Virulence Plasmids of Nonsporulating Gram-Positive Pathogens

Abstract

SUMMARY Gram-positive bacteria are leading causes of many types of human infection, including pneumonia, skin and nasopharyngeal infections, as well as urinary tract and surgical wound infections among hospitalized patients. These infections have become particularly problematic because many of the species causing them have become highly resistant to antibiotics. The role of mobile genetic elements, such as plasmids, in the dissemination of antibiotic resistance among Gram-positive bacteria has been well studied; less well understood is the role of mobile elements in the evolution and spread of virulence traits among these pathogens. While these organisms are leading agents of infection, they are also prominent members of the human commensal ecology. It appears that these bacteria are able to take advantage of the intimate association between host and commensal, via virulence traits that exacerbate infection and cause disease. However, evolution into an obligate pathogen has not occurred, presumably because it would lead to rejection of pathogenic organisms from the host ecology. Instead, in organisms that exist as both commensal and pathogen, selection has favored the development of mechanisms for variability. As a result, many virulence traits are localized on mobile genetic elements, such as virulence plasmids and pathogenicity islands. Virulence traits may occur within a minority of isolates of a given species, but these minority populations have nonetheless emerged as a leading problem in infectious disease. This chapter reviews virulence plasmids in nonsporulating Gram-positive bacteria, and examines their contribution to disease pathogenesis.

Genome Sequence of Listeria monocytogenes Plasmid pLM-C-273 Carrying Genes Related to Stress Resistance

“…Listeria monocytogenes is highly resistant to environmental stresses that usually limit bacterial growth, such as low temperatures, fluctuations in pH, high salt concentrations, and metal ions ( 1 ), making its eradication from food manufacturing plants difficult. In general, plasmids have been implicated as genetic vectors in the interbacterial transfer of antibiotic resistance ( 2 ), virulence factors ( 3 ), and metal ion resistance factors ( 4 ). Here, we report the nucleotide sequence of L. monocytogenes plasmid pLM-C-273, which was derived from the whole-genome sequence of the strain LM-C-273.…”