Lecture 11 - Microbes and Disease PDF

BIOL1030 Biochemistry & Microbiology Microbes and Disease Microorganisms and Disease Humans have 30 trillion cells in their body Humans are covered with 40 trillion microorganisms!!! Can include bacteria, fungi, protozoans, and viruses This population constitu...

BIOL1030 Biochemistry & Microbiology Microbes and Disease Microorganisms and Disease Humans have 30 trillion cells in their body Humans are covered with 40 trillion microorganisms!!! Can include bacteria, fungi, protozoans, and viruses This population constitutes our Normal Flora or Human Microbiota The normal flora is a mixture of pathogenic and harmless organisms Comprised of resident (usually occupy a particular body site) and transient microflora (colonize people for hours to weeks but do not establish themselves permanently) Normal flora do not cause disease Symbiosis When two organisms develop a relationship The larger organism is the host, the smaller is the symbiont  Symbiosis Commensal – beneficial to the MO but does not harm the host Bacteria on the skin Bacteria in the respiratory and gastrointestinal tract Mutualistic – bacteria and host benefit from the relationship Assist the immune system Assist in nutrient metabolism, vitamin production, and waste processing. Parasitic - the bacteria benefit while the host is harmed Blood flukes (shistosomiasis) a.k.a. bilharizia Tape worms Competition – One species outcompetes another Symbiosis and Normal Flora Do not typically cause illness in humans IF you have a healthy immune system Can become opportunistic that are non- pathogenic that act as a pathogen in certain circumstances and invade the system of individuals Those with immune deficiencies, elderly, etc. Example: Bacteria of the nose include Streptococcus pneumoniae and Staph aureus Generally benign and cause no issues If they colonize other areas of the body they can be highly pathogenic and KILL Human Microflora Benefits of the human microflora Include chemical secretions such as vitamin B & K Stimulates the immune system Assists with the recognition of foreign bodies Prevents pathogenic bacteria from colonizing tissue Produce bacteriocins Large Intestine: Bifidobacterium – probiotic Escherichia coli Bacterioides Lactobacillus Opportunistic Bacteria Humans can be infected with MOs that seize an advantage Weakened immune system, wounds, altered microbiota Generally do not cause disease in humans but Introduction to areas where they should not be found Lack of competition from commensals Cause infection and disease Agents such as: Pseudomonas aeruginosa Salmonella spp. Streptococcus/Staphylococcus Symbiosis and Normal Flora The location of normal flora can be as follows: Human skin Armpits/Groin/Soles of Feet Hair Follicles/Sweat Glands Respiratory tract Nose/Nostrils Buccal Area Digestive System Urogenital Tract Symbiosis and Normal Flora The location of normal flora depend on several factors: Moisture level pH level Temperature Salinity The presence of waste products Presence of Microbes Symbiosis and Normal Flora The Digestive Tract The flora of the digestive tract is affected by several factors Your age The type of diet that you consume Type and frequency of medications Cultural and lifestyle conditions Fast food versus Home Cooking Type of dietary intake Smoking Stress Obesity Geographic location Symbiosis and Normal Flora Stomach is first line of defense against invasive flora Gastric juice contains enzymes and HCl Kill and disrupt the growth of bacteria Some bacteria highly adapted to live in the low pH Helicobacter pylori The small intestine has bacteria in the jejunum and ileum Staphylococcus, Lactobacillus, & Streptobacillus Colon (large intestine) contains the highest numbers of pathogens Mostly opportunistic - E. coli >600 species in the colon Anaerobes live in the colon and digest wastes in the bowel ~50% of your fecal mass is bacteria Symbiosis and Normal Flora Urogenital System Contains your urinary and reproductive systems Generally kidneys, ureters, urethra and bladder are sterile The opening of the urethra to the outside has microbes Generally comprised of bacteria, fungi and viruses Constant flushing of urinary tract prevents buildup Prevents infections UTIs occur from change in normal flora or blockages Infection from inflammation Microorganisms and Disease Infectious is a disease caused by an organism that can be transmitted from person to person Communicable Can occur through ingestion, bites, coughs, etc Non-infectious is a diseases caused by genetics, the environment, lifestyle and not disease Non-communicable – cannot be passed from person to person Stress, genetics, allergies, nutritional/metabolic issues Microorganisms and Disease Infectious Agents Can be viruses, bacteria, protozoans, fungi and worms We are only concerned with the first four Process of infection occurs in stages: Exposure to infectious particles Establish a focus of infection Colonize some surface and overcome host defenses Surfaces can be skin or mucosal membranes Skin, gastrointestinal, respiratory, urogenital tract  Course of Infectious Disease Incubation period Time between pathogen entry and development of signs and symptoms. Prodromal stage Mild, non-specific signs and symptoms. Illness period Disease is most severe and display signs and symptoms. Convalescence Recovery stage. Pathogenicity The pathogenicity of an agent: The ability of a pathogen to cause disease in an organism Pathogenic organisms have differing abilities to cause illness Differing levels of pathogenicity High Pathogenicity – easily cause disease Yersinia pestis, Listeria sp., Clostridium tetani Low Pathogenicity – does not easily cause disease Staphylococcus aureus (opportunistic) Virulence The virulence of an agent: The severity of an illness caused by a pathogen All pathogens cause disease Differing levels of virulence High virulence- pathogens cause severe illness Low virulence- pathogens cause less severe illness Pathogenicity