Comparison of different methods of determining β-lactam susceptibility in clinical strains of Pseudomonas aeruginosa

Torres, Eva; Villanueva, Rosa; Bou, Germán

doi:10.1099/jmm.0.005587-0

Cited by 16 publications

(9 citation statements)

References 20 publications

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“…Due to this problem, laboratories might consider primary testing of mucoid isolates by disk diffusion. The most notable errors occurred in P. aeruginosa isolates with piperacillin-tazobactam, as has been seen by others (5,7,11,12). Unlike these previous studies that found piperacillin-tazobactam VME rates ranging from 10.2 to 21.7% (5, 7, 10), we found 0 VMEs and only 3 (4.3%) MEs.…”

Section: Discussioncontrasting

confidence: 55%

Performance of Vitek 2 for Antimicrobial Susceptibility Testing of Acinetobacter baumannii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia with Vitek 2 (2009 FDA) and CLSI M100S 26th Edition Breakpoints

et al. 2017

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The performances of Vitek 2 AST-GN69 and AST-XN06 cards were compared to Clinical and Laboratory Standards Institute (CLSI) reference broth microdilution (BMD) for 99 isolates of Pseudomonas aeruginosa, 26 Acinetobacter baumannii isolates, and 11 Stenotrophomonas maltophilia isolates. In total, 15 antimicrobials were evaluated, with 11 for P. aeruginosa, 14 for A. baumannii, and 2 for S. maltophilia. Categorical agreement (CA) was assessed using both Vitek 2 breakpoints and 2016 CLSI M100S 26th edition breakpoints. The essential agreement values for P. aeruginosa, A. baumannii, and S. maltophilia were 99.5%, 99.2%, and 100%, respectively. The CA values for P. aeruginosa, A. baumannii, and S. maltophilia were 94.1%, 92.7%, and 95.5%, respectively, by the Vitek 2 breakpoints, and 93.4%, 92.3%, and 95.5%, respectively, by the CLSI breakpoints. Overall, the Vitek 2 performance was comparable to that of BMD using both Vitek 2 breakpoints and 2016 CLSI M100S 26th edition breakpoints. Improved performance was noted for the reformulated piperacillin-tazobactam and imipenem found on the AST-GN69 card, with no very major or major errors noted when using the CLSI breakpoints.KEYWORDS Acinetobacter baumannii, antimicrobial susceptibility testing, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Vitek 2, breakpoints, broth microdilution M ultidrug resistance (MDR) among Gram-negative bacteria, which is defined by nonsusceptibility (intermediate or resistant) to Ն1 agent in Ն3 antimicrobial categories (1), is a significant clinical concern. In the United States, 12.6% of health care-associated infections (HAIs) caused by Pseudomonas aeruginosa are due to MDR isolates, as are 45.3% of Acinetobacter species (2). Infections caused by these MDR organisms are associated with poor clinical outcomes, particularly for patients who are immunocompromised, have prolonged hospitalization in the intensive care unit, or who reside in long-term-care facilities (3). The treatment options for MDR infections are limited, making accurate and timely antimicrobial susceptibility testing (AST) critical for patient care.Most U.S. clinical laboratories use commercial automated systems for AST, including the bioMérieux Vitek 2. However, the failure of these systems to detect resistance in Gram-negative bacteria, and in particular ␤-lactam resistance in nonfermenting Gramnegative bacilli, such as P. aeruginosa and Acinetobacter baumannii, has been reported by several studies (4-7). In 2010, bioMérieux issued a voluntary recall of AST cards

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Section: Discussioncontrasting

confidence: 55%

Performance of Vitek 2 for Antimicrobial Susceptibility Testing of Acinetobacter baumannii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia with Vitek 2 (2009 FDA) and CLSI M100S 26th Edition Breakpoints

et al. 2017

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“…The Vitek results were confirmed and concordant with disk diffusion testing. Third, a more recent analysis of Vitek 2 performance using the newer (AST-GN69) cards (the same ones our hospital uses) wherein the TZP has been reformulated, were concordant with reference methods [38]. Additionally, an increase in the MICs of cefepime, piperacillin-tazobactam, and ticarcillin-clavulanate was biologically plausible given the antibiotics the patient previously received for the urinary tract infection.…”

Section: Discussionmentioning

confidence: 66%

Pseudomonas Endocarditis with an unstable phenotype: the challenges of isolate characterization and Carbapenem stewardship with a partial review of the literature

