This document summarizes key concepts from a medical microbiology lecture, including definitions of infection, pathogens, commensals, and nonpathogens. It discusses the roles of normal flora in protecting the host and how their composition is determined. It also outlines colonization, carriage states, pathogenicity, and virulence factors. Specific examples are provided of bacterial adherence mechanisms like pili and adhesins in E. coli and S. aureus. The document also briefly discusses bacterial growth requirements, iron acquisition, and toxin production.

1. Medical Microbiology Lecture 2 Dr. Saleh M Y OTH PhD Medical Molecular Biotechnology and Infectious Diseases 02/10/2010 IMS - MSU

2. Infection: The growth of microorganisms in the host without causing damages to the host. Definaations Bacteria may be divided into three types based on their potential to cause diseases; - pathogens , - commensals , and - nonpathogens . Must to know: Morbidity, mortality, infections, parasite, host, vector, fomite, contagious (infectious) disease, epidemic, endemic, pandemic, Zoonosis, Epizootic, Attack rate.

6. Some tissues, organs are dense with normal flora, others are normally sterile a. colonized sites i. alimentary/intestinal tract ii. upper respiratory tract iii. distal genitourinary tract iv. skin b. normally sterile sites i. blood ii. CSF iii. interstitial fluid and spaces iv. lymph

7. Disease ; damage caused by presence of microorganisms or their products. Colonization - presence of microorganisms without disease at that point. This term applies to surfaces only , i.e., the blood cannot be colonized and host cells with intracellular infection are not colonized.

8. Carrier state; colonization with a pathogen Pathogen ; any organism that has the potential to cause disease

11. Pili and Afimbrial Adhesins Pili - fimbrial Adhesins Afimbrial Adhesins (No pili) Adherence and colonization ……..

19. Mechanisms of Bacterial Pathogenesis Virulence factors are bacterial strategies or products which contribute to each of these steps leading ultimately

20. Functions and stages of pathogens and disease 1. encounter 2. entry 3. spread (+/-) 4. multiplication 5. evasion of host defenses 6. damage 7. outcome a. transmission to new host (+/-) b. recovery or not

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