Sterilization and Disinfection

• Sterilization removes all microbial life.
• Commercial sterilization kills C. botulinum endospores from canned goods.
• Disinfection destroys harmful microorganisms, killing 99.9% of bacteria and viruses, but endospores survive.
• Antisepsis destroys harmful microorganisms from living tissue and is safe for skin, as with soap and mouthwash.
• Degerming is the mechanical removal of microbes from a limited area, such as cleaning a spill with bleach.
• Sanitization lowers microbial counts on eating utensils to a safe level.
• Sepsis is bacterial contamination, often used to describe conditions in animals and people where bacteria spreads throughout the body.
• Asepsis is the absence of significant contamination, such as in aseptic inoculation in the lab or during aseptic surgery.
• Biocides, also known as germicides, kill microbes but not necessarily endospores.
• Examples of biocides include bactericides, fungicides, algicides, and viricides.
• Bacteriostatic and fungistatic methods inhibit microbial and fungal growth.
• D-value, or death value, is the time it takes for the number of cells to decrease ten-fold.
• D-value can be calculated similarly to generation time using a growth curve.

Biosafety Levels

• BSL-4 microbes are dangerous and exotic, with a high risk of aerosol-transmitted infections that are frequently fatal without treatment or vaccines; Ebola and Marburg viruses are examples.
• BSL-3 microbes are indigenous or exotic and can cause serious or potentially lethal diseases through respiratory transmission; Mycobacterium tuberculosis is an example.
• BSL-2 microbes are typically indigenous and associated with diseases of varying severity; they pose a moderate risk to workers and the environment; Staphylococcus aureus is an example.
• BSL-1 microbes are not known to cause disease in healthy hosts and pose minimal risk to workers and the environment; nonpathogenic strains of Escherichia coli are examples.
• Biosafety levels are determined by agent infectivity, ease of transmission, potential disease severity, and the type of work being done with the agent.

Methods Using Heat

• Dry heat kills by oxidation, such as flaming a loop.
• Incineration burns trash.
• Hot-air sterilizers generate high temperatures, generally via electrical means.
• Moist heat denatures enzymes and proteins.
• Autoclaves apply steam under pressure, reaching 120-130°C at 15 psi for 15 minutes, killing all organisms and endospores.
• Pasteurization reduces the number of organisms in liquids like juices, milk, beers, and wines.
• High-temperature short-time (HTST) pasteurization uses 72°C for 15 seconds.
• Ultra-high temperature (UHT) pasteurization uses 140°C for 4 seconds.

Filtration

• Filtration involves passing liquids and air through a screen-like material.
• Its application is for heat-sensitive materials.
• Viruses can pass through filters.
• Filtration is only be used for liquids.
• High-efficiency particulate air (HEPA) filters remove microbes larger than 0.3 μm.

Phenolic compounds and halogens

• Phenol disrupts plasma membranes and denatures enzymes, usage is rarely used except as a standard of comparison.
• Phenolics disrupt plasma membranes and denature enzymes, used on environmental surfaces, instruments, skin surfaces, and mucous membranes.
• Bisphenols probably disrupt plasma membranes, used in disinfectant hand soaps and skin lotions.
• Triclosan (a bisphenol) is widely used but may lead to bacterial resistance.
• Halogens, such as iodine, inhibit protein function and are strong oxidizing agents; chlorine forms hypochlorous acid, altering cellular components.
• Iodine is an effective antiseptic available as a tincture and an iodophor.
• Chlorine gas disinfects water; chlorine compounds disinfect dairy equipment, eating utensils, and glassware.
• Iodine works by oxidizing the cellular components.

Heavy Metals

• Heavy metals kill microbes by binding to proteins, inhibiting enzymatic activity.
• May bioaccumulate in human or animal cells.
• Excessive concentrations are toxic.
• Mercury can cause neurological damage.
• Silver can result in argyria.
• Metals can interfere with metabolism.

Factors Affecting Antimicrobial Agent Activity

• Larger populations of microbes take longer to kill.
• Microorganisms' sensitivity varies.
• Higher concentrations kill faster with antimicrobial agents.
• Longer exposure times result in more organisms killed.
• Higher temperatures generally increase killing.
• Local environment factors like pH, viscosity, and organic matter concentration can impact effectiveness.
• Biofilms are physiologically altered and less susceptible to many antimicrobial agents.

