M I C R O B I O L O G Y WITH DISEASES BY BODY SYSTEM SECOND EDITION Chapter 14 Infection, Infectious Diseases, and Epidemiology Symbiotic Relationships Between Microbes and Their Hosts ? Symbiosis means ?to live together? ? We have symbiotic relationships with microorganisms ? 100 trillion bacterial & fungal cells on each of us ? called ?normal flora? or ?normal microbiota? ? Types of symbiosis ? Mutualism: both benefit (+/+) ? e.g., sea anemone & clownfish ? Commensalism: one benefits, other neutral (+/0) ? e.g., barnacles & whales ? Parasitism: one benefits, other harmed (+/-) ? e.g., heartworm & dog Symbiotic Relationships Between Microbes and Their Hosts [INSERT TABLE 14.1] PREDATION Herbivory Symbiotic Relationships Between Microbes and Their Hosts ? Normal Microbiota in Hosts ? Also termed normal flora and indigenous microbiota ? Refers to the organisms that colonize the body?s surfaces without normally causing disease ? Two main types 1. Resident microbiota 2. Transient microbiota Symbiotic Relationships Between Microbes and Their Hosts [INSERT FIGURE 14.2] Symbiotic Relationships Between Microbes and Their Hosts ? Normal Microbiota in Hosts (cont.) 1. Resident microbiota ? 100s of species of bacteria & fungi live in and on our bodies ? Are a part of the normal microbiota throughout life ? Most are commensal ? Exact combination of species & size may vary somewhat, but resident flora are characteristic & permanent Symbiotic Relationships Between Microbes and Their Hosts ? Normal Microbiota in Hosts (cont.) 2. Transient microbiota ? Remain in the body for only hours to months before disappearing ? Found in the same regions as resident microbiota ? Cannot persist in the body (long-term) ? Competition from other microorganisms ? Elimination by the body?s defense cells ? Chemical or physical changes in the body Symbiotic Relationships Between Microbes and Their Hosts Symbiotic Relationships Between Microbes and Their Hosts ? Normal Microbiota in Hosts (cont.) ? Acquisition of normal microbiota ? Development in the womb is generally free of microorganisms (i.e., axenic) ? Microbiota begins to develop during the birthing process ? Much of one?s resident microbiota is established during the first months of life ? Restore normal flora ? After antibiotic regimen (e.g., penicillin, cyclosporin, amoxicillin) ? Yogurt with active/live cultures ? Other probiotics Symbiotic Relationships Between Microbes and Their Hosts ? How Normal Microbiota Become Opportunistic Pathogens ? Opportunistic pathogens are normal microbiota or other normally harmless microbes that can cause disease under certain circumstances ? Conditions that provide opportunities for pathogens ? Immune suppression ? Changes in the normal microbiota ? changes in relative abundance of normal microbiota provides an opportunity for a member to thrive and cause disease ? Introduction of normal microbiota into unusual site in the body ? NOTE: all of these are a change in the normal flora Symbiotic Relationships Between Microbes and Their Hosts Toxic shock syndrome = a change in vaginal flora due to increased O2(g) & protein (blood) levels ? highly aerobic, fast growth; caused by an opportunistic pathogen Symbiotic Relationships Between Microbes and Their Hosts ? How Normal Microbiota Become Opportunistic Pathogens (cont.) ? Immune Suppression ? Disease ? Malnutrition ? Emotional or physical stress ? Extremes of age ? Use of radiation or chemotherapy ? Use of immunosuppressive drugs ? NOTE: all of these are a decrease in ability for the immune system to counteract the disease ? How Normal Microbiota Become Opportunistic Pathogens (cont.) ? Changes in the Normal Microbiota ? Microbial antagonism or competition ? normal flora use nutrients, take up space, and release toxic waste products ? Make it less likely that other microbes can compete ? Due to: ? Long-term antimicrobial treatment ? Hormonal changes ? Stress ? Changes in diet ? Exposure to overwhelming numbers of pathogens Symbiotic Relationships Between Microbes and Their Hosts ? How Normal Microbiota Become Opportunistic Pathogens (cont.) ? Introduction of a Member of the Normal Microbiota into an Unusual Site in the Body ? Each body site contains only certain species of microbiota Symbiotic Relationships Between