bacteriology stack slackers facts by mike ori. disclaimer the information represents my...
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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 to H2O2 2O
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
EntryAdherence
SurvivalInjury
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 positivePneumococci – S. pneumoniae
Viridans – all other strepEnterococci – similar to but genetically distinct
from Streptococci
Lancefield antigens
Carbohydrate antigens categories of beta hemolytic streptococci
Group A strep characteristics
Small compact coloniesBeta 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 tooWound 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
MorphologyAlpha 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 namesakeMeningitis – common cause worldwide
Otitis media – most frequent childhood causeSinusitis
Does not cause pharyngitis or tonsillitis.
Pneumococcus virulence factors
CapsuleStreptolysin
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 DFormerly 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 non-productinve cough that lasts 1-5 days and is
followed by respiratory distress, cyanosis, and edema of the neck, mediastinum, and chest.