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streptococci
 

streptococci

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this is a series of lectures on microbiology, useful for undergraduate and post graduate medical and paramedical students..lecture on streptococci

this is a series of lectures on microbiology, useful for undergraduate and post graduate medical and paramedical students..lecture on streptococci

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    streptococci streptococci Presentation Transcript

    • STREPTOCOCCUS 1
    • Strepto-cocci 2
    •  Commensals or Parasites of man & animals  or  Saprophytes of decaying matter 3
    • Genus Streptococcus Gram-Positive Cocci in Pairs or Chains v/s Staph – gram positive cocci in clusters (grape like) 4
    • Gram-Positive Streptococcus 5
    •  Gram positive cocci in clusters 6
    • Classification  On the basis of their growth characteristics on blood agar  Alpha hemolytic  Beta hemolytic  Gamma hemolytic 7
    • Example – Streptococcus viridans (Viridans = green) Streptococcus pneumoniae 8
    • 9
    • Example – enterococcus group 10
    • 11
    • 12
    • Beta hemolytic streptococci Lancefield grouping  Group A to Group V without I and J  Divided according to differences in Cell wall carbohydrate antigen  Out of all these, those of Group A known as streptococcus pyogenes produce majority of human infections  Group B are known as S agalactiae 13
    • Group A beta hemolytic streptococci / strep pyogenes  These are further subdivided according to sell surface M, T and R antigens  Griffith typing 14
    • 15
    • Streptococcus Pyogenes (Group A beta hemolytic) 16
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 17
    • Morphology  Cocci in long chains 18
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 19
    • Growth characteristics  Facultative anaerobe, grows best in presence of 10% CO2  Grows on enriched media only  Beta hemolysis around colonies on blood agar 20
    • 21
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 22
    • Biochemical reactions  Ferment sugars – produce acid , no gas  Catalase negative  Catalase helps to differentiate staphylococci from streptococci 23
    • Catalase test  Add hydrogen peroxide to culture material 24
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 25
    • Resistance  Most are still susceptible to penicillin and erythromycin 26
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 27
    • Pathogenicity and virulence  Antigenic structure  Antigens on surface of strep cross react with body proteins   Capsular hyaluronic acid – human joints – autoimmune arthritis Carbohydrate antigen – cardiac valves – rheumatic heart disease  Toxins  Enzymes      Streptolysin O – ASO titre for diagnosis Streptolysin S – for hemolysis around colonies Streptokinase – lysis of clots – given iv for treatment of MI DNA ase – Anti DNAase is useful for diagnosis of S. pyogenes skin infection Hyaluronidase – breaks down tissues – helps in spread of strep infection 28
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 29
    • Epidemiology  Source – human upper respiratory tract – throat, pharynx, nose  Transmission – direct contact, fomites 30
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 31
    • Diseases caused  Pus producing (suppurative) Respiratory infections  Skin and soft tissue infections  Genital infections   Non suppurative Acute rheumatic fever  Rheumatic heart disease  Acute glomerulonephritis (kidney)  32
    • Respiratory infections  Tonsillitis  Pharyngitis 33
    •  tonsillitis 34
    •  pharyngitis 35
    • Skin and soft tissue infections  Skin Erysipelas – involves lymphatics – older pts  Impetigo – young children  Pyoderma   Soft tissue Cellulitis  Necrotising fascitis  36
    • Erysipelas 37
    • Impetigo 38
    • Pyoderma 39
    • Cellulitis 40
    • Necrotising fascitis flesh eating bacteria (anaerobes) 41
    • Non suppurative complications After 1-3 weeks of primary infection Due to cross reactivity 42
    • Acute rheumatic fever  Follows streptococcal sore throat 43
    • Acute glomerulonephritis  Cross reaction between streptococci and kidney tissues 44
    • Rheumatic heart disease 45
