The text has been thoroughly updated to include the latest developments. It is illustrated with coloured computer-drawn figures clinical photographs and photo micro graphs. New figures have also been added. Each chapter ends with key facts and important questions. Emphasis has been given on oral manifestations of each microorganism. In the chapter on hepatitis viruses emphasis has been made on various hepatitis viruses and dentistry. The text is presented in a simple and lucid manner. About the Author Dr. D. R. Arora Ex-Professor & Head Department of Microbiology Postgraduate Institute of Medical Sciences Rohtak—124001 (Haryana) India;Lead AssessorFaculty Member and Member Technical Committee National Accreditation Board for Testing and Calibration Laboratories (NABL) New Delhi (India); Principal Assessor National Accreditation Board for Hospitals & Healthcare Providers (NABH) New Delhi (India);Reviewing Officer National Registration Board for Personnel and Training (NRBPT) Quality Council of India New Delhi (India); has more than 39 years of teaching experience in microbiology including parasitology to medical dental and nursing undergraduate and postgraduate students. He has supervised a number of PG students of Ph.D. M.D. and M.S. In appreciation of outstanding research carried out by him in India on bacteriocins of Klebsiella pneumoniae he was awarded Smt. Kunti Mehrotra Award of Indian Association of Pathologists and Microbiologists in 1983. In recognition of significant contribution for the advancement of medical sciences. Dr. Brij Bala Arora Ex-Senior Professor & Head Department of Pathology PGIMS Rohtak has more than 37 years of teaching experience to medical and dental undergraduate and postgraduate students.Her research on AgNOR staining technique received international importance and paper on morphometric analysis of AgNOR in lymph node lesions was published in Advances in Clinical Pathology 6:95-99 2002. The results of her research on malaria parasite and haemosiderin iron deposition in lymph nodes have drawn the attention of theInternational Scientific Community.