Micro bacteria

infection

presence and multiplication of an organism in a host

infectious disease

host exhibiting an adverse response to the presence of an infecting organism

primary infection

First infection by a microorganism

reinfection

Subsequent infection by the same organism

Reactivation

Organism lies dormant in the body & becomes active at a later date under different conditions

secondary infection

superimposed infection of a different pathogen in an already infected host

Nosocomial

infection acquired during a hospital stay or at a medical facility due to infection from the environment, instruments, prosthetics

iatrogenic

physician induced infection due to therapy
includes immune suppression from chemo

Coloization

Adherence of the microorganism to the host
Specific interaction between the microbe & host in which a bond is formed

Adhesion

Facilitates adherence of the microbe to the host
Requires surface structures or virulence factors
Adhesins, fimbriae, pili

Evasion of host defenses

Ability to resist phagocytosis & other host defenses
Requires production of virulence factors
Toxins, cell surface proteins, capsule, enzymes

Invasion and multiplication

Replication after attachment to host cells
Needs to avoid or overcome host responses
Production of enzymes or toxins that destroy host immune response
Morphology changes of surface antigens

composition of human microbiota

bacterial- mostly
fungi
parasites
viruses- rare

human microbiota varies with

age, geography, external factors, diet, systemic health, contact lens wear

Origin of microbiota

fetus is in sterile environment until birth (once exposed to microorganisms in environment, must create a host-microbe relationship)
changes throughout different stages of life and environmental conditions

we are colonized by how many different microbial species

~100

total organism load of microbiota

~100 trillion

symbiosis/ mutualism

Relationship between 2 or more organisms where each benefits from the presence of the other

Commensalism

Relationship in which the organism benefits, but no benefit or harm is done to the host

Parasitism

relationship in which one species benefits at the expense of the other

carrier state

potentially pathogenic organism establishes residence on the body
possible to transmit to a different host
may be resident or transient organisms

resident flora

organisms that have establishes a niche at a particular body site
may occupy indefinitely
(live there)

transient flora

acquired from environment
establish a brief residency at a particular body site
often replaced by resident flora
more likely pathogenic than resident
(guests)

is microbial essential to life

no

suppression of normal flora creates what

a void that allows colonization by opportunistic organisms

microbiota of blood, body fluids, and tissues, is it sterile

yes generally sterile

skin microbiota is in what type of environment

predominantly dry, slightly acidic and aerobic environment
increased prevalence on moist skin areas

conj microbiota

similar distribution to lid skin in lower numbers
inhibited by flushing effects of blinking and high lysozyme content of lacrimal secretions

oral cavity microbiota

high number of organisms
mouth & pharynx highly colonized by facultative & anaerobic bacteria, saliva contains mixed organisms

Stomach microbiota

Few organisms capable of surviving gastric acid & peptic enzymes

intestines microbiota

Scant flora in small intestines
Lower ileum begins to resemble colon

colon microbiota
variable based on?
what % of feces is comprised of bacteria

most abundant and diverse microbiota in the body
mostly anaerobic, some facultative
variable based on diet
high meat diets have increased Bacteroides species and other gram negative bacilli compared to diets high in fish or veggies
feces of adults comprised of 25% bacteria by weight

upper respiratory tract microbiota:
external nares
nasopharynx
sinuses

external 1cm of anterior nares have flora similar to skin
nasopharynx similar to mouth
sinuses generally free of organisms

lower respiratory tract microbiota

protected by epithelial cilia and movement of mucociliary blanket
only transient organisms gain access to trachea and larger bronchi

geniturinary tract microbiota

Distal 1cm of urethra colonized by organisms derived from perineum
Rest of urinary tract sterile
uterus- sterile

positive role in health and disease for microbiota

Contribute to normal microbial defenses & toxin degradation
Assists in maturation of immune system
Prevents colonization by potentially harmful organisms
Synthesis of vitamins & nutrients

negative role in health and disease microbiota

Imbalance leads to opportunistic infection
Overproduction of resident flora leads to infection
Transient flora may proliferate to cause infection