Methods to Test Effectiveness

• Filter paper disks soaked in a chemical are placed on a spread plate.
• After incubation, the zone of inhibition around the disks is measured.
• Surfactants are major ingredients in soaps and detergents; they are surface-active agents that lower surface tension of water.
• Long-chain fatty acids have polar and nonpolar regions, enabling them to interact with polar and nonpolar regions in other molecules.

Antimicrobial Drugs

• Chemotherapy involves using chemicals to treat a disease.
• Selective toxicity is the ability to selectively find and destroy pathogens without harming the host.
• Antibiotics are substances produced by a microbe that inhibit another microbe.
• Antimicrobial drugs are synthetic substances that interfere with microbial growth.
• Ehrlich and Hata discovered Salvarsan (arsenic-containing compound).
• Fleming discovered penicillin.
• Klarer, Mietzch, and Domagk discovered Prontosil (red dye) used for strep and staphylococcal infections.
• Domagk won a Nobel Prize for work on Prontosil and sulfanilamide (first synthetic antimicrobial).
• Dorothy Hodgkin analyzed the structure of natural products using crystallography and X-rays.
• Natural antimicrobial drugs are compounds isolated from organisms (mold, fungi, bacteria).
• Semisynthetic antimicrobial drugs are chemically modified derivatives of a natural antibiotic, increasing range, stability, and/or decreasing toxicity.
• Synthetic antimicrobial drugs are developed from chemicals not found in nature.
• Narrow-spectrum drugs affect a narrow range of microbial types.
• Broad-spectrum drugs affect a broad range of gram-positive or gram-negative bacteria and treat polymicrobic infections.
• Dosage is the amount of medication given over time; it ensures therapeutic drug levels at the infection site without causing significant side effects.
• Oral administration is convenient, some drugs are not easily absorbed into the bloodstream.
• The parenteral route (IV or IM injection) results in a short time to reach high concentration in plasma and is typically performed in healthcare settings.
• Half-life is the rate at which 50% of a drug is eliminated from the plasma in the number of doses/day.
• Short half-life drugs require frequent dosages.
• Half-life depends on metabolism and excretion function.
• Deficient metabolic activity (renal failure) can lengthen the half-life and duration of adverse effects of a drug.
• Selective toxicity kills or inhibits microbial targets while causing minimal harm to the host.
• Toxicity refers to the side effects caused by the drug, such as loss of balance, rapid eye movement, and vomiting.
• Anaphylaxis and idiosyncratic reactions can occur with allergic reactions.
• Antibiotics can disrupt the gut, skin, or lung microbiome, killing beneficial bacteria and leading to infection.
• Synergism is when two antibacterial drugs are administered together to improve efficacy.
• Antagonism can occur between two antimicrobials or between antimicrobials and non-antimicrobials, causing loss of drug activity, decreased therapeutic levels, and increased potential for toxicity.
• Cell wall synthesis inhibition involves the B-lactam ring preventing peptidoglycan synthesis.
• Natural penicillins, semisynthetic penicillins, ampicillin, amoxicillin, and methicillin prevent peptidoglycan synthesis.
• Protein synthesis inhibition targets different steps in bacterial translation by changing shape of 30S portion causing code on mRNA to be read incorrectly, binds to 50S portion and inhibits formation of peptide bond, interfere with attachment of tRNA-ribosome complex.
• Chloramphenicol inhibits peptide bond formation.
• Erythromycin interferes with tRNA attachment to ribosome.
• Streptomycin and tetracyclines inhibit protein synthesis.
• Membrane function interference occurs via polypeptide antibiotics changing membrane permeability, which lacks selective toxicity.
• Daptomycin is used for skin infections and attacks bacterial cell membranes.
• Polymyxin B is a topical, bactericidal antibiotic effective against gram-negative bacteria.
• Nucleic acid synthesis inhibition interferes with DNA replication and transcription by blocking DNA replication (inhibiting DNA polymerase and helicase) and blocking transcription (inhibiting RNA polymerase).
