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Staphylococcus PowerPoint Presentation

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Description : Check out this medical presentation on Staphylococcal Scalded Skin Syndrome, which is titled "Staphylococcus", to know about Staphylococcus, a group of bacteria (microbe or germ) that can cause a number of infectious diseases in various tissues of the body.

Tags : Staphylococcal Scalded Skin Syndrome, Staphylococcus, bacteria

Published on : Jul 05, 2021 | Views : 3858 | Downloads : 5

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Slide 1-

Staphylococcus Dr. Jyotsna Agarwal Professor, Dept. of Microbiology K G Medical University, Lucknow
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Family: Micrococcaceae Genus: Staphylococcus- derived from Greek “stapyle” (bunch of grapes) Include major human pathogen and skin commensals Micrococcus- skin commensal
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Staphylococcus: General Characteristics Gram-positive spherical cells (0.5-1.5 mm) in singles, pairs, and clusters Appear as “bunches of grapes” Gram-stained smear of staphylococci from colony
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Non motile Non–spore-forming Nonencapsulated Catalase-producing Oxidase: negative Glucose fermenters Primarily aerobic, some facultatively anaerobic Staphylococcus: General Characteristics
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Approximately 33 species ~15 species associated with humans Staphylococcus divided into coagulase positive & coagulase negative categories Inhibited by high bile salt concentration Some are ß-hemolytic Colony morphology: buttery looking, cream or white colored Staphylococcus: General Characteristics
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S. aureus S. intermedius S. hyicus S. delphini S. schleiferi Veterinary pathogens Animal-associated species Human pathogens Coagulase Positive Staphylococci
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Primary pathogen Habitat: anterior nares (carriers) Colonization: axilla, perineum, pharynx Produce superficial to systemic infections Mode of transmission: Pus formation Staphylococcus aureus
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Natural history of disease Usual sites - skin, nasopharynx, perineum Breach in mucosal barriers - can enter underlying tissue Characteristic abscesses with Pus Bacteria liberates toxins-
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DISEASES Due to direct effect of organism Local - skin Deep abscesses Systemic infections Toxin mediated Food poisoning toxic shock syndrome Scalded skin syndrome
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Virulence Factors of S. aureus Pathogen Factors ENZYMES Catalase (counters host defences) Coagulase Hyaluronidase Lipases B lactasamase (antibiotic resistance) TOXINS- enterotoxin, TSST, epidermolytic toxin
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SKIN LESIONS- superficial Boils Styes Furuncles Carbancles Wound infections
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DEEP ABSCESSSES Direct / by blood Can be single / multiple Eg. - Breast abscess kidney, brain, Osteomyelitis, septic arthritis
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TOXIN MEDIATED DISEASES 1. Staphylococcal food poisoning Due to production of enterotoxins preformed toxin, heat stable short incubation period Milk & milk products
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2. Toxic shock syndrome High fever, diarrhoea, shock and erythematous skin rash which desquamate Mediated via ‘toxic shock syndrome toxin’ 10% mortality rate
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3. Scalded skin syndrome Disease of young children Mediated through minor Staphylococcal infection by ‘epidermolytic toxin’ producing strains Good prognosis
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Virulence Factors: Extracellular enzymes Cytolytic Toxins Alpha hemolysin: lyses rbcs, damages plts, causes severe tissue damage ß hemolysin: acts on sphingomyelin in the plasma membrane of rbcs
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Virulence Factors: Extracellular enzymes Hyaluronidase: Hydrolyzes hyaluronic acid in connective tissue allowing spread of infection Staphylokinase: fibrinolysin which allows spread of infection Coagulase: virulence marker Lipase: allows colonization
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Beta-lactamase or Penicillinase: confers resistance DNase: degrades DNA Protein A: in cell wall, it binds to Fc part of IgG toblock phagocytosis Virulence Factors: Extracellular enzymes
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Coagulase-Negative Staphylococci Habitat: skin and mucous membranes Common human isolates S. epidermidis S. saprophyticus
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Coagulase-Negative Staphylococci: Staphylococcus epidermidis Virulence factor: “slime” Mode of infection: colonization of medical implants Infections are acquired nosocomially Serious infections among immunosuppressed patients or neonates may occur
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Habitat: skin and mucosal membranes of the genitourinary tract Common cause of urinary tract infections in young, sexually active females Coagulase-Negative Staphylococci: Staphylococcus saprophyticus
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Microscopic Examination Gram-positive cocci pairs and clusters Numerous polymorphonuclear cells (PMNs) Laboratory Diagnosis: Direct Smear Examination
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Laboratory Diagnosis: Cultural Characteristics Colony morphology Smooth, butyrous, white to yellow, creamy Grow well in 18-24 hours S. aureus may produce hemolysis on blood agar S. aureus
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Principle: tests for enzyme catalase Drop H2O2 onto smear Bubbling = POS (Staph) No bubbling = Streptococci Identification Tests: Catalase
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Cell-bound “clumping factor” converts fibrinogen to fibrin which precipitates on cell causing agglutination Extracellular enzyme “free coagulase” Identification Tests: Coagulase Test Two methods Slide test: screens for “clumping factor” Tube test
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Novobiocin Susceptibility Test Test to differentiate coagulase-negative staphylococci from S.saprophyticus from urine samples S. saprophyticus is resistant (top)
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Beta-lactam group of antibiotics- (penicillins, cloxacillins, ampicillin, amoxycillin) Beta-lactamase producers treatment of choice Amoxyclavulinic acid or ampicillinn sulbactam combo or methicillin/ oxacillin For methicillin -resistant S. aureus (MRSA) treatment of choice- Vancomycin Antimicrobial Susceptibility
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Summary Characters of Staphylococcus aureus Enzymes / Toxins Infections / Diseases Laboratory diagnosis Treatment / Abx resistance