Streptococci

microbiology

1. STREPTOCOCCUS LAKSHMI SASIKANTH 51

2. CONTENTS MORPHOLOGY CLASSIFICATION CULTURAL CHARACTERISTICS BIOCHEMICAL REACTIONS RESISTENCE & ANTIGENIC STRUCTURE TOXINS AND OTHER VIRULENCE FACTORS PATHOGENICITY LAB DIAGNOSIS TREATMENT AND PROPHYLAXIS 08-07-2015 2

3. introduction First seen in wound infections by Billroth –called them streptococci-1874 Gram Positive cocci Arranged in chains Part of normal flora of humans and animals 08-07-2015 3

4. CLASSIFICATION Classified by Brown in1919 based on their growth in 5% Blood Agar Normal commensals 80 types 08-07-2015 4

5. ALPHA HEMOLYSIS BETA HEMOLYSIS GAMMA HEMOLYSIS Greenish discolouration with partial hemolysis Small zone of lysis (1-2mm) with indefinite margins Unlysed RBCs seen under microscope Sharply defined ,clear, colourless zone of hemolysis 2-4 mm wide RBCs lysed completely No hemolysis 08-07-2015 5

6. STREPTOCOCCUS PYOGENES MORPHOLOGY Individual cocci are spherical or oval ( 0.5-1 micrometer ) Arranged in chains of varying lengths (?? ) Longest chain is formed by S.salivarius Non-motile & non sporing 08-07-2015 6

7. CULTURAL CHARACTERISTICS Aerobes as well as facultative anaerobes Grown best at 37°C   ( 22-42°C   ) Grows in media rich in fermentable carbohydrates or enriched media with blood or serum ON BLOOD AGAR Shows beta hemolysis Virulent strains form matt colonies Avirulent strains form glossy colonies Some strains with capsule form mucoid colonies ON LIQUID MEDIA Growth occur as a granular turbidity with a powdery deposit in glucose or serum broth 08-07-2015 7

8. Biochemical reactions 08-07-2015 8

9. ANTIGENIC STRUCTURE 08-07-2015 9

10. TOXINS AND VIRULENCE FACTORS S.Pyogenes forms several exotoxins and enzymes that contributes its virulence. M Protein also act as a virulence factor by inhibiting phagocytosis H EMOLYSIN PYROGENIC E XOTOXIN S TREPTOKINASE (FIBRINOLYSIN) D EOXYRIBONUCLEASES N ADase H YALURONIDASE S ERUM OPACITY FACTOR OTHER E NZYMES HEN SHEDS

11. 1. HEMOLYSINS 2 types STREPTOLYSIN O AND S STREPTOLYSIN O Oxygen labile & heat labile Inactive in oxidized form but reactivated on treating with mild reducing agents Lethal on i.v injection and is cardiotoxic & leucotoxic activity Its antigenic and antistreptolysin O appears in sera following its infection ASO TITRE Earlier done by hemolysis inhibition test Now done by serological method of latex agglutination ASO titer > 200 units is significant & suggests a recent or recurrent infection with streptococci 08-07-2015 11

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13. STREPTOLYSIN S Soluble in serum,thus the name Oxygen stable hemolysin Responsible for hemolysis seen in blood agar It’s a protein but is not antigenic Non specifically inhibited by serum lipoproteins STREPTOLYSIN S AND O ARE PRODUCED BY GROUPS A,C & G

14. 2.PYROGENIC EXOTOXIN ERYTHROGENIC / DICK /SCARLATINAL TOXIN Its injection into susceptible individuals cause an erythematous reaction (DICK TEST) Used to identify scarlet fever in children Toxin induced fever. Hence renamed as Streptococcal pyrogenic exotoxin {SPE} 3 types of SPE – A, B & C Types A & C are coded for by bacteriophage genes Type B gene is chromosomal SPEs are SUPERANTIGENS (like staph & TSS toxin) That is the T cell mitogen that induce a massive release of inflammatory cytokines, causing fever, shock and tissue damage 08-07-2015 14