• Metabolic pathways are inhibited by antimetabolites which compete with normal substrates for an enzyme.
• Sulfanilamide competes with para-aminobenzoic acid (PABA) to stop folic acid synthesis.
• Antifungal drugs have limited effectiveness because fungal cells are similar to human cells, making them more toxic.
• Topical administration is easier to treat superficial mycoses than systemic infections; combinations of drugs may be used.
• Several drugs target ergosterol in the fungal plasma membrane.
• Antiprotozoan drugs include quinine, chloroquine, and artemisinin, which kill Plasmodium (malaria).
• Metronidazole (Flagyl) treats Trichomonas, giardiasis, and amebic dysentery; it also interferes with anaerobic bacteria.
• Antiviral drugs exhibit slow development because of the difficulty specifically targeting viral replication.
• Viruses mutate easily due to rapid replication, increasing their resistance to drugs or vaccines.
• Current antiviral drugs inhibit virus-specific enzymes related to nucleic acid biosynthesis.
• Antimicrobial resistance occurs when microbes develop the ability to defeat drugs designed kill them.
• This can occur with bacterial, fungal, viral, protozoan, species etc.
• Mechanisms of resistance include efflux pumps, blocked penetration, inactivation of enzymes, and target modification.
• Microbes are constantly evolving.
• Widespread antibiotic use has provided a selective pressure, this promotes further evolution
• The causes of the selective pressure are overuse and misuse of antimicrobials, inappropriate use, sub-therapeutic dosing, and patient noncompliance.
• Drug modification or inactivation occurs when many bacteria make B-lactamase, an enzyme that destroys penicillin and penicillin analogues.
• Prevention of cellular uptake or efflux inhibits antimicrobial drug accumulation, preventing it from reaching its target, or by pumping the antibiotic out of the cell using transport proteins/multidrug resistance (MDR) exporter.
• This confers resistance to several classes of antibiotics at once.
• Target modification occurs when antimicrobial drugs have specific targets and structural changes to those targets, can prevent drug binding, making the drug ineffective.
• Spontaneous mutations that change the target of antibiotics can lead may develop resistance to drugs.
• Genetic changes impacting the active site of penicillin-bonding proteins (PBPs) can inhibit the binding of B-lactam drugs and provide resistance to multiple drug within this class.
• Tests that are used to describe tests to determine microbe susceptibility to an antibacterial drug are describe tests used to determine microbe susceptibility to an antibacterial drug.
• Origin and transmission of drug resistance come from
• Immunity genes exists in nature to protect antibiotic producing microbes from their own antibiotics
• Horizontal gene transfer is transfered of immunity genes from antibiotic producers to non-producing microbes
• Overcoming drug resistance occurs by
• Give drug in appropriate concentrations
• Give two or more drugs at the same time (synergy: two drugs enhance each other's function)
• Use drugs only when necessary
• Possible future solutions include the use of bacteriophages to treat bacterial disease.
• The Kirby-Bauer disk-diffusion test is performed by placing paper disks with a chemotherapeutic agent on agar containing the test organism.
• After incubation, the zone of inhibition around the disk determines the sensitivity of the organism to the antibiotic.
• Dilution tests are used to determine the MIC and minimal bactericidal concentration (MBC) of an antimicrobial drug.
• The test organism is placed into the wells of a tray containing dilutions of a drug, and growth is evaluated.
• Premature termination of antibiotic treatment leads to bacteria multiplying with high resistance when antibiotics no longer being taken.
• These can also spread to other hosts, causing more drug-resistant infections.
• The E Test is a gradient diffusion method that determines antibiotic sensitivity and estimates minimal inhibitory concentration (MIC).

