Standardisation of Cystic Fibrosis Microbiology Testing In

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Standardisation of

Cystic Fibrosis Microbiology Testing

In Scotland

Second Edition, March 2015

Scottish Microbiology and Virology Network (SMVN)

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Author

Dr Fiona M. MacKenzie (SMVN Manager)

SMVN contributors: Ms K. Milne (NHS Grampian) Ms C. Lucas (NHS Greater Glasgow & Clyde) Dr W. Olver (NHS Tayside) Dr I. Laurenson (NHS Lothian) Dr I. Gould (NHS Grampian) Prof C. Williamson (NHS Greater Glasgow & Clyde)

In collaboration with the following Paediatric Cystic Fibrosis Network (PCFN) and Adult Cystic

Fibrosis Network colleagues (ACFN): Dr R. Brooker (NHS Grampian, PCFN Clinical Lead) Dr D. Urquhart (NHS Lothian) Dr H. Rodgers (NHS Lothian) Dr C. MacGregor (NHS Greater Glasgow & Clyde)

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INDEX

1. Background 4

1.1 Standardisation of Cystic Fibrosis Microbiology

Testing in Scotland: VERSION 1

4

1.2 Standardisation of Cystic Fibrosis Microbiology

Testing in Scotland: VERSION 2

4

2. General considerations and sample preparation 5

3. Direct molecular detection 5

4. Sample culture 5

Table 4.1 Recommended culture media and conditions for

respiratory samples from individuals with CF

6

5 Organism identification 7

5.1 Levels of identification

7

5.2 Confirmation of identification

7

5.3 Algorithm for identification of non-fermenting Gram negative bacilli (CF Trust Laboratory standards for processing microbiological samples from people with Cystic Fibrosis)

8

5.4 Guideline to identify pseudomonads which cause

identification problems (SMI ID 17)

9

6. Antibiotic susceptibility testing 10

Scottish standard CF AST panels 11

7. Frequency and mode of testing 12

8. Reporting 12

9. Isolates to be sent to Reference Laboratories 13

10. Cystic Fibrosis antibiotic susceptibility testing service (CFASS) 13

11. Public Health reporting 13

12. References 14

Appendix 1: Tables a to f: AST methods and interpretive criteria 15

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1. Background

Within Scotland there are five Specialist Cystic fibrosis (CF) Centres based in Glasgow, Edinburgh, Aberdeen, Dundee and Inverness. Scottish CF microbiology is therefore largely carried out in the five laboratories associated with these centres, although testing is also carried out in laboratories associated with smaller CF units.

Infection of the airways remains the primary cause of morbidity and mortality in persons with CF, resulting in this patient group having a life-long association with the microbiology laboratory. To deliver optimum care to those with CF, the long term picture of an individual’s lung microbiology is important and it is recognised that this may be delivered by different centres, units and microbiology laboratories as the individual grows up.

CF microbiology is recognised as complex and challenging and the basic service delivered has historically been highly variable within Scotland. In accordance with the aims of all national clinical and managed diagnostic networks, it is the aim of the SMVN to deliver a service that is consistent and equitable across Scotland and which is focused on the patient. The Paediatric CF network has specifically requested that the SMVN agrees to deliver a consistent basic Microbiology service across Scotland to support standardised delivery of care.

1.1 Standardisation of Cystic Fibrosis Microbiology Testing in Scotland: 1st edition.

As a minimum, CF Microbiology in Scotland should be carried out in accordance with the most up-to-date and relevant guidelines available, including the UK Standards for Microbiology Investigations (SMIs), Cystic Fibrosis Trust guidelines and Scottish national methods for antimicrobial susceptibility testing (AST).

Version 1 of this document was approved in March 2014 and summarised the most salient points from the reference documents which are relevant only to the microbiology laboratory and have been the cause of non-standardisation across Scotland. Further detail may be obtained by referring to the reference documents directly.

1.2 Standardisation of Cystic Fibrosis Microbiology Testing in Scotland: 2nd

edition.