15. 3. STREPTOKINASE (Fibrinolysin) Promotes lysis of fibrin clots by activating a plasminogen Antigenic protein Antistreptokinase antibodies provide retrospective evidence of strept . Infection BIOLOGICAL ROLE : It breaks down the fibrin barrier around the lesion & facilitate spreading of infection Intravenous streptokinase is given for the Treatment of early MI & other thromboembolic disorders 08-07-2015 15

16. 4. DEOXYRIBONUCLEASES ( Streptodornase or DNAase ) Causes depolymerization of DNA Pyogenic exudates contain large amount of DNA derived from nuclei of necrotic cells Helps to liquefy the thick pus & hence responsible for the thin serous character of streptococcal exudates. 4 antigenically distinct DNAases are recognized - A,B,C & D B is the most antigenic in humans Demo. Of ANTI- DNAase B antibody is used in the retrospective diagnosis of S.p infection THERAPEUTIC APPLICATION: Liquefying localized collection of thick exudates as in empyema, a preparation of streptokinase and streptodornase are used 08-07-2015 16

17. 5. NICOTINAMIDE ADENINE DINUCLEOTIDASE NADase acts on co-enzyme NAD and liberates nicotinamide Antigenic Leucotoxic 08-07-2015 17

18. 6.HYALURONIDASE Breaks down hyaluronic acid of tissues Thus favours spread of infection along intercellular spaces S.cocci also possess a H.acid capsule & thus it exhibits a self destructive process Antigenic 08-07-2015 18

19. 7.SERUM OPACITY FACTOR Produced by some M types of S.pyogenes SOP is a lipoproteinase that results in opacity when applied to agar gel containing horse or swine serum 08-07-2015 19

20. 8.OTHER ENZYMES Many strains also produce PROTEINASE PHOSPHATASE ESTERASES N-ACETYL GLUCOSAMINIDASE NEURAMINIDASE Their extend of pathogenicity is unknown 08-07-2015 20

21. PATHOGENECITY SUPPURATIVE STREPTOCOCCAL DISEASES 1.RESPIRATORY INFECTIONS Primary site of invasion by S.pyogenes (lower M type) is the throat SORE THROAT is the most common streptococcal infection Produce tonsillitis or pharyngitis Virulent group A streptococci adhere to pharyngeal epithelium by means of the lipoteichoic acid covering the surface pili The glycoprotein fibronectin on the epithelial cells serve as the receptor to lipoteichoic acid ligand From throat s.cocci may spread to surrounding tissues, leading to suppurative complications like otitis media, mastoditis , quinsy, Ludwig’s angina and suppurative adenitis Rarely lead to meningitis & S.pneumonia 08-07-2015 21

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23. 08-07-2015 23 QUINSY MASTODITIS SUPPURATIVE ADENITIS LUDWIGS ANGINA

24. 2.SKIN & SOFT TISSUE INFECTION 2 Typical Streptococcal skin infections are : ERYSIPELAS It’s a diffuse infection involving superficial lymphatics Affected skin is red, swollen & indurated Rare & seen in older patients 08-07-2015 24 IMPETIGO Caused by the higher numbered M type of streptococci Tiny blisters are the first symptom of impetigo. When the blisters burst, the skin underneath them is moist, red, and may ooze fluid. Next, a tan or yellow-brown crust covers the wet areas, making it look like they've been coated with honey or brown sugar.

25. CELLULITIS It usually affects a limb but can occur anywhere on the body . Symptoms and signs are usually localized to the affected area but patients can become generally unwell with fevers, with chills & rigor (bacteremia) Redness, Swelling, Increased warmth, Tenderness, Blistering, Abscess, Erosions and ulceration 08-07-2015 25 NECROTISING FASCIITIS Caused by mixed aerobic & anaerobic bacterial infection Some strains of S.pyogenes may alone be responsible ( M type 1&3 ) Notoriety under the name FLESH EATING BACTERIA Extensive necrosis of subcut. & muscular tissues assoc. with severe systemic infection with DIC and MSF.

