, L; Piffer, I; Pinto, LS; Potrich, DP; Salim, AC; Santos, FR; Schmitt, R; Schneider, MP; Schrank, A; Schrank, IS; Schuck, AF; Seuanez, HN; Silva, DW; Silva, R; Silva, SC; Soares, CM; Souza, KR; Souza, RC; Staats, CC; Steffens, MB; Teixeira, SM; Urmenyi, TP; Vainstein, MH; Zuccherato, LW; Simpson, AJ; Zaha, A (August 2005). "Swine and poultry pathogens: the complete genome sequences of two strains of Mycoplasma hyopneumoniae and a strain of Mycoplasma synoviae". Journal of Bacteriology. 187 (16): 5568–77. doi:10.1128/JB.187.16.5568-5577.2005. PMC 1196056. PMID 16077101.
  • Mycoplasma hyopneumoniae, Wikivet accessed 13/09/2011
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