versus Virulence Pathogens = ability to cause disease Virulence = severity of illness caused by pathogen Virulence All Pathogens can cause disease Pathogens with HIGH virulence cause a severe illness Pathogens with a LOW virulence case less severe illness Example: Colds Common influenza causes fever, cough, sore throat and runny nose Generally over in a matter of days H5N1 causes similar symptoms Contribute to pulmonary failure Pneumonia, multi organ failure H5N1 > virulence than Common influenza  Bacteria as Infectious Agents Have structures for adhesion to cells Adhesins and pili Adhesins are surface recognition materials Allow the bacteria to attach to a variety of surfaces Epithelial lining, skin, etc Example: Gangrenous Stomatitis Fusiforme bacillus infection of mucosa Ulcerative necrosis Bacteria as Infectious Agents Produce enzymes that cause infection and spread Hyaluronidase – degrades material holding cell together Allows tissue penetration Coagulase – clots blood and stops WBCs from killing Secrete toxins into host tissues Stimulate a MASSIVE immune response that kills the host Eubacteria cause > 50% of all human disease We produce interferon in response to bacterial toxins Causes a fever Sources of Infection: Reservoirs The variety of sources where infection can be stored until passed to a host A reservoir where the pathogen can survive until transmission Reservoir can be a living or non-living object Common cold can be transmitted by hugging someone Transmission of body fluids can transmit infection Blood, semen, vaginal fluids, saliva, tears Food borne illness Pathogen exists on food item Humans as Reservoirs Pathogens can survive quite happily in humans A person can be an active carrier of infection May not show symptoms Known as an asymptomatic carrier Examples include: Typhoid Fever – consuming infected food Pneumonia – viral/bacterial transmission Polio – can be spread by an immunized individual AIDS – No visible sign of infection Human Carriers - Classifications Passive – carry the pathogen but never show outward sign of the disease Active – have recovered or does not show the disease but can transmit indefinitely Incubatory – can transmit during the incubation period of the disease (measles, mumps, polio) Pathogen is incubating but not evident in carrier Convalescent – can transmit while recovering from the disease (cholera, typhoid fever, diphtheria) Clinically recovered but can still transmit Typhoid Mary – Asymptomatic Carrier  Animals as Reservoirs Microorganisms can infect both humans and animals Transmission from animal to human = zoonoses Monkeys can act as a reservoir for malaria Cats can act as a reservoir for disease Toxoplasmosis/rabies Toxoplasma gondii and rabies virus Dogs can act as reservoirs for disease Toxocariasis – roundworms Ringworm – fungal Rabies – rabies virus Non-Living Reservoirs Soil – bacterial transmission – Clostridium sp. Tetanus, gangrene Water – Vibrio cholera – secretes a toxin Extreme diarrhea and dehydration Cryptosporidium – weight loss, nausea, diarrhea Air – Anthrax, chicken pox, Influenza, measles, TB Portals of Entry/Exit Portals of Entry An MO has to enter tissues to cause an infection Entry points are called portals of entry Examples: Eyes, ears, cuts, abrasions, mouth Portal of Exit Disease spreads when infectious agents leave the host All exit points are called portals of exit Examples: Eyes, ears, anus, mouth, blood/body fluids  Modes of Transmission Transmission of a disease occurs when a reservoir spreads infection from a portal of exit to a portal of entry Passed on to another organism There are three means of transmission: 1. Contact 2. By vehicles 3. By vectors  Contact Transmission Contact: occurs when an infectious disease is transmitted from an infected individual to a new host. Contact can be indirect, direct or droplet Direct occurs from body contact Horizontal – shaking hands, kissing, sexual contact Vertical – from parent to offspring via egg/sperm, through the placenta, breast milk or birth canal Example: Herpes Simplex I &II Baby is exposed traveling through birth canal Fecal-Oral – unwashed hand to mouth transfer Indirect occurs from contact with non-living objects Also called fomites Examples include soiled tissue, gloves, dishes, doorknobs, eating utensils, toys, soap, lipstick, lip gloss, money Contact Transmission Contact: occurs when an infectious disease is transmitted from an infected individual to a new host. Droplet – obtained from the aerosol from sneeze, cough or talking to an infected individual A proximity of ~1 m is sufficient for transfer Vehicle Transmission Vehicle: non-living carrier of a pathogen From reservoir to a host Waterborne diseases - cholera Airborne transmission - flu Food borne transmission - salmonella Vector Transmission Vector: transfer from reservoir to host via a living organism Examples include: Mosquitos – Plasmodium (malaria) Fleas – Yersinia pestis – bubonic plague Lice – mange/dermodectic mange Flies – Trypanosomiasis – African Sleeping Sickness Nosocomial Transmission Nosocomial Infections – a type of infection acquired in a health care facility Secondary to the original condition Appear shortly after admission or within 14 days of discharge Latrogenic Infections – infections that are the result of medical treatment Caused by healthcare workers, surgeons, or physicians Cross infection of patients, materials from surgery left behind  Nosocomial Infections Patients acquire during their stay in a healthcare facility These infections typically occur 48 hours or more after admission or within 30 days of receiving healthcare treatment Can be caused by bacteria, viruses, fungi, or other pathogens Most common is the bacterium Staphylococcus aureus. Other examples: Escherichia coli, Enterococci, Candida Normally found on the skin and mucous membranes. Antibiotic-resistant strains such as methicillin- resistant Staphylococcus aureus (MRSA) can be especially dangerous and difficult to treat.