26. ERYSIPELAS IMPETIGO CELLULITIS NECROTISING FASCIITIS

27. S.Pyogenes are isolated from the lesion Rising titres of ASO and anti- DNAase B are demonstrated Vancomycin is the drug of choice in life-threatening cases as penicillin mayn’t be effective. Soft tissue infection with some M types of S.pyogenes cause a TSS resembling staphylococcal TSS 08-07-2015 27

28. 3.GENITAL INFECTIONS Both aerobic & anaerobic s.cocci are normal inhabitants of female genitalia. Imp. c ause of PUERPERAL SEPSIS Semmelweis - 1847- hand washing Now puerperal fever is common due to endogenous anaerobic streptococci 08-07-2015 28

29. 4.OTHER SUPPURATIVE INFECTIONS S.PYOGENES can cause abscesses in internal organs like brain ,lungs ,liver & kidney Septicemia & pyemia. 08-07-2015 29

30. NON-SUPPURATIVE STREPTOCOCCAL DISEASES A 7 year old boy developed skin infection but his mother didn’t seek medical help. He passed coloured urine . 4 days later he developed pitting edema in both ankles. On examination B.P was elevated 4+ proteinuria, RBC casts & elevated serum creatinine DIAGNOSIS ?? ACUTE POST- STREPTOCOCCAL GLOMERULONEPHRITIS

31. 2 imp. Infections are Acute Rheumatic Fever & Acute Glomerulonephritis These complications develop 1-3 weeks after acute infection Thus the organism mayn’t be detectable when sequelae sets in . ACUTE RHEUMATIC FEVER Rheumatic fever follows persistent or repeated streptococcal throat infections with a strong antibody response The lesion is carditis, including connective tissue degeneration of heart valves & inflammatory myocardial lesions characterized by ASCHOFF Nodules Antigenic cross reaction between streptococci and heart tissues

32. ACUTE GLOMERULONEPHRITIS Caused by only a few nephritogenic type of streptococci Impetigo & infection of scabies lesions are more important here than throat infections Nephritis resolves without any permanent damage Pathogenesis : antigenic cross reaction between glomerular membrane antigen & cell membranes of nephritogenic streptococci.

33. EPIDEMIOLOGY Main source of S.p is human upper respiratory tract (3) of patients and carriers Symptomless infection is common Transmission by direct contact or through contaminated fingers, dust or fomites Streptococcal skin infection is common & spread by non-biting insects Streptococcal RTI are frequent in children at 5-8 years of age Crowding is an imp. Factor Outbreaks of infection are common in hostels and army camps 08-07-2015 34

34. LAB DIAGNOSIS In acute infections, diagnosis is established by culture In non- suppurative complications are diagnosed by demo. Of antibodies SPECIMEN Throat swab, pus swab or exudates are collected In RF & GN serum is collected for serology 2) MICROSCOPY Observing gram stained films from pus Presence of gram positive cocci in chains indicate the infection Smears are of no value in infections of throat or genitalia. Y??? 08-07-2015 35

35. 3) CULTURE Swabs collected from affected site are plated immediately or send to lab in PIKE’S MEDIUM ( Blood agar containing 1 in 10 lakh crystal violet & 1 in 16,000 sodium azide ) The specimen is plated on blood agar & incubated @ 37°C anaerobically or under 5-10% CO2 08-07-2015 36

36. IDENTIFICATION Hemolytic strept . a re grouped by the Lancefield technique using specific antisera RAPID DIAGNOSTIC TEST KITS Used f or the detection of streptococcal group A antigen from throat swabs BACITRACIN SENSITIVITY : A convenient method for identification of S.pyogenes. They are more sensitive to bacitracin than other streptococci A filter paper disc of 0.04U is applied on the surface of an inoculated blood agar After incubation a wide zone of inhibition is seen with S.pyogenes but not with other streptococci 08-07-2015 37

37. 4 ) SEROLOGY Diagnosis of RF & GN can be made by demonstrating high levels of antibody to streptococcal toxins Standard test is ASO TITRATION ASO titres > 200 indicates prior streptococcal infection High levels found in ARF but in GN the titres are often low ANTI- DNAase B estimation Titres >300 are taken significant Mainly used in diagnosis of streptococcal pyoderma for which ASO titres is of much less value STREPTOENZYME TEST A passive hemagglutination test using erythrocytes sensitized with a crude preparation of extracellular antigens of streptococci V ery sensitive and specific test Becomes positive after all types of streptococcal tests 08-07-2015 38

