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.