Diseases: Pathogens that affect humans

What is a disease? A disease is an abnormal condition that affects the body of an organism. Infectious diseases are often caused by microbial pathogens. Pathogens are infectious agents (such as bacteria, viruses, fungi, or microbes) that can produce poisons (toxins) that result in sickness (fever, headache, vomiting, diarrhea or conditions that destroy body tissues.) Microbiology is the study of microscopic organisms, some of which cause disease.

Types of diseases: Very common Most are preventable Usually leads to a long course of illness Usually develops slowly Usually progresses over time –Heart disease –Diabetes –Cancer –Asthma 1. Chronic: A disease lasting three months or more, that cannot be prevented or cured by medicine. 2. Infectious: Diseases that can be carried and transmitted by humans or animals by different routes. These include: A. bacteria B. viruses C. fungi D. Micro-organisms (protists like Amoeba)

Bacteria: Unicellular (single-celled) organisms Prokaryotic (no nucleus) Microscopic (very small) Rapidly reproducing (asexual, short gestation period-- can produce another generation in minutes) Can be found on most materials and surfaces – Billions on and in your body right now E. Coli O157:H7 can make you very sick. Streptococcus can cause strep throat. This bacteria helps you digest food.

Flagellum Pili DNA (plasmid) Cell membrane ribosomes peptidoglycan Cell wall Bacteria : Bacteria are Prokaryotes (they do not have a nucleus!)

Bacteria Shapes 1.Bacilli - rod-shaped 2. Cocci - spherical 3. Spirilla - spiral

How do bacteria reproduce? 1. Binary fission - doubles in size, replicates DNA, cell divides 2. Conjugation - genes move from one cell to another 3. Spore formation - endospore germinates and grows

Why are bacteria important? 1.Decomposition - break down materials into simple materials 2. Nitrogen fixation - converting N 2 (gas) to a form plants can use 3. Human uses - - food production - digestion of wastes - vitamin production - production of hormones such as insulin

A Closer Look – Helpful Bacteria Pediococcus - used in production of fermented meats Leuconostoc cremoris – used in the production of buttermilk and sour cream Lactobacillus casei – found in human intestines and mouth to improve digestion Lactobacillus bulgaricus – used in the production of yogurt USDA NIFSI Food Safety in the Classroom© University of Tennessee, Knoxville 2006

Pathogens: Bad Bacteria! Bacterial Diseases 1.Damage cells and tissues (use them for food) 2. Release toxins into blood stream Mycobacterium tuberculosis Streptococcus pneumonia

Examples of Bacterial Pathogens Salmonella Staphylococcus aureus Campylobacter jejuni E. coli O157:H7 What shape are these bacteria? Cocci, bacilli, or spiral? USDA NIFSI Food Safety in the Classroom© University of Tennessee, Knoxville 2006

Some Diseases caused by bacteria: Rabies Lyme Disease Bacterial meningitis Leprosy Tetanus Tuberculosis Strep Throat Lyme Disease bacteria

Controlling Bacteria: Preventing Infections 1.Sterilization 2.Disinfectants 3.Food storage and processes 4.Wash your hands 5.Antibiotics

Viruses – Cellular Pirates Adenovirus showing Varicella zoster virus icosahedral shape causes chickenpox

Characteristics of Viruses Obligate Intercellular Parasite (not alive) - Must reproduce(replicate) inside a host Structure - Nucleic Acid – DNA or RNA - Protein coat – called a capsid -Envelope – some contain a layer of membrane taken from a host cell Mutate Rapidly Host Specific - can only infect one type of cell Small – from 20nm to 250nm - most are too small to be seen with a light microscope

Virus Structure

Retroviruses Contain RNA and not DNA - to be able to take over a host cell, the retrovirus must be able to convert the RNA into DNA - to accomplish the conversion, retroviruses insert an enzyme called Reverse Transcriptase into the host cell

Bacteriophage Bacteriophages are viruses that infect bacteria - they are responsible for transduction in bacteria

What do viruses do? In Animals: attack and destroy certain cells or cause cells to change function (can cause cancer) – Can’t be treated with antibiotics (no cell wall)

Diseases Caused by Viruses: AIDS Influenza (flu-different strains) Common cold (many different types!) Polio Chicken Pox (Varicella) Small Pox Yellow Fever Viral meningitis West Nile syndrome Ebola

What works against viruses? Vaccines or immunizations By pre-infecting the body with small amounts of a weakened or dead part of a particular virus, our body can build up antibodies that will fight it for our lifetime * Antibiotics DO NOT work against viruses because they attack cell walls (which viruses do not have)

Fungal Diseases Fungi that cause disease are mostly single-celled. Examples: Yeasts, molds, mildews (most do not cause disease) Candida: Yeasts, skin infections, and infections of bones, lungs, heart Ringworm: Caused by dermatophytes— infections on neck, scalp, groin or feet. Athlete’s foot is an example of ringworm on the feet. Molds: allergic reactions, asthma, pneumonia

Methods of Infection: Airborne route: Bacteria and viruses are transmitted through small particles in the air. They must be able to live outside the body for a long period of time. They enter the body via the respiratory tract. Common cold Influenza (the flu) Tuberculosis (TB)

Methods of Infection: Fecal-Oral route: Organisms that live in the digestive tract. Usually come from contaminated food. Lack of hand washing spreads the organisms. Improper cooking and storing of food can spread: E. coli bacteria Salmonella bacteria Hepatitis A virus

Methods of Infection: Direct contact: Person-to-person Touching Kissing Sexual contact Body lesions (sores or open areas)

Methods of Infection: Indirect contact: Person is infected by coming into contact with contaminated surfaces such as: Doorknobs and light fixtures Computers Toys Phones

Methods of Infection: Vector-borne: Transmitted by animals or insects, such as: Mosquitoes (West Nile virus) Raccoons (rabies) Ticks (Lyme disease) Vector-any agent (person, animal, microorganism) that carries an infectious pathogen or disease to another living organism

Methods of Infection: Waterborne (Borne by droplets): Transmitted by large droplets from the eyes, nose, or mouth, usually too large to be airborne for long. – Measles – SARS (Severe Acute Respiratory Syndrome – noted outbreak in China)

Epidemic vs. Pandemic. An epidemic is an outbreak of a disease that affects a disproportionately large number of individuals within a population, community or region at the same time. (example—typhoid) A pandemic is an epidemic of an infectious disease that is spreading through human populations across a large region, continent or even worldwide (examples: smallpox, tuberculosis, flu of 2009).

Primary prevention: Activities that take place before a disease or injury is present to prevent it from occurring. For example: Vaccines and Immunizations: By pre- infecting the body with small amounts of a particular virus/pathogen, the body can build up antibodies that will fight it for a lifetime (Vaccination for chicken pox) Education on hygiene--avoidance of disease-favorable conditions (i.e. the dangers of smoking) Preventative measures (hand washing, safe handling, use of disinfectants )

Secondary prevention: Isolation--Isolating those who are ill – Stay home from school if you are sick Monitoring--Testing for certain diseases like scoliosis or tuberculosis. Drug treatments —treating diseases with medicine, like diabetes and high cholesterol. Activities that take place once the disease has already occurred to help treat, reverse, or stop the illness. For example:

A New Problem: Antibiotic Resistance Overuse of antibiotics can lead to the bacteria developing a resistance to the antibiotic. Solutions: 1.ONLY use current antibiotics when absolutely necessary 2.Develop new antibiotics that can treat illness and bacterial diseases and use them carefully