Streptococcus Microbiology Lecture 04 Kmu

Streptococcus Kmu lecture

1. Streptococci Shah Faisal Jamal KMU-IPMS

2. Streptococci Streptococci are spherical gram-positive, non-spore forming nonmotile facultative anaerobic cocci arranged in chains or pairs Lenght may vary from a single pair to continuous chains over 30 cells, depending on the specie and growth condition All streptococci are catalase-negative, whereas staphylococci are catalase-positive Some members form capsules composed of polysaccharide complexes or hyaluronic acid Streptococci grow best in enriched media. Sheep blood agar is prefered because it satisfies the growth requirements and also serves as an indicator for paatterns of hemolysis

3. Classification At the turn of the 20 th century, a classification based on hemolysis and biochemical tests was sufficient to associate some streptococcal species with infection in human. Rebecca Lancefield, demonstrated carbohydrate antigens in cell wall extracts of the β- Hemolytic streptococci, Her studies formed a classfication by serogroups (eg A,B,C) Later it was also discovered that nonhemolytic streptococci also have the same cell wall antigens

4. Classification Over the years it has become clear that possession of one of the lancefield a particularly virulence segment of the streptococcal genus regardless of hemolytic patterns For practical purposes, the type of hemolysis and certain biochemical reactions remain valuable for the initial recognition and presumptive classification of streptococci.

5. Lancefield Groups Membrane Ag, Groups A-H, K-V Group A Strep. pyogenes Group B Strep. agalactiae Group C, F, G Strep equisimilis Strep zooepidemicus Strep anguinosus Group D E. faecalis Strep bovis Strep equines Group K Strep salivarius Viridans Strep mutans Strep mitis Strep sanguis Pneumococci

6. Types of Hemolysis α- Hemolytic streptococci form a green zone around their colonies as a result of incomplete lysis of red blood cells in the agar. The green color is formed when hydrogen peroxide produced by the bacteria oxidizes hemoglobin (red color) to biliverdin (green color). β- Hemolytic streptococci form a clear zone around their colonies because complete lysis of the red cells occurs. β- Hemolysis is due to the production of enzymes (hemolysins) called streptolysin O and streptolysin S γ- hemolysis streptococci are nonhemolytic

7. Group A Streptococci (S. pyogenes) Habitat Habitat is the human throat and skin. Diseases Suppurative diseases (Pus producing) Non suppurative diseases (Immunologic) Transmission Cough, sneezing, even conversation, tiny skin pustules are spread by scratching & direct contact or shared fomities and also hand to hand transmission

8. Antigenic structure of GAS and adhesion to an epithelial cell.

9. Pathogenesis and Clinical Manifestation Group A streptococci ( S. pyogenes ) cause disease by three mechanisms : P yogenic inflammation, which is induced locally at the site of the organisms in tissue E xotoxin production, which can cause widespread systemic symptoms in areas of the body where there are no organisms Immunologic, which occurs when antibody against a component of the organism cross-reacts with normal tissue or forms immune complexes that damage normal tissue The M protein of S. pyogenes is its most important antiphagocytic factor, but its capsule, composed of hyaluronic acid, is also antiphagocytic. Antibodies are not formed against the capsule because hyaluronic acid is a normal component of the body and humans are tolerant to it.

10. G roup A streptococci toxins and hemolysins Erythrogenic toxin causes the rash of scarlet fever. Its mechanism of action is similar to that of the TSST of S. Aureus Streptolysin O is a hemolysin that is inactivated by oxidation (oxygenlabile ). It causes β- hemolysis only when colonies grow under the surface of a blood agar plate Streptolysin S is a hemolysin that is not inactivated by oxygen (oxygenstable) Pyrogenic exotoxin A is the toxin responsible for most cases of streptococcal toxic shock syndrome . It has the same mode of action as does staphylococcal TSST Exotoxin B is a protease that rapidly destroys tissue and is produced in large amounts by the strains of S. pyogenes , the so-called “flesh-eating” streptococci that cause necrotizing fasciitis . The C5a peptidase degrades complement component C5a, the main factor that attracts phagocytes to sites of complement deposition

