Downloaded 584 times
Uploaded byRiyaz Sheriff
Staphylococcus
The document provides an in-depth overview of the Staphylococcus genus, highlighting its characteristics, pathogenicity, and the related infections caused by various species such as Staphylococcus aureus and Staphylococcus epidermidis. It discusses their culture characteristics, resistance to antibiotics, virulence factors, and the clinical significance of staphylococcal diseases ranging from skin infections to systemic conditions. Additionally, the document addresses the methods of laboratory diagnosis and treatment options for staphylococcal infections, emphasizing the rise of antibiotic resistance in hospital strains.
More Related Content
Staphylococcus
- 1.
- 2. Staphylococcus • Ubiquitous • Grampositive • Cocci • Staphyle - Bunch of grapes • Kokkos - Berry • Discovered by Von Recklinghausen • Named by Sir Alexander Ogston
- 3. Staphylococcus • Pyogenic infections •Pigment production not associated with virulence – Golden yellow colonies Staphylococccus aureus – White colonies Staphylococcus epidermidis – White colonies Staphylococcus albus – Lemon yellow colonies Staphylococcus citreus
- 4.
- 6.
- 7.
- 8.
- 9.
- 11.
- 12.
- 13. Generally! • Non motile •Non sporing • Young cultures may have capsules • Stain with aniline dyes • Uniformly gram positive • L forms may be seen
- 14. Current classification • 32species • 15 sub species • Coagulase positive Staphylococcus aureus • Coagulase negative – Staph. epidermidis – Staph hemolyticus – Staph saprophyticus – Staph hominis – Staph capitis Commensal flora
- 15. Staphylococcus aureus • Grampositive cocci • Arranged in grape like clusters • Cluster formation is d/t division in 3 planes and daughter cells remain in close proximity • May appear in singles, pairs or short chains • Some bacteria may have capsules
- 16. Culture characteristics • Growon ordinary media • Temp 10-42°C. optimum is 37°C • pH range 7.4 – 7.6 • Aerobes • Facultative anerobes • Nutrient agar – Large, Circular, Smooth, Shiny, Opaque & easily emulsifiable colonies – Yellow pigment which does not diffuse into medium – Pigment is carotene like lipoprotein – Pigment production best at 22°C or when glycerol monoacetate / milk is incorporated into medium
- 17. culture characteristics (Cont'd) •Nutrient slope – Oil paint appearance • Blood agar – Marked hemolysis on sheep blood agar – 20-25% Co2 – Rabbit / Sheep blood • Mac Conkey agar – Pink colonies due to lactose fermentation • Liquid media – Uniform turbidity • Selective medium – Salt milk agar – Salt broth – Ludlam’s medium ( Lithium chloride, Tellurite)
- 22.
- 23. Biochemical reactions • Catalase Positive • Indole Negative • MR Positive • VP Positive • Urease Positive • Nitrate reduction Positive • Mannitol fermentation Positive • Phosphatase production Positive
- 24.
- 25.
- 26.
- 27.
- 28. Resistance • Withstand upto60°C, die at 62°C • Can grow upto 45°C • Can grow in medium containing 10-15% NaCl • Resist 1% phenol for 15mins • 1% mercuric perchloride kills staphylococci in 10mins • Aniline dyes lethal – Crystal violet 1:5,00,000 concentration – Brilliant green 1: 1,00,00,000 concentration • Fatty acids inhibit growth of staphylococci
- 29. Penicillins & Staphylococci •Sensitive in pre-antibiotic era • Few strains evolved !! • Pencillinase • Inducible enzyme • Plasmid mediated : Transduction / conjugation • 4 types A-D • Newer antibiotic resistant bacteria spread far and wide …. • Hospital strains belong to group A
- 30. Resistance to drugs- Penicillin • Changes in bacterial surface receptors (PBP2a) • Avoids binding of antibiotic to cell wall • Development of tolerance to penicillin • Also includes beta-lactamase resistance penicillins like Methicillin & Cloxacillins : MRSA • Plasmid borne resistance to Erythromycin, Tetracyclines, Aminoglycosides etc • Cause hospital infections & epidemics EMRSA • Methicillin Oxacillin Cefoxitin
- 31. Pathogenicity • Infections – Coccienter via damaged skin/ mucousa/tissue – Colonise locally – Evade host mechanism – Tissue damage • Intoxications – Disease caused by bacterial toxins – In vitro/ in vivo
- 32. virulence • Cell associatedpolymers – Cell wall polysaccharide peptidoglycan • Rigidity and structural integrity • Activates complement • Induces release of inflammatory cytokines – Techoic acid • Antigenic component • Adhesion • Protect from complement mediated opsonisation – Capsular polysacchride • Inhibit opsonization
- 33. virulence • Cell surfaceproteins – Protein A • Chemotactic • Anti – phagocytic • Anti-Complementary • Induces platelet damage & hypersensitivity – Clumping factor – Bound coagulase – slide coagulase test • Extracellular enzymes – Coagulase clots human/rabbit plasma – Coagulase enzyme + CRF coagulum (fibrinogen to fibrin clot) – free coagulase- Tube coagulase test
- 34.
