1. Staphylococcus-Streptococcus-Enterococcus

2. Gr + cocci ~ 21 genera Common features Spherical shape
Gram stain reaction
Absence of endospores
Catalase activity subdividing
Catalase positive genera Staphylococcus Micrococcus
Stomatococcus
Alloiococcus
Catalase negative genera Streptococcus
Enterococcus

3. Staphylococcus Gram positive Grow pattern cluster of grapes
single cells, pairs, short chains
Nonmotile
Aerobic or facultatively anaerobic
Catalase-positive
Grow in 10 % NaCl o C

4. Most common Staph. causing diseases
S. aureus
S. epidermidis
S. saprophyticus
S. capitis
S. haemolyticus
Produce coagulase
Coagulase negative staphylococcus

5. Micrococcus Can be confused with CN staphs
Differ in that, they grow only aerobically
Resistant to lizostafin and furazolidone
Isolation of micrococcus in clinical samples
Contamination ?

6. Stomatococcus Alloiococcus
Stomatococcus mucilaginosus
Only species in this genus
Infection in the immunocompromised host
Alloiococcus otitidis
Only species in this genus
Aerobic Gr +
Disease??

7. Staphylococcus and their diseases
S. aureus
Toxin-mediated
Food poisoning
Toxic shock syndrome, scalded skin syndrome
Cutaneous
Impetigo
Folliculitis
Furuncles
Carbuncles, wound infections

8. Staphylococcus and their diseases
S. aureus
Others
Bacteremia
Endocarditis,
Pneumoniae
Empyema
Osteomyelitis
Septic arthritis

9. Staphylococcus and their diseases
S. epidermidis
Bacteremia
Endocarditis,
Surgical wounds
Urinary tract infections
Opportunistic infections of catheters,
shunts, prostetic devices and peritoneal dialysates

10. Staphylococcus and their diseases
S. saprophyticus
Urinary tract infections
Opportunistic infections
Resistant to novobiocin

11. Staphylococcus/physiology & structure
Capsule
Peptidoglycan
Teichoic acids
Protein A
Coagulase and other sutface proteins
Cytoplasmic membrane

12. Staphylococcus/capsule
Loose-fitting
Polysaccharide layer (slime layer)
In vitro rare

13. Staphylococcus/peptidoglycan
Half of the cell wall
More rigide compared to Gr negatives
Endotoxin-like activity
Endogenous pyrogenes
Activation of complement
Production of int-1 from monocytes
Aggregation of polymorphonuclears

14. Staphylococcus/teichoic acids
Teichoic & lipoteichoic acid
Polysaccharide A in S. aureus
Polysaccharide B in S. epidermidis
Mediate the attachment of staphs to mucosal surfaces
Poor immunogens (except when bound to peptidoglycan)

15. Staphylococcus/protein A
The surface of most S. aureus is coated with protein A (not CNS)
Affinity to bind Fc receptor of IgG1, IgG2 & IgG4 prevents the antibody-mediated immune clearence of the bacteria

16. Staphylococcus/coagulase & other surface proteins
S. aureus clumping factor (bound coagulase)
Collagen-binding protein adherence to
Elastin-binding protein host tissues
Fibronectin-binding protein

17. Staphylococcus/pathogenesis & immunity
Toxins
&
Enzymes

18. Staphylococcus/toxins
Alpha toxin
Beta toxin
Delta toxin
Gamma toxin & Panton-Valentine Leukocidin
Exfoliative toxins
Enterotoxins
Toxic shock syndrome toxin-1

19. Staphylococcus/toxins
a Toxin important mediator of tissue damage in staphylococcal diseases
toxic for many cells (erythrocytes, leukocytes, hepatocytes,..)
produced by most strains of S. aureus

20. Staphylococcus/toxins
b Toxin sphingomyelinase C
toxic for many cells role in tissue destruction & abscess formation produced by most strains of S. aureus

21. Staphylococcus/toxins
d Toxin wide spectrum of cytolytic activity detergent-like activity produced by most strains of S. aureus

22. Staphylococcus/toxins
g Toxin & Panton-Valentine Leukocidin composed of two polypeptide chains toxic for many cells

23. Staphylococcus/toxins
Exfoliative toxins staphylococcal scalded skin syndrome (SSSS) exfoliative dermatitis two types: ETA & ETB produced by 5 to 10 % of all S. aureus strains