11. Strep pyogenes infections

12. Strep pyogenes diseases Pharyngitis Scarlet Fever (rash) Skin Pyoderma Impetigo Erysipelas Cellulitis Strep TSS Necrotizing fasciitis Myositis Immune Mediated Rheumatic fever Glomerulonephritis

13. Streptococcal Pharyngitis Occur at any age, most frequently 5-15 years Characterized by acute sore throat, malaise, fever and headache Involves tonsillar pillars, uvula & soft palate. Which become red, swollen and covered with yellow white exudate Cervical lymph nodes become swollen and tender GAS pharyngitis is usually self-limiting. Typically, the fever is gone by the third to fifthday , and other manifestations subside within 1 week Untreated pharyngitis may extend to the middle ear (otitis media), the sinuses (sinusitis), the mastoids (mastoiditis ), or the meninges (meningitis).

14. Impetigo Primary lesion is upto 1cm vesicle surrounded by erythema The vesicle enlarges and eventually breaks to form a yellow crust The lesions usually appear in 2- to 5-year-old children on exposed body surfaces, typically the face and lower extremities

15. Erysipelas Erysipelas is a distinct form of streptococcal infection of the skin and subcutaneous tissues, primarily affecting the dermis It is characterized by a spreading area of erythema and edema with rapidly advancing, well-demarcated edges, pain, and systemic manifestations, including fever and lymphadenopathy Infection usually occurs on the face, and a previous history of streptococcal sore throat is common

16. Necrotizing fasciitis (”flesh eating bacteria”) When there is destruction of the fibrous tissue deep in the skin The sheath of tissue that covers the muscle is destroyed Destruction is due to release of exotoxin A that stimulates production of cytokines damaging endothelial lining and leaking fluid into the extravascular space causing diminished blood flow, tissue hypoxemia, and tissue death Can also be caused by Staph aureus and other bacteria

17. Scarlett Fever If the infecting streptococci produce erythrogenic toxin and the host lacks antitoxin , scarlet fever may result. A “strawberry” tongue is a characteristic lesion seen in scarlet fever.

18. Streptococcal Toxic Shock Syndrome (STSS ) Beta-hemolytic group A streptococci can cause toxic shock syndrome like that caused by Staphylococcus aureus Similar to scarlet fever, streptococcal toxic shock syndrome is also mediated by the release of pyrogenic toxin

19. Poststreptococcal Sequelae ACUTE RHEUMATIC FEVER Acute rheumatic fever is a nonsuppurative inflammatory disease characterized by fever, carditis, subcutaneous nodules, chorea, and migratory polyarthritis . The antigen stimulating these antibodies is most probably M protein, but the group A carbohydrate is also a possibility. There is similarity between the structure of regions of the M protein and myosin, and M protein fragments have been shown to stimulate antibodies that bind to human heart sarcolemma membranes, cardiac myosin, synovium, and articular cartilage. A cellular reaction pattern consisting of lymphocytes and macrophages aggregated around fibrinoid deposits is found in human hearts. This lesion, called the Aschoff body is considered characteristic of rheumatic carditis

20. Poststreptococcal Sequelae ACUTE GLOMERULONEPHRITIS The renal injury of acute glomerulonephritis is caused by deposition in the glomerulus of antigen–antibody complexes with complement activation and consequent inflammation. This is a type III hypersensitivity. The M proteins of some nephritogenic strains have been shown to share antigenic determinants with glomeruli, which suggests an autoimmune mechanism similar to rheumatic fever Poststreptococcal glomerulonephritis is primarily a disease of childhood that begins 1 to 4 weeks after streptococcal pharyngitis and 3 to 6 weeks after skin infection. It is characterized clinically by edema, hypertension, hematuria, proteinuria, and decreased serum complement levels .

21. Diagnosis Suppurative Infections Gram Stain, smear and culture. B- hemolytic colonies on blood agar (Hemolysis due to streptolysin O & S) Isolates are sensitive to bacitracin ELISA tests are available for GAS antigens in throat swab Non suppurative infections If rheumatic fever is suspected, patients antistreptolysin O (ASO) antibody titer is tested If acute glomerulonephritis is suspected antibody to streptococcal Dnase B is used as evidence of a previous skin infection by S. Pygenes.

