药物敏感实验标准 CLSI MR08-2020

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© Clinical and Laboratory Standards Institute. All rights reserved.
Romney M. Humphries, PhD, D(ABMM)
Accelerate Diagnostics, Inc.
USA
Clifford Mintz
USA
Audrey N. Schuetz, MD, MPH, D(ABMM)
Mayo Clinic
USA
On behalf of the CLSI Oral Cephalosporin Ad Hoc Working Group and the CLSI Subcommittee on
Antimicrobial Susceptibility Testing
1 Foreword
The Clinical and Laboratory Standards institute (CLSI) is a not-for-prot membership organization that brings together the varied
perspectives and expertise of the worldwide laboratory community for the advancement of a common cause: to foster excellence
in laboratory medicine by developing and implementing medical laboratory standards and guidelines that help laboratories fulll
their responsibilities with efficiency, effectiveness, and global applicability.
Using the CLSI voluntary consensus process, the Subcommittee on Antimicrobial Susceptibility Testing develops standards that
promote accurate antimicrobial susceptibility testing and appropriate reporting. The subcommittee reviews data from various
sources and studies (eg, in vitro, pharmacokinetic-pharmacodynamic, and clinical studies) to establish antimicrobial susceptibility
test methods, breakpoints, and quality control (QC) ranges.
The details of the necessary and recommended data for selecting appropriate breakpoints and QC ranges, and how the data are
presented for evaluation, are described in CLSI document M23.1 CLSI antibacterial breakpoints are provided in CLSI documents
M1002 and M45.3
Over time, a microorganism’s susceptibility to an antimicrobial agent may decrease, resulting in a lack of clinical efficacy and/
or safety. In addition, microbiological methods, QC parameters, and the manner in which breakpoints are established may be
rened to ensure more accurate results. Because of these types of changes, CLSI continually monitors and updates information
in its documents. Although CLSI standards and guidelines are developed using the most current information available at the time,
the eld of science and medicine is always changing; therefore, standards and guidelines should always be used in conjunction
with clinical judgment, current knowledge, and clinically relevant laboratory test results to guide patient treatment. For more
information, visit www.clsi.org.
This CLSI rationale document is based on data compiled by the CLSI Oral Cephalosporin Ad Hoc Working Group to reassess
cefazolin minimal inhibitory concentration (MIC) breakpoints for Enterobacterales for uncomplicated urinary tract infections
(UTIs) and introduce new intermediate and resistant MIC breakpoints supported by higher dosage treatment regimens for
cefazolin.
Cefazolin Breakpoints for Enterobacterales
(Uncomplicated Urinary Tract Infections)
CLSI rationale document MR08
March 2020
1
Cefazolin Breakpoints for Enterobacterales (Uncomplicated Urinary Tract Infections)
© Clinical and Laboratory Standards Institute. All rights reserved. 2
2 A Note on Terminology
As of January 2020, the term Enterobacteriaceae has been replaced with Enterobacterales. For consistency with CLSI document
M100,2 Enterobacterales is used in MR08.
3 Introduction
Cephalosporins are a large class of antimicrobial agents that contain a six-membered dihydrothiazine ring moiety fused to a
β-lactam ring with broad-spectrum antimicrobial activity against gram-positive and gram-negative bacteria. These compounds
are derivatives of 7-aminocephalosporanic acid, with various modications at several ring positions that result in differences in
antimicrobial activity, β-lactamase stability, and pharmacokinetic (PK) properties.4 The bactericidal action of cephalosporins is
mediated by their strong binding affinities for penicillin-binding proteins (PBPs). This affinity leads to the inhibition of bacterial cell
wall synthesis and, ultimately, cell death.4
Cefazolin is a parenterally administered, rst-generation cephalosporin that exhibits bactericidal activity against a wide variety
of gram-positive and gram-negative bacteria, including methicillin-susceptible Staphylococcus aureus (MSSA), coagulase-negative
Staphylococcus spp., penicillin-susceptible Streptococcus pneumoniae, Streptococcus spp., Moraxella catarrhalis, Escherichia coli,
Klebsiella pneumoniae, and Proteus mirabilis.5
Cefazolin is approved by the US Food and Drug Administration for the treatment of6:
• Respiratory tract infections caused by S. pneumoniae, Klebsiella spp., Haemophilus inuenzae, S. aureus, and group A
β-hemolytic streptococci
• UTIs caused by E. coli, P. mirabilis, Klebsiella spp., and some strains of Enterobacter and Enterococcus
• Skin and skin structure infections caused by S. aureus, group A β-hemolytic streptococci, and other strains of Streptococcus
• Biliary tract infections caused by E. coli, Streptococcus, P. mirabilis, Klebsiella spp., and S. aureus
• Bone and joint infections caused by S. aureus
• Genital infections caused by E. coli, P. mirabilis, Klebsiella spp., and some strains of Enterococcus
• Septicemia caused by S. pneumoniae, S. aureus, P. mirabilis, E. coli, and Klebsiella spp.