Microbial Pathogenesis

• Disease is any condition in which the normal structure or functions of the body are damaged or impaired, whether caused by infection, genetics, noninfectious environmental causes, or inappropriate immune response.
• Infection is the successful colonization of a host by a microorganism (pathogen).
• Symptoms are subjective, felt or experienced by a patient, and cannot be clinically confirmed or objectively measured (nausea, loss of appetite, pain, etc.).
• Signs are objective and measurable within ranges of normality such temp, heart rate, etc.
• Pathogenicity is the potential ability to cause disease (qualitative).
• Virulence is the disease producing power of an organism or the degree of pathogenicity when compared within a group.
• Infectious dose (ID50) is the number of pathogen cells or virions needed to cause active infection in 50% of inoculated animals.
• Lethal dose (LD50) is the number of pathogenic cells, virions, or amount of toxin required to kill 50% of infected animals.
• The principal portals of entry are skin, inhalation, and ingestion (least to most endospores required for infection).
• Communicable diseases are contagious and spread from person to person, such as measles.
• Non-communicable diseases are not spread from person to person, exemplified by tetanus.
• latrogenic diseases are contracted as a result of medical procedures, such as wounds.
• Nosocomial, MRSA, diseases are acquired in hospital.
• Zoonotic diseases are transmitted from animals to humans (rabies, yellow fever, flu).
• Incubation period: low number of pathogens
• Prodromal period: increase in number of pathogens, during which an individual starts to feel symptoms
• Period of illness: greater increase in pathogens - longer period of time depending on the pathogen
• Period of decline: pathogens decline in number, while signs and symptoms decrease
• Period of convalescence: pathogens are low in number, a patient often feels tired from fighting pathogens
• Acute diseases have a short time course (hours, days, weeks) and involve a rapid onset.
• Chronic diseases have longer time spans (months, years, lifetime).
• Latent diseases occur when the pathogen goes dormant for extended periods with no active replication (herpes, chickenpox).
• Summarize the stages of pathogenesis
• Exposure: mucosal surfaces are most important entry for microbes, pathogens are suited for a specific portal of entry determined by organism's environmental adaptations and by the enzymes and toxins they secrete
• Adhesion: capability of pathogenic microbes to attach to the cells of the body using adhesion factors (fimbriae, capsules)
• Invasion: dissemination of a pathogen throughout local tissues or the body, may produce exoenzymes (extracellular enzymes, enable pathogens to invade host cells and deeper tissues) or toxins which serve as virulence factors, allow them to colonize and damage host tissues as they spread deeper into the body
• Infection: successful multiplication of the pathogen
• Local: confined to small area of body, typically near portal of entry
• Focal: localized pathogen or the toxin it produces, can spread to secondary location
• Systemic: infection becomes disseminated throughout the body
• Primary pathogens cause disease regardless of the host's resident microbiota or immune system.
• Opportunistic pathogens cause disease in situations that compromise the host's defenses, such as protective barriers, immune system, or normal microbiota.
• Transmission happens as a result of pathogens being possible portals of exit
• Portals of exit include the respiratory tract (coughing and sneezing), the gastrointestinal tract (feces and saliva), the genitourinary tract (urine, secretions from the penis or vagina), skin, and blood (arthropods that bite, needles or syringes).
• Production of toxins is a virulence factor that contributes to signs and symptoms of disease.
• Poisons produced by Toxins, microorganisms, cause fever, cardiovascular problems, diarrhea, and shock
• Toxemia is a presence of toxin in the host's blood
• Intoxications: presence of toxin without microbial growth
• Exotoxins are produced inside pathogenic bacteria (most commonly gram +), secreted into surrounding medium during the log phase
• Endotoxins: lipid portions of lipopolysaccharides (LPS) that are part of the outer membrane of the cell wall of gram – bacteria (lipid A), liberated when bacteria die and the cell wall lyses
• Lipid A
• Epidemiology: The study of where and when diseases occur and how they are transmitted in populations -epidemiology: study having to, determine etiology of a disease (the study of the causes of disease), identify other important factors concerning the spread of disease, develop methods for controlling a disease, assemble data and graphs to outline incidence of disease
• The World Health Organization oversees public health at a global level.
• The Centers for Disease Control and Prevention (CDC) oversees public health at a national level.
• Notifiable diseases are those physicians are required to report; they are considered of public health importance.
• Mortality refers to the deaths from notifiable diseases.
• Morbidity is the incidence of a specific notifiable disease.
• Incidence is the number of new cases of a disease that develop in a specific population over a defined period; measures the risk of developing a disease.
• Prevalence is the proportion of a population that has a disease at a specific point in time; measures the burden/impact of a disease.
• Sporadic diseases are uncommon, occur occasionally, and affect only a few persons (whooping cough, diphtheria).
• Endemic diseases are constantly present in a percentage of the population (malaria, sickle cell anemia).
• Epidemic diseases are acquired by many people in a given area, damaging living organisms within a short time (smallpox).
• Pandemic diseases affect a large geographical area, often globally.
• Observational epidemiological studies are gathered from study participants through measurements or answers to questions in interviews.
• These studies are only able to measure associations between disease occurrence and possible causative agents.
• Observational studies are descriptive, analytical, retrospective, prospective, case-control, and cross section study.
• Experimental studies use laboratory or clinical studies with investigator manipulated subjects, to the connections between diseases and potential causatives or to assess treatments
• Everything related to epidemiology concerns the community (vaccination numbers, immunocompromised concerns, boosters).
• Connects a disease to a specific pathogen, involves
• Controlled experiments needed to eliminate other causitive agents
• Pathogens are difficult to detect when there is no immediate clue what is causing the outbreak, and signs and symptoms are non specific
• Disease reservoirs are continual sources of infection.
• Human reservoirs consist of passive carriers, who may have unapparent infections or latent diseases, and active carriers, who are infected individuals, who can transmit disease to others.
• Animal reservoirs: Zoonoses are diseases transmitted from animals to humans
• Nonliving reservoirs: Soil and water
• Diseases can be transmitted by a number of methods
• Direct contact: requires close association between the infected and a susceptible host
• Indirect contact: spreads to a host by a nonliving object called a fomite
• Droplet transmission: transmission via airborne droplets less than 1 meter
• Vehicle transmission transmission by an inanimate reservoir, such as
• Waterborne
• Foodborne
• Airborne
• Mechanical transmission, a vector Arthropod carries pathogen on its feet
• Biological transmission: pathogen reproduces in the vector; transmitted via bites or feces
• Nosocomial infections are acquired while receiving treatment in a healthcare facility, affecting 1 in 25 hospital patients, 2 million per year infected, 20,000 deaths
• A compromised host has a resistance to infection impaired by disease, therapy, or burns.
• what factors contribute to emerging and re-emerging diseases include?

