UNE BIOL 1020 Module 9

Describe how human behavior can contribute to the emergence and reemergence of disease

complacency and public heath efforts changes in human society (hygiene and sanitation) population expansion/development mass production

Describe the mechanisms of pathogenesis of dermatophytes, Candida albicans, and the dimorphic fungi.

dermatophytes: have keratinases, enzymes that break down the keratin in superficial tissues, allowing the fungi to use this protein as a source of nutrition. C. albicans: generally infects the mucous membranes, causing thrush (an infection of the throat and mouth) or vulvovaginitis. dimorphic: when the small airborne conidia are inhaled, they lodge deep within the lungs. There, they develop into other forms, usually yeasts. The immune system generally controls the infection, so most cases are asymptomatic. If immunocompromised, deadly.

Describe four reservoirs of infectious agents in healthcare settings and .

other patients: Patients who have an infectious disease, perhaps the reason for their hospitalization, may discharge pathogens into the environment via skin cells, respiratory droplets, and other body secretions and excretions. healthcare environment healthcare workers visitors patient microbiota

Define the terms primary pathogen, opportunist, and virulence.

primary pathogen: microbes or virus that causes disease in healthy individuals opportunist: causes disease when body's innate or adaptive defenses are compromised virulence: degree of pathogenicity. Higher virulence means more likely to cause disease

Describe the role of Infection Control Committees in preventing nosocomial infections.

with the ICP (infection control practitioner), drafts and imple- ments preventive policies following the guidelines suggested by the Standard Precautions and the Transmission-Based Precautions given to patients, staffs and visitors

Compare and contrast acute, chronic, and latent infections.

-Acute infections are characterized by symptoms that develop quickly but last only a short time; an example is strep throat. -Chronic infections develop slowly and last for months or years -Latent infections are never completely eliminated; the microbe continues to exist in host tissues, often within host cells, without causing any symptoms. If there is a decrease in immunity sometime later, the latent infection may reactivate and become symptomatic.

Explain two ways in which microbial evolution can lead to emergence of disease

-ability to form strains and resistance to antimicrobial drugs

Describe mechanisms that bacteria use to avoid complement system proteins, antibodies, and destruction by phagocytes.

-hiding within a host cell: causes host cell actin to polymerize at one end of bacterial cell to form an "actin tail" that can propel themselves within cells -avoid destruction by phagocytes: 1. preventing encounters with phagocytes with C5a peptidase (degrades the complement system C5a that recruits phagocytic cells) and membrane-damaging toxics (kills phagocytes and other cells by forming pores in their membranes) 2. avoiding recognition and attachment: capsules (prevent phagocytosis by interfering with opsonization. The pathogen hijacks the body's immune response with C3b which activates the complement system). M protein (binds a complement regulatory protein that inactivates C3b that prevents it from being an effective opsonin and Fc receptors (bind to Fc region of antibodies to prevent their opsonins function 3. Surviving within the phagocytes: escape from phagosome (before it fuses with lysosome by multiplying within cytoplasm and forming pores in phagosomal membrane), preventing phagosome-lysosome fusion and surviving within phagolysosome -avoiding killing by complement system: serum resistant by binding to host's complement regulatory proteins and postponing MAC formation -avoiding recognition by antibodies: IgA protease (cleaves IgA- antibody in mucus and other secretions), antigenic variation (alter structure of surface antigen) and mimicking host molecules

Describe three protective roles of the normal microbiota.

-protecting against infections: covering binding sites that's used for attachment, consuming available nutrients, producing compounds toxic to other bacteria

Describe how viruses avoid interferon, regulate apoptosis, and avoid antibodies

-some viruses encode proteins that shut down expression of host genes. Others avoid interferon's effects by interfering with activation of the enzymes. -Some kill the host cell once it has produced virions, and others prevent the host cell from dying prematurely. -Some viruses prevent apoptosis from happening, giving the virus more time to replicate by controlling a protein called p53 . When this protein is inhibited, tumors sometimes develop. -To avoid being detected by the cell-mediated immune response, many types of viruses interfere with MHC class I molecules. - some viruses move directly from one cell to neighbors. -remain intracellular by forcing cellular neighbors to fuse, forming a large multinucleated cell called a syncytium. -The surface antigens of some viruses change rapidly, out-pacing the body's capacity to produce effective neutralizing antibodies. -Some viruses actually take advantage of antibodies, using them to help enter macrophages. Opsonized viral particles are engulfed by phagocytes, which they then infect.

Describe how viruses recognize host cells, and how they spread to other cells.

