Antimicrobial resistance primary

Preexisting antimicrobial resistance is an increasing cause of treatment failure and is estimated to account for up to 70% of all treatment failures. Geography is the most important factor in HP resistance. Metronidazole-resistant strains are more prevalent in Asia (85%) than North America (30%).15 Primary resistance to amoxicillin and tetracycline remains low in both the United States and Europe. Clarithromycin resistance rates are estimated to be approximately 10% in the United States. Another confounding factor when evaluating potential antibiotic resistance is that culture and sensitivity studies are not routinely performed with HP infection. 

The role of enterococci in nosocomial infections is probably due to a variety of factors of which antimicrobial resistance appears to be a primary cause. Enterococci possess a broad spectrum of both natural (intrinsic) resistance and acquired (transferable) resistance (Franz et al. 2003). Examples of antibiotics to which the enterococci present an intrinsic resistance include the P-lactam antibiotics (third generation cephalosporins), sulphonamides and clindamycin and aminoglycosides in low levels (Eranz et al. 2003). Acquired resistance based on plasmids or transpo-sons acquisition has relevance for chloramphenicol, erythromycin, high levels of clindamycin, aminoglycosides, tetracycline, high levels of P-lactam antibiotics, fluoroquinolones and glycopeptides like vancomycin (Murray 1990 Leclercq 1997). In particular, vancomycin-resistant enterococci (VRE) pose a major problem... 

DSC has also been used to study the effects of a wide variety of antimicrobial peptides on the thermotropic phase behavior of different lipid bilayers. These studies again are highly biologically relevant because the primary mode of action of most antimicrobial peptides is the perturbation and permeabilization of the lipid bilayers of the target membrane, and these agents have considerable promise as antibiotics, especially to treat multiple dmg-resistant pathogenic bacteria. Again, the reader should consult recent reviews for more information on this topic (30, 31). 

Terrorists may attempt to use drug resistant organisms in their attack. Obviously, it is imperative to obtain the appropriate specimens, perform antimicrobial susceptibility testing of isolates promptly, and alter mass treatment accordingly (43). All antibiotics useful in treating tularemia are included in the strategic national stockpile. Chapter 6 discusses how public health officials will implement mass treatment plans, and how they will involve primary care physicians. 

Very narrow spectrum, penicillinase-resistant drugs This subclass of penicillins includes methicillin (the prototype), nafcillin, and oxacillin. Their primary use is in the treatment of known or suspected staphylococcal infections. Methicillin-resistant staphylococci (MRSA) are resistant to other members of this subgroup and may be resistant to multiple antimicrobial drugs. 

Antibiotics may be defined as secondary metabolites of micro-organisms. In contrary to primary metabolites (proteins, carbohydrates, nucleic acids, lipids) which play an essential role in the growth and multiplication of cells secondary metabolites are of no importance in that respect. Antibiotics dispose of a relative low molecular mass and the ability to exhibit microbistatic or microbicidal efficacy in/on other microbe species by impairing the cell wall biosynthesis, the cytoplasmic membrane, the oxidative phophorylation. Because of there extremely high antimicrobial activity antibiotics are mainly used as chemotherapeuticals however, some antibiotics are also used in the food industry for the protection of food against deterioration e.g. Nisin (20.11.1.), Pimaricin (20.11.2.). But these applications will be more and more restricted or even completely banned as microbes may acquire resistance which represents a severe problem in chemotherapy with antibiotics. Acquired resistance is a consequence of the selection pressure on a microbe population in the presence of microbicides. Chemotherapy with an antibiotic the application of which has led to the selection of mutant resistant organisms is no longer successful. 

The high level resistance of certain bacteria to Cm is due to the enzyme chloramphenicol acetyltransferase (CAT) which modifies the Cm to a biologically inactive derivative. CAT is an intracellular, trimeric enzyme with an average monomer size of 25 kDa. CAT catalyzes the transfer of an acetyl group from donor acetyl-CoA to the primary (C-3) hydroxyl of Cm, generating chloramphenicol 3-acetate and CoA-SH as products (Fig. 8.7). The acetylated Cm is incapable of binding to bacterial ribosome and is devoid of antimicrobial activity. 

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