Medical Microbiology Lecture 2 Dr. Saleh M Y OTH PhD Medical Molecular Biotechnology and Infectious Diseases 02/10/2010 IMS - MSU
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.
The composition of the normal flora varies in different body sites.
Ultimately, the flora composition is determined by ecological factors including the presence of receptors of host cell surface for bacterial adherence, pH, oxygen, availability of nutrients, water, host defense and personal hygiene.
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
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.
Carrier state; colonization with a pathogen Pathogen ; any organism that has the potential to cause disease
Many bacteria also can use transferrin, lactoferrin, ferritin or hemin as a source of iron.
Mechanisms of Bacterial Pathogenesis Virulence factors are bacterial strategies or products which contribute to each of these steps leading ultimately
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