STAPHYLOCOCCISTAPHYLOCOCCI

PROF AM KAMBALPROF AM KAMBAL

StaphylococciStaphylococci

Definition:Gram +ve cocci in clusters, catalase positive.

Other gram positive cocci include Streptococci and MicrococciDifferences between Staphylococci, Micrococci and Streptococci

Character Staphylococci Streptococci (& Micrococci)

Gram Stain Positive Positive

Arrangement Clusters Chains(Micrococci) in Fours)

Size Large 1 um Smaller0.5 – 1 um

Catalase Positive Negative

H2O2 Catalase H2O + O2

Staphylococci are similar to Micrococci in shape But Staphylococci can be:

a) Pathogenic

b) Commensals (Normal Flora)

c) Oxidative & fermentative

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

Gram Positive Cocci In Clusters

Species :Species : S.aureusS.aureus : main pathogen : main pathogen S.epidermidisS.epidermidis ( (S.albusS.albus) : opportunistic) : opportunistic S.saprophyticusS.saprophyticus : UTI : UTI

Laboratory Characteristics

Morphology:Morphology: Culture: ordinary media,aerobic/ non aerobic, Culture: ordinary media,aerobic/ non aerobic,

positive catalase reaction.positive catalase reaction.

Colonies :Colonies : S.aureus S.aureus : golden yellow-white: golden yellow-white S.epidermidis S.epidermidis : white, no pigment: white, no pigment Both tolerate 5-10 % NaCL.Both tolerate 5-10 % NaCL.

Staphylococci are divided into two main groups:

1) Coagulase +ve 2) Coagulase negative

i.e.

Staphylococcus aureus

a) Staphylococcus epidermidis

b) Staphylococcus saprophyticus

Differentiating TestsDifferentiating Tests

Coagulase test : main testCoagulase test : main test S.aureusS.aureus : coagulase positive : coagulase positive S. epidermidisS. epidermidis and albus : coagulase negative and albus : coagulase negative Two types of coagulase tests:Two types of coagulase tests:

Tube coagulaseTube coagulase Slide coagulaseSlide coagulase

Coagulase TestCoagulase 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

Other TestsOther Tests

DNAse testDNAse test Phosphatase testPhosphatase test Mannitol fermentationMannitol fermentation

Novobiocin sensitivity to differentiate between Novobiocin sensitivity to differentiate between S.epid.S.epid. and and S. saproph.S. saproph. which is resistant which is resistant

Staphylococci are divided into two main groups:

1) Coagulase +ve 2) Coagulase negative

i.e.

Staphylococcus aureus

a) Staphylococcus epidermidis

b) Staphylococcus saprophyticus

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

Staph aureus Staph

epidermidis

Coagulase +ve -ve

Dnase +ve -ve

Phosphalase +ve -ve

Growth on Yellow RedMannitol salt agardue to fermentationof mannitol

Phage typing available Not available Groups I, II, III

(Continued)

Staphylococcus aureusStaphylococcus aureus

Carried by 20 – 50 % of healthy people on the skin mainly in

a. Nose

b. Axilla

c. Perineum

d. Throat

e. Gut

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:

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 -

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 PlasmaFibronolysin Digests fibrinLeucoccidin Kills leucocytesHyaluronidase Breaks down hyaluronic

acidDNAase Hydrolysis DNA

Toxins ActivityLipase Lipolytic (produces opacity in egg-

yolk medium)

Protein A Antiphagocytic

Epidermolytic toxins Epidermal splitting and exfoliation

A and B

Enterotoxin(s) Causes vomiting and diarrhoeaToxic shock syndrome Shock, rash, desquamationtoxin - 1

Virulence Factors: (Continued)

B. Other virulence factors include:

1. Peptidoglycan of the cell wall

2. Teichoic acid

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

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

1l – 1 = Interlukin ITNF = Tumour necrosis factor

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 Acid penetrate well in bones

4. Vancomycin if the organism is resist to methicillin (MRSA)

5. Erythromycin

6. Clindamycin

7. Rifampicin

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.

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.

M.R.S.AM.R.S.A

Methicillin and cloxacillin resistant Methicillin and cloxacillin resistant S.aureus.S.aureus. Due toDue to mec A gene mec A gene which codes for PBP which codes for PBP 2a2a with with

low affinity to beta lactam antibiotics nosocomial low affinity to beta lactam antibiotics nosocomial infections.infections.

TreatmentTreatment: vancomycin for systemic infections : vancomycin for systemic infections only.only.

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. Polysaccharideb. Techoic acid enhanced by presence of fibrinogen.

This makes them sticky on biomaterial like catheters. Sticky material called is Biofilm.

They Cause:

1. Endocarditis in artificial valves “shunts”.2. Infections of spitz holter valves connecting brain ventricle

with jugular vein3. Infection of cannulae4. Infection of Intravenous catheters5. Infections of prosthesis

e.g. Artificial valves (heart) Orthopaedic fixing nails

6. Infection in premature babies (Bacteriaemia)7. Infection in Oncology patients8. Staphylococcus saprophyticus causes urinary infection in

young females

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