-viruses attach to target cells via specific receptors. Only cells that have the receptor can be infected, so this influences the host range and tissue specificity of a particular virus. -Virions released from a cell can either infect neighboring cells or spread to other tissues via the bloodstream or lymphatic system.

Compare and contrast the roles of the Centers for Disease Control and Prevention, state public health departments, and the World Health Organization.

Centers for Disease Control and Prevention (CDC) provides support for infectious disease laboratories in the United States and abroad and collects data on diseases that impact public health. The CDC also conducts research relating to infectious diseases and can dispatch teams worldwide to assist with identifying and controlling epidemics. state public health: oversees a network of public health lab involved in infection surveillance and control as well as other health-related activities. Individual states have the authority to mandate which diseases must be reported by physicians to the state. World Health Organization (WHO) provide worldwide guidance in the field of health, set global standards for health, cooperatively strengthen national health programs and develop and transfer appropriate health technology

Describe the mechanisms pathogens use to penetrate the skin and mucous membranes.

Direct uptake by cells: induce non-phagocytic cells to engulf them. The pathogen first attaches to a cell, then triggers the process of endocytosis. Membrane ruffling: actin molecules in host cell cytoplasm to rearrange, enclosing the bacterial cells and bringing them into intestinal cell. Exploiting antigen-sampling processes: some pathogens use the MALT material to cross the membrane. M cells of the MALT transport material from lumen of intestine to Peyer's patches and most microbes are destroyed but some have mechanism to avoid getting destroyed in Peyer's patch by getting non-phagocytic cells to engulf them

Describe movement of a pathogen from its reservoir to a host, and back to its reservoir or to another host.

First, there must be a source, or reservoir, of an infectious agent. If the reservoir is an infected host, the agent must leave that host through a portal of exit, be transmitted to a new host, and colonize the new host or enter that host through a portal of entry

Explain why epidemiologists are most concerned with the rate of disease rather than the number of cases.

For example, to have 100 people in a city of 1,000,000 develop genital herpes in a given time period is not as alarming as to have 100 people in a town of 5,000 develop the same disease over the same time period.

List Koch's postulates, and compare them to the Molecular Koch's postulates.

Koch's postulates: establishes that a microbe causes a specific infectious disease 1. The microorganism must be present in every case of the disease. 2. The microorganism must be grown in pure culture from diseased hosts. 3. The same disease must be produced when a pure culture of the microorganism is introduced into susceptible hosts. 4. The microorganism must be recovered from the experimentally infected hosts. Molecular Koch's postulates: similar to Koch's postulates, but they rely on molecular techniques to study a microbe's virulence factors. 1.The virulence factor gene or its product should be found in pathogenic strains of the microorganism. 2. Mutating the virulence gene to disrupt its function should reduce the virulence of the pathogen. 3. Reversion of the mutated virulence gene or replacement with a wild-type version should restore virulence to the strain.

Compare and contrast the mechanisms of pathogenesis of protozoa and helminths

Most pathogenic protozoa and helminths either live within the intestinal tract or enter the body's tissues via the bite of an arthropod. eukaryotic parasites attach to host cells via specific receptors. Some hide within cells, thus avoiding expo- sure to antibodies as well as certain other defenses. The extent and type of damage caused by parasites varytremendously. In some cases, the parasites compete for nutrients in the intestinal tract, contributing to malnutrition of the host. Helminths may accumulate in high enough numbers or grow long enough to block the intestines or other organs. Some parasites produce enzymes that digest host tissue, caus- ing direct damage. In other cases, damage is due to the immune response

Explain the value of maintaining a current list of notifiable diseases.

The list of diseases considered notifiable is determined through collaborative efforts of the CDC and state health departments. Typically the diseases are of relatively high incidence or pose potential danger to public health.

Explain how characteristics of a pathogen can influence the epidemiology of a disease.

Virulence- affects the type of severity of the disease -mechanisms for attaching to host surface -avoiding recognition or destruction by immune system -damaging the host The Dose- When the person is exposed to small numbers of the pathogen it is unlikely to cause infection/ disease. -the certain minimum number of cells must colonize to enter the body and produce enough damage to cause disease Incubation period- the extent of the spread if influenced by its incubation period -disease with long incubation can spread far and wide before the fist symptomatic case appears

Explain how climate can influence disease emergence.

