Microbial Control and Immunity Concepts Review

Sterilization

Complete destruction or removal of all forms of microbial life, including endospores.

Disinfection

Destruction of harmful microorganisms on inert surfaces.

Antiseptics

Chemicals used to destroy microorganisms on living tissue.

Sanitization

Lowering microbial counts on eating utensils and food preparation areas to safe public health levels.

Thermal death time (TDT)

The length of time for all bacteria to be killed at a given temperature.

Thermal death point (TDP)

The lowest temperature at which all microorganisms will be killed in 10 minutes.

cide

to kill.

Stasis or static

to inhibit growth but not necessarily kill.

Physical methods of control

1. Heat 2. Radiation.

Chemical methods of control

1. Alcohols 2. Phenolics 3. Halogens.

Autoclave parameters

121°C, 15 psi, 15-20 minutes; uses steam under pressure to sterilize.

Pasteurization

A method of heating liquids like milk to a specific temperature for a set time to kill pathogens.

Methods of control targeting proteins

Heat, alcohols, heavy metals.

Methods of control damaging DNA

Radiation, some chemical agents.

Methods of control targeting nucleic acids

Ionizing radiation, ethylene oxide gas.

Methods of control targeting lipid/cell membranes

detergents, alcohols, phenolics.

Antimicrobial drugs

Drugs that destroy pathogens or inhibit their growth.

Antibacterial drugs

Easier to treat because pathogen is prokaryotic and our cells are eukaryotic. The cell wall, ribosomes, and metabolic reactions are different.

Antiviral drugs

Difficult to treat because the virus is inside our cells, so our cells are killed also.

Antifungal drugs

Difficult to treat because pathogen is eukaryotic and our cells are eukaryotic.

Antiparasitic drugs

Difficult to treat because pathogen is eukaryotic and our cells are eukaryotic.

Bacterium studied by Alexander Fleming

Staphylococcus aureus.

Mold species studied by Alexander Fleming

Penicillium notatum.

Broad-spectrum drugs

Drugs that target a wide range of microbes both Gram-positive and Gram-negative. Example: tetracycline, ampicillin.

Narrow-spectrum drugs

Drugs that target a specific group either Gram-positive or Gram-negative. Example: penicillin, vancomycin.

Preferred type of spectrum

Narrow-spectrum is preferred because it targets specific pathogens and limits disruption of normal flora.

Antibiotics

Natural antimicrobial agents produced by microbes to kill or inhibit other microbes.

Factors impacting antimicrobial drug development

1. Toxicity to host 2. Microbial resistance 3. Cost and availability 4. Stability in the body.

Antimicrobial resistance

A microbe to resist the effects of a drug that once could successfully treat it.

Superbugs

Microbes that are resistant to multiple antimicrobial drugs.

Acquired resistance

Resistance that develops due to genetic change or acquisition of resistance genes.

Ways microbes evade antimicrobial drugs

1. Inactivation of the drug 2. Alteration of drug target sites 3. Efflux pumps that expel the drug.

Human behaviors contributing to antibiotic resistance

- Overprescribing antibiotics - Not finishing prescribed treatments - Using antibiotics in animal feed.

Holobiont

Host and its associated microbes considered together as a single ecological unit

Symbiosis

A close relationship between two different species living together.

Mutualism

Both organisms benefit

Commensalism

One organism benefits, the other is unaffected.

Parasitism

One organism benefits at the expense of the other

Normal microbiota

Microorganisms that reside normally on or in the body without causing disease.

Transient microbe

Microbes that are present temporarily and then disappear.

Pathogen

A microorganism that can cause disease.

Host

The organism that harbors the pathogen.

Opportunistic pathogen

Causes disease only when the host's defenses are compromised.

Infection

Colonization of the body by pathogens

Disease

An abnormal state where the body is not functioning normally.

Pathogenicity

The ability of a microbe to cause disease.

Virulence

Degree of pathogenicity or how severe the disease is.

Virulence factors

Traits used by microbes to invade and cause disease.

Portal of entry

The site through which pathogens enter the body.

Parenteral route

Pathogens enter through broken skin.

Preferred portal of entry

The specific portal a pathogen must enter to cause disease.

Lethal dose (LD50)

The dose of a toxin that kills 50% of the test population.

Infectious dose (ID50)

The number of microbes needed to cause infection in 50% of a test population.

Adherence

The ability of pathogens to attach to host cells

Biofilms

Communities of microbes that form a protective layer on surfaces.

Toxigenicity

Ability of a microorganism to produce toxins

Toxemia

Presence of toxins in the blood

Toxins

Poisonous substances produced by microbes

Exotoxins

Made of proteins and are produced by Gram-positive (and some Gram-negative) bacteria.

Toxoid

Inactivated exotoxins used in vaccines

Neurotoxin

Toxin that affects nerve cells

Enterotoxin

Toxin that affects the intestines

Cytotoxin

Toxin that kills host cells

A-B toxins

Two-part toxins: 'A' active part and 'B' binding part

Two-part toxins

A toxin consisting of an 'A' active part and a 'B' binding part.

Membrane disruption toxins

Toxins that lyse host cells by disrupting membranes.

Leukocidins

Toxins that destroy white blood cells; produced by Staphylococcus aureus.

Hemolysins

Toxins that lyse red blood cells.

Superantigen

Bacterial proteins that overactivate the immune system, causing massive inflammation.

Gamma hemolysin

No change on blood agar; no hemolysis.

Alpha hemolysin

Partial hemolysis on blood agar.

Beta hemolysin

Complete clearing around colonies on blood agar.

Endotoxins

Made of lipopolysaccharide (LPS), produced by Gram-negative bacteria.

Localized infection

Infection confined to a small area.

Systemic infection

Infection spreads throughout the body.

Latent infection

Infection remains inactive/dormant.

Acute disease

Disease develops rapidly and resolves quickly.

Chronic disease

Disease develops slowly and lasts a long time.

Signs

Objective indicators of disease (fever, rash, swelling).

Symptoms

Subjective feelings of disease (pain, fatigue, nausea).

Incubation phase

Time between infection and appearance of first symptoms.

Prodromal stage

Early, mild symptoms.

Acute phase

Disease is at its height; most severe signs and symptoms.

Convalescent period

Recovery phase, symptoms decline as the body returns to normal.

Epidemiology

Study of the distribution and determinants of health-related events in populations.

Etiological factors

The cause of a disease (the pathogen responsible).

Reservoirs

Natural habitat of a pathogen, can be humans (HIV), animals (rabies), environment (soil for Clostridium).

Source

The individual or object from which an infection is actually acquired.

Vector

Living organism that transmits pathogens.

Zoonosis

A disease transmitted from animals to humans (ex: rabies, plague).

Fomite

Inanimate object that transmits disease.

Mode of transmission

The way a pathogen moves from one host to another.

Noncommunicable

Disease that is not spread from host to host (ex: tetanus).

Communicable

Disease that spreads from one host to another (ex: influenza).

Contagious

A communicable disease that spreads easily (ex: chickenpox).

Direct contact

Person-to-person transmission (ex: touching, kissing, sexual contact).

Indirect contact

Transmission via a nonliving object (ex: fomite).

Sporadic

Disease that occurs occasionally (ex: typhoid fever).

Epidemic

Disease acquired by many people in a short time (ex: influenza outbreak).

Endemic

Disease constantly present in a population (ex: common cold).