38. TYPING MTR protein based typing of S.pyogenes Is done & required only for epidemiological purposes Done by precipitation or agglutination tests using specific antisera 08-07-2015 39

39. TREATMENT All ß-hemolytic strept . are sensitive to PENICILLIN G Most of them are sensitive to ERYTHROMYCIN In patients allergic to penicillin erythromycin or cephalexin are used Anti microbial drugs have no effect on established GN or RF 08-07-2015 40

40. PROPHYLAXIS 08-07-2015 41 The indication of prophylaxis is only in the prevention of Rheumatic fever Achieved by long term administration of PENICILLIN in children who have developed early signs of rheumatic fever. This prevents streptococcal reinfection and further damage to heart Antibiotic prophylaxis is not useful for glomerulonephritis as this complication follows a single streptococcal infection & reinfection don’t occur .

41. OTHER HEMOLYTIC STREPTOCOCCI 08-07-2015 42 GROUP B Important pathogens of cattle causing bovine mastitis S.agalactiae – important pathogen causing human infections NEONATAL INFECTIONS Most common cause of neonatal meningitis 2 TYPES : 1 ) EARLY ONSET TYPE : Occur within a week of birth Presentation as meningitis or septicemia 2) LATE ONSET TYPE : Occur within 2 nd & 12 th weeks of life Presentation as septicemia SOURCE???

42. ADULT INFECTIONS PEURPERAL SEPSIS & PNEUMONIA CAMP TEST Identification method Based on their ability to hydrolyze Hippuric acid A zone of hemolysis is seen when S.agalactiae is inoculated perpendicular to streak of S.aureus grown on blood agar Human pathogenic GROUP B s trains possess a polysaccharide capsule that gives virulence 9 capsular serotypes have been identified 08-07-2015 43 Other neonatal infections include osteoarthritis, osteomyelitis, respiratory infections, peritonitis, omphalitis & endocarditis

43. GROUP C 08-07-2015 44

44. GROUP D ( Non- enterococcal ) 08-07-2015 45

45. GROUP F 08-07-2015 46

46. OTHER GROUPS GROUP G & O - N ormal commensals of throat May occasionaly cause tonsillitis endocarditis & UTI GROUP H&K - I nfective endocarditis GROUP R - Meningitis , Septicemia, & RTI in persons in contact with infected pigs & meat 08-07-2015 47

47. ENTEROCOCCUS SPECIES They are fecal streptococci reclassified as a separate genus called enterococci Contains different species like E.faecalis , E.faecium , & E.durans . They appear as pairs of oval cocci, the cell are arranged at an angle to each other

48. They are relatively resistant, surviving at 60°C for 30 minutes On Mac Conkey medium – produce tiny pink colonies Identified by its ability to ferment mannitol , sucrose, sorbitol & esculin They are frequently isolated from UTI & wound infection Also cause endocarditis, biliary tract infection, septicemia & intra-abdominal abscess Antibiotic sensitivity is done before treatment Intrinsically resistant to cephalosporins VANCOMYCIN is used But, recently VANCOMYCIN-RESISTANT-STRAINS ( VRE) are observed M echanism of resistance - Alteration in D- alanyl -D-alanine chain in cell wall

49. STREPTOCOCCI VIRIDANS Normally resident in mouth & URT Alpha lysis on blood agar – hence the name Not grouped by Lancefield scheme ( S.sangius ) Classified into many species like : S.mitis , S.mutans , S.salivarius & S.sangius based on biochemical properties Risks in people with pre-existing cardiac lesions Causes bacterial endocarditis Following dental procedures, they cause bacteremia & get implanted on damaged or prosthetic valves or in congenital HD & grow to form vegetation Thus penicillin prophylaxis is indicated before the procedure But antibiotic sensitivity is determined for proper treatment

50. STREPTOCOCCUS MUTANTS Normal flora of oral cavity Can cause dental caries & endocarditis in patients with risk factors It has a polysaccharide coat that allows it to stick to the teeth & to damaged heart valves & invade the bloodstream Normal body defenses are adequate to prevent this infection PREVENTION Maintenance of good oral hygiene, regular dental checkups & prophylactic antibiotics prior to dental work on people with damaged heart valves.

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