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Query: UMLS:C0026936 (Mycoplasma)
 14,761 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A correlation was found between the expression of a specific Mycoplasma fermentans surface antigen (Pra, proteinase-resistant antigen) and the site of isolation of the organism from the infected host. Strains which expressed Pra were most frequently associated with cells of bone marrow origin, and strains which lacked expression of Pra were most commonly isolated from the respiratory tract, genital tract, and arthritic joints, i.e., epithelial cell surfaces. Pra was previously shown to be resistant to degradation by proteinases and was hypothesized to play a protective role at the organism surface and perhaps to influence which host tissue site was colonized by the organism. The methods used for this phenotyping scheme required isolation and growth of the mycoplasma in quantities sufficient for immunoblot analysis using monoclonal antibodies. We wanted to determine a more rapid and less cumbersome technique to supplement this method for determining the Pra phenotype directly in clinical specimens. Here we describe PCR studies to investigate the movement of a previously identified M. fermentans insertion sequence (IS)-like element. These data showed a correlation between a specific IS genotype and the Pra+ phenotype. Production of a 160-bp product using a single set of IS-based primers was associated with expression of Pra. The genomic IS location resulting in the 160-bp product was determined by using Southern blot analysis and was found to be a stable insertion site characteristic of genotype I strains. Additional analyses of sequences within and flanking the IS insertion sites revealed another pair of PCR primer sites which resulted in the consistent production of a 450-bp amplicon. The stability of this site was dependent on the absence of the IS-like element between the primer sites. The production of this 450-bp amplicon correlated with the Pra mutant phenotype and was characteristic of genotype II strains. The data showed that the sequence within the IS may be unstable and that reliable genotyping sequences are more easily found in the stable genomic sites which flank the IS element.
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PMID:Genotypic and phenotypic analysis of Mycoplasma fermentans strains isolated from different host tissues. 957 8

Six isolates of Mycoplasma bovoculi obtained from cattle herds with bovine keratoconjunctivitis were analyzed by gel electrophoresis and immunoblotting techniques. All six strains showed similarity in their protein profiles although no two patterns were identical. Antigenic differences between strains were detected in immunoblots reacted with post-exposure calf serum. A common 94 kDa protein band designated p94 was detected in all six strains reacted with monoclonal antibody MA25.5 developed to one of the strains. The p94 was also recognized in these strains by the calf serum. Trypsin treatment of intact mycoplasma cells resulted in the removal of p94 from immunoblots reacted with MA or hyperimmune rabbit serum. Other trypsin-resistant antigens shared between strains or being strain-specific in nature were identified when trypsin-treated mycoplasma cells were reacted with hyperimmune rabbit serum. The p94 antigen was shown to be of mycoplasmal origin by radio-immunoprecipitation using the MA or hyperimmune rabbit serum. These studies identify the presence of a surface antigen (p94) on M. bovoculi membrane in all strains examined that is trypsin sensitive by the use of monoclonal antibody, calf serum and hyperimmune rabbit serum.
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PMID:Identification and localization of a 94 kDa membrane protein found in Mycoplasma bovoculi strains. 977 58

Mycoplasma penetrans is a recently identified mycoplasma, isolated from urine samples collected from human immunodeficiency virus (HIV)-infected patients. Its presence is significantly associated with HIV infection. The major antigen recognized during natural and experimental infections is an abundant P35 lipoprotein which, upon extraction, segregates in the Triton X-114 detergent phase and is the basis of M. penetrans-specific serological assays. We report here that the P35 antigen undergoes spontaneous and reversible phase variation at high frequency, leading to heterogeneous populations of mycoplasmas, even when derived from a clonal lineage. This variation was found to be determined at the transcription level, and although this property is not unique among the members of the class Mollicutes, the mechanism by which it occurs in M. penetrans differs from those previously described for other Mycoplasma species. Indeed, the P35 phase variation was due neither to a p35 gene rearrangement nor to point mutations within the gene itself or its promoter. The P35 phase variation in the different variants obtained was concomitant with modifications in the pattern of other expressed lipoproteins, probably due to regulated expression of selected members of a gene family which was found to potentially encode similar lipoproteins. M. penetrans variants could be selected on the basis of their lack of colony immunoreactivity with a polyclonal antiserum against a Triton X-114 extract, strongly suggesting that the mechanisms involved in altering surface antigen expression might allow evasion of the humoral immune response of the infected host.
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PMID:Phase variations of the Mycoplasma penetrans main surface lipoprotein increase antigenic diversity. 1008 88