- 35.
- 36. virulence – Lipases – Hyaluronidase –Nucleases – Protein receptors
- 37. Toxins • Cytolytic toxins –Alpha Hemolysin – Beta Hemolysin – Gamma Hemolysin – Delta Hemolysin – Leucocidin - (Panton –Valentine toxin or PVL) • Enterotoxin – Staphylococcal food poisoning – Nausea , Diarrhoea , vomiting after 2-6hrs of ingestion of contaminated food – Heat stable toxin : 100°C for 10-40mins – Common food products : Meat, Fish, Milk or Milk products • A, B,C1,C2,C3,D,E & H
- 38. Summation of Factors associatedwith virulence Hemolysis Gelatin liquefaction Lipolytic activity Production of urease Production of phosphatase Coagulase formation Mannitol fermentation
- 39. Toxin mediated syndromes •TSST & SSSS toxins are called superantigens • Potent activators of T-Lymphocytes • Stimulate wide variety of T Lymphocyte regardless of antigen specificity • Excessive improper immune response, Massive release of cytokines , TNF & INF Ɣ
- 40. Toxin mediated syndromes •Toxic Shock Syndrome Toxin TSST – Multisystem disease – Older days : Tampon usage – Follows infection of mucosa / site by toxin producing strains • Fever • Hypotension • Myalgia • Vomiting • Diarrhoea • Mucousal hyperemia • Rash – TSST 1 Antibody is seen in patients recovering from TSST
- 41. Toxin mediated syndromes •Exfoliative (epidermolytic) toxin SSSS • Staphylococcal Scalded Skin Syndrome • Exfoliative disease • Outer layer of epidermis gets separated from underlying tissue • Severe form of SSSS in new born Ritter’s disease • In older patients Toxic epidermal Necrolysis • Milder forms – Phemphigus neonatorum – Bullous impetigo
- 43. Staphylococcal diseases • Skinand soft tissue infections – Folliculitis – Furancle – Boils – Abscess – Wound infection – Carbuncle – Impetigo – Paronychia – Cellulitis • Musculoskeletal – Osteomyelitis – Arthritis – Bursitis – Pyomyositis
- 45. Staphylococcal diseases • Respiratory –Tonsillitis – Pharyngitis – Sinusitis – Otitis – Bronchopneumonia – Lung abscess – Empyema • Central nervous system – Abscess – Meningitis – Intra cranial thrombophlebitis
- 46. Staphylococcal diseases • Endovascular –Bacteremia – Septicemia – Pyemia – Endocarditis • Urinary tract infection – Uncommon – Present with instrumentation – Diabetes – Significant when associated with Bacteremia
- 47. Bacteriophage typing • Strainto be typed is inoculated as lawn culture on nutrient agar • After drying phages are applied on marked squares in a fixed dose • After overnight incubation cultures will be observed to be lysed by some phages • Phage type of strain is expressed by the phages which lyse the bacteria • Phage typing is important in epidemiological studies.
- 48.
- 49. Epidemiology • Primarily colonizeskin • Respiratory & superficial infections disseminate into environment • 10-30% carry staphylococci in nose • 10 % have staphylococcal carriage in hair& perineum • 5-10% carriage is seen in vagina • Transmission of infection can be by contact, direct or through fomites, by dust or by airborne droplets • Nosocomial cross infection is very important resistant strains
- 50. LAB DIAGNOSIS • SPECIMENCOLLECTION • Microscopy • Culture • Identification – Catalase test – Coagulase test • Slide • Tube – Antibiotic sensitivity – Phage typing
- 51. Treatment • Penicillin isdrug of choice • Methicillin/ cloxacillin in penicillin resistant cases • For MRSA Vancomycin • Vancomycin, Teicoplanin resistant strains have appeared • Superficial infection local application with bacitracin, Chlorhexidine or Mupirocin • Very resistant cases & chronic resistant carriers Rifampicin along with oral antibiotic
- 52. Coagulase negative Staphylococcci • Staphylococcusepidermidis – Commensal on skin – Can cause cystitis – Stitch abscess, artificial heart valves, shunts, intra vascular catheters& prosthetic appliances • Staphylococcus hemolyticus • Staphylococcus saprophyticus – Uti in young women