Pathogenesis

Ability of a microbe to produce disease

true pathogens

Organism able to cause disease in a healthy, immune-competent individual
not usually part of microbiota

opportunistic pathogen

Organism that causes disease only in immune-compromised state
Often found in normal microbiota

Virulence

Relative ability of a microorganism to cause disease or the degree of pathogenicity
Evade or overcome host defenses

host defenses to infection (7)

Physical barriers
Cleansing mechanisms
Antimicrobial substances
(Enzymes, antibodies, β-lysins, interferon)
Indigenous microbial flora
Phagocytosis
Inflammation
Immune response

microbial resistance factors to host defenses (4)

Ability to resist phagocytosis
Surface structures
(Adhesins)
Intracellular survival & proliferation
Production of toxins & enzymes
(Exotoxins)
(Endotoxins)

Exotoxins

Produced by gram positive & gram negative organisms
Secreted by organism into extracellular environment or by cell lysis

Endotoxins

Portion of the gram negative outer cell membrane
NOT a component of gram positive organisms
No enzymatic activity
No specificity in their activity against the host

Disease state is noticeable when

Disease state only noticeable if tissue damage occurs

toxins

poisonous substances produced by an organism to interact with host cells

universal signs of infection

fever/ heat
pain
redness
swelling

body area and offending organism produce different signs/ symptoms

considerable overlap

Eukaryotic cells:
size
contain
located in what

large and complex structure 10-100µm
Contain a true nucleus, organelles, & cytoskeleton
Plant, animal cells

prokaryotic cells
size,
is there a nucleus?
what type of cell envelope
what does a plasma membrane do
what is bacterial DNA
growth depends on what
multiple copies are what
ribozymes synthesize

Smaller
No nucleus or membrane bound organelles
More complex cell envelope
Plasma membrane to regulate what enters the cells nucleoid
Bacterial DNA - circular molecule arranged loosely within the cell
Number depends on growth conditions: Rapidly growing cells have more nucleoids
Multiple copies are identical
Ribosomes to synthesize proteins

cell envelope of prokaryotic cells
what type of structure
protects against what
components

Multi layer structure
Protects organism from environmental stresses
Components:
Cell / plasma membrane
Cell wall
Capsule & gylcocalyx
Cell appendages
Flagella
Pili
Fimbriae

plasma membrane of cell envelope of prokaryotic cells
contain sterols?
what type of barrier
location of what

Phospholipid bilayer with embedded proteins
No sterols present Exception: Mycoplasma
Osmotic barrier
Location of electron transport chain

cell wall (prokaryotic cell)
maintains what
prevents what

Maintains shape
Prevents bursting from high osmotic pressure within
Different morphologies based on gram staining characteristics
~Gram positive
~Gram negative
~Acid-fast (modified gram positive cell wall)

cell wall staining purpose

Allow for visualization of cells
Distinguish characteristics of cells for recognition

cell wall staining process

1. Stain with crystal violet dye for 60 seconds
2. Wash off & flood with iodine solution for 60 seconds
3. Wash off & decolorized with 95% alcohol
4. Counter- stain with safranin for 30 seconds

gram positive
stain adheres to what

blue/purple
crystal violet stain adheres to the thick peptidoglycan layer

gram negative

red/pink
crystal violet washes off, safranin binds to cell wall

composition of gram positive cell wall

cytoplasmic membrane- phospholipid bilayer with embedded proteins
thick peptidoglycan layer- protective and
has wall techoic acid- anchored to peptidoglycan and lepteichoic acid- anchored to plasma membrane

composition of gram negative cell wall

Cytoplasmic membrane
Periplasmic space which is a Gel-filled space containing proteins & enzymes
Thin peptidoglycan layer which contains murein lipoprotein
Outer membrane of Phospholipid bilayer contains lipopolysaccharides

function of Gram Negative Cell Wall

Barrier to hydrophobic compounds & harmful substances
Contains porin proteins which allow water-soluble molecules to enter the cell
Provides attachment sites

gram negative cell wall lipopolysaccharide (LPS) components for O-specific side chains

