Staphylococcus is a common cause of skin infections in humans. Staphylococcus aureus is an important pathogenic species. It is gram-positive, catalase-positive, and produces coagulase. S. aureus causes a variety of infections, including skin and soft tissue infections like boils and abscesses. It can also cause pneumonia, osteomyelitis, toxic shock syndrome, and food poisoning. Laboratory diagnosis involves culturing specimens on blood agar and performing tests like the coagulase test and mannitol fermentation. Treatment involves antibiotics like penicillin, cloxacillin, or vancomycin for resistant strains.

1. STAPHYLOCOCCUS
 Gram positive cocci arranged in grape like
clusters
 Commonest cause of localized suppurative
lesions in humans
 Habitat includes skin ,hair,anterior nasal area
 Imp sps- S.aureus,
S.epidermidis,S.saprophyticus etc

2. Staphylococcus aureus
MORPHOLOGY
 Gram poitive ,Arranged in grape like
clusters,Non motile, Non sporing, Non
capsulated
 1 micrometer in diameter

3. STAPHYLOCOCCUS

4. CULTURAL CHARACTERS
 Grow readly on ordinary media
 Temp range-10-42 degree Celsius,
Optimum-37
 Ph-7.4-7.6
 They are aerobes and facultative anaerobes
 Common media are Nutrient agar & Blood
agar

5. On Nutrient agar
 2-4mm diameter colony.circular ,smooth
,convex ,Most strains produce golden yellow
pigment

6. Colonies of staphylococcus aureus

7. On Blood agar
 Produce beta hemolytic colonies

8. Colonies of staphylococcus albus

9. Colonies of staphylococcus cetreus

10. Colonies on biood agar

11.  Selectivemedia is Mannitol salt agar
 Produce yellow colonies on mannitol salt
agar

12. Selective media-mannitol salt agar

13. Biochemical propertis
 Catalase +
 Oxidase –
 Coagulase +

14. Following properties are imp to
distigush S.aureus from other non
pathogenic sps
 Coagulase production
 Mannilol fermentation
 Golden yellow pigment
 Liquefy gelatin
 Phosphatase production
 DNase production

15. ANTIGENIC STRUCTURE &
VIRULANCE FACTORS
ANTIGENIC STRUCTURE
Capsule
 Some strains have a capsule. That inhibit phagocytosis, they
inhibit opsonisation
 Capsulated strains are more virulent
Peptidoglycan
 Give rigidity to the cell wall, activtes compliment
Teichoic acid
 Major antigenic component
 Protect cell from compliment mediated opsonisation
Protein A
 It has chemotactic,antiphagocytic & anti complimentary action

17. TOXINS & ENZYMES
Staph aureus produce a number of toxins &
extra cellular enzymes
TOXINS
1. Cytolytic toxin
2. Entero toxin
3. Toxic shock syndrome toxin
4. Exfoliative(epidrmolytic toxin)

18. CYTOLYTIC TOXIN
2 Types HEMOLYSIN & LEUCOCIDINS
HEMOLYSIN
 Lyse RBCs
 4 types ie, alpha, beta ,gamma & delta
LEUCOCIDINS
 Damage polymorphonuclear lecocytes

19. ENTERO TOXIN
 Responsible for staphylococcal food
poisoning
 Nosiea,vomitting & diarrhea in 2-6 hrs after
consumption of contaminated food
 Meat ,fish ,milk & milks products are the main
foods responsible for this condition
 Source of infection is a food handler who is a
carrier.

20. TOXIC SHOCK SYNDROME
TOXIN
 Causing toxic shock syndrome
 It is a fatal multi system disease with fever
,hypotension,myalgia,vomitting, diarrhea,
erythematous rashes etc
 It is potentially a a fatal diasease

21. Exfoliative (epidermolytic)
toxin
 Responsible for staphylococcal scaled skin
disease
 Here the outer layer of epidermis gets
separated from the underlying tissue

22. ENZYMES
COAGULASE
 It is the most important enzyme which brings the clotting of
human or rabbit plasma
 2 types of coagulase engyme-
 Bound coagulase-which is bound to the cell wall
 Free coagulase-which is liberated free in to the surrounding
medium
 This enzyme can be demonstrated by COAGULASE TEST
 Coagulase test is the standard criteria for the identification of
Staph aureus
 SLIDE Test (For bound coagulase) & TUBE Test(for free
coagulase) are there

23. Other enzymes
 Lipases
 Hyaluronidase
 Nuclease

24. STAPHYLOCOCCAL DISEASES
Skin & soft tissue infections
 Folliculitis
 Furancles(boils)
 Wound infections
 Brest abscess
 Carbuncles
 Cellulitis
 Styes

25. CARBUNCLES

26. Multiple carbuncles

27. Abscess

28. Wound infection

29. cellulitis

30. faurancles

31. boils

32. styes

33. Brest abscess

34. impetigo

35. MUSCULOSKELETAL
INFECTIONS
 Osteomyelitis
 Arthritis etc

36. osteomyaliytis

37. RESPIRATORY INFECTIONS
 Tonsillitis
 Pharyngitis
 Sinusitis
 Otis
 Broncho npneumonia
 Lung abscess
 Empyemia

38. Lung abscess

39. tonsillitis

40. CNS INFECTIONS
 Brainabscess
 Meningitis etc

41. meningitis

42. Endo vascular infections
 Bacteremia
 Septicemia
 Pyemia
 Endocarditis
URINARY INFECTIONS
 Staph are uncommon in UTI, but may cause
infections in association with lacal
instrumentation, implants or diabetes

43. TOXIN ASSOCIATED DISEASES

44. Food poisoning

45. Toxic shock syndrome

46. Scaled skin disease

47. Staphylococcal infections

48. LAB DIAGNOSIS
SPECIMENS
Specimens are to be depend on the type of lesions
1. Pus(suppurative lesions)
2. Sputum(respiratory infections)
3. Blood(endo vascular)
4. CSF(CNS infections)
5. Urine (UTI)
6. Feces,vomit,remains of suspected food(food
poisoning)
7. Nasal swab(carriers)

49. METHODS
Direct microscopy
Smears of material shows gram positive cocci
in clusters
Culture
Inoculated on to BLOOD AGAR ,NUTRIENT
AGAR etc
Look for typical colony
morphology,hemolysis,pigmentation etc

50. BICHEMICHAL REACTIONS
 Catalase - positive
 Oxidase - negative
 Coagulase -positive
 DNase -positive
 Phosphatase - positive
 Mannitiol fermentation -positve

51. COAGULASE TEST
 Itis the main lab test used to differenciate
staph aureus from other sps of
 2 types –slide test & tube test
Slide coagulase test
Few colonies are emulsified in a drop of normal
saline on a slide and mixed with a drop of
rabbit or human plasma.
Clumping indicates positive reaction

52. Slide coagulase test

53. TUBE COAGULASE test
 Done to detect free coagulase
 0.1 ml broth culture of the isolate is added to
0.5 ml of human or rabbit plasma in a narrow
test tube.
 The tubes incubated at 37 degree Celsius for
3-6 hrs
 If positive ,the plasma clots & does not flow
when the tube is tilted

54. Tube coagulase test

55. Mannitol fermentation

56. tretment
 Benzyl penicillin is most effective
 Methicillin ,cloxacillin etc can be used in
penicillinase producing strains
MRSA(Methicillin resistant staph aureus)
They are causing grate problem to clinicians
They are resistant to penicillins & other beta lactam
antibiotics
They can be treated by vancomycin &teicoplanin
Treatment of carriers by local application of
antibiotics like as bacitracin