It is recognised that the current reference documents are not all up-to-date and gaps remain in the guidance. It was hoped that Version 2 of the Scottish summary guidelines would be developed to include any new SMI or CF Trust guidelines but none have been published. In the absence of new guidelines, a CF Microbiology sub-group of the SMVN was reconvened and met with both the Paediatric and Adult CF Networks to address outstanding issues which are more clinically relevant such as possible standard national antibiotic panels for AST, frequency of full AST work up and reporting and frequency of referral of isolates to Reference Laboratories for typing.

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2. General considerations and sample preparation

2.1 Safety considerations and specimen storage should be in line with accredited standards for processing respiratory specimens in a routine Clinical Microbiology laboratory.

1

2.2 Sample preparation1,2

2.2.1 The following respiratory samples should be accepted for microbiological testing: cough swab, cough plate, oropharyngeal culture, laryngeal or naso-pharyngeal aspirate, expectorated sputum, induced sputum following hypertonic saline, bronchoalveolar lavage and bronchoscopy brush specimens. It should be borne in mind that pathogen yields may vary depending on the sample.

2.2.2 Specimens should not be rejected based on macroscopic appearance.

2.2.3 Gram staining is not recommended. If mycobacterial testing of a sputum sample is requested, a relevant fluorochrome staining method should be used in line with the TB Action Plan for Scotland.

2.2.4 Use of a mucolytic agent is recommended.

3. Direct molecular detection1

Direct PCR methods are acknowledged to be quicker and more sensitive than conventional culture methods and should be used if available in a specific laboratory. It is acknowledged however, that there is little / no availability of direct molecular testing in Scotland. This will be reviewed in an ongoing basis and the guidelines updated as and when appropriate.

4. Sample culture Recommended culture media and conditions for respiratory samples from individuals with CF may be found in Table 4.1

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Table 4.1 Recommended culture media and conditions for respiratory samples from individuals with CF1,2

Target organism Medium

Incubation conditions Examination

of plates Temperature (°C) Atmosphere Time (hr)

S. aureus Selective agar (Mannitol salt agar / CHROMagar)

35 - 37 Air 40 - 48 Daily

S. pneumoniae, M. catarrhalis

Chocolate agar or blood agar (with optochin disc for S. pneumoniae)

35 – 37 Chocolate: Air

Blood: 5-10% CO2 40 - 48 Daily

H. influenzae

Selective agar. Eg. Chocolate agar with bacitracin / cefsulodin

35 - 37 Anaerobic

(to inhibit P. spp.) 40 - 48 Daily

P. aeruginosa CLED, MacConkey or selective agar

35 - 37 Air

40 - 48 Growth should be visible

within 24hr but confirmation of mucoid

P. aeruginosa may require 48hr

Daily

B. cepacia spp. B. cepacia selective agar

35 - 37 Air 5 days Daily

S. maltophilia,

Differentiate LF from

NLF

CLED, MacConkey or selective agar

35 - 37 Air 40 - 48 Daily

Fungi Sabouraud medium 35 – 37 (22) Air 7days Daily

Mycobacteria Culture should be performed using both an automated liquid culture system and a solid medium

in line with TB Action Plan

for Scotland

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5. Organism identification

5.1 Levels of identification

According SMI B57,1 the minimum levels of identification in the laboratory are

detailed as follows however, organisms may be further identified if clinically or

epidemiologically indicated.

B. cepacia complex Species level (see ID 17 – Identification of glucose non-fermenting Gram negative rods)

S. maltophilia Species level

Enterobacteriaceae Species level

Klebsiella pneumoniae

Species level

Fungi Genus level

H. influenzae Species level

M. catarrhalis Species level

N. meningitidis Species level

Pasteurella Species level

Pseudomonads "Pseudomonads" level

P. aeruginosa Mucoid or non-mucoid species level

S. aureus Species level

S. pneumoniae Species level

Yeasts "Yeasts" level

Legionella species level

Mycobacterium See SMI B 40 - Investigation of specimens for Mycobacterium species and TB Action Plan for Scotland

Parasites See SMI B 31 - Investigation of specimens other than blood for parasites

