1. GRAM POSITIVE COCCI & RODS
CLASSIFICATION:
(A) Cocci, divided into:
Catalase positive : Staphylococcus
Catalase negative : Streptococcus
& anaerobic cocci

2. (B) Rods (bacilli), divided into:
Branching, divided into:
a) Aerobic : Nocardia,
Streptomyces, Actinomadura.
b) Anaerobic : Actinomyces.

3. 2. Non-branching divided :
a) Anaerobic : Clostridium
b) Aerobic : divided into:
(i) Catalase negative : Loctobacillus,
Gardnerella, Erysipelothrix.
(ii) Catalase positive : divided into:
@ Sporing, e.g.: Bacillus
@ Non-sporing : Listeria,
Corynebacterium

4. STAPHYLOCOCCUS SPECIES: S. aurous, main pathogenic species.
2. S. epidermidis.
3. S. saprophyticus.

5. (40% of healthy people carry S. aureus).
NORMAL HABITAT:
*Skin,* intestinal tract,
* upper respiratory
tract, * nose
(40% of healthy people carry S. aureus).

6. PATHOGENICITY: 1- Abscess, boils, styes, impetigo.
2- Secondary infection to: insect
bites, ulcers, burns, wound .
3- Conjunctivitis (newborn).
4- Hospital cross-infection.

7. 5- Septicaemia, endocarditis,
osteomyelitis.
6- Pneumonia, empyema.
7- Mastitis.
8-Antibiotic-associated enteritis
9- Food poisoning : secretion of
enterotoxin (B) in contaminated
meat, milk, & milk products.

8. 10- Scalded skin syndrome in
young children (release of
exfoliatin toxin).
11- Toxic shock syndrome,
(colonization of vagina,
other parts of body).

9. ENZYMES AND TOXINS 1-Coagulase enzyme: clots
plasma & prevents phagocytosis
2- Leucocidin: destroy WBC .
3- Lytic exotoxin: destroys RBC
and platelets.
4- Deoxyribonuclease enzyme :
destroys DNA.

10. 5- Hyaluronidase enzyme,
helps spread in tissues.
6- Lipase enzyme, breaks
down fats.
7- Staphylokinase enzyme,
causes fibrinolysis.

11. 8- Exfoliatin, causes scalded
skin syndrome (skin peeling)
9- Enterotoxin B, causes food
poisoning.
10- Beta-lactamase enzyme,
destroys Beta-lactam ring,
leads to penicillin resistance.

12. S. epidermidis : May cause @ Bacteraemia, due to : @ contamination of
* cannulae, shunts,
* indwelling catheters

13. S. SAPROPHYTICUS: Associated with : @ Cystitis. @ Pyelonephritis.
@ Acute urethritis (women)

14. LABORATORY DIAGNOSIS
SPECIMENS:
Pus & sputum for microscopy
and culture.
2. Blood for culture.
3. Stool, vomit, remains of food,
(food poisoning)
4. Nasal swabs (carriers)

15. MICROSCOPY:
@ Staphylococci :
* non-motile,
* non-capsulated,
* gram positive,
* 1 µm in diameter,
* occur: cluster, pairs, single

16. @ Aerobic , anaerobic , carboxyphilic, S. aureus: use:
CULTURE:
@ Aerobic , anaerobic , carboxyphilic,
S. aureus: use:
Blood agar & chocolate agar: colonies
yellow-cream, golden, white, 1-2 mm,
raised, may be Beta-haemolytic.
b) Mc Conkey :colonies 0.5 mm,
lactose not fermented.
c) Mannitol salt agar: To isolate
S. aureus from stool in food poisoning.

17. 2. S.epidermidis: 3. S. saprophyticus: @ Same media of S.aureus
@ Colonies white, non-haemolytic.
3. S. saprophyticus:
@ Same above media.
@ Colonies white or yellow, non-
haemolytic.
@ Does not grow anaerobicaly,
or on Mc Conkey agar.

18. BIOCHEMICAL REACTIONS:
@ S.aureus:
1-Coagulase: identifies pathogenic strains
2-DNAse test: if coagulase is not clear.
3-Catalase test: Staph. catalase positive
4-Most Staph. strains ferment mannitol
5-S.aureus grows on 15-25% NaCl media

19. S.epidermidis & saprophyticus:
Coagulase negative.
DNAse negative.
Catalase positive.
Grow on mannitol salt agar.
S. saprophiticus ferments
mannitol + acid production .
6. S. epidermidis does not
ferment mannitol.

20. COAGULASE TEST: Bound: detected by slide
S. aureus has 2 types of coagulase:
Free: detected by tube
Bound: detected by slide
@ Slide coagulase test is confirmed
by tube test if:
Slide is negative & S. aureus is
isolated from a very ill patient
b) Slide is not clear.

21. SLIDE METHOD:
Put a saline drop on each end of a slide
Mix a colony on each saline drop to
make a thick suspension.
Colonies are taken from B.A. or N.A.
3. Add a drop of plasma to one suspension. Mix, look for clumping within 10 sec.
second suspension is a negative control.
4. Control Strains:
a) S.aureus: Positive control.
b) E.coli: Negative control.

22. TUBE METHOD: Plasma is diluted 1:10 in saline . Label 3 test tubes:
T = Test organism
Pos = Positive control
Neg = Negative control (E.coli )
2. Pipette 0.5 ml plasma into each tube.
3. Add 5 drops of test organism to tube (T)
3. Add 5 drops of positive control to tube (Pos)
4. Add 5 drops of negative control to tube (Neg).
5. Mix, & incubate all tubes at 37˚C.
Look for clotting after one hour.
No clotting, check tubes every ½ hr for 6 hrs.

23. Positive: organism hydrolysed DNA in medium
DNAse Test:
Culture organisms on media containing DNA.
Divide the DNA plate into 3 parts:
a) Test organism is streaked on part (1).
b) Positive control is streaked on part (2).
c) Negative control is streaked on part (3).
Incubate overnight at 37˚C.
Flood plate with HCl & pour off excess.
Note clear zones around colonies within 5 min
Results: @ Positive DNAse: Clear
@ Negative DNAse: Not clear
Positive: organism hydrolysed DNA in medium
7. Controls: Positive : S.aureus -Negative : E. coli

24. Catalase Test:
Take colonies from a medium not containing blood (catalase is in RBC). Use nutrient agar
Place 2ml H2O3 solution in test tube.
Use a wood stick (not wire), to mix colonies with hydrogen perioxide solution.
Note appearance of O2 bubbles.
Controls:
Positive: Staph. species.
Negative: Strep. species.

25. BACTERIOPHAGE TYPING:
@ To study:
* epidemiology of hospital
cross-infection
* food poisoning sources of
infection
@ S. aureus strains producing
enterotoxin belong to phage
Group III.

26. Penicillin, Methicilin, Cephalosporin
SENSITIVITY
@ Sensitive to:
Flucloxacillin, Cephalosporin, Fucidin, Clindamycin, Penicillin, Erythromycin, Lincomycin.
Resistance to:
Penicillin, Methicilin, Cephalosporin