24. Staphylococcus/toxins
Enterotoxins 8 serologically distinct enterotoxins exist (A-E, G-I) stable to heating
resistant to gastric & jejunal enzymes produced by 30 to 50 % of all S. aureus strains are superantigens

25. Staphylococcus/toxins
Toxic shock syndrome toxin-1
heat & proteolysis resistant all S. aureus responsible for menstruation-associated TSS produce TSST % of the strains responsible for other forms of TSS produce TSST-1 superantigens

26. Staphylococcus/enzymes
Coagulase
Catalase
Hyaluronidase
Fibrinolysin
Lipases
Nuclease
Penicillinase

27. Staphylococcus/enzymes
Coagulase
S. aureus
2 forms
Bound
free

28. Staphylococcus/enzymes
Catalase
“All staphylococci produce catalase”
H2O2 (toxic) H2O O2

29. Staphylococcus/enzymes
Hyaluronidase
Hydrolyzes hyaluronic acids facilitates the spread of S aureus in tissues
> 90 % of S. aureus produce hyaluronidase

30. Staphylococcus/enzymes
Fibrinolysine
Staphylokinase
All S. aureus
Dissolve fibrine clots

31. Staphylococcus/enzymes
Lipases
All S. aureus & 30 % of the CNS produce several different lipases
Nuclease
A marker for S. aureus
Penicillinase (b-lactamase)

32. Staphylococcus/IDENTIFICATION
Microscopy
Culture:
Nutritionally enriched agar media with sheep blood
Selective agar media for S. aureus with 7.5 % NaCl + mannitol
Aerobic and anaerobic
Large, smooth colonies
Identification
Positive coagulase, heat-stable nuclease, alkaline phosphatase, mannitol ferment. S. aureus

33. Streptococcus Gram positive Grow pattern pairs, chains
Most species are facultatively anaerobes
Some grow only in atmosphere enhanced with CO2
Nutritional requirements are complex
Blood, serum
“Catalase-negative”

34. Streptococcus Classification is complicated
3 different schemes are used
Lancefield groupings according to serologic properties (A-H, K-M, O-V)
Hemolytic patterns: b, a & g hemolysis
Biochemical properties

35. Streptococci and their diseases
S. pyogenes (group A)
Pharyngitis,
scarlet fever,
pyoderma,
erysipelas,
cellulitis,
necrotizing fasciitis,
streptococcal toxic shock syndrome,
bacteremia,
rheumatic fever,
glomerulonephritis

36. Streptococci and their diseases
S. agalactiae (group B)
Neonatal infections (meningitis, pneumoniae, bacteremia)
Urinary tract infections
Amnionitis,
Endometritis
Wound infections

37. Streptococcus pyogenes/physiology & structure
Spherical cocci
Form short (clinical specimen) or long chains (liquid media)
Grow on enriched blood agar media
White colonies 1-2 mm with large zones of b-hemolysis
Encapsulated strains mucoid
Basic structure in the cell wall is peptidoglycan as Staphs group spec. Ag

38. Streptococcus pyogenes/physiology & structure
Group specific carbohydrate
Within the cell wall
10 % of the dry weight
Is used to classify group A streptococci and distinguish them from others

39. Streptococcus pyogenes/physiology & structure
Type specific proteins
M protein major type-specific protein associated with virulent streptococci
2 polypeptide chains
Highly conserved among all ggroup A streptococci
Responsible for the antigenic variability >80 serotypes
T protein (trypsin-resistant) secondary
Usefull when bacteria fail to express the M protein

40. Streptococcus pyogenes/physiology & structure
Other cell surface components
M-like proteins
Lipoteichoic acid
F protein
Capsule (hyaluronic acid)

41. Streptococcus pyogenes/Pathogenesis&Immunity
Virulence of S. pyogenes
The ability of the bacteria
to adhere to the surface of the host cells
Invade into the epithelial cells
Avoid opsonization & phagocytosis
Produce a variety of toxins & enzymes

42. Streptococcus pyogenes/Pathogenesis&Immunity
Pyrogenic exotoxins
(Streptococcal pyrogenic exotoxin, Spes)
Produced by lysogenic strains
Superantigens
Responsible for the streptococcal toxic shock syndrome

43. Streptococcus pyogenes/Pathogenesis&Immunity
Streptolysin S & O
Streptolysine S lyse erythrocytes
leukocytes
platelets
responsible for b-hem.
Streptolysine O lyse erythrocytes
antibodies are formed against ASO test

