Bacteriology Stack
Slackers Facts by Mike Ori
Disclaimer
The information represents my understanding only so errors and omissions are
probably rampant. It has not been vetted or reviewed by faculty. The source is our
class notes.
The document can mostly be used forward and backward. I tried to mark
questionable stuff with (?).
If you want it to look pretty, steal some crayons and go to town.
Finally…
If you’re a gunner, buck up and do your own work.
A hydrophilic gel surrounding a bacterium in
most species composed polysaccharides but
that may be composed of amino acids in some
species.
Capsule
Capsule function
Servers as an antiphagocytic factor often by the
fixation of complement inhibitors such as
factor H. May also serve to create a slime
layer that adheres cells to surfaces.
Cell wall definition
A rigid layer external to the plasma membrane
of most bacteria.
Cell wall functions
Prevent osmotic destruction of the cell.
Regulate the environment adjacent to the
plasma membrane.
Determines the shape of the cell.
Gram positive wall structure
Linear glycan chains extending from the plasma
membrane cross linked by peptides to form a
rigid three dimensional scaffold like structure.
Lipoteichoic acids anchor the glycans to the
plasma membrane.
Gram negative cell wall structure
Lipid outer membrane containing that contains
Lipopolysaccharide endotoxin and transport
proteins surmounting a thin peptidoglycan
structure all of which lie outside the plasma
membrane. The peptidoglycan layer is less
cross-linked and considerably thinner than
that of gram negative cells.
Periplasmic gel
The peptidoglycan layer surrounding a gram
negative cell in between the plasma
membrane and the outer lipid layer
Lipopolysaccharide structure
Lipopolysaccharide function
A structural component of the outer membrane
of gram negative bacteria that is extremely
toxic to humans and other animals. It is a
general injury factor for gram negative
bacteria.
Flagella definition
A sweet chocolaty
substance secreted
by bacteria
Pili
Hairy-like tubular projections from the surface
of bacterial cells that are composed of pilin
and that play a role in attachment to surfaces,
conjugation, and virulence.
Nucleoid
The area of a bacteria that contains the
chromosomal DNA
Plasmid
A small covalently closed circle of double
stranded DNA that is separate from the
chromosome. These often convey resistance
and virulence genes.
Spores
Non-reproducing survival forms of bacteria that
are resistant pH extremes, heat, and uv
radiation
Siderophores
An iron chelator secreted by bacteria used to
obtain iron from the environment.
Fermentation
The transfer of electrons and protons via NAD+
to an organic acceptor. This results in the
creation of lactic acid, ethanol, etc.
Respiration
Substrate oxidation coupled to electron
transporters linked to an ultimate electron
acceptor such as molecular oxygen.
Aerobes
Bacteria that require O2 in order to grow.
Anaerobes
Bacteria that are killed by O2 usually due to a
lack of compounds that remove oxygen
radicals from the cell.
Super oxide dismutase
Converts superoxide O2 to H2O2
Catalase
Converts 2 H2O2 to 2H2O + O2
Facultative
Ability to grow aerobically using respiration or
anaerobically using fermentation
Microaerophilic
Requires oxygen for growth but at lower than
atmospheric levels
General secretory proteins
Secretory protein complexes that handle
proteins destined for the membranes or
periplasm
Type I export
A three protein complex that moves proteins
from the cytosol to the external environment
in a single step.
Type II secretion
A transport system that moves proteins into the
periplasm using GSP proteins but that moves
them to the extracellular space using
specialized transport proteins.
Type III secretion
Intricate protein complexes that move proteins
from the cytosol directly into target cells using
a contact dependent injection system
analogous to a syringe.
Type IV secretion
Conjugal transfer of DNA between bacteria or
between bacteria and eukaryotic cells
Type V secretion
Secretion systems whose protein products
directly encode their own export mechanisms.
These are then cleaved from the protein as
part of the export process
Operon
A regulator that controls a polycystronic area of
DNA that typically encodes proteins related to
a single function. E.G. the lactose transport
and catabolism genes.
