Cytokines in Mycoplasma pneumoniae infections

Mycoplasma pneumoniae (M. pneumoniae) is one of the smallest free-living bacteria known. Along with other unique characteristics of this genus, it lacks the typical peptidoglycan cell wall of most eubacteria. Best known for causing tracheobronchitis and atypical pneumonia in humans, this pathogen also causes a number of extrapulmonary syndromes such as meningitis/encephalitis and arthritis. Recent studies also suggest that infection may be associated with chronic conditions such as asthma. Although the mechanisms of M. pneumoniae pathogenesis remain to be elucidated, one important component of M. pneumoniae infections is the induction of proinflammatory and other cytokines in both acute and chronic conditions. In this review, we survey the induction of cytokines by M. pneumoniae in different model systems, and we discuss the possible role of induced cytokines in M. pneumoniae pathogenesis.     

Mycoplasma pneumoniae infections in a rural setting in Canada.

Mycoplasma pneumoniae infection was monitored in patients with symptoms of acute respiratory tract infection in a village in southeastern Ontario from April 1983 to April 1984. M. pneumoniae was isolated from 51 (48%) of the 106 patients. The incidence began to increase in May 1983, reached a peak in July and declined to normal by mid-August. During the epidemic period M. pneumoniae was detected in 36 of the 43 symptomatic patients. The most prominent features of the outbreak were the considerable intrafamilial attack rate and the high frequency of pneumonia among infected patients. Treatment with tetracyclines and erythromycin reduced the duration of the illness and accelerated the resolution of symptoms.     

Comparative genome analysis of Mycoplasma pneumoniae

Background

Mycoplasma pneumoniae is a common pathogen that causes upper and lower respiratory tract infections in people of all ages, responsible for up to 40 % of community-acquired pneumonias. It also causes a wide array of extrapulmonary infections and autoimmune phenomena. Phylogenetic studies of the organism have been generally restricted to specific genes or regions of the genome, because whole genome sequencing has been completed for only 4 strains. To better understand the physiology and pathogenicity of this important human pathogen, we performed comparative genomic analysis of 15 strains of M. pneumoniae that were isolated between the 1940s to 2009 from respiratory specimens and cerebrospinal fluid originating from the USA, China and England.

Results

Illumina MiSeq whole genome sequencing was performed on the 15 strains and all genome sequences were completed. Results from the comparative genomic analysis indicate that although about 1500 SNP and indel variants exist between type1 and type 2 strains, there is an overall high degree of sequence similarity among the strains (>99 % identical to each other). Within the two subtypes, conservation of most genes, including the CARDS toxin gene and arginine deiminase genes, was observed. The major variation occurs in the P1 and ORF6 genes associated with the adhesin complex. Multiple hsdS genes (encodes S subunit of type I restriction enzyme) with variable tandem repeat copy numbers were found in all 15 genomes.

Conclusions

These data indicate that despite conclusions drawn from 16S rRNA sequences suggesting rapid evolution, the M. pneumoniae genome is extraordinarily stable over time and geographic distance across the globe with a striking lack of evidence of horizontal gene transfer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1801-0) contains supplementary material, which is available to authorized users.     

Comparative study of overlapping genes in the genomes of Mycoplasma genitalium and Mycoplasma pneumoniae

Overlapping genes are defined, in this paper, as a pair of adjacent genes whose coding regions are partly overlapping. We systematically analyzed all overlapping genes in the genomes of two closely related species: Mycoplasma genitalium and Mycoplasma pneumoniae. Careful comparisons were made for homologous genes that are overlapped in one species but not in the other. This comparative analysis allows us to propose a model of how overlapping genes emerged in the course of evolution. It was found that overlapping genes were generated primarily due to the loss of a stop codon in either gene, in many cases, the absence of which resulted in elongation of the 3' end of the gene's coding region. More specifically, the loss of the stop codon took place as a result of the following events: deletion of the stop codon (64.4%), point mutation at the stop codon (4.4%), and frame shift at the end of the coding region (6.7%). Overlapping genes, in a sense, can be thought of as the results of evolutionary pressure to minimize genome size. However, our analysis indicates that many overlapping genes, at least in the genomes of M.genitalium and M.pneumoniae, are due to incidental elongation of the coding regions.     

