Transcript 6-Staphylococci

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
(& Micrococci)
Streptococci
Gram Stain
Positive
Positive
Arrangement
Clusters
(Micrococci) in
Fours)
Chains
Size
Large 1 um
Catalase
Positive
Smaller
0.5 – 1 um
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 :
 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
i.e.
Staphylococcus aureus
2) Coagulase negative
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) 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.
2.
Slide test for bound coagulase or clumping factor
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
i.e.
Staphylococcus aureus
2) Coagulase negative
a) Staphylococcus epidermidis
b) Staphylococcus saprophyticus
Habitat
Staph. aureus
Staph.
epidermidis
Certain areas
of skin
All skin
surface
(see diagram)
Colour
Mainly golden
yellow
(on Blood agar)
Catalase
+ve
White
(on Blood
agar medium)
+ve
(Continued)
Staph aureus
Staph
epidermidis
Coagulase
Dnase
+ve
+ve
-ve
-ve
Phosphalase
+ve
-ve
Growth on
Mannitol salt agar
due to fermentation
of mannitol
Yellow
Red
Phage typing
available
Groups I, II, III
Not available
Staphylococcus aureus
 Carried by 20 – 50 % of healthy people on the skin
mainly in
a.
Nose
b.
Axilla
c.
Perineum
d.
Throat
e.
Gut
Human Staphylococcal Species most important are:
Species
Frequency
Coagulase
of Infection Production
Common Human
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
Species
Frequency
of infection
Other species are:
Coagulase
production
Common Human
habitat
S. hemolyticus
Uncommon
Negative
Axilla, pubes
(apocrine glands)
Axilla, pubes
(apocrine glands)
-
S. hominis
Uncommon
Negative
S. simulans
Uncommon
Negative
S. auricularis
Rare
Negative
S. capitis
Rare
Negative
S. cobnii
Rare
Negative
S. saccharolyticus
Rare
Negative
-
S. warneri
Rare
Negative
-
S. xylosis
Rare
Negative
-
Ear canal
Scalp, forehead
(sebaceous gland)
-
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
Fibronolysin
Leucoccidin
Hyaluronidase
DNAase
Clots Plasma
Digests fibrin
Kills leucocytes
Breaks down hyaluronic acid
Hydrolysis DNA
Virulence Factors: (Continued)
Toxins
Activity
Lipase
Lipolytic (produces opacity in egg-yolk
medium)
Antiphagocytic
Epidermal splitting and exfoliation
Protein A
Epidermolytic toxins
A and B
Enterotoxin(s)
Toxic shock syndrome
toxin - 1
Causes vomiting and diarrhoea
Shock, rash, desquamation
B. Other virulence factors include:
1.
2.
Peptidoglycan of the cell wall
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
2)
Skin Exfoliation
 Toxic epidermal necrocysis
 S.S.S.S. = Staphylococcus Scalded Skin Syndrome
3)
Deep Infections
 Septicaemia,
 Endocarditis
 Pyaemia
 Osteomyelitis – Infection of bone
 Pneumonia
4)
Food Poisoning
 Due to an enterotoxin produced in the food before
ingestion.
 An intoxication not infection
5)
Toxic Shock Syndrome
1l – 1 = Interlukin I
TNF = Tumour necrosis factor
Treatment: Drain Pus if any + Antibiotics
Antibiotic Sensitivity (Staphylococcus aureus)
Penicillin 95% ®: if sensitive, it is the best drug
Flu/Cloxacillin (Methicillin) Drug of choice
Fucidic Acidpenetrate well in bones
Vancomycin
if the organism is resist to
methicillin (MRSA)
5. Erythromycin
6. Clindamycin
7. Rifampicin
1.
2.
3.
4.
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.
2.
3.
4.
5.
6.
7.
8.
Endocarditis in artificial valves “shunts”.
Infections of spitz holter valves connecting brain ventricle
with jugular vein
Infection of cannulae
Infection of Intravenous catheters
Infections of prosthesis
e.g. Artificial valves (heart)
Orthopaedic fixing nails
Infection in premature babies (Bacteriaemia)
Infection in Oncology patients
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