Wayne, Pennsylvania, USA-January 2012-The Clinical and
Laboratory Standards Institute (CLSI) recently published updated editions of
its antimicrobial susceptibility testing (AST) standards, Performance Standards
for Antimicrobial Disk Susceptibility Tests; Approved Standard-Eleventh Edition
(M02-A11) and Methods for Dilution Antimicrobial Susceptibility Tests for
Bacteria That Grow Aerobically; Approved Standard-Ninth Edition (M07-A9). In
addition, the annual update of the well-known supplement to these documents,
entitled Performance Standards for Antimicrobial Susceptibility Testing;
Twenty-Second Informational Supplement (M100-S22), is available with the
purchase of M02-A11 and M07-A9.
“Because antimicrobial resistance is acquired over
time, updated standards and guidelines provide the tools to ensure that the
latest knowledge can be used to provide consistent, quality data for patient
care, and for the public health laboratory system,” says Susanne Norris
Zanto, MPH, MLS, SM, Deputy Laboratory Director and Lab Systems Improvement
Manager, Montana DPHHS Laboratory Services Bureau, Helena, Montana, USA.
“The Montana Public Health Laboratory has been able to distribute CLSI
documents to encourage our clinical laboratory colleagues to make appropriate
practice changes to address the public health challenge of emerging bacterial
resistance.”
Elizabeth Palavecino, MD, Associate Director of Pathology,
Director Clinical Microbiology, Wake Forest Baptist
Medical Center,
Winston-Salem, North Carolina, USA,
agrees. “It is important for CLSI to continuously review the M100 document
because new data may support a breakpoint that is different from the one
originally assigned to a particular antimicrobial agent, and the breakpoint may
need to be modified,” she explains. “In addition, the microbiological
activity of an agent or its clinical indications may have changed and therefore
the indication for testing and reporting may need to be reevaluated. It is
critical for me, as director of a clinical microbiology lab, to know that the
CLSI M100 document has been reviewed and updated to provide the most current
information. This process assures me that I can check the latest version of
these documents and give my advice on antimicrobial therapy to my clinical
colleagues.”
M100-S22 provides updates of the latest recommendations for
detecting emerging resistance of aerobic and anaerobic bacteria, arranged in
tabular format. The “breakpoints” included in the supplement are
defined as specific values on the basis of which bacteria can be assigned to
the clinical categories of susceptible, intermediate, or resistant.
“The microbial world is continually evolving and
developing mechanisms of resistance. The timely updates of CLSI standards
assist the clinical microbiology manager in providing the most accurate
susceptibility data to health care providers, and the wealth of information
included in the M100 document is priceless,” says Beth Prouse, MS,
MT(ASCP), Clinical Microbiologist, Peninsula
Regional Medical
Center, Salisbury, Maryland, USA. “The suggested groupings
of antimicrobial agents, comments associated with the interpretive standards,
and information included in the supplemental tables and appendixes are
essential to any clinical laboratory performing antimicrobial susceptibility
testing.”
Dr. Palavecino adds, “I use the M100 document on a
daily basis to review the breakpoints for different organism/drug combinations.
If I receive a request for testing an agent not included in our panel, I know
that I can count on the M100 document to find recommendations on whether to
test and report the agent in question. It is reassuring for clinical
microbiology labs to know that the latest versions of the document contain the
most updated antimicrobial data, including new MIC breakpoints for new agents
that may not be included in routine panels, but that may need to be tested and
reported.”
New or revised interpretive criteria are available for the
following drugs:
- Ertapenem disk diffusion and minimal inhibitory
concentration (MIC) interpretive criteria for Enterobacteriaceae - Ciprofloxacin disk diffusion and MIC interpretive criteria
for reporting against Salmonella typhi and extraintestinal Salmonella spp. only - Piperacillin, piperacillin-tazobactam, ticarcillin, and
ticarcillin-clavulanic acid disk diffusion and MIC interpretive criteria for
Pseudomonas aeruginosa - Doripenem for P. aeruginosa; methicillin-susceptible
staphylococci; Haemophilus influenzae, Haemophilus parainfluenzae,
Streptococcus pneumoniae (MIC only), Streptococcus spp. (©¬-hemolytic and
viridans group MIC only), and anaerobes - Imipenem and meropenem for P. aeruginosa
Added:
-
New penicillin disk diffusion zone-edge test as an additional screening test
for ¥Ã¢-lactamase production in the Staphylococcus aureus group - Cefamandole to the list of antimicrobial agents to which
BLNAR (¥Ã¢-lactamase negative, ampicillin-resistant) strains of H. influenzae
should be considered resistant
Quality control (QC) ranges added for:
- Ceftaroline-avibactam
- Ceftazidime-avibactam
- Doxycycline
- Finafloxacin
- Fusidic acid
- Omadacycline
- Plazomicin
- Solithromycin
- Tedezolid
In addition to publishing CLSI document M100, new versions
of its parent documents, M02 and M07, were also released. Every three years,
these standards are updated by the CLSI Subcommittee on Antimicrobial
Susceptibility Testing and several dedicated working groups to ensure that new
methodology is included in the documents. This methodology is essential to
correctly interpret and use the annual M100 supplement.