5.2 Confirmation of identification

All identification tests should be performed from non-selective agar.3

The following can be identified relatively easily

Organism Automated MALDI Biochemical tests /

agglutination etc

S. aureus VITEK Yes Yes

S. pneumoniae VITEK No Yes

M. catarrhalis VITEK Yes Yes

H. influenzae VITEK Yes Yes

P. aeruginosa / species No Yes3 Yes

B. cepacia spp (complex) No No4 (Yes) Yes

S. maltophilia VITEK Yes3 Yes

Non-Enterobacteriaceae No (Yes3) Yes

Fungi No Yeasts yes, moulds no Yes

Mycobacteria Yes (Ref lab) No Yes (Ref lab)

http://www.hpa.org.uk/SMI/pdf/Identification
















http://www.hpa.org.uk/SMI/pdf/bacteriology

http://www.hpa.org.uk/SMI/pdf/bacteriology

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5.3 According to the CF Trust Laboratory standards for processing

microbiological samples from people with Cystic Fibrosis,2 the following

algorithm should be used for identification of non-fermenting Gram negative

bacilli.

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5.4 According to SMI ID 17 (Identification of Pseudomonas species and

morphologically similar organisms)3 the following algorithm may be used for guidance

to identify pseudomonads which can cause particular identification problems.

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6. Antibiotic susceptibility testing (AST)

General AST The SMVN has a long established sub group which has addressed standardisation of AST methods across Scotland. This includes standardisation of AST on CF pathogens. General recommendations are summarised as follows:

6.1 Where possible, AST should be carried out on the Vitek 2 system.

6.1.1 Vitek 2 AST results should be interpreted using EUCAST breakpoints (BPs).

6.1.2 In the absence of EUCAST BPs, CLSI BPs should be used.

6.2 If the Vitek 2 is not capable of performing AST for specific organisms alternative methods should be used.

6.2.1 EUCAST methodology and interpretive criteria should be used as first choice.

6.2.2 In the absence of EUCAST methodology and interpretive criteria, CLSI methodology and interpretive criteria should be used.

6.2.3 Where MICs must be measured, the use of commercial gradient strips (such as Etest strips) is acceptable.

CF pathogens (general)

6.3 As for identification tests

3, AST should be performed from non-selective agar.

6.4 AST of S. aureus and S. pneumoniae should be carried out on the Vitek 2. It is noted that some S. pneumoniae isolated from CF samples do not perform well in the Vitek 2 and these should be tested using an alternative method.

6.5 Currently, automated AST (eg on the Vitek 2) is not recommended for glucose non-fermenting Gram negative bacilli isolated from the respiratory tract of individuals with CF. The tables in Appendix 1 provide details of all the methodology and interpretive breakpoint (BP) criteria applicable for each pathogen group (there is no suggestion that all combinations are tested). All EUCAST information is accurate according to the latest 2015 guidelines. CLSI information reflects the 2014 interpretive criteria guidelines (which will next be updated in 2016).

6.5.1 DISC DIFFUSION: Report S/R only antibiotics for which approved methods / interpretive criteria exist.

6.5.2 MIC: Report MIC and / or S/R for antibiotics for which approved methods / interpretive criteria exist:

For antibiotics for which NO approved methods / interpretive criteria exist, carry out Etest and report MIC without interpretation.

6.6 For glucose non-fermenting Gram negative bacilli the antibiotics in Table 1 should be tested. A first line battery should be tested and if fully sensitive then testing of the second line battery of antibiotic is not required.

6.7 Mycobacterial AST should be carried out at the Reference Laboratory.

6.8 For fungi, the CF Trust has recommendations for cases of repeated isolation of Aspergillus spp. In spite of long-term treatment with antifungals, there may be a need for referral to a reference laboratory.

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Table 1

Scottish standard CF panels

Include in standard disc panel

B. cepacia S. maltophilia P. aeruginosa / spp Other non-fermenting

Gram negative bacilli**

Disc diff MIC Disc diff MIC Disc diff MIC Disc diff MIC

Piperacillin-tazobactam N/A * N/A * S/R (EUCAST) S/R (EUCAST) N/A S/R (CLSI)

Ticarcillin N/A * N/A * S/R (EUCAST) S/R (EUCAST) N/A S/R (CLSI)

Ticarcillin-clavulanate N/A S/R (CLSI) N/A S/R (CLSI) S/R (EUCAST) S/R (EUCAST) N/A S/R (CLSI)

