Bacterial diseases are very common globally. Recent advances in Medical Sciences proved that bacteria are not only involved with acute and chronic diseases but also in dreadful diseases like carcinoma of gall bladder, liver, oral cavity, etc. So, for proper treatment correct diagnosis of the species of bacteria involved is very essential.The purpose of this book is to have an insight into the intricacy of different bacterial species involved in various pathologies affecting human, which will ultimately direct us to proper diagnosis and accurate treatment.