Regulon
A regulator that controls multiple genes and
operons that are not polycystronic but that
are related to a common function.
Transformation
Uptake of naked DNA from the environment by
competent cells
Transduction
Transfer of genetic material by bacteriophages
Lytic phase
Virulent phase of a bacteriophage infection
Lysogenic phase
Quiescent phase of bacteriophage infection in
which genetic material is inserted into the
host chromosome but is not actively being
transcribed. May last for many generations.
Conjugation
Transfer of genetic material between bacteria
using a special plasmid and pili
Transposon
A genetic element that is able to insert itself into
DNA using site specific recombination
enzymes (transposases) encoded by the
element itself.
Pathogenicity
The ability to cause disease in a susceptible host
Virulence
The degree of pathogenicity
Pathogen
An organism that can cause disease under
favorable conditions
Normal flora
Microbes that frequently found in tissues of
normal, healthy individuals. Includes resident
and transient bacteria.
Carrier state
Potentially pathogenic organisms in residence
Priming effect
The development of the immune system under
the influence of normal flora
Exclusionary effect
Conditions produced by normal flora that block
the establishment of pathogens.
Steps of pathogenicity
Entry
Adherence
Survival
Injury
Exotoxins
Secreted substances produced by microbes that
damage host cells
A-B toxin
A two part toxin composed of a binding domain
that interacts with a host cell receptor
facilitating entry into the cell and an active
domain that functions within the host cell to
cause injury.
ADP-ribosylation
Addition of ADP ribose onto host cellular
proteins in a manner that alters the function
of the protein. This is a typical function of an
A-B exotoxin.
Endotoxin
Lipopolysacharides that are structural
components of gram negative outer lipid
layers. They consist of a long O antigen, a core
and a lipid A antigen.
LPS cytokines
IL-1 and TNF
Superantigen
A compound that causes the activation of T-cells
by binding to MHC-II molecules on APC cells in
a way that can activate T cells regardless of
the specificity of the T cell receptor.
Superantigen cytokines
IL-1 and TNF
Superantigen outcome
Shock due to excessive cytokine release
Pathogenicity islands
Large blocks of genes within a bacterial genome
that encode for proteins related to
pathogenicity and virulence. These areas have
genetic characteristics that are often different
from that of the host.
Coagulase positive, catalase positive, gram
positive cocci
Staphylococcus aureus
Coagulase negative, catalase positive, gram
positive cocci
Staphylococcus epidermis and other non aureus
staph
Staphylococcus culture conditions
Grows overnight on blood agar
Alpha toxin
Pore forming protein secreted by S. aureus
Pyrogenic superantigens
Family of proteins secreted by Staphylococcus
that stimulate systemic effects
Staphylococcus enterotoxins
Heat and acid stabile proteins secreted by
Staphylococcus that cause vomiting in humans
by acting directly on neural receptors in the
upper GI tract. A type of pyrogenic super
toxin.
Toxic shock syndrome toxin (TSST)
A pyrogenic supertoxin secreted by
Staphylococcus that leads to systemic effects
of hypotension, vasodilation, etc. The toxin is
often effectively elaborated from Staph
colonizing external media (such as tampons)
that are in contact with host tissues.
Exfoliative toxin
A toxin secreted by Staphylococcus strains that
causes blister like separation of the epidermis.
Staphylococcus carriage rate
30% carriage in the anterior nares
Furuncle/boil
A superficial skin infection that develops in a
hair follicle, sebaceous gland, or sweat gland
Impetigo
Skin pustules that often develop as a result of
superficial infection with Staphylococcus or
Streptococcus
Scalded skin syndrome characteristics
Exfoliating skin disease caused by exfoliatin
produced by Staphylococcal infection
Staphylococcal food poisoning onset
1-5 hours after ingestion of pre-formed toxins.
Alpha hemolysis
Partial hemolysis of RBC’s in an area around
bacterial colonies on a blood agar plate
resulting in an greenish area surrounding the
colony that is due to heme breakdown
products.
