Porcine Mycoplasmas

Whittlestone, P.

doi:10.1016/b978-0-12-078402-8.50010-3

Cited by 41 publications

(34 citation statements)

References 101 publications

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“…The results of this study reveal expanded abilities for diversification and adaptive surface variation for the Vlp system of M. hyorhinis, a pathogen of swine that maintains chronic infection in its natural host (29,35). The genetic basis of surface variation involving the vlpD, vlpE, and vlpF products is now established and shows that the organism can draw from a variable reservoir of multiple genes as a basis for diversity of surface structure.…”

Section: Discussionmentioning

confidence: 96%

Increased structural and combinatorial diversity in an extended family of genes encoding Vlp surface proteins of Mycoplasma hyorhinis

et al. 1995

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Variable lipoproteins (Vlp) constitute the major coat protein of Mycoplasma hyorhinis. They are products of multiple, divergent, single-copy genes organized in a chromosomal cluster. Three genes, vlpA, vlpB, and vlpC, have been previously identified in clonal isolates of M. hyorhinis SK76. Each is linked to a characteristic promoter region containing a homopolymeric tract of adenine residues [poly(A) tract], subject to hypermutation, that transcriptionally controls phase variation of vlp genes and leads to combinatorial surface mosaics of distinct Vlp products. The size of the natural vlp gene repertoire is unknown but may critically determine the degree of structural and combinatorial diversity available in this species. In this study, the vlp repertoire of M. hyorhinis GDL-1 was characterized and shown to contain three additional genes, vlpD, vlpE, and vlpF, clustered with other known vlp genes in the order 5-vlpD-vlpE-vlpF-IS-vlpA-IS-vlpB-vlpC-3, where IS represents copies of the IS1221 element of M. hyorhinis. The 5 boundary of this expanded family was identical to that of the more limited family 5-vlpA-IS-vlpB-vlpC-3 previously described in a clonal isolate of strain SK76. A recombinant construct containing vlpD, vlpE, and vlpF expressed antigenically distinguishable products corresponding to each gene. These genes encode characteristic C-terminal repetitive regions that are subject to size variation by insertion or deletion of intragenic repeats but maintain an extended, charged structure. Each vlp gene also contained characteristic alternative open reading frames, which provide a potential reservoir of coding sequence for Vlp diversity, possibly recruited through insertion and/or deletion mutations. These findings demonstrate a vastly expanded potential for structural diversity and combinatorial display of surface mosaics on this organism and suggest that modulation of the vlp repertoire, possibly in conjunction with mobile elements, may determine the capacity for surface variation in natural populations and laboratory strains of this mycoplasma species.The variable lipoprotein (Vlp) system of Mycoplasma hyorhinis provides a mutational strategy for adaptive surface variation that generates extreme population diversity in the major coat proteins expressed on this wall-less procaryote (27,28,38,40). The complexity of this system and its role as a prototype for analogous emerging systems in other mycoplasma species warrants a detailed characterization of the genetic and structural attributes contributing to its adaptive capabilities. Vlps are procaryotic lipoproteins processed by cleavage of a conserved prolipoprotein sequence (11) and expressed as abundant surface proteins anchored on the single mycoplasma membrane by a lipid moiety on an N-terminal Cys residue. Molecular genetic analysis has shown that alternative Vlps share distinctive structural features despite divergence throughout their surface-exposed protein sequence. Structural details of known Vlps (VlpA, VlpB, and VlpC) have been defined at the g...

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Section: Discussionmentioning

confidence: 96%

Increased structural and combinatorial diversity in an extended family of genes encoding Vlp surface proteins of Mycoplasma hyorhinis

et al. 1995

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“…M. hyopneumoniae is considered an exclusive respiratory pathogen (51). Nevertheless, M. hyopneumoniae has already been reisolated from brains of infected pigs (9).…”

Section: Discussionmentioning

confidence: 99%

Persistence of Mycoplasma hyopneumoniae in Experimentally Infected Pigs after Marbofloxacin Treatment and Detection of Mutations in the parC Gene

