Chapter 8 Key Points: Anti-infectives can act to destroy an infective pathogen (bactericidal) or to prevent the pathogen from reproducing (bacteriostatic). Anti-infectives can have a small group of pathogens against which they are effective (narrow spectrum), or they can be effective against many pathogens (broad spectrum).Resistance of a pathogen to an anti-infective agent can be natural (the pathogen does not use the process on which the anti-infective works) or acquired (the pathogen develops a process to oppose the anti-infective agent). The emergence of resistant strains is a serious public health problem. Health care providers need to be alert to preventing the emergence of resistant strains by not using antibiotics inappropriately, assuring that the anti-infective is taken at a high enough dose for a long enough period of time, and avoiding the use of newer, powerful antiinfectives if other drugs would be just as effective.

Summary: Anti-infectives are drugs designed to act on foreign organisms that have invaded and infected the human host with selective toxicity, which means that they affect biologicalsystems or structures found in the invading organisms but not in the host. Anti-infectives include antibiotics, antivirals, antifungals, antiprotozoals, and anthelmintic agents. The goal of anti-infective therapy is interference with the normal function of invading organisms to prevent them from reproducing and promotion of cell death without negative effects on the host cells. Also, reduction of the invading organisms to a point at which the human immune response can take care of the infection. The infection should be eradicated with the least toxicity to the host and the least likelihood for development of resistance. Anti-infectives can work by altering the cell membrane of the pathogen, by interfering with protein synthesis, or by interfering with the ability of the pathogen to obtain needed nutrients. Anti-infectives also work to kill invading organisms or to prevent them from reproducing, thus depleting the size of the invasion to one that can be dealt with by the human immune system. Pathogens can develop resistance to the effects of antiinfectives over time when (1) mutant organisms that do not respond to the anti-infective become the majority of the pathogen population or (2) the pathogen develops enzymes to block the anti-infectives or alternative routes to obtain nutrients or maintain the cell membrane. An important aspect of clinical care involving anti-infective agents is preventing or delaying the development of resistance. This can be done by ensuring that the particular anti-infective agent is the drug of choice for the specific pathogen involved and that it is given in high enoughdoses for sufficiently long periods to rid the body of the pathogen. Culture and sensitivity testing of a suspected infection ensures that the correct drug is being used to treat the infection effectively. Culture and sensitivity testing should be performed before an anti-infective agent is prescribed. Anti-infectives can have several adverse effects on the human host, including renal toxicity, multiple GI effects, neurotoxicity, hypersensitivity reactions, and superinfections. Some anti-infectives are used as a means of prophylaxiswhen patients expect to be in situations that will expose them to a known pathogen, such as travel to an area where malaria is endemic, or oral or invasive GI surgery in a personwho is susceptible to subacute bacterial endocarditis.