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Streptococci and Other Streptococci-like Organisms.

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Presentation on theme: "Streptococci and Other Streptococci-like Organisms."— Presentation transcript:

1 Streptococci and Other Streptococci-like Organisms

2 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Case Study u9-year-old boy complains of fever and sore throat uOn examination, his pharynx is red and his tonsils are swollen uHis cervical lymph nodes are also swollen uA throat culture is taken

3 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Points to Consider uClinical symptoms presented by the patient uThe serious complications that may result from this type of infection uHow to recover and identify the infecting organism uWhat other species are involved in clinical infections uOther points to consider

4 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Streptococcus and Enterococcus : General Characteristics uGram-positive, facultatively anaerobic cocci uMost are typically spherical; some may appear elongated

5 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Streptococcus and Enterococcus : General Characteristics uAppear in chains when smears are prepared from broth cultures uCatalase-and oxidase-negative

6 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Streptococcus and Enterococcus : Habitat and Clinical Infections uHabitat 4Indigenous respiratory tract microbial flora of animals and humans 4Certain species are also found in the gastrointestinal and urogenital tracts of humans uClinical infections 4Upper and lower respiratory tract infections 4Urinary tract infections 4Wound infections 4Endocarditis

7 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Streptococcus and Enterococcus : Cell Wall Structure uThick peptidoglycan layer uTeichoic acid uC=carbohydrate layer present except in viridans group uCapsule in S. pneumoniae and in young cultures of most species

8 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Streptococcus and Enterococcus : General Characteristics uHemolytic Patterns 4Beta (ß) a clear, colorless zone around the colony caused by complete hemolysis of the red blood cells in the agar

9 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Streptococcus and Enterococcus : Hemolytic Patterns 4Alpha (a):hemolysis showing a greenish discoloration around the area surrounding the colony due to incomplete hemolysis of the red blood cells in the agar

10 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Streptococcus and Enterococcus : Hemolytic Patterns 4No hemolysis (gamma): colonies show no hemolysis or discoloration

11 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Classification of Streptococcus and Enterococcus

12 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Biochemical Identification uSusceptibility tests 4Bacitracin (0.04 units) or “A” disk FIdentifies Group A streptococci Group A streptococcus is susceptible to “A” disk (left)

13 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Biochemical Identification uSusceptibility test 4Trimethoprim sulfamethoxazole (SXT) FInhibits beta-hemolytic streptococcal groups other than A and B Group A streptococcus growing in the presence of SXT

14 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Biochemical Identification uSusceptibility test 4Optochin “P” disk FDifferentiates S. pneumoniae from other alpha-hemolytic streptococci (Viridans group) uBile solubility test 4S pneumoniae lyses in a suspension of sodium deoxycholate while other viridans streptococci do not lyse

15 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Biochemical Identification uPYR hydrolysis  Substrate L-pyrrolidonyl-  napthlyamide (PYR) is hydrolyzed by Group A Streptococci and Enterococcus sp. 4As specific as 6.5% NaCl broth for Enterococcus sp. 4More specific than Bacitracin for Group A streptococci PYR test for Group A streptococci and enterococci. Both are positive for this test (right); left is a negative result

16 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Biochemical Identification uHydrolysis 4Hippurate hydrolysis FDifferentiates Group B streptococci from other beta hemolytic streptococci FGroup B streptococci hydrolyzes sodium hippurate

17 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Biochemical Identification uChristie-Atkins, Munch- Petersen (CAMP) test  Detects the production of enhanced hemolysis that occurs when  -lysin and the hemolysins of Group B streptococci come in contact Group B streptococci showing the classical “arrow-shaped hemolysis near the staphylococcus streak

18 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Biochemical Identification uBile Esculin hydrolysis 4Ability to grow in 40% bile and hydrolyze Esculin are features of streptococci that possess Group D antigen uGrowth in 6.5% NaCl broth 4Differentiates Group D streptococci from enterococci Both Group D streptococci and enterococci produce a positive (left) bile Esculin hydrolysis test.

19 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Clinically Significant Streptococci: Streptococcus pyogenes or Group A Beta-Hemolytic Streptococci uBacterial structure 4Fimbrae: attachment and adherence 4M protein: major virulence factor 4Hyaluronic acid capsule: prevents phagocytosis

20 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. S treptococcus pyogenes or Group A Streptococci : Additional Virulence Factors  Hemolysins  Streptolysin O  Streptolysin S  Erythrogenic toxin  Enzymes  Streptokinase  DNases 4Hyaluronidase

21 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Streptococcus pyogenes (Group A) Streptococcal Infections  Acute bacterial pharyngitis  Sore throat  Malaise 4Fever/headache uScarlet fever  Pyodermal infections  Impetigo 4Erysipelas Erysipelas due to Streptococcus pyogenes

22 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Post–Group-A Streptococcal Infections uRheumatic fever from pharyngeal infections only 4Fever 4Inflammation of the heart, joints, blood vessels, and subcutaneous tissues 4Chronic, progressive damage to the heart valves

23 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Post–Group-A Streptococcal Infections uAcute glomerulonephritis from either cutaneous or pharyngeal infections 4More common in children than adults 4Antigen-antibody complexes deposit in the glomerulus 4Inflammatory response causes damage to the glomerulus and impairs the kidneys

