Antibiotic A-201E

Rifamycin antibiotics include the WHO essential medicines rifampin, rifabutin, and rifapentine. These are semisynthetic derivatives of the natural product rifamycins, originally isolated from the soil bacterium Amycolatopsis rifamycinica. These antibiotics are primarily used to treat mycobacterial infections, including tuberculosis. Rifamycins act by binding to the β-subunit of bacterial RNA polymerase, inhibiting transcription, which results in cell death. These antibiotics consist of a naphthalene core spanned by a polyketide ansa bridge. This structure presents a unique 3D configuration that engages RNA polymerase through a series of hydrogen bonds between hydroxyl groups linked to the naphthalene core and C21 and C23 of the ansa bridge. This binding occurs not in the enzyme active site where template-directed RNA synthesis occurs but instead in the RNA exit tunnel, thereby blocking productive formation of full-length RNA. In their clinical use to treat tuberculosis, resistance to rifamycin antibiotics arises principally from point mutations in RNA polymerase that decrease the antibiotic's affinity for the binding site in the RNA exit tunnel. In contrast, the rifamycin resistome of environmental mycobacteria and actinomycetes is much richer and diverse. In these organisms, rifamycin resistance includes many different enzymatic mechanisms that modify and alter the antibiotic directly, thereby inactivating it. These enzymes include ADP ribosyltransferases, glycosyltransferases, phosphotransferases, and monooxygenases.ADP ribosyltransferases catalyze group transfer of ADP ribose from the cofactor NAD+, which is more commonly deployed for metabolic redox reactions. ADP ribose is transferred to the hydroxyl linked to C23 of the antibiotic, thereby sterically blocking productive interaction with RNA polymerase. Like ADP ribosyltransferases, rifamycin glycosyl transferases also modify the hydroxyl of position C23 of rifamycins, transferring a glucose moiety from the donor molecule UDP-glucose. Unlike other antibiotic resistance kinases that transfer the γ-phosphate of ATP to inactivate antibiotics such as aminoglycosides or macrolides, rifamycin phosphotransferases are ATP-dependent dikinases. These enzymes transfer the β-phosphate of ATP to the C21 hydroxyl of the rifamycin ansa bridge. The result is modification of a critical RNA polymerase binding group that blocks productive complex formation. On the other hand, rifamycin monooxygenases are FAD-dependent enzymes that hydroxylate the naphthoquinone core. The result of this modification is untethering of the ansa chain from the naphthyl moiety, disrupting the essential 3D shape necessary for productive RNA polymerase binding and inhibition that leads to cell death.All of these enzymes have homologues in bacterial metabolism that either are their direct precursors or share common ancestors to the resistance enzyme. The diversity of these resistance mechanisms, often redundant in individual bacterial isolates, speaks to the importance of protecting RNA polymerase from these compounds and validates this enzyme as a critical antibiotic target.

When all rules of hygiene have been scrupulously applied, antibiotic prophylaxis (ABP) is the one remaining means of further reducing surgical site infection risk. Its efficacy in major orthopedic surgical procedures is proven. Guidelines for indications and ABP systemic administration have been long established and are able to address many questions. By extrapolation, the same protocols apply in closed fractures, whereas they are less certain in open fractures, where successive and still incomplete reassessments have been made. There are no specific ABP protocols in implant revision for mechanical or infectious causes or in high-grade open fractures, despite the high associated risk of surgical site infection. All means of prophylaxis need exploring in these contexts: various molecule combinations, and various local applications. Although ideas are by no means lacking, levels of evidence are low or undetermined. Awaiting more objective data, the focus has to be on the quality of implementation. It is easy enough to conceive of ABP in terms of the tissue pharmacokinetics of the antibiotic(s), but real-life implementation is a real organizational challenge. Optimizing practices in clearly defined indications is still the prime objective for surgical ABP.

One of the major global health care crises in the 21st century is antibiotic resistance. Almost all clinically used antibiotics have resistance emerging to them. Antibiotic Resistance can be regarded as the 'Faceless Pandemic' that has enthralled the entire world. It has become peremptory to develop treatment options as an alternative to antibiotic therapy for combating antibiotic-resistant pathogens. A clearer understanding of antibiotic resistance is required to prevent the rapid spread of antibiotic-resistant genes and the re-emergence of infections. The present review provides an insight into the different classifications and modes of action of antibiotics to understand how the hosts develop resistance to them. In addition, the association of genetics in the development of antibiotic resistance and environmental factors has also been discussed, emphasizing developing action plans to counter this "quiescent pandemic". It is also pertinent to create models that can predict the early resistance so that treatment strategies may build up in advance with the evolving resistance.