Friday, April 18, 2008
References:
DC Krause, MF Balish - FEMS Microbiology Letters, 2001 - Blackwell Synergy
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=93483
Waris, M.E., et al (1998). Diagnosis of Mycoplasma pneumoniae pneumonia in children
http://s99.middlebury.edu/BI330A/projects/Howard/Mpneumoniae.html#anchor723401
http://jcm.asm.org/cgi/content/full/36/4/1151, Journal of Clinical Microbiology
http://www.roadback.org/index.cfm/fuseaction/education.display.html&display_id=93
Molecular Biology and Pathogenesis. (American Society for Microbiology, Washington, D.C.)
http://nar.oxfordjournals.org/cgi/content/abstract/25/4/701
http://en.wikipedia.org/wiki/Mycoplasma
http://pathmicro.med.sc.edu/mayer/myco.htm
http://www.emedicine.com/EMERG/topic467.htm
http://books.google.com.my/books?id=RVH-CDn-R1kC&pg=PA48&lpg=PA48&dq=vaccine+on+mycoplasma+pneumonia&source=web&ots=T-1IMQfLjX&sig=kIKsx8o0vJ8x-PSuNkPfXj5CV4s&hl=en
http://www.healthscout.com/ency/68/205/main.html
http://www.jstor.org/pss/25184
http://en.wikipedia.org/wiki/Vaccine
Genomic Evolution:
Genomic Evolution:
Mycoplasma pneumoniae has classically been considered an extracellular (or membrane-associated) organism. Nevertheless, the recently elucidated genomic structure of this pathogen strongly suggest that this organism may have been subjected to the process of reductive genetic evolution which is characteristic of intracellular bacteria.
Besides that, the 5S rRNA sequences of eubacteria and mycoplasmas have been analyzed and a phylogenetic tree constructed. The sequences of 5S rRNA from Clostridium innocuum, Acholeplasma laidlawii, Acholeplasma modicum, Anaeroplasma bactoclasticum, Anaeroplasma abactoclasticum, Ureaplasma urealyticum, Mycoplasma pneumoniae, and Mycoplasma gallisepticum is being analyzed. The analysis of these and published sequences shows that mycoplasmas form a coherent phylogenetic group that, with C. innocuum, arose as a branch of the low G+C Gram-positive tree, near the lactobacilli and streptococci. The initial event in mycoplasma phylogeny was formation of the Acholeplasma branch; hence, loss of cell wall probably occurred at the time of genome reduction to ≈ 1000 MDa. A subsequent branch produced the Spiroplasma. This branch appears to have been the origin of sterol-requiring mycoplasmas. During development of the Spiroplasma branch there were several independent genome reductions, each to ≈ 500 MDa, resulting in Mycoplasma and Ureaplasma species. Mycoplasmas, particularly species with the smallest genomes, have high mutation rates, suggesting that they are in a state of rapid evolution.
Vaccination and Eradication:
We can consider modify the virulent factor and used it as a vaccine. As we know that, when Mycoplasma pneumonia is interacted with the host cells, it will inhibit the host cells’ catalase which can be used to breaks down hydrogen peroxide and toxic form of oxygen which is lethal to the cells. We can introduce anti-toxin as a vaccine which is to be injected to the human for prevention of the disease.
Gene-modified Mycoplasma pneumoniae can be considered to be made into vaccine against itself too. The gene therapy required method eliminates the disease-causing gene and replaced it with a modified gene, which can be inserted with functions that enhance the cell regulatory in host cells. Little amount of the gene-modified M. pneumonia can be injected to human body as a vaccine and trigger the immune response of the human body to produce antibody of immune cells to bind at the surface protein of the pathogens and attract phagocytes to kill them.
New Prevention or Treatment:
Since M. pneumoniae infections are almost exclusively mild, preventative measures are not normally recommended as necessary. But then, for some reason, people still can get vaccinated as recommended by physician.
Get vaccinated. Because pneumonia can be a complication of the flu, getting a yearly flu shot is a good way to prevent viral influenza pneumonia, which can lead to bacterial pneumonia. Your doctor may recommend a pneumonia vaccine if you're a smoker, if you're younger but have a lung or cardiovascular disease, certain types of cancer, diabetes or sickle cell anemia, if your immune system is compromised or if you've had your spleen removed for any reason.