The attachment of two strains of Mycoplasma bovoculi to erythrocytes was measured using 35S-methionine-labelled organisms. Receptor sites of M. bovoculi involved in this attachment are trypsin-sensitive, since mild trypsin treatment of the intact organisms abolished this process completely. Pretreatment of erythrocytes with trypsin or increasing concentrations of neuraminidase resulted in no measurable effect. Monoclonal antibody MA25.5 directed against a M. bovoculi surface antigen of 94 kDa termed p94 blocked 40% of the attachment, while MA18.13 directed against a 57 kDa protein band of M. bovoculi had no effect on the attachment process. Other properties of M. bovoculi were tested using six strains of the mycoplasma and erythrocytes from several animal species. None of the strains showed haemagglutinating or haemadsorbing activities.
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PMID:Interactions of Mycoplasma bovoculi with erythrocytes: role of p94 surface protein. 1041 66

Mycoplasma synoviae is a poultry pathogen causing respiratory disease and synovitis. A number of serological assays have been developed for diagnosis of M. synoviae infection; however, they lack sensitivity and/or are prone to false-positive reactions. Using a combination of PCR and expression cloning, four overlapping regions (regions 1-4) of the surface antigen MSPB of M. synoviae WVU-1853 were expressed in a bacterial expression system. Immunostaining of the resultant polypeptides with chicken sera raised against different M. synoviae strains, or Mycoplasma gallisepticum S6, suggested that region 4 contained a highly antigenic and species-specific domain (amino acids 212-317) [corrected] of MSPB. A fusion protein of region 4 was expressed in the pMAL expression system and purified from cold-osmotic-shock fluids of Escherichia coli cells for use in an indirect ELISA. The potential of the purified antigen for detection of M. synoviae antibodies was assessed with sera obtained from chickens experimentally infected with different strains of M. synoviae or M. gallisepticum, or from uninoculated chickens. All the sera from M. synoviae-inoculated chickens provided higher absorbance values than those from M. gallisepticum-inoculated or uninoculated chickens. Chickens inoculated with M. synoviae 86079/7NS had detectable increases of serum anti-MSPB immunoglobulins at day 7 after inoculation. These studies have identified the most antigenic region of one of the major species-specific surface proteins of M. synoviae, and shown the potential of this protein as a serodiagnostic reagent.
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PMID:Mycoplasma synoviae surface protein MSPB as a recombinant antigen in an indirect ELISA. 1046 75

Restriction and modification (R-M) systems are generally thought to protect bacteria from invasion by foreign DNA. This paper proposes the existence of an alternative role for the phase-variable R-M systems encoded by the hsd loci of Mycoplasma pulmonis. Populations of M. pulmonis cells that arose during growth in different environments were compared with respect to R-M activity and surface antigen production. When M. pulmonis strain X1048 was propagated in laboratory culture medium, > 95% of colony-forming units (cfu) lacked R-M activity and produced the variable surface protein VsaA. Mycoplasmas isolated from the nose of experimentally infected rats also lacked R-M activity and produced VsaA. In contrast, the cell population of mycoplasmas isolated from the lower respiratory tract of the infected rats was more complex. The most dramatic results were obtained for mycoplasmas isolated from the trachea. At 14 days postinfection, 38% of mycoplasma isolates produced a Vsa protein other than VsaA, and 34% of isolates had active restriction systems. These data suggest that differences in selection pressures in animal tissues affect the surface proteins and the R-M activity of the mycoplasmal cell population. We propose that variations in the production of R-M activity and cell surface proteins are important for the survival of the mycoplasma within the host.
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PMID:Variations in the surface proteins and restriction enzyme systems of Mycoplasma pulmonis in the respiratory tract of infected rats. 1140 10

Mollicutes are unique microorganisms characterized by a great extent for the reduction in genetic material, which retained the capability of independent division on acellular nutrient media. Phenotypically mycoplasmas differed from other bacteria by their small size and lack of a cell wall (mollis, soft; cutis, skin). High dependence on metabolism components utilized in the cultivation medium and high metabolic plasticity due to the absence of many genome regulatory elements make mycoplasmas perfect parasites for cells of the eukaryotic origin. The ability of these microorganisms to pass through host cells and their assumed participation in AIDS activation facilitate the study of mycoplasma pathogenesis. Another important feature of mycoplasmas, which is expressed during their interaction with a macroorganism, is their ability to escape from the immune response of a host due to surface antigen variation. These adaptation capacities of mycoplasmas ensuring their life in various biological niches, given a limited genome and the direct metabolic dependence on an environment, cannot be adequately explained at present. In this review, we attempted to collect and systematize data that contribute to our understanding of the important feature of mycoplasmas, genetic instability, which may underlie many of their adaptive responses.
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PMID:[Mechanisms of genetic instability of mollicutes (mycoplasma)]. 1164 20

