Activity, antibacterial bacteriostatic

Dactinomycin, an antineoplastic dmg, was discovered in 1943 and is made in rather pure form by StreptomjcesparvuUus. Dactinomycin has some bacteriostatic antibacterial and antifungal activity, but high toxicity limits its use to antineoplastic therapy. It may be used alone or with other antineoplastics, with or without surgery and synergistic x-ray therapy. Dose limiting bone marrow toxicity may result in low white cell and platelet count. Intestinal mucosal damage also occurs. Reviews of more detailed chemotherapeutic information are available (217—222). 

Antibiotics possess antibacterial activity and are used in the treatment of eye infections. Sulfonamides possess a bacteriostatic effect against a wide range of gram-positive and gram-negative microorganisms. They are used in the treatment of conjunctivitis, comeal ulcer, and other superficial infections of the eye. See the Summary Drug Table Select Ophthalmic Preparations and Chapter 6 for additional information on the sulfonamides. 

Lincomycins bacteriostatic activity is based on the inhibition of the bacterial proteic synthesis. Lincomycin A in particular have been largely employed in clinical therapy of infections caused by micoplasmas, Gram-positive bacteria, and cocci but it presents a lot of side effects overcome by 7-clindamycin (Fig. 21), a semi-synthetic drug with larger spectrum of action and major antibacterial activity. 

Linezohd (Zyvox) is an oxazolidinone, a tive-membered heterocychc ring that forms the core of the hnezohd structure. The approval of hnezohd by the FDA in 2000 marked the first new structural class of antibacterial introduced into medical practice in the United States in 40 years. It is notable for its activity against methicillin-resistant Staph aureus, MRSA, and vancomycin-resistant Enterococcus faecium, VRE. It is bacteriostatic rather than bactericidal but finds significant use in patients with an intact immune system. Like several other classes of antibacterials, linezolid is an inhibitor of protein synthesis. It interacts specifically with the RNA component of a bacterial ribosome subunit to prevent initiation of protein synthesis. 

Gindamydn has antibacterial activity similar to that of erythromycin. It exerts a bacteriostatic effect mainly on gram-positive aerobic, as well as on anaerobic pathogens. Gindamycin is a semisynthetic chloro analogue of lin-comycin, which derives from a Streptomyces species. Taken orally, clindamycin is better absorbed than lincomycin, has greater antibacterial efficacy and is thus preferred. Both penetrate well into bone tissue. 

A considerable number of enzymes occupy a central and crucial role in the activity of drugs. Dihydrofolate reductase, an enzyme involved in purine and amino acid biosynthesis, is the target of antibacterial sulfanilamides, which act both as bacteriostatics and antimalarials. These drugs act on the enzyme in different ways, some being so-called antimetabolites (i.e., reversible enzyme inhibitors). Some diuretics act on carbonic... 

Antibacterial agents may be classified as bacteriostatic or bactericidal (Table 51-3). For agents that are primarily bacteriostatic, inhibitory drug concentrations are much lower than bactericidal drug concentrations. In general, cell wall-active agents are bactericidal, and drugs that inhibit protein synthesis are bacteriostatic. 

The bacteriostatic activity of a series of substituted trans-3-benzoylacrylic acids has been successfully correlated by Hansch linear free energy relations involving polar and partition substituent constants. The activity-lipophilicity relations for this series closely parallel those found previously for other antibacterial agents, with an ideal lipophilic character for gram-positive cells of 6.1 and, for linear dependence, a slope of 0.7. A polar reaction constant, p, of about —0.6 to —0.7 is given. A possible mode of action for these acids and their related substituted cis- and trans-3-benzoyl acrylic acids and esters is discussed as an enzyme-inhibitor interaction. 

Concurrent administration with phenylbutazone increases plasma concentrations, but lowers tissue concentrations, of penicillin G. Bacteriostatic antimicrobial agents, such as chloramphenicol and the tetracyclines, antagonize the antibacterial activity of penicillin G. 

---