BE400 Infections in Medical Devices Final

Binomial nomenclature

• two word naming system

• genus (capitalized) + species “specific epithet”

Strains

• subtypes of one species of microorganism

• ex. Staphylococcus epidermis 0594

microbes are generally

unicellular and not visible to the naked eye

How big must an object be to be visible without magnification?

~100 micrometers

Which domains are microorganisms found in?

All three: Archaea, Bacteria, and Eukarya

What do prokaryotic microorganisms lack?

a nucleus and other organelles

Bacteria characteristics

• single-celled organism (unicellular)

• can be harmless or pathogenic (disease-causing)

• most cell walls contain peptidoglycan

• many in human flora, and can be pathogenic

Acute infections

• conditions that begin suddenly and is often short-lived

• rapid onset of symptoms

Examples of acute infections

influenza, UTI

Chronic infections

• Condition that develops gradually and persists over time

• symptoms develop slowly and are slow to resolve

Chronic infection examples

• Hepatitis B and C

• lyme disease

Subacute infections

symptoms develop more slowly than acute, but faster than chronic

What is the initial site of infection from which organisms spread called?

focal

What type of bacteria is this?

coccus

What type of bacteria is this?

bacillus

What type of bacteria is this?

Vibrio

What type of bacteria is this?

coccobacillus

What type of bacteria is this?

Spirillum

What type of bacteria is this?

spirochete

Bacteria general definition

• described by general shape (cell morphology)

• wide range of metabolic capabilities and can grow in many different environments

• anaerobic and aerobic

What does the bacterial cell wall do?

• morphology is maintained by cell wall

• protects cell from changes in osmotic pressure

isotonic solution

• no net movement of water particles

• cell membrane is attached to the cell wall

hypertonic solution

• water particles move out of the cell

• cell membrane shrinks and detaches from cell wall

plasmolysis

cell membrane shrinks and detaches from cell wall

hypotonic solution

• water particles move into the cell

• cell wall counteracts osmotic pressure to prevent swelling and lysis

nucleiod

• area where chromosomes are in bacterial cells

All cellular life has DNA genome organized into one or more __________

chromosomes

Typical traits of prokaryotic chromosomes

• circular

• haploid (unpaired/single-stranded)

• not bound by a nucleus

Nucleoid associated proteins (NAPs)

interact with DNA to aid organization and chromosomal packaging

What do the proteins on the surface of the plasma membrane do?

• cell-to-cell communication

• sense environmental conditions and pathogenic virulence

glycoprotein/glycolipid

associated carbohydrates (sugars) that interact with the external environment

types of membrane transport

• simple diffusion

• facilitated diffusion

• active transport

peptidoglycan

• only found in bacteria

• long chains of alternating molecules

• crosslinked heteropolymer of alternating sugars

• gives the cell its shape

Crosslinked heteropolymer of alternating sugars in peptidoglycan

• N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

• NAM and NAG connected by peptide bridges that vary based on type of bacteria

• cross-linking happens via transpeptidase

gram-positive bacteria

• thick peptidoglycan layer (30-100nm)

• teichoic acid

How does teichoic acid contribute to gram-positive bacteria?

pathogenicity

gram-negative bacteria

• outer and inner membrane

• thin peptidoglycan (<4nm)

• lipopolysaccharide (LPS)

How does LPS contribute to gram-negative bacteria?

acts as endotoxin

What color are gram-negative bacteria after staining?

pink

What color are gram-positive bacteria after staining?

dark purple

glycoalyces

• additional envelope structures exterior to cell wall

• sugar coat

• capsule

• slime layer

• allows cells to adhere to surfaces, aiding in formation of biofilms

glycoalyx capsule

organized layer comprised of polysaccharides or proteins

glycoalyx slime layer

loosely attached layer composed of polysaccharides, glycoproteins, or glycolipids

Fimbriae and pilli

aid in attachment to surfaces

flagella

aids in movement in aqueous environments

binary fission

process by which bacteria asexually reproduces

Doubling time

amount of time it takes for the population to double through one round of binary fission

What is doubling time dependent on?

