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Clindamycin and Lincomycin
Published in M. Lindsay Grayson, Sara E. Cosgrove, Suzanne M. Crowe, M. Lindsay Grayson, William Hope, James S. McCarthy, John Mills, Johan W. Mouton, David L. Paterson, Kucers’ The Use of Antibiotics, 2017
Clindamycin-resistant bacteria usually have the MLS resistance phenotype. This type of resistance is associated with genes encoding for the ribosomal methyltransferases leading to modification of the common target site for macrolides and lincosamides. The common target site is the 23S ribosomal RNA. This makes the ribosome insensitive to the actions of clindamycin. The rRNA methylases are encoded by erm (erythromycin ribosome methylase) genes, known as erm(A) or erm(C) genes (Spizek and Rezanka, 2004). These genes can be acquired through mobile elements and can be found on the bacterial chromosome or on plasmids. These erm genes can be transferred among species and confer a much more pronounced MLS-type resistance than those of spontaneous mutations (Clabots et al., 1988; Hachler et al., 1987; Halula and Macrina, 1990; Privitera et al., 1981, 1979; Tally and Malamy, 1986). Over 30 classes of erm genes have been identified (Roberts, 2004). The incidence of each class of erm genes differs among bacterial species and geographic location. For example, in staphylococci the erm(A) and erm(C) genes predominate, but in streptococci the erm(B) gene is most common.
Oxazolidinones and Streptogramins
Published in Thomas T. Yoshikawa, Shobita Rajagopalan, Antibiotic Therapy for Geriatric Patients, 2005
Stephen Marer, Shobita Rajagopalan
Thus far, resistance to linezolid and quinupristin/dalfopristin has been rare among gram-positive organisms. No cross-resistance between other protein synthesis inhibitors and linezolid has been described, as had been predicted by virtue of linezolid's unique mechanism of action. Gram-positive bacteria with de novo resistance to both linezolid and quinupristin/dalfopristin have been described. This has more frequently been the case with quinupristin/dalfopristin, probably because of streptogramin use in livestock in certain parts of the world. More important, it is possible to generate resistance to both linezolid and quinupristin/dalfopristin in the laboratory, and the emergence of resistance to both agents has also occurred in vivo during therapy. The emergence of resistant isolates during therapy can be associated with treatment failure. For linezolid, the emergence of resistance has been more common in enterococci than in staphylococci (11). The mechanism of resistance against linezolid appears to involve mutations in the 23S portion of the ribosomal RNA, which lies within the 50S subunit. The change in the 23S ribosomal RNA presumably alters the oxazolidinone binding site. Clinical conditions that increase the risk of the development of resistant strains include prolonged therapy, sequestered sites of infection, and device-related infections.
Neonatal ocular prophylaxis in the United States: is it still necessary?
Published in Expert Review of Anti-infective Therapy, 2023
Susannah Franco, Margaret R. Hammerschlag
Erythromycin, the oldest antibiotic of the broad-spectrum macrolide class, exhibits its bacteriostatic action by binding to the 50S bacterial ribosomal subunit. This prevents the formation of peptide bonds and consequently the translocation of the peptidyl-tRNA. Binding to the 50S ribosomal subunit also blocks the peptide exit channel by interacting with 23S ribosomal RNA (rRNA) located within the 50S ribosomal subunit. Protein synthesis is ultimately inhibited due to the incomplete release of polypeptides from the bacterial ribosomes [20–22]. Bacterial resistance mechanisms against macrolides are thought to be genetic, either via specific nucleotide alterations in 23S rRNA or through modifications of the 23S rRNA subunit by rRNA methylases that prevent macrolide binding. Another theorized resistance mechanism is an overexpression of efflux pumps, particularly the MtrCDE efflux pump [20].
An overview of nanotechnology-based treatment approaches against Helicobacter Pylori
Published in Expert Review of Anti-infective Therapy, 2019
Tural Safarov, Bukre Kiran, Melahat Bagirova, Adil M Allahverdiyev, Emrah Sefik Abamor
Amoxicillin, a member of the penicillin family, is an antibiotic containing a beta-lactam ring used to treat H.Pylori [33]. The main mechanisms leading to resistance to amoxicillin antibiotic are thought to be alterations in binding proteins, reduced cell membrane permeability of the antibiotic, or a combined effect of these factors [34]. Clarithromycin is one of the basic drugs used in the treatment of H.Pylori [35]. One of the most important factors of failure in H.Pylori eradication is the resistance to clarithromycin. Resistance to clarithromycin acting by binding to the peptidyl transferase cycle of the V region of the 23S ribosomal RNA molecule developed by point mutations in the 23S rRNA [36]. Metronidazole, a bactericidal antibiotic, is a synthetic nitroimidazole [27]. The synthetic nitroimidazole antibiotic, metronidazole, is activated by nitroreductases in the cytosol of the microorganism [37]. Mutations cause inactivation of these nitroreductases. This leads to the development of resistance [37].
Helicobacter pylori: molecular basis for colonization and survival in gastric environment and resistance to antibiotics. A short review
Published in Infectious Diseases, 2019
Sharmila Fagoonee, Rinaldo Pellicano
Among the currently available macrolides, only clarithromycin is widely used to treat H. pylori Infection, due to its low minimal inhibitory concentration (MIC). This drug is sensitive to acid degradation and has a half-life of less than 1 h at pH 2. Hence, the use of proton-pump inhibitors in antimicrobial regimens containing clarithromycin is important to preventing its acid degradation [55]. The dominant mechanisms underlying the development of clarithromycin resistance are several point mutations in domain V of the 23S ribosomal RNA (rRNA) gene, which result in decreased affinity and in absence of clarithromycin binding to the 50s ribosome subunit, and thus, failure to influence protein synthesis. It is noteworthy that there is well-documented evidence for cross-resistance to macrolides and that clarithromycin resistance may originate from the previous consumption of macrolides to treat other diseases such as respiratory infections. There are essential point mutations, which can occur at the nucleotide positions 2142 (A2142G and A2142C), 2143 (A2143G) and 2144 (A2144G) in the peptidyl transferase loop of the 23S rRNA gene. These mutations, that occur by chance, do not have an impact on bacterial fitness, and result in conformational change leading to decreased efficacy of the drug [55]. In fact, resistance impacts deeply on the outcome of the clarithromycin-based treatments, resulting in 66% decrease in eradication rate [54].