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Braspenning AJMM, Rajakani SG, Sey A, El Bounja M, Lammens C, Glupczynski Y, Malhotra-Kumar S. Assessment of Colistin Heteroresistance among Multidrug-Resistant Klebsiella pneumoniae Isolated from Intensive Care Patients in Europe. Antibiotics (Basel) 2024; 13:281. [PMID: 38534716 DOI: 10.3390/antibiotics13030281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 03/15/2024] [Accepted: 03/18/2024] [Indexed: 03/28/2024] Open
Abstract
Heteroresistance (HR) to colistin is especially concerning in settings where multi-drug-resistant (MDR) K. pneumoniae are prevalent and empiric use of colistin might lead to treatment failures. This study aimed to assess the frequency of occurrence of colistin HR (CHR) among (MDR) K. pneumoniae (n = 676) isolated from patients hospitalized in 13 intensive care units (ICUs) in six European countries in a clinical trial assessing the impact of decolonization strategies. All isolates were whole-genome-sequenced and studied for in vitro colistin susceptibility. The majority were colistin-susceptible (CS) (n = 597, MIC ≤ 2 µg/mL), and 79 were fully colistin-resistant (CR) (MIC > 2 µg/mL). A total of 288 CS isolates were randomly selected for population analysis profiling (PAP) to assess CHR prevalence. CHR was detected in 108/288 CS K. pneumoniae. No significant association was found between the occurrence of CHR and country, MIC-value, K-antigen type, and O-antigen type. Overall, 92% (617/671) of the K. pneumoniae were MDR with high prevalence among CS (91%, 539/592) and CR (98.7%, 78/79) isolates. In contrast, the proportion of carbapenemase-producing K. pneumoniae (CP-Kpn) was higher among CR (72.2%, 57/79) than CS isolates (29.3%, 174/594). The proportions of MDR and CP-Kpn were similar among CHR (MDR: 85%, 91/107; CP-Kpn: 29.9%, 32/107) and selected CS isolates (MDR: 84.7%, 244/288; CP-Kpn: 28.1%, 80/285). WGS analysis of PAP isolates showed diverse insertion elements in mgrB or even among technical replicates underscoring the stochasticity of the CHR phenotype. CHR isolates showed high sequence type (ST) diversity (Simpson's diversity index, SDI: 0.97, in 52 of the 85 STs tested). CR (SDI: 0.85) isolates were highly associated with specific STs (ST101, ST147, ST258/ST512, p ≤ 0.003). The widespread nature of CHR among MDR K. pneumoniae in our study urge the development of rapid HR detection methods to inform on the need for combination regimens.
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Affiliation(s)
- Anouk J M M Braspenning
- Laboratory of Medical Microbiology, Vaccine & Infectious Disease Institute, Universiteit Antwerpen, 2610 Antwerp, Belgium
| | - Sahaya Glingston Rajakani
- Laboratory of Medical Microbiology, Vaccine & Infectious Disease Institute, Universiteit Antwerpen, 2610 Antwerp, Belgium
| | - Adwoa Sey
- Laboratory of Medical Microbiology, Vaccine & Infectious Disease Institute, Universiteit Antwerpen, 2610 Antwerp, Belgium
| | - Mariem El Bounja
- Laboratory of Medical Microbiology, Vaccine & Infectious Disease Institute, Universiteit Antwerpen, 2610 Antwerp, Belgium
| | - Christine Lammens
- Laboratory of Medical Microbiology, Vaccine & Infectious Disease Institute, Universiteit Antwerpen, 2610 Antwerp, Belgium
| | - Youri Glupczynski
- Laboratory of Medical Microbiology, Vaccine & Infectious Disease Institute, Universiteit Antwerpen, 2610 Antwerp, Belgium
| | - Surbhi Malhotra-Kumar
- Laboratory of Medical Microbiology, Vaccine & Infectious Disease Institute, Universiteit Antwerpen, 2610 Antwerp, Belgium
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Liu S, Wu Y, Qi S, Shao H, Feng M, Xing L, Liu H, Gao Y, Zhu Z, Zhang S, Du Y, Lu Y, Yang J, Chen P, Sun T. Polymyxin B therapy based on therapeutic drug monitoring in carbapenem-resistant organisms sepsis: the PMB-CROS randomized clinical trial. Crit Care 2023; 27:232. [PMID: 37312218 PMCID: PMC10262552 DOI: 10.1186/s13054-023-04522-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Accepted: 06/04/2023] [Indexed: 06/15/2023] Open
Abstract
BACKGROUND The appropriate administration regimen of polymyxin B is yet controversial. The present study aimed to explore the optimal dose of polymyxin B under therapeutic drug monitoring (TDM) guidance. METHODS In China's Henan province, 26 hospitals participated in a randomized controlled trial. We included patients with sepsis caused by carbapenem-resistant Gram-negative bacteria (CR-GNB) susceptible to polymyxin B. The patients were randomly divided into a high-dose (HD) group or a low-dose (LD) group and received 150 mg loading dose, 75 mg every 12 h and 100 mg loading dose, 50 mg every 12 h, respectively. TDM was employed to determine if the dose of polymyxin B needs adjustment based on the area under the concentration-time curve across 24 h at a steady state (ssAUC0-24) of 50-100 mg h/L. The primary outcome was the 14-day clinical response, and the secondary outcomes included 28- and 14-day mortality. RESULTS This trial included 311 patients, with 152 assigned to the HD group and 159 assigned to the LD group. Intention-to-treat analysis showed that the 14-day clinical response was non-significant (p = 0.527): 95/152 (62.5%) in the HD group and 95/159 (59.7%) in the LD group. Kaplan-Meier's 180-day survival curve showed survival advantage in the HD group than in the LD group (p = 0.037). More patients achieved the target ssAUC0-24 in the HD than in the LD group (63.8% vs. 38.9%; p = 0.005) and in the septic shock subgroup compared to all subjects (HD group: 71.4% vs. 63.8%, p = 0.037; LD group: 58.3% vs. 38.9%, p = 0.0005). Also, the target AUC compliance was not correlated with clinical outcomes but with acute kidney injury (AKI) (p = 0.019). Adverse events did not differ between the HD and LD groups. CONCLUSION A fixed polymyxin B loading dose of 150 mg and a maintenance dose of 75 mg every 12 h was safe for patients with sepsis caused by CR-GNB and improves long-term survival. The increased AUC was associated with increased incidence of AKI, and TDM results were valued to prevent AKI. Trial registration Trial registration ClinicalTrials.gov: ChiCTR2100043208, Registration date: January 26, 2021.
