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Mycoplasma pneumoniae

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Mycoplasma pneumoniae

Mycoplasma pneumoniae
Scientific classification
Kingdom: Bacteria
Division: Tenericutes
Class: Mollicutes
Order: Mycoplasmatales
Family: Mycoplasmataceae
Genus: Mycoplasma
Binomial name
Mycoplasma pneumoniae
Somerson et al., 1963

Mycoplasma pneumoniae is a very small bacterium in the class Mollicutes. It is a human pathogen that causes the disease mycoplasma pneumonia, a form of atypical bacterial pneumonia related to cold agglutinin disease. M. pneumoniae is characterized by the absence of a peptidoglycan cell wall and resulting resistance to many antibacterial agents. The persistence of M. pneumoniae infections even after treatment is associated with its ability to mimic host cell surface composition.

Contents

  • Discovery and history 1
  • Taxonomy and classification 2
  • Cell biology 3
  • Genomics and metabolic reconstruction 4
  • Host and reproduction 5
  • Pathogenicity 6
    • Cytadherence 6.1
    • Intracellular localization 6.2
    • Immune response 6.3
    • Cytotoxicity and organismal effects 6.4
  • Epidemiology 7
  • Symptoms of infection 8
  • Diagnosis 9
  • Treatment and prevention 10
  • See also 11
  • References 12
  • Further reading 13
  • External links 14

Discovery and history

In 1898, Nocard and Roux were the first to isolate a mycoplasma species in culture from bovine, however it wasn't until 1944 when Mycoplasma pneumoniae, known then as Eaton agent or Eaton's agent,[1] was isolated and described from a patient with primary atypical pneumonia.[2]

Initially M. pneumoniae was considered as a

  • genomeMycoplasma pneumoniae

External links

  • Baseman J. B. (1996). "Interplay between Mycoplasma Surface Proteins, Airway Cells, and the Protean Manifestations of Mycoplasma-mediated Human Infections". American Journal of Respiratory and Critical Care Medicine 154: 137–144.  
  • Razin S., Yogev D., Naot Y. (1998). "Molecular biology and pathogenicity of mycoplasmas". Microbiol. Mol. Biol. Rev. 62 (4): 1094–156.  
  • Kashyap S., Sarkar, M. (2010). "Mycoplasma pneumonia: Clinical features and management". Lung India 27 (2): 75–85.  
  • Narita M. (2009). "Pathogenesis of neurologic manifestations of Mycoplasma pneumoniae infection". Pediatr Neurol. 41 (3): 159–166.  
  • Ferwerda A., Moll H. A., de Groot R. (2001). "Respiratory tract infections by Mycoplasma pneumoniae in children: a review of diagnostic and therapeutic measures". Eur J Pediatr. 160 (8): 483–491.  
  • Esposito S., Droghetti R., Bosis S., Claut L. Marchisio P., Principi N. (2002). "Cytokine secretion in children with acute Mycoplasma pneumoniae infection and wheeze". Pediatric Pulmonology 34 (2): 122–127.  
  • Ríos A. M., Mejías A., Chávez-Bueno S., Fonseca-Aten M., Katz K., Hatfield J., Gómez A. M., Jafri H. S., McCracken G. H., Ramilo O., Hardy R. D. (2004). "Impact of Cethromycin (ABT-773) Therapy on Microbiological, Histologic, Immunologic, and Respiratory Indices in a Murine Model of Mycoplasma pneumoniae Lower Respiratory Infection". Antimicrob Agents Chemother. 48 (8): 2897–2904.  

Further reading

This article incorporates public domain text from the CDC as cited.

