Host-Microbe Relationships

Transcription

1 Host-Microbe Relationships ALL PARTS of the body open to the external environment are extensively colonized Skin, Mouth, Respiratory Tract (not to deep in health adults cilliated epithelial cells beating upward), GI tract Urogenital tract 1

2 Host-Microbe Relationships Care Free and Germ Free Let colonization begin! Colonized Alright! Start with Lactobacillus from mom as the baby passes through the vagina Then from the external environment VERY RAPID COLONIZATION Normal healthy adult == 1 x 10^13 TOTAL CELLS COMPRISE THE BODY 10 Trillion ISH BUT Has 1 x 10^14 bacterial cells or 100 Trillion on them It has been calculated that the normal human houses about 10^12 bacteria on the skin, 10^10 in the mouth, and 10^14 in the gastrointestinal tract. The latter number is far in excess of the number of eukaryotic cells in all organs which comprise the human host. 2

3 In a healthy animal, internal tissues, e.g. blood, brain, muscle, etc.,normally free of microorganisms. Surface tissues, e.g. skin and mucous membranes, -- constantly in contact with environmental organisms become readily colonized by certain microbial species. WRITE THIS ON THE BOARD The mixture of organisms regularly found at any anatomical site is referred to as the normal flora (Microbiota). Normal flora of humans exceedingly complex consists of more than 200 species of bacteria. Makeup of the normal flora depends upon various factors, genetics, age, sex, stress, nutrition and diet of the individual. DOWN TO HERE The normal flora of humans consists of a few eukaryotic fungi and protists, and some methanogenic Archaea that colonize the lower intestinal tract, but the Bacteria are the most numerous and obvious microbial components of the normal flora. 3

4 Host-Microbe Relationships Commensalism One organism benefits while the other is unaffected many bacteria Mutualism Symbiosis, both organisms benefit Parasitism one organism benefits at the expense of the other Mutualism GI tract E. Coli provides us with B vitamins and vitamin K lactic acid bacteria produce certain B-vitamins 4

5 Terms of Infectious Disease Pathogen Disease causing Microorganism Pathogenicity Virulence Infection Invasion or colonization of body by a pathogen Disease change from a state of health Genus Bordetella (pertussis, parapertussis [whooping cough kills 100 s of thousands of children a year world wide] and bronchiseptica) PATHOGEN Microbial parasite Outcome depends on PATHOGENICITY ability of the parasite (pathogen) to cause damage to the host AND the host resistance or susceptibility to the parasite Pathogenicity varies greatly among individual pathogens. The quantitative measure of pathogenicity is VIRULENCE VIRULENCE = expressed as the cell number (pathogens) that will elicit a pathogenic response in the host within a given time period. NEITHER Virulence nor relative resistance of the host are static. These items change frequently. Interaction of the Host-Parasite is very dynamic.. Invasion by and multiplication of pathogenic microorganisms in a bodily part or tissue, which may produce subsequent tissue injury and progress to overt disease through a variety of cellular or toxic mechanisms. the invasion of the body by pathogenic microorganisms and their multiplication which can lead to tissue damage and disease Disease Also can be simply the damage or injury to the host that impairs host function caused by pathogen 5

6 Etiology of Infectious Disease Koch s Postulates Neisseria gonorrhoeae, the bacteria that causes gonorrhea, Koch s postulates used to show association of a particular microorganism with a particular disease Steps culture. 1.) Same pathogen must be present in all cases of a disease 2.) Pathogen must be isolated, and grown in pure 3.) Pure culture put into a susceptible host must reproduce the disease symptoms 3.) Same organism must be reisolated Doesn t Always work for ALL Organisms WHY???? - fastidious organisms Won t work if can t grow on artificial media Treponema pallidum (syphilis), Mycobacterium leprae (leprosy) Chlamydia sp. Viruses What about must be able to isolate pure culture and re-infect susceptible host HIV??? Ethical considerations 6

7 Classification of Infectious Diseases Communicable Disease Spreads from one host to another Can be directly or indirectly transferred chickenpox, tuberculosis Noncommunicable Disease Not spread from one host to another Only causes disease when introduced into the body tetanus Consider them to be contagious diseases if they are easily spread Mycobacterium tuberculosis Clostridium tetanii 7

