Comparison of 3 Etest® methods and time-kill assay for determination of antimicrobial synergy against carbapenemase-producing Klebsiella species

Pankey, George A.; Ashcraft, Deborah; Dornelles, Adriana

doi:10.1016/j.diagmicrobio.2013.07.006

Cited by 46 publications

(51 citation statements)

References 33 publications

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“…A factor that prompted this investigation was the comparable results of the Etest synergy method and TKA for testing antibacterial combinations, with the Etest method being simpler to perform (14,22). This study demonstrated the presence of synergy of the combination of polymyxin B and fluconazole against C. glabrata isolates-even using a lower, subinhibitory concentration of polymyxin B (1/2 MIC).…”

Section: Discussionmentioning

confidence: 91%

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Time-Kill Assay and Etest Evaluation for Synergy with Polymyxin B and Fluconazole against Candida glabrata

Pankey

Ashcraft

Kahn

et al. 2014

Antimicrob Agents Chemother

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Fluconazole-resistant Candida glabrata is an emerging pathogen that causes fungemia. Polymyxin B, a last-resort antibiotic used to treat multidrug-resistant Gram-negative bacterial infections, has been found to possess in vitro fungicidal activity and showed synergy with fluconazole against a single strain of C. glabrata. Since both agents may be used simultaneously in intensive care unit (ICU) patients, this study was performed to test for possible synergy of this combination against 35 C. glabrata blood isolates, using 2 methods: a time-kill assay and an experimental MIC-MIC Etest method. Thirty-five genetically unique C. glabrata bloodstream isolates were collected from 2009 to 2011, identified using an API 20C system, and genotyped by repetitive sequence-based PCR (rep-PCR). MICs were determined by Etest and broth microdilution methods. Synergy testing was performed using a modified bacterial Etest synergy method and time-kill assay, with final results read at 24 h. The Etest method showed synergy against 19/35 (54%) isolates; the time-kill assay showed synergy against 21/35 (60%) isolates. Isolates not showing drug synergy had an indifferent status. Concordance between methods was 60%. In vitro synergy of polymyxin B and fluconazole against the majority of C. glabrata isolates was demonstrated by both methods. The bacterial Etest synergy method adapted well when used with C. glabrata. Etest was easier to perform than time-kill assay and may be found to be an acceptable alternative to time-kill assay with antifungals. Candida glabrata has been a rising cause of candidemia in the past few years, second only to Candida albicans (1). According to the Centers for Disease Control and Prevention (CDC), candidemia is the fourth most common hospital-acquired infection in the United States (2). C. glabrata has been known to develop resistance to the azole family of antifungals, the most inexpensive and easily accessible medications to treat candidemia. Further data from the CDC have shown that 7% of Candida species have become fluconazole resistant (2). This development of resistance is most likely due to the routine use of azoles in treatment or prophylaxis. Other treatment options for Candida infections include amphotericin B and the echinocandin family (to which resistance by C. glabrata has occurred) (1). A U.S. surveillance study evaluating Candida isolates from San Francisco, CA, Atlanta, GA, Baltimore, MD, and Connecticut (from 1998 to 2010) determined that C. glabrata isolates are able to adapt to new environments to increase their fitness and antifungal resistance (3). Another surveillance study, evaluating developing resistance in fluconazolesusceptible isolates collected from 2008 to 2011, showed that among 2,329 Candida isolates, the prevalence of azole resistance was unchanged (7%), 32 of the isolates were echinocandin resistant, and 8 C. glabrata isolates were resistant to both fluconazole and echinocandins (4).Polymyxin B is a last-resort antibiotic used to treat multidrug-resistant Gram-negative bacte...

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Section: Discussionmentioning

confidence: 91%

“…A modified Etest synergy method (14) previously reported for testing antibacterial combinations was performed in triplicate to test combinations for antifungal activity ( Fig. 1 and 2).…”

Section: Synergy Testing (I) Etest Synergy Methodmentioning

confidence: 99%

Time-Kill Assay and Etest Evaluation for Synergy with Polymyxin B and Fluconazole against Candida glabrata

Pankey

Ashcraft

Kahn

et al. 2014

Antimicrob Agents Chemother

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“…Several methods have been assessed to evaluate the synergistic activity of two or more antimicrobial agents [5,6,[15][16][17][18]. As the gold standard, the TK method yields high concordance between various studies because it produces dynamic and longitudinal information about bacterial death, which is not provided by other methods.…”