  1. ^ A.S. Dajani, W.A. Clyde Jr. and F.W. Denny (1965). (Eaton's Aagent)"Mycoplasma Pneumoniae"Experimental Infection with . The Journal of Experimental Medicine 121 (6): 1071–1086.  
  2. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az Ken; Waites, B; Deborah, F. Talkington (2004). "Mycoplasma pneumoniae and Its Role as a Human Pathogen". Clin. Microbiol. Rev 17 (4): 697–728.  
  3. ^ Eaton MD, Meiklejohn G, van Herrick W, Corey M (1945). "STUDIES ON THE ETIOLOGY OF PRIMARY ATYPICAL PNEUMONIA : III. SPECIFIC NEUTRALIZATION OF THE VIRUS BY HUMAN SERUM". J. Exp. Med. 82 (5): 329–42.  
  4. ^ B.P. Marmion (1990). "Eaton agent—science and scientific acceptance: a historical commentary". Rev. Infect. Dis. 12 (2): 338–53.  
  5. ^ a b c d e Weisburg, W. G.; Tully, J. G.; Rose, D. L.; Pretzel, J.P.; Oyaizu, H.; Yang, D.; Mandelco, L.; Sechrest, J.; Lawrence, T. G.; Etten, J. Van (1989). "A phylogenetic analysis of the mycoplasmas: basis for their classification". J. Bacteriol 171: 6455–6467. 
  6. ^ a b c d e f g h i j k l m Romero-Arroyo, C. E.; Jordan, J.; Peacock, S. J.; Willby, M. J.; Farmer, M. A.; Krause, D. C. (1994). "Mycoplasma pneumoniae protein P30 is required for cytadherence and associated with proper cell development". J. Bacteriol 181: 1079–1087.  
  7. ^ a b c d S. Dallo, and J. Baseman "Intracellular DNA replication and long-term survival of pathogenic mycoplasmas" Microb. Pathog. 2000; 29, 301–309.
  8. ^ a b c d e f Wodke, J. A. H.; Puchałka, J.; Lluch-Senar, M.; Marcos, J.; Yus, E.; Godinho, M.; Gutiérrez-Gallego, R.; Serrano, L.; Klipp, E.; Maier, T. "Dissecting the energy metabolism in Mycoplasma pneumoniae through genome-scale metabolic modeling". Mol. Syst. Biol 2010: 9.  
  9. ^ a b c d e f Drasbek, M.; Christiansen, G.; Drasbek, K. R.; Holm, A.; Birkelund, S. (2007). "Interaction between the P1 protein of Mycoplasma pneumoniae and receptors on HEp-2 cells". Microbiology 153: 3791–3799.  
  10. ^ a b c d e Baseman, J. B.; Cole, R. M.; Krause, D. C.; Leith, D. K. (1982). "Molecular basis for cytadsorption of Mycoplasma pneumoniae". J. Bacteriol 151: 1514–1522. 
  11. ^ a b c Hahn, T.-W; Willby, M. J.; Krause, D.C. (1998). "HMW1 Is Required for Cytadhesin P1 Trafficking to the Attachment Organelle in Mycoplasma pneumoniae". J. Bacteriol 180: 1270–1276. 
  12. ^ a b Sobeslavsky, B. Prescott; Chanock, R. M. "Adsorption of Mycoplasma pneumoniae to Neuraminic Acid Receptors of Various Cells and Possible Role in Virulence". J. Bacteriol 96: 695–705. 
  13. ^ "CDC Mycoplasma Pneumoniae". CDC. CDC. Retrieved 23 September 2015. 
  14. ^ a b c d Daxboeck, F.; Krause, R.; Wenisch, C. (2003). "Laboratory diagnosis of Mycoplasma pneumoniae infection". Clin. Microbiol. Infect 9: 263–273.  
  15. ^ a b Matsuoka, M.; Narita, M.; Okazaki, N.; Ohya, H.; Yamazaki, T.; Ouchi, K.; Suzuki, I.; Andoh, T.; Kenri, T.; Sasaki, Y.; Horino, A.; Shintani, M.; Arakawa, Y.; Sasaki, T. (2004). "Characterization and Molecular Analysis of Macrolide-Resistant Mycoplasma pneumoniae Clinical Isolates Obtained in Japan". Antimicrob. Agents Chemother 48: 4624–4630.  
  16. ^ Eshaghi, A; Memari, N; Tang, P; Olsha, R; Farrell, DJ; Low, DE; et al. "Macrolide-resistant Mycoplasma pneumoniae in humans, Ontario, Canada, 2010–2011". Emerg Infect Dis 19.  
  17. ^ a b c Meyers, L. A.; Newman, M. E. J.; Martin, M.; Schrag, S. "Applying Network Theory to Epidemics: Control Measures for Mycoplasma pneumoniae Outbreaks". Emerg. Infect. Dis. 9: 204–210.  

References

See also

Transmission of Mycoplasma pneumoniae infections is difficult to limit because of the several day period of infection before symptoms appear.[17] The lack of proper diagnostic tools and effective treatment for the bacterium also contribute to the outbreak of infection.[17] Using network theory, Meyers et al. analyzed the transmission of M. pneumoniae infections and developed control strategies based on the created model. They determined that cohorting is less effective due to the long incubation period, and so the best method of prevention is to limit caregiver-patient interactions and reduce the movement of caregivers to multiple wards.[17]

Vaccine design for M. pneumoniae has been focused primarily on prevention of host cell attachment, which would prevent initiation of cytotoxicity and subsequent symptoms.[2] To date, vaccines targeted at the P1 adhesin have shown no reduction in the onset of infection, and some vaccine trials resulted in worsened symptoms due to immune system sensitization.[2] Introduction of peptides that block adhesion receptors on the surface of the host cell may also be able to prevent attachment of M. pneumoniae.[9]