44. Streptococcus pyogenes/Pathogenesis&Immunity
Streptokinases
A & B
Lyse blood clots
Used in medicine
Deoxyribonucleases
A to D
Depolymerase free DNA in pus reduce viscosity
C5a peptidase
Hyaluronidase,diphosphopyridine nucleotidase

45. Streptococcus pyogenes/IDENTIFICATION
Microscopy
Culture:
Proper collection of throat swab specimen
Nutritionally enriched agar media with sheep blood
Selective media (media with “bactrim”)
Identification
Table 23-4

46. Streptococcus agalactiae (Group B)
The only species that carries the group B antigen
physiology & structure
Gr + cocci
Short or long chains (indistinguishable from S. pyogenes)
Buttery colonies, narrow zone of b-hem.
Subdividing
The B antigen group specific
Capsular polysaccharides type-specific
C protein (surface protein)

47. Streptococcus agalactiae/IDENTIFICATION
Microscopy
Culture:
Readily grow on a nutritionally enriched medium
Large colonies
b-hemolysis may be absent selective broth medium with antibiotics
Identification
Preliminary identification (+) CAMP test, hydrolysis of hippurate

48. Other beta-hemolytic streptococci
Group C, F and G are most commonly associated with human disease
2 species of particular importance
S. anginosus
S. dysgalactiae

49. Viridans Streptococci
a-hemolytic and nonhemolytic streptococci
Produce green pigment on blood agar media
Require complex media supplemented with blood products and 5-10 % CO2 atmsp.

50. Streptococcus pneumoniae
Encapsulated, Gr + coccus
Lancet-shaped cells, in pairs or short chains
a-hemolytic
Can grow only on enriched media (with blood products)
Catalase (-)
Capsule, classified accr. to polysaccharides
90 serotypes
Capsular polysaccharides are used in vaccines
Teichoic acid C polysaccharide (CRP)

51. S. pneumoniae / diseases
Meningitis
Sinusitis
Otitis media
Bacteremia

52. Streptococcus pneumoniae/Pathogenesis&Immunity
The disease manifestations are caused primarily by the host response to infection

53. Streptococcus pneumoniae/Pathogenesis&Immunity
Colonization & migration
S.pn colonizes the oropharynx
Can spread to the lungs, paranasal sinuses, middle ear, blood stream
By means of:
Surface protein adhesins, secretory IgA (sIgA) protease, pneumolysin

54. Streptococcus pneumoniae/Pathogenesis&Immunity
Tissue destruction
Mobilization of inflamatory cells characteristic of pneumococcal infections
Teichoic acid
Peptidoglycan fragments
Pneumolysin
H2O2 production
Phosphorylcholin
Phagocytic survival
Capsule
Pneumolysin mediated suppression of the phagocytosis

55. Streptococcus pneumoniae/IDENTIFICATION
Microscopy
Lancet-shaped, Gr (+) diplococci, unstained capsule (Gram stain with “quellung” reaction)
Culture:
Enriched supplemented medium with blood
Selective medium with gentamicin
Identification
Bile solubility test
Optochin

56. Enterococcus
Most frequently isolated & most commonly responsible for human disease with streptococcus among gram-positive cocci
“enteric cocci”
Possess the group D cell wall antigen
16 species in the genus
E. faecalis & E. faecium are most commonly isolated

57. Enterococcus/physiology & structure
They can not be differentiated from S. pneumoniae in microscope
Facultatively anaerobic
Optimal growth temp.= 35 oC (10oC to 45oC)
White, large colonies on blood agar (after 24h)
Nonhemolytic (or a or b-hemolysis)
Grow in the presence of
6.5 % NaCl, tolerate 40 % bile salts, hydrolyse esculin

58. Enterococcus/Pathogenesis&Immunity
Are commensal with limited potential for causing disease
Do not possess toxins
Cannot avoid being engulfed & killed by phagocytic cells
BUT,
Cause
Serious
Disease

59. Enterococcus/Pathogenesis&Immunity
Virulence factors
Adhesive factors
Bacteriocins
Inherently resistant to many antibiotics

60. Enterococcus/Clinical Diseases
Can cause life-threatening infections
One of the most feared nosocomial pathogens 10% of all nos. infct.
Most commonly involved sites
Urinary tract
Blood stream
A sever complication: endocarditis( following bacteremia)

61. Enterococcus/Laboratory diagnosis
Grow readily on nonselective media
Resemble S. pneum.
Differentiation resistant to optochin
don’t dissolve when exposed to bile
hydrolyze PYR pyrolidonyl-b-naphthylamide