Performance Standards for Antimicrobial Disk Susceptibility
Tests; Approved Standard-Eleventh Edition (M02-A11) describes the standard agar
disk diffusion techniques used to determine the in vitro susceptibility of
aerobic bacteria to antimicrobial agents.
Methods for Dilution Antimicrobial Susceptibility Tests for
Bacteria That Grow Aerobically; Approved Standard-Ninth Edition (M07-A9)
outlines reference methods for the determination of MICs of aerobic bacteria by
broth macrodilution, broth microdilution, and agar dilution.
“Disk diffusion is widely used in countries around the
world because this is a standardized method that can be used without the need
for expensive instrumentation. The updated information in M02 is an effective
tool for clinical laboratories using this method for routine susceptibility
and, therefore, it is important that this methodology be revised to include new
mechanisms of resistance or breakpoint interpretation,” explains Dr.
Palavecino. “For laboratories using an automated antimicrobial
susceptibility system, it is very reassuring that the disk diffusion and broth
microdilution methodologies are standardized and available to confirm
resistance patterns or unusual results obtained by the automated systems.
Revision and standardization of these procedures is critically important
because these methods can be used for evaluation and verification of new
panels, upgraded instrumentation, or new reporting ranges, and clinical labs
can have the assurance that the method has been standardized to include the
most current antimicrobial data.”
Updates to M02-A11 and M07-A9 include:
-
Information on a new subclass, cephems, including cephalosporins with
anti-methicillin-resistant S. aureus (MRSA) activity - Nitroimidazoles as a new section, which includes the
antimicrobial agents metronidazole and tinidazole - Oxazolidinones as a new section, which includes the
antimicrobial agent linezolid - Streptogramins as a new section, which includes the
antimicrobial agents quinupristin-dalfopristin and linopristin-flopristin - Additional recommendations for the use of nitrocefin-based
tests or the penicillin disk diffusion zone-edge test for isolates of
Staphylococcus - Additional information on ESBLs (extended-spectrum
¥Ã¢-lactamases) being inhibitor-susceptible enzymes - Additional information on how ¥Ã¢-lactam interpretive
breakpoints are set at MIC values to recognize ESBL activity - Addition of penicillin zone-edge test method as an
alternative method for detection of ¥Ã¢-lactamase in staphylococci
“To improve the public health laboratory system, the
Montana Public Health Laboratory has distributed these CLSI guidelines to
clinical laboratories in the state for the past five years,” Zanto says.
“A biennial survey of AST practices in these laboratories revealed
knowledge increases of up to 64% in specific subject areas in a two-year period
following distribution of CLSI standards and subsequent training.
In addition to the documents themselves, the Antimicrobial
Susceptibility Testing Searchable CD-ROM, AST QC Flowchart Quick Guides, M100
Tables 1A-1C Quick Guide, and the Glossary of Antimicrobial Terms and
Abbreviations Wall Chart for implementing CLSI’s highly acclaimed AST standards
and guidelines have also been updated.
CLSI and the Association of Public Health Laboratories
(APHL) have announced an AST teleconference taking place on February 1, 2012,
1:00-2:30 PM Eastern (US) Time or February 2, 2012, 3:00-4:30 PM Eastern (US)
Time. Janet Hindler, MCLS, MT(ASCP),
Senior Specialist, Clinical Microbiology, UCLA
Medical Center,
Los Angeles, California, USA,
will provide an overview of the M100-S22 tables, as well as discuss updates of
the disk (M02-A11) and MIC (M07-A9) testing standards. There is also a
beginner-level AST teleconference scheduled for January 19, 2012, 1:00-2:00 PM
Eastern (US) Time, entitled, “The Basics: Using CLSI Antimicrobial
Susceptibility Testing Standards.” Register for the upcoming
teleconferences at www.aphl.org/clsi.
CLSI is a volunteer-driven, membership-supported, nonprofit
organization dedicated to developing standards and guidelines for the health
care and medical testing community through a consensus process that balances
the perspectives of industry, government, and the health care professions. For
additional information, visit the CLSI website at www.clsi.org
or call 610.688.0100.
Posted by Sean Fenske, Editor-in-Chief, MDT
