Infection and Disease: Symbiosis & Normal Flora

Lecture 5 - Infection and Disease

• Symbiosis: "living together", doesn't specify benefit/non-benefit to organisms.

• Mutualism: both organisms benefit, exemplified by E. coli in intestines.

• Commensalism: One organism benefits, the other is unaffected

• Synergism: microbes combine to achieve something neither could alone.

• Parasitism: one organism benefits, the other is harmed, like viruses or malaria.

• Normal flora: healthy microbes in/on the body, critical for survival.

• Human body: ~30 trillion human cells, ~40 trillion microbial cells.

• Normal flora exists in large/small intestines (E. coli, Enterobacter), skin (Staphylococcus), mouth (Staph, Strep, Spirochetes), nose/upper respiratory (Staph, Strep, Corynebacteria), and genitals (Staph, Lactobacilli)

• Normal flora should NOT be in the circulatory system, internal organs, CNS, bladder, stomach or a foetus.

• Normal flora prevents pathogen establishment, E. coli produces vitamin K, intestinal bacteria aid fibre breakdown and alter gene expression

• Destruction/translocation of normal flora can lead to UTIs, yeast vaginitis, diarrhea/colitis, toxic shock, or staph infections.

• Infection: invasion of body by a pathogenic organism.

• Disease: change from good health

• Infection doesn't always equal disease.

• Disease requires infection by the causative microbe.

• Pathogenicity: ability of a parasitic microbe to infect and cause disease.

• Pathogenicity includes the disease's severity.

• Virulence: the degree of pathogenicity

• Avirulent organisms: don't cause disease

• Measles timeline (example):

  • Days 0-10: incubation from measles entrance.
  • Days 10-13: prodromal symptoms appear.
  • Days 13-16: acme stage; rash appears at hairline, face.
  • Days 16-18: decline period.
  • Days 18-21: convalescence as rash fades.

• Incubation period: time from initial contact to symptom appearance, usually 1-30 days.

• Prodromal period: the infected person begins to fight infection

• Acme period: acute illness and characteristic symptoms appear, most transferable period

• Decline period: symptoms decrease, accompanied by sweating.

• Convalescent period: recovery, but susceptible to re-infection.

• Direct transmission: involves physical contact, respiratory secretions, animal bites, or congenital transfer

• Indirect transmission: infectious agent passes via an intermediate object to another host.

• Fomite: inanimate object carrying pathogens.

• Vector: live organism acting as a vehicle.

• Mechanical transmission: vector carries unchanged microbial population.

• Biological transmission: vector increases microbial population.

• Reservoirs of infection: living (humans, animals) or nonliving (soil, water, food, fomites).

• The most important reservoir for human infections are other humans.

• Disease measurement importance: identify new diseases, their impact, allocate resources, and prevent.

• To determine disease frequency: Define population, case, information sources, and use a systematic approach (statistical analysis) .

• Mortality rate: deaths per 1000 or 100,000 people.

• Incidence: new cases in a given space and time.

  • (# of new cases/number of people at risk)

• Prevalence: total cases in a given space and time.

  • (number of old & new cases/ number of people at risk)

• Prevalence > Incidence (≥ Mortality)

• Incidence ≥ Mortality Rate unless a disease is eradicated

• Endemic: disease constant, low level in a given area.

• Sporadic: few scattered cases in an area.

• Epidemic: greater than normal cases in an area.

• Outbreak: a more contained epidemic

• Epi Curves: show case distribution over time

• Point source type outbreak: rapid increase and decrease in cases.

• Continuing Source Outbreak: constant infectious agent emission.

• Disseminated Outbreak: progressive spread from an index case.

• Intermittent outbreak: source intermittently available.

• Pandemic: worldwide epidemic.

• AIDS in Canada (2008): prevalence was 65, 000 and incidence was 0.01%

• Communicable: infectious agent spreadable from person to person

• Contagious: infectious agent spread very easily

• Acute Infection: rapid onset, climax, recovery

• Chronic infection: slow onset, longer recovery, no climax

• Primary infection: the original illness

• Secondary infection: infection in a weakened individual.

