bsac rolling programme for devising acceptable limits for control strains jenny andrews the bsac...
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BSAC rolling programme for devising acceptable limits for
control strainsJenny AndrewsJenny Andrews
The BSAC Standardized Method The BSAC Standardized Method Development CentreDevelopment Centre
Acceptable limits for control strains
Used by diagnostic laboratories to monitor the Used by diagnostic laboratories to monitor the performance of testing.performance of testing.
There are gaps in the tables that need filling.There are gaps in the tables that need filling. At present At present S. aureusS. aureus is used to control testing of is used to control testing of
fastidious organisms and this may not be ideal fastidious organisms and this may not be ideal because the growth requirements of fastidious because the growth requirements of fastidious organisms are different to that of staphylococci.organisms are different to that of staphylococci.
Findings from a previous BSAC study
Confirmed that agar poured `in-house’ to a depth Confirmed that agar poured `in-house’ to a depth between 3.5-4.5 mm, and pre-poured plates from between 3.5-4.5 mm, and pre-poured plates from Oxoid and bioMerieux gave acceptable results by Oxoid and bioMerieux gave acceptable results by BSAC methodology.BSAC methodology.
When combined data from these plates was used When combined data from these plates was used to calculate the acceptable limits for all of the to calculate the acceptable limits for all of the antibiotic/strain combinations tested, the ranges antibiotic/strain combinations tested, the ranges were similar to those found in previous `field were similar to those found in previous `field studies’. So it was proposed that this procedure studies’. So it was proposed that this procedure could be used to fill the gaps in the tables.could be used to fill the gaps in the tables.
Programme design
After discussion the Working Party decided After discussion the Working Party decided that it would be prudent if acceptable limits that it would be prudent if acceptable limits were calculated using data from several were calculated using data from several laboratories rather than one centre.laboratories rather than one centre.
However, SMDC acceptable ranges could However, SMDC acceptable ranges could be used as a guide for comparison.be used as a guide for comparison.
Request for help
Needed the help of laboratories using the BSAC Needed the help of laboratories using the BSAC method, but unsure if laboratories would take part. method, but unsure if laboratories would take part.
Letter sent to known users of the BSAC methodLetter sent to known users of the BSAC method Asking if they would take part and select from a Asking if they would take part and select from a
list of antibiotic/strain combinations those they list of antibiotic/strain combinations those they were prepared to testwere prepared to test
20 laboratories agreed to take part20 laboratories agreed to take part
QC Study
SMDC calculated acceptable limits by SMDC calculated acceptable limits by testing discs 40 times each on ISA poured testing discs 40 times each on ISA poured to a depth of 3.5, 4 & 4.5mm and pre-to a depth of 3.5, 4 & 4.5mm and pre-poured plates from Oxoid & bioMerieux. poured plates from Oxoid & bioMerieux. 200 observations200 observations
The participating laboratories were asked to The participating laboratories were asked to test discs (supplied by SMDC) 5 times on test discs (supplied by SMDC) 5 times on 10 separate occasions. 250 observations.10 separate occasions. 250 observations.
How are the acceptable limits for the control strains calculated?
Obtain at least 200 zone diameters for the Obtain at least 200 zone diameters for the strain/antibiotic disc combination.strain/antibiotic disc combination.
Determine the number of observations at each Determine the number of observations at each zone diameter.zone diameter.
Calculate the cumulative % at each zone diameter.Calculate the cumulative % at each zone diameter. Construct a graph of cumulative % versus zone Construct a graph of cumulative % versus zone
diameter.diameter. Read off the zones equivalent to 2.5% & 97.5% of Read off the zones equivalent to 2.5% & 97.5% of
observations to give the acceptable range.observations to give the acceptable range.
