Bacteria erythromycin resistance

Erythromycin (a macrolide Group I inhibitor ineffective in the archaea) impairs the functioning of bacterial SOS subunits by interacting with the central loop of domain IV of the 23S rRNA (Fig. 6). In bacteria ( . coli), erythromycin resistance is conferred by an A to U base change, or by the dimethylation of the A residue [142]. In erythromycin-resistant yeast S. cerevisiae) mitochondria, the equivalent A residue is replaced by a G[141]. In accord with these observations, all of the archaeal 23 S rRNAs sequenced until now resemble the large subunit rRNA of eucarya and of the erythromycin-resistant yeast mitochondrial ribosomes in having a G instead of the critical A residue [150]. Since the remaining structure of the peptidyltransferase loop is conserved in all of the... 

In the two bacteria with acquired erythromycin resistance, obtained in 1952 clinical isolates in the United States, it is too late to determine retrospectively whether the kind of resistant genotype erm or msr) in the two S. aureus strains could be specified. The erm gene encodes a methyltransferase (Erm protein) that catalyzes dimethylation of a specific adenine residue in 23S rRNA and requires... 

The deletion and point mutations in the 23S rRNA domain II were responsible for erythromycin resistance in E. coli A clone that mediates erythromycin resistance has been obtained from a certain plasmid containing the rrnB operon of the bacteria, the plasmid that was exposed to a hydroxylamine mutagen [167, 188, 189]. 

Although a mini-gene encoding a five-amino-acid peptide, MVLFV, has permanently been introduced into B. subtilis [192], an erythromycin-resistant mechanism due to production of E-peptide has not yet been found in clinical bacteria. 

Modifications of both saccharide moieties of erythromycin have also been made. Migration of the 3 -dimethylamino substituent to C-2 has been demonstrated [138]. Acylation of the 4"-hydroxyl group yielded products such as A-63075 (4"-0-carbamoylclarithromycin), which minimize gastrointestinal side effects in dogs [139]. Modifications of the 4"-hydroxyl group also increase activity against certain erythromycin-resistant bacteria [140, 141],... 

Erythromycin has much the same spectrum of antibacterial activity as penicillin. Because erythromycin-resistant strains of the commoner bacteria abound, the use of this antibiotic is becoming confined to three diseases mycoplasmal pneumonia, diphtheria, and Legionnaires disease. 

Propionic acid bacteria are resistant to penicillin, chlortetracycline, Chloromycetin, erythromycin, gramicidin S, polymyxin and streptomycin this makes possible a combined application of the indicated antibiotics and propionic acid bacteria for the treatment of some animal diseases. 

B. Aracil, M. Minambres, J. Oteo, C. Torres, J.L. Gomez-Garces, J.l. Alos, High prevalence of erythromycin-resistant and clindamycin-susceptible (M phenotype) viridans group streptococci from pharyngeal samples A reservoir of mef genes in commensal bacteria, 7 Antimicrob. Chemother., 48, 592-594,2001. 

Some bacteria are resistant to penicillin, because they produce an enzyme, penicillinase, that destroys the /3-lactam ring in the antibiotic. Synthesis of analogs afforded a partial solution to this problem. Ultimately, however, it became necessary to turn to antibiotics with completely different modes of action. Erythromycin, produced by a strain of Streptomyces bacteria first found in soil samples in the Philippines in 1952, functions in a distinct manner. It is a large ring lactone that interferes with the bacterial ribosome, its cell-wall protein S5mthesis factory. Although erythromycin is unaffected by penicillinase, bacteria resistant to it have developed over the decades since its introduction into the antibiotic arsenal. 

Chlamydomonas reinhardi is sensitive to the protein synthesis inhibitor, erythromycin. At the time, some erythromycin-resistant strains had been isolated and described, and we were considering experimental approaches to locate the sites of structural genes for proteins of plastid ribosomes. It seemed reasonable to use erythromycin resistance as a genetic marker if we could be certain that the antibiotic interacts with some part of the chloroplast ribosome and was not lethal for some other reason. Erythromycin was known to bind to the large subunit of Escherichia coli ribosomes, and the alteration leading to resistance in the bacteria was found to reside in a single protein in the 50 S subunit. ... 

Erythromycin (24) is a bacteriostatic antibacterial it is only effective against Grampositive organisms. It is hence especially efficacious against mastitis, but is normally only used when /3-lactam treatment is ineffective, e.g. due to emergence of resistant bacteria. It is irritant when injected parenterally, but at a rate of 10 mg kg-1 it may be administered as an intramammary injection. 

When acne is severe it may require medidnes that have to be taken by mouth and these may be stronger antibiotics combined with hormone therapy. Tetracyclines and erythromycin are typically used and they have to be taken for many weeks, but there are signs that bacteria are becoming resistant to these antibiotics and if there is no improvement in the acne within three months then this type of treatment has to be discontinued, or a much stronger antibiotic tried. Hormone therapy is available for young women with severe acne and this can block the sebum-stimulating effect of natural hormones - as well as having a contraceptive effect. 

Studies on archaeal ribosomes have shown that mutations that confer resistance to the peptidyl-transfer inhibitor anisomycin (an antibiotic that also affects eucaryal ribosomes) also map to this central loop [87]. Sequencing of several archaeal LSU rRNA has also revealed that they have either a G or a U at a position equivalent to A2058, which in bacteria produces sensitivity to erythromycin. As a consequence of this change, archaea are insensitive to this drug [29,30,87,88,95]. 

---