Susceptibility of Extended-Spectrum-β-Lactamase-Producing Enterobacteriaceae According to the New CLSI Breakpoints

Wang, Peng; Hu, Fupin; Xiong, Zeng; Ye, Xinyu; Zhu, Demei; Wang, Yun F.; Wang, Minggui

doi:10.1128/jcm.00222-11

Cited by 57 publications

(35 citation statements)

References 27 publications

(22 reference statements)

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“…In response to these limitations, the CLSI elected to lower the susceptibility breakpoints for several cephalosporins in an attempt to eliminate the need for phenotypic ESBL tests (55). Despite the lowered breakpoints, strains harboring bla CTX-M ESBLs may still test as susceptible to ceftazidime, cefepime, and aztreonam (56). Specifically, 14% to 45% of E. coli isolates and 85% to 96% of P. mirabilis isolates harboring bla CTX-M tested as susceptible to these antibiotics based on the lower breakpoints (56).…”

Section: Discussionmentioning

confidence: 99%

“…Despite the lowered breakpoints, strains harboring bla CTX-M ESBLs may still test as susceptible to ceftazidime, cefepime, and aztreonam (56). Specifically, 14% to 45% of E. coli isolates and 85% to 96% of P. mirabilis isolates harboring bla CTX-M tested as susceptible to these antibiotics based on the lower breakpoints (56). This potential undercalling of resistance was especially pronounced in isolates harboring CTX-M-9 enzymes (56).…”

Section: Discussionmentioning

confidence: 99%

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Identification of Gram-Negative Bacteria and Genetic Resistance Determinants from Positive Blood Culture Broths by Use of the Verigene Gram-Negative Blood Culture Multiplex Microarray-Based Molecular Assay

Lopansri²,

et al. 2015

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Bloodstream infection is a serious condition associated with significant morbidity and mortality. The outcome of these infections can be positively affected by the early implementation of effective antibiotic therapy based on the identification of the infecting organism and genetic markers associated with antibiotic resistance. In this study, we evaluated the microarray-based Verigene Gram-negative blood culture (BC-GN) assay in the identification of 8 genus or species targets and 6 genetic resistance determinants in positive blood culture broths. A total of 1,847 blood cultures containing Gram-negative organisms were tested using the BC-GN assay. This comprised 729 prospective fresh, 781 prospective or retrospective frozen, and 337 simulated cultures representing 7 types of aerobic culture media. The results were compared to those with standard bacterial culture and biochemical identification with nucleic acid sequence confirmation of the resistance determinants. Among monomicrobial cultures, the positive percent agreement (PPA) of the BC-GN assay with the reference method was as follows; Escherichia coli, 100%; Klebsiella pneumoniae, 92.9%; Klebsiella oxytoca, 95.5%; Enterobacter spp., 99.3%; Pseudomonas aeruginosa, 98.9%; Proteus spp., 100%; Acinetobacter spp., 98.4%; and Citrobacter spp., 100%. All organism identification targets demonstrated >99.5% negative percent agreement (NPA) with the reference method. Of note, 25/26 cultures containing K. pneumoniae that were reported as not detected by the BC-GN assay were subsequently identified as Klebsiella variicola. The PPA for identification of resistance determinants was as follows; bla CTX-M , 98.9%; bla KPC , 100%; bla NDM , 96.2%; bla OXA , 94.3%; bla VIM , 100%; and bla IMP , 100%. All resistance determinant targets demonstrated >99.9% NPA. Among polymicrobial specimens, the BC-GN assay correctly identified at least one organism in 95.4% of the broths and correctly identified all organisms present in 54.5% of the broths. The sample-to-result processing and automated reading of the detection microarray results enables results within 2 h of culture positivity. Bloodstream infection (BSI) is a serious and life-threatening condition that has been associated with 25% to 80% mortality (1, 2). The outcome of BSI can be dependent on host factors, such as underlying comorbidities, and microbiological factors, including the type of infecting organism and its susceptibility to antibiotics. It is estimated that up to 30% of hospital-acquired BSI are attributable to Gram-negative organisms (3). Infections caused by these bacteria, particularly when acquired in the hospital, have been associated with 15% to 29% increased crude mortality rates compared with those of the case controls (4, 5). This is particularly true for infections with multidrug-resistant organisms, including those harboring extended-spectrum ␤-lactamases (ESBLs) or carbapenemases, which have been associated with prolonged hospital stay and increased 30-day mortality (6, 7).Perhaps the most important in...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Identification of Gram-Negative Bacteria and Genetic Resistance Determinants from Positive Blood Culture Broths by Use of the Verigene Gram-Negative Blood Culture Multiplex Microarray-Based Molecular Assay

Lopansri²,

et al. 2015

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“…False positives for carbapenemase production was found using MHT in 11 strains. According to Wang et al (2011), the false positive results observed using MHT probably occur due to lowlevel hydrolysis of ertapenem by extended-spectrum blactamases (ESBLs), particularly those of the CTX-M type. Although carbapenemase-encoding genes were not identified in 11 K. pneumoniae strains, bla CTX-M and bla SHV genes were detected.…”