Mycoplasma penetrans is a newly identified species of the genus MYCOPLASMA: It was first isolated from a urine sample from a human immunodeficiency virus (HIV)-infected patient. M. penetrans changes its surface antigen profile with high frequency. The changes originate from ON<==>OFF phase variations of the P35 family of surface membrane lipoproteins. The P35 family lipoproteins are major antigens recognized by the human immune system during M. penetrans infection and are encoded by the mpl genes. Phase variations of P35 family lipoproteins occur at the transcriptional level of mpl genes; however, the precise genetic mechanisms are unknown. In this study, the molecular mechanisms of surface antigen profile change in M. penetrans were investigated. The focus was on the 46-kDa protein that is present in M. penetrans strain HF-2 but not in the type strain, GTU. The 46-kDa protein was the product of a previously reported mpl gene, pepIMP13, with an amino-terminal sequence identical to that of the P35 family lipoproteins. Nucleotide sequencing analysis of the pepIMP13 gene region revealed that the promoter-containing 135-bp DNA of this gene had the structure of an invertible element that functioned as a switch for gene expression. In addition, all of the mpl genes of M. penetrans HF-2 were identified using the whole-genome sequence data that has recently become available for this bacterium. There are at least 38 mpl genes in the M. penetrans HF-2 genome. Interestingly, most of these mpl genes possess invertible promoter-like sequences, similar to those of the pepIMP13 gene promoter. A model for the generation of surface antigenic variation by multiple promoter inversions is proposed.
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PMID:Multiple promoter inversions generate surface antigenic variation in Mycoplasma penetrans. 1248 60

The Mycobacterium tuberculosis protein ESAT-6 has unusual immune stimulating activities, has been implicated in the recall of long-lived immunity, and induces protection against tuberculosis in mice. For many diseases caused by bacterial or viral pathogens, a strong cell-mediated immune (i.e., type 1) response is often required for recovery or protection. Therefore, it is important to design immunization regimens that induce agent-specific type 1 immunity. We have shown in previous studies that ESAT-6 could enhance antigen-specific type 1 immune responses in BALB/c mice against a second antigen when presented as a purified fusion protein. It was also of interest to determine if ESAT-6 could enhance the type 1 response against a second antigen beyond that afforded by DNA vaccination through CpG motifs. This was tested by using gene fusions of ESAT-6 and the Mycoplasma hyopneumoniae surface antigen P71. Modified P71 gene sequences were cloned with or without ESAT-6 sequences into a DNA vaccine vector and were used to immunize mice. Splenic lymphocytes from vaccinated mice were tested for gamma interferon (IFN-gamma) and interleukin-10 (IL-10) secretion. Serum antibodies were examined for P71 antigen-specific isotype responses. When stimulated in vitro with purified P71 antigen, splenocytes from the ESAT-6:P71 vaccinates secreted higher levels of IFN-gamma and lower levels of IL-10 compared to those of vaccinates receiving the P71 construct alone. Furthermore, the immunoglobulin G2a serum antibody levels were significantly higher in the ESAT-6:P71 vaccinates compared to those of the vaccinates receiving P71 alone. In conclusion, ESAT-6 was shown to enhance antigen-specific type 1 immune responses in BALB/c mice when used in DNA vaccines.
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PMID:Enhanced murine antigen-specific gamma interferon and immunoglobulin G2a responses by using mycobacterial ESAT-6 sequences in DNA vaccines. 1265 48

The prevalence of bacterial vaginosis and other lower genital tract infections were determined in women from a developing community. Patients were recruited from four out-patient clinics of a large urban tertiary referral hospital serving the indigent Black population of KwaZulu/Natal, South Africa. A total of 208 women attending the sexually transmitted diseases (STD) (n = 51), colposcopy (n =50), family planning (n = 52) and antenatal (n = 55) clinics were investigated. Endocervical and vaginal specimens were collected for microbiological investigation of recognised sexually transmitted pathogens. Estimation of vaginal pH, amine test and wet smear microscopy were performed at the bedside. Peripheral venous blood was obtained for serological tests for syphilis, hepatitis B surface antigen and antibody to the human immunodeficiency virus (HIV). Vaginal infections were detected in a total of 50% (104) of women, endocervical infections alone in 9% (18) and concurrent vagino-endocervical infections in 20% (41). Bacterial vaginosis (BV) was diagnosed in 35% (73) and its prevalence amongst different clinic populations ranged from 25% to 41% with no significant differences between any groups. Trichomoniasis was detected significantly more often in women attending the STD and antenatal clinics. Endocervical infections were found mainly in women attending the STD clinic, though the prevalence of Chlamydia trachomatis amongst the other clinic attenders ranged from 13% to 20%. Micro-organisms such as Gardnerella vaginalis, Mycoplasma hominis, anaerobes and curved Gram-negative rods were found in significantly higher number of women with BV. This study confirms the high prevalence of vaginal, endocervical and mixed vagino-endocervical infections in women from developing communities. The high prevalence of bacterial vaginosis as a single infection and its association with other recognised sexually transmitted pathogens in a large proportion of women, is of significance since such infections not only predispose to ascending upper genital tract infections but are also associated with complications in pregnancy such as premature rupture of membranes, preterm labour and endometritis.
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PMID:Bacterial vaginosis and lower genital tract infections in women attending out-patient clinics at a tertiary institution serving a developing community. 1551 15


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