Preface

This book contains precisely referenced chapters, emphasizing antibacterial agents with clinical practicality and alternatives to synthetic antibacterial agents through detailed reviews of diseases and their control using alternative approaches. The book aims at explaining bacterial diseases and their control via synthetic drugs replaced by chemicals obtained from different natural resources which present a future direction in the pharmaceutical industry. The book attempts to present emerging low cost and environmentally friendly drugs that are free from side effects studied in the overlapping disciplines of medicinal chemistry, biochemistry, microbiology and pharmacology.

> **Varaprasad Bobbarala**  Chief Scientist at Krisani Biosciences India

**1** 

*Serbia* 

**Antibacterial Activity of Naturally** 

*Labaratory of Microbiology, Department of Biology and Ecology, Faculty of Science, University of Kragujevac, Kragujevac*

**Occurring Compounds from Selected Plants** 

Man is in constant contact with a large number of different bacteria which temporarily or permanently inhibit his body creating temporary or permanent community. Relations which are thus established are various and very complex, from those positive to those whose consequences for man are extremely negative. Very often, both on and in man's body, bacteria which have the ability to cause an infection are present. This ability of pathogenic bacteria is reflected in possession of certain pathogenicity factors. A set of factors which enable successful invasion and damage of the host are: toxins, surface structures and enzymes. Between the host and the pathogen very complex relations are established whose

Infections caused by bacteria can be prevented, managed and treated through anti-bacterial group of compounds known as antibiotics. Antibiotics are natural, semi-synthetic or synthetic compounds that kill or inhibit the growth of bacteria. When bacteria are exposed to an antibiotic, they doubly respond: i) they are sensitive what cause the inhibition of their

The resistance of bacteria to antibiotics can be natural (intrinsic) or acquired. Natural resistance is achieved by spontaneous gene mutation. The acquired resistence occurs after the contact of bacteria with an antibiotic as a result of adaptation of a species to adverse environmental conditions. In such population, an antibiotic as a selective agent, acts on sensitive individuals, while resistant survive and become dominant. Bacteria gain antibiotic resistance due to three reasons namely: (i) modification of active site of the target resulting in reduction in the efficiency of binding of the drug, (ii) direct destruction or modification of the antibiotic by enzymes produced by the organism or, (iii) efflux of antibiotic from the cell (Sheldon, 2005). The evolution of antibacterial resistance in human pathogenic and commensal microorganisms is the result of the interaction between antibiotic exposure and the transmission of resistance within and between individuals. It is especially interesting the phenomenon of horizontally gene transfer. Extrachromosomal DNA material, so-called plasmids, often carry genes of resistance and can transfer information within and between the individuals of the same or related bacterial species, thus also spreading the resistance. Transformation, transduction and conjugation represent the horizontal gene transfer

income depends on host's characteristics as well as on pathogen's characteristics.

growth, division and death or ii) they can remain unaffected or resistant.

mechanisms of resistance between the bacteria.

**1. Introduction** 

Olgica Stefanović, Ivana Radojević, Sava Vasić and Ljiljana Čomić
