A novel approach for high-level expression and purification of GST-fused highly thermostable Taq DNA polymerase in Escherichia coli.

Polymerases are enzymes that synthesize long chains or polymers of nucleic acids, including DNA or RNA of nucleotides. They assemble to copy the template nucleic acids DNA or RNA strand using the base-pairing interactions. One of the polymerase enzyme, Taq DNA polymerase, originally isolated from Thermus aquaticus (Taq) is an enzyme widely used in molecular biology so far. The properties of thermostable enzymes has contributed majorly to specificity, automation, and efficacy of the polymerase chain reaction (PCR), making it a powerful tool for molecular biology research today throughout the world.

Purification of Taq DNA polymerase from the original host results in low yields, labor and time consumption. Therefore, much research has been done before to get this enzyme using an alternative host. So far, all of the existing methodology is more laborious, time consuming and requires a heavy cost. We use a new approach to purifying the enzyme with relatively high efficiency, yield and minimum time consumption using Escherichia coli (E. coli) as an alternative host. We cloned 2500 base pairs of DNA Taq polymerase gene into pGEX-4T-1 vector containing GST-tag, downstream of tac promoter and expressed using isopropyl β-D-1-thiogalactopyranoside (IPTG) as an inducer

The enzyme was purified using chromatography efficient new approach and use in routine PCR tests in our laboratory. Our findings suggest a new approach to facilitate the availability of polymerases for molecular and diagnostic studies. In the future, may be used for purification of other recombinant peptides or proteins used in structural biology and proteomics research-based.

 A novel approach for high-level expression and purification of GST-fused highly thermostable Taq DNA polymerase in Escherichia coli.
A novel approach for high-level expression and purification of GST-fused highly thermostable Taq DNA polymerase in Escherichia coli.

Outside Chelation: EDTA binds Closely Taq DNA Polymerase, Mutt and dUTPase and direct Inhibiting Activity dNTPase.

EDTA is commonly used as a metal ion chelator efficient enzyme cofactor. It is highly soluble, optically inactive and do not interfere with most chemicals used in making standard buffer EDTA common options for generating metal-free conditions for biochemical and biophysical investigations. However, controversy in the literature about the activity of the metal-free enzyme is achieved by using EDTA or otherwise called our attention to the alleged effects of external EDTA chelation. Here, we show that EDTA compete for sites of hydrolases dUTPase nucleotide nucleotide binding by developing a network of interactions within the active site similar to the substrate. To reach these findings, we apply the kinetics and molecular docking technique uses two different dUTPases.

Furthermore, we directly measured the binding of EDTA to dUTPases and two other dNTPases, Taq polymerase and Mutt using isothermal titration calorimetry. EDTA binds proven exothermic and enthalpy driven primarily by submicromolar dissociation constant is much lower than with an enzyme: substrate or Mg: EDTA complex. Control of protein, including ATPase, do not interact with EDTA. Our findings indicate that EDTA can act as a selective inhibitor of the enzyme hydrolysis of dNTPs and urges a rethinking of the use of EDTA in enzymatic trial.

Taq DNA Polymerase (Mg2+ plus Buffer)

P101-02 5000 U
EUR 231.6

Taq DNA Polymerase (Mg2+ plus Buffer)

P101-03 10000 U
EUR 290

Taq DNA Polymerase (Mg2+ free Buffer)

P102-01 1000 U
EUR 145.2

Taq DNA Polymerase (Mg2+ free Buffer)

P102-02 5000 U
EUR 231.6

Taq DNA Polymerase (Mg2+ free Buffer)

P102-03 10000 U
EUR 314.4

Taq DNA Polymerase with dNTP Mix Buffer

11140015-1 500 Unit (s) Ask for price

Taq DNA Polymerase with dNTP Mix Buffer

11140015-2 2500 Unit (s) Ask for price

Taq DNA Polymerase with dNTP Mix Buffer

11140015-3 5000 Unit (s) Ask for price

HotStart Taq DNA Polymerase (Mg2+ Plus Buffer)

RK20601 25 U Ask for price

Taq Polymerase (5U/µl)

MBT060A-1000U 1 unit
EUR 62.03
Description: Taq Polymerase (5U/µl)

Taq Polymerase (5U/µl)

MBT060A-5000U 1 unit
EUR 241.01
Description: Taq Polymerase (5U/µl)

