Method for rapid typification of microorganisms and set of reagents used

1. A process for rapid bacterial typing by Pulsed Field Gel Electrophoresis (PFGE) performed in 7 to 13 hours and including the separation of bacterial DNA restriction fragments by electrophoresis in minichambers of CHEF (Contour Clamped Homogeneous Electric Field) system, electrophoresis performed in 1.5% agarose gels and 0.5×TBE buffer (44.5 mM Tris, 44.5 mM Boric Acid, 1 mM EDTA, pH 8.3); process wherein the improvement comprises a step for preparing, in agarose miniplugs, intact and immobilized DNA molecules from bacterial cells of the species Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus , wherein said step of preparation further comprises steps of:

i) washing, embedding and incubating the bacterial cells and the DNA molecules in a plurality of lytic and protease enzymes-free solutions, composed by chemical reagents; wherein said solutions are:

(1) NaCl salt, at a concentration of 0.15M, and the metal chelating agent EDTA, at a concentration of 0.01M and pH 8.0;

(2) NaCl salt at a concentration of 0.15M;

(3) low melting agarose at a concentration of 1.5% suspended in NaCl solution at a concentration of 0.15M;

(4) low melting agarose at a concentration of 1.5% suspended in the solution that contains NaCl salt at a concentration of 0.15M and the metal chelating agent EDTA at a concentration of 0.01M and pH 8.0;

(5) the metal chelating agent EDTA at a concentration of 0.1M, two anionic detergents Sarkosyl and Nonidet P-40 both at a concentration of 1%, and 0.01M Tris base, pH 8.0;

(6) the metal chelating agent EDTA at a concentration of 0.1M, the two anionic detergents Sarkosyl and Nonidet P-40 both at a concentration of 1%, 0.01M Tris base, and 4M Urea, pH 9.5;

(7) the metal chelating agent EDTA at a concentration of 0.1M and 0.01M Tris base, pH 8.0;

ii) embedding said bacterial cells in agarose miniplugs by means of a flexible and sterilizable mold which has a lid and various square depressions stamped in one of its surfaces; mold that is flexible enough to be bent for detaching said miniplugs from it and is reusable after its sterilizing; and

iii) casting in the mold said agarose miniplugs containing cells of one of said bacterial species, detaching said miniplugs from the mold, and incubating and washing the miniplugs with the solutions composed by chemical reagents.

2. The process of claim 1 , wherein said Pseudomonas aeruginosa cells are grown in broth and collected by centrifugation for said preparation of the agarose-embedded intact DNA molecules.

3. The process of claim 1 , wherein said Pseudomonas aeruginosa cells are grown in plates and collected by washing said plates for the preparation of the agarose-embedded intact DNA molecules.

4. The process of claim 1 , wherein said Staphylococcus aureus cells are grown in plates and collected by washing said plates for the preparation of the agarose-embedded intact DNA molecules.

5. The process of claim 1 , wherein said Escherichia coli cells are grown in broth and collected by centrifugation for said preparation of the agarose-embedded intact DNA molecules.

6. The mold of claim 1 , wherein said mold sheet comprises silicone, rubber or any other flexible material.

7. The process of claim 1 , wherein said lid for covering the mold is made of glass.

8. The process of claim 1 , wherein the embedding of said bacterial cells in the agarose miniplugs, by means of using the flexible and sterilizable mold and its lid, comprises the following steps:

i) pouring the suspension of the bacterial cells and agarose onto the stamped surface of the mold;

ii) distributing said suspension evenly with a spatula to fill said depressions;

iii) covering the mold with its lid and led to set until the miniplugs are formed; and

iv) bending the mold onto a flask to detach the miniplugs.

9. The process of claim 1 , wherein the washing of Escherichia coli cells is done with said solution (1) containing 0.15M NaCl and 0.01M EDTA, pH 8.0.

10. The process of claim 1 , wherein the washing of Staphylococcus aureus cells is done with said solution (1) containing 0.15M NaCl and 0.01M EDTA, pH 8.0.

11. The process of claim 1 , wherein the washing of Pseudomonas aeruginosa cells is done with said solution (2) containing 0.15M NaCl.

12. The process of claim 1 , wherein the embedding of Pseudomonas aeruginosa cells is done with said solution (3) containing 1.5% low melting temperature agarose suspended in 0.15M NaCl.

13. The process of claim 1 , wherein the embedding of Escherichia coli cells is done with said solution (3) containing 1.5% low melting temperature agarose suspended in 0.15M NaCl.

14. The process of claim 1 , wherein the embedding of Staphylococcus aureus cells is done with said solution (4) containing 1.5% low melting temperature agarose suspended in 0.15M NaCl and 0.01M EDTA, pH 8.0.