• Endocarditis caused by S. aureus and group A β-hemolytic streptococci
• Perioperative prophylaxis
The FDA-approved parenteral administration schedule for cefazolin in adult patients is shown in Table 1.
Document #/Version #: S-080/2.0 Effective Date: 1 August 2018
Endocarditis caused by S. aureus and group A β-hemolytic streptococci
Perioperative prophylaxis
The FDA-approved parenteral administration schedule for cefazolin in adult patients is shown
in Table 1.
Table 1. Recommended Dosage Schedule for Cefazolin in Adult Patients6 (FDA. Cefazolin for
injection USP prescribing information.)
Type of Infection Dosage
Moderate to severe infections 0.5-1 g every 6 to 8 hours
Mild infections caused by susceptible
gram-positive streptococci
250-500 mg every 8 hours
Acute uncomplicated UTIs 1 g every 12 hours
Pneumococcal pneumonia 500 mg every 12 hours
Severe life-threatening infections
(eg, endocarditis, septicemia)
1-1.5 g every 6 hours
Abbreviation: UTI, urinary tract infection.
The predominant mechanisms of resistance to cefazolin in gram-negative bacteria include
decreased bacterial uptake of cefazolin into the cell or production of β-lactamases that
enzymatically hydrolyze and inactivate β-lactam antibiotics.7 Cefazolin is a useful de-escalation
agent for the treatment of many invasive and noninvasive infections caused by susceptible
isolates of E. coli, Klebsiella spp. (excluding Klebsiella aerogenes), and P. mirabilis.8
CLSI has established cefazolin as a surrogate agent to predict the activity of the oral
cephalosporins (ie, cefaclor, cefdinir, cefpodoxime, cefprozil, cefuroxime, cephalexin, and
loracarbef) in antimicrobial susceptibility testing (AST) against Enterobacterales isolates
causing uncomplicated UTIs.9,10 Data demonstrate that a cefazolin MIC ≤ 16 µg/mL (correlate
zone diameter ≥ 15 mm) is an excellent predictor (97% to 100% accuracy) of susceptibility to
these agents when testing E. coli, K. pneumoniae, and P. mirabilis for intended treatment of
uncomplicated UTIs.10 Cefdinir, cefpodoxime, and cefuroxime may be tested individually,
because some isolates may be susceptible to these agents but resistant to cefazolin when
applying the uncomplicated UTI cefazolin breakpoints.10
This rationale document summarizes interpretative data and information used by CLSI to
establish cefazolin as a surrogate agent for oral cephalosporins, including cefaclor, cefdinir,
cefpodoxime, cefprozil, cefuroxime, cephalexin, and loracarbef10 (see Additional Resources,
June 2013 CLSI meeting). Current CLSI urine-specific breakpoints are shown in Table 2.
Cefazolin Breakpoints for Enterobacterales (Uncomplicated Urinary Tract Infections)
© Clinical and Laboratory Standards Institute. All rights reserved. 3
The predominant mechanisms of resistance to cefazolin in gram-negative bacteria include decreased bacterial uptake of cefazolin
into the cell or production of β-lactamases that enzymatically hydrolyze and inactivate β-lactam antibiotics.7 Cefazolin is a
useful de-escalation agent for the treatment of many invasive and noninvasive infections caused by susceptible isolates of E. coli,
Klebsiella spp. (excluding Klebsiella aerogenes), and P. mirabilis.8
CLSI has established cefazolin as a surrogate agent to predict the activity of the oral cephalosporins (ie, cefaclor, cefdinir,
cefpodoxime, cefprozil, cefuroxime, cephalexin, and loracarbef) in antimicrobial susceptibility testing (AST) against
Enterobacterales isolates causing uncomplicated UTIs.9,10 Data demonstrate that a cefazolin MIC ≤ 16 µg/mL (correlate zone
diameter ≥ 15 mm) is an excellent predictor (97% to 100% accuracy) of susceptibility to these agents when testing E. coli,
K. pneumoniae, and P. mirabilis for intended treatment of uncomplicated UTIs.10 Cefdinir, cefpodoxime, and cefuroxime may
be tested individually, because some isolates may be susceptible to these agents but resistant to cefazolin when applying the
uncomplicated UTI cefazolin breakpoints.10
This rationale document summarizes interpretative data and information used by CLSI to establish cefazolin as a surrogate
agent for oral cephalosporins, including cefaclor, cefdinir, cefpodoxime, cefprozil, cefuroxime, cephalexin, and loracarbef10 (see
Additional Resources, June 2013 CLSI meeting). Current CLSI urine-specic breakpoints are shown in Table 2.
