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Volume 26 Number 19

M45-A ISBN 1-56238-607-7 ISSN 0273-3099

Methods for Antimicrobial Dilution and Disk Susceptibility Testing of Infrequently Isolated or Fastidious Bacteria; Approved Guideline

James H. Jorgensen, PhD Janet Hindler, MCLS, MT(ASCP) Diane M. Citron, M(ASCP) Franklin R. Cockerill, III, MD Thomas R. Fritsche, PhD, MD Guido Funke, MD Jean B. Patel, PhD, D(ABMM) Paul C. Schreckenberger, PhD, D(ABMM) John D. Turnidge, MD Robert D. Walker, PhD David F. Welch, PhD, D(ABMM)

Abstract

If the susceptibility of a bacterial pathogen to antimicrobial agents cannot be predicted based on the identity of the organism alone, in vitro antimicrobial susceptibility testing of the organism isolated from the disease processes is indicated. Susceptibility testing is particularly necessary in those situations where the etiologic agent belongs to a bacterial species for which resistance to commonly used antimicrobial agents has been documented, or could arise. A variety of laboratory techniques can be used to measure the in vitro susceptibility of bacteria to antimicrobial agents. This document describes the standard microdilution and agar disk diffusion methods. It also includes a series of procedures designed to standardize test performance. The performance, applications, and limitations of the current CLSI-recommended methods are described. The tabular information in this document presents the most current information for drug selection, interpretation, and quality control for the infrequently isolated or fastidious bacterial pathogens included in this guideline. As more information becomes available, changes will be incorporated into future revisions of this document. Clinical and Laboratory Standards Institute (CLSI). Methods for Antimicrobial Dilution and Disk Susceptibility Testing of Infrequently Isolated or Fastidious Bacteria; Approved Guideline. CLSI document M45-A (ISBN 1-56238-607-7). Clinical and Laboratory Standards Institute, 940 West Valley Road, Suite 1400, Wayne, Pennsylvania 19087-1898 USA, 2006.

The Clinical and Laboratory Standards Institute consensus process, which is the mechanism for moving a document through two or more levels of review by the healthcare community, is an ongoing process. Users should expect revised editions of any given document. Because rapid changes in technology may affect the procedures, methods, and protocols in a standard or guideline, users should replace outdated editions with the current editions of CLSI/NCCLS documents. Current editions are listed in the CLSI catalog, which is distributed to member organizations, and to nonmembers on request. If your organization is not a member and would like to become one, and to request a copy of the catalog, contact us at: Telephone: 610.688.0100; Fax: 610.688.0700; E-Mail: [email protected]; Website: www.clsi.org

(Formerly NCCLS)

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Contents

Abstract ....................................................................................................................................................i Committee Membership........................................................................................................................ iii Foreword ................................................................................................................................................ix 1 2 3 4 5 6 Scope..........................................................................................................................................1 Introduction................................................................................................................................1 Standard Precautions..................................................................................................................4 Definitions .................................................................................................................................4 Indications for Performing Susceptibility Tests.........................................................................4 Methods for Dilution Antimicrobial Susceptibility Testing of Infrequently Isolated or Fastidious Bacteria ................................................................................................................5 6.1 6.2 6.3 7 8 9 Selection of Antimicrobial Agents................................................................................5 Antimicrobial Agents....................................................................................................5 Interpretive Categories..................................................................................................5

Methods for Antimicrobial Disk Diffusion Susceptibility Testing of Infrequently Isolated or Fastidious Bacteria.....................................................................................................................6 Therapy-Related Comments ......................................................................................................6 Quality Control ..........................................................................................................................6 9.1 Minimum Laboratory Requirements for Testing Infrequently Isolated or Fastidious Bacteria ......................................................................................................................................7

10

Detection of Resistance to Some -Lactams by a Direct -Lactamase Test .............................7

