Virulence Plasmids of Nonsporulating Gram-Positive Pathogens

Chris M. Pillar; Michael S. Gilmore

doi:10.1128/9781555817732.ch21

Chapter 21 : Virulence Plasmids of Nonsporulating Gram-Positive Pathogens

Authors: Chris M. Pillar¹, Michael S. Gilmore²

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Affiliations: 1: Department of Ophthalmology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 73190; 2: Departments of Microbiology and Immunology, and Ophthalmology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 73190

Content Type: Monograph

Publication Year: 2004

Category: Microbial Genetics and Molecular Biology

Book DOI: 10.1128/9781555817732

Chapter DOI: 10.1128/9781555817732.ch21

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Abstract:

Gram-positive bacteria are leading causes of many types of human infection, including pneumonia; skin and nasopharyngeal infections; and, among hospitalized patients, bloodstream, urinary tract, and surgical wound infections. As variable traits of the species, many of these virulence properties are encoded by mobile genetic elements, such as virulence plasmids and pathogenicity islands. This chapter reviews virulence plasmids in nonsporulating gram-positive bacteria and examines their contribution to the pathogenesis of disease. More recent studies have determined the nature of the bacteriocin activity linked with exfoliative toxin B (ETB) virulence plasmids. Some Enterococcus faecalis strains produce a cytolysin with both bactericidal and toxin activity against eukaryotic cells. The cytolysin operon occurs along with aggregation substance on pheromone-responsive plasmids and within the recently described 150-kb pathogenicity island on which enterococcal surface protein (Esp) and aggregation substance are found. Aggregation substance expression has also been shown to correlate with an enhanced uptake of enterococci by intestinal epithelial cells. However, this increase in uptake did not result in an increase in translocation across intestinal epithelium in vitro. Virulence plasmids may then represent "selfish DNA" of limited benefit to the bacterium that takes advantage of an otherwise stable, intimate association to ensure its perpetuation, with selection limiting its presence to a small proportion of the population so as not to jeopardize the commensal existence of the vast majority.

Citation: Pillar C, Gilmore M. 2004. Virulence Plasmids of Nonsporulating Gram-Positive Pathogens, p 439-454. In Funnell B, Phillips G (ed), Plasmid Biology. ASM Press, Washington, DC. doi: 10.1128/9781555817732.ch21

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Virulence Plasmids of Nonsporulating Gram-Positive Pathogens

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Figure 1

Restriction map of pIB485 encoding SED and SEJ. Genes encoding cadmium resistance (cad) and resistance to beta-lactams (bla) are also indicated. Plasmid diagram contributed by J. J. landolo, Oklahoma University Health Sciences Center (OUHSC), Oklahoma City, Okla.

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Figure 1

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Figure 2

Plasmid map of a representative ETB-expressing plasmid, pETB. ORFs encoding ETB, cadmium resistance (cad), an operon responsible for production of staphylococcin c55 (bacteriocin operon), and the virulence factor EDIN-C are depicted (accession no. NC_003265) (174).

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Figure 2

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Figure 3

(A) Plasmid map of pADl depicting UV-resistance genes (uvr), the cytolysin operon, and genes involved in plasmid maintenance/transmission ( 46 , 56 ). (B) Depiction of genes involved in plasmid transfer and pheromone-sensing (adapted from reference 162 ). (C) Regulation of pheromone-response-mediated plasmid transfer; transcripts are depicted by arrows (adapted from reference 22 ).

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Figure 3

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Figure 4

(A) Detailed schematic of cytolysin operon (contributed by W. Haas, OUHSC, Oklahoma City, Okla.). (B) Schematic of cytolysin expression and posttranslational modification. ( 1 ) CyILL and CylLS, are synthesized, ( 2 ) arc intracellulary modified by CylM to create CylLL * and CylLS,* ( 3 ) arc secreted and further modified by CylB, resulting in CyILL′ and CylLS ′ and ( 4 ) are cleaved extracellularly by CylA to form the active cytolysin components CylLL″ and CylLS″. CylLL″ and CylLS″ are capable of forming aggregates ( 5 ) but are prevented from lysing cytolysin expressing cells via Cyl ( 6 ) (contributed by W. Haas, OUHSC, Oklahoma City, Okla.).

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Figure 4

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Figure 5

Plasmid map of virulence plasmid p33701 of R. equi. ORFs believed to be involved in plasmid maintenance and conjugation are depicted in gray, ORFs encoding Vaps are depicted in black, and putative ORFs within the proposed pathogenicity island are depicted in white ( 148 ).

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Figure 5

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