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PYOGENIC COCCI Streptococcus Enterococcus Staphylococcus Neisseria

Streptococcus

The streptococci Gram-positive cocci Divide in one plane Don’t separate after division - form chains 2 genera: Streptococcus Enterococcus

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Laboratory Tests of Significance Catalase negative* *Catalase - an enzyme that breaks down peroxides such as hydrogen peroxide resulting in O2 and water

Ecological niches There are large numbers of streptococci in the mouth Several different species are associated with the different ecological niches in the mouth

Oral Ecological Niches Harboring Streptococci Tissue   Organism Hard Soft Plaque Tongue Mucosa  S. sanguis +++  S. mutans +++  S. salivarius +++ ++  S. mitis ++ +++

Streptococcal diseases Two of these species are associated with different diseases S. sanguis - Subacute bacterial endocarditis S. mutans - Tooth Decay (Dental Caries)

"S." S. pyogenes can be in the throat or on the skin and cause no symptoms of disease But it may also cause infections that range from mild to severe and even life-threatening

"The majority of infections are..." The majority of infections are relatively mild illnesses, such as impetigo and "strep throat"

"Occasionally the organisms reach the..." Occasionally the organisms reach the blood, deep muscle and fat tissue, or the lungs, and cause invasive infections Two of the most severe but least common forms of invasive S. pyogenes disease are necrotizing fasciitis and streptococcal toxic shock syndrome

"Necrotizing fasciitis (sometimes described..." Necrotizing fasciitis (sometimes described by the media as "the flesh-eating bacteria") is a destructive infection of muscle and fat tissue

"Streptococcal toxic shock syndrome is..." Streptococcal toxic shock syndrome is a rapidly progressing infection causing shock and injury to internal organs such as the kidneys, liver, and lungs

Hemolytic differentiation Blood has long been incorporated into culture media In the early days of bacteriology, it was seen that streptococci isolated from purulent throat and skin infections often caused complete lysis of the red blood cells Lysis is a dissolving of the cells

"When red blood cells are..." When red blood cells are involved it is called hemolysis Three types of reactions were observed when streptococci were grown on blood agar

"The first type was an..." The first type was an area of complete clearing in the opaque red agar surrounding a streptococcal colony This was a true hemolysis Streptococci isolated from purulent throat and skin infections often did this

"The second type was an..." The second type was an area of yellow to greenish color The cells, when examined under a microscope were found to have shrunk The streptococci most commonly found in the oropharynx, the ones not associated with disease, did this

"A third group of streptococci..." A third group of streptococci were found to have no affect on the red blood cells

Three types of hemolysis Alpha ( a ) Yellowish to Greenish Beta ( b ) Complete Clearing Gamma ( g ) No Change

"Alpha Hemolysis" Alpha Hemolysis

"Beta Hemolysis" Beta Hemolysis

"Gamma Hemolysis" Gamma Hemolysis

Groups of Streptococci Pyogenic Streptococci Oral Streptococci Enterococci

Pyogenic streptococci Pyogenic means "pus producing” There are two major species of streptococci in the pyogenic streptococci Streptococcus pyogenes Streptococcus pneumoniae

Streptococcus pyogenes

"Most early work focused on..." Most early work focused on the b-hemolytic organisms because they seemed to be involved in the most important diseases Attempts were made to classify these organisms into different species But using sugar fermentations and other biochemical tests was not successful

Work of Rebecca Lancefield Then a Microbiologist named Rebecca Lancefield used serology to classify the b-hemolytic streptococci

Group A Beta Strep

Virulence Factors Not all group A strep are equally virulent Only cells containing the M protein are virulent More than 70 different M types have been identified and some have been correlated with certain diseases

Correlation of Diseases with M Types Type 3 Throat Infection Rheumatic Fever Type 12 Skin Infections Nephritis The M protein appears to be the major virulence factor of the Group A strep

Other Virulence Factors Hyaluronic acid capsule Virtually identical to the hyaluronic acid in human connective tissue Thus the cell is not seen as foreign and is not phagocytized

Other Virulence Factors M protein Antiphagocytic by preventing C’ binding

Other Virulence Factors Peptidoglycan plus the Group A polysaccharide Produce lesions in rabbits resembling the joint and skin lesions seen in patients with rheumatic disease

Other Virulence Factors Lipoteichoic acid Lipoteichoic acid promotes attachment to cells Protoplast membrane The cell's Protoplast membrane antigens cross react with heart tissues and may be involved in the heart tissue destruction seen in rheumatic fever

Other Virulence Factors Streptolysin O A hemolysin that is oxygen-labile May have cardiotoxic activity Streptolysin S A hemolysin that is oxygen-stabile Leukotoxic

Other Virulence Factors Hyaluronidase Probably breaks down the ground substance in connective tissue allowing the organisms to spread

Other Virulence Factors Streptokinase Converts serum plasminogen to plasmin, an enzyme that digests fibrin By dissolving fibrin clots, the organism can spread

Other Virulence Factors DNAase / Streptodornase Hydrolyzes DNA, which is found in large amounts in purulent exudates as a result of lysis of the phagocytic cells The lysis leads to decreased viscosity of the exudate and enhanced spread of organisms