Innate Defenses

• Immunity is the ability to fight infection or toxins
• Susceptibility is the lack of resistance to a disease
• Innate Defenses

Physical Barriers

• Skin

  • Epidermis is the outer portion made of tightly packed epithelial cells, containing keratin, a protective protein
  • Shedding and dryness of skin inhibits microbial growth
  • Cell junctions keep cells together avoiding breakdown by microbes (tight junctions, desmosomes, gap junctions)

• Mucous membrane

  • Epithelial layer that lines the respiratory, gastrointestinal, and genitourinary tracts
  • Mucus: viscous glycoproteins that trap microbes and prevent tracts from drying out
  • Lacrimal apparatus: drains tears; washes eye
  • Bacteriophages are abundant in mucus and protect us against bacteria
  • Ciliary escalator transports microbes trapped in mucus away from the lungs
  • Earwax prevents microbes from entering the ear
  • Urine cleans the urethra via flow
  • Vaginal secretions move microorganisms out of the vaginal tract

• Mechanical defenses

• mechanical defenses keep microbes out of the body or physically remove pathogens from the body by

  • Mucus production
  • Shedding of skin cells
  • Peristalsis: feces excretion, diarrhea
  • Vomiting

• Microbiome:

  • Begins with birth
  • Microbial communities are different in different parts of our bodies

• Resident microbiota can serve as an important first-line defense against invading pathogens

  • Resident Microbiota - compete w/ pathogens for cellular binding sites + nutrients
  • Resident Microbiota - can compete w opportunistic pathogens (candida)
  • Fecal transplant

• Chemical defenses provide protection against infection or disease

  • Low pH (1.2-3.0) of gastric juice destroys most bacteria and toxins
  • Sebum - protective + lowers skin pH (3-5)
  • Low pH (3-5) vaginal secretions inhibit microbes
  • Earwax - fatty acids that lower pH
  • Destroy Bacterial cell walls- Lysozyme and lactoferrin (perspiration, tears, saliva, mucus, and urine)

• The major anatomical features of the lymphatic system include

• Lymph, lymphatic vessels, lymphoid tissue, and red bone marrow

• Contains lymphocytes and phagocytic cells

• Lymph carries microbes to lymph nodes where lymphocytes and macrophages destroy the pathogen

• The lymphatic system lacks normal microbiota.