Microbes and Their Hosts Capabilities of a Pathogen ? Koch?s Postulates: ? Maintain a reservoir ? Leave its reservoir (transmission) ? Enter a host through a portal of entry (infection) and adhere to the surface of the host ? Evade defenses, multiply, and affect body function ? Leave the body and return to its reservoir or enter a new host Reservoirs of Infectious Diseases of Humans ? Most pathogens cannot survive for long outside of their host ? Sites where pathogens are maintained as a source of infection are termed reservoirs of infection ? Three types of reservoirs 1. Animal reservoirs ? e.g., chickens carry the influenza virus, shed in feces?H2O ? This is why chickens are NOT allowed in most cities!! 2. Human reservoirs ? Humans with active disease ? Carriers: asymptomatic but still have the pathogen ? e.g., HIV, Shigella spp. 3. Nonliving (i.e., abiotic) reservoirs Reservoirs of Infectious Diseases of Humans ? Animal Reservoirs ? Zoonoses ? diseases that are naturally spread from their usual animal host to humans ? Acquire zoonoses through various routes ? Direct contact with animal or its waste ? Eating animals ? Bloodsucking arthropods ? Humans are usually dead-end host to zoonotic pathogens How cute! Beautiful!! YUCK!!!! Reservoirs of Infectious Diseases of Humans [INSERT TABLE 14.3] Which animal(s) do you own??? Reservoirs of Infectious Diseases of Humans ? Nonliving (Abiotic) Reservoirs ? Soil, water, and food can be reservoirs of infection ? Presence of microorganisms is often due to contamination by feces or urine Modes of Infectious Disease Transmission ? Transmission is either from a reservoir or a portal of exit to another host?s portal of entry ? Three groups of transmission 1. Contact transmission ? Direct, Indirect, or Droplet 2. Vehicle transmission ? Airborne, Waterborne, or Foodborne 3. Vector transmission ? Biological or Mechanical Modes of Infectious Disease Transmission [INSERT TABLE 14.11] Modes of Infectious Disease Transmission ? Modes of Transmission 1. Contact ? Direct contact ? Typically involves body contact between hosts ? Self-inoculation ? Indirect contact ? Fomites: inanimate objects ? Fomites are not reservoirs; only transmit disease when people come into close contact with others (sharing same objects, etc) Modes of Infectious Disease Transmission ? Modes of Transmission 1. Contact (cont.) ? Droplet ? More human diseases transmitted by this mechanism ? Droplets expelled when we cough, sneeze, laugh, or talk ? Diseases spread rapidly through crowded populations ? Transmission via droplet nuclei that travel <1 meter ? Modes of Transmission 2. Vehicle ? Airborne ? Aerosols may contains pathogens on dust or inside droplets ? May come from sneezing, coughing, air conditioning systems, sweeping, mopping, changing clothes, or flaming inoculating loops ? Pathogens travel >1 meter ? Waterborne ? Important in spread of GI diseases ? Water can be reservoir or vehicle ? Fecal-oral Modes of Infectious Disease Transmission Modes of Infectious Disease Transmission ? Modes of Transmission 2. Vehicle (cont.) ? Foodborne ? Pathogens in & on foods that may be ? Poorly processed ? Undercooked (e.g., beef, chicken, pork, shellfish, turkey) ? ground beef ?vs- steak ? Fecal-oral ? Bodily fluid ? Blood, urine, saliva, & other bodily fluids ? e.g., herpes, HIV, gonorrhea ? Must contact conjunctiva or breaks in skin or mucous membranes ? Modes of Transmission 3. Vector ? Flies, mosquitoes, ticks, fleas, and lice ? e.g., Lyme disease, malaria, west nile ? Two types 1. Mechanical 2. Biological Modes of Infectious Disease Transmission Modes of Infectious Disease Transmission [INSERT TABLE 14.10] The Movement of Microbes Into Hosts: Infection ? Exposure to Microbes: Contamination and Infection ? Contamination ? the mere presence of microbes in or on the body ? Infection ? results when the organism has evaded the body?s external defenses, multiplied, and become established in the body ? Disease ? a condition which is different than normal good health ? NOTE: pop culture often uses the word ?infection? to describe an observable deviation from healthy ? e.g., ?I have an infection.? in reference to redness & swelling ? Yes, you do have a microbial infection. -BUT- What you?re experiencing/observing is the disease