Microbiology

Editor's Notes

• #2 Microbiology is the study of microorganisms and their role in the environment
• #3 Pathogen: microorganism that can cause disease Opportunist: usually harmless but may become a pathogen in certain circumstances Spores: Cell produced by a FUNGI for reproduction, may remain dormant yet viable for months. Cooking destroys spores, but pathogenic spores are usually inhaled rather than ingested A resistant cell (dormant, inactive state) of a BACTERIA to withstand extreme heat or cold or dehydration, may remain viable for decades. Can survive an hour of boiling! But can be destroyed under pressure. Any airborne particle that triggers an allergic reaction A stage in the life cycle of some PROTOZOA that contains infective sporozoites
• #5 Natural habitats Vital role of decomposing dead organic material and recycling nutrients Strep throat Pneumonia Meningitis
• #6 natural habitats- human body Influenza Common cold Chickenpox
• #9 Soil is their natural habitat Consumes dead organic matter or smaller living things
• #11 First name listed is like family name, 2nd name more specific Like saying Smith Mary & Smith John
• #12 Flora: microorganisms living in or on us Resident flora: live on or in nearly everyone almost all of the time Skin, colon, small intestines When in “normal location” they do not cause harm, and may be beneficial But resident flora may cause harm if introduced to another site, i.e. E. Coli Resident flora may be diminished by the use of antibiotics Yeasts or other bacteria may overgrow, especially on mucous membranes Resident flora are important to us because they produce VITAMINS, also because they may inhibit growth of pathogens (competition). So what problems might we have if we don’t have enough normal flora? What about newborns/infants? Transient flora: Found periodically on the body May cause harm when the host’s resistance is lowered
• #13 virulence: ability of the pathogen to cause disease (how strong it is). Ie. Measles, 90% infectivity rate (90% of those exposed will develop measles) vs. common cold (may not develop illness unless fatigue, stress, malnutrition, etc) Resistance: total of the body/host’s defenses against pathogens (skin, cilia, lymphocytes, macrophages)
• #15 Clinical infection: infection with symptoms Symptoms: observable or measurable changes that indicate illness Subclinical infections: infection with no symptoms (gonorrhea) Reservoirs: someone with a subclinical infection can be a reservoir or source, and pass the infection to someone else, in whom it may become a clinical infection Incubation period: period of time before symptoms appear. See page 502 table 22-2. **can be contagious during this period! Prodromal period: follows the incubation period. Vague, non specific symptoms may appear, such as muscle aches, lethargy, fatigue. Invasion period: specific symptoms of the illness appear Acme: worst stage of the disease Self limiting: diseases that last a certain period of time and are usually followed by recovery (cold, chickenpox, mumps)
• #16 Terminology may refer to the location of the pathogens in the body, to the general nature of the disease, or to how or where the pathogen was acquired Localized: confined to one area of the body Systemic: pathogen is spread throughout body via blood or lymph Bacteremia: used interchangeablely with Septicemia. Bacteremia means bacteria are present in the blood Septicemia: the bacteria present in the blood are multiplying rapidly. Septicemia is always serious, because it means the immune defenses have been overwhelmed and are unable to stop the spread of infection. Acute: begins abruptly, is severe Chronic: progresses slowly, may last a long time Secondary infection: made possible by a primary infection that has lowered the host’s resistance (influenza in an elderly person may be followed by bacterial pneumonia), not by fatigue or malnourishment Nosocomial infections: infections acquired in hospitals or other institutions such as nursing homes. Prevent by handwashing, proper disposal of urine, feces, blood, sharps Endogenous: infection caused by the patient’s own normal flora that has been inadvertently introduced into an abnormal body site. E. coli
• #17 Epidemiology: study of the patterns and spread of disease within a population Epidemic: outbreak of a disease Endemic: disease that is present in a population, with an expected or usual number of cases in a given time. Expect a certain number of cases; like annual flu. But if the number of cases increases significantly, it is then called an epidemic Pandemic: epidemic that has spread through several countries; ie bubonic plague
• #18 Unbroken skin is an excellent barrier to pathogens, but even microscopic breaks are portals of entry. In the spread of diseases, a pathogen travels from one person’s portal of exit to another person’s portal of entry. Diseases for which the pathogen may be directly or indirectly transmitted from host to host are called communicable. Indirect transmission includes food, water, vectors, or fomites. Picture pg. 503 Portal of entry is the way the pathogen enters a host, portal of exit is the way the pathogen leaves the body Many hospital procedures provide portal of entry
• #19 Carrier – person that is a reservoir for a disease Zoonoses- animal diseases that people acquire in certain circumstances Rocky Mtn spotted fever, lyme disease, rabies, plague Carrier may be someone who has recovered from the disease but continues to shed the pathogen
• #20 Diseases for which the pathogen may be directly or indirectly transmitted from host to host are called communicable. Indirect transmission includes food, water, vectors, or fomites. Fomites: inanimate objects that carry the pathogen. Influenza and cold viruses can survive outside their hosts for a time, so that toys, door knobs, etc. can become a vehicle of transmission NON COMMUNICABLE: tetanus
• #21 Communicable does not automatically mean contagious; HIV is communicable but not contagious since not spread by respiratory or cutaneous
• #22 Chemicals have no effect on spores Antiseptic: chemical that destroys bacteria or inhibits their growth on a living being Disinfectant: chemical used on inanimate objects Alcohol can be used for both. Bactericides: kill bacteria. Some may also kill viruses (such as bleach) Bacteriostatic chemicals: inhibit their reproduction & slow their growth but don’t kill. Sterilization: destroys all living organisms Autoclave: steam under pressure, kills everything including spores Ionizing radiation: used for materials that can’t tolerate autoclave or foods
• #23 pasteurized: heated to 145 F (boiling) for 30 minutes, kills pathogens (but not all bacteria) Chlorine: kills virtually all bacteria
• #26 Simple unicellular organisms Microscopic Watery cytoplasm, single chromosome (made of DNA) surrounded by a cell membrane, and a cell wall (often rigid & strong) classify by shape: coccus, bacillus, spirillum Classify by arrangement: staphylo, strepto, diplo Know the shapes!