8 Classification of Infectious Diseases Acute Disease Develops rapidly Short lived flu Chronic Disease Develops slowly Long lasting Acute Chronic Chlamydia pneumoniae infection and cardiovascular disease. The bacteria cause a common respiratory infection but Chlamydia-atherosclerosis connection exists Helicobacter pylori gastritis and peptic ulcers 8

9 Classification of Infectious Diseases Emerging Infectious Disease New disease or Old disease which is reemergent Causes of emergence or re-emergence Global Warming Global Village Changes in animal population Breakdown of Public Health (lack of infrastructure) Global Warming Malaria and Cholera. --Vibrio cholerea Typical of warm climates Warm climates may enter new ranges as global temperatures increase Global Village SARS Changes in ease of rapid transportation (air specifically) Changes in Animal Population Increase deer population, increase deer tick population and increase chances or rate of infection Breakdown of Public Health diptheria increase in Russia Corynebacterium diphtheriae 9

10 Classification of Infectious Diseases Nosocomial Infectious Disease Infection acquired as a result of a hospital stay Main chain of infection is via hospital personnel 5-15 % of all patients acquire 20,000 deaths per year Contributing Factors Presence of microorganisms in hospital Weakened patients Primary Nosocomial Pathogens E. coli, S. aureus, P. aerginosia Escherischia coli Staphylococcus aureus --Staphylococcus aureus causes a variety of suppurative (pus-forming) infections and toxinoses in humans. It causes superficial skin lesions such as boils, styes and furunculosis; more serious infections such as pneumonia, mastitis, phlebitis, meningitis, and urinary tract infections; and deep-seated infections, such as osteomyelitis and endocarditis. S. aureus is a major cause of hospital acquired (nosocomial) infection of surgical wounds and infections associated with indwelling medical devices. S. aureus causes food poisoning by releasing enterotoxins into food, and toxic shock syndrome by release of superantigens into the blood stream. Pseudomonas aeruginosa --Pseudomonas aeruginosa is an opportunistic pathogen, meaning that it exploits some break in the host defenses to initiate an infection. It causes urinary tract infections, respiratory system infections, dermatitis, soft tissue infections, bacteremia, bone and joint infections, gastrointestinal infections and a variety of systemic infections, particularly in patients with severe burns and in cancer and AIDS patients who are immunosuppressed. Pseudomonas aeruginosa infection is a serious problem in patients hospitalized with cancer, cystic fibrosis, and burns. The case fatality rate in these patients is 50 percent. 10

11 Reservoirs of Infection Human Reservoirs Principle reservoir for many pathogens Some people are carriers Animal Reservoirs zoonoses Nonliving Reservoirs Soil fungi, C. tetanii H 2 O Vibrio cholera Food -- Salmonella AIDS, diptheria, gonorrhea, streptococcal infections Carriers carry the organism without themselves showing any disease symptoms Typhoid Zo ON o-seas RABIES Lyme Disease West Nile Non-Living Clostridium tetanii H20 and Food often involve fecal contamination 11

12 Transmission of Diseases Contact Transmission Person to Person patient medical personel Indirect Contact Transmission Infected person fomite uninfected person Droplet Transmission Infected person droplet nuclei uninfected person Contact physical contact between infected and unifected host touching, kissing, sexual intercourse (STD s) Nosocomial gloves and hand washing can prevent Staph infections most common Indirect Contact Fomite inanimate object or substance which can transmit infections disease towel, toy syringe Droplet Transmission coughing sneezing formation of an aerosol carrying infectious microorganisms 12

13 Transmission of Diseases Vehicle Transmission Usually food, water and air Vector Transmission Insects and arthropods as vectors Malaria -- Plasmodium a protozoan mosquito human Plague Yersinia pestis rat flea human Food foodborne infections and intoxications E. coli and Salmonella Contaminations from improper cooking, or improper microbial control procedures Water - Fecal contamination Pathogens the transmitted to new host cholera, dysentery Airborne small droplets which remain airborne can remain airborne for > 1m from the host Tuberculosis can be spread this way VECTOR Malaria - mosquitoes Plasmodium (a protozoan) Plaque - Rat Flea Yersinia pestis (bacterium) 13