Plot of cumulative % v zone diameter
05
101520253035404550556065707580859095
100
25 26 27 28 29 30 31 32 33 34
Zone diameter (mm)
Cum
ulat
ive
%
E. coli ATCC 25922
CT2 (Chester MS)CT2 (Chester MS) CT6 (Oxoid)CT6 (Oxoid) CT1 (Oxoid)CT1 (Oxoid) CT25 (Oxoid)CT25 (Oxoid) CT24 (In-house)CT24 (In-house)
Pip/tazoPip/tazo PiperacillinPiperacillin Nalidixic acidNalidixic acid LevofloxacinLevofloxacin AmpicillinAmpicillin
E. coli NCTC 10418
CT4 (Taunton PHL)CT4 (Taunton PHL) CT8 (In-house)CT8 (In-house) CT14 (bioMerieux)CT14 (bioMerieux) CT12 (Chester PHL)CT12 (Chester PHL) CT 20 (Oxoid)CT 20 (Oxoid)
Pip/tazoPip/tazo PiperacillinPiperacillin ChloramphenicolChloramphenicol ColistinColistin
E. faecalis ATCC 29212
CT17 (Oxoid)CT17 (Oxoid) CT15 (E&O)CT15 (E&O) CT16 (Taunton MS)CT16 (Taunton MS) CT29 (bioMerieux)CT29 (bioMerieux) CT10 (Leeds PHL)CT10 (Leeds PHL)
Pip/tazoPip/tazo MeropenemMeropenem ImipenemImipenem LinezolidLinezolid AzithromycinAzithromycin
E. coli ATCC 25922: Ampicillin 25 ug Participant zones compared with
SMDC acceptable limits
19
20
21
22
23
24
25
26
27
28
29
30
31
Zone
dia
met
er (m
m)
CT25 (Oxoid) CT1 (Oxoid) CT24 (In-house) CT6 (Oxoid) CT2 (Chester MS)
Observations
E. coli NCTC 10418 : Chloramphenicol 10 ug Participant zones compared with
SMDC acceptable limits
18192021222324252627282930313233343536
Zone
dia
met
er (m
m)
CT4 (Taunton PHL) CT8 (In-house) CT20 (Oxoid) CT14 (bioMerieux) CT12 (Chester PHL)
Observations
E. faecalis ATCC 29212: Azithromycin 15 ug Participant zones compared with
SMDC acceptable limits
10
11
12
1314
15
16
17
18
1920
21
22
23
Zone
dia
met
er (m
m)
CT17 (Oxoid) CT15 (E&O) CT16 (Taunton MS) CT29 (bioMerieux) CT10 (Leeds PHL)
Observations
E. faecalis ATCC 29212: Linezolid 10 ug Participant zones compared with
SMDC acceptable limits
19202122232425262728293031323334
Zone
dia
met
er (m
m)
CT17 (Oxoid) CT15 (E&O) CT16 (Taunton MS) CT29 (bioMerieux) CT10 (Leeds PHL)
Observations
E. faecalis ATCC 29212: Pip/tazo 85ug disc
Participant zones compared with SMDC acceptable limits
23
24
25
26
27
28
29
30
31
32
33
34
Zon
e d
iam
ete
r (m
m)
CT17 (Oxoid) CT15(E&O) CT16 (Taunton MS) CT29 (bioMerieux) CT10 (Leeds PHLS)
Observations
E. faecalis ATCC 29212: Pip/tazo 85ugAcceptable limits using data from 5 centres
(SMDC 27-32 mm)
23
24
25
26
27
28
29
30
31
32
33
34
Zone
dia
met
er (m
m)
CT17 (Oxoid) CT15(E&O) CT16 (Taunton ) CT29 (bioMerieux)
Observations
CT10 (Leeds PHL)
E. coli NCTC 10418: Centres where zone diameters outside the SMDC acceptable ranges
AntibioticAntibiotic CT4CT4
(Taunton (Taunton PHL)PHL)
CT8CT8
(Oxoid)(Oxoid)
CT20CT20
(bioMerieux(bioMerieux))
CT14CT14
(Oxoid)(Oxoid)
CT12CT12
(Chester (Chester PHL)PHL)
Pip/tazoPip/tazo
85ug85ug
XX
Too largeToo large
PiperacillinPiperacillin
75ug75ug
XX
Too largeToo large
ChloramphenicolChloramphenicol
10ug10ug
XX
Too largeToo large
ColistinColistin
25ug25ug
Summary of acceptable ranges (mm) for E. coli NCTC 10418
AntibioticAntibiotic SMDCSMDC
(mm)(mm)
5 centres5 centres
(mm)(mm)
4 centres*4 centres*
(mm)(mm)
SMDC &SMDC &
4 centres*4 centres*ChloramphenicolChloramphenicol
10ug10ug23-2723-27 20-2820-28 20-2620-26 21-2721-27
PiperacillinPiperacillin
75ug75ug31-3531-35 30-3630-36 29-3529-35 30-3530-35
Pip/tazoPip/tazo
85ug85ug31-3431-34 30-3630-36 29-3429-34 30-3530-35
ColistinColistin
25ug25ug15-1915-19 16-2016-20 16-1916-19 15-1915-19
* Excluding CT12
E. coli ATCC 25922: Centres where zone diameters outside the SMDC acceptable ranges
AntibioticAntibiotic CT25CT25
(Oxoid)(Oxoid)
CT11CT11
(Oxoid)(Oxoid)
CT24CT24
(Chester)(Chester)
CT6CT6
(Oxoid)(Oxoid)
CT2CT2
(Oxoid)(Oxoid)
Pip/tazoPip/tazo
85ug85ug
XX
Too largeToo large
XX
Too largeToo large
XX
Too largeToo large
XX
Too largeToo large
XX
Too largeToo large
PiperacillinPiperacillin
75ug75ug
XX
Too largeToo large
XX
Too largeToo large
XX
Too largeToo large
Nalidixic acidNalidixic acid
30ug30ug
XX
Too largeToo large
XX
Too largeToo large
XX
Too largeToo large