22. Treatment and prevention Penicillin G (No significant resistance) Penicillin is used in patients with rheumatic fever to prevent recurrent s.pygenes pharygitis. This prevents additional damage to heart valves Multivalent vaccines using M protein epitopes that are not cross-reactive to self are in clinical trials with encouraging results.

23. Group B Streptococcus (S. agalactia ) Characteristics Gram positive cocci in chains, B-hemolytic colonies, catalase negative, Bacitricin resistant. Habitat Habitat is the human GIT & vagina ( Group B streptococci can be found in the lower gastrointestinal and vaginal flora of 10% to 40% of women ) Diseases Neonatal Meningitis and sepsis Transmission Trasmission occurs during birth

24. Pathogenesis & clinical manifestations In adults it rarely causes URT infections, meningitis, bacteremia, and endocarditis It used to be a major cause of puerperal sepsis (post-partum sepsis) The most serious cases of group B infections occur in the newborn There are two types of disease in the newborn Early onset disease – occurs when babies become infected in utero or at birth, with the organism gaining access through the respiratory tract The disease has a high mortality rate and is characterized by respiratory disease and bacteremia Septicemia and meningitis may also occur

25. Pathogenesis & clinical manifestations Late onset disease – occurs 7-10 days after birth and the baby probably acquires the organism by direct contact with mucosal surfaces The disease is characterized by meningitis or osteomyelitis and possibly bacteremia The mortality rate is high, but lower than that for the early-onset disease Although most group B streptococcal infections are in neonates, this organism also causes such infections as pneumonia, endocarditis, arthritis, cellulitis, and osteomyelitis in adults. Postpartum endometritis also occurs. Diabetes is the main predisposing factor for adult group B streptococcal infections

26. Lab Diagnosis Specimens: Include cerebrospinal fluid, and blood for culture from neonates. High vaginal swab is required from women with suspected sepsis Gram stain smear and culture B-hemolytic colonies on blood agar that is resistant to bacitracin CAMP (Christie, Atkins, Munch, Peterson) test to identify presumptively S. agalactiae +ve Hippurate hydrolysis test + ve

27. Treatment and prevention Penicillin G for GBS infection No vaccine available Ampicillin should be given to mothers if prolonged rupture of membranes occurs, if mother has a fever or if the neonate is premature

28. Enterococci (Group D) Characteristics Gram positive cocci in chains, catalase negative, non- hemolytic or alpha hemolytic, non-capsulate and the majority are non-motile Habitat Habitat is the human colon, urethra and female genital tract but mainly GIT Diseases Urinary tract infection, biliary tract infection are frequent, endocarditis are rare but life threatening Transmission May enter bloodstream and gastrointestinal or genitourinary tract through procedures

29. Enterococci (Group D) Formerly called streptococci, two important species E. faecalis and E. faecium E. faecalis is the main pathogen in the genus Enterococcus, causing about 95% of enterococcal infections, a minority of infections are caused by E. faecium The term enterococcus derives from their presence in the intestinal tract

30. Pathogenesis & clinical manifestation Enterococci are a significant cause of disease in specialized hospital settings They are not highly virulent. On their own, they do not produce fulminant disease and in wound and soft tissue infections are usually mixed with other members of the intestinal flora Enterococci cause opportunistic urinary tract infections (UTIs) and occasionally wound and soft tissue infections, in much the same fashion as members of the Enterobacteriaceae

31. Pathogenesis & clinical manifestation Infections are often associated with urinary tract manipulations, malignancies, biliary tract disease, and gastrointestinal disorders Vascular or peritoneal catheters are often points of entry There is sometimes an associated bacteremia, which can result in the development of endocarditis on previously damaged cardiac valves

32. Lab Diagnosis Morphology: Enterococcus species are Gram positive cocci, occurring in pairs or short chains Culture Enterococci are aerobic organisms capable of growing over a wide temperature range, 10–45 ºC Blood agar: Enterococci are mainly nonhaemolytic but some strains show alpha or beta-haemolysis Enterococcus species are also able to grow in the presence of 6.5% sodium chloride and 40% bile When grown on media containing esculin , enterococci hydrolyze the esculin , producing black colonies

