Microorganisms and Disease How does the human body and various microorganisms interact in terms of disease?

Infectious Disease skin, mucous membranes, antibodies bacteria can produce capsules, enzymes, and toxins infectious disease is the primary cause of death world-wide : influenza pandemic killed more than 20 million people world-wide and 500,000 people in the United States

Readings question #1: Describe the “chain of infection”.

Infection vs. Disease Infection: “the entry, establishment and multiplication of pathogenic organisms within a host” Disease: an abnormal state in which part or all of the body is not properly adjusted or is incapable of performing normal functions; any change from a state of health

Factors that Influence the Occurrence of Disease 1) virulence of the organisms 2) portal of entry of the pathogen 3) number of organisms present 4) the resistance of the host

Virulence of Organisms virulence: “relative power of an organism to produce disease” resistance host pathogen contamination: “the act of introducing disease germs or infectious material into an area or substance”

Virulence (cont’d) true pathogen: “an organism that due to its virulence is able to produce disease: attenuation: “dilution or weakening of virulence of a microorganism, reducing or abolishing pathogenicity” pathogenicity: “the state of producing or being able to produce pathological changes and disease”

Virulence (cont’d) indigenous flora: “synonymous with normal flora, indicates the microbial population that lives with the host in a healthy condition” opportunists: “an organism that exists as part of the normal flora but may become pathogenic under certain conditions” drug-fast: “resistant, as in bacteria, to the action of a drug or drugs”

MRSA Methicillin-resistant Staphylococcus aureus

MRSA 2005: 94, 360 people; 18,650 died (CDC) 85%- healthcare 66% outside of hospital “colonized” but not infected invasive medical procedures, weakened immune systems sepsis, surgical site infections, pneumonia

MRSA (cont’d) mode: human hands staph generally harmless unless they enter through a cut or wound 1990: CA-MRSA (community-associated) preventable

Types of Infections and Diseases exogenous infections: “originating outside an organ or part” endogenous infections: “produced or arising from within a cell or organism” acute diseases: symptoms develop rapidly but may only last for a short period of time chronic diseases: develop slowly and are likely to continue or recur for long periods of time

Infections and Diseases (cont’d) communicable diseases: “a disease that may be transmitted directly or indirectly from one individual to another” endemic: “disease that occurs continuously in a particular region, but has low mortality” epidemic: “appearance of an infectious disease or condition that attacks many people at the same time in the same geographical area”

Infections and Disease (cont’d) pandemic: “a disease affecting the majority of the population of a large region or one that is epidemic at the same time in many different parts of the world” sporadic: “a disease which occurs occasionally or in scattered instances” noncommunicable diseases: do not spread from one host to another

Readings question #2: Define local, focal, and general infections, and give an example of each.

Infections (cont’d) primary: “the first infection that a host has after a period of health” secondary: “infection caused by a different organism than the one causing the primary infection mixed: “infection caused by two or more organisms” blood: viremia; bacteremia

Readings question #3: Define septicemia and toxemia and include an example of each. What are the symptoms/characteristics for septicemia and toxemia?

Factors Influencing Virulence Readings question #4: Describe toxins, exotoxins, and endotoxins, and give an example of each. Capsules and Endospores

Sources of Infection Human Reservoirs: “carriers” Universal Precautions Animal Reservoirs: “zoonoses” Environmental Reservoirs: Vibrio cholera Salmonella typhi

Transmission of Infections Direct: viral respiratory disease, staphylococcal infections, hepatitis A, measles, scarlet fever, STDs, AIDS, infectious mononucleosis - hand washing, gloves etc. Indirect: Readings question #5: Describe the primary mechanisms of indirect contact. Include examples with each mechanism. What are fomites?

Portal of Entry 5 portals of entry: 1) skin and mucous membranes 2) respiratory tract 3) digestive tract 4) genito-urinary tract 5) placenta

Skin and Mucous Membranes membranes line the respiratory tract, gastrointestinal tract, genitourinary tract, and conjunctiva skin is one of the largest organs of the body - hair follicles and sweat gland ducts parenteral route: microorganisms are deposited directly into the tissues

Respiratory Tract easiest and most frequently traveled portal of entry airborne pathogens sneezing, coughing, touching contaminated surfaces and then touching the mouth or nose, dust particles pathogenic bacterial spores may be inhaled

Digestive Tract Food, water, contaminated fingers HCl and enzymes in the stomach bile and enzymes in the small intestine poliomyelitis, hepatitis A, typhoid fever, amoebic dysentery, giardiasis, shigellosis, cholera

Genitourinary Tract pathogens that are contracted sexually genital warts, chlamydia, herpes

Placenta CMV: cytomegalovirus 10% infants: premature delivery, jaundice, enlarged liver and spleen, microcephaly, seizures, rash, feeding difficulties hearing, vision, neurologic, and developmental problems no vaccine hand washing, not sharing eating utensils, avoid kissing or intimate contact with CMV+

Portals of Exit secretions, excretions, discharges, shed tissue related to the infected part of the body microbe generally uses the same portal for entry and exit respiratory: TB, whooping cough, pheumonia, scarlet fever, meningococcal meningitis, chickenpox, measles, mumps, small pox, influenza

Portals of Exit (cont’d) gastrointestinal: feces- salmonellosis, cholera, typhoid fever, shigellosis, amoebic dysentery, poliomyelitis saliva - rabies, mumps, infectious mononucleosis genitourinary: secretions from penis and vagina- STDs urine- tyhphoid fever brucellosis

Portals of Exit (cont’d) skin or wound infections - impetigo, skin ringworm, herpes simplex, warts Infected blood: insects, contaminated needles and syringes insects – yellow fever, plague, tularemia, malaria con. needles & syringes – AIDS, hepatitis B

Number of Organisms Present Third factor

Resistance of the Host mechanical defenses physiological defenses chemical defenses

Mechanical Defenses Skin: epithelium (epidermis), sebaceous glands, dryness, “necrobiosis” Eyes: lacrimal apparatus Saliva: cleansing action Respiratory Tract: mucus, ciliated epithelium Urinary Tract: flushing action

Physiological Defenses Inflammation: pus Fever: degrees Phagocytosis: phagocyte ingests material

Chemical Defenses Lysozome: enzyme that breaks down cell walls of gram-positive bacteria and some gram-negative bacteria Sebum: sebaceous glands, oily substance, protective film, lowers skin pH Gastric Juice: HCl, enzymes, mucus, acidic Interferon: eukaryotic cells, surface receptors

Immunology Latin immunis “to exempt” Why is it that some people tend to be sick more often than others? Why can two people eat the same infected chicken, and only one person contracts food poisening? children, elderly, immunocompromised

Antigens “a foreign substance that stimulates the formation of antibodies that react specifically with it” substance that provoke a specific response Antibodies: “glycoprotein substance developed by the body in response to, and interacting specifically, with an antigen. Also known as immunoglobulin.”

Antigen-Antibody Reactions 1) destroy pathogens by neutralizing the toxins the pathogen produces 2) coat the pathogen with a substance that attracts phagocytes by forming a substance that clumps the antigens together 3) prevent the pathogen from adhering to the body’s cells

Types of Immunity Natural (Innate) Acquired: Naturally Acquired – active, passive Artificially Acquired - active: vaccines - passive: antibodies immune serums

Hypersensitivity (Allergy) “an acquired, abnormal immune response to a substance (allergen) that does not normally cause a reaction” Immediate: 2 – 30 minutes – systemic (shock, breathing difficulties) – Localized (hay fever, asthma, hives) Delayed: 1-2 days – TB skin test, contact dermatitis