Section: Discussionmentioning

confidence: 99%

“…Existing methods have several disadvantages including the time-kill assay (TK), which-although considered the gold standard for synergism evaluation-is very timeconsuming and requires high technical skills [5,6]. The disk and epsilometer tape diffusion methods using commercially available materials are less technically demanding than the TK assay but require further validation.…”

mentioning

confidence: 99%

Comparison of methods for the detection of in vitro synergy in multidrug-resistant gram-negative bacteria

et al. 2020

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Background: The use of combined antibiotic therapy has become an option for infections caused by multidrugresistant (MDR) bacteria. The time-kill (TK) assay is considered the gold standard method for the evaluation of in vitro synergy, but it is a time-consuming and expensive method. The purpose of this study was to evaluate two methods for testing in vitro antimicrobial combinations: the disk diffusion method through disk approximation (DA) and the agar gradient diffusion method via the MIC:MIC ratio. The TK assay was included as the gold standard. MDR Gram-negative clinical isolates (n = 62; 28 Pseudomonas aeruginosa, 20 Acinetobacter baumannii, and 14 Serratia marcescens) were submitted to TK, DA, and MIC:MIC ratio synergy methods. Results: Overall, the agreement between the DA and TK assays ranged from 20 to 93%. The isolates of A. baumannii showed variable results of synergism according to TK, and the calculated agreement was statistically significant in this species against fosfomycin with meropenem including colistin-resistant isolates. The MIC:MIC ratiometric agreed from 35 to 71% with TK assays. The kappa test showed good agreement for the combination of colistin with amikacin (K = 0.58; P = 0.04) among the colistin-resistant A. baumannii isolates. Conclusions: The DA and MIC:MIC ratiometric methods are easier to perform and might be a more viable tool for clinical microbiology laboratories.

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“…Bacteria were cultivated on blood agar plates in 5 % CO 2 at 37 0 C. Minimal inhibitory concentration (MIC) was determined using Etests (Biomerieux, Solna, Sweden) on Müller-Hinton agar (MHA) with defibrinated horse blood and β-NAD [24] or blood agar for three isolates not growing on the MHA. For synergy testing based on Etest methodology, the method MIC:MIC was used [25].…”

Section: Collection Of and Analysis Of Isolatesmentioning

confidence: 99%

Clinical and microbiological features of infective endocarditis caused by aerococci

et al. 2015

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Aerococci are increasingly recognized as causative agents in human infective endocarditis (IE). Information on the clinical presentation and the prognosis of IE caused by aerococci is limited. We employed the Swedish Registry of Infective Endocarditis (SRIE) to identify cases of aerococcal IE. The medical records were analysed and comparisons with cases of IE caused by other pathogens reported to the SRIE were made. Available bacterial isolates were reanalysed using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) and the aetiology was confirmed to be Aerococcus urinae in fourteen cases and Aerococcus sanguinicola in two cases. The bacteria were sensitive to penicillin and Etest-based synergy testing and time-kill experiments suggested synergy between penicillin and gentamicin towards some isolates. The patients had a median age of 79 years, which was significantly higher than that of patients with IE caused by streptococci or Staphylococcus aureus. Most patients with IE caused by aerococci had underlying urinary tract diseases and many presented with symptoms suggesting a urinary tract focus of the infection. Despite the fact that many patients with aerococcal IE presented with severe sepsis, ICU treatment was needed only in one patient and there was no fatality. Valve exchange surgery was needed in four of sixteen patients with aerococcal IE and embolization was seen in three patients. This report is by far the largest on aerococcal IE and suggests that the prognosis of aerococcal IE is relatively favourable despite the fact that the patients are old and have significant comorbidities.

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Comparison of 3 Etest® methods and time-kill assay for determination of antimicrobial synergy against carbapenemase-producing Klebsiella species

Cited by 46 publications

References 33 publications

Time-Kill Assay and Etest Evaluation for Synergy with Polymyxin B and Fluconazole against Candida glabrata

Time-Kill Assay and Etest Evaluation for Synergy with Polymyxin B and Fluconazole against Candida glabrata

Comparison of methods for the detection of in vitro synergy in multidrug-resistant gram-negative bacteria

Clinical and microbiological features of infective endocarditis caused by aerococci

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