15. The process of claim 1 , wherein the incubating of the miniplugs containing Escherichia coli cells is done with said solution (5) containing 0.1M EDTA, 1% Sarcosyl, 1% Nonidet P-40 and 0.01M Tris base, pH 8.0.

16. The process of claim 1 , wherein the incubating of the miniplugs containing Escherichia coli cells is done with said solution (6) containing 0.1M EDTA, 1% Sarcosyl, 1% Nonidet P-40, 0.01M Tris base and 4M Urea, pH 9.5.

17. The process of claim 1 , wherein the incubating of the miniplugs containing Pseudomonas aeruginosa cells is done with said solution (6) containing 0.1M EDTA, 1% Sarcosyl, 1% Nonidet P-40, 0.01M Tris base and 4M Urea, pH 9.5.

18. The process of claim 1 , wherein the incubating of the miniplugs containing Staphylococcus aureus cells is done with said solution (6) containing 0.1M EDTA, 1% Sarcosyl, 1% Nonidet P-40, 0.01M Tris base and 4M Urea, pH 9.5.

19. The process of claim 1 , wherein the washing of the miniplugs containing the intact and immobilized DNA molecules of Pseudomonas aeruginosa is done with said solution (6).

20. The process of claim 1 , wherein the washing of the miniplugs containing the intact and immobilized DNA molecules of Staphylococcus aureus is done with said solution (7) containing 0.1M EDTA and 0.01M Tris base, pH 8.0.

21. The process of claim 1 , wherein the storing of the miniplugs containing the intact and immobilized DNA molecules of Pseudomonas aeruginosa is done with said solution (7) containing 0.1M EDTA and 0.01M Tris base, pH 8.0.

22. The process of claim 1 , wherein said sterilizable mold comprises a sheet having the square depressions stamped in one of its surfaces, wherein said depressions are of 0.3 cm in size and from 0.03 to about 0.1 cm in depth, depressions into which the suspension of agarose-bacterial cell mix solidifies and provides miniplugs of said sizes.

23. The mold of claim 22 , wherein said sheet comprises silicone, rubber or like flexible material, and comprises up to 49 identical square depressions stamped in one of its surfaces.

24. The process of claim 1 , wherein said step of preparation, in the agarose miniplugs, of said intact and immobilized DNA molecules from Pseudomonas aeruginosa cells comprises the steps of:

i) collecting said cells from broth or plates followed by washing the cells in the solution (2) containing 0.15M NaCl;

ii) embedding of said cells in the solution (3) containing 1.5% low melting temperature agarose suspended in 0.15M NaCl and pouring the suspension onto said flexible mold;

iii) incubating the miniplugs, after they are formed, for 30 minutes at 50° C. in the solution (6) containing 0.1M EDTA, 1% Sarcosyl, 1% Nonidet P-40, 0.01M Tris base and 4M Urea, pH 9.5; and

iv) washing said miniplugs twice at 50° C. for 10 minutes in the solution (7) containing 0.1M EDTA and 0.01M Tris base, pH 8.0, and further storing them in said solution.

25. The process of claim 24 , wherein said collecting of the cells in the step of preparation, in the agarose miniplugs, of the intact and immobilized DNA molecules from the Pseudomonas aeruginosa cells is done by centrifugation of the suspension of said cells grown in broth.

26. The process of claim 24 , wherein said collecting of the cells in the step of preparation, in the agarose miniplugs, of the intact and immobilized DNA molecules from the Pseudomonas aeruginosa cells grown in plates is done by washing the plates with the solution (2) containing 0.15M NaCl and further centrifuging the cell suspension.

27. The process of claim 1 , wherein the preparation of the intact and immobilized DNA molecules from the Staphilococcus aureus cells has the steps of:

i) collecting said cells from plates by washing the plates with the solution (1) containing 0.15M NaCl and 0.01M EDTA, pH 8.0, and washing said cells in said solution;

ii) embedding said cells in the solution (4) containing 1.5% low melting temperature agarose suspended in 0.15M NaCl and 0.01M EDTA, pH 8.0 and pouring the cell suspension onto the flexible mold;

iii) incubating the miniplugs, after they are formed, for 60 minutes at 50° C. in the solution (6) containing 0.1M EDTA, 1% Sarcosyl, 1% Nonidet P-40, 0.01M Tris base and 4M Urea, pH 9.5; and

iv) washing said miniplugs twice at 50° C. for 10 minutes in the solution (7) containing 0.1M EDTA and 0.01M Tris base, pH 8.0.

