Mapping and cloning of Corynebacterium diphtheriae plasmid pNG2 and characterization of its relatedness to plasmids from skin coryneforms

Abstract

The relationship of plasmid pNG2, isolated from an erythromycin-resistant strain of Corynebactenium diphtheriae, to plasmids isolated from skin coryneforms was examined. The extent of homology between plasmids from erythromycin-resistant and -susceptible skin coryneforms and pNG2 varied, but in aggregate homology was observed with all six BstEII fragments of pNG2. The data support the hypothesis that pNG2 originated in skin coryneforms. Intact plasmid pNG2 and some of its restriction fragments were cloned into Escherichia coli JM109. The erythromycin resistance phenotype was expressed in clones carrying intact pNG2 as well as in some of its fragments and appeared to depend on a C. diphtheriae promoter for expression. A 2.5-megadalton EcoRI fragment, the smallest expressing resistance, contained the 1.2-megadalton region of pNG2 which is deleted when the erythromycin-resistant strain of C. diphtheriae reverts spontaneously to the susceptible state.Schiller et al. (16) isolated the first and thus far only Corynebacterium diphtheriae plasmid from clinical strains that were resistant to erythromycin (Emr). The plasmid, pNG2, has a molecular mass of 9.6 megadaltons (MDa), and the data suggest that the plasmid gene(s) mediating resistance is on a 1.2-MDa segment that is consistently lost when Emr strains revert spontaneously to the erythromycinsusceptible (Ems) state. The susceptible revertants carry the 8.4-MDa plasmid pNG3 in place of

Transcription of the ContiguoussigB,dtxR, andgalEGenes inCorynebacterium diphtheriae: Evidence for Multiple Transcripts and Regulation by Environmental Factors

“…The expression vector pSPZ that was used to determine ␤-galactosidase activity encoded by a lacZ reporter gene in C. diphtheriae was constructed by ligating the 1.2-kb FspI-to-NsiI fragment of pJKS1 (40) to the 7.7-kb NsiI to NruI fragment of pKMZ (Y. Qian and R. K. Holmes, unpublished data). This fragment of pKMZ contained transcriptional terminators and the promoterless lacZ gene from pCM502 (50) as well as the stable replication origin of pNG2 (57). The plasmid pSPZ encodes resistance to spectinomycin.…”

Mechanisms of Antibiotic Resistance in Corynebacterium spp. Causing Infections in People

“…ErmX occurring in C. diphtheriae is contained in plasmid pNG2, similar to plasmids isolated from Corynebacterium spp. occurring on the skin (Serwold-Davis & Groman, 1986). The replicon 2.6-kb EcoRI-ClaI fragment (oriR) may be possessed by many microorganisms, including a popular commensal E. coli (Deb & Nath, 1999;Serwold-Davis et al, 1990;Serwold-Davis et al, 1987).…”

Use of plasmid profiles in epidemiologic surveillance of disease outbreaks and in tracing the transmission of antibiotic resistance

“…Antibiotic resistance transfer among streptococci can be mediated by plasmids or by other elements called conjugative transposons (38). Plasmid transfer between or within other gram-positive bacteria also occurs (71,72,176). Transfer of resistance determinants from gram-positive to gram-negative organisms and Mycoplasma spp.…”