The fourth edition of  Textbook of Microbiology and Immunology  is an extensively revised edition , a healthy mixture of the old and the new contents. Many of the old traditional chapters have been retained with addition of new information along with the inclusion of new chapters more in line with the on-going changes in the syllabus and concepts in Medical Microbiology .While doing so, this book has blended the traditional organism-based learning and a syndrome based approach to infectious disease, together with the introduction of new and modified chapters incorporating the latest information in this field. The book provides an extensive coverage of fundamental topics in general and medical microbiology. The book also lays due emphasis on clinical microbiology with special focus on syndrome based approach to infectious diseases. It includes the basic concepts of microbiology as well as the recent updates and developments in the field of medical microbiology.