Inhibition of gram-positive

The mechanism of antibacterial activity is through inhibition of gram-positive bacterial cell-wall synthesis thus, the penicillins are most effective against actively multiplying organisms. Because mammalian cells do not have a definitive cell-wall stmcture as do bacteria, the mammalian toxicity of the penicillins is low. Allergic phenomena in patients following sensitization may occur. 

Essential oils are active in the inhibition of Gram positive and Gram negative bacteria, yeast, and fungi. These oils usually show weak to moderate activity when compared with chemical biocides such as antibiotics, quaternary ammonium salts, or chlorinated phenols such as triclosan. When the major components are isolated, they usually show improved activity compared to the essential oils. The test methods employed commonly determine inhibition activity via an MIC, but do not usually address the issue of MLC (minimum lethal concentration) or how quickly viable organisms are reduced over a short period of time. In order to determine this, other test methods need to be employed. Differences in... 

Thymus sp. (thyme) is a common spice that has been extensively studied [116-123]. Thyme is one of the earliest medicinal plants in western herbal medicine. The essential oil isolated from this spice is active in the inhibition of Gram positive and Gram negative bacteria as well as yeast and fdamentous fungi. A major constituent of thyme oil is thymol (91), which has been implicated as the molecule responsible for the activity of this essential oil. Other materials isolated from thyme oil that possess biological activity include carvacrol (92), bomeol (93), p-cymene (37), a-pinene (13) and camphene (94). Thymol (91) was shown to be the most active, followed by carvacrol (92), borneol (93), / -cymene (37), a-pinene (13), and camphene (94) [121]. 

In recent years there has been a growing awareness of the potential value of marine and river sediments as sources of actinomycetes that produce useful metabolic products. Approximately 16% of the strains obtained from marine sediments displayed antimicrobial activity, consisting primarily of the inhibition of Gram-positive bacteria [9]. Actinomycetes were also isolated from sediments obtained from the Hudson River. Of 165 isolates obtained, 22 exhibited significant antifungal activity. All but three of the active substances contained polyene antibiotics and most of the bioactive actinomycetes were identified as streptomycetes [10]. These observations of the production of antibiotics resulted from laboratory cultivation it is not known whether the bioactive actinomycetes are also capable of producing antibiotics in the aquatic environments. 

Numerous bacteriocins are produced by lactic acid bacteria (Klaenhammer, 1988), but only a few bacteriocins have been found in propionibacteria (Lyon and Glatz, 1991, 1993 Giinstead and Barefoot, 1992). Recently, 14 dairy propionibacteria were screened for catalase-insentitive, protease-sensitive inhibition of Gram-positive and Gramnegative bacteria (Ratnam et al., 1998). Bacteriocin production was identified in 57% of these cultures. 

MacConkey s medium. This was introduced in 1905 to isolate Enterobacteriaceae from water, urine, faeces, foods, etc. Essentially, it consists of a nutrient medium with bile salts, lactose and a suitable indicator. The bile salts function as a natural surface-active agent which, while not inhibiting the growth of the Enterobacteriaceae, inhibits the growth of Gram-positive bacteria which are likely to be present in the material to be examined. 

Parthenolide was found to be located in the glands on the surface of the leaves and seeds and was shown to have antimicrobial properties [33]. It was able to inhibit the growth of Gram-positive bacteria, yeast and filamentous... 

Pharmacology The tetracyclines are bacteriostatic. They exert their antimicrobial effect by inhibition of protein synthesis. Tetracyclines are active against a wide range of gram-positive and gram-negative organisms. 

Pharmacoiogy Inhibits cell-wall synthesis in susceptible strains of gram-positive and gram-negative bacteria and in Mycobacterium tubercuiosis. 

It is mainly bacteriostatic and inhibits the growth of gram positive organisms which includes staphylococci, streptococci, pneumococci, C. diphtheriae and B. anthracis. Like erythromycin it act by interfering with protein synthesis. 

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