622 10/28 GLA pt 2 Bacteria and Viruses

Simple Bacterial Replication

replicates circular chromosome, grow cell wall and components, split one bacteria into two cells

may not actually physically come apart, and may stick together as chains

Gram + vs Gram - Bacterial Replication

gram +: wall is built between the bacteria

gram -: constriction between two cells that then blebs off

Bacterial Growth Chart

3 Phases of Bacterial Growth

lag phase

log phase

stationary phase

Lag Phase

first phase of bacterial growth, metabolically active but not much replication, acclimation

building everything they need to replicate

Log Phase

second phase of bacterial growth, exponential growth with steep growth, doubling time varies widely among microbes

ex: e coli is 20 mins, m tuberculosis is 800 min

Stationary Phase

third phase of bacterial growth, less replication, less metabolism, nutrients depleted

rate of cell division = cell death

death rate eventually outpaces growth rate

Bacteriostatic Drugs

stop bacteria replication, push bacteria into stationary phase

Bacteriosidic Drugs

burst/lyse and kill cells, push bacteria into death/decline phase

Bacterial Spores

made by a few gram + (bacillus and clostridium), form endospores

Endospores

made to resist environmental stress, dormant until exposed to water, difficult to kill which makes them difficult to get rid of for healthcare

can withstand heat, radiation, pH, pressure, and chemicals

What makes endospores so resistant?

they are dormant until exposed to water

Sporulation

axial filament formation

septum formation and forespore development

spore develops within bacteria, making it very resistant

Endospores for Identification

central

subterminal

terminal/swollen

Spore Stain

Anaerobic Bacterial Infections (no O2)

deep tissue, abscess formation, foul-smelling pus, gangrene, severe tissue damage

Oxygen Tolerance

bacteria can tolerate certain concentrations of O2, pathogenic bacteria have preference of anatomical site based on O2 preference

tool to grow, differentiate, and identify bacteria

Oxygen Tolerance Diagram

Obligate Aerobe

require oxygen, so it will only grow at the top of the test tube

ex: bortadella pertussis

Obligate Anaerobe

oxygen is toxic, so it will only grow at the bottom of a test tube

ex: clostrinium botulinum

Facultative

has an oxygen preference, but can grow in other

ex: e. coli

Oxygen in Different Areas of the Body

Intracellular Bacterial Growth

growth in host cell, can be obliagte or facultative

Obligate Intracellular

they cannot replicate without host cell machinery or energy

Obligate Intracellular Bacteria

chlamydia

rickettsia

coxiella

certain myobacteria

Facultative Intracellular

they prefer intracellular living (especially to replicate) but can survive outside of host cells

General Requirements for Bacterial Growth

oxygen (either presence or absence)

carbon source

nitrogen

energy source

water

Carbon

bacteria utilize different carbon sources and produce different products

we exploit this characteristic to differentiate and identify specific bacteria, and to make foods

Energy Source

derived from breakdown of organic substrates, known as catabolism, not just glycolysis

substrates: carbs, lipids, proteins

what is the energy then used for?

Fermentation

process where organic molecule acts as an electron donor and one or more of its organic products act as a final electron acceptor, resulting in anaerobic energy production

Fermentation as Differentiation

MacConkey Agar is used to test for the ability to ferment lactose

ex: salmonella does not and is clear, e coli does and is pink

Bacterial ETC

localized to cytoplasmic/inner membrane, more complex and shorter so less energy is produced

utilized to differentiate bacteria

2 Ways ETC is Used to Differentiate Bacteria

oxidase test

nitrate reduction test

Virulence

how harmful a given microbe is, based on their growth/energy use/products/metabolism

low virulence = less harmful

high virulence = more harmful

Common Bacterial Virulence Factors

adhesion and invasion (proteins and polysaccharides)

secretion

toxins

iron acquisition (from host, can lead to anemia)

siderophores

antibiotic resistance enzymes

More Virulence Factors =

more pathogenic

Adherence to Cells as Virulence Factor

adhesins and biofilms

Adhesins

mediate adherence to cells and contribute to virulence

pili, glycocalyx

spike proteins

Biofilms

protective matrix, contributes to virulence

resistant to antibiotics and antibodies, slows healing

2 Things that Contribute to Bacterial Invasion

collagenase and hyaluronidase

coagulase

Collagenase and Hyaluronidase

contributes to bacterial invasion, degrade collagen and hyaluronic acid and break down extracellular matrix

allows spread through subcutaneous tissue

Coagulase

contributes to bacterial invasion in blood, accelerates formation of fibrin clot from fibrinogen, clot may protect microbe from immune system infiltration

may coat microbe with fibrin as protection as well

Exotoxins

gram + or gram -, extremely toxic, usually do not produce a fever in the host

Endotoxin

only gram -, part of lipid a in LPS, moderately toxic, usually produces fever in the host

What do bacteria use iron for and why is iron acquisition contributing to virulence?

they use it for metabolism, replication, and production of virulence factors

it can take iron away from the host and make them anemic

Immune Evasion Examples

encapsulation and biofilms

adaptation to live within cells, including immune cells

proteases that cleave the antibodies

mutations

molecular mimicry (camoflauge)

resistance to enzyme destruction

Bacterial Targets of Antibiotics

antibiotics target specific characteristics of bacteria

Mechanisms of Antibiotic Resistance

enzymatic inactivation of antibiotic

modification of the bacterial target via mutation

active export of drug out of bacteria using pumps

mutation in porin to reduce bacterial permeability

biofilm formation

Enzymatic Inactivation of Antibiotic

mechanism of antibiotic resistance, microbes that have b-lactamase can inactivate penecillin, cephalosporins, and carbapenems (the b-lactams)

Modification of the Bacterial Target via Mutation

mechanism of antibiotic resistance, one certain mutation in peptidoglycan can render vancomycin ineffective

Active Export of Drug out of Bacteria Using Pumps

mechanism of antibiotic resistance, multidrup-resistance pumps (MDR pumps) and efflux pumps can pump out tetracyclines

Mutation in Porin to Reduce Bacterial Permeability

mechanism of antibiotic resistance, porin structural change can stop penicillin from entering bacteria

Biofilm Formation

mechanism of antibiotic resistance, inhibits access of antibiotics