exam 1

• host defense: complex balance, requires recognition of self vs non-self, protects against disease while maintaining beneficial relationships
• saprophytic: free living microbes
• parasitic: microbes requiring a host
• some saprophytes may exist in higher order hosts due to better living conditions
• 99.99% bacteria live outside a host
• host-microbe interactions are dynamic interactions based on the characteristics of the microbe and the host
• host-microbe interactions are dependent on host range
• only a fraction of microbial species are associated with humans
• human microbiome normal flora include commensals, opportunistic, and pathogenic microbes
• commensals have a beneficial or neutral relationship with the host
• opportunistic microbes, given the right circumstances can lead to infection
• pathogenic microbes always cause disease
• human microbiome influencing factors include: diet, antibiotics, anatomic abnormalities, genetic differences, hormonal changes, age, and lifestyle
• the human microbiome is beneficial because it provides protection from pathogens, stimulation of gut maturation, stimulation of innate and adaptive immunity, expansion of nutritional diversity, and digestion of complex carbohydrates
• the human microbiome provides protection from pathogens because stable ecosystems resist introduction or overgrowth of pathogens at epithelial surfaces
• consequences of the microbiome: foot odor, flatulence, body odor, bad breath, opportunistic disease, transfer antibiotic resistance genes
• disease is any condition in which the normal strucutre or functions of the body are damaged or impaired
• physical injury and disabilities are not classified as disease
• disease causes include infection, genetics, environmental, and immune responses
• infection: successful colonization of host by a microorganism, can lead to disease
• pathogens: organisms that cause disease
• virulence: degree of pathogenicity
• stages of pathogenesis: exposure, adhesion, invasion
• exposure: encounter with pathogen, requires portal of entry to gain access to target tissue
• adhesions: attachment to body cells, mediated through adhesins, binds to receptors on host cells, or biofilms can act as adhesions
• adhesins: fimbriae, bacterial flagella, cilia, viral capsid or envelopes, viral spikes, capsules
• biofilms can act as adhesions with extrapolymeric substance (EPS)
• invasion: mediated by production of exoenzymes are toxins, dissemination throughout local tissues or body, damage host to spread deeper
• exoenzymes or toxins are examples of virulence factors
• emia: dissemination through blood stream
• sepsis: bacteria multiplying in blood
• infection: successful invasion and multiplication
• local infection: confined to a small area
• focal infection: spread of local infection to secondary location
• systemic infection: disseminated throughout the body
• pathogen transmission requires a portal of exit
• secondary infection: infection by one pathogen leads to infection by another
• incubation period: exposure of pathogen, beginning to adhere
• prodromal stage: multiplication of the pathogen
• illness: immune system response causing symptoms