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staphylococcus aureus from medical bacteriology
- 1. VIVEKANANDHA ARTS AND SCIENCECOLLEGE FOR WOMEN . VEERACHIPALAYAM-637303, SANKAGIRI, SALEM DT, TAMILNADU, INDIA AFFILIATED TO PERIYAR UNIVERSITY, SALEM . DEPARTMENT OF MICROBIOLOGY . SUBJECT : MEDICAL BACTERIOLOGY TITLE : STAPHYLOCOCCUS .AUREUS SUBJECT INCHARGE: Dr.R.MYTHILI RAVICHANDRAN, ASSISTANT PROFESSOR, HEAD OF THE DEPARTMENT, DEPARTMENT OF MICROBIOLOGY. SUBMITTED BY : Ms . M . ARTHI, lll. Bsc., MICROBIOLOGY, DEPARTMENT OF MICROBIOLOGY.
- 2. STAPHYLOCOCCUS AUREUS SYNOPSIS : •Introduction • Morphology • History • Virulence factors • Pathogenesis • Clinical syndrome • Culture characteristics • Lab diagnosis • Mode of transmission • Treatment • Prevention • reference
- 3. INTRODUCTION STAPHYLOCOCCUS • Gram positivecocci, belongs to Family Micrococcaceae. • Aerobic , some facultative anaerobes. • Arrangement in clusters ( like grapes ), pairs or tetrads, • Catalase positive. • S. aureus is the most important human pathogen, others human pathogens are CONS (Coagulase negative Staphylococci) which include S. saprophyticus, S. epidermidis, S. hominis etc. • Staphylococcus are capable of acquiring resistance to antibiotics, • Can cause serious clinical and epidemiological problems.
- 4. Staphylococcus aureus Morphology • Nonmotile and non spore forming •Gram positive cocci •Size is 0.7 to 1.2mm in diameter •Irregular clusters that resemble cluster of grapes.
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- 6. HISTORY • Robert Koch(1878)- first to see staphylococci in pus specimen • Louis Pasteur (1880)- first to cultivate in liquid medium • Sir Alexander Ongston (1881)- named the bacteria as “ Staphylococcus”
- 7. VIRULENCE FACTORS CELL WALL ASSOCIATED STRUCTURES •Peptidoglycan • Capsule • Protein A • Clumping factor (bound Coagulase) EXTRA CELLULAR TOXINS • Haemolysin • Leukocidin • Enterotoxin • TSST • Exfoliatin toxin COAGULASE • Staphylokinase • DNAase • Phosphatase • Lipase • Phospholipase • Hyaluronidase • Serokinase • Protease
- 8. PATHOGENESIS • Cause localisedlesions • First multiply in tissues, produce toxins and stimulate inflammation. • Adhere to damaged skin. • Evade defense mechanism of host. • Cause tissue damage and from abscesses, produce extra-cellular enzymes and exotoxins. Host immunity: • No life long immunity. • Repeated infections occur in susceptible host.
- 9. CLINICAL SYNDROME • 2types: inflammatory and toxin mediated staphylococcal disease. INFLAMMATORY DISEASES: • Impetigo, folliculitis, furuncle, carbuncle, surgical wound infection, postpartum breast infection. • Bacterimia (bacteria found in blood) and septicemia ( multiplication of bacteria produce toxins cause high rate of fever) • Endocarditis. • Osteomyelitis and arthritis. • Deep seated abscess in any organ after bacterimia.
- 11. Toxin mediated staphylococcaldisease: 1. Staphylococcal food poisoning: • Caused by Enterotoxin. • Milk, milk products, meat fish when kept at room temperature after cooking, contaminants multiply and produce toxins. • Virulent when release of interoleukins( L-1and L-2). • Sudden symptoms after 2-6 hour of ingestion • Nausea, vomiting, abdominal cramps, watery or bloody diarrhea.
- 12. 2. Staphylococcal toxicshock syndrome (TSST): • Caused by toxin shock syndrome toxin. • Release of large amount of interleukin lL-1 and lL-2. • Life threatening condition. • Fever, vomiting, hypertension, myalgia( muscle pain) mucosal hyperemia, erythematous rash ( redness due to increased blood flow). 3. Staphylococcal scaled skin syndrome (SSSS): • Caused by exfoliative toxin • Common in infants and children • Outer layer of skin of epidermis is separated from underlying tissue. • Appears as extensive bullae ( rupture and leave behind red, tender skin ).
- 13. STAPHYLOCOCCUS AUREUS Culture characteristics: •Growreadily on ordinary culture media. •Optimum temperature -37°C •Optimum pH – 7.4 – 7.6 •Aerobes and facultative anaerobes.
- 14. LAB DIAGNOSIS: 1. Specimens: •Pus– from wound or abscess or burns •Nasal Swab – from suspected carrier •Food – to diagnose staphylococcal intoxication •Blood- to diagnose endocarditis and bacteremia •Sputum- to diagnose lower respiratory tract infection
- 15. 2. Gram staining: Thediagnosis of staphylococcus aureus is suggested by the finding of gram positive bacteria in clumps in the sample. 3. Culture: on nutrient agar, • Golden yellow and opaque colonies with smooth glistening surface, 1-2mm in diameter
- 16. On blood agar: •Golden yellow colonies, surrounded by a clear zone of hemolysis ( beta hemolysis), esp. When incubated in sheep blood agar in atmosphere of 20% CO2 • On MacConkey agar: • Smaller colonies than those on NA (0.1-0.5mm) and are pink coloured due to lactose fermentation
- 17. On Mannitol salaryagar: S.aureus ferments mannitol and appear as yellow colonies • MSA is a useful selective medium for recovering S. aureus from faecal specimen, when investigating food poisoning
- 18. BIOCHEMICAL PROPERTIES • Indoletest – negative • MR test – positive • VP test – positive • Urease test – positive • Phosphatase – positive • DNAase test – positive • Coagulase test – positive • Hydrolyse gelatin • Reduces nitrate to nitrite
- 19. MODE OF TRANSMISSION •Person with lesions •Airborne droplets •Asymptomatic carrier •Cross infection
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- 22. REFERENCE • Ananthanarayan andPaniker’s text book of Microbiology 12 th edition • Google images
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