Temocillin N/A * N/A * N/A *

Cefepime N/A * N/A * S/R (EUCAST) S/R (EUCAST) N/A S/R (CLSI)

Ceftazidime S/R (CLSI) S/R (CLSI) N/A S/R (CLSI) S/R (EUCAST) S/R (EUCAST) N/A S/R (CLSI)

Imipenem N/A * N/A * S/R (EUCAST) S/R (EUCAST) N/A S/R (CLSI)

Meropenem / Doripemen S/R (CLSI) S/R (CLSI) N/A * S/R (EUCAST) S/R (EUCAST) N/A S/R (CLSI)

Aztreonam N/A * N/A * S/R (EUCAST) S/R (EUCAST) N/A S/R (CLSI)

Ciprofloxacin N/A * N/A * S/R (EUCAST) S/R (EUCAST) N/A S/R (CLSI)

Levofloxacin N/A S/R (CLSI) S/R (CLSI) S/R (CLSI) S/R (EUCAST) S/R (EUCAST) N/A S/R (CLSI)

Amikacin N/A * N/A * S/R (EUCAST) S/R (EUCAST) N/A S/R (CLSI)

Gentamicin N/A * N/A * S/R (EUCAST) S/R (EUCAST) N/A S/R (CLSI)

Tobramycin N/A * N/A * S/R (EUCAST) S/R (EUCAST) N/A S/R (CLSI)

Colistin N/A * N/A * N/A S/R (EUCAST) N/A S/R (CLSI)

Trimethoprim-sulphamethoxazole S/R (CLSI) S/R (CLSI) S/R (EUCAST) S/R (EUCAST) N/A * N/A S/R (CLSI)

Chloramphenicol N/A S/R (CLSI) N/A S/R (CLSI) N/A * N/A S/R (CLSI)

Minocycline S/R (CLSI) S/R (CLSI) S/R (CLSI) S/R (CLSI) N/A * N/A S/R (CLSI)

Doxycycline N/A * N/A * N/A * N/A S/R (CLSI)

Fosfomycin N/A * N/A * N/A * N/A *

S/R (CLSI / EUCAST) Standard methodology and interpretive criteria according to either CLSI or EUCAST to be used.

N/A Not appropriate to test this drug – bug combination by disc diffusion as standards methods and interpretive criteria do not exist.

* MIC may be determined by Etest but there are no interpretive criteria. ** Antibiotics tested to be agreed locally with clinicians.

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7. Frequency and mode of testing

7.1 Routine antibiotic susceptibility testing (S/R) should be carried out on all relevant isolates from all CF samples. Specific first and second line antibiotic batteries for testing from Table 1 should be agreed upon locally.

7.2 Local Microbiology Departments should be willing and able to establish MICs but MICs should not be carried out routinely on all pathogens from all samples.

7.3 If a patient is not responding to treatment after seven days, the clinician should request MICs on the pathogen(s) isolated from the patient’s sample(s) at the start of the current episode requiring treatment. A new sample must not be sent. The local laboratory must therefore store bacterial isolates for at least 7 days and should be prepared to carry out MICs. Once MICs are available, it would be appropriate for a conversation between the clinician and the Microbiologist to take place.

7.4 MICs should be carried out locally (i) every six months for each patient, (ii) on request and (iii) in the event that a pathogen is reported resistant (R) to more than two antibiotic classes, at the request of the local physicians.

7.5 Mycobacterial species: if clinically indicated, samples should be checked annually for non-tuberculous mycobacteria (NTM).

7.6 NTM MICs should be carried out by the microtitre method at the Reference Laboratory.

8. Reporting

Organism Note on reporting

P. aeruginosa2 Presence should always be reported irrespective of quantity

B. cepacia complex2 Presence should always be reported. No need to report quantity.

• First isolates – issue an interim report until identification has been confirmed

• Phenotypic identification of B. cepacia in individuals who are known to be colonised with B. cepacia and have the same antibiogram as previous isolates

• Presumptive isolates from individuals who have been B. cepacia free for 12 months - use a validated recA PCR method to confirm identification. Send to HPS Colindale for genotyping.