References...............................................................................................................................................8 Table 1. Abiotrophia species and Granulicatella species (Formerly Known as Nutritionally Deficient or Nutritionally Variant Streptococci)--Information and Interpretive Criteria for Broth Microdilution Susceptibility Testing............................................................................................................................10 Table 2. Aeromonas hydrophila Complex (Includes A. caviae, A. hydrophila, A. jandaei, A. schubertii, and A. veronii, Two Biotypes) and Plesiomonas shigelloides--Information and Interpretive Criteria for Broth Microdilution and Disk Diffusion Susceptibility Testing ....................12 Table 3. Bacillus species (Not B. anthracis)--Information and Interpretive Criteria for Broth Microdilution Susceptibility Testing ....................................................................................................14 Table 4. Campylobacter jejuni/coli--Information and Interpretive Criteria for Broth Microdilution and Disk Diffusion Susceptibility Testing ............................................................................................16 Table 5. Corynebacterium species (Including C. diphtheriae)--Information and Interpretive Criteria for Broth Microdilution Susceptibility Testing........................................................................18 v

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Contents (Continued)

Table 6. Erysipelothrix rhusiopathiae--Information and Interpretive Criteria for Broth Microdilution Susceptibility Testing............................................................................................................................20 Table 7. HACEK Group: the Aphrophilus Cluster of the Genus Haemophilus (i.e., H. aphrophilus, H. paraphrophilus, H. segnis), Actinobacillus actinomycetemcomitans, Cardiobacterium species, Eikenella corrodens, and Kingella species--Information and Interpretive Criteria for Broth Microdilution Susceptibility Testing ....................................................................................................22 Table 8. Lactobacillus species--Information and Interpretive Criteria for Broth Microdilution Susceptibility Testing............................................................................................................................24 Table 9. Leuconostoc species--Information and Interpretive Criteria for Broth Microdilution Susceptibility Testing............................................................................................................................26 Table 10. Listeria monocytogenes--Information and Interpretive Criteria for Broth Microdilution Susceptibility Testing............................................................................................................................27 Table 11. Moraxella catarrhalis--Information and Interpretive Criteria for Broth Microdilution Susceptibility Testing............................................................................................................................28 Table 12. Pasteurella species--Information and Interpretive Criteria for Broth Microdilution and Disk Diffusion Susceptibility Testing...................................................................................................30 Table 13. Pediococcus species--Information and Interpretive Criteria for Broth Microdilution Susceptibility Testing............................................................................................................................32 Table 14. Vibrio species (Not V. cholerae)--Information and Interpretive Criteria for Broth Microdilution and Disk Diffusion Susceptibility Testing.....................................................................34 Table 15. Summary of Testing Conditions and QC Recommendations for Infrequently Isolated or Fastidious Bacteria................................................................................................................................36 Table 16. Acceptable Limits for Quality Control Strains Used to Monitor Accuracy of Minimal Inhibitory Concentrations (MICs) (µg/mL) of Nonfastidious Organisms (Using Cation-Adjusted Mueller-Hinton Medium Without Blood or Other Supplements).........................................................37 Table 16A. Acceptable Limits for Streptococcus pneumoniae ATCC® 49619 Used to Monitor Accuracy of Minimal Inhibitory Concentrations (MICs) (µg/mL) (Using Cation-Adjusted MuellerHinton Broth With Lysed Horse Blood [2.5 to 5% v/v])......................................................................38 Table 16B. Acceptable Limits for Quality Control Strains Used to Monitor Accuracy of Broth Microdilution Minimal Inhibitory Concentrations (MICs) (µg/mL) of Campylobacter jejuni ATCC® 33560 (Using Cation-Adjusted Mueller-Hinton Broth With Lysed Horse Blood [2.5 to 5% v/v])......39 Table 17. Acceptable Limits for Quality Control Strains Used to Monitor Accuracy of Disk Diffusion Testing of Nonfastidious Organisms (Using Mueller-Hinton Medium Without Blood or Other Supplements) ..............................................................................................................................40 Table 17A. Acceptable Limits for Streptococcus pneumoniae ATCC® 49619 Used to Monitor Accuracy of Disk Diffusion Testing .....................................................................................................41 Glossary I (Part 1). -lactams: Class and Subclass Designation and Generic Name............................42 vi

