cours of staphyloccus and very imprtant

1. STAPHYLOCOCCI
PROF AM KAMBAL

2. Staphylococci
Definition:
Gram +ve cocci in clusters, catalase positive.
Other gram positive cocci include Streptococci and
Micrococci
Differences between Staphylococci, Micrococci and
Streptococci

3. Character Staphylococci Streptococci
(& Micrococci)
Gram Stain Positive Positive
Arrangement Clusters Chains
(Micrococci) in
Fours)
Size Large 1 um Smaller
0.5 – 1 um
Catalase Positive Negative
H2O2 Catalase H2O + O2

4.  Staphylococci are similar to Micrococci in shape
 But Staphylococci can be:
a) Pathogenic
b) Commensals (Normal Flora)
c) Oxidative & fermentative

5. While Micrococci are:
a) Commensal (Normal flora of skin)
b) Only oxidative (Non fermentative)
 Can be differentiated from Staphylococci by oxidation,
fermentation reactions (O – F) test

6. Gram Positive Cocci
In Clusters
Species :
 S.aureus : main pathogen
 S.epidermidis (S.albus) : opportunistic
 S.saprophyticus : UTI

7. Laboratory Characteristics
Morphology:
 Culture: ordinary media,aerobic/ non aerobic, positive
catalase reaction.
Colonies :
 S.aureus : golden yellow-white
 S.epidermidis : white, no pigment
 Both tolerate 5-10 % NaCL.

8. Staphylococci are divided into two main groups:
1) Coagulase +ve 2) Coagulase negative
i.e.
Staphylococcus aureus
a) Staphylococcus epidermidis
b) Staphylococcus saprophyticus

9. Differentiating Tests
 Coagulase test : main test
 S.aureus : coagulase positive
 S. epidermidis and albus : coagulase negative
 Two types of coagulase tests:
 Tube coagulase
 Slide coagulase

10. Coagulase Test
A) Enzyme secreted by Staphylococcus aureus.
B) Differentiate between Staphylococcus aureus and other
Staphylococci
C) Coagulates Plasma Fibrinogen to Fibrin in clot form
D) Tested By:
1. Slide test for bound coagulase or clumping factor
2. Tube test free coagulase test

12. Other Tests
 DNAse test
 Phosphatase test
 Mannitol fermentation
 Novobiocin sensitivity to differentiate between
S.epid. and S. saproph. which is resistant

13. Staphylococci are divided into two main groups:
1) Coagulase +ve 2) Coagulase negative
i.e.
Staphylococcus aureus
a) Staphylococcus epidermidis
b) Staphylococcus saprophyticus

15. Staph. aureus Staph.
epidermidis
Habitat Certain areas All skin
of skin surface
(see diagram)
Colour Mainly golden White
yellow (on Blood
(on Blood agar) agar medium)
Catalase +ve +ve

16. Staph aureus Staph
epidermidis
Coagulase +ve -ve
Dnase +ve -ve
Phosphalase +ve -ve
Growth on Yellow Red
Mannitol salt agar
due to fermentation
of mannitol
Phage typing available Not available
Groups I, II, III
(Continued)

18. Staphylococcus aureus
 Carried by 20 – 50 % of healthy people on the skin
mainly in
a. Nose
b. Axilla
c. Perineum
d. Throat
e. Gut

20. Species Frequency Coagulase Common Human
of Infection Production Habitat
S. aureus Common Positive Anterior nares,
perineum
S. epidermidis Common Negative Anterior nares,
head, axilla,
arms and legs
S.saprophyticus Common Negative Urinary tract
Human Staphylococcal Species most important are:

21. Species Frequency Coagulase Common Human
of infection production habitat
Other species are:
S. hemolyticus Uncommon Negative Axilla, pubes
(apocrine glands)
S. hominis Uncommon Negative Axilla, pubes
(apocrine glands)
S. simulans Uncommon Negative -
S. auricularis Rare Negative Ear canal
S. capitis Rare Negative Scalp, forehead
(sebaceous gland)
S. cobnii Rare Negative -
S. saccharoly- Rare Negative -
ticus
S. warneri Rare Negative -
S. xylosis Rare Negative -

