This manual is a modern teaching tool focused on the study of Gram-positive bacteria. It provides students with a useful learning resource for understanding these bacterial families. This medical microbiology manuscript has been extensively revised and updated, and its content has been adapted to meet the current curriculum requirements for veterinary medicine students. For that, We have tried to adopt the same writing plan for all the courses, which includes: Historical; Classification; Habitat; Resistance; Morphology; Cultural Characteristics; Biochemical Characteristics; Antigenic Characteristics; Virulence Factors; Pathogenicity; Identification and Antibiotic Susceptibility