The difficulty in eradicating Mycoplasma pneumoniae infections is due to the ability of the bacterium to persist within an individual, as well as the lack of cell wall in M. pneumoniae, which renders multiple antibiotics directed at the bacterial cell wall ineffective in treating infections.[2] M. pneumoniae therefore displays resistance to antimicrobials such as β-lactams, glycopeptides, sulfonamides, trimethoprim, polymixins, nalidixic acid, and rifampin.[2][14] The majority of antibiotics used to treat M. pneumoniae infections are targeted at bacterial rRNA in ribosomal complexes, including macrolides, tetracycline, ketolides, and fluoroquinolone, many of which can be administered orally.[2][15] Macrolides are capable of reducing hyperresponsiveness and protecting the epithelial lining from oxidative and structural damage, however they are capable only of inhibiting bacteria (bacteriostatic) and are not able to cause bacterial cell death.[2][7] The most common macrolides used in the treatment of infected children in Japan are erythromycin and clarithromycin, which inhibit bacterial protein synthesis by binding 23S rRNA.[15] Administration of antibiotics has been proven to reduce the longevity and intensity of M. pneumoniae infections in comparison to cases left untreated. Additionally, some high-dose steroid therapies have shown to reverse neurological effects in children with complicated infections.[2] Antimicrobial drug resistance rates for Mycoplasma pneumoniae were determined in clinical specimens and isolates obtained during 2011–2012 in Ontario, Canada. Of 91 M. pneumoniae drug-resistant specimens, 11 (12.1%) carried nucleotide mutations associated with macrolide resistance in the 23S rRNA gene. None of the M. pneumoniae specimens were resistant to fluoroquinolones or tetracyclines.[16]

Treatment and prevention

infections. M. pneumoniae Neither of these methods, along with others, has been available to medical professionals in a rapid, efficient and inexpensive enough form to be used in routine diagnosis, leading to decreased ability of physicians to diagnose [2]

Diagnosis

M. pneumoniae is known to cause a host of symptoms such as primary atypical pneumonia, tracheobronchitis, and upper respiratory tract disease. Primary atypical pneumonia is one of the most severe types of manifestation, with tracheobronchitis being the most common symptom and another 15% of cases, usually adults, remain asymptomatic.[2][14] Symptomatic infections tend to develop over a period of several days and manifestation of pneumonia can be confused with a number of other bacterial pathogens and conditions that cause pneumonia. Tracheobronchitis is most common in children due to a reduced immune system capacity, and up to 18% of infected children require hospitalization.[2] Common mild symptoms include sore throat, wheezing and coughing, fever, headache, coryza, myalgia and feelings of unease, in which symptom intensity and duration can be limited by early treatment with antibiotics. Rarely, M. pneumoniae pneumonia results in death due to lesions and ulceration of the epithelial lining, pulmonary edema, and bronchiolitis obliterans. Extrapulmonary symptoms such as autoimmune responses, central nervous system complications, and dermatological disorders have been associated with M. pneumoniae infections in up to 25% of cases.[2]

Symptoms of infection

The incidence of disease does not appear be related to season or geography, however infection tends to occur more frequently during the summer and fall months when other respiratory desiccation. Outbreaks of M. pneumoniae infections tend to occur within groups of people in close and prolonged proximity, including schools, institutions, military bases, and households.[2]

Epidemiology

The main cytotoxic effect of M. pneumoniae is local disruption of tissue and cell structure along the respiratory tract epithelium due to its close proximity to host cells. Attachment of the bacteria to host cells can result in loss of cilia, a reduction in metabolism, biosynthesis, and import of macromolecules, and, eventually, infected cells may be shed from the epithelial lining.[2] M. pneumoniae produces a unique virulence factor known as Community Acquired Respiratory Distress Syndrome (CARDS) toxin. [13]The CARDS toxin most likely aids in the colonization and pathogenic pathways of M. pneumoniae, leading to inflammation and airway dysfunction. In addition, the formation of hydrogen peroxide is a key virulence factor in M. pneumoniae infections.[2] Attachment of M. pneumoniae to erythrocytes permits diffusion of hydrogen peroxide from the bacteria to the host cell without detoxification by catalase or peroxidase, which can injure the host cell by reducing glutathione, damaging lipid membranes and causing protein denaturation.[2][12] Local damage may also be a result of lactoferrin acquisition and subsequent hydroxyl radical, superoxide anion and peroxide formation.[2] The cytotoxic effects of M. pneumoniae infections translate into common symptoms like coughing and lung irritation that may persist for months after infection has subsided. Local inflammation and hyperresponsiveness by infection induced cytokine production has been associated with chronic conditions such as bronchial asthma and has also been linked to progression of symptoms in individuals with cystic fibrosis and COPD.[2]