Section: Strain Mht Maldi-tof Msmentioning

confidence: 99%

Risk factors for KPC-producing Klebsiella pneumoniae: watch out for surgery

Silva

Maciel

Sacchi

et al. 2016

Journal of Medical Microbiology

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This study describes the molecular characteristics and risk factors associated with carbapenemresistant Klebsiella pneumoniae strains. Risk factors associated with KPC-producing K. pneumoniae strains were investigated in this case-control study from May 2011 to May 2013. Bacterial identification was performed by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Antimicrobial susceptibility was determined by broth microdilution. Carbapenemase production was assessed by both modified Hodge test (MHT) and ertapenem hydrolysis using MALDI-TOF MS. The presence of b-lactamase-encoding genes was evaluated by PCR and DNA sequencing. Alterations in genes encoding K. pneumoniae outer membrane proteins were analysed by PCR and DNA sequencing as well as SDS-PAGE. Genetic relatedness among strains was determined by pulsed-field gel electrophoresis. This study included 94 patients. Longer hospitalisation, mechanical ventilation, catheters, and previous surgery were associated with KPC-producing K. pneumoniae. Sixty-eight strains showed resistance to carbapenems. Carbapenemase production was detected by MHT in 67 K. pneumoniae strains and by MALDI-TOF MS in 57. The presence of the bla KPC-2 gene was identified in 57 strains. The bla KPC-2 gene was not found in 11 carbapenem-resistant K. pneumoniae; instead, the bla CTX-M-1-like , bla CTX-M-2-like , bla CTX-M-8 like , bla CTX-M-14-like and bla SHV-like genes associated with OmpK35 and OmpK36 alterations were observed. Thirty-three KPC-producing K. pneumoniae strains were clonally related, and patients infected with these strains had a higher mortality rate (78.78 %). Our results show that KPC-producing K. pneumoniae was associated with several healthcare-related risk factors, including recent surgery.

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“…Among the E. coli isolates examined, 8.0%, 58.0%, and 52.7% were called susceptible to cefotaxime, ceftazidime, and cefepime, respectively; among the K. pneumoniae isolates, 2.3%, 7.0%, and 58.1% were called susceptible to the aforementioned ESCs. Wang et al found that, with the new breakpoints, 41.8 to 45.6% of ESBL-producing E. coli strains appeared to be susceptible to ceftazidime and cefepime and 20.1% of ESBL-producing K. pneumoniae strains were susceptible to cefepime (10).…”

mentioning

confidence: 99%

Incidence of Extended-Spectrum-β-Lactamase-Producing Escherichia coli and Klebsiella pneumoniae Isolates That Test Susceptible to Cephalosporins and Aztreonam by the Revised CLSI Breakpoints

2014

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The incidence of aztreonam and cephalosporin susceptibility, determined using the revised CLSI breakpoints, for extendedspectrum-␤-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae isolates was evaluated. Our analysis showed that results for aztreonam and/or >1 cephalosporin were reported as susceptible or intermediate for 89.2% of ESBLproducing E coli isolates (569/638 isolates) and 67.7% of ESBL-producing K. pneumoniae isolates (155/229 isolates). Extended-spectrum-␤-lactamase (ESBL)-producing Enterobacteriaceae strains represent a challenging problem for health care providers, particularly in acute-care and long-term-care facilities and more recently in community-acquired infections (1-5). ESBL enzymes are capable of inactivating penicillins, aztreonam, cephalosporins, and ␤-lactamase inhibitors, which limits the number of effective antibiotics for treatment (1,2,4,5).The presence of an ESBL is suspected in Escherichia coli and Klebsiella pneumoniae infections when resistance to one or more of the extended-spectrum cephalosporins (ESCs) (cefotaxime, ceftazidime, ceftriaxone, or cefepime) is detected (1, 2, 4). Based on pre-2010 guidelines from the Clinical and Laboratory Standards Institute (CLSI) (Wayne, PA), laboratories then confirmed the presence of an ESBL using labor-intensive manual methods. This supplemental testing often delayed ESBL identification by 24 to 48 h. Confirmatory testing for ESBLs has also been incorporated into automated susceptibility test systems. Since resistance to some ESCs and aztreonam may not always be detected by in vitro methods, strains were reported as resistant to all penicillins, cephalosporins (excluding the cephamycins), and aztreonam based on positive confirmatory test results, independent of the initial susceptibility test results. These guidelines were followed to prevent strains being reported inadvertently as being susceptible to ESCs and aztreonam, leading to potentially inappropriate treatment.In 2010, the CLSI Antibiotic Subcommittee lowered the MIC breakpoints and increased the disk diffusion size criteria for reporting of aztreonam, cefazolin, cefotaxime, ceftizoxime, ceftriaxone, and ceftazidime results. Interpretive criteria for cefuroxime and cefepime were not changed, because the committee determined that the available data did not support any changes in the breakpoints for these two drugs (6). In 2014, the CLSI recommended changing the MIC breakpoints for cefepime to Ͻ2 g/ml for sensitive, 4 to 8 g/ml for sensitive dose dependent (SDD), and Ͼ16 g/ml for resistant (7). The CLSI advises that treatment of ESBL-producing strains can be predicted solely on the basis of MIC values, regardless of the underlying resistance mechanisms. More-stringent interpretive criteria would eliminate the need for confirmatory testing for ESBL, and results could be reported as tested. In theory, this would decrease the time needed to identify ESBL-producing Enterobacteriaceae and the costs associated with additional laboratory work.There were significant conc...

show abstract

Susceptibility of Extended-Spectrum-β-Lactamase-Producing Enterobacteriaceae According to the New CLSI Breakpoints

Cited by 57 publications

References 27 publications

Identification of Gram-Negative Bacteria and Genetic Resistance Determinants from Positive Blood Culture Broths by Use of the Verigene Gram-Negative Blood Culture Multiplex Microarray-Based Molecular Assay

Identification of Gram-Negative Bacteria and Genetic Resistance Determinants from Positive Blood Culture Broths by Use of the Verigene Gram-Negative Blood Culture Multiplex Microarray-Based Molecular Assay

Risk factors for KPC-producing Klebsiella pneumoniae: watch out for surgery

Incidence of Extended-Spectrum-β-Lactamase-Producing Escherichia coli and Klebsiella pneumoniae Isolates That Test Susceptible to Cephalosporins and Aztreonam by the Revised CLSI Breakpoints

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