excreted unchanged in the urine.56 Many aerobic Gram-positive and Gram-negative bacteria are inhibited or killed including E. coli, Proteus mirabilis, Klebsiella spp., and Enterobacter spp. There is no effect on Pseudomonas spp. In complicated UTIs TMP/SMX should only be used in accordance with sensitivity testing because of the high resistance rates.

Glycopeptides

The glycopeptides (vancomycin, teicoplanin) inhibit the synthesis of cell walls in susceptible microbes by inhibiting peptidoglycan synthesis. Vancomycin and teicoplanin are related substances. Teicoplanin is more lipophilic. Both substances are administered intravenously. Teicoplanin has an increased half-life compared to vancomycin, as well as a better tissue penetration. The urinary excretion of both substances is 90%. They are active exclusively against Gram-positive uropathogens, such as enterococci and methicillin susceptible and resistant staphylococci.57

Linezolid

Linezolid is a member of the oxazolidinone class synthetic antibacterial agents that inhibit bacterial protein synthesis through a unique mechanism. In contrast to other inhibitors of protein synthesis, linezolid acts early in translation by preventing the formation of a functional initiation complex.58 Linezolid is rapidly absorbed after oral dosing with an absolute bioavailability of about 100%. Serum half-life is about 5.5 h, and protein binding approximately 31%.59,60 Approximately, 35% is excreted in urine as the parent drug and 50% as the two major metabolites. However, linezolid is active exclusively against Gram-positive uropathogens, such as enterococci and methicillin susceptible and resistant staphylococci. Linezolid can be used for the treatment of UTIs caused by multiresistant Gram-positive bacteria like MRSA or VRE.

Conclusion

Development of resistance in the treatment of UTI is dramatically increasing. Therefore, the basis of anti-infective therapy, the action of

current available antimicrobial substances and the structure-property relationships have to be understood for the prudent use of antibiotics. Pharmacokinetic and pharmacodynamic parameters should be used to improve dosing. The potential to induce resistance of certain antibiotic substances should be more investigated. Substances with a low potential should be preferred.

Considering this, the management of infectious diseases must be highly responsible.

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