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Contents (Continued)

Glossary I (Part 2). Non--lactams: Class and Subclass Designation and Generic Name ...................43 Glossary II. Abbreviations/Routes of Administration/Drug Class for Antimicrobial Agents Listed in CLSI Document M100......................................................................................................................44 Additional References...........................................................................................................................47 Summary of Consensus Comments and Committee Responses ...........................................................57 The Quality System Approach..............................................................................................................60 Related CLSI/NCCLS Publications ......................................................................................................61

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Foreword

This document was developed for the purpose of providing guidance to clinical microbiology laboratories regarding the performance of standardized susceptibility testing, when needed, of infrequently isolated or fastidious bacteria that are not presently included in the most current editions of CLSI/NCCLS documents M2--Performance Standards for Antimicrobial Disk Susceptibility Tests, M7--Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically, or M11--Methods for Antimicrobial Susceptibility Testing of Anaerobic Bacteria. Some of the organisms included herein are aerobic gram-negative bacilli that are not members of the family Enterobacteriaceae, but may be tested by the standard CLSI broth microdilution or disk diffusion methods in the same manner as the much more common Enterobacteriaceae isolates. Some aerobic gram-positive cocci and bacilli that are encountered periodically by clinical laboratories can likewise be tested reliably by the standard CLSI MIC or disk diffusion test methods in a manner analogous to Staphylococcus or Enterococcus spp. In addition, several genera of fastidious gram-positive and gram-negative bacteria can be tested in the same manner as the streptococci, using blood-supplemented Mueller-Hinton media. For the purpose of this document, the term fastidious is used to describe bacteria that require media supplemented with blood or blood components and that possibly need an atmosphere other than ambient air (e.g., with 5% CO2) for acceptable growth. Because the standard CLSI media, reagents, and procedures can be used to test the organisms included in this guideline, the quality control procedures, strains, and acceptable zone diameter and MIC limits that have been established through previous rigorous studies can be utilized for tests with the less common organisms that are included in this document. The working group used a thorough search of the published literature in conjunction with the clinical experience of the members to apply or adapt interpretive criteria or breakpoints from other organisms that could best be applied to the interpretation of tests of the less common organisms in this document. Users of the guideline should be aware that the very extensive microbiological, clinical, and pharmacodynamic databases normally employed for setting breakpoints by CLSI did not exist for the collection of "orphan" organisms described in this document. It is important for users of M45-A to recognize that commercial susceptibility testing devices are not addressed in this guideline. The methods described herein are generic reference procedures that can be used for routine susceptibility testing by clinical laboratories, or that can be used by clinical laboratories to evaluate commercial devices for possible routine use. Results generated by the CLSI reference methods are used by the United States Food and Drug Administration to evaluate the performance of commercial systems before clearance is given for marketing in the United States. Clearance by the FDA indicates that the agency concludes that commercial devices provide susceptibility results that are substantially equivalent to results generated using the CLSI reference methods for the organisms and antimicrobial agents described in the manufacturer's approved package insert. Some laboratories could find that a commercial dilution, antibiotic gradient, colorimetric, turbidimetric, fluorometric, or other method is suitable for selective or routine use. Key Words Agar dilution, antimicrobial agent, antimicrobial susceptibility, broth dilution, disk diffusion, microdilution, minimal inhibitory concentration (MIC), susceptibility testing

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Methods for Antimicrobial Dilution and Disk Susceptibility Testing of Infrequently Isolated or Fastidious Bacteria; Approved Guideline