S. aureus2 Presence should always be reported irrespective of quantity

MRSAs sent to Ref Lab for typing

H. influenzae2 As isolation of H. influenzae could indicate contamination from the upper

respiratory tract, it may be helpful to report the approximate amount present

S. maltophilia Presence should always be reported irrespective of quantity

S. pneumoniae Presence should always be reported irrespective of quantity

M. catarrhalis Should be reported only when heavy growth is present

Coliforms (LF / NLF) Report “of doubtful significance”

Pseudomonas spp. Presence should always be reported irrespective of quantity. No need to report mucoid / non-mucoid as the information does not change patient management.

“Pseudomonads” Issue an interim report until identification has been confirmed

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9. Isolates to be sent to Reference Laboratories for molecular typing

9.1 Mycobacteria should be sent to the Scottish Mycobacteria Reference Laboratory

9.2 B. cepacia spp. should be sent to the AMRHAI Reference Laboratory, PHE, Colindale for routine genotyping

9.3 P. aeruginosa should be sent for strain typing to the AMRHAI Reference Laboratory, PHE, Colindale.

9.4 MRSA should be sent to the Scottish MRSA Reference Laboratory

9.5 All first isolates, causes of reinfection and subsequent isolates with a change in antibiogram or which are deemed to be multi-resistant should be sent to the appropriate Reference Laboratory for molecular typing. Clinicians should be alerted of any common genotypes between patients as this may indicate infection prevention and control issues which will require active management.

9.6 Typing should be carried out on annual review samples, at the request of the local physicians.

9.7 9.5 and 9.6 will be implemented for two years after which the way forward will be reviewed, included any requirements for funding.

10. Cystic fibrosis antibiotic susceptibility testing service (CFASS)

CFASS is a specialist laboratory funded by NSD for adults with CF and is currently hosted by NHS Grampian, located in Medical Microbiology at Aberdeen Royal Infirmary. Paediatric isolates may be sent to the service but a charge will be incurred.

Isolates of NLF Gram negative organisms may be sent if:

10.1 There are problems locally with identifying suitable treatment regimens due to e.g. the isolate being multidrug-resistant, the individual has allergies to or is intolerant of antimicrobials

10.2 When it is deemed clinically necessary e.g. the individual is not responding to the antimicrobial therapy or their clinical picture significantly worse than would be expected with available bacteriology.

11. Public Health Reporting

All isolates of Mycobacterium tuberculosis complex must be reported.

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12. References

1. SMI B57, Investigation of Bronchoalveolar Lavage, Sputum and Associated

Specimens is dated August 2012 and is currently still under consultation.

2. Laboratory standards for processing microbiological samples from people

with Cystic Fibrosis, 1st Edition. Published by the Cystic Fibrosis Trust in

September 2010.

3. SMI ID 17 (Identification of Pseudomonas species and morphologically

similar organisms). Dated January 2014. Currently under consultation

4. Burns, JL, Rolain JM. (2014). Culture based diagnostic microbiology in cystic

fibrosis: can we simplify the complexity? Journal of Cystic Fibrosis 13; 1-9.

5. Pseudomonas aeruginosa infection in people with cystic fibrosis:

suggestions for prevention and infection control: 2nd

Edition. Published by the Cystic Fibrosis Trust in November 2004.

6. The Burkholderia cepacia complex: suggestions for prevention and

infection control: 2nd Edition. Published by the Cystic Fibrosis Trust in September 2004.

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APPENDIX 1 The following tables detail all possible “drug – bug” combinations where

either EUCAST or CLSI methodology and breakpoints exist.

Table a Pseudomonas aeruginosa / Pseudomonas species

Zone

diameter

BPs (mm)

Testing

guideline

Testing

method

Disc

content

MIC BPs

(mg/L)