28. The process of claim 1 , wherein the preparation of the intact and immobilized DNA molecules from the Staphilococcus aureus cells has the steps of:

i) collecting said cells from plates by washing the plates with the solution (1) containing 0.15M NaCl and 0.01M EDTA, pH 8.0, and washing said cells in said solution;

ii) preincubating said cells for 30 minutes at 50° C. in the solution (6) containing 0.1M EDTA, 1% Sarcosyl, 1% Nonidet P-40, 0.01M Tris base and 4M Urea, pH 9.5, diluting fivefold the cell suspension with the solution (7) containing 0.1M EDTA and 0.01M Tris base, pH 8.0 and further collecting the preincubated cells by centrifugation;

iii) embedding said preincubated cells in the solution (4) containing 1.5% low melting temperature agarose suspended in 0.15M NaCl and 0.01M EDTA, pH 8.0 and pouring the cell suspension onto the flexible mold; and

iv) washing the miniplugs, after they are formed, twice at 50° C. for 10 minutes in the solution (7) containing 0.1M EDTA and 0.01M Tris base, pH 8.0.

29. The process of claim 1 wherein said step of preparation, in the agarose miniplugs, of the intact and immobilized DNA molecules from Escherichia coli cells is done according to the steps of:

i) collecting said cells from broth followed by washing the cells in the solution (1) containing 0.15M NaCl and 0.01M EDTA, pH 8.0;

ii) embedding said cells in the solution (3) containing 1.5% low melting temperature agarose suspended in 0.15M NaCl and pouring the suspension onto the flexible mold;

iii) incubating the miniplugs, after they are formed, for 10 minutes at 37° C. in the solution (5) containing 0.1M EDTA, 1% Sarcosyl, 1% Nonidet P-40 and 0.01M Tris base, pH 8.0; and

iv) incubating said miniplugs for 30 minutes at 50° C. in the solution (6) containing 0.1M EDTA, 1% Sarcosyl, 1% Nonidet P-40, 0.01M Tris base and 4M Urea, pH 9.5.

30. A process for rapid bacterial typing by Pulsed Field Gel Electrophoresis (PFGE) performed in 7 to 13 hours and including the separation of bacterial DNA restriction fragments by electrophoresis in minichambers of CHEF (Contour Clamped Homogeneous Electric Field) system, wherein the improvement comprises a step for preparing, in agarose miniplugs, intact and immobilized DNA molecules from bacterial cells of the species Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus , wherein said step of preparing further comprises the steps of:

i) washing, embedding and incubating the bacterial cells and the DNA molecules in a plurality of lytic and protease enzymes-free solutions, wherein said solutions are:

(1) NaCl and the metal chelating agent EDTA at pH 8.0;

(2) NaCl at a concentration of 0.15M, without the metal chelating agent EDTA;

(3) low melting agarose suspended in a NaCl solution;

(4) low melting agarose suspended in a NaCl solution and further comprising the metal chelating agent EDTA at pH 8.0;

(5) the metal chelating agent EDTA and two anionic detergents at pH 8.0;

(6) the metal chelating agent EDTA, the two anionic detergents and Urea at pH 9.5; and

(7) the metal chelating agent EDTA, at pH 8.0.

ii) embedding said bacterial cells in agarose miniplugs by means of a flexible and sterilizable mold which has a lid and various square depressions stamped in one of its surfaces; mold that is flexible enough to be bent for detaching said miniplugs from it and is reusable after its sterilizing; and

iii) casting in the mold said agarose miniplugs containing cells of one of said bacterial species, detaching said miniplugs from the mold, and incubating and washing the miniplugs with the solutions composed by chemical reagents.

31. The process of claim 30 , wherein one of the two variants for preparing, in the agarose miniplugs, the intact and immobilized DNA molecules from the Staphylococcus aureus cells has the steps of:

i) collecting said cells from plates by washing the plates with the solution (1), and washing said cells in said solution;

ii) embedding said cells in the solution (4) and pouring the cell suspension onto the flexible mold;

iii) incubating said miniplugs for 60 minutes at 50° C. in the solution (6); and

iv) washing said miniplugs twice at 50° C. for 10 minutes in the solution (7).

32. The process of claim 30 , wherein one of the two variants for preparing the agarose miniplugs, the intact and immobilized DNA molecules from the Staphylococcus aureus cells has the steps of:

i) collecting said cells from plates by washing the plates with the solution (1) containing 0.15M NaCl and 0.01M EDTA, pH 8.0, and washing said cells in said solution;

ii) embedding said cells in the solution (4), and pouring the cell suspension onto the flexible mold;

iii) incubating said miniplugs for 60 minutes at 50° C. in the solution (6); and washing said miniplugs in the solution (7).