• Local infection: confined to a single area

• Systemic infection: enters blood stream and/or spreads into tissues.

• Nosocomial infections: acquired in hospital

  • 5% of infections in Canada, 2% in Norway/Finland.
  • 15,000 deaths/year; can be prevented.

• Top 3 nosocomial infections: UTI (40%), surgical sites (19%), respiratory infections (15%).

• Exogenous infections: the source is outside the patient.

• Endogenous infections: the source is inside the patient.

• Iatrogenic infections: HCW induced/caused.

• Superinfections: e.g. MRSA, VRE, C. difficile.

Factors & Events Contributing to Infections

• Microbes in hospital, immunocompromised patients, transmission btwn staff/patients.
• Control: universal precautions including handwashing.
• Establishment of infectious disease requires penetrating the host's barrier, entering tissues, moving, causing damage, and exiting
• Entry/exit portals: eyes, nose, mouth, ears, skin lesions, urethra, anus
• Factors in disease: host susceptibility, dose, and virulence
• Virus infectious dose = PFU (plaque forming units) or IU (infectious units).
• Virulence: Pathogenicity (ability to cause disease)
  • Influenced by invasiveness and toxicity
• Adhesions: On pili, cell wall, outer membrane, capsid, spikes that induce phagocytosis/endocytosis.
• Coagulase: clots plasma, forming protective walls.
• Kinases: dissolve blood clots, facilitating movement.
• Hyaluronidase: dissolves tissue glue, spreading infection (gas gangrene).
• Leukocidins: destroy WBCs
• Hemolysins: destroy RBCs
• Extracellular enzymes are used to assist in bacteria identification.
• Genes coding for pathogenic factors exists within pathogenicity islands and transferred via horizontal gene transfer.
• Two toxin groups: Exotoxins (tissue specific) and Endotoxins (generalized/systemic)
• Exotoxins: target tissue, destroy tissue/alter production.
• Endotoxins: induce clots, activate complement, cause systemic inflammation
• Characteristics of exotoxins include protein, secreted, mainly Gm +, and high potency.
• Characteristics of endotoxins include Lipid/Carbs, released when cell disintegrates, Gm - and low potency.
• Exotoxins create very specific toxic effects, and a strong immune response
• Endotoxins create non specific toxic effects, and a weak immune response
• Exotoxin examples: Botulism (muscle paralysis), Diphtheria (nerve/myocardial destruction), Tetanus (muscle spasms)
• Endotoxin examples: Dysentery, meningitis, typhoid fever, cholera (fever, diarrhea, vomiting, shock)

Lecture 6 - Control of Microorganisms

• Microbial control is for preventing diseases, preserving foods/medications, prevent contamination

• 3 types of microbial control: physical, chemical, chemotherapeutic.

• "-cide" or "-cidal" indicates killing

• "-stasis" or "-static" indicates slowing growth

• Sterilization: destroys ALL forms of life, which includes bacterial spores

• Disinfection: destroys/removes pathogens

  • Disinfectant: used on objects
  • Antiseptic: used on living tissue

• Aseptic: conditions free of contaminating microbes

• Septic: conditions with microbial contamination

• Sanitize: reduction of microbial population

• Degerm: removal of microbes from surface

• Antimicrobial effectiveness factors: Exposure time, intensity/concentration, populations, characteristics, and environmental factors.

• Rate of microbial death occurs at a constant % and follows a logarithmic pattern

• Physical microbial control methods: heat, cold, drying, filtration, radiation.

• Heat is efficient at cost-effective sterilization and disinfection

  • Measured by thermal death : Time to kill microbes at a specific point/temp, temp to kill population

• Heat kills microbes by destroying membranes, denaturing/oxidizing proteins, and dehydration.

• Moist heat: has better penetration and requires lower temperatures.