Antimicrobial (µg) S > R < S < R >

Piperacillin-tazobactam EUCAST Disc 30-6 19 19 16-4 16-4

Ticarcillin EUCAST Disc 75 17 17 16 16

Ticarcillin-clavulanate EUCAST Disc 75-10 17 17 16-4 16-4

Cefepime EUCAST Disc 30 19 19 8 8

Ceftazidime EUCAST Disc 10 16 16 8 8

Doripenem EUCAST Disc 10 25 22 1 2

Imipenem EUCAST Disc 10 20 17 4 8

Meropenem EUCAST Disc 10 24 18 2 8

Aztreonam EUCAST Disc 30 50 16 1 16

Ciprofloxacin EUCAST Disc 5 25 22 0.5 1

Levofloxacin EUCAST Disc 5 20 17 1 2

Amikacin EUCAST Disc 30 18 15 8 16

Gentamicin EUCAST Disc 10 15 15 4 4

Tobramycin EUCAST Disc 10 16 16 4 4

Colistin EUCAST MIC N/A - - 4 4

Table b Burkholderia cepacia

Zone

diameter

BPs (mm)

Testing

guideline

Testing

method

Disc

content

MIC BPs

(mg/L)


Ticarcillin-clavulanate CLSI MIC N/A - - 16-2 128-2

Ceftazidime CLSI Disc 30 21 17 8 32

Meropenem CLSI Disc 10 20 15 4 16

Levofloxacin CLSI MIC N/A - - 2 8

Trimethoprim-

sulphamethoxazole CLSI Disc 1.25-23.75 16 10 2-38 4-76

Chloramphenicol CLSI MIC N/A - - 8 32

Minocycline CLSI Disc 30 19 14 4 16

Table c Stenotrophomonas maltophilia

Zone

diameter

BPs (mm)

Testing

guideline

Testing

method

Disc

content

MIC BPs

(mg/L)


Ticarcillin-clavulanate CLSI MIC N/A - - 16-2 128-2

Ceftazidime CLSI MIC N/A - - 8 32

Levofloxacin CLSI Disc 5 17 13 2 8

Trimethoprim-

sulphamethoxazole EUCAST Disc 1.25-23.75 16 16 4 4

Chloramphenicol CLSI MIC N/A - - 8 32

Minocycline CLSI Disc 30 19 14 4 16

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Table d Non-enterobacteriaceae

Includes other glucose-nonfermenting Gram negative bacilli.

Excludes P. aeruginosa, Acinetobacter spp., B. cepacia, B. mallei, B. pseudomallei and S. maltophilia.

Testing

guideline

MIC BPs

Testing

method

(mg/L)

Antimicrobial S < R ≥

Piperacillin-tazobactam CLSI MIC 16-4 128-4

Ticarcillin CLSI MIC 16 128

Ticarcillin-clavulanate CLSI MIC 16-2 128-2

Cefepime CLSI MIC 8 32

Ceftazidime CLSI MIC 8 32

Imipenem CLSI MIC 4 16

Meropenem CLSI MIC 4 16

Aztreonam CLSI MIC 8 32

Ciprofloxacin CLSI MIC 1 4

Levofloxacin CLSI MIC 2 8

Amikacin CLSI MIC 16 64

Gentamicin CLSI MIC 4 16

Netilmicin CLSI MIC 8 32

Tobramycin CLSI MIC 4 16

Colistin CLSI MIC 2 8

Trimethoprim-

sulphamethoxazole CLSI MIC 2-38 4-76

Chloramphenicol CLSI MIC 8 32

Minocycline CLSI MIC 4 16

Doxycycline CLSI MIC 4 16

Tetracycline CLSI MIC 4 16

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Table e Haemophilus influenzae Zone

diameter

BPs (mm)

Testing

guideline

Testing

method

Disc

content

MIC BPs

(mg/L)


