Bacterial Infection and immunit Xiao-KuiGuo
Bacterial Infection and Immunity Xiao-Kui GUO
Symbioses ● Commensalism:one partner benefits and the other is neither harmed nor benefited ● Mutualism:both partners benefit. o Parasitism: one partner benefits at the expense of區出”“ the other
Symbioses ⚫ Commensalism: one partner benefits and the other is neither harmed nor benefited. ⚫ Mutualism: both partners benefit. ⚫ Parasitism: one partner benefits at the expense of the other
Role of the resident flora Members of the resident fora in the intestinal tract synthesize vitamin K and aid in the absorption of nutrients Members of the resident flora on mucous mem branes and skin may prevent colonization by pathogens and possible disease through"bacterial interference The normal flora may antagonize other bacteria through the production of substances which inhibit or kill nonindigenous species The normal flora stimulates the development of certain tissues, i.e., the caecum and certain lymphatic tissues(Peyer's patches) in the GI tract The normal flora stimulate the production of cross reactive antibodies
Role of the resident flora • Members of the resident flora in the intestinal tract synthesize vitamin K and aid in the absorption of nutrients. • Members of the resident flora on mucous membranes and skin may prevent colonization by pathogens and possible disease through “bacterial interference”. • The normal flora may antagonize other bacteria through the production of substances which inhibit or kill nonindigenous species. • The normal flora stimulates the development of certain tissues, i.e., the caecum and certain lymphatic tissues (Peyer's patches) in the GI tract • The normal flora stimulate the production of crossreactive antibodies
o Hospital acquired infection: Infections acquired during hospital stays o Pathgen: A microorganism capable of causing sisease Nonpathogen: a microorganism that does not cause disease; may be part of the normal flora o Opportunistic pathogen: An agent capable of causing disease only when the host's resistance is impaired (ie, when the patient is"immunocompromised) o Pathogenicity: The ability of an infectious agent to cause disease o Virulence: The quantitative ability of an agent to cause disease. Virulent agents cause disease when introduced into the host in small numbers. Virulence involves invasion and toxigenicity LD so(age/sex/health /route of entry, etc o LD50: The number of pathogens required to cause lethal disease in half of the exposed hosts is called an Ldso ID50: The number of pathogens required to cause disease(or, at least, infection) in half of the exposed hosts is called the ID o Adherence(adhesion, attachment) the process by which bacteria stick to the surfaces of host cells Once bacteria have entered the body, adherence is a major initial step in the infection process. The terms adherence, adhesion, and attachment are often used interchangeabl o Invasion: The process whereby bacteria, animal parasites, fungi, and viruses enter host cells or tissues and spread in the body Toxigenicity: The ability of a microorganism to produce a toxin that contributes to the development of disease
⚫ Hospital acquired infection:Infections acquired during hospital stays. ⚫ Pathgen: A microorganism capable of causing sisease. ⚫ Nonpathogen: A microorganism that does not cause disease; may be part of the normal flora. ⚫ Opportunistic pathogen: An agent capable of causing disease only when the host’s resistance is impaired (ie, when the patient is “immunocompromised”). ⚫ Pathogenicity: The ability of an infectious agent to cause disease ⚫ Virulence: The quantitative ability of an agent to cause disease. Virulent agents cause disease when introduced into the host in small numbers. Virulence involves invasion and toxigenicity. LD 50 (age /sex /health /route of entry, etc ) ⚫ LD50: The number of pathogens required to cause lethal disease in half of the exposed hostsis called an LD50. ⚫ ID50: The number of pathogens required to cause disease (or, at least, infection) in half of the exposed hosts is called the ID50 ⚫ Adherence(adhesion, attachment): the process by which bacteria stick to the surfaces of host cells. Once bacteria have entered the body, adherence is a major initial step in the infection process. The terms adherence, adhesion, and attachment are often used interchangeably. ⚫ Invasion: The process whereby bacteria, animal parasites, fungi, and viruses enter host cells or tissues and spread in the body. ⚫ Toxigenicity: The ability of a microorganism to produce a toxin that contributes to the development of disease
Koch's postulates oo Isolated ●Koch’ s Postulates diseased not health Molecular Koch’s people Postulates Growth o Molecular guidelines for pure culture Establishing Microbial ● Induce disease Disease causation susceptible animals ● Re-isolated susceptible animals
⚫ Koch’s Postulates ⚫ Molecular Koch’s Postulates ⚫ Molecular Guidelines for Establishing Microbial Disease Causation Koch's postulates ⚫ Isolated – diseased not healthy people ⚫ Growth – pure culture ⚫ Induce disease – susceptible animals ⚫ Re-isolated – susceptible animals