Antibiotics classes

The antibiotic activity of certain (3-lactams depends largely on their interaction with two different groups of bacterial enzymes. (3-Lactams, like the penicillins and cephalosporins, inhibit the DD-peptidases/transpeptidases that are responsible for the final step of bacterial cell wall biosynthesis.63 Unfortunately, they are themselves destroyed by the [3-lactamases,64 which thereby provide much of the resistance to these antibiotics. Class A, C, and D [3-lactamases and DD-peptidases all have a conserved serine residue in the active site whose hydroxyl group is the primary nucleophile that attacks the substrate carbonyl. Catalysis in both cases involves a double-displacement reaction with the transient formation of an acyl-enzyme intermediate. The major distinction between [3-lactamases and their evolutionary parents the DD-peptidase residues is the lifetime of the acyl-enzyme it is short in (3-lactamases and long in the DD-peptidases.65-67... 

Antibiotic Class Antibiotic Pediatric (mg/kg/day) Adult (total dose/day)... 

These natural product scaffolds identified provided us with most of the antibiotic classes identified to date and they also provided the model for the many semisynthetic antibiotics approved in the recent years. Natural products contributed to more than 78% of the antibiotics approved between 1981 and 2002. Known targets in the clinic are inhibitors of bacterial... 

This antibiotic class has the highest number of antibiotics on the market. All P lactam antibiotics have a basic fl-lactam ring structure and other classes are categorized based on the structure of the ring adjacent to the beta-lactam ring (Fig. 3). The majority of the fl-lactams derived from natural products and approved for human use are listed in Table 2. 

Oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) are the main representatives of this antibiotic class. In addition, demeclocycline (DMC), doxycycline (DXC), minocycline (MNC), and methacycline (MTC) can be found in food samples. 

Jackson, J.J., Kropp, H., Hurley, J.C. Influence of antibiotic class and concentration on the percentage of release of lipopolysaccharide from Escherichia coli. J Infect Dis 169 (1994) 471—473. 

In 1999, Suzuki completed the synthesis of pradimicinone,63 the aromatic pen-tacyclic aglycone moiety common to both the pradimicin and benanomicin antibiotic classes. The key step in the approach involves a Sml2-mediated pinacol cyclisation of an axially chiral 2,2 -biaryldicarbaldehyde 54 (Scheme 7.24). This cyclisation proceeds to give the trans- 1,2-diol 55 in quantitative yield and with complete transfer of the axial chirality in the starting material to the central chirality of the product, which is obtained in enantiomerically pure form. The selectivity and chiral transfer were attributed to an i e,i e-cyclisation mode, giving the diequatorial product.63... 

Figure 4 Exemplar structures of various antibiotic classes that bind to either the 505 or the 305 subunit. Macrolides azithromycin (1), oxazolidinones linezolid (2), aminoglycosides Kanamycin A (3), Pleuromutilin (4), phenylpropanoids chloramphenicol (5), lincosamides clindamycin (6), Sparsomycin (7), Anisomycin (8), and tetracycline (9). See Scheme 9 for thiosptrepton (38). Not pictured streptogramins such as quinupristin/dalfopristin.

Kollef, M.H. Vlasnik, J. Sharpless, L. Pasque, C. Murphy, D. Fraser, V. Schedule changes of antibiotic classes A strategy to decrease the incidence of ventilator associated pneumonia. Am. J. Respir. Crit. Care Med. 1997, i56(4 Pt. 1), 1040 1048. 

That structural variation of congeners can spell the difference between drugs of little or no clinical utility and drugs of wide applicability can also be seen by comparing the properties of various members of antibiotic classes isolated solely from microbiological sources. Some of these cases are summarized in Table VIII. 

Antibiotics, in combination with NSAIDs, ACE inhibitor and contrast media, are responsible for the majority of cases with drug-induced ARF. The antibiotic class most often implicated is the aminoglycosides [4, 5, 8]. Acute renal failure complicating treatment with aminoglycosides occurs in about 10% of therapeutic courses most of these patients receive inappropriate regimens of the drug [7. ... 

Daptomycin binds to bacterial membranes resulting in depolarization, loss of membrane potential, and cell death. It has concentration-dependent bactericidal activity. Due to its unique mechanism of action, cross-resistance with other antibiotic classes seems not to occur, and there are no known resistance mechanisms. There were two cases (one S. aureus and the other E. faecalis) among more than 1000 cases treated in which resistance emerged during therapy. Staphylococci with decreased susceptibility to vancomycin have higher daptomycin MICs than fully susceptible strains. 

Research activity in the macrolide antibiotic class has been intense recently in attempts to reduce side effects and to broaden their antimicrobial spectra. The ketolides are a group of agents that are characterized by oxidation of the 3-position from an alcohol to a ketone. They are active against a significant number of erythromycin-resistant microorganisms. Recent investigation has been intense and a new agent has been introduced. 

Ever since penicillin was discovered and further developed into a drug for use in humans, there has hardly been a natural product that parallels its impact on medicine and pharmacy. Yet, penicillin is only one example of the /J-lactam antibiotics class, along with other fungal (and streptomycete) secondary metabolites, for... 

Aminoglycoside Antibiotic Classes and their Sonrce Organism ... 

Many factors influence the residue profiles of antibiotics in animal-derived edible tissues (meat and offal) and products (milk and eggs), and in fish and honey. Among these factors are the approved uses, which vary markedly between antibiotic classes and to a lesser degree within classes. For instance, in some countries, residues of quinolones in animal tissues, milk, honey, shrimp, and fish are legally permitted (maximum residue limits [MRLs] have been established). By comparison, the approved uses of the macrolides are confined to the treatment of respiratory disease and for growth promotion (in some countries) in meat-producing animals (excluding fish), and to the treatment of American foulbrood disease in honeybees. As a consequence, residues of macrolides... 

---