Taq Polymerase (5U/µl)

MBT060A-500U 1 unit
EUR 41.58
Description: Taq Polymerase (5U/µl)

Taq DNA Polymerase (Mg2+ plus Buffer, with dNTP)

P101-d1 1000 U
EUR 163.2

Taq DNA Polymerase (Mg2+ plus Buffer, with dNTP)

P101-d2 5000 U
EUR 320.4

Taq DNA Polymerase (Mg2+ plus Buffer, with dNTP)

P101-d3 10000 U
EUR 490.8

Taq DNA Polymerase (Mg2+ free Buffer, with dNTP)

P102-d1 1000 U
EUR 163.2

Taq DNA Polymerase (Mg2+ free Buffer, with dNTP)

P102-d2 5000 U
EUR 320.4

Taq DNA Polymerase (Mg2+ free Buffer, with dNTP)

P102-d3 10000 U
EUR 490.8

Taq DNA Polymerase (5U/uL)

A1003-500U 500U
EUR 26.4
Description: Biotechnology

Taq DNA Polymerase, 5u/ul

B0089(D0089) 5X200U
EUR 112.2

Taq Polymerase / Labeling Buffer

PCR-201L 5x 200units
EUR 230.7
Description: Thermus aquaticus, recombinant, E. coli

Taq Polymerase / Labeling Buffer

PCR-201S 200units
EUR 57.6
Description: Thermus aquaticus, recombinant, E. coli

HotStart Taq DNA Polymerase (5U/uL)

A4144-250U 250U
EUR 66
Description: Biotechnology

Taq Plus DNA Polymerase, 5u/ul

D0090 200U
EUR 94.8

Taq DNA Polymerase with dNTP Mix, 10X Mg free Buffer and 25mM MgCl2

11140016-1 500 Unit(s)
EUR 108.39

Taq DNA Polymerase with dNTP Mix, 10X Mg free Buffer and 25mM MgCl2

11140016-2 2500 Unit(s)
EUR 490.36

Taq DNA Polymerase with dNTP Mix, 10X Mg free Buffer and 25mM MgCl2

11140016-3 5000 Unit(s)
EUR 912.79

Taq DNA Polymerase, 5 units/µl

ABP-PP-ERTQ001 1000U Ask for price

Taq DNA Polymerase, 5 units/µl

ABP-PP-ERTQ100 100U Ask for price

Taq DNA Polymerase, 5 units/µl

ABP-PP-ERTQ200 200U Ask for price

Taq DNA Polymerase, 5 units/µl

ABP-PP-ERTQ500 500U Ask for price

3G HotStart Taq DNA Polymerase (5u/ul)

3GHST81 5x500U
EUR 896.24

Taq DNA Polymerase (High Purity), 5u/ul

HTD0078 5X200U
EUR 129.6

AtMax Taq DNA Polymerase (2.5U/µl), 200U

PL4201 each Ask for price

AtMax Taq DNA Polymerase (2.5U/µl), 500U

PL4202 each Ask for price

Chromo Taq DNA Polymerase (1U/µl), 200U

PL1205 each Ask for price

Chromo Taq DNA Polymerase (1U/µl), 500U

PL1206 each Ask for price

DNA Polymerase Reaction Buffer

abx461036-1096tests 10 × 96 tests Ask for price

DNA Polymerase Reaction Buffer

abx461036-596tests 5 × 96 tests Ask for price

DNA Polymerase Reaction Buffer

abx461036-96tests 96 tests
EUR 562.5

Pfu DNA Polymerase (5U/µl), 100U

PL5201 each Ask for price

Pfu DNA Polymerase (5U/µl), 500U

PL5202 each Ask for price

AtTaq DNA Polymerase (5U/µl), 200U

PL3201 each Ask for price

AtTaq DNA Polymerase (5U/µl), 500U

PL3202 each Ask for price

MaxTaq DNA Polymerase (5U/µl), 200U

PL2201 each Ask for price

MaxTaq DNA Polymerase (5U/µl), 500U

PL2202 each Ask for price

Long-Taq DNA Polymerase (5U/uL)

A4186-250U 250U
EUR 66
Description: Biotechnology

Taq DNA Polymerase

EQ005 100μl/500U
EUR 50

Taq DNA Polymerase

G009 1000 U (200 ul)
EUR 20
Description: Taq DNA Polymerase is a highly thermostable DNA Polymerase that catalyzes the 5’-3’ synthesis of DNA. This polymerase has 5’-3’ exonuclease activities, lacks 3’-5’ exonuclease activity, and produces 3’-dA-tailed amplicons. PCR products made with Taq can be used with TA cloning vectors.