Get flu shot. Yearly flu shot can help to prevent pneumoniae since viral pneumoniae may develop from influenza.
New Diagnostic Strategy:
By using PCR - method for amplifying a selected nucleic acid sequence. To target the amplification to a specific DNA segment, two primers bearing the complementary sequences that are unique to the target gene are used. These two primers hybridize to opposite strands of the target DNA, thus enabling DNA polymerase to extend the sequence between them. Each cycle produces a complementary DNA strand to the target gene. Newer detection methods targeting protein antigens or nucleic acids hold promise for more rapid diagnosis. To diagnosed it, usually the physician use of a nested-PCR assay to detect M. pneumoniae DNA in tissue samples from two patients with severe pneumonia. With this approach, a definitive diagnosis was available within 24 h.
Nowadays, there are many PCR test kit that available that can be used to diagnose the disease and it is easy to handle. Mycoplasma complement fixation or MCF which is the replacement test for cold agglutinin titer, identifies antibodies to a specific mycoplasma and are reported as a titer to the specific mycoplasma(s) resident in the patient. This is more specific than the M. pneumoniae kit.
We can also collect the samples from the patients, screen the samples and find out if there are any presence of DNA or protein sequence of the pathogen by the help of existing software. For this case, we can check the presence of the unique adhesin protein of M. pneumonia which allows close interaction between the pathogen and the host cells. It is a useful method which can be used to identify the pathogen which attack the patient’s system.
Genome Information:
When Mycoplasma species were first cultured, they were thought to have been virus because of their size. However, after discovered the presence of DNA and RNA, they are said to be types of bacteria. They are very tiny and able to fit through 450nm pore diameter membrane filters. One of the members of Mycoplasma is M. pneumomiae. The complete sequence of M. pneumoniae genome indicates that it is a circular duplex DNA of 816,394 bp. The presumptive origin of replication is in an A+T rich region between dnaA and dnaN. A total of 677 open reading frames (ORFs) and 39 genes coding for various RNAs were identified. M. pneumoniae has a degenerate genome because it uses some unique genetic code to make its code more similar to mitochondria than to other bacteria. It lacks the cellular machinery for making new purines and pyrimidines. However, it has tri-carboxylic acid cycle and an incomplete electron transport chain.
The coding regions in M. pneumoniae comprise a total length of 724,174 bp, or 88.7% of the genome. The average size of a gene is 1011 bp, giving an average of one gene every 1140 bp. This is similar to the gene size and density seen with both the smaller M. genitalium genome as well as the H. influenza genome, which is more than twice as large.
Below is the comparison of genome information between M. pneumoniae and M. genitalium:
We compare them with emphasis on genome organization and coding capacity. All the 470 proposed open reading frames (ORFs) of the smaller M.genitalium genome (580 kb) were contained in the larger genome (816 kb) of M.pneumoniae. There were some discrepancies in annotation, but inspection of the DNA sequences showed that the corresponding DNA was always present in M.pneumoniae. The two genomes could be subdivided into six segments. The order of orthologous genes was well conserved within individual segments but the order of these segments in both bacteria was different. We explain the different organization of the segments by translocation via homologous recombination. The translocations did not disturb the continuous bidirectional course of transcription in both genomes, starting at the proposed origin of replication. The additional 236 kb in M.pneumoniae, compared to the M.genitalium genome, were coding for 209 proposed ORFs not identified in M.genitalium. Of this ORFs 110 were specific to M.pneumoniae exhibiting no significant similarity to M.genitalium ORFs, while 76 ORFs were amplifications of ORFs existing mainly as single copies in M.genitalium. In addition, 23 ORFs containing a copy of either one of the three repetitive DNA sequences RepMP2/3, RepMP4 and RepMP5 were annotated in M.pneumoniae but not in M.genitalium, although similar DNA sequences were present. The M.pneumoniae-specific genes included a restriction-modification system, two transport systems for carbohydrates, the complete set of three genes coding for the arginine dihydrolase pathway and 14 copies of the repetitive DNA sequence RepMP1 which were part of several different translated genes with unknown function.
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