Disease relevance of ermC

• ermC is an inducible antibiotic resistance gene from Staphylococcus aureus, one of several whose expression is regulated at the level of mRNA secondary structure [1].
• Expression of ermC can also be demonstrated in Bacillus subtilis carrying plasmid pE194 [1].
• The induction efficiency of a test panel of MLS antibiotics was studied by using two translational attenuator-lac reporter gene fusion constructs, one based on ermSV from Streptomyces viridochromogenes NRRL 2860 and the other based on ermC from Staphylococcus aureus RN2442 [2].
• The predominant plasmid carrying ermC was 2.5 kb, while four plasmids were smaller and three were larger. ermC has been found in all phage type patterns [3].
• The sequence predicts a 243-amino-acid protein that is homologous to those specified by ermC, ermAM, and ermD, resistance determinants from Staphylococcus aureus, Streptococcus sanguis, and Bacillus licheniformis, respectively [4].

High impact information on ermC

• During induction of ermC, the inhibition of a ribosome active in translation of a short leader peptide by low levels of antibiotic belonging to the macrolide-lincosamide-streptogramin b family is believed to cause a rearrangement in mRNA secondary structure [1].
• The resultant conformational isomerization unmasks the methylase ribosome binding site and initiator Met codon, causing increased translation of the ermC transcript [1].
• Additionally, physical evidence was obtained demonstrating that during induction, the stalled ribosome protects codons 9 and 10 of the leader peptide from modification by dimethyl sulfate, in agreement with genetic data obtained previously that identified the integrity of codons 5-9 as critical for induction of ermC by erythromycin [1].
• The DNA sequence of the ermC gene of plasmid pE194 is presented [5].
• The sequence contains an open reading frame sufficient to encode the previously identified 29,000 dalton ermC protein [5].

Chemical compound and disease context of ermC

• A beneficial effect of the combination of quinupristin-dalfopristin and vancomycin was observed against two methicillin-resistant strains of Staphylococcus aureus harboring or not harboring the ermC gene, which codes for constitutive macrolide, lincosamide, and streptogramin B resistance [6].
• A group of 130 clinical isolates of Staphylococcus aureus and 100 isolates of erythromycin-resistant coagulase-negative staphylococci (CNS) were examined by disk approximation; all CNS isolates and a subset of S. aureus isolates were examined by PCR for ermA, ermC, and msrA [7].

Biological context of ermC

• Sequence deletions of 16, 59, and 111 bp as well as a tandem duplication of 272 bp with respect to the corresponding sequence of pT48 were identified in the regulatory regions of constitutively expressed ermC genes [8].
• A model for the development of sequence deletions in the ermC translational attenuator by homologous recombination is presented and experimentally tested by in vitro selection of constitutively expressed mutants in staphylococcal strains deficient and proficient in homologous recombination [8].
• Constitutive ermC gene expression as a consequence of these structural alterations is based on either the prevention of the formation of mRNA secondary structures in the translational attenuator or the preferential formation of those mRNA secondary structures which do not interfere with the translation of the ermC transcripts [8].
• Among the staphylococci, two variants of the inducible phenotype detected with the agar diffusion assay correlated with the presence of classical ermA or ermC genes, respectively, by dot-blot analysis [9].
• Assembly was also inhibited in a B. subtilis strain carrying a plasmid with the ermC gene that confers macrolide resistance by rRNA methylation [10].

Associations of ermC with chemical compounds

• Two erythromycin-resistant strains of S. aureus that carried the ermC gene were as sensitive as wild-type cells to antibiotic inhibition [11].
• Resistance was mainly due to the presence of ermA or ermC genes, which were detected in 259 strains (88%), in particular those resistant to methicillin (78% of the strains) [12].
• Of 82 erythromycin-resistant CNS isolates that contained ermA or ermC, 57 demonstrated constitutive clindamycin resistance, and 25 demonstrated inducible resistance, at 20 and 26 mm [7].
• The transfer of ermA and ermC genes, the two most common resistance determinants of erythromycin resistance, was studied with Luria-Bertani broth in the absence of additional Ca(2+) or Mg(2+) ions [13].
• The two erythromycin/lincomycin resistant S. caprae and S. epidermidis strains did not hybridize with the MLSB resistance genes ermAM, ermA, ermB and ermC [14].

Analytical, diagnostic and therapeutic context of ermC

• We tested 16 erythromycin-resistant clinical isolates of S. aureus, recovered from patients hospitalized in the United States from 1958 to 1969, for the presence of ermA, ermB, and ermC by using PCR [15].
• The insertion of ermC in the chromosomal hysA locus was confirmed by Southern blot hybridization and the loss of HL activity was demonstrated macroscopically by a plate assay [16].
• The ermC gene of pSES21 was expressed constitutively and sequence analysis of the regulatory region showed multiple base-pair insertions and substitutions in the translational attenuator [17].

References