Intro to Microbes and Infectious Diseases; Bacterial Things

Microbe

• something that requires a microscope to be seen

• can’t see with the naked eye

• EX: Influenza virus (Flu), Bacteria

Classes of Microbes

• Eukaryotes (protists, Fungi)

• Bacteria

• Archaea

• Virus (not alive, needs a host cell compared to the others)

Prion

• collection of misfolded protein

• considered as a class of microbe kind of

Microbes in Human Lives: Positive Effects

• gut health

• builds immune system

• Fermentation

• Vaccines/Medication

Microbes in Human Lives: Negative Effects

• certain ones make you sick

• Food spoilage

Roles of Microbial Organisms

Health

• infectious disease/but also protection, digestion; food spoilage/but also food protection

Roles of Microbial Organisms

Biotechnology (Bioengineering)

• production of drugs, hormones, etc

Roles of Microbial Organisms

Bioremediation

• detoxification

Roles of Microbial Organisms

Environment

• energy capture (photosynthesis)

• geochemical cycling (EX: Nitrogen fixation)

Roles of Microbes in Biosphere

• bacteria that lives on plants/photosynthesis)

• can find microbes in ecosystem (inside and out of animals/plants etc…)

• microorganisms play an essential role in cycling of nutrients (nitrogen fixation, bacteria in soil helps nitrogen cycle through)

Microbes in Human Evolution

• fossil evidence of prokaryotic cells existing over 3 billion years ago

• Endosymbiosis - early prokaryotes contributed directly to the evolution of eukaryotes

• Symbiotic prokaryotic cells are the original source of chloroplasts and mitochondria (they have DNA & double membranes)

• Microbes are extremely diverse in habitat, form, and function

Types of Symbiotic Relationships

Mutualism

• both species benefit

Type of Symbiotic Relationship

Parasitism

• one species benefits and the other is harmed

Type of Symbiotic Relationship

Commensalism

• one species benefits, the other is not harmed (neutral)

History of Infectious Disease

• Florence Nightingale - founder of modern nursing, found significance of infection using a quantitative approach (EX: Mortality due to infection)

• helped lead to epidemiology (the study of disease in populations)

• historical observations indicated that disease can be transmitted from person to person

• microbes relationship to disease wasn’t established until the mid-1800s

“Germ” Theory

• Koch establishes Bacillus anthracis (bacteria) as the cause of anthrax

• Anthrax - disease found in livestock which can be transmitted to humans

Koch’s Postulates definition

• are used to determine if a particular microbe is the causative agent of disease

Koch’s Postulates: 1

• the microbe is found in all cases of the disease but is absent from healthy individuals

Koch’s Postulates: 2

• microbe is isolated from diseased host and grown in culture

Koch’s Postulates: 3

• when the microbe is introduced into a healthy, susceptible host; the same disease occurs

Koch’s Postulates: 4

• the same strain of microbe is obtained from the newly diseased host

Pathogen

• can survive in or out of a cell

• 2 classes of pathogens

Primary Pathogen

• cause of disease in an otherwise healthy host (EX: Influenza (flu))

Opportunistic Pathogen

• not typically associated with disease

• ability to cause disease depends on host resistance (typically immune function)

Virulence

• severity of disease associated with infection by pathogen

LD₅₀

• the amount of pathogen required to cause death of half the animals

Types of Growth of Pathogens

Invasion

• growth inside of host cells

Types of Growth of Pathogens

Invasiveness

• ability to spread in tissue

Types of Growth of Pathogens

Host Range

• the species that a particular pathogen can infect

General Mechanisms of Pathogenesis

Adherence

• the ability of a pathogen to stick to a host

• they must attach to their host, usually using specific receptors that determine the initial site of infection

General Mechanisms of Pathogenesis

Avoidance

• avoid defenses or rapid immune responses will eliminate them before they can replicate

General Mechanisms of Pathogenesis

Growth

• gain nutrients from host to grow

Disease Stages

Incubation

• the subject gets exposed to the pathogen; microbe gets used to new surroundings within the host

Disease stages

Prodromal

• start to see initial symptom; the person my feel a little sick or off

Disease Stages

illness

• number of microbes is higher than immune response; peak sickness

Disease Stages

Decline

• higher immune response against microbe; feeling a lot better

Disease Stages

Convalescent

• still some microbial presence and can spread the illness but may be asymptomatic

Disease Stages

Long term

• body has built immunity to microbe but can still track the microbe if it were to come back; it’ll be ready to “fight” it

