This book provides a comprehensive account of the several bacterial infections and the antibiotics used for their treatment. Infectious diseases are major public health problems. The emergence and spread of microbes causing severe infectious diseases such as diarrhea, respiratory tract infections, bacterial meningitis, sexually transmitted diseases and tuberculosis have become a common incidence. Bacterial infections are known to be treated with antibiotics. New antibiotics are needed to combat these bacterial pathogens, but progress in developing them has been slow. The recent rise in the resistance (a survival benefit to microbes) makes it harder to eliminate infections from the body. This shows the continuous and urgent need to discover new antimicrobial compounds with diverse chemical structures and novel mechanisms of action for new and re-emerging infectious diseases.Therefore, natural sources of antibiotics and the need for new antibiotics have been thoroughly discussed. some antibacterials with novel mechanisms of action have also been discussed.