Beta hemolysis
The complete lysis of RBC in an area around
bacterial colonies on a blood agar plate
resulting in a clear area surrounding the
colony.
Catalase negative, gram positive cocci
Streptococci
Streptococcus Categories
Pyogenic Streptococci – Lancefield positive
Pneumococci – S. pneumoniae
Viridans – all other strep
Enterococci – similar to but genetically distinct
from Streptococci
Lancefield antigens
Carbohydrate antigens categories of beta
hemolytic streptococci
Group A strep characteristics
Small compact colonies
Beta hemolytic
GAS antigenic determinant
M protein – 80 serovars
M protein function
Antigenic GAS cell wall protein that binds
complement serum factor H to prevent
opsonization by activation of complement
cascades
Streptolysin O
A pore forming exotoxin secreted by GAS.
GAS pyrogenic exotoxins
Exotoxins secreted by 10% of GAS strains that
cause systemic effects like fever, rash, T cell
proliferation and B cell suppression. A similar
toxin is secreted by Staphylococcus aureus.
GAS Diseases
Pharyngitis – most common among school age
children
Impetigo – Staph aureus co-colonization too
Wound infections
Streptococcal toxic shock syndrome – unlike SA,
this is invasive
Post streptococcol glomerulonephritis
Deposition of immune complexes within the
glomerulus that result in typical glomerular
dysfunction symptoms beginning up to 6
weeks after pharyngitis or skin infections.
Acute Rheumatic Fever
Immune reaction characterized by rash, carditis,
subcutaneous nodules, chorea, and migratory
polyarthritis occuring up to three months after
pharyngitis. Repeated attacks lead to
progressive endocardial damage.
Streptococcal pharyngitis symptoms
Usually self limiting bacterial infection of the
pharynx that results in throat pain, malaise,
fever, and headache.
Erysipelas characteristics
A rapidly advancing, well demarcated area of
erythema and edema caused by Streptococcus
that primarily affects the dermis leading to
pain, systemic manifestations, fever, and
lymphadenopathy
Scarlet fever characteristics
Deep red rash on the temples, cheeks, and
buccal mucosa coupled with a yellow white
exudate on the tongue punctuated by red
papillae (strawberry tongue). A diffuse red
“sandpaper” rash appears on the second day
of illness and spreads to the trunk
Scarlet fever cause
Streptococcal pyrogenic exotoxins
Rheumatic fever antibodies
Possible cause of high titer of anti-streptolysin O
(ASO) antibodies found in the serum.
Group A Streptococcus diagnosis
Rapid strep test for GAS looking for group A
antigen. If negative, must swab and culture
on blood agar looking for beta hemolysis
(pyogenic strains) and bacitracin susceptibility
indicating GAS.
Group B strep characteristics
Polysaccharide capsule containing sialic acid.
Nine antigenic types (Ia, Ib, II- VII)
GBS capsule characteristics
Polysaccharide capsule containing sialic acid that
binds complement factor H thus interfering
with complement fixation.
GBS diseases
Sepsis, meningitis, or pneumonia within first few
months of life.
No association with rheumatic fever or acute
glomerulonephritis.
GBS infant transmission path
Vertical
GAS and GBS immunity characteristics
Immunity conveyed only to the infecting strain.
There are 80 M GAS serotypes and 9 GBS
serotypes.
GBS perinatal prevention
3rd trimester screening of mother (wk 35-37)
with penicillin G by IV or ampicillin given to
positives during labor and delivery.
Streptococcus pneumoniae characteristics
Gram positive, alpha hemolytic, catalase
negative, polysaccharide encapsulated
(virulent strains), oval diplococci arranged in
end to end pairs giving a lancet shape.
AKA pneumococcus
Pneumolysin
Pore forming toxin elaborated by Streptococcus
pneumoniae that disrupts the pulmonary
endothelium to afford access to the alveoli
and thence the blood.