Outer oligosaccharide units
Variable lengths specific to different organisms Play a role in adherence of organism to host cell

gram negative cell wall lipopolysaccharide (LPS) components for core polysaccharides

anchor sections together

gram negative cell wall lipopolysaccharide (LPS) components for lipid A

Disaccharide which anchors LPS to the cell wall
Endotoxin
When cell lysed, fragments released into circulation lead to non-specific symptoms

acid fast cell envelope composition

Modified gram positive cell wall Thin peptidoglycan layer
Mycolic acid - waxy layer of glycolipids & fatty acids bound to exterior wall
Forms a strongly hydrophobic lipid shell altering its permeability
ex. Mycobacterium sp.
Stain RED

cell envelope glycocalyx capsule:
is it well defined
function
composed of

Condensed, well-defined layer
Protective barriers to host immune recognition
Gram positive & gram negative
Function as virulence factors by helping to evade phagocytosis
Composed of polysaccharide polymers or polyproteins

cell envelope glycocalyx slime layer

Loosely associated with the cell
Protective
Prevents desiccation
Assists in adherence of bacteria to surfaces

cell appendages- flagella

motility organ
protein filaments that rotate to allow the bacterium to be motile

Monotrichous

flagellum that extend from one end

lophotrichous flagella

occur on one end in tufts

peritrichous flagella

occur on all sides of the bacterium

polar flagella

single flagella occurring at both ends of the bacterium

Pili

non-motile, long, hollow protein tubes
allow connection of bacteria and DNA exchange

Fimbriae

Non-flagellar, sticky, proteinaceous, hair-like appendages
Adhere bacterial cells to each other, or to environmental surfaces

genetic material of prokaryotic cells: Nucleoid

Attached to mesosome in the cell membrane
Contains DNA material
Generally single, continuous circular molecule
Number depends on growth conditions
Rapidly growing bacteria have multiple copies

genetic material for prokaryotic cells: Plasmids

Extrachromosomal, circular, double stranded (ds) DNA located in the cytoplasm
Not essential for bacterial cell growth Number depends on species Self-replicating
Passed to daughter cells via binary fission or transferred during conjugation

cytoplasmic structures for prokaryotic cells:
does it have membrane bound organelles

no

cytoplasmic structures for prokaryotic cells: ribosomes

Free-floating in cytoplasm & attached to cytoplasmic reticulum
Synthesize proteins
70s
Dissociate into 50s & 30s subunits

cytoplasmic structures for prokaryotic cells: endospores

Produced by some species in response to harsh environments Small, dormant, asexual spores
Become vegetative when harsh conditions removed

Bacterial Morphology Shapes

cocci
bacilli
spirochetes
vibrios
filamentous
pleomorphic

size of cocci

1 µm

size of bacilli

0.5 - 1 x 3 µm

size of spirochetes

0.3 to 0.6 - 1 to 3 µm

Cocci shape

Spherical, kidney-bean, or lancet-shaped

Bacilli shape

Rod shaped, ends may be blunt, tapered or rounded

spirochetes shape

Spiral shaped

vibrios shape

comma shaped

Filamentous shape

elongated, thin

pleomorphic shape

no defined shape

bacterial morphology arrangement singular

cocci or bacilli
coccobacilli

coccobacilli

elongated, oval shaped organism

Bacterial morphology
Arrangement: pairs

diplo

Bacterial morphology
Arrangement: clusters

staphylo

Bacterial morphology
Arrangement: chains

strepto

Bacterial morphology
Arrangement: side-by-side

palisading
only in bacilli organisms

bacterial morphology: gram positive

streptococci
staphylococci
enterococcus
(all cocci are no spores)
corynebacterium
listeria
(no spore)
bacillus
clostridium
(spore)

Gram negative organisms

Cocci:
neisseria
moraxella
Bacilli: all others
Spirochetes:
borrelia
leptospira
treponema

acid fast bacterial morphology

mycobacteria

bacterial morphology: no cell wall

chlamydia
mycoplasma

what is the pH for most bacteria

neutral, except for stomach bacteria which is acidic