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Table 3 Comparison of standard deviations of measurements with calliper, the Sirscan system adaped on-screen by the human eye and the Sirscan fully automated mode

From: Standardisation of disk diffusion results for antibiotic susceptibility testing using the sirscan automated zone reader

S. aureusATCC 29213

                    
 

TOB

AK

CN

CIP

LEV

P

FOX

E

DA

SXT

RA

average

        

EUCAST QC range

20-26

18-24

19-25

21-27

23-29

12-18

24-30

23-29

23-29

29-32

30-36

          

Sirscan fully automated

                     

   Mean value

23.2

23.4

23.6

27.8

28.1

15.9

25.0

27.8

29.4

29.4

32.7

26.0

         

   Standard deviation

0.8

0.5

0.8

0.9

1.3

0.3

1.2

0.8

0.7

0.9

1.0

0.8*

         

Sirscan on-screen adjusted

                     

   Mean value

24.7

25.5

25.2

27.8

29.5

15.8

26.1

30.4

29.9

29.8

33.6

27.1

         

   Standard deviation

1.2

0.7

1.4

1.7

1

0.4

0.9

2.2

3

1.3

0.7

1.3

         

Calliper

                     

   Mean value

23.4

23.2

23.8

22.7

27.2

17.2

26.1

26.2

26.7

26.2

32.9

25.1

         

   Standard deviation

1

1.6

1.2

1.1

2

0.6

0.8

1.1

1.2

4.7

2.1

1.6*

         

E. coli ATCC 25922

                    
 

TOB

AK

CN

NA

NOR

CIP

LEV

AM

AMC

TPZ

CXM

CAZ

CTX

CPD

CRO

FEP

MEM

ETP

SXT

NF

average

EUCAST QC range

18-26

19-26

19-26

22-28

28-35

30-40

29-37

16-22

18-24

21-27

20-26

23-29

25-31

23-28

29-35

31-37

28-34

29-36

23-29

17-23

 

Sirscan fully automated

                     

   Mean value

22.4

20.6

20.4

25.9

28.1

28.4

28.4

20.6

21.8

23.3

24.8

26.0

27.5

24.7

29.3

31.0

29.2

34.0

26.3

17.5

25.5

   Standard deviation

1.1

0.8

0.5

0.8

0.6

1.0

0.7

0.9

0.6

0.4

0.4

0.0

0.5

0.5

0.7

0.7

0.9

0.8

0.4

0.5

0.7*

Sirscan on-screen adjusted

                     

   Mean value

23.2

24.5

25.1

25.9

34

37.3

35.4

25.9

23.3

27.6

26.1

27.8

31.1

29.3

32.3

35

35.9

34.3

28.4

24.8

29.4

   Standard deviation

1.5

1.3

1.4

1.3

2.4

1.6

1.5

1.8

1

1

1.2

1.2

1.9

1.2

1.3

1

1.2

1.2

1.4

1

1.4

Calliper

                     

   Mean value

22.4

24.4

23.3

27.6

31.1

34.1

31.5

22.3

25.1

25.7

24.8

25.5

28.5

27.6

30.2

33.7

23.9

34.3

27.3

17.4

27.0

   Standard deviation

1.1

2.5

1.2

1.3

1

1.6

1.5

1.2

0.7

1.1

1.2

1

1.5

2.4

1.4

1.4

1.3

2.4

0.9

1.6

1.4*

P. aeruginosa ATCC 27853

                    
 

TOB

AK

CN

LEV

FEP

CAZ

TPZ

IPM

MEM

average

          

EUCAST QC range

19-25

18-26

16-21

19-26

24-30

21-27

23-29

20-28

27-33

            

Sirscan fully automated

                     

   Mean value

24

24.9

21.5

28

27.8

22.9

25.3

23.6

29.9

25.3

           

   Standard deviation

0.8

0.7

1.4

0.6

0.4

0.3

0.7

0.5

0.3

0.6

           

Sirscan on-screen adjusted

                     

   Mean value

23.2

25.2

22

27.8

26.6

22.2

24.5

25

26.5

24.8

           

   Standard deviation

0.8

1

0.9

1.3

1.4

0.9

1.2

0.5

0.6

1.0

           

Calliper

                     

   Mean value

23.5

25.0

21.6

25.9

25.8

22.2

23.9

24.9

26.4

24.4

           

   Standard deviation

0.6

0.7

0.5

1.2

0.9

0.8

1.1

0.6

0.9

0.8

           
  1. Standard deviations of repeat measurements of S. aureus ATCC 29213 and E. coli ATCC 25922 were significantly lower with fully automated Sirscan readings as compared to manual calliper measurements indicating better reproducibility and precision of Sirscan readings. Asterisks indicate statistically significant differences (p<0.05) of mean standard deviations using the paired t-test. Measurements were done independently and double-blinded by 19 experienced persons (technicians and laboratory physicians) with the same disk diffusion plates of EUCAST quality control strains of S. aureus ATCC 29213, E. coli ATCC 25922, and P. aeruginosa ATCC 27853. Measurements of the Sirscan fully automated mode comprise 19 independent measurements of the panels. QC, quality control; AM, ampicillin; AMC, amoxicillin-clavulanic acid; AK, amikacin; CAZ, ceftazidime; CIP, ciprofloxacin; CN, gentamicin; CPD, cefpodoxime; CRO, ceftriaxone; CTX, cefotaxime; CXM, cefuroxime; DA, clindamycin; E, erythromycin; ETP, ertapenem; FEP, cepefim; FOX, cefoxitin; IPM, imipenem; LEV, levofloxacin; MEM, meropenem; NA, nalidixic acid; NF, nitrofuratoine; NOR, norfloxacin; P, penicillin G; RA, rifampicin; SXT, trimethoprim-sulfamethoxazole.
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BMC Microbiology

ISSN: 1471-2180

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