Taq DNA polymerase

BT10101 500U
EUR 96
Description: High quality Taq polymerase for different PCR variations and downstream applications.

Taq DNA polymerase

BT10102 1000U
EUR 130.8
Description: High quality Taq polymerase for different PCR variations and downstream applications.

Taq DNA polymerase

BT10103 2000U
EUR 200.4
Description: High quality Taq polymerase for different PCR variations and downstream applications.

Taq DNA Polymerase

BA00103 500U
EUR 104.4
Description: High quality Taq polymerase for different PCR variations and downstream applications.

Taq DNA Polymerase

BA00104 1000U
EUR 147.6
Description: High quality Taq polymerase for different PCR variations and downstream applications.

Taq DNA Polymerase

BA00105 2500U
EUR 278.4
Description: High quality Taq polymerase for different PCR variations and downstream applications.

Taq DNA Polymerase

9001-2500 each
EUR 614.4

Taq DNA Polymerase

9001-500 each
EUR 229.2

Taq DNA Polymerase

L7051001 1000 unit
EUR 167

Taq DNA Polymerase

L7051200 200 unit
EUR 43

Taq DNA Polymerase

MB101-0500 500 U/100 μl
EUR 10

Taq DNA Polymerase

abx299725-100g 100 µg Ask for price

Taq DNA Polymerase

abx299725-20g 20 µg
EUR 337.5

Taq DNA Polymerase

abx299725-50g 50 µg Ask for price

Taq DNA Polymerase

abx461029-1096tests 10 × 96 tests
EUR 1787.5

Taq DNA Polymerase

abx461029-596tests 5 × 96 tests
EUR 1062.5

Taq DNA Polymerase

abx461029-96tests 96 tests
EUR 362.5

Taq Polymerase(3U/µl)

MBT060B-1000U 1 unit
EUR 73.68
Description: Taq Polymerase(3U/µl)

Taq Polymerase(3U/µl)

MBT060B-5000U 1 unit
EUR 286.42
Description: Taq Polymerase(3U/µl)

Taq Polymerase(3U/µl)

MBT060B-500U 1 unit
EUR 49.43
Description: Taq Polymerase(3U/µl)

Taq Polymerase(3U/µl)

MBT060C-1000U 1 unit
EUR 73.68
Description: Taq Polymerase(3U/µl)

Taq Polymerase(3U/µl)

MBT060C-5000U 1 unit
EUR 286.42
Description: Taq Polymerase(3U/µl)

Taq Polymerase(3U/µl)

MBT060C-500U 1 unit
EUR 49.43
Description: Taq Polymerase(3U/µl)

Taq Polymerase(1U/µl)

MBT060D-1000U 1 unit
EUR 73.68
Description: Taq Polymerase(1U/µl)

Taq Polymerase(1U/µl)

MBT060D-5000U 1 unit
EUR 286.42
Description: Taq Polymerase(1U/µl)

Taq Polymerase(1U/µl)

MBT060D-500U 1 unit
EUR 49.43
Description: Taq Polymerase(1U/µl)

Taq Polymerase(1U/µl)

MBT060E-1000U 1 unit
EUR 73.68
Description: Taq Polymerase(1U/µl)

Taq Polymerase(1U/µl)

MBT060E-5000U 1 unit
EUR 286.42
Description: Taq Polymerase(1U/µl)

Taq Polymerase(1U/µl)

MBT060E-500U 1 unit
EUR 49.43
Description: Taq Polymerase(1U/µl)

h-Taq DNA Polymerase with dNTP Mix 10X Mg Free Buffer and 25mM MgCl

11140022-1 250 Unit (s) Ask for price

h-Taq DNA Polymerase with dNTP Mix 10X Mg Free Buffer and 25mM MgCl

11140022-2 1000 Unit (s) Ask for price

Vazyme LAmp DNA Polymerase (Mg2+ plus buffer)

P301-01 125 U
EUR 145.2

Vazyme LAmp DNA Polymerase (Mg2+ plus buffer)