Signs

• are directly measurable or observable

  Ex: Rash, Fever

Symptoms

• are difficult to pinpoint in a sense of measuring

• felt my the patient

  Ex: Headache, muscle-pain, nausea

Descriptions of Infection

Focal

• one spot; pinpoint location of infection

  Ex: boil

Descriptions of Infection

Systemic

• the infection is widespread throughout the body

Descriptions of Infection

Mixed Infection

• various microbes involved or present

Descriptions of Infection

Primary/Secondary Infection

• one infection comes first then a second infection is caused by the first one; different infections

Descriptions of Infection

Acute infection

• very rapid onset of symptoms

Descriptions of Infection

Chronic Infection

• symptoms develop slowly and resolve slowly as well

Descriptions of Infection

Nosocomial infection

• infections acquired in a hospital

Descriptions of Infection
Iatrogenic infection

• infections transmitted by a healthcare worker to a patient

Vector

• a living organism that can transmit infectious pathogens between humans, animals, plants, etc…

  Ex: a mosquito

Reservoir

• organisms that harbor a pathogen and can be transmitted indirectly and directly through contact

Transmissions

Indirect

• microbes can be transmitted indirectly by inanimate objects

• by vehicle transmission

• by insect vector

Transmission

Direct

• microbes can be transmitted by direct contact or by aerosolization (sneeze, cough)(droplets)

Transmission

Vertical

• transmission of infectious agent from parent to offspring

Transmission

Vehicle

• microbes get transferred through fomites(inanimate objects) , food, water, or air

Zoonotic pathogens

• can grow within animals, insects, and humans and they can act as reservoirs if the pathogen can grow

Yellow fever

• caused by a virus (microbe)

Zika

• caused by a bite from a mosquito (mostly)

• acute, viral, systemic infection

Endemic disease

• present at a relatively constant level

Epidemic disease

• indicates a large increase above the baseline level in an area

Pandemic disease

• a worldwide epidemic

Portals of Entry

• the eye

• oral (mouth)

• Genital or Sexual transmission

• respiratory

• through skin (wounds)

• Parenteral = pathogens injected into bloodstream by insect

Host Factors

• Level of Immunocompetence = influenced by age, genetics, behaviors (alcohol consumption)

• Exposure to pathogens = based on behaviors or occupations (healthcare, agricultural, recreation)

Microbial Structures of Biomacromolecules

Carbohydrates

• true polymer

• formed from saccharide monomers

• polysaccharides provide important structual and enegry storage molecules (cellulose = structural; starch = energy storage) and can also be attached to certain lipids and proteins

• recognize hydroxyl groups (OH)

Microbial Structures of Biomacromolecules

Lipids

• are amphipathic (hydrophilic and hydrophobic properties) molecules that assemble into layers in the presence of water

• not true polymers

• fatty acids have non-polar hydrocarbon chains

• phospholipids link fatty acids to polar head groups (phosphate head= hydrophilic; tails=hydrophobic)

• Phospholipid bilayer (cells produce them to form membrane barriers)

• triglyceride = 3 fatty acid chains connected to glycerol

Microbial Structures of Biomacromolecules

Nucleic Acids

• DNA = double-stranded, information library (5’ end = phosphate group; 3’ end = hydroxyl group)

• RNA = usually single stranded

• true polymers

• Adenine and Guanine (purines)

• Cytosine, Thymine, uracil=used in RNA instead of T (pyrimidines)

• phospate group, 5-carbon sugar, and Nucleobase (ATGC)

• DNA to RNA (transcription)

• RNA to proteins (translation)

Microbial Structures of Biomacromolecules

Proteins

• (polypeptides) are assembled from amino acids, linked by peptide bonds

• true polymers

• enzymes

• come in a variety of shapes that allow distinct functions

• amino terminus and carboxyl terminus

• primary structure = amino acids

• secondary structure = alpha helices and beta-pleated sheets linked together by hydrogen bonds on there perspective sides

• tertiary structure = helices and sheets come together and are bound by disulfide bonds

Bacteria Cell

The membrane

• provides a semi-permeable barrier

• fluid structure

• transport, secretion, environment sensing, energy acquisition

Lipid Bilayer

• limits movement of molecules into and out of cell (part of the cell membrane)

• Freely permeable = hydrophobic molecules (O2, CO2, N2)

• Somewhat permeable = small uncharged polar molecules (H2O, glycerol)

• Impermeable = large uncharged polar molecules (glucose and sucrose)

• Impermeable = Ions (H⁺, Na⁺, HCO₃^-, Ca²⁺ , Cl^-, Mg²⁺, K⁺)

Osmosis

• special type of diffusion that deals with the movement of water (high to low concentration)

Isotonic

• inside and outside of cell is equal (salt content)

• no change to cell size

Hypertonic

• more salt on the outside of cell

• water moves out of cell; which decreases its size

Hypotonic

• more salt in the cell

• so water comes into the cell which increases the cell size