1 Scope

CLSI documents M2--Performance Standards for Antimicrobial Disk Susceptibility Tests and M7-- Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically describe standardized methods for antimicrobial susceptibility testing of common aerobic bacteria, including some fastidious organisms or potential agents of bioterrorism. However, there are a number of less frequently encountered or fastidious bacteria that are not addressed in M2, M7, and M100--Performance Standards for Antimicrobial Susceptibility Testing. Some of these are organisms that may cause serious infections (e.g., infective endocarditis), infections associated with trauma and environmental contamination, or device-associated infections in immunocompromised or postsurgical patients (e.g., intravascular catheters, implanted devices, central nervous system shunts). Key gram-positive organisms include Corynebacterium spp., Bacillus spp. (not B. anthracis), and several genera that have intrinsic vancomycin resistance. Nonfastidious gram-negative bacteria include Aeromonas spp., Plesiomonas spp., Vibrio spp., and Moraxella catarrhalis. The fastidious gram-negative bacilli include the HACEK group, Campylobacter, and Pasteurella spp. Organisms considered to be members of the HACEK group are the Aphrophilus cluster of the genus Haemophilus (i.e., H. aphrophilus, H. paraphrophilus, H. segnis), Actinobacillus actinomycetemcomitans, Cardiobacterium spp., Eikenella corrodens, and Kingella spp. Capnocytophaga spp. are outside the scope of this document because of the lack of suitable methods for broth dilution or disk diffusion susceptibility testing. The Capnocytophaga spp. frequently produce -lactamase, but they are generally susceptible to -lactam/-lactamase inhibitor combinations, clindamycin, imipenem, and linezolid. Fastidious gram-positive bacteria that may cause endocarditis include Abiotrophia spp. and Granulicatella spp. Acquired antimicrobial resistance mechanisms have been reported in many of these organisms, and the medical literature includes descriptions of susceptibility results derived from use of standard CLSI methods or certain nonstandard procedures. Because infections due to organisms addressed in M45 occur less frequently than many of the organisms presently covered in CLSI documents M2 and M7, and the fact that many of the antimicrobial agents of interest have been marketed for a number of years, it is not reasonable to expect the intensive CLSI/NCCLS document M23-specified studies (Development of In Vitro Susceptibility Testing Criteria and Quality Control Parameters) to be conducted on this special group of organisms. Instead, the goal of this document is to propose test conditions and interpretive criteria based upon a careful review of published microbiological data (distributions of MICs), and the extant clinical literature regarding therapy for these organisms, and in a few instances, a review of existing pharmacokinetic data on the drugs of interest. In some cases, limited in vitro testing was performed. It is hoped that this CLSI guideline will assist clinical microbiology laboratories in determining an approach for testing these unusual organisms that is relevant to their individual practice settings.

2

Introduction

CLSI documents M2 and M7 describe reference and standardized methods for antimicrobial susceptibility testing of common, rapidly growing aerobic bacteria, including staphylococci, enterococci, members of the Enterobacteriaceae, Pseudomonas spp., and Acinetobacter spp., Burkholderia cepacia, and Stenotrophomonas maltophilia (in addition to a few other nonglucose-fermentative gram-negative bacilli). These documents also include standard susceptibility testing methods, quality control values, and specific breakpoints for several fastidious bacterial species, including Haemophilus influenzae, Neisseria