P301-02 500 U
EUR 210

Taq DNA Polymerase (3000U)

9K-001-0002 3000U
EUR 582

Taq DNA Polymerase (6000U)

9K-001-0033 6000U
EUR 1234.5

Taq DNA Polymerase (1000U)

9K-001-0035 1000U
EUR 418.62

Taq DNA Polymerase (500U)

9K-001-0001 500U
EUR 209.29

TM Taq DNA Polymerase

TBS4010 1000 U
EUR 60

Taq HS DNA Polymerase

P132-d1 500 U
EUR 47.85

Taq HS DNA Polymerase

P132-d2 1,000 U
EUR 89.18

Taq HS DNA Polymerase

P132-d3 5,000 U
EUR 406

Taq DNA Polymerase (PCR)

G008 5000 U (1.0 ml)
EUR 246

Taq DNA Polymerase (PCR)

G126 10000 U (2 x 1.0 ml)
EUR 370.8

Taq DNA Polymerase Mix

abx461043-1096tests 10 × 96 tests Ask for price

Taq DNA Polymerase Mix

abx461043-596tests 5 × 96 tests
EUR 1062.5

Taq DNA Polymerase Mix

abx461043-96tests 96 tests
EUR 337.5

Taq DNA polymerase (-dNTPs)

02-011 200U
EUR 168
Description: The Taq DNA polymerase (-dNTPs) is available in Europe and for worldwide shipping via Gentaur.

Taq DNA polymerase (-dNTPs)

02-011-5 5×200U
EUR 261.6
Description: The Taq DNA polymerase (-dNTPs) is available in Europe and for worldwide shipping via Gentaur.

Taq DNA polymerase (+dNTPs)

02-001 200U
EUR 183.6
Description: The Taq DNA polymerase (+dNTPs) is available in Europe and for worldwide shipping via Gentaur.

Taq DNA polymerase (+dNTPs)

02-001-5 5×200U
EUR 308.4
Description: The Taq DNA polymerase (+dNTPs) is available in Europe and for worldwide shipping via Gentaur.

Taq DNA Polymerase, 5units/㎕

T2200-050 500units
EUR 157.2

Taq DNA Polymerase, 5units/㎕

T2200-100 2x500 units
EUR 230.4

Taq DNA Polymerase, 5units/㎕

T2200-200 4x500 units
EUR 375.6

Maximo Taq DNA Polymerase

S101 500 units
EUR 55.2

Maximo Taq DNA Polymerase

S102 5x500 units
EUR 128.4

Maximo Taq DNA Polymerase

S103 20x500 units
EUR 393.6

Hotstart Taq DNA Polymerase

L7052001 1000 units
EUR 595

Hotstart Taq DNA Polymerase

L7052250 250 units
EUR 167

Taq DNA Polymerase -1000 units

3243 1000units
EUR 115
Description: Intact Genomics Taq DNA Polymerase is a thermostable DNA polymerase that possesses a 5´→3´ polymerase activity (1, 2) and a 5´ flap endonuclease activity (3, 4). This product is supplied with 10x PCR reaction buffer, containing MgCl2, which produces a final Mg2+ concentration of 1.5 mM. Ideal for primary extension reaction with DNA fragments having dA overhang on 3’ ends.Product Includes:Taq DNA Polymerase10x PCR Buffer with Mg2+5x Magic Enhancer

Champagne Taq DNA Polymerase

P122-d1 500 U (2.5 U/μl)
EUR 212.4

Champagne Taq DNA Polymerase

P122-d2 500 U (5 U/μl)
EUR 212.4

Champagne Taq DNA Polymerase

P122-d3 500 U (10 U/μl)
EUR 212.4

ACTaq? Taq DNA Polymerase, 1000U

E2100-1000U each
EUR 260.4

Taq DNA Polymerase - 5,000 units

3245 1/EA
EUR 449
Description: Intact Genomics Taq DNA Polymerase is a thermostable DNA polymerase that possesses a 5´→3´ polymerase activity (1, 2) and a 5´ flap endonuclease activity (3, 4). This product is supplied with 10x PCR reaction buffer, containing MgCl2, which produces a final Mg2+ concentration of 1.5 mM. Ideal for primary extension reaction with DNA fragments having dA overhang on 3’ ends.Product Includes:Taq DNA Polymerase10x PCR Buffer with Mg2+5x Magic Enhancer

