Staphylococcus are gram-positive cocci that commonly cause suppuration and infection. The most important species are S. aureus and S. epidermidis. They appear in grape-like clusters under microscopy and are non-motile, non-capsulated, and non-spore forming. They produce toxins like enterotoxins that cause food poisoning and toxic shock syndrome toxin. Staphylococcus cause a variety of infections from superficial skin infections to deep infections like osteomyelitis and sepsis. Diagnosis involves culture and biochemical testing. Treatment involves antibiotics like benzylpenicillin.

1. STAPHYLOCOCCUS
Staphylococci are gram positive cocci arranged in grape like clusters. They are common cause of
suppuration.
SPECIES –
A. Staphylococcus aureus
B. Staphylococcus epidermis
C. Staphylococcus saprophyticus
MORPHOLOGY –
- Staphylococci are gram positive cocci arranged in grape like clusters.
- Non motile
- Non capsulated
- Non sporing
- Diameter – 1 micro meter
CULTURE –
- Avg temp. – 10 to 42 degree c
- Optimal temp. – 37
- They are aerobes and facultative anaerobes
- Nutrient agar – colonies are 2 – 4 mm in diameter, circular, smooth, convex, opaque and
easily imulsifiable and produce yellow pigment
- Blood agar – beta type of haemolysis
- Macconkey’s agar – colonies are very small and pink in colour due to lactose fermentation
- MANNITOL salt agar is a selective medium for isolation of staph. Aureus
Biochemical reaction –
- Catalase - + ve
- Oxidase - - ve
- Coagulase test - + ve in staph. Aureus, - ve in other species
- Mannitol test - + ve in staph. Aureus - ve in other species
- Gelatin liquefaction test – Positive
- Tellurite reduction test - Positive
- It brake down carbohydrate by fermentation
- Producing acid without gas

2. ENZYMES –
1. Coagulase
2. Deoxyribonuclease
3. Phosphtase
ANTIGENIC STRUCTURE –
1. Capsule
2. Peptidoglycan
3. Teichoic acid
4. Protein A (for diagram p.no. – 179 )
TOXINS –
1. HAEMOLYSINS – four antigenecially distinct types are produced by staphylococci.
- Alpha lysin
- Beta lysin
- Gamma lysin
- Delta lysin
2. LEUCOCIDIN – it is composed of two components slow (S) and fast (F). it damage
polymorphonuclear leucocytes and macrophages.
3. ENTEROTOXIN – it is responsible for staphylococcal food poisoning – nausea, vomiting and
diarrhoea occurring within 2 – 6 hours of consuming contaminated food. Nine ( A,B,C1, C2,
C3, D, E, H, I) enterotoxins are identified. It is detected by ELISA and latex agglutination test.
4. TOXIC SHOCK SYNDROME TOXIN (TSST) – It is characterized by fever, hypotension,
vomiting, diarrhoea and an erythematous rash with subsequent desquamation and
hyperaemia of mucous membrane.
5. EXFOLIATIVE TOXIN – A & B two types of toxins are present. A is heat stable while B is heat
labile. Control of A is chromosomal and control of B is plasmid mediated. They cause
epidermal splitting resulting in blistering diseases. It may lead to staphylococcal scalded skin
syndrome (SSSS). Severe form of SSSS is known as ritter’s disease.
PATHOGENESIS –
1. CUTANEOUS INFECTION – superficial infection include pustules, boils, carbuncles,
abscesses, styes, impetigo, wound and burn infections.
2. DEEP INFECTIONS – it include osteomyelitis, tonsillitis, pharyngitis, sinusitis, pneumonitis,
empyema, septicemia, bacteriaemia & pyaemia.

3. 3. FOOD POISONING - Nausea, vomiting and diarrhoea occurring within 2 – 6 hours of
consuming contaminated food.
4. NOSOCOMIAL INFECTION – they are important cause of hospital acquired infection.
5. SKIN EXOFOLIATIVE DISEASE - They cause epidermal splitting resulting in blistering diseases.
It may lead to staphylococcal scalded skin syndrome (SSSS). Severe form of SSSS is known as
ritter’s disease.
6. TOXIC SHOCK SYNDROME - It is characterized by fever, hypotension, vomiting, diarrhoea
and an erythematous rash with subsequent desquamation and hyperaemia of mucous
membrane.
LAB DIAGNOSIS –
1. SPECIMENS –
PUS - SUPPURATIVE LESIONS
SPUTUM - RESPIRATORY INFECTIONS
BLOOD - SEPTICEMIA Or PUO
URINE - URINARY TRACT INFECTIONS
CSF - MENINGITIS
FAECES - FOOD POISONING
FOOD or VOMIT - FOOD POISONING
2. COLLECTION & TRANSPORT – Specimen collected in sterile container.
3. DIRECT MICROSCOPY - Gram positive cocci arranged in grape like clusters.
4. CULTURE –
- Blood agar
- Peptone water
- Salt agar
- Salt milk agar
- Robertson’s cooked meat agar
5. COLONY MORPHOLOGY AND GRAM STAINING – SEE ABOVE
6. BIOCHEMICAL REACTIONS – SEE ABOVE
7. BACTERIOPHAGE TYPING – For epidemiological purpose.
8. Antibiotic susceptibility – it is determined by stokes method or Kirby bauer method.
TREATMENT – BENZYL PENICILIN