Antimicrobials classification

Classification Age of Onset Infection Site Risk Factors Typical Pathogens Antimicrobial Therapy... 

Major breaks in surgical technique may cause the classification of the operation to change and require adjustments in antimicrobial prophylaxis. 

The large number and diversity of available /3-lactams, mainly penicillins and cephalosporins, necessitate their classification. Penicillins can be classified primarily according to chemical structure. Table 5.2 shows that there is good correspondence between chemical structure and properties. The categorization of cephalosporins into chemically similar groups is not useful because their antimicrobial spectrum is not closely correlated with chemical structure, and classification into generations is based on their spectrum of microbial activity (Table 5.3). 

Antimicrobial agents can be subdivided according to their mechanism of action, by their general structure or by their indications. For a systematic presentation of the various agents mostly some compromise between the three is found. In this text the structural relationships are the principal guidelines for their classification. 

The National Research Council (NRC) Wound Classification Criteria have served as the basis for recommending antimicrobial prophylaxis. NRC criteria consist of four classes (see National Research Council (NRC) Wound Classification Criteria). 

The Study of the Efficacy of Nosocomial Infection Control (SENIC) identified four independent risk factors for postoperative wound infections operations on the abdomen, operations lasting more than 2 hours, contaminated or dirty wound classification, and at least three medical diagnoses. Patients with at least two SENIC risk factors who undergo clean surgical procedures have an increased risk of developing surgical wound infections and should receive antimicrobial prophylaxis. 

Or they may be grouped according to the genus of their plant source (morphine and codeine, Section 23-2, are examples of opium alkaloids), or by their physiological effects (antimicrobials, antibiotics, analgesics), or by similarities in the route by which they are synthesized by the organism (biosynthesis). The structural and biosynthetic classifications make the most sense to the chemist and is the organization chosen here. 

Most antimicrobial peptides produced by Gram-positive bacteria are classified as bacteriocins, and like microcins they are diverse in size and structure.35 36 Recent classification schemes divide bacteriocins into three classes lantibiotics (class I), heat-stable non-lantibiotics (class II) and heat-labile antimicrobial proteins (class III), of which the majority of bacteriocins belong either to class I or class II. NMR spectroscopy has been applied in numerous studies of bacteriocins and an overview of the range of diversity in the 3D structures that have been determined by NMR spectroscopy is provided in Figure 4. 

Classification of some antimicrobial agents by their sites of action. 

The penicillins [pen i SILL in] are the most widely effective antibiotics and are among the least toxic drugs known the major adverse reaction to penicillins is hypersensitivity. The members of this family differ from one another in the R substituent attached to the 6-aminopenicillanic acid residue. The nature of this side chain affects their antimicrobial spectrum, stability to stomach acid, and susceptibility to bacterial degradative enzymes (P-lactamases). Figure 30.1 shows the main structural features of the penicillins. Figure 30.2 shows the classification of agents affecting cell wall synthesis. 

The beta-lactam antibiotics still comprise roughly half of the antibiotic market worldwide. The common structure that defines the whole family of beta-lactam antibiotics is the four-membered, highly reactive beta-lactam ring, which is essential for antimicrobial activity (1). The following simplif)dng classification is practical ... 

Table 2.2 Classification of antimicrobial agents according to their dissociation constant (pKJ...

Table 2.3 Classification of antimicrobial agents as bactericidal or bacteriostatic...

The antimicrobial antibiotics have a selectively toxic action on invading bacteria, by virtue of exploiting differences in cellular characteristics between microorganisms and their human host cells. Major target sites are the bacterial cell wall located outside the cell membrane (animal cells have only a cell membrane). and the bacterial ribosome - the protein-synthesizing organelle within its cell - which is different between bacteria and animal cells. Viruses lack both cell walls and ribosomes and so are resistant to these and other similar antibiotics. A classification of therapeutically used antibiotics can be attempted on the basis of these mechanisms. 

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