• Moist heat method examples:

  • Boiling water: It's not effective for sterilizing but very effective at sanitization
    • Most species killed in 10 min
    • Fungal spores and hep A may require 30 minutes
    • Bacterial spores require more than 2 hours
  • Pasteurization: kills certain bacteria to sanitize
  • Pressured Steam: use autoclaves at a preferred sterilization method
  • Steam enters autoclave at 15 psi above atmospheric pressure and is used to sanitize bedding, utensils, instruments, and saline solutions

• Dry heat methods:

  • Incineration (direct flame)
    • Effective sterilization used on lab utensils
    • Disposal of contaminated objects
  • Hot air baking
    • Can be used to sterilize
    • 160°C for 2 hours to kill spores
    • Used on dry powders, glassware

• Filtration is a physical removal of microbes used on heat-sensitive materials.

  • It requires a correct degree of removal that works depending on the pore size

• Atmospheric air filtration: Laminar Flow Hood (<0.5µm), Face Mask (several µm), HEPA filters – High Efficiency Particulate Air (<0.5µm)

• Radiation kills by damaging DNA

  • Classified by wavelength power. Higher frequency = greater energy.

• Ionizing/penetrating radiation has high energy wavelengths

• Non-ionizing radiation Non-penetrating and lower energy, primarily UV

• Effects are germicidal for objects and air, destroys genetic material, and has a lower penetration power. This is used in special light fixtures used in hospitals

• Ionizing radiation:

  • Example rays are gamma and x-rays
  • Its good at penetration and germicidal by destruction of genetic material
  • It is also used to sterilize food, drugs(vitamins), vaccines, plastics, and subcultures

• Irradiated foods in Canada: Potatoes, Onions, Wheat, Flour, Spices, Ground beef

• Effects include the generation of O2 free radicals and the destructions of vitamins (A, E, K)

• Four Preservation methods: Salting or sweetening, Drying, Cold, and Freeze drying.

• Salting/sweetning is bacteriostatic used as a preservative foods

• Drying is bacteriostatic used as a preservative for food/drugs. It stops metabolism when rehydrated.

• Cold slows growth to bacteriostatic levels. It freezes and requires liquid nitrogen for preservation.

• Freeze drying: uses Lyophilization for long term laboratory and astronaut food preservations

• Semmelweis advocated for hand washing chlorine, and Lister used carbolic acid phenol as father of antiseptic for physicians and after surgery.

• Antiseptics/disinfectants must kill microbes, be non-toxic, soluble, stable, not corrode, avoid organic matter combination, and be cheap/easy to obtain

• Consider temperature/pH (25 °C vs 37 °C, pH = 7 vs 5-6), microbe type (bacterial spores vs colonizing bacteria), and surface (table‐top vs wound) when employing such products.

• In Canada, Health Canada oversees health issues. The guidelines used by the TPD called Food and Drug Act and Regulations

• Disk diffusion test: determine if product is bactericidal or quantitative

• Use-dilution test: quantitative tests conducted by suppliers to determine effectiveness of chemical

• Drawbacks on both these diffusion method is its controlled test environment and not toxicity

• Phenol Coefficient (PC): measure chemicals against phenol

• Germicidal Actions: Disrption of plasma membrane, denature Proteins, and inhibit protein synthesis

  • Phenol denatures proteins, breaks cell membrane, and is effective on positive bacteria
  • Harshness on skin led to the development in less caustic derivatives.

• Halogens: Reactive elements include Chlorine and Iodine.

• Chlorine/Iodine have germicidal effects from oxidation/protein inactivation and effective to all microbes

  • Chlorine: Sodium hypochlorite (NaOCL): We use bleach in water treatment , equipment disinfection, and food processing.
  • Iodine: added to alcohol or is a iodophors detergent in pre-op to sterilize. Doses use 5 drops to sterilization in 1L H₂O.