• #27 Binary fission: bacteria reproduce by the process of binary fission, in which the chromosome duplicates itself and the original cell divides into two identical cells. Aerobic: can reproduce ONLY in the presence of oxygen Anaerobic: can reproduce ONLY in the ABSENCE of oxygen Facultatively anaerobic: can reproduce with or without oxygen Gram stain: lab procedure; “positive” stain purple/blue, “negative” stains pink/red. Helps to identify a pathogen. STAINS THE CELL WALL! Culture & sensitivity: helps to choose an appropriate antibiotic Resistance: bacteria are able to produce an enzyme that destroys the antibiotic, rendering it useless
• #28 Positive: purple or blue Negative: red or pink
• #29 CAPSULE: some bacilli & cocci have capsules that enclose the entire cell and inhibit the host from phagocytosis, gives them time to reproduce SPORES: dormant or inactive stage, can survive in adverse conditions, such as heat (boiling), freezing. TOXINS: chemicals harmful to the host produced by the bacteria, similar to our digestive enzymes. Some may literally digest host tissues NEUROTOXINS: toxins that specifically disrupt the functioning of nerve cells ENDOTOXINS: chemicals that make up the walls of gram negative bacteria, cause fever and circulatory shock Bacterial shapes and Gram reaction are determined by their cell walls. Capsules inhibit phagocytosis by WBCs. Flagella provide motility. Spores are a dormant form that can survive environmental extremes.
• #30 Chemicals used to treat bacterial infections BROAD SPECTRUM: affects many different kinds of bacteria NARROW SPECTRUM: affects just a few kinds of bacteria ACTION OF ANTIBIOTICS: disrupt or inhibit the chemical reactions. Penicillin blocks the formation of cell walls. Others inhibit DNA synthesis. Our own cells carry out similar activities, so our own cells can be damaged by antibiotics; liver/kidney damage
• #31 Viruses are not cells; a virus has DNA or RNA surrounded by a protein shell of characteristic shape. Many viruses are host specific. Viruses must be within a host cell to reproduce; they use the cell’s genetic and protein synthesis machinery to make new viruses. OBLIGATORY INTRACELLULAR PARASITES! Page 511 The protein shell has a shape that is characteristic for each virus. Some viruses may cross the placenta Some viruses may cause an initial infection then become dormant for years until reactivated when the host’s resistance is lowered. Some viruses are known to cause cells to form tumors.
• #34 Many challenges: Viruses are active only within cells, so the medication must be able to enter the cells Viruses are simple so not many options of what to disrupt Meds used to kill a virus may kill the host cell too Many viruses mutate frequently AZT: first med effective against HIV RIBAVIRIN: treats RSV in children
• #35 Pg 513 Spores can be inhaled, AIDS patients very susceptible
• #36 SAPHROPHYTES: live on dead organic matter and decompose it MYCOSES: infections caused by fungi CANDIDA ALBICANS: small amount normal on skin, mouth etc. but too much can cause disease.
• #37 Amphotericin b: effective for systemic mycoses but can cause serious side effects Ketoconazole, Fluconazole, Griseofulvin = newer meds to tx fungal infections and less toxic
• #38 Unicellular animals, single cells adapted to life in freshwater (including soil) and saltwater. May acquire by ingesting contaminated water or food.
• #40 Meds used to treat intestinal protozoa
• #41 Worms are simple multicellular animals.