Ampicillin EUCAST Disc 2 16 16 11 1

1

Amoxicillin EUCAST - Note A 21 2

1

Amoxicillin-

clavulanate EUCAST Disc 2-1 15 15 22 2

2

Cefepime EUCAST Disc 30 27 27 0.25 0.25

Cefixime EUCAST Disc 5 25 25 0.12 0.12

Cefotaxime EUCAST Disc 5 26 26 0.12 0.12

Cefpodoxime EUCAST Disc 10 26 23 0.25 0.5

Ceftaroline EUCAST MIC - - - 0.03 0.03

Ceftriaxone EUCAST Disc 30 30 30 0.12 0.12

Cefuroxime iv EUCAST Disc 30 26 25 1 2

Cefuroxime oral EUCAST Disc 30 50 26 0.12 1

Ertapenem EUCAST Disc 10 20 20 0.5 0.5



Ciprofloxacin EUCAST Disc 5 26 26 0.5 0.5


Moxifloxacin EUCAST Disc 5 25 25 0.5 0.5

Azithromycin EUCAST - Note B 0.123 4

3

Clarithromycin EUCAST - Note B 13 32

3

Erythromycin EUCAST Disc 15 50 10 0.5 16

Doxycycline EUCAST MIC - Note C 14 2

4

Minocycline EUCAST Disc 30 24C 21

C 1

4 2

4

Tetracycline EUCAST Disc 30 25 22 1 2

Chloramphenicol EUCAST Disc 30 28 28 2 2

Rifampicin EUCAST Disc 5 18 18 1 1

Trimethoprim-

sulphamethoxazole EUCAST Disc 1.25-23.75 23 20 0.5 1

Disc diffusion A – Susceptibility inferred from ampicillin. B - Erythromycin can be used to determine susceptibility to azithromycin and clarithromycin. C – Isolates susceptible to tetracycline are also susceptible to doxycycline and minocycline but some isolates resistant to tetracycline may be susceptible to doxycycline and/or minocycline. An MIC method should be used to test doxycycline if required if isolate is tetracycline resistant.

MIC breakpoints 1 – Breakpoints based on iv administration. Breakpoints apply to β-lactamase negative isolates only. β-lactamase positive isolates are reported resistant to penicillins without β-lactamase inhibitors. 2 – Concentration of clavulanate fixed at 2mg/L. 3 – Erythromycin can be used to determine susceptibility to azithromycin and clarithromycin. 4 - Isolates susceptible to tetracycline are also susceptible to doxycycline and minocycline but some isolates resistant to tetracycline may be susceptible to doxycycline and/or minocycline. An MIC method should be used to test doxycycline if required if isolate is tetracycline resistant.

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Table f Moraxella catarrhalis Zone

diameter

BPs (mm)

Testing

guideline

Testing

method

Disc

content

MIC BPs

(mg/L)


Ampicillin EUCAST - - - Note 1

Amoxicillin-

clavulanate EUCAST Disc 2-1 19 19 12 1

2

Cefixime EUCAST Disc 5 21 18 0.5 1

Cefotaxime EUCAST Disc 5 20 17 1 2

Ceftriaxone EUCAST Disc 30 24 21 1 2

Cefuroxime iv EUCAST Disc 30 21 18 4 8

Cefuroxime oral EUCAST Disc 30 50 21 0.12 4

Ertapenem EUCAST Disc 10 29 29 0.5 0.5



Ciprofloxacin EUCAST Disc 5 23 23 0.5 0.5


Moxifloxacin EUCAST Disc 5 23 23 0.5 0.5

Azithromycin EUCAST - Note A 0.253 0.5

3

Clarithromycin EUCAST - Note A 0.253 0.5

3

Erythromycin EUCAST Disc 15 23 20 0.25 0.5

Doxycycline EUCAST MIC - Note B 14 2

4

Minocycline EUCAST Disc 30 25B 22

B 1

4 2

4

Tetracycline EUCAST Disc 30 28 25 1 2

Trimethoprim-

sulphamethoxazole EUCAST Disc 1.25-23.75 18 15 0.5 1

Disc diffusion A - Erythromycin can be used to determine susceptibility to azithromycin and clarithromycin. B – Isolates susceptible to tetracycline are also susceptible to doxycycline and minocycline but some isolates resistant to tetracycline may be susceptible to doxycycline and/or minocycline. An MIC method should be used to test doxycycline if required if isolate is tetracycline resistant.

MIC breakpoints 1 – Most M. catarrhalis produce β-lactamase although production is slow and may give weak results with in vitro tests. β-lactamase producers should be reported resistant to penicillins and aminopenicillins without inhibitors. 2 – Concentration of clavulanate is fixed at 2mg/L. 3 – Erythromycin can be used to determine susceptibility to azithromycin and clarithromycin. 4 - Isolates susceptible to tetracycline are also susceptible to doxycycline and minocycline but some isolates resistant to tetracycline may be susceptible to doxycycline and/or minocycline. An MIC method should be used to test doxycycline if required if isolate is tetracycline resistant.

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Standardisation of Cystic Fibrosis Microbiology Testing In