Warm temperatures favor the reproduction and survival of some arthropods, which can serve as vectors for diseases such as malaria,

Describe the requirements for adherence and colonization.

adherence: pathogens must adhere to host cells to initiate infections but does not necessarily cause disease. Toxic production or invasion are involved for disease. Bacteria use adhesions to attach to host cells that are often on the tip of pili (fimbriae for attachment) to receptors. Adhesin-receptor is highly specific, dictating the type of cells to which bacterium can attach. colonization: microbes must multiply in order to colonize the host. To colonize a mucosal surface, some pathogens produce iron-binding molecules called siderophores and others can can use the iron bound to the host. Raid turnover of pili to shed any bound antibody, antigenic variation and IgA proteases (enzymes that cleave IgA antibodies)

Explain the role of type III secretion systems in infection

aka injectisome, is a syringe-like structure that injects proteins into eukaryotic cells. The injected pro- teins, referred to as effector proteins, induce changes such as altering the cell's cytoskeleton structure. Some effector pro- teins direct the host cell to engulf the bacterial cell

Describe how the composition of the normal microbiota can change over time

c-section vs. natural birth breast feeding encounters of microbes

Compare and contrast descriptive studies, analytical studies, and experimental studies.

descriptive studies: collecting data about time, place and individuals affected during occurrence analytical studies: designed to determine which of the potential risk factors identified by the descriptive studies are actually relevant in the spread of the disease. -case-control study starts with the disease and attempts to determine the chain of events leading to it -cross-sectional study collects data about a population at a given point in time. It does not attempt to establish the cause of a disease, but instead provides a snapshot of the population's characteristics -Cohort studies look ahead to see if previously identified risk factors actually predict a tendency to develop the disease experimental study is sometimes used to judge the cause-and-effect relationship between the risk factors and the development of disease, but most frequently it is done to assess the value of a particular intervention or treatment

three mechanisms by which the agents can be transferred to patients

direct transmission: Healthcare personnel must be extremely vigilant to avoid trans- mitting infectious disease agents, particularly from patient to patient. indirect transmission: diagnostic and therapeutic procedures can potentially transmit infectious agents to patients. indirect transmission: most hospitals are designed to minimize the airborne spread of microbes. Airflow to operating rooms is usually regulated so that it is supplied under slight pressure, preventing contaminated air in

Describe the conditions that may allow eradication of a disease.

eliminating the natural occurrence of a disease that had a 25% case-fatality rate and disfigured many who survived. programs of extensive immunization along with isolation of cases were able to eliminate the reservoir and therefore eradicate the disease.

Compare and contrast neurotoxins, enterotoxins, and cytotoxins, giving two examples of each

enterotoxins: intestinal disturbance (diarrhea and cholera) neurotoxins: damage nervous system (botulism and tetanus) cytotoxins: variety of different cell type damage by interfering with essential cellular mechs or by lysing cells (whooping cough and diphtheria)

Describe the difference between exotoxins and endotoxins.

exotoxins: proteins that have specific damaging effects in Gram -/+. Can leak into surrounding fluid and lyse bacterial cells. The pathogen must colonize a body surface/tissue to produce enough toxins to cause damage each unique. Can act locally or spread in bloodstream causing systemic effects. Because exotoxin are proteins, the immune system can produce neutralizing antibodies but not before fatal damage. Inactivated by heat endotoxins: lipopolysaccharide that makes of outer layer of Gram-. Cannot be converted to an effective toxoid for immunization like exotoxins. Heat-stable but innate immune response, systemic as well but if distributed can be deadly

Explain how characteristics of a host can influence the epidemiology of a disease.

immunity to the pathogen- previous exposure or immunization decreases incidence of disease. -herd immunity protects non-immune individuals because most potential hosts are immune general health age gender behavioral practices: breast fed genetic background

Explain how inflammation and antibodies can cause damage.

inflammation damage: inflammation can destroy tissue because phagocytic cells are recruited to the area releasing enzymes and toxic products antibodies: -when antibodies bind to antigens, the complexes can settle in the kidneys and joints, where they activate the complement system, causing destructive inflammation. -certain antibodies produced in response to an infection bind to the body's own tissues, promoting an autoimmune response.

Describe how a common-source epidemic can be distinguished from a propagated epidemic.

propagated epidemic occurs when a disease is contagious, with one person transmitting it to several others, who then transmit it to several more, and so on. In this situation, the number of ill people rises gradually, with higher peaks in the number of cases over time common-source epidemic occurs when all of the cases result from exposure to a single source of the infectious agent. Not all common-source epidemics involve a single exposure to the infectious agent. In some cases, contact is continuous over a long period of time or is intermittent. Also, some epidemics may start with a single source, but then those infected individuals transmit the disease to their contacts, leading to a propagated epidemic.