1. Staphylococcus
Asmabanu Shaikh
Tutor
Department of Microbiology
PIMSR

2. What are Staphylococcus
• Sir Alexander Ogston, a Scottish surgeon, first showed in 1880 that a
number of human pyogenic diseases were associated with a cluster-
forming micro-organism. He introduced the name 'staphylococcus’
• (Greek: staphyle = bunch of grapes; kokkos = grain or berry), now
used as the genus name for a group of facultatively anaerobic,
catalase-positive, Gram-positive cocci.

3. Classification
• Family
• Genus
• Species
Micrococcaceae
Micrococcus and Staphylococcus
S. aureus
S. saprophyticus
S. epidermidis
M. luteus

4. The genus Staphylococcus contains about forty
species and subspecies today.
• Only some of them are important as human pathogens:
• Staphylococcus aureus
• Staphylococcus epidermidis
• Staphylococcus hominis
• Staphylococcus haemolyticus
• Staphylococcus saprophyticus
• others

5. Morphology
• Gram-positive cocci, nonmotile,
facultative anaerobes
• Cells occur in grape like clusters
because cells division occurs
along different planes and the
daughter cells remain attached
to one another

6. Pathogenicity and virulence
• Two types of disease:
• Infections
• Intoxications

7. INFECTIONS
• Cocci gain access to damaged skin, mucosal or tissue sites
• Colonise by adhering to cells or extracellular matrix
• Evade host defence mechanisms
• Multiply and cause tissue damage
INTOXICATION
• Caused by bacterial toxins – produced either in the infected host or
preformed in vitro

8. Virulence factors
CELL-ASSOCIATED POLYMERS
• Cell wall polysaccharide peptidoglycan
• Techoic acid – antigenic component of the cell wall
• Capsular polysaccharide
CELL SURFACE PROTEINS
• Protein A (present in most S. aureus strains Biological properties –
chemotactic, anti-phagocytic and anti-complementary effects Induces
platelet damage and hypersensitivity)
• Clumping factor –‘bound coagulase’ (responsible for slide coagulase)

9. EXTRACELLULAR ENZYMES
1) Coagulase (An enzyme that brings about clotting of human or rabbit plasma Acts
with a coagulase reacting factor (CRF) present in plasma Binds to prothrombin
Converts fibrinogen to fibrin Basis of tube coagulase test)
2) Lipid hydrolases or lipases
3) Hyaluronidase
4) Nuclease
5) Protein receptors
Virulence factors

10. Toxins
Cytolytic toxin:
- Membrane active substance.
- Consising of four haemolysins – alpha, beta, gamma, delta and leucocidin.
Enterotoxin :
- Responsible for manifestations of Staphylococcal food poisoning –
nausea, vomiting and diarrhea
-2–6 hours after consuming food contaminated by preformed toxin
- Meat, fish, milk and milk products contaminated with staphylococci, toxin
accumulates
- Source of infection – food handler
- Disease – self-limited
- Tests to detect toxin – ELISA, latex agglutination

11. TOXIC SHOCK SYNDROME TOXIN(TSST) – a potentially fatal
multisystem disease, presenting with fever, hypotension, myalgia, vomiting,
diarrhea, mucosal hyperemia and an erythematous rash
EXFOLIATIVE TOXIN
• Exfoliative (epidermolytic) toxin, also known as ET or ‘exfoliatin’,
responsible for staphylococcal scalded skin syndrome (SSS)
• SSS is an exfoliative skin disease
• The outer layer of the epidermis becomes separated from the underlying
tissues

12. Clinical Manifestations
Skin & Soft tissue infections
• Folliculitis, Furuncle
• Carbuncle, Impetigo
• Mastitis and breast abscess
• Surgical site wound
infections
• Cellulitis

13. Clinical Manifestations...
Musculoskeletal
Infections
• Septic arthritis
• Osteomyelitis
• Pyomyositis in HIV
• Psoas abscess
• Epidural abscess
Respiratory Tract
Infections
• Ventilator associated pneumonia in
adults
• Septic pulmonary emboli
• Post viral pneumonia
• Empyema and Pneumothorax
• Pneumatocele in neonates

14. Bacteremia and its Complications
• Sepsis, septic shock
• Central line associated blood stream infection
• Metastasis - kidney, joints, bone and lung
• Native-valve endocarditis
• Prosthetic-valve endocarditis
• Intravenous drug use associated endocarditis

15. Clinical Manifestations
UTI(Urinary tract
infection)- secondary to
bacteremia
Toxin-Mediated Illnesses
• Toxic shock syndrome
• Food poisoning
• Staphylococcal scalded-
skin syndrome
Infections Associated
with CA-MRSA
• Necrotizing pneumonia
• Purpura fulminans
• Necrotizing fasciitis

16. Epidemiology
• Staphylococci – primary parasites, human beings and animals
• Colonise – skin, skin glands and mucous membranes
• Source of infection – human patients and carriers
• Patients with superficial infections and respiratory infections disseminate large
number of staphylococci into the environment
• Healthy persons
• 10–30% carry staphylococci in the nose
• 5–10% in the vagina
• Colonisation of umbilical stump – common
• Some carriers, called shedders, disseminate large numbers of cocci for prolonged
periods