Recombinant Taq Dna Polymerase

27079806 EACH
EUR 607.62

Taq DNA Polymerase (Recombinant)

22060707-1 1,000 Unit(s)
EUR 137.27

Taq DNA Polymerase (Recombinant)

22060707-2 1500 Unit(s)
EUR 182.1

Taq DNA Polymerase (Recombinant)

22060707-3 5000 Unit(s)
EUR 465.77

Taq DNA Polymerase (Recombinant)

22060707-4 10 KU
EUR 840.96

Recombinant Taq DNA Polymerase

7-03634 1,000U Ask for price

Recombinant Taq DNA Polymerase

7-03635 3,000U Ask for price

Recombinant Taq DNA Polymerase

7-03636 10,000U Ask for price

Taq DNA Polymerase (Recombinant)

abx073521-10000U 10000 U
EUR 710.4

Taq DNA Polymerase (Recombinant)

abx073521-1000U 1000 U
EUR 276

Taq DNA Polymerase (Recombinant)

abx073521-3000U 3000 U
EUR 393.6

Taq DNA Polymerase Recombinant

rAP-1062 Inquiry Ask for price

ACTaq? Taq DNA Polymerase, 250U

E2100-250U each
EUR 122.4

Taq Plus DNA Polymerase

P201-01 250 U
EUR 147.6

Taq Plus DNA Polymerase

P201-02 1000 U
EUR 213.6

Taq Plus DNA Polymerase

P201-03 3000 U
EUR 382.8

Vazyme LAmp DNA Polymerase (Mg2+ plus buffer, with dNTP)

P301-d1 125 U
EUR 147.6

Vazyme LAmp DNA Polymerase (Mg2+ plus buffer, with dNTP)

P301-d2 500 U
EUR 213.6

Vazyme LAmp DNA Polymerase (Mg2+ free buffer, with dNTP)

P302-d1 125 U
EUR 147.6

Vazyme LAmp DNA Polymerase (Mg2+ free buffer, with dNTP)

P302-d2 500 U
EUR 213.6

Taq Plus DNA Polymerase (Taq Plus DNA) Protein

abx073522-100tests 100 tests
EUR 225

Hot start Taq DNA Polymerase

EQ006 100μl/500U
EUR 200

Hot Start Taq DNA Polymerase

abx460010-1096tests 10 × 96 tests Ask for price

Hot Start Taq DNA Polymerase

abx460010-596tests 5 × 96 tests Ask for price

Hot Start Taq DNA Polymerase

abx460010-96tests 96 tests
EUR 262.5

Genorise® Taq DNA Polymerase

GR108007 200 tests
EUR 230

YEA taq DNA Polymerase wiodNTP

FYT011-500U 500U Ask for price

Taq DNA Polymerase (TaqDNA) Protein

abx073521-100tests 100 tests
EUR 225

Apex Red Taq DNA Polymerase, 10000u

42-402R 20 x 500u/Unit
EUR 1229.49
Description: 10X NH4 Buffer, Mg Free

Apex Red Taq DNA Polymerase, 500u

42-409R 1 x 500u/Unit
EUR 62.1
Description: 10X NH4 Buffer, Mg Free

Taq HS Red DNA Polymerase

abx461041-1096tests 10 × 96 tests Ask for price

Taq HS Red DNA Polymerase

abx461041-596tests 5 × 96 tests
EUR 2187.5

Taq HS Red DNA Polymerase

abx461041-96tests 96 tests
EUR 1062.5

Recombinant Taq Dna Polymerase - EACH

27079804 EACH
EUR 132.3

Recombinant (E.Coli) Taq DNA Polymerase

RP-394 1000 IU
EUR 196.8

Taq Plus DNA Polymerase (PCR)

G012 250 U (50 ul)
EUR 87.6

Taq Plus DNA Polymerase (PCR)

