First published in 1978, Ananthanarayan and Paniker’s Textbook of Microbiology has been a trusted textbook on microbiology for more than four decades and has evolved with the rapidly changing field of medical microbiology. To stay abreast of recent developments across the global and local infectious disease spectra, the new Competency-Based Medical Education (CBME) curriculum is aimed at integrating microbiology into the system-based approach to human disease. The eleventh edition of Ananthanarayan and Paniker's Textbook of Microbiology has been revised to address this restructuring of the curriculum and to make it better suited for the shorter course duration and system-based integration. Chapters have been pruned without compromising on essential elements which have been presented in a lucid style and flow for an easy and enjoyable reading experience. Several clinical and laboratory images have been updated and line diagrams included for better visual impact and comprehension. Recent advances in disease detection, molecular diagnosis, quality control, infection prevention and control, public health and epidemiology and preventive strategies including national programmes have been brought up to date. An entire chapter (chapter 60) has been devoted to the essence of the competency-based integrated approach to system-wise infectious diseases. This chapter delves into the entire gamut of organisms involved in infectious diseases commonly affecting various systems of the human body and will pave the way for the study of pathogenic microorganisms as individuals and as groups. The traditional approach to the learning and understanding of the microbe–host–environment interaction, pathogenesis, clinical presentations, diagnosis, treatment and prevention of infections has been retained.