Cytotoxicity and organismal effects

[2] can change the composition of its cell membrane to mimic the host cell membrane and avoid detection by M. pneumoniae In addition to evasion of host immune system by intracellular localization,

Immune response

Mycoplasma pneumoniae is known to evade host immune system detection, resist antibiotic treatment, and cross mucosal barriers, which may be due to its ability to fuse with host cells and survive intracellularly.[2][7] In addition to the close physical proximity of M. pneumoniae and host cells, the lack of cell wall and peculiar cell membrane components, like cholesterol, may facilitate fusion (1). Internal localization may produce chronic or latent infections as M. pneumoniae is capable of persisting, synthesizing DNA, and replicating within the host cell even after treatment with antibiotics.[7] The exact mechanism of intracellular localization is unknown, however the potential for cytoplasmic sequestration within the host explains the difficulty in completely eliminating M. pneumoniae infections in afflicted individuals.[2]

Intracellular localization

Schematic of the phosphorylated proteins in the attachment organelle of Mycoplasma pneumoniae

[9][2], which bind to fibronectin.pyruvate dehydrogenase E1 β chains on glycolipids and glycoproteins to facilitate attachment, in addition to the proteins TU and oligosaccharide on the surface of the bacterial cells are capable of binding Lectins [12][9][2] receptors.neuraminic acid, and fibronectin, glycoproteins, glycolipids, sulfated sialoglycoconjugates. Among them are epithelium cells to the respiratory tract M. pneumoniae cell surface components have been implicated in the adherence of eukaryotic A number of [6] to a host cell (usually a M. pneumoniae Adherence of

Cytadherence

Mycoplasma pneumoniae host immune system by intracellular localization and adjustment of the cell membrane composition to mimic the host cell membrane.

Pathogenicity of Mycoplasma pneumoniae in vasculitic/thrombotic disorders

Pathogenicity

Mycoplasma pneumoniae exclusively motility and cell division, but also reduce the ability of M. pneumoniae cells to adhere to the host cell.[6]

Host and reproduction

fermentation.[2][5][6][8] M. pneumoniae is consequently very susceptible to loss of enzymatic function by gene mutations, as the only buffering systems against functional loss by point mutations are for maintenance of the pentose phosphate pathway and nucleotide metabolism.[8] Loss of function in other pathways is suggested to be compensated by host cell metabolism.[8] In addition to the potential for loss of pathway function, the reduced genome of M. pneumoniae outright lacks a number of pathways, including the TCA cycle, respiratory electron transport chain, and biosynthesis pathways for amino acids, fatty acids, cholesterol and purines and pyrimidines.[2][6][8] These limitations make M. pneumoniae dependent upon import systems to acquire essential building blocks from their host or the environment that cannot be obtained through glycolytic pathways.[6][8] Along with energy costly protein and RNA production, a large portion of energy metabolism is exerted to maintain proton gradients (up to 80%) due to the high surface area to volume ratio of M. pneumoniae cells. Only 12 – 29% of energy metabolism is directed at cell growth, which is unusually low for bacterial cells, and is thought to be an adaptation of its parasitic lifestyle.[8] Unlike other bacteria, M. pneumoniae uses the codon UGA to code for tryptophan rather than using it as a stop codon.[2][5]

Genomics and metabolic reconstruction

[2] Mycoplasmas, the smallest

A) Filamentous Mycoplasma pneumoniae cells B) M. pneumoniae cells (M) attached to ciliated mucosal cells by the attachment organelle (indicated by arrow)

Cell biology

The term mycoplasma (“mykes”, meaning fungus and “plasma”, meaning formed) is derived from the fungal-like growth of some mycoplasma species.[2] The mycoplasmas were classified as Mollicutes (“mollis”, meaning soft and “cutis”, meaning skin) in 1960 due to their small size and genome, lack of cell wall, low G+C content and unusual nutritional needs.[2][5] M. pneumoniae has also been designated as an arginine nonfermenting species.[6] Mycoplasmas are further classified by the sequence composition of 16s rRNA. All mycoplasmas of the pneumoniae group possess similar 16s rRNA variations unique to the group, of which M. pneumoniae has a 6.3% variation in the conserved regions, that suggest mycoplasmas formed by degenerative evolution from the gram-positive eubacterial group that includes bacilli, streptococci, and lactobacilli.[2][5][6] M. pneumoniae is a member of the Mycoplasmataceae family and Mycoplasmatales order.[2]

Taxonomy and classification

[2].lower respiratory tract infections that caused human bacterium There were reports linking Eaton agent to the PPLOs or mycoplasmas, well known then as parasites of cattle and rodents, due to sensitivity to antimicrobials. Studies that followed until 1963 determined that Eaton’s agent was a [4]

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