• A special class of broad-spectrum antimicrobial mediators are called antimicrobial peptides or (AMP)

• Antimicrobial peptides can interfere with pathogens, which are nonspecific.

• Some antimicrobial peptides are produced routinely by the body, whereas others are primarily produced (or produced in greater quantities) in response to the presence of an invading pathogen

• Complement system contains group of > 30 proteins circulating in serum that are activated in a cascade: 1 complement protein triggers the next ( complement activation )

• Proteins produced by liver and assist the immune system in destroying microbes

• Genes Only Expressed When Necessary

  • Classical Pathway- microbe covered w/ antibodies
  • Alternative Pathway- triggered first by microbe - triggers production of complement, trigger production of specific factors, cascade of protein induces inflammation, cytolysis, opsonization

• Outcomes of Complement Activation

  • Inflammation, cytolysis, opsonization
  • Protein created -> Membrane Attack Complex (MAC)
  • Burst occurs extracellular fluid flows in through transmembrane channel formed by membrane attack complex

• Coating microbes with C3b promotes attachment of a phagocyte to a microbe

• Blood vessels become more permeable chemotactic agents attract phagocytes to the area.

• Soluble proteins that act as communication signals between different cells are called cytokines such as cell proliferation, cell differentiation, inhibition of cell division, apoptosis, and chemotaxis

• Autocrine: same cell secretes and receives cytokine signal

• Paracrine: cytokine signal secreted to nearby cell

• Endocrine: cytokine signal secreted to circulatory system; travels to distant cells

• Classes of Cytokines:

• Interleukins -Chemokines

• Interferons (IFNs): Cytokines (proteins) produced by cells - have antiviral activity

  • Alerts cells to viral infection, induce antiviral defenses in infection + nearby uninfected cells
  • Induce apoptosis of virus infected cells

• Activate + Stimulate Immune cells to attack Virus Infected cells

• Ifn- alpha and Beta Produced by Cells - Cause neighbor cells to produce antiviral proteins that inhibits viral replication IFNy: Causes neutrophils and macrophages to kill bacteria. Host Specific Not Virus Specific

• Signs of inflammation include redness, swelling, pain, and heat

• Destroys harmful agent or limits its effects on the body

• Repairs replaces tissue damaged by the harmful Agent

• Cellular + Molecular Mediators of Inflammation

  • Metabolism
  • Thermogenesis
  • Function of Nerv sys

• Mediators include histamine, serotonin, bradykinin, thromboxanes, leukotrienes, prostaglandins

• acute-phase proteins cause vasodilation, increased blood vessel premeability

• Histamine - Stimulate vessels to open further, blood plasma + platelets released into area

• Kinins -Bradykinin - causes edema ( promote extravasation ), stim mast cells to degranuulate + release histamine

• Prostaglandin- promotes histamine release, contributes to fever Leukotrienes- proinflam mediators produced by leukocytes Cytokines: Small Protients: cell signaling Some pathogens resist host defense – remain in the body – stimulates inflam response → body "wall off" – creates granuloma

• Inflam that lasts a long time - ( fibrotic lesion + bacterium) examples:

  • Asthma
  • Crohn's Disease Positive outcomes of fever can increase rate of chem reaction, enhance phagocytosis, and interfere with viral interferon

Blood

• Cells and cell fragments suspended in plasma
  • Erythrocytes: red blood cells
  • Leukocytes: white blood cells
  • Platelets
• Made on Bones – Stem cells via "hematopoiesis" on Bone Marrow
• Natural killer cells: use nonspecific mechanisms to recognize and destroy cells that are abnormal in some way.
• cancer cells and those infected with viruses.
• natural killer cells recognize MHC I on a healthy cell Phagocytosis- Refers Capacity of Some Cells - Seek, "injest" + Kill Pathogens
• Phagocytes squeeze between endothelial cells of blood vessal is called diapedesis .
• Transendothelial Migration: Sticking of phagozytes blood vessel In Response To Cytokines At Site Of inflamatin
• the processes destroy & degrade are from Enzymes
  • Bacteria can reprod inside of lysosome + kill cell w/ release of toxins + other lethal components
• Pattern recognition receptors (PRR) are made of protein, generate different receptors that recognize different parts of the pathogen