Types of chemotaxins – C5a attracts neutrophils and monocytes – Made by bacteria Peptide clipped off N-terminus (beginning with N￾formylmethionine) during peptide maturation after protein synthesis

Constitutive Defenses Barriers to entry – See Schaechter text, Table 6.1 Mucous membranes—covered by protective layer of mucus – Mechanical and chemical barrier that allows proper functioning

Operon fusion: transcriptional – Promoter from foreign gene – Translational sequence from reporter gene

Choosing an Animal Model Pathogen may not affect animal at all -OR￾may give different symptoms Given disease may have a number of animal models, none of which fully satisfies characteristics of disease

General aspects – Remember definition: organisms frequently found on or within body of healthy individuals – Most are bacteria, but some are viruses, fungi, and protozoa

Microbial pathogenesis—process of causing disease Colonization—presence of microbes at site of body – Does not imply tissue damage or disease symptoms – Does imply invasion of site and multiplication

American Legion Convention in 1976 in Philadelphia hotel – Respiratory distress and fever – 200 affected – 34 died

General Aspects Ecology – Found throughout the environment Very simple nutritional requirements – Not usually in normal flora unless hospitalized or immunocompromised

Diversity of species Ecology – Found worldwide in soil, water, vegetation, and microbial flora of animals and humans – Some are always associated with disease

Comparison of Meningococcus and Gonococcus Pathobiology Similarities: – Both diploccocci – Share about 80% DNA – Neither makes exotoxin; both make endotoxin – Both are relatively good colonizers