G040 1000 U (200 ul)
EUR 127.2

Taq DNA Polymerase Polyclonal Antibody

7018-100 each
EUR 424.8

Taq DNA Polymerase Polyclonal Antibody

7018-30T each
EUR 175.2

YEA taq DNA Polymerase wi dNTP

FYT001-500U 500U Ask for price

AffiTaq® DNA Polymerase - With Buffer - With MgCl2 - Without dNTP

AFG-BOR-101 10X (1000U/200µL)
EUR 380

Taq DNA Polymerase with Red Dye

abx461047-1096tests 10 × 96 tests
EUR 1787.5

Taq DNA Polymerase with Red Dye

abx461047-596tests 5 × 96 tests
EUR 1062.5

Taq DNA Polymerase with Red Dye

abx461047-96tests 96 tests
EUR 362.5

ACTaq? Taq Blue DNA Polymerase, 1000U

E2100B-1000U each
EUR 272.4

Taq DNA polymerase (TQ21) , DNA Aptamer, unlabeled

AD-146-U Custom Ask for price

ACTaq? Taq Blue DNA Polymerase, 250U

E2100B-250U each
EUR 126

Taq HS DNA Polymerase (Glycerol-free)

QL101-01 1,000 U
EUR 89

Taq HS DNA Polymerase (Glycerol-free)

QL101-02 5,000 U
EUR 406

Taq HS DNA Polymerase (Glycerol-free)

QL101-03 50,000 U
EUR 3625

Recombinant Taq Plus DNA Polymerase

7-03631 250U Ask for price

Recombinant Taq Plus DNA Polymerase

7-03632 750U Ask for price

Recombinant Taq Plus DNA Polymerase

7-03633 2,500U Ask for price

Taq Plus DNA Polymerase (Recombinant)

abx073522-2500U 2.500 U
EUR 710.4

Taq Plus DNA Polymerase (Recombinant)

abx073522-250U 250 U
EUR 276

Taq Plus DNA Polymerase (Recombinant)

abx073522-750U 750 U
EUR 393.6

Taq Plus DNA Polymerase Recombinant

rAP-1063 Inquiry Ask for price

Taq DNA Polymerase, 5units/㎕ , Bulk Packing

T2200-B01 10,000 units
EUR 1388.4

Taq DNA Polymerase, 5units/㎕ , Bulk Packing

T2200-B05 5x10,000 units
EUR 6540

Taq DNA polymerase (TQ21) , DNA Aptamer, Biotinylated

AD-146-B Custom Ask for price

Taq DNA Polymerase M101 (5,000 U/mL)

RK26000 250U
EUR 60

amfiSure Hot-Start Taq DNA Polymerase

P0322-010 100 units
EUR 176.4

amfiSure Hot-Start Taq DNA Polymerase

P0322-025 250 units
EUR 273.6

T4 DNA Polymerase, 5u/ul

BEP0061 100U
EUR 153.97

DNA Amplification Kit with Taq DNA Polymerase, 100app

PL1202-K each Ask for price

Tsg DNA Polymerase, 5u/ul

D0081 5X200U
EUR 112.2

Pfu DNA Polymerase, 5u/ul

B0093(D0090P) 500U
EUR 164.4

Taq DNA Polymerase with Red Dye Mix

abx461048-1096tests 10 × 96 tests Ask for price

Taq DNA Polymerase with Red Dye Mix

abx461048-596tests 5 × 96 tests
EUR 1062.5

Taq DNA Polymerase with Red Dye Mix

abx461048-96tests 96 tests
EUR 325

Taq DNA Polymerase with dNTP Mix (6000U)

9K-001-0018 6000U
EUR 1536.74

Taq DNA Polymerase with dNTP Mix (500U)

9K-001-0031 500U
EUR 351.28

Taq DNA Polymerase with dNTP Mix (3000U)

9K-001-0032 3000U
EUR 1088.87

Taq DNA Polymerase with dNTP Mix (1000U)

9K-001-0034 1000U
EUR 518.84

Maximo DFS-Plus Taq DNA Polymerase DNA-free

N140 500 units
EUR 60

Maximo DFS-Plus Taq DNA Polymerase DNA-free

N142 5x500 units
EUR 144

Maximo DFS-Plus Taq DNA Polymerase DNA-free

N144 20x500 units
EUR 440.4


In order to develop a test to identify the genes responsible for antibiotic resistance in gram-negative bacteria, it has been found that the standard of Taq DNA polymerase (not DNA-free) blaTEM contaminated with fragments of genes that varied in length and number. BlaTEM complete gene sequences are absent or detected in very small amounts. We developed an approach to avoid false-positive findings caused by contamination polymerase gene sequence in a conventional blaTEM