Aminoglycosides Aminoglycoside antibacterials Penicillins

There is an in vitro interaction between aminoglycoside antibiotics and carbenicUhn or ticarciUin, leading to a significant loss of aminoglycoside antibacterial activity if these antibiotics are mixed in the same infusion bottle (184). The extent of inactivation depends on the penicUhn concentration, the contact time, and the temperature. Azlocillin and mezlocUhn inactivate aminoglycosides in a similar manner to that described for carbenicUhn (185,186). Aminoglycosides should not be mixed with penicillins or cephalosporins in the same infusion bottle. 

The nephrotoxicity of various combinations of antibiotics was assessed in 171 cancer patients (139 treated with a combination of aminoglycoside with penicillin or cephalosporin 32 treated with amphotericin B or vancomycin with other antibacterials). The highest nephrotoxicity (based on changes in urea and electrolytes) was found in patients treated with amphotericin B with an aminoglycoside and a cephalosporin. ... 

Norfloxacin (1, R = C2H5, R = H), a typical example, exhibits broad-spectrum activity and is useful in the treatment of upper respiratory tract and urinary infections [7] Lomefloxacin (2), a very recent introduction, is a third-generation product that, given once daily, is especially useful against pathogens resistant to cephalosponns, penicillins, and aminoglycosides [4] Floxacillin (J) is a stable, orally active antibacterial with improved activity over thenonfluonnated product (cloxacillin) [5]... 

The quinolone antibiotics feature as the one main gronp of antibacterial agents that is totally synthetic, and not derived from or based upon natural products, as are penicillins, cephalosporins, macrolides, tetracyclines, and aminoglycosides. The first of these compounds to be employed clinically was nalidixic acid more recent drugs in current use include ciprofloxacin, norfloxacin, and ofloxacin... 

In the purposeful search that followed the demonstration of the clinical efficacy of penicillin, streptomycin was obtained from Streptomyces griseus in 1944, cultured from a heavily manured field, and also from a chicken s throat. Aminoglycosides resemble each other in their mode of action, and their pharmacokinetic, therapeutic and toxic properties. The main differences in usage reflect variation in their range of antibacterial activity crossresistance is variable. 

However, by far the most important strategy involves the production of enzymes that destroy or deactivate the antibiotics. Bacterial enzymes that inactivate chloramphenicol (e.g., chloramphenicol acetyl transferase) and the aminoglycosides (usually enzymes that acetylate or phosphorylate the aminoglycosides) are quite common, but it is the penicillinases or, as they are now called, the beta-lactamases, that have had the most impact on antibacterial chemotherapy. The beta-lactam antibiotics, including the penicillins, cephalosporins and the newer variants called penems, carbapen-ems, cephamycins and monobactams, all possess the four-membered ring... 

Classes of Useful Antibacterial Antibiotics Penicillin Cephalosporin -C Steroid Aminoglycoside Polymyxin Chloramphenicol Cycloserine Tetracycline Macrolide Ansa macrolide Lincomycin Cycloserine Novobiocin... 

Increased activity of enzymes that make drags more polar is likely to inactivate an antimicrobial drug and will not lead to increased antibacterial activity. Specific examples of mechanisms that do result in synergy include (A) the combination of trimethoprim and sulfamethoxazole (B) the combination of a penicillin and an aminoglycoside and (D) the combination of clavu-lanic acid and amoxicillin. The answer is (C). 

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