for mbbs 2nd prof

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