Lecture 7 – Control of Microorganisms (part 2)

• Microbes are fought off the body by using our immune system and chemotherapy to help kill them

• Chemotherapeutic agent: any chemical (antimicrobial/antibiotic) used to treat infections in the body through a synthetic agent

  • Must provide selective toxicity: the microbe, not the host

• Antibiotics produced naturally that inhibit microbes

• Natural drugs: Aspirin from tree willow bark, Quinine - from quina tree bark, Streptokinase – from Streptococcus bacteria, Hirudin and Draculin - from leeches/bat anticoagulant, Penicillin from Penicillium, Other AB from bacteria/fungi

• Antibiotic: ‘Spectrum of Activity'(range of which it’s effective against)

• Erythromycin aGm positive narrow spectrum antibiotic

• Tetracycline a broad spectrum antibiotic

• Broad antibiotic are harmful as they kill normal microbes, leads to side effects and can leads to AB resistance

• 5 Methods of Antimicrobial Activity: Inhibit synthesis of cell wall/membrane, Nucleic acid, Essential metabolite and interfere with plasma membrane.

• Sulfonamides: the first agent isolated in 1935 that inhibit/mimics folic synthesis. They are broad and can treat UTIs

• Isoniazid: activated by catalase in the cell to inhibit the mycolic production. Used for TB leprosy.

• TB is resistant by inactivating drug effectiveness. To counter, TB down regulate catalase in cell to combat medicine.

• Quinine: chemotherapeutic antimalarial that binds to protozoa DNA to disrupt reproduction. A combination is best

• Antibiotics originate from Microbial wars

• Drugs: produced from Streptomyces bacteria> synthetic drugs> gram +ve bacillus > Penicillium

• List of molecules and drugs: Penicillin, Cephalosporin, Streptomycin, Chloramphenicol, Tetracyclin

• Penicillin acts using a beta-lactam to inhibit peptidoglycan. This leads to cell synthesis blocked from carb link.

• Derivatives from this are Sodium penicillin G, Cloxacillin

• Cephalosporin has similar actions/structure as a substitute that’s beta lactam to inhibit cell wall synthesis and derived from seawater.

  • Substitutes includes some allergenic resistance in its 3 generations.

• Streptomycin binds, toxic, and can affect GI w/ less toxic derivatives called “mycin”

• Chloramphenicol is isolated from bacteria. Has great meningitis that have protein synthesis inhibitors. New borns cannot produce and show “grey syndrome”

• Tetracycline: disrupts protein and has resistance to STD

• Can trigger child stunted, tooth discoloration but its derivates have cycline.

• 3 tests of effectiveness: The zone of resistance. Does the broth kill or not?!

• Difussion w/: E-Test aka Kirby

1. Paper absorbs AB-then inhibits effectiveness vs zone, qualitative only. Not for testing
2. Plastic strip- gradients show, minimum amount needed which does not kill. This one tested with concentration
3. Ab diluted to wells, what number does this kill- what quantity

• Superbugs are very drug resistant strains

• Can trigger quick drug removal, hardening from prevention, or targeting drugs

• Antibiotics can affect natural phenomenon by misduing it. Common issues are over prescriptions, self medications and incomplete regulators.

• 3 Major Bugs :MRSA C.Difficile VRE

• Characteristics: 33% Carry SA, 2% Canadians. Occurs 5 to 6 times in 1000 administrations in candidate direct contact and is pen. resistant. Also has gram resistance and death is often unclear due to

• Clostrifium forms spores via fecal root in Na. Causes quebec to have increase cases to combat. 90% Success Rate

• 1. Day of feces given test in pt -2 Day Blended to the injection

• VRE developed w/ fecal routes and use AB with low risk and great doses.

• Major Threat Super Bug: KPC capsule bacilli causes pneumonia that contains AB resistant issues

• To combat bugs, education of line workers,reduce medicine,create antibiotics, and combine drugs with therapy to stop the bugs!

• This can involves with phages of the microbe that's in the cell to stop division within plants and animals that kill the bacteria.