Document #/Version #: S-080/2.0 Effective Date: 1 August 2018
Table 2. Current CLSI Urine-Specific Cefazolin Breakpointsa
Organism Group
Antimicrobial
Agent
Interpretive Categories and MIC Breakpoints,
µg/mLb,c
SSDD I
R
Enterobacterales
(E. coli,
K. pneumoniae,
P. mirabilis)
Cefazolin ≤ 16 - - ≥ 32
Abbreviations: I, intermediate; R, resistant; S, susceptible; SDD, susceptible-dose dependent.
a Last reviewed June 2013; first published in CLSI document M100, 24th ed.
b These breakpoints can be used to predict susceptibility to cefaclor, cefdinir, cefpodoxime, cefprozil, cefuroxime,
cephalexin, and loracarbef.
c Breakpoints are based on a dosage regimen of 1 g administered every 12 h.
4 Standard Dosages and Pharmacokinetic Data
The standard dosages and PK data for cefaclor, cefazolin, cefdinir, cefpodoxime, cefprozil,
cefuroxime, cephalexin, and loracarbef are listed in Table 3.
Table 3. Dosages Used for Breakpoint Determination
Antimicrobial Agent Dosages
Cefaclo
r
11 250-500 mg every 8 hours
Cefazolin6 1–2 g (IM or IV) every 8 hours (1 g every 12 hours for
u
ncomplicated UTIs), 2 g every 8 hours
Cefdini
r
12,13 300 mg every 12 hours or 600 mg every 24 hours
Cefpodoxime14,15 100-200 mg every 12 hours
Cefprozil16 250–500 mg every 12 hours
Cefuroxime17,18 125-500 mg every 12 hours
Cephalexin19,20 250-1000 mg every 6 hours
Loracarbef21 200–400 mg every 12 to every 24 hours (200 mg
every 24 hours for uncomplicated UTIs)
Abbreviations: IM, intramuscular; IV, intravenous; UTI, urinary tract infection.
Document #/Version #: S-080/2.0 Effective Date: 1 August 2018
Table 2. Current CLSI Urine-Specific Cefazolin Breakpointsa
Organism Group
Antimicrobial
Agent
Interpretive Categories and MIC Breakpoints,
µg/mLb,c
SSDD I
R
Enterobacterales
(E. coli,
K. pneumoniae,
P. mirabilis)
Cefazolin ≤ 16 - - ≥ 32
Abbreviations: I, intermediate; R, resistant; S, susceptible; SDD, susceptible-dose dependent.
a Last reviewed June 2013; first published in CLSI document M100, 24th ed.
b These breakpoints can be used to predict susceptibility to cefaclor, cefdinir, cefpodoxime, cefprozil, cefuroxime,
cephalexin, and loracarbef.
c Breakpoints are based on a dosage regimen of 1 g administered every 12 h.
4 Standard Dosages and Pharmacokinetic Data
The standard dosages and PK data for cefaclor, cefazolin, cefdinir, cefpodoxime, cefprozil,
cefuroxime, cephalexin, and loracarbef are listed in Table 3.
Table 3. Dosages Used for Breakpoint Determination
Antimicrobial Agent Dosages
Cefaclo
r
11 250-500 mg every 8 hours
Cefazolin6 1–2 g (IM or IV) every 8 hours (1 g every 12 hours for
u
ncomplicated UTIs), 2 g every 8 hours
Cefdini
r
12,13 300 mg every 12 hours or 600 mg every 24 hours
Cefpodoxime14,15 100-200 mg every 12 hours
Cefprozil16 250–500 mg every 12 hours
Cefuroxime17,18 125-500 mg every 12 hours
Cephalexin19,20 250-1000 mg every 6 hours
Loracarbef21 200–400 mg every 12 to every 24 hours (200 mg
every 24 hours for uncomplicated UTIs)
Abbreviations: IM, intramuscular; IV, intravenous; UTI, urinary tract infection.
4 Standard Dosages and Pharmacokinetic Data
The standard dosages and PK data for cefaclor, cefazolin, cefdinir, cefpodoxime, cefprozil, cefuroxime, cephalexin, and loracarbef
are listed in Table 3.
摘要：

CLSI MR08-2020是临床与实验室标准协会（CLSI）发布的最新版《药物敏感实验标准》文件，专用于规范化微生物药敏试验的操作流程、质控要求及结果判读。该标准涵盖了抗菌药物最低抑菌浓度（MIC）测定、纸片扩散法、稀释法及自动化系统验证等关键环节，为临床微生物实验室、制药研发机构及感染病诊疗提供了权威的技术依据。遵循MR08-2020标准可确保药敏试验结果的准确性与可重复性，有效指导抗生素合理使用，减少耐药菌株的传播。无论是实验室日常质控、新药敏感性评估还是流行病学监测，该标准均是不可或缺的

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