Other Virulence Factors NADase and various Proteases Contribute to spreading

Other Virulence Factors Erythrogenic Toxin Some strains contain a phage that Allows the organism to produce a toxin called the Erythrogenic Toxin The Erythrogenic Toxin is responsible for the rash in Scarlet Fever

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"SCARLET" SCARLET  FEVER STREP  THROAT due to Group A Beta Streptococci

Erythrogenic Toxin SCARLET FEVER Strep Throat Infection + Toxemia Erythrogenic toxin causes Toxemia Erythrogenic toxin causes Skin Rash

Erythrogenic Toxin Not all strains of GpA strep produce the toxin Individuals who have had scarlet fever are immune to the toxin but not to the bacteria So they can still get strep throat

Erythrogenic Toxin Infection with Toxin – strain or Toxin + strain in immune individual Only strep throat There is no skin rash

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Pathogenesis of Streptococcal Pharyngitis

"Each species or sometimes genus..." Each species or sometimes genus of an organism produces disease in its own way But many aspects are the same or similar With the streptococci, the development of the local lesion can be divided into 3 stages: attachment, spreading, and recovery

Attachment Requires ~ 2x106 organisms Mediated by Lipoteichoic acid M protein C polysaccharide Inflammatory response takes place: fluid exudate (edema) Polymorphonuclear (PMN) cells

Spreading M protein prevents phagocytosis DNAses, proteases, and streptokinases hydrolyze PMN exudates (released when the PMNs are killed) Produce Hyaluronidase - breaks down ground substance

Recovery Normally occurs when antibodies to M protein are produced However, ~3% of patients develop Rheumatic fever (heart valve damage)

Diagnosis of Streptococcal Pharyngitis Based first on clinical symptoms and then on the appropriate laboratory tests

Laboratory Tests Throat swab Culture for Group A b-strep Determine sensitivity to Bacitracin

"Serologic tests on patient’s serum" Serologic tests on patient’s serum Several tests can be done on the serum of a person suspected of having a group A strep infection - the most common are Antistreptolysin O test - most often done Antihyaluronidase test

Serologic Tests Antistreptolysin O (ASO) Test The titer of antibodies to streptolysin O is measured If higher than a standard, it indicates that the person has had a recent Group A infection

Strep Throat Epidemiology Usually spread by aerosol droplets from someone with a sore throat or someone who is a carrier Carrier = infected but not symptomatic

Treatment Penicillin = antibiotic of choice Erythromycin = if allergic Symptoms go away in 24 hours But must continue treatment for full 10 days to prevent Rheumatic Fever

Streptococcus pneumoniae Pneumococcus Pneumococci

Streptococcus pneumonia One of the most frequent causes of death due to an infectious disease Gram-positive diplococci Catalase negative Alpha hemolytic under O2 conditions and Beta hemolytic under AnO2 conditions

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Serology Polysaccharide Capsule 80 Serologically different types

Serology “C” substance in cell wall Reacts with a protein produced during acute inflammatory diseases This protein = C-Reactive Protein

Virulence Factors Capsular polysaccharides inhibit phagocytosis unless cells are coated with antibodies Beta hemolysin (AnO2 produced) is leucocidal (Toxin?) may exist since people die with symptoms resembling a toxemia

Oral Streptococci

Oral Streptococci There are many species Most are alpha hemolytic Some are gamma hemolytic The following are a few of the more important ones

Streptococcus salivarius Gamma hemolytic Normally on tongue Large numbers are shed into the saliva and this organism is the major one found in the saliva

"(Sucrose is a disaccharide..." (Sucrose is a disaccharide composed of glucose and fructose) Produces levan (poly-fructose) from the fructose moiety of sucrose Produces energy from the glucose moiety of sucrose

Sugar names Sugar Sugar Polymer Sugar Polymer  Type Name A Name A Name B Name B 6 carbon glucose glucan dextrose dextran 5 carbon fructose fructan levulose levan

Sugar names Sugar Sugar Polymer Sugar Polymer  Type Name A Name A Name B Name B 6 carbon glucose glucan dextrose dextran 5 carbon fructose fructan levulose levan

Streptococcus sanguis Normal resident of tooth surface (Plaque) Considered normal, healthy flora Polymerizes glucose from sucrose into soluble dextrans

Streptococcus mitis Normal resident of tongue and oral mucosa Produces a soluble dextran and doesn’t play a role in pathology

Streptococcus mutans group There are 7 species in this group, 5 are human species All were originally classified as the single organism Streptococcus mutans Produce an insoluble dextran from sucrose Involved in dental caries

Treatment Virtually all members of the genus Streptococcus are sensitive to Penicillin and Erythromycin The exception to this is the emergence of Penicillin Resistant Streptococcus pneumoniae

Enterococcus

Enterococcus Gram positive streptococci in a separate genus Some are Lancefield type D Many are beta hemolytic Originally isolated from intestine (entero) Often found in oral soft tissue infections

Virulence Factors Hyaluronidase Hemolysin Other enzymes and toxins Bacteriocin (antibacterial proteins)

Treatment Difficult to treat because they often have a very high resistance to penicillin Vancomycin was the antibiotic used for Penicillin Resistant Enterococci (PRE) but now Vancomycin Resistant Enterococci (VRE) are emerging

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