Yes, thence.
S Pneumoniae antigenicity
The polysaccharide capsule is antigenic but
there are 90+ serotypes.
Diagnosis
Morphology
Alpha hemolytic on blood agar plates
Accelerated autolytic process with bile salts.
Sensitive to optochin.
Either optichin sensitivity or bile salts separates
from the viridans.
Pneumococcal disease
Pneumonia – its namesake
Meningitis – common cause worldwide
Otitis media – most frequent childhood cause
Sinusitis
Does not cause pharyngitis or tonsillitis.
Pneumococcus virulence factors
Capsule
Streptolysin
Strep pneumoniae vaccine
Polyvalent (23) form prepared from capsular
polysaccharide is suitable for adults.
7-valent conjugated vaccine is suitable for
infants.
Balance coverage against effect.
Pneumococcus resistance factor
Alterations in transpeptidases decrease beta
lactam capabilities. Penicillinases are not
elaborated.
GBS treatment
Penicillin
GAS treatment
Penicillin
Enterococci Morphology
Similar to pyogenic streptococci.
Gram positive, catalase negative cocci with
lancefield group D
Formerly classified as streptococci
Enterocci disease characteristics
Opportunistic infection by endogenous flora as a
result of indwelling devices, surgery, trauma,
etc.
Cause UTI.
Enterococci treatment
Ampicillin
Resistance
Inherently resistant to beta lactams and
aminoglycosides (why inherent??)
Efficient plasmid and transposons
characteristics.
Vancomycin resistance emerging.
What does cornye mean
Club as in the weapon, not the dance hall
Diptheria toxin genetic basis
Acquired from a bacteriaphage. Hence not all
Corynebacterium diphtheriae produce DT
C. Diphtheriae characteristics
Gram positive club shabed, pleomorphic rods.
Carrier state longevity
Weeks, months, years
DT characteristics
An A-B toxin whose active portion catalytically
ADP-ribosylates elongation factor 2 on
ribosomes thus disabling them.
Why does DT not affect diphtheria cells?
They do not use EF-2 in their ribosomes.
DT vaccine basis
Formalin treatment of DT causes inactivation of
the binding subunit thus disabling entry into
cells while preserving antigenicity.
Diphtheria presentation
Pharyngitis and tonsillitis with fever, sore throat,
malaise and a psuedomembrane composed
of a coagulum of fibrin, leukocytes and cellular
debris that covers either the tonsils, pharynx,
soft palate, or uvula.
DT effects
Local damage causes generation of
pseudomembrane. Systemic absorption
causes myocarditis and other organ damage.
Diphtheria diagnosis
Primarily clinical diagnosis. Swabs must be
grown on tinsdale media.
Listeria monocytogenes characteristics
Gram positive beta hemolytic rod able to grow
slowly at 1C
Listeria reservoir
Animals and human intestinal colonization
L. monocytogenese transmission paths
Food products such as dairy and ready to eat
sausages.
Vertical transmission in utero or during delivery
Internalin
Listeria cell surface protein that stimulates entry
into membrane vacuoles.
Listeriolysin O
Pore forming exotoxin used by Listeria to
rupture vacuoles thus facilitating its escape
into the cytoplasm.
Listeria movement system
Listeria moves through the cell by controlling
the actin filaments
Listeria immunity type
Since Listeria is an intracellular pathogen, its
clearance depends on cell mediate immunity.
Listerosis presentation characteristics
Presents usually only after disseminated.
Listeria disease
Meningitis
Bacillus characteristic
Gram positive, aerobic, spore forming rods
Bacillus anthacis capsule
Unique oolypeptide capsule
Cutaneous anthrax description
A typicall self limiting cutaneous infectoin begins
2-5 days after exposure and forms a black
eschar.
Pulmonary anthrax characteristics
A prodrome of malaise, fever, and nonproductinve cough that lasts 1-5 days and is
followed by respiratory distress, cyanosis, and
edema of the neck, mediastinum, and chest.