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

http://upload.wikimedia.org/wikipedia/commons/a/a7/LPS.jpg

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.