Lecture 19 Civil war soldier o Nematodes would crawl into the wound of the soldiers laying in the mud and they were carrying an organism called a luminescent bacteria which they gave into the wound o Example of symbiosis resides in the worm until it finds an environment it can effect Normal flora More bacteria on body then human cells in body by factor of ten o Distinctive for different regions of body o Influenced by host cell structure physiology Ex aerobic organisms could live on surface of skin o Fluctuates On monthly or yearly basis o Responds to environmental changes Right place right time and the bacteria can make you ill 10 bacteria for every human cell 1 g human feces people on earth o May contain opportunistic pathogens o Disease can result if a microbe s virulence is greater than the relative resistance of Q Which is true the host Microbes and Man o Interact With each other With other types With you directly o Build communities Biofilms often form in inconvenient places ex catherter tubes They can cause disease or be beneficial to us Biofilms can survive saliva mouthwashing etc o Microbes use us as a vessel of reproduction Population of organisms normally found on the body of a healthy Bacterial host interactions o Normal Flora individual Dynamic Divers Aerobes facultative anaerobes anaerobes can be inside the mouth for example o Resident flora organisms that you normally expect to find there all the time o Transient flora organisms that you find there intermittently you touch something and its own your skin until you wash your hands not everything grows on you it must evolve for this to happen Some resident microbiota chart o Research study was done on women with yeast infections these work sex workers These women couldn t wait three days to not have sex In the control group of women the pill worked great o Upper Respiratory Tract The nose is cooler than the rest of the resp system and has some unique microbiota The trachea and bronchi have a sparse microbiota compared to the nose and mouth The alveoli of the lungs which are too small to depict in this illustration have no natural microbiota they are axenic o Upper digestive tract Microbes colonize surfaces of teeth gingival lining of cheeks and pharynx and are found in saliva in large numbers Dozens of species have never been identified o Lower Digestive tract The bacteria are mostly strict anaerobes though some facultative anaerobes are also resident o Female urinary and reproductive systems Microbiota change as acidity in the vagina changes during menstrual cycle The flow of urine prevents extensive colonization of the urinary bladder or urethra o Mall urinary and reproductive systems The flow of urine prevents extensive colonization of the urinary bladder or urethra o Eyes and skin Microbiota live on the outer dead layers of the skin and in hair follicles and pores of glands The deeper layers dermis and hypodermis are axenic Tears wash most microbiota from the eyes so there are few compared to the skin Q Which part of the body is likely to have NO microbial normal flora o Answer The blood o The mouth stomach and genitourinary tract are all exposed to at some part to the environment Microbial cells interact o The blood is a closed system getting infections in the blood is very dangerous o Symbiosis living together o Mutualism both bacteria and host derive some sort of benefit o Commensalism bacteria benefit but the host is neutral o Parasitism bacteria benefit it is negative for the host Benefits of Normal Microbiota o Gnotobiotic germ free animals free of microorganisms Usually they have poorly developed immune system Requirements for vitamins K and B because bacteria give us some of our Increased susceptibility to pathogens vitamins in our stomach o Some microbes cause disease sometimes but most microbes do not and many are beneficial to humans Can help pathogens from colonizing etc Some microbes cause disease sometimes Biofilms o Host combat microbes by the host defense immunology o Microbes cause disease by pathogenic microbiology and microbial pathogenesis o We study the transmission of disease by epidemiology o Microbes attach to surfaces recognize presence of population quorum sensing start to form slime form a biofilm o Attachment microbes attach to surface could be anything intestinal wall catheter tube etc o Colonization they start to make slime often polysacarides etc allows the bacteria to grow in 3 dimensions o Growth they form a biofilm o Biofilms help support the growth of bacteria the slimes themselves sugar and protein mixtures can also serve as a protective mechanism against harm from organisms Pathogens o Able to cause disease perturbation from normal Infectious disease Caused by a transmissible agent o Must overcome host defenses Host Pathogen interactions o Usually the scales tip in favor of us there is a scale that ways human health and usually it is in our favor o Human are able to or have Normal flora Defenses Nonspecific Specific Treatment Antibiotics Prevention Vaccines o Microbes in their favor Have virulence factors specifically designed to beat human defenses Rapid growth Large numbers what they cant beat with smarts they can overwhelm human defenses with Synergies organisms can communicate with each other than work o When the scale tips in the favor of the microbe this is when we say we have a together disease What does a bacterium have to do to cause a disease o Establish an infection adhere colonize grow o Invade tissue breach anatomical barriers o Evade host defenses o Damage Host toxins Establish cause of infectious disease diagram of cookes postulate o o Compare mice that have died of an infectious disease with mice that have not died of disease healthy mice o Infect healthy mice with supposed virulent agent if it was this agent that killed the mouse would die Portals of entry o Whatever holes that we have in our skin already o Ears eyes nose cut or insect bite urethra placenta can cross into the placenta if pathogen enters the mother Anus vagina mouth Once an organism gets in it needs to recognize a specific set of cells or tissue Done by finding something usually found on host cells o Ex carbohydrate molecule on host cell Virulence colonization o Compete with normal flora o Acquire nutrients o Escape local immunity organisms like to go where immune cells do not usually o Avoiding host immune killing mechanism ex some bacteria are able to grow inside the host own cells this is