STAPHYLOCOCCI PROF AM KAMBAL

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

Character Staphylococci Streptococci (& Micrococci) Gram StainPositivePositive ArrangementClustersChains (Micrococci) in Fours) SizeLarge 1 umSmaller 0.5 – 1 um CatalasePositiveNegative H 2 O 2 CatalaseH 2 O + O 2

  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 :  S.aureus : main pathogen  S.epidermidis (S.albus) : opportunistic  S.saprophyticus : UTI

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.

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

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

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

Other Tests  DNAse test  Phosphatase test  Mannitol fermentation  Novobiocin sensitivity to differentiate between S.epid. and S. saproph. 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. aureusStaph. epidermidis Habitat Certain areasAll skin of skinsurface (see diagram) ColourMainly goldenWhite yellow (on Blood (on Blood agar) agar medium) Catalase+ve+ve

Staph aureusStaph epidermidis Coagulase+ve-ve Dnase+ve-ve Phosphalase+ve-ve Growth onYellowRed Mannitol salt agar due to fermentation of mannitol Phage typingavailable Not available Groups I, II, III (Continued)

Staphylococcus 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 NegativeAxilla, pubes (apocrine glands) S. hominis Uncommon NegativeAxilla, 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 CoagulaseClots Plasma FibronolysinDigests fibrin LeucoccidinKills leucocytes HyaluronidaseBreaks down hyaluronic acid DNAaseHydrolysis DNA

Toxins Activity LipaseLipolytic (produces opacity in egg-yolk medium) Protein AAntiphagocytic Epidermolytic toxins Epidermal splitting and exfoliation A and B Enterotoxin(s)Causes vomiting and diarrhoea Toxic shock syndromeShock, rash, desquamation toxin - 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) 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 I TNF = 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 Acidpenetrate well in bones 4.Vancomycinif 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.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.

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.

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

  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