Lesho

Snesrud

Kwak

et al. 2017

Antimicrob Resist Infect Control

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Background Pseudomonas endocarditis is exceedingly rare, especially in patients without predisposing risks. We present such a case that included unexpected switches in antibacterial resistance profiles in two Pseudomonas aeruginosa (PA) strains with the same whole-genome sequence. The case also involved diagnostic and treatment challenges, such as issues with automated testing platforms, choosing the optimal aminoglycoside, minimizing unnecessary carbapenem exposure, and the need for faster, more informative laboratory tests.Case presentationOn hospital day one (HD-1) a cefepime and piperacillin-tazobactam (FEP-TZP)-susceptible P. aeruginosa was isolated from the bloodstream of a 62-year-old man admitted for evaluation of possible endocarditis and treated with gentamicin and cefepime. On HD-2, his antibiotic regimen was changed to tobramycin and cefepime. On HD-11, he underwent aortic valve replacement, and P. aeruginosa was isolated from the explanted valve. Unexpectedly, it was FEP-TZP-resistant, so cefepime was switched to meropenem. On HD-14, in preparation for whole-genome sequencing (WGS), valve and blood isolates were removed from cryo-storage, re-cultured, and simultaneously tested with the same platforms, reagents, and inoculations previously used. Curiously, the valve isolate was now FEP-TZP-susceptible. WGS revealed that both isolates were phylogenetically identical, differing by a single nucleotide in a chemotaxis-encoding gene. They also contained the same resistance genes (bla ADC35, aph(3′)-II, bla OXA-50, catB7, fosA). ConclusionRepeated testing on alternate platforms and WGS did not definitively determine the resistance mechanism(s), which in this case, is most likely unstable de-repression of a chromosomal AmpC β-lactamase, porin alterations, or efflux upregulation, with reversion to baseline (non-efflux) transcription. Although sub-culture on specialized media to select for less fit (more resistant) colonies, followed by transcriptome analysis, and multiple sequence alignment, might have revealed the mechanism and better informed the optimal choice of β-lactam, such approaches are neither rapid, nor feasible for hospital laboratories. In this era of escalating drug resistance and dwindling antibiotics, use of the most potent anti-pseudomonals must be balanced with stewardship. Clinicians need access to validated genomic correlates of resistance, and faster, more informative diagnostics. Therefore, we placed these isolates and their sequences in the public domain for inclusion in the Pseudomonas pan-genome and database projects for further countermeasure development.

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“…VITEK 2 system showed a high level of minor errors (a tendency toward false sensitivity) particularly to ceftazidime and cefepime. In general, E-test showed a high rate of false-resistant results to all antibiotics among the tested methods, while the disk diffusion method showed a high rate of falsesusceptible results to all antibiotics except ceftazidime (10). broth microdilution method, which showed that only 11 isolates were moderately resistant or resistant to imipenem and meropenem.…”

Section: Resultsmentioning

confidence: 92%

Comparison of Disc Diffusion, Broth Microdilution and Modified Hodge Test Susceptibility Testing Of Escherichia coli Isolates to Beta-Lactam Antibiotics

Alizade¹,

Fallah²,

Ghanbarpour³

et al. 2016

mljgoums

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Background and Objective: One of the main tasks of clinical microbiology laboratories is to determine antibiotic resistance profiles in common pathogens and ensure the selection of effective antibiotics for certain infections. The aim of this study was to compare the methods of disk diffusion, broth microdilution and modified Hodge test in Escherichia coli isolates from urinary tract infection and diarrhea for susceptibility testing against beta-lactam antibiotics in Kerman, Iran.Methods: In this study, 432 E. coli isolates were collected from diarrhea (216 isolates) and urinary tract infection samples (216 isolates). The antibiotic susceptibility testing methods of disk diffusion, broth microdilution and modified Hodge test were performed according to the Clinical and Laboratory Standards Institute guidelines.Results: The findings of disk diffusion method showed that resistance to cefotaxime, ceftazidime, aztreonam, cefepime and imipenem was 51.15%, 30.55%, 24.30%, 15.27% and 1.85%, respectively. In the disk diffusion test, 51.15% of the isolates were resistant to at least one antibiotic, all of which were later evaluated by the broth microdilution method. Moreover, 52.94%, 17.19%, 13.12% and 0.90% of the isolates were resistant to cefotaxime, ceftazidime, cefepime and imipenem, respectively. All of the isolates were evaluated for the production of carbapenemase enzyme by the modified Hodge test and none of the isolates were found as positive.Conclusion: This study shows that performing carbapenem tests is very challenging, and laboratories are recommended to use secondary and independent antibiotic susceptibility tests such as modified Hodge test to confirm the carbapenem-resistant results.

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Comparison of different methods of determining β-lactam susceptibility in clinical strains of Pseudomonas aeruginosa

Cited by 16 publications

References 20 publications

Performance of Vitek 2 for Antimicrobial Susceptibility Testing of Acinetobacter baumannii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia with Vitek 2 (2009 FDA) and CLSI M100S 26th Edition Breakpoints

Performance of Vitek 2 for Antimicrobial Susceptibility Testing of Acinetobacter baumannii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia with Vitek 2 (2009 FDA) and CLSI M100S 26th Edition Breakpoints

Pseudomonas Endocarditis with an unstable phenotype: the challenges of isolate characterization and Carbapenem stewardship with a partial review of the literature

Comparison of Disc Diffusion, Broth Microdilution and Modified Hodge Test Susceptibility Testing Of Escherichia coli Isolates to Beta-Lactam Antibiotics

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