17. • Staphylococcal disease may follow endogenous or exogenous infection.
• Mode of transmission:
• Contact – direct/fomites
• Dust
• Airborne droplets
Methicillin resistant S.aureus (MRSA)
• Hospital infections – frequency – strains resistant to a variety of
antibiotics
• Post-operative wound infections and hospital cross-infections
• Resistant to all beta lactam antibiotics and other antimicrobial agents

18. OUTBREAK CONTROL MEASURES
• Isolation of patient with open staphylococcal lesion
• Detection of staphylococcal lesions among surgeons, nurses and other
hospital staff and keeping them away from work till lesions heal
• Strict asepsis in operation theatre
• Hand washing – simplest and most effective method
• Search for carriers among hospital staff
• Carriers treated with local application of mupirocin or chlorhexidine

19. LABORATORY DIAGNOSIS.
1) Specimen
2) Microscopy
3) Culture
4) Identification
5) Serological tests

20. LABORATORY DIAGNOSIS..
Infection Specimen
Suppurative lesion Pus, wound swab
Respiratory Infections Sputum
Urinary tract infection Mid stream urine
PUO, Bacteremia Blood
Food poisoning Feces, vomitus, food
Carriers Nasal & perianal swab

21. LABORATORY DIAGNOSIS.
• MICROSCOPY
• Gram staining -Gram positive cocci in
clusters, non capsulated, non sporing.

22. LABORATORY DIAGNOSIS- CULTURE CHARACTERISTICS
• Aerobe, facultative anaerobe, Non-
fastidious
• Nutrient agar – Golden yellow
• Blood agar – beta hemolytic

23. LABORATORY DIAGNOSIS- CULTURE CHARACTERISTICS
• MacConkey agar- Small pink
• Liquid medium - uniform turbidity
• Selective media
- Mannitol salt agar – yellow colonies -mannitol
fermentation 
- Salt milk agar
- Ludlam’s medium

24. Biochemical Tests
 Coagulase test
o Tube coagulase
o Clumping factor
 Heat stable thermo nuclease test
 DNase test
 Phosphatase (also produced by S.epidermidis)
 Golden yellow pigmentation
 Hemolysis on blood agar
 Mannitol fermentation
 Black coloured colonies on potassiumtellurite
agar
 Gelatin liquefaction
 Protein A detection
• S.aureus positive and CONS
mostly negative

25. Catalase test :
Procedure :
• Take clean glass slide
• Put a drop of 3 % hydrogen
peroxide
• Add bacterial colony
• Result: If bubbles is formed,
test is positive

26. Coagulase test :
• Tube coagulase test – detects free coagulase
• 0.1 ml of broth culture added to 0.5 ml of human or rabbit plasma,
positive and negative controls are set up
• Incubated – water bath at 37°C for 3–6 hours
• If positive, plasma clots and does not flow when the tube is tilted

27. TUBE COAGULASE TEST
Tube coagulase test: positive, negative

28. • Slide coagulase test – detects bound coagulase
• The isolate is emulsified in a drop of saline on a slide
• A drop of human or rabbit plasma is added and mixed
• Positive and negative controls are set up
• Prompt clumping indicates a positive test

29. Tube coagulase Slide coagulase
Due to coagulase enzyme Due to clumping factor
Requires CRF in plasma Does not require CRF in
plasma
Done in tube Done in slide
Positive if clot is formed Positive if clumps are
formed
Coagulase enzyme has eight
serotypes
Clumping factor has one
serotype
S.Lugdunensis gives a
negative result
S.Lugdunensis gives a
positive result
Both tube and slide coagulase positive for S.aureus,
S.hyicus, and S.intermedius

30. Antibiotic sensitivity tests –important –drug resistance
Zone of inhibition around antibiotic discs on the lawn culture of test bacteria

31. COAGULASE NEGATIVE
STAPHYLOCOCCUS (CONS)

32. CONS
• Mostly harmless commensals
• Less virulent than S.aureus
• Recently their role as pathogens is increasingly been reported
• Important species:
- S. epidermidis
- S.saprophyticus
- S.lugdunensis
- S.schleiferi

33. STAPHYLOCOCCUS EPIDERMIDIS
• Most common CONS (75-80%)
• Normal flora - skin, oropharynx and vagina
• Risk - prosthetic devices
• Pathogenesis-
- Initial adhesion
- Colonization (Biofilm)

34. STAPHYLOCOCCUS EPIDERMIDIS
• Infections:
- Prosthetic-device related infections endocarditis with insertion of valvular
prosthesis and ventricular shunt infections
- Stitch abscess

35. CoNS..
Staphylococcus saprophyticus
• UTI in sexually active young women
• Unlike other Staphylococci resistant to novobiocin
• S.lugdunensis and S.schleiferi
- Native-valve endocarditis and osteomyelitis

36. Treatment
• Drug resistance – appropriate antibiotic based on antibiotic sensitivity tests
• Benzyl penicillin – most effective if strain is sensitive
• Cloxacillin used against penicillinase-producing strains
• MRSA – resistant to all beta lactum antibiotics
• Life-threatening staphylococcal infections – vancomycin – drug of choice
• Mild superficial infections – topical applications – bacitracin, chlorhexidine or
mupirocin
• Carriers – local application – mupirocin

37. QUESTIONS :
• Describe morphology, culture characteristics and laboratory diagnosis of
Staphylococcus.
• Describe pathogenesity and and laboratory diagnosis of Staphylococcus.
• Full form : MRSA, VRSA, TSST, SSS