24 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Invasive Group A Streptococcal Infections uStreptococcal toxic shock syndrome 4Multi-organ system failure similar to staphylococcal toxic shock 4Initial infection may have been pharyngitis, cellulitis, peritonitis, or other wound infections

25 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Invasive Group A Streptococcal Infections: “Flesh-Eating Bacteria” uCellulitis 4Severe form of infection that is life-threatening 4Bacteremia and sepsis may occur 4In patients necrotizing fasciitis, edema, erythema, and pain in the affected area may develop 4Streptococcal myositis resembles clostridial gangrene

26 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Laboratory Diagnosis: Group A Streptococcus Grams stained wound smear showing gram-positive cocci in chains with numerous “polys”

27 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Laboratory Diagnosis: Group A Streptococcus uColony morphology  Transparent, smooth, and well-defined zone of complete or  - hemolysis

28 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Laboratory Diagnosis: Group A Streptococcus uIdentification 4Catalase-negative 4Bacitracin-susceptible 4PYR-positive 4Bile-esculin–negative 46.5% NaCl-negative Group A streptococci is susceptible to Bacitracin disk (left); The right shows resistance

29 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Group B  -Hemolytic Streptococcus ( Staphylococcus agalactiae ) uHas been known to cause mastitis in cattle uColonize the urogenital tract of pregnant women uCause invasive diseases in newborns 4Early-onset infection 4Late-onset disease

30 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Staphylococcus agalactiae : Invasive Infections uEarly-onset infection 4Occurs in neonates who are less than 7 days old neonates 4Vertical transmission of the organism from the mother 4Manifests in the form of pneumonia or meningitis with bacteremia 4Associated with a high mortality rate

31 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Staphylococcus agalactiae : Invasive Infections uLate-onset infection 4Occurs between 1 week and 3 months after birth 4Usually occurs in the meningitis form 4Mortality rate is not as high as early-onset uIn adults 4Occurs in immunosuppressed patients or those with underlying diseases 4Often found in a previously healthy adult who just experienced childbirth

32 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Laboratory Diagnosis: Group B  -Hemolytic Streptococcus uColony morphology  Grayish-white, mucoid, creamy, narrow zone of  - hemolysis uPresumptive Identification tests 4Catalase-negative 4Bacitracin-resistant

33 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Laboratory Diagnosis: Group B  -Hemolytic Streptococcus uPresumptive identification tests 4Bile-esculin-hydrolysis– negative 4Does not grow in 6.5% NaCl 4CAMP-test–positive S. agalactiae shows the arrow- shaped hemolysis near the staphylococcus streak, showing a positive test for CAMP factor

34 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Identification Schema Schema to differentiate Group A and B from other b-hemolytic streptococci

35 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Streptococcus Group D and Enterococcus Species uMembers of the gut flora uAssociated infections 4Bacteremia 4Urinary tract infections 4Wound infections 4Endocarditis

36 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Laboratory Diagnosis: Streptococcus Group D and Enterococcus Species uMicroscopic morphology 4Cells tend to elongate uColony morphology  Most are non-hemolytic, although some may show  or, rarely  hemolysis 4Possess Group D antigen

37 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Laboratory Diagnosis : Streptococcus Group D and Enterococcus Species uIdentification tests 4Catalase: may produce a weak catalase reaction 4Hydrolyze bile esculin 4Differentiate Group D from Enterococcus sp. with 6.5% NaCl or PYR test

38 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Identification Schema Schema to differentiate Enterococcus and Group D streptococci from other nonhemolytic streptococci

39 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Other Streptococcal Species uViridans group 4Members of the normal oral and nasopharyngeal flora 4Includes those that lack the Lancefield group antigen 4Most are  hemolytic but also includes nonhemolytic species 4The most common cause of subacute bacterial endocarditis (SBE)

40 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Streptococcus pneumoniae uGeneral characteristics 4Inhabits the nasopharyngeal areas of healthy individuals 4Typical opportunist 4Possess C substance uVirulence factors 4Polysaccharide capsule  Clinical infections  pneumonia  meningitis  bacteremia 4sinusitis/otitis media

41 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Laboratory Diagnosis: Streptococcus pneumoniae uMicroscopic morphology 4Gram-positive cocci in pairs; lancet-shaped

42 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Laboratory Diagnosis: Streptococcus pneumoniae uColony morphology 4Smooth, glistening, wet-looking, mucoid   -Hemolytic 4CO2enhances growth

43 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Laboratory Diagnosis: Streptococcus pneumoniae uIdentification 4Catalase negative 4Optochin- susceptibility-test– susceptible 4Bile-solubility-test– positive

44 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Identification Schema Schema to differentiate S. pneumoniae from other  - hemolytic streptococci

45 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Streptococcus-Like Organisms uAerococcus 4Gram-positive cocci that tend to form tetrads   -hemolytic; and may resemble viridans group 4May be confused with Enterococcus biochemically

46 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Streptococcus-Like Organisms uLeuconostoc 4Resemble streptococci microscopically; colonies resemble viridans group or Enterococcus  Found in plants, vegetables, and dairy products uPediococcus 4Found in nature; used in bioprocessing and biopreservation of foods such as cheese, meats, and vegetables 4Rarely seen in human infections; has been associated with septicemia

47 W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company. Points to Remember u General characteristics and hemolytic patterns of streptococcal and enterococcal species u Infections produced by pathogenic species u Microscopic and colony morphology u Tests used to identify these species u Emergence of resistant strains


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