the pathogen is causing. The Movement of Microbes into Hosts: Infection ? Portals of Entry ? Sites through which pathogens enter the body ? Four major pathways 1. Skin 2. Mucous membranes 3. Placenta 4. Parenteral route The Movement of Microbes into Hosts: Infection [INSERT FIGURE 14.3] The Movement of Microbes into Hosts: Infection ? Portals of Entry (cont.) 1. Skin ? Outer layer of packed, dead, skin cells usually acts as a barrier to pathogens ? Some pathogens can enter through openings or cuts ? Others enter by burrowing into or digesting the outer layers of skin The Movement of Microbes into Hosts: Infection ? Portals of Entry (cont.) 2. Mucous membranes ? Line the body cavities that are open to the environment ? Provide a moist, warm environment that is hospitable to pathogens ? Respiratory tract is the most common site of entry ? entry is through the nose, mouth, or eyes ? Pathogens able to survive the acidic pH of the stomach may use the gastrointestinal tract as a route of entry The Movement of Microbes into Hosts: Infection [INSERT TABLE 14.4] The Movement of Microbes into Hosts: Infection ? The Role of Adhesion in Infection ? Process by which microorganisms attach themselves to cells ? Use adhesion factors (specialized structures or attachment proteins) ? Adhesion disks in some protozoa ? Suckers and hooks in some helminths ? Ligands/attachment proteins in viruses ? Adhesins in bacteria (fimbriae, flagella, and glycocalyces) ? Ability to change/block the ligand or receptor can prevent infection ? Interaction of ligand with host receptor can determine specificity ? Inability to make attachment proteins or adhesins renders the microorganisms avirulent ? Some bacterial pathogens interact with each other to form a biofilm REVIEW of MONDAY ? Symbioses ? Mutualism (+/+) ? Commensalism (+/0) ? Parasitism (+/-) ? Normal Flora/Microbiota ? Resident Microbiota: permanent ? Transient Microbiota: don?t persist i.e., ephemeral ? Different microenvironments = different flora ? Acquire Flora ? 1st few months of life ? Restore Flora ? yogurt, probiotics REVIEW of MONDAY ? Changes in Normal Flora/Microbiota ? Opportunistic Pathogens: can but don?t normally cause disease ? Change in relative abundances of an organism ? Immune System decrease ? Koch?s Postulates: pathogen capabilities ? Transmit, infect, cause disease, re-enter ? Pathogen Reservoirs: biotic (animals) & abiotic (water, soil) ? Zoonoses: pathogens that goes from animal to human ? a ?zoonotic disease? e.g., the bubonic plague, rabies REVIEW of MONDAY ? Disease (pathogen) Transmission ? Direct contact (human-to-human) ? Fomites e.g., grocery/shopping cart ? Aerosols ? Contamination, Infection, Disease ? Adhesion Factors allow pathogens to attach onto cells to cause disease [INSERT FIGURE 14.5] The Role of Adhesion in Infection Excellent drug targets to prevent infection [INSERT FIGURE 14.6] The Role of Adhesion in Infection The Nature of Infectious Disease ? Infection is the invasion of the host by a pathogen ? Disease results only if the invading pathogen alters normal functions of the body ? also referred to as ?morbidity? The Nature of Infectious Disease ? Virulence Factors of Infectious Agents ? Pathogenicity ? ability of a microorganism to cause disease ? Virulence ? degree of pathogenicity ? How ?dangerous? is it? ? Virulence factors include traits that allow the pathogen to cause disease ? Interact with a host and enable it to enter a host ? Adhere to host cells ? Gain access to nutrients ? Escape detection or removal by the immune system ? e.g., Bubonic plague (caused by Yersinia pestis) killed so many people because it was extremely virulent (i.e., high virulence) and its virulence factors were very effective The Nature of Infectious Disease [INSERT FIGURE 14.8] The Nature of Infectious Disease ? Virulence Factors of Infectious Agents (cont.) ? Include ? Adhesion Factors ? Biofilm Formation ? Extracellular Enzymes ? Toxins ? Antiphagocytic Factors (to evade immune responses) The Nature of Infectious Disease ? The Nature of Infectious Disease ? Extracellular enzymes ? Secreted by the pathogen ? Dissolve structural chemicals in the body ? Help pathogen maintain infection, invade further, and avoid body defenses ? Examples ? Hyaluronidase and collagenase ? Coagulase ? Kinases ? ?Extra-? means outside of The Nature of Infectious Disease ? Virulence Factors of Infectious Agents ? Toxins ? Chemicals that harm tissues or trigger host immune responses that cause damage ? Two types 1. Exotoxin: secreted, released during life 2. Endotoxin: within cells, released during death The Nature of Infectious Disease ? Virulence Factors of Infectious Agents (cont.) ? Toxins (cont.) 1. Exotoxin ? Many enter the bloodstream and exert their harmful effects far away from the site of production ? Destroy host cells or interfere with host metabolism ? Three principle types 1. Cytotoxin 2. Neurotoxin 3. Enterotoxin The Nature of Infectious Disease [INSERT FIGURE 14.9b] e.g., pathogen in brain, disease throughout body (from exotoxins) The Nature of Infectious Disease ? Virulence Factors of Infectious Agents (cont.) ? Toxins (cont.) 2. Endotoxin ? Produced only by Gram negative bacteria ? Released when cells die naturally or are digested ? Stimulate body to release chemicals that cause fever, inflammation, diarrhea, hemorrhaging, shock, and blood clotting ? Systemic effects This is how Gram (-) pathogens can still cause disease (even DEATH!) after they are killed by antibiotics The Nature of Infectious Disease ? Virulence Factors of Infectious Agents (cont.) ? Antiphagocytic Factors ? Certain factors prevent phagocytosis by the host?s phagocytic cells (evade immune system responses) ? Capsules ? Often composed of chemicals found in the body ? Can be slippery ? Antiphagocytic Chemicals ? Some prevent fusion of lysosome and phagosome ? M proteins resist phagocytosis ? Leukocidins directly destroy phagocytic white blood cells The Nature of Infectious Disease [INSERT FIGURE 14.9c] The Movement of Pathogens Out of Hosts: Portals of Exit ? Pathogens leave host through portals of exit ? Many portals of exit are the same as portals of entry ? Pathogens often leave hosts in materials the body secretes or excretes The Movement of Pathogens Out of Hosts: Portals of Exit [INSERT FIGURE 14.11] The Nature of Infectious Disease ? Manifestations of Disease: Symptoms, Signs, and Syndromes ? Symptoms ? subjective characteristics of disease felt only by the patient ? Syndrome ? group of symptoms and signs that characterize a disease or abnormal condition ? Signs ? objective manifestations of disease that can be observed or measured by others ? Asymptomatic, or subclinical, infections lack symptoms but may still have signs of infection The Nature of Infectious Disease [INSERT TABLE 14.5] The Nature of Infectious Disease ? The Stages of Infectious Disease ? Following infection, a sequence of events called the disease process occurs ? Many infectious diseases have five stages following infection 1. Incubation period 2. Prodromal period 3. Illness 4. Decline 5. Convalescence The Nature of Infectious Disease [INSERT FIGURE 14.10] The Nature of Infectious Disease [INSERT TABLE 14.9] ?food poisoning? Epidemiology of Infectious Diseases [INSERT FIGURE 14.16] 1 region ?VS- all over Epidemiology of Infectious Diseases ? Hospital Epidemiology: Nosocomial Infections ? Types of Nosocomial infections ? Exogenous ? pathogen acquired from the health care environment ? Endogenous ? pathogen arises from normal microbiota due to factors within the health care setting ? Iatrogenic ? results from modern medical procedures Epidemiology of Infectious Diseases ? Hospital Epidemiology: Nosocomial Infections (cont.) ? Factors Influencing Nosocomial Infections [INSERT FIGURE 14.20] Epidemiology of Infectious Diseases ? Hospital Epidemiology: Nosocomial Infections (cont.) ? Control of Nosocomial Infections ? Involves precautions designed to reduce the factors that result in disease ? Hand washing is the most effective way to reduce nosocomial infections ? NOT ethanol ?sanitizing? solutions! FUN ACTIVITY QUESTIONS: Last Name, First Name Last Name, First Name Last Name, First Name Last Name, First Name Date 1. Name an endemic disease. What makes this endemic? 2. What?s the difference between a flu epidemic and flu pandemic? 3. Using the flu (disease caused by the influenza virus) as an example: describe 1 symptom and 1 sign of the flu Christopher Gulvik PowerPoint Presentation Chapter 14 Material
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