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gonorrhoeae, Neisseria meningitidis, and Streptococcus spp. In addition, the standards include a limited amount of information regarding the testing of Helicobacter pylori, Vibrio cholerae, and several potential agents of bioterrorism (i.e., Bacillus anthracis, Yersinia pestis, Burkholderia mallei, B. pseudomallei, Francisella tularensis, and Brucella spp.). Despite this extensive list of organisms included in CLSI documents M2 and M7, there are a number of genera of bacteria isolated periodically by clinical microbiology laboratories from human diagnostic specimens for which there are no current CLSI standards. Organisms that presently lack defined methods for susceptibility testing and interpretive criteria include various Coryneform bacteria, Bacillus spp. (other than B. anthracis), Abiotrophia and Granulicatella spp., several genera of gram-positive bacteria with intrinsic glycopeptide resistance (e.g., Erysipelothrix spp., Lactobacillus spp., Leuconostoc spp., Pediococcus spp.), as well as several species of fastidious gram-negative bacteria (e.g., HACEK group organisms, and Pasteurella spp.). In addition, more detailed guidance for test performance and interpretation are needed, especially breakpoints for Listeria spp., Aeromonas spp., Plesiomonas spp., Vibrio spp., Moraxella catarrhalis and Campylobacter spp. The lack of test methods or interpretive criteria has made it difficult to assess the frequency of acquired resistance in these less frequently isolated or fastidious organisms, and has discouraged the testing of individual patient isolates by clinical laboratories. However, concerns have been raised that resistance exists in certain of these organisms, and that laboratories should be prepared to test them when appropriate.1,2 Resistance Mechanisms in Gram-Positive Rods Bacillus cereus and B. thuringiensis have long been noted as producers of a potent broad-spectrum lactamase that affects penicillins and cephalosporins.3 However, these related species are often susceptible to several other drug classes including vancomycin, aminoglycosides, macrolides, and quinolones that might be used to treat ocular or wound infections. Among the Corynebacterium spp., C. jeikeium and C. urealyticum are often multidrug resistant, including resistance to -lactams, macrolides, and aminoglycosides.4 Even C. diphtheriae may be macrolide and rifampin-resistant, while C. pseudodiphtheriticum and C. striatum may possess erm genes and be resistant to macrolides and lincosamides.4 Further, some strains of C. striatum are said to be resistant to tetracyclines and quinolones.4 The related bacilli, Arcanobacterium and Arthrobacter, have been reported to be resistant to aminoglycosides and quinolones,4 and Brevibacterium spp. may demonstrate reduced lactam susceptibility. Turicella spp. may be macrolide- and clindamycin-resistant.4 Erysipelothrix rhusiopathiae and most Lactobacillus spp. isolates are intrinsically resistant to vancomycin; and the uncommon species, Microbacterium resistans and Leifsonia aquatica, have been reported to have diminished vancomycin susceptibility.5,6 Resistance in Infrequently Isolated or Fastidious Gram-Positive Cocci Leuconostoc and Pediococcus are intrinsically resistant to vancomycin, but are usually susceptible to lactams, chloramphenicol, tetracyclines, and aminoglycosides, although Leuconostoc can be resistant to carbapenems and cephalosporins.7 Abiotrophia and Granulicatella (formerly nutritionally deficient streptococci) may demonstrate diminished susceptibility to penicillin, resulting in greater difficulty in treatment of patients with endocarditis, and in one case, fluoroquinolone resistance was reported in an isolate from an immunosuppressed patient.8 Infrequently Isolated Nonfastidious Gram-Negative Rods There are a few nonfastidious gram-negative rods that are not addressed in M2, M7, and M100 but that are capable of being grown using unsupplemented Mueller-Hinton medium. Aeromonas spp. may produce as many as three different -lactamases, including a carbapenemase, that result in resistance to ampicillin, but variable susceptibility to cephalosporins.9 The significance of the carbapenemase produced 2

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M45-A

Related CLSI/NCCLS Publications

M2-A9 Performance Standards for Antimicrobial Disk Susceptibility Tests; Approved Standard--Ninth Edition (2006). This document contains the current CLSI-recommended methods for disk susceptibility testing, criteria for quality control testing, and updated tables for interpretive zone diameters. Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically; Approved Standard--Seventh Edition (2006). This document addresses reference methods for the determination of minimal inhibitory concentrations (MICs) of aerobic bacteria by broth macrodilution, broth microdilution, and agar dilution. Development of In Vitro Susceptibility Testing Criteria and Quality Control Parameters; Approved Guideline--Second Edition (2001). This document addresses the required and recommended data needed for the selection of appropriate interpretive standards and quality control guidelines for antimicrobial agents. Performance Standards for Antimicrobial Susceptibility Testing; Sixteenth Informational Supplement (2006). This document provides updated tables for the Clinical and Laboratory Standards Institute (CLSI) antimicrobial susceptibility testing standards M2-A9 and M7-A7.

M7-A7

M23-A2

M100-S16

Proposed-level documents are being advanced through the Clinical and Laboratory Standards Institute consensus process; therefore, readers should refer to the most current editions.

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