Carrou

Laurentie

Kobisch

et al. 2006

Antimicrob Agents Chemother

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The ability of Mycoplasma hyopneumoniae to persist despite fluoroquinolone treatments was investigated with pigs. Groups of specific-pathogen-free pigs were experimentally infected with M. hyopneumoniae strain 116 and treated with marbofloxacin at the therapeutic dose (TD) or half of the therapeutic dose (TD/2) for 3 days. Results showed that, despite tissue penetration of marbofloxacin, particularly in the trachea and the tracheal secretions, the treatments did not have any influence on M. hyopneumoniae recovery from tracheal swabs. Mycoplasmas were also isolated from inner organs and tissues such as liver, spleen, kidneys, and bronchial lymph nodes. Recontamination of pigs via environment could not explain mycoplasma persistence after medication, as decontamination of pigs and allocation to a new disinfected environment did not have any significant effect on the phenomenon. A significant decrease in the susceptibility level to marbofloxacin of 12 mycoplasma clones reisolated after the treatments (TD/2 and TD) was observed. Two point mutations were found in the ParC quinolone resistance-determining region (QRDR) of DNA topoisomerase IV (Ser803Phe and Asp843Asn), and one point mutation was observed just behind the QRDR of ParC (Ala1163Glu). This is the first time that mutations in a gene coding for topoisomerase IV have been described for M. hyopneumoniae after in vivo marbofloxacin treatments in experimentally infected pigs. However, development of resistance is not sufficient to explain M. hyopneumoniae persistence in vivo since (i) marbofloxacin concentrations were above the marbofloxacin MIC of the wild-type strain and (ii) mycoplasmas reisolated after a single injection of marbofloxacin did not display an increased marbofloxacin MIC.Mycoplasma hyopneumoniae is one of the primary pathogens associated with the porcine respiratory disease complex, one of the most common and economically important diseases for swine producers worldwide (43). M. hyopneumoniae is the etiological agent of enzootic pneumonia in swine, a chronic respiratory disease characterized by high morbidity and low mortality rates (15). The principal clinical but not constant sign is a chronic cough. Mycoplasmal pneumonia is located mainly in the anterior lobes of the lung. In the acute phase of the disease, catarrhal pneumonia is observed, with exudates in the airways. The bronchial and mediastinal lymph nodes are often enlarged. In the chronic stage of the disease, recovering lesions, consisting of fissures of collapsed alveoli adjoining areas of alveolar emphysema, are observed (26). M. hyopneumoniae is a very contagious bacterium and may be transmitted via direct contact between pigs (43) or via environment (14, 48).In vitro, M. hyopneumoniae is susceptible to various antibiotics, including fluoroquinolones, tetracyclines, spiramycin, and tiamulin (17,18,19,25,42,49). However, although antibiotic treatments are usually able to control the disease (49), persistence is observed under field conditions (43) and experimental infections (16,25)....

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“…The quinolones were highly effective against M. hyopneumoniae but less effective against M. hyorhinis. The susceptibility patterns for M. hyopneumoniae and M. flocculare were similar.Mycoplasmas can infect the respiratory tract of humans and animals (16,17,20,26). Antimicrobial agents are used to treat these infections, but because MICs of these agents have been determined infrequently, the infections are often treated empirically.…”

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confidence: 99%

“…Mycoplasmas can infect the respiratory tract of humans and animals (16,17,20,26). Antimicrobial agents are used to treat these infections, but because MICs of these agents have been determined infrequently, the infections are often treated empirically.…”

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confidence: 99%

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Comparison of methods for in vitro testing of susceptibility of porcine Mycoplasma species to antimicrobial agents

Laak

Pijpers

Noordergraaf

et al. 1991

Antimicrob Agents Chemother

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The MICs of 18 antimicrobial agents used against strains of three porcine Mycoplasma species were determined by a serial broth dilution method. Twenty field strains of M. hyorhinis, ten field strains of M.hyopneumoniae, six field strains of M. flocculare, and the type strains of these species were tested. Twelve field strains and the type strain of M. hyorhinis were also tested by an agar dilution method. Tests were read at various time points. When the broth dilution method was used, the final MIC had to be read 2 days after color changes had stopped. MICs of tetracycline, oxytetracycline, doxycycline, and minocycline were low for the three Mycoplasma species tested. MICs of chlortetracycline were 8 to 16 times higher than MICs of the other tetracyclines. Spiramycin, tylosin, kitasamycin, spectinomycin, tiamulin, lincomycin, and clindamycin were effective against all strains of M. hyorhinis and M. hyopneumoniae. The quinolones were highly effective against M. hyopneumoniae but less effective against M. hyorhinis. The susceptibility patterns for M. hyopneumoniae and M. flocculare were similar.Mycoplasmas can infect the respiratory tract of humans and animals (16,17,20,26). Antimicrobial agents are used to treat these infections, but because MICs of these agents have been determined infrequently, the infections are often treated empirically. Since the various Mycoplasma species need different complex culture media and different incubation periods for growth, MICs have been determined by various methods. Only a few authors have tried to standardize in vitro techniques for testing the susceptibility of mycoplasmas to antimicrobial agents (18,21).The International Research Program on Comparative Mycoplasmology, part of the International Organization for Mycoplasmology, established an ad hoc working group that compared various methods of testing antimicrobial agents against mycoplasmas in vitro. Various test conditions were evaluated, e.g., types of culture media, number of organisms, and lengths of incubation periods. The working group proposed the serial broth dilution method as the most useful and reproducible assay (21a).Mycoplasma hyopneumoniae causes enzootic pneumonia, a widespread and economically important disease of swine (11,15,20). Some investigators have reported the in vitro activity of antimicrobial agents against M. hyopneumoniae (5, 12, 27, 28). Different test methods were used, however, and only a few reports on recently isolated strains are available. Other Mycoplasma species of the respiratory tract of swine are M. hyorhinis and M. flocculare. M. hyorhinis is a ubiquitous organism that infrequently causes polyserositis and arthritis. M. flocculare is considered to be a ubiquitous but nonpathogenic organism that closely resembles M. hyopneumoniae in serologic and biochemical tests (20,26

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Porcine Mycoplasmas

Cited by 41 publications

References 101 publications

Increased structural and combinatorial diversity in an extended family of genes encoding Vlp surface proteins of Mycoplasma hyorhinis

Increased structural and combinatorial diversity in an extended family of genes encoding Vlp surface proteins of Mycoplasma hyorhinis

Persistence of Mycoplasma hyopneumoniae in Experimentally Infected Pigs after Marbofloxacin Treatment and Detection of Mutations in the parC Gene

Comparison of methods for in vitro testing of susceptibility of porcine Mycoplasma species to antimicrobial agents

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