Infection and Disease Where Are Pathogens Reservoirs Places where pathogens persist Animal Transmitted to humans when in contact with reservoir o Ex Rabies West Nile Disease of the brain rare sporadic virus Human Carrier of pathogen that doesn t show symptoms and sheds pathogen into the environment o Chronic Carriers Long term months years o Intermittent Carriers Short term o Ex Typhoid first carrier disease polio Non living Pathogens in water and soil o Water Cholera persists in lakes and ponds o Soil Tetanus and fungi Mechanism of Infectious Disease Microbes cause disease when someone ingests a certain amount of pathogens to get disease 1 Pathogens access host 2 Pathogens multiply and reproduce within the host 10 000 100 000 cells 3 Overcomes defenses 4 Damage to tissues causes the disease Disease Mechanisms Toxins Chemical that alters how a cell works and has and adverse affect on the cells function and physiology Degradative Enzymes Break down chemical components of cells or tissues Ex Collagen Cells get damaged by own immune system when trying to fight off disease Ex Tuberculosis a bacterium gets into lungs and sits there while the immune system tries to fight to get rid of disease While fighting large masses are produced called tubercles that damage the lungs and blood vessels Patterns of Damage Local Disease stays in one area Ex skin infections Systemic Damage is spread out and affects multiple organs Ex Heart infection spreads to kidneys and tissues causing a more serious disease Types of Infection Acute Short term days to weeks Comes on very rapidly like the common cold Chronic Long lasting months to years Infects slowly Virulence The intensity of a pathogen Infectivity The lower the infectivity the more virulent it is Invasiveness The deeper in the body the more invasive Ex flesh eating bacteria Pathogenic Potential Severity Incubation Period No symptoms the time it takes for microbe to get where it needs to go and replicate Prodromal Stage First symptoms show up ex fatigue weak tired Period of Invasion Symptoms of disease sneezing coughing Height of Infection Disease reaches plateau and cant get worse Convalescent Period Get put of antibiotics and symptoms go down LD50 Lethal dose how many cells it takes to kill and organism The lower the LD the more virulent the microbe is Bacterial Virulence Factors Fimbriae Attaches bacterial to host cells Without Fimbriae bacteria is mostly harmless Ex Neisseria Gonorrhoea STD Streptococcus Pyogenes strep throat Capsules Outer layer that surrounds the bacteria protects cell from phagocytosis Cell Wall Components Techoic and Lipotechoic acids in gram positive bacteria LPS lipopolysaccharide Endotoxin in Gram negative bacterial Mycolic Acids Protects bacteria from phagocytic cells like a capsule Exoenzymes Used by microbes to break down connective tissue chemicals invade deeper into the body and gain more nutrients Lipase breaks down lipids Collagenase collagen Elastase elastic connective tissue Hyaluronidase hyaluronic acid Endotoxins LPS Found in every species of gram negative bacteria Made of lipids and carbs Exotoxins Very potent toxin that can affect you in nano gram amounts made of proteins Hemolysins red blood cells Leukocidins white blood cells Neurotoxins Nervous system o Botulism Nerves in skeletal system o Tetanus Neurons in spinal cord Toxins with multiple effects Affect multiple organs o Diphtheria A childhood disease that grows in throat and spreads to multiple organs through bloodstream Ex heart tissue
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