33. Enterococcus Grou p D Streptococcus Bile Esculin Agar Negative Bile Esculin Agar Positive

34. Treatment and Prevention Penicillin or vancomycin plus gentamycin is used combinely. Organism is resistant to drug given individually. Vancomycin resistant enterococci (VRE) are important causes of nosocomal infection, for which linzolid is best option Penicillin and gentamycin should be given to patients with damaged heart valves prior to intestinal or urinary tract procedures No vaccine is available

35. Streptococcus pneumoniae Characteristics Gram positive (lancet “bullet” shaped) cocci in pairs or in short chains, catalase negative, alpha hemolytic colonies. Growth is inhibited by optochin, colonies are bile soluble. Prominant polysaccharide capsule (85 serotypes) Habitat Resides asymptomatically in healthy carriers typically colonizing the respiratory tract, sinuses and nasal cavity Diseases Pneumonia, meningitis in adults and otitis media, sinusitis and conjunctivitis in childrens. S. Pneumoniae cause of community acquired pneumoniae Transmission Spread via respiratory droplets and autoinoculation in persons carrying the bacteria.

36. S. pneumoniae: lancet-shaped diplococcus

37. Streptococcus pneumoniae Pneumococcal cell wall structure is similar to other streptococci Teichoic acid, LPA, and phosphocholine are rooted in the peptidoglycan extending outward into the capsule Where they provide binding domains for a variety of surface proteins

38. Streptococcus pneumoniae Possess polysaccharide capsules (85 distint types) With type specific antiserum capsules swell (quelling reaction) Capsules are virulence factor (Antiphagocytic), favor invasiveness Another important surface component is C-substance It reacts with a normal serum protein called C-reative protein (CRP). CRP is an acute phase protein that is elevated upto 1000 folds in acute inflammation and is a nonspecific indicator of inflammation. CRP is a better predictor of heart attack risk than an elevated cholesterol level

39. Pathogenesis & clinical manifestation M ost important virulence factor is the capsular polysaccharide, and anticapsular antibody is protective Lipoteichoic acid, which activates complement and induces inflammatory cytokine production, contributes to septic shock syndrome in immunocompromised patients Pneumolysin, the hemolysin that causes α- hemolysis, may also contribute to pathogenesis. Pneumococci produce IgA protease that enhances the organism’s ability to colonize the mucosa of the upper respiratory tract Pneumococci multiply in tissues and cause inflammation.

40. Pathogenesis & clinical manifestation When they reach alveoli, there is outpouring of fluid and red and white blood cells, resulting in consolidation of the lung. During recovery, pneumococci are phagocytized, mononuclear cells ingest debris, and the consolidation resolves . Factors that lower resistance and predispose persons to pneumococcal infections are Alcohol, drug intoxication, cerebral impairment, repiratory tract abnormality, abnormal circulatory dynamics, certain chronic diseases like scikle cell anemia and splenectomy

41. Pathogenesis & clinical manifestation Pneumonia often begins with a sudden chill, fever, cough, and pleuritic pain. Sputum is a red or brown “rusty” color. Bacteremia occurs in 15% to 25% of cases. Spontaneous recovery may begin in 5 to 10 days and is accompanied by development of anticapsular antibodies. Pneumococci are a prominent cause of otitis media , sinusitis, mastoiditis, conjunctivitis, purulent bronchitis, pericarditis, bacterial meningitis, and sepsis. Pneumococci are the leading cause of sepsis in patients without a functional spleen.

42. Strep pneumoniae diseases

43. Laboratory Diagnosis Gram positive bacteria and culture produce alpha hemolytic colonies on blood agar. Growth is inhibited by bile and optochin. Quelling reaction occurs (swelling of capsule with types specific antiserum) Serologic test is not useful Test for capsular antigen in spinal fluid and C polysaccharide in urine can be diagnostic

44. Treatment and prevention Penicillin G, resistance is caused by alterations in penicillin binding protein, no Beta lactamase is made Cephalosporins, erythromycin, chloramphenicol or vancomycin are used for patients allergic to penicillin or for treatment of penicillin resistant strains Two vaccines are available One is used for adults containing 23 serotypes Other is primarily used in children undre age 2 years contains 13 serotypes