Principles and approaches -- Laboratory methods used for strain typing of pathogens: conventional and molecular techniques -- Laboratory methods used for strain typing pathogens: PCR-based strain typing methods -- Analysis of similarity and relatedness in molecular epidemiology -- Distinguishing epidemic and endemic occurrence of infectious diseases -- Stratification and refinement of data in epidemiologic investigations -- Distinguishing pathovars from nonpathovars: escherichia coli -- Distinguishing pathovars from nonpathovars: streptococcus pneumoniae -- Distinguishing pathovars from nonpathovars: helicobacter pylori -- Hospital infections: staphylococcus aureus -- Hospital infections: gram-negative bacteria -- Identifying a pathogen's biologic determinants of disease transmission