LevofloxacinLevofloxacin
1ug1ug
XX
Too largeToo large
XX
Too largeToo large
AmpicillinAmpicillin
25ug25ug
XX
Too largeToo large
NB. NCTC E. coli: CT12 (Chester MS) also large zones
Summary of acceptable ranges (mm) for E. coli ATCC 25922
AntibioticAntibiotic SMDCSMDC
(mm)(mm)
5 centres5 centres
(mm)(mm)
3 centres*3 centres*
(mm)(mm)
SMDC &SMDC &
3 centres*3 centres*
PiperacillinPiperacillin
75ug75ug
26-3126-31 29-3429-34 28-3228-32 27-3227-32
Pip/tazoPip/tazo
85ug85ug
26-3026-30 28-3228-32 28-3228-32 26-3126-31
Nalidixic acidNalidixic acid
30ug30ug
26-3026-30 26-3226-32 26-3126-31 26-3226-32
LevofloxacinLevofloxacin
1ug1ug
29-3329-33 28-3628-36 28-3428-34 28-3428-34
AmpicillinAmpicillin
25ug25ug
20-2620-26 22-2822-28 22-2822-28 21-2821-28
* Excluding CT24 & CT6
E. Faecalis ATCC 29212: Centres where zone diameters outside the SMDC acceptable ranges
AntibioticAntibiotic CT17CT17
(Oxoid)(Oxoid)
CT15CT15
(E&O)(E&O)
CT16CT16
(Taunton)(Taunton)
CT28CT28(bioMerieux)(bioMerieux)
CT10CT10
(Leeds)(Leeds)
Pip/tazoPip/tazo
85ug85ug
XX
Too largeToo large
XX
Too smallToo small
MeropenemMeropenem
10ug10ug
XX
Too largeToo large
XX
Too smallToo small
XX
Too smallToo small
ImipenemImipenem
10ug10ug
XX
Too smallToo small
LinezolidLinezolid
10ug10ug
XX
Too largeToo large
XX
Too smallToo small
AzithromycinAzithromycin
15ug15ug
XX
Too largeToo large
XX
Too smallToo small
XX
Too largeToo large
Summary of acceptable ranges (mm) for E. faecalis ATCC 29212
AntibioticAntibiotic SMDCSMDC
(mm)(mm)
5 centres5 centres
(mm)(mm)
3 centres*3 centres*
(mm)(mm)
SMDC &SMDC &
3 centres*3 centres*
Pip/tazoPip/tazo
85ug85ug
27-3227-32 24-3224-32 26-3126-31 26-3226-32
MeropenemMeropenem
10ug10ug
24-2824-28 19-2819-28 21-2721-27 22-2822-28
LinezolidLinezolid
10ug10ug
25-3025-30 22-3122-31 24-2824-28 24-2924-29
ImipenemImipenem
10ug10ug
28-3328-33 25-3225-32 28-3228-32 28-3228-32
AzithromycinAzithromycin
15ug15ug
15-2015-20 11-2111-21 14-2114-21 15-2115-21
*Excluding CT15 & CT17
Conclusions
Reasonable to exclude data from the Reasonable to exclude data from the analysis that is outside the acceptable limits analysis that is outside the acceptable limits generated by SMDC or that is different to generated by SMDC or that is different to the other laboratoriesthe other laboratories
Conclusions
Very worthwhile exercise and the rolling Very worthwhile exercise and the rolling programme is to be continued including programme is to be continued including looking at fastidious controls.looking at fastidious controls.
In future studies control strains will be In future studies control strains will be provided.provided.
Laboratories asked to test `once daily’ as Laboratories asked to test `once daily’ as this reflects `real life’. this reflects `real life’.
Future meeting
Intend to have a meeting with the Intend to have a meeting with the participating laboratoriesparticipating laboratories
Need to look at data from centres where Need to look at data from centres where zones are generally different from SMDC & zones are generally different from SMDC & other participants other participants
Acknowledgments QE Hospital, Woolwich, LondonQE Hospital, Woolwich, London Department of Clinical Medicine, ManchesterDepartment of Clinical Medicine, Manchester Truro PHLSTruro PHLS Rotherham DGHRotherham DGH Craigavon Area HospitalCraigavon Area Hospital Addenbrookes Hospital, CambridgeAddenbrookes Hospital, Cambridge Singleton PHL, SwanseaSingleton PHL, Swansea University Hospital, BirminghamUniversity Hospital, Birmingham Bedford HospitalBedford Hospital Bristol Royal InfirmaryBristol Royal Infirmary QE2, HertfordshireQE2, Hertfordshire UCL Hospitals, LondonUCL Hospitals, London Russells Hall Hospital, West MidlandsRussells Hall Hospital, West Midlands Manchester Royal InfirmaryManchester Royal Infirmary New Cross Hospital, WolverhamptonNew Cross Hospital, Wolverhampton
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