22. Virulence Factors:
A. Toxins and toxic components produced by
Staphylococcus aureus
Toxins Activity
Haemolysins a, B, y and - Cytolytic, lyse erythrocytes of
various animal species
Coagulase Clots Plasma
Fibronolysin Digests fibrin
Leucoccidin Kills leucocytes
Hyaluronidase Breaks down hyaluronic acid
DNAase Hydrolysis DNA

23. Toxins Activity
Lipase Lipolytic (produces opacity in egg-yolk
medium)
Protein A Antiphagocytic
Epidermolytic toxins Epidermal splitting and exfoliation
A and B
Enterotoxin(s) Causes vomiting and diarrhoea
Toxic shock syndrome Shock, rash, desquamation
toxin - 1
Virulence Factors: (Continued)
B. Other virulence factors include:
1. Peptidoglycan of the cell wall
2. Teichoic acid

24. Pathogenecity Or Infections Caused
By: Staph. aureus
1) Superficial Infection
1. Pustules
2. Boils
3. Carbuncles
4. Impetigo
5. Collection of pus
6. Abscesses
7. Wound infection (Hospital Acquired)
8. Paronychia – Infection of nail bud

25.  Toxic epidermal necrocysis
 S.S.S.S. = Staphylococcus Scalded Skin Syndrome
3) Deep Infections
 Septicaemia,
 Endocarditis
 Pyaemia
 Osteomyelitis – Infection of bone
 Pneumonia
2) Skin Exfoliation
 Due to an enterotoxin produced in the food before
ingestion.
 An intoxication not infection
5) Toxic Shock Syndrome
4) Food Poisoning

28. 1l – 1 = Interlukin I
TNF = Tumour necrosis factor

31. Treatment: Drain Pus if any + Antibiotics
Antibiotic Sensitivity (Staphylococcus aureus)
1. Penicillin 95% ®: if sensitive, it is the best drug
2. Flu/Cloxacillin (Methicillin) Drug of choice
3. Fucidic Acidpenetrate well in bones
4. Vancomycin if the organism is resist to
methicillin (MRSA)
5. Erythromycin
6. Clindamycin
7. Rifampicin

32. MRSA = Methicillin Resistant Staphylococcus aureus
MRSA: Also Resistant to Cloxacillin & Flucloxacillin
Treatment For MRSA = Vancomycin
Treatment of Staphylococcus aureus
 95% Resistant to Penicillin so treated by Cloxacillin if
Resistant to Cloxacillin or Methicillin = MRSA = so treat
with Vancomycin.

33. MRSA = Methicillin Resistant Staphylococcus aureus
MRSA: Also Resistant to Cloxacillin & Flucloxacillin
Treatment For MRSA = Vancomycin
Treatment of Staphylococcus aureus
 95% Resistant to Penicillin so treated by Cloxacillin if
Resistant to Cloxacillin or Methicillin = MRSA = so treat
with Vancomycin.

34. M.R.S.A
 Methicillin and cloxacillin resistant S.aureus.
 Due to mec A gene which codes for PBP 2a with
low affinity to beta lactam antibiotics nosocomial
infections.
 Treatment: vancomycin for systemic infections
only.

35. B) Staphylococcus saprophiticus
 It causes urinary tract infection in young female.
Coagulase Negative Staphylococci (it is novobiocin resistant)
The commonest coagulase negative is:
Staph. epidermidis
Pathogenesis:
 They produce very small amounts of toxins.
 Pathogenesis is mainly due to production of (slime) which consists of:
a. Polysaccharide
b. Techoic acid enhanced by presence of fibrinogen.
 This makes them sticky on biomaterial like catheters. Sticky material
called is Biofilm.

36. They Cause:
1. Endocarditis in artificial valves “shunts”.
2. Infections of spitz holter valves connecting brain ventricle
with jugular vein
3. Infection of cannulae
4. Infection of Intravenous catheters
5. Infections of prosthesis
e.g. Artificial valves (heart)
Orthopaedic fixing nails
6. Infection in premature babies (Bacteriaemia)
7. Infection in Oncology patients
8. Staphylococcus saprophyticus causes urinary infection in
young females

37.  Treatment of Coagulase Negative Staphylococci
“Staphylococcus epidermidis” and others :
 Depends on testing antibiotics sensitivity on the isolates
 But Vancomycin is the drug of choice for severe serious
infection