species and growth environment

lag phase

• initial growth on curve

• no increase in number of living bacterial cells

log phase

exponential increase in number of living bacterial cells

stationary phase

• plateau in number of living bacterial cells

• rate of cell division and cell death roughly equal

death/decline phase

cells begin to die

Parameters for growth curve

• microorganisms grown in batch culture

• no nutrients added or removed

• predictable curve

culture density

• number of cells per unit volume

• can calculate population in fixed volume

virulence

ability of a microorganism to cause disease (pathogenicity)

infection

occurs when a microbe overcomes the defense barriers and lives inside the host

disease

infections that result in damage to the host tissue or disruption of normal function

pathogenecity

ability of microbial agent to cause disease

virulence

degree to which an organism is pathogenic

ID50

• infectious dose 50

• dose that will infect 50% of a population

LD50

• lethal dose 50

• dose that will kill 50% of a population

primary pathogen

cause disease in a host regardless of the host’s resident microbiota or immune system

opportunistic pathogen

can only cause disease in situations that compromise the host’s defenses, such as the body’s protective barriers, immune system, or normal microbiota

What most a microbe do first to infect a host?

• attach to a specific receptor

• no receptor = no attachment

tissue tropism

• specificity of microbe to attach to tissue

• why a specific infectious disease only involves specific tissue

attachment sites

areas of microbial attachment, may be animal species specific

Examples of attachment sites

• pili

• specialized surface proteins

metabolism

chemical reactions that occur within a cell

exergonic reactions

spontaneous reactions that release energy

catabolism

• break down complex molecules

• energy can be stored in bonds of complex molecules that is released to then drive anabolic reactions

Is catabolism exergonic or endergonic?

exergonic

endergonic reactions

require energy

anabolism

converts simple molecules into more complex molecules, fueled by cellular energy

Is anabolism exergonic or endergonic?

endergonic

glycolysis

• catabolism of glucose

• produces energy (ATP)

• produces reduced electron carriers

• produces precursor molecules for cellular metabolism

Where does glycolysis take place?

cytoplasm

Krebs cycle products

• 2 CO2

• ATP or GTP

• 3 NADH

• CoA

Energy investment phase of glycolysis

• start with glucose and 2 ATP

• reaction occurs to yield 2 ADP and fructose diphosphate

• fructose becomes 2 glyceraldehyde 3-phosphate

Energy payoff phase of glycolysis

• start with 2 glyceraldehyde 3-phosphate

• NAD+ reduces to NADH

• 2 ADP becomes 2 ATP

• carbon chains become 2 pyruvate

Products of the breakdown of a single glucose molecule through glycolysis

• 2 ATP

• 2 NADH

• 2 pyruvate molecules

chemiosmosis

flow of hydrogen ions across the membrane

ATP synthase

membrane-bound enzyme complex that channels H-

cellular bioenergetics

ATP is produced from pH and electrostatic charge gradients (and) set across the cytoplasmic membrane

What happens if H+ ions are neutralized by hydroxide ions

the concentration gradient collapses and impairs energy production

How does pH influence proteins and disrupt hydrogen bonding?

• alters folding pattern

• alters activity

acidophile

thrives in low pH

neutrophile

thrives in neutral environments

alkaliphile

thrives in high pH

What does a pH microbial growth chart show?

• optimum growth

• maximum growth

• minimum growth

pyschrophiles temperature range

-5 to 20 degrees C

mesophiles temperature range

15 to 45 degrees C

thermophiles temperature range

45 to 80 degrees C

hyperthermophiles temperature range

65 to 105 degrees C

States pf bacterial existence

• biofilm-associated (sessile) state

• persister state

• planktonic

bio-film associated (sessile) state

• bacteria attach to a surface and become embedded in a self-produced extracellular polymeric matrix (EPS) matrix

• this forms a biofilm

• this state provides protection from antibiotics, immune responses, and environmental stressors

persister state

• subpopulation of bacteria that enters a dormant, non-replicating phase within a biofilm or planktonic culture

• these cells are highly tolerant to antibiotics but can evert to an active state when conditions improve

Biofilm formation steps

0. Formation of conditioning layer

1. reversible attachment of planktonic cells

2. first colonizers become irreversibly attached

3. growth and cell division

4. production of EPS and formation of water channels

5. attachment of secondary colonizers and dispersion of microbes to new sites

Amount of time each step in biofilm formation takes

1. seconds

2. seconds, minutes

3. hours, days

4. hours, days

5. days, months

Acute inflammation

• vasoconstriction to reduce blood loss—brief

• vasodilation due to histamine response

• increased blood flow dilutes toxins and bacterial products

chronic inflammation

• often results in an ongoing lower-level battle between host organism and pathogen

• granulomas formed