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 46
    • Suppurative infections  Examination of pus/throat swabs  Microscopy, staining and culture  Gram stain  Blood agar 47
    • Non suppurative infections  Demonstration of antibodies  Like ASO and anti DNA ase B 48
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 49
    • Treatment  Penicillin  Erythromycin  Drugs have no effect if non suppurative complications have developed  Prophylaxis – can prevent rheumatic fever, not glomerulonephritis 50
    • OTHER STREPTOCOCCI BETA HEMOLYTIC - GROUP B AND GROUP D ALPHA HEMOLYTIC (VIRIDANS GROUP)– STREPTOCOCCUS PNEUMONIAE 51
    • Group B Streptococcus Streptococcus agalactiae 52
    • Group B Streptococcus S. agalactiae 1. Infect newborns 2. Infection acquired through maternal vagina during birth 3. Presents as meningitis, pneumonia or septicemia 53
    • Diagnostic Laboratory Tests   CAMP factor positive Hippurase positive 54
    • CAMP (Christie, atkins, munchpeterson) Factor Test aureus S. Group B Streptococcus (Spingomyelinase C) (CAMP Factor) Group A Streptococcus Enhanced Zone of Hemolysis 55
    • Hippurase NEG Streptococcus agalactiae not added 56
    • Grp B Streptococci Hippurase POS 57
    • Viridans group Streptococcus pneumoniae • Commonly referred to as pneumococcus 58
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 59
    •  Lancet shaped (one end broad, other pointed)  Capsulated  Diplococci 60
    • S. pneumoniae: lancet-shaped diplococcus 61
    • S. pneumoniae • Diplococcus 62
    • Capsular stain 63
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 64
    • Growth characteristics  Alpha hemolysis on blood agar  On further incubation, the colonies become flat with raised edges and central elevation resembling carrom coins 65
    • Example – Streptococcus viridans (Viridans = green) Streptococcus pneumoniae 66
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 67
    • Biochemical reactions  Hiss serum water – fermentation of inulin  Bile solubility 68
    • Inulin fermentation 69
    • 70
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 71
    • Resistance  Pneumococcus is sensitive to optochin – used for typing  Resistance to penicillin – third generation cephalosporin like ceftriaxone  May be resistant to third gen ceph also 72
    • 73
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 74
    • Pathogenicity and virulence  Capsule  Toxins – pneumolysin  C reactive protein 75
    • Capsule 76
    • Pneumolysin  Membrane damaging toxin  Cytotoxic activity 77
    • C reactive protein  Abnormal immunoglobulin against C protein of S. pneumoniae appears in serum of patients  Also seen in acute phase of infections and inflammations  CRP titre is tested in acute infections 78
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 79
    • Epidemiology  Source – respiratory tract of humans  Spread – droplets  Carriers – pharynx  Low immunity is responsible for fulminant infections RSV infection, pulmonary congestion, stress, malnutrition, alcoholism  Splenectomy  Sickle cell disease  80
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 81
    • Diseases caused  Middle ear – otitis media  Para nasal sinuses – sinusitis  Respiratory tract – pneumonia, bronchitis, empyema  Meningitis is secondary to otitis media, penumonia, sinusitis and conjunctivitis 82
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 83
    • Laboratory diagnosis  Sample sputum – pneumonia  septicemia - blood culture  Otitis media - fluid from middle ear  Meningitis - CSF   Method Gram stain, microscopy  culture  84
    •  Latex agglutination for pneumococcal antigen in serum of patients 85
    • Description headings          Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment 86
    • Treatment  Penicillin  Amoxycillin  ceftriaxone/ceftazidime  Vancomycin 87
    • Prophylaxis  Pneumococcal conjugate vaccine is available  Given to splenectomy patients, sickle cell anemia patients and susceptible individuals 88
    • GROUP D STREPTOCOCCI Enterococcus faecalis Enterococcus faecium • GI tract of humans and animals • Group D carbohydrate cell wall antigen • Formerly Streptococcus 89
    •  Cause UTI, wound infection  Endocarditis  Intra abdominal abcesses 90
    • 91