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PYOGENIC COCCI Streptococcus Enterococcus Staphylococcus Neisseria

INTRODUCTION The staphylococci are Gram-positive coccal bacteria that divide in different planes They tend to not separate after division and thus they form clusters similar to grapes “Staphylo” means “grape-like” in  Greek

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PHYSIOLOGY Staphylococci Streptococci Cocci Bunches Chains Catalase Positive Negative Salt Tolerant (7.5%) Sensitive Infection Localized Spreading Antibiotics Resistant Most sensitive   to penicillin

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"The significance of the salt..." The significance of the salt tolerance is that 1) they can grow on the skin, which can get salty on a hot day, and 2) they can be selectively isolated on culture media that contains a high salt concentration

"This is useful if we..." This is useful if we specifically want to know if they are present in a wound or food material that may contain many other kinds of bacteria

"Staphylococci cause a type of..." Staphylococci cause a type of food poisoning Being able to specifically culture these organisms from suspected bad food can result in a faster diagnosis

"A medium that selects out..." A medium that selects out certain bacteria from a mixed population is referred to as a selective medium It may be possible in the future to use a selective medium to quickly determine the presence of specific periodontopathic organisms in a periodontal pocket

Comparison of Human Staphylococci S. aureus S. epidermidis Colonies Golden White Found Nose Skin (epidermis) Mouth Mouth Coagulase Positive Negative Mannitol Ferments Does not ferment Clump. fact. + - Pathogenic + -

"The 2 species can be..." The 2 species can be distinguished by tests for coagulase production Coagulase is an enzyme that coagulates plasma S. aureus is always coagulase positive S. epidermidis is always coagulase negative This is the main test to separate these two

"S." S. aureus also usually ferments mannitol and S. epidermidis usually does not

"This characteristic has been usefully..." This characteristic has been usefully employed by incorporating this sugar and a pH indicator in a plate of medium containing 7.5% salt Mannitol fermenting colonies are S. aureus

"We call a medium that..." We call a medium that differentiates between 2 or more kinds of organisms growing on it a differential medium Since the mannitol-salt agar was also a selective medium it is a selective and differential medium

"S." S. aureus also has in its cell wall a component that will agglutinate in the presence of plasma It is called Clumping Factor It has been shown to help the staphylococci to attach to human cells

BACTERIOPHAGE TYPING S. aureus is susceptible to a number of phages The phage are numbered and any one strain of S. aureus is susceptible to only a few of the numbered set of phage

"We thus get what are..." We thus get what are called phage types for strains of S. aureus such as type 42D/42E/47/52 meaning the strain is lysed by phages 42D, 42E, 47, and 52

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"As is the case with..." As is the case with some animal cell viruses, the bacterial viruses don't always kill the cell It is then said that they carry a prophage

"One significance of the prophage..." One significance of the prophage is that it contributes its own DNA to that of the bacterial cell Thus it usually adds something such as the ability to produce an enzyme or toxin

Somatic Antigens Capsules Some strains produce a thin polysaccharide capsule Sometimes it is only a slime layer May play a role in adherence to catheters and other materials

Somatic Antigens Teichoic Acids Teichoic acids Present in the cell wall May help the staphylococci attach to surfaces

Somatic Antigens Protein A The surface of many strains of staph contain a protein called Protein A Binds to Fc Region of IgG Can lead to systemic and local anaphylactic reactions Can lead to Arthus reactions Can block phagocytosis

Somatic Antigens Clumping Factor Clumping Factor Present in the cell wall Helps cells agglutinate in the presence of plasma Helps staphylococci attach to human cells

VIRULENCE FACTORS The staphylococci produce perhaps the largest number of virulence factors of any known organism Those that are known are shown in the next table

Virulence Factors of Staphylococci Factor Activity Alpha hemolysin Hemolytic, Lethal, Dermonecrotic, Leukocidal Beta hemolysin Hemolytic, a Phospholipase Gamma hemolysin Hemolytic, Lethal Delta hemolysin Hemolytic, Leukocidal Epsilon hemolysin Hemolytic, Leukocidal

Virulence Factors of Staphylococci Factor Activity Coagulase Coagulates plasma Egg Yolk Factor Lipase and Phospholipase Enterotoxin Food poisoning Esterase Hydrolyzes esters (cell walls)

Virulence Factors of Staphylococci Factor Activity Exfoliative Toxin Toxin Shock Syndrome Toxin 1 (causes exfoliation Glucuronidase Hydrolyzes glucuronic acid (tissues) Hyaluronidase Hydrolyzes hyaluronic acid (tissues

Virulence Factors of Staphylococci Factor Activity Leukocidin Leukocidal Leukocyte Cytotaxin Attracts leukocytes Lipase Hydrolyzes lipids to fatty acids (histotoxic) Lysozyme Lyses cells of Micrococcus lysodiekticus

Virulence Factors of Staphylococci Factor Activity DNAse Hydrolyzes DNA, helps spread RNase Hydrolyzes RNA, helps spread Penicillinase Hydrolyzes penicillin Phosphatase Acts on phosphates (tissue, tooth)

Virulence Factors of Staphylococci Factor Activity Proteases Casein, Collagen, Elastin, Gelatin, Hemoglobin Staphylokinase Breaks down fibrin (Fibrinolysin) clots (spreading) Sulfatase Hydrolyzes sulfates Urease Hydrolyzes urea

Virulence Factors of Staphylococci Factor Activity Succinic Oxidase Factor Disrupts cellular metabolism

"With many infectious agents," With many infectious agents, one specific toxin is responsible for the pathology With staphylococci no one specific toxin is responsible for the pathology Thus we can’t immunize against Staph infections

Staphylococcus  Pathogenesis Staphylococci generally cause localized infections with much pus They may also invade the bloodstream and cause a septicemia

Staphylococcus Pathogenesis Most common local infection = boil or furuncle Fibrin forms around the abscess Staphylokinase (fibrinolysin) or hyaluronidase may then allow the infection to spread

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Staphylococcus Treatment Penicillin only effective for 10 - 20% Methicillin is effective but now we have Methicillin Resistant Staphylococcus aureus (MRSA) emerging

"Vancomycin is still very effective..." Vancomycin is still very effective but recent isolates show intermediate levels of resistance giving rise to the term VISA (Vancomycin Intermediate Staphylococcus aureus) And now also emerging are Vancomycin Resistant Staphylococcus aureus (VRSA)

Staphylococcus Antibiotics Must do antibiotic sensitivities on ALL staphylococcal infections With staph infections, must establish adequate drainage

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