Motility of Mycoplasma pneumoniae.

Cell of Mycoplasma pneumoniae FH gliding on a glass surface in liquid medium were examined by microscopic observation and quantitatively by microcinematography (30 frames per min). Comparisons were made only within the individual experiments. The cells moved in an irregular pattern with numerous narrow bends and circles. They never changed their leading end. The average speed (without pauses) was relatively constant between o.2 and 0.5 mum/s. The maximum speed was about 1.5 to 2.0 mum/s. The movements were interrupted by resting periods of different lengths and frequency. Temperature, viscosity, pH, and the presence of yeast extract in the medium influenced the motility significantly; changes in glucose, calcium ions, and serum content were less effective. The movements were affected by iodoacetate, p-mercuribenzoate, and mitomycin C at inhibitory or subinhibitory concentrations. Sodium fluoride, sodium cyanide, dinitrophenol, chloramphenicol, puromycin, cholchicin, and cytochalasin B at minimal inhibitory concentrations did not affect motility. The movements were effectively inhibited by anti-M. pneumoniae antiserum. Studies with absorbed antiserum suggested that the surface components involved in motility are heat labile. The gliding of M. pneumoniae cells required an intact energy metabolism and the proteins involved seemed to have a low turnover.     

Development of a PCR-based method for diagnosing Mycoplasma pneumoniae infections

The polymerase chain reaction was used to detect clinical samples of Mycoplasma pneumoniae. A 245-bp region of the cytoadhesin P1 gene was shown to be specifically amplified in Myc. pneumoniae , but not in other species of Mollicutes. Picogram amounts of Myc. pneumoniae DNA could be detected per ml blood serum by use of a simple and reliable protocol for sample preparation and a PCR reaction involving two rounds of amplification. Application of the PCR-based method for the detection of Myc. pneumoniae in serum samples and throat swabs from patients with atypical pneumonia showed that it could be used in clinical diagnosis.     

Mycoplasma pneumoniae infection and arthritis in man.

Seven patients developed arthritis after Mycoplasma pneumoniae infection. Their joint symptoms persisted for up to one year. One patient developed an articular erosion and in another rheumatoid factor was present in serum transiently. Mycoplasma infection often causes ill-defined arthralgias and myalgias, but the migratory polyarthropathy of middle-sized joints that occurred in these patients is much less common. The prognosis seems to be good.     

Repetitive DNA sequences in Mycoplasma pneumoniae.

Two types of different repetitive DNA sequences called RepMP1 and RepMP2 were identified in the genome of Mycoplasma pneumoniae. The number of these repeated elements, their nucleotide sequence and their localization on a physical map of the M. pneumoniae genome were determined. The results show that RepMP1 appears at least 10 times and RepMP2 at least 8 times in the genome. The repeated elements are dispersed on the chromosome and, in three cases, linked to each other by a homologous DNA sequence of 400 bp. The elements themselves are 300 bp (for RepMP1) and 150 bp (for RepMP2) long showing a high degree of homology. One copy of RepMP2 is a translated part of the gene for the major cytadhesin protein P1 which is responsible for the adsorption of M. pneumoniae to its host cell.     

Cloning of the complete Mycoplasma pneumoniae genome.

The complete genome of Mycoplasma pneumoniae was cloned in an ordered library consisting of 34 overlapping or adjacent cosmids, one plasmid and two lambda phages. The genome size was determined by adding up the sizes of either the individual unique EcoRI restriction fragments of the gene bank or of the XhoI fragments of genomic M. pneumoniae DNA. The values from these calculations, 835 and 849 kbp, are in good agreement. An XhoI restriction map was constructed by identifying adjacent DNA fragments by probing with selected cosmid clones.     

Physical mapping of the Mycoplasma pneumoniae genome.

In order to study the genome organization of Mycoplasma pneumoniae a cosmid library of M. pneumoniae DNA was established using a newly designed cosmid vector (pcosRW2). From this library 32 overlapping clones were isolated covering a contiguous 720 kbp DNA segment representing about 90% of the genome assuming a genome size of about 800 kbp.