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Affiliation(s)
- Shaohua Liu
- Department of General ICU, The First Affiliated Hospital of Zhengzhou University, Henan Key Laboratory of Critical Care Medicine, Zhengzhou Key Laboratory of Sepsis, Henan Engineering Research Center for Critical Care Medicine, Zhengzhou, 450052, People's Republic of China
| | - Ying Wu
- Department of Biostatistics, School of Public Health, Southern Medical University, Guangzhou, 510515, People's Republic of China
| | - Shaoyan Qi
- Department of ICU, The Second Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, People's Republic of China
| | - Huanzhang Shao
- Department of ICU, Henan Provincial People's Hospital, Zhengzhou, 450052, People's Republic of China
| | - Min Feng
- Department of Surgery ICU, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, People's Republic of China
| | - Lihua Xing
- Department of Respiratory ICU, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, People's Republic of China
| | - Hongmei Liu
- Department of Respiratory ICU, Henan Provincial People's Hospital, Zhengzhou, 450052, People's Republic of China
| | - Yanqiu Gao
- Department of Respiratory ICU, Zhengzhou Central Hospital, Zhengzhou, 450052, People's Republic of China
| | - Zhiqiang Zhu
- Department of Emergency ICU, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, People's Republic of China
| | - Shuguang Zhang
- Department of General ICU, The First Affiliated Hospital of Zhengzhou University, Henan Key Laboratory of Critical Care Medicine, Zhengzhou Key Laboratory of Sepsis, Henan Engineering Research Center for Critical Care Medicine, Zhengzhou, 450052, People's Republic of China
| | - Yuming Du
- Department of Surgery ICU, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, People's Republic of China
| | - Yibin Lu
- Department of ICU, Xinyang Central Hospital, Xinyang, 464000, People's Republic of China
| | - Jing Yang
- Department of Pharmacy, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, People's Republic of China
| | - Pingyan Chen
- Department of Biostatistics, School of Public Health, Southern Medical University, Guangzhou, 510515, People's Republic of China
| | - Tongwen Sun
- Department of General ICU, The First Affiliated Hospital of Zhengzhou University, Henan Key Laboratory of Critical Care Medicine, Zhengzhou Key Laboratory of Sepsis, Henan Engineering Research Center for Critical Care Medicine, Zhengzhou, 450052, People's Republic of China.
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Zhang HL, Han JH, Lapp Z, Snitkin E, Goldstein EJC, Muldoon S, Tolomeo P, Lautenbach E. Risk Factors for Colistin-Resistant Carbapenem-Resistant Klebsiella pneumoniae in the Postacute Care Setting. Open Forum Infect Dis 2022; 9:ofac452. [PMID: 36168553 PMCID: PMC9511120 DOI: 10.1093/ofid/ofac452] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 08/30/2022] [Indexed: 12/01/2022] Open
Abstract
We assessed risk factors for colistin resistance among carbapenem-resistant Klebsiella pneumoniae (CRKP) from 375 patients in long-term acute care hospitals. Recent colistin or polymyxin B exposure was associated with increased odds of colistin resistance (adjusted odds ratio = 1.11 per day of exposure, 95% confidence interval = 1.03-1.19, P = .007).
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Affiliation(s)
- Helen L Zhang
- Correspondence: Helen L. Zhang, MD, MSCE, Division of Infectious Diseases, University of Pennsylvania Perelman School of Medicine, 3400 Spruce Street, Philadelphia, PA 19104 ()
| | - Jennifer H Han
- Division of Infectious Diseases, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA,Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA,Department of Biostatistics, Epidemiology and Informatics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
| | - Zena Lapp
- Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Evan Snitkin
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Ellie J C Goldstein
- R.M. Alden Research Laboratory, Santa Monica, California, USA,Department of Medicine, David Geffen School of Medicine at the University of California, Los Angeles, California, USA
| | | | - Pam Tolomeo
- Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA,Department of Biostatistics, Epidemiology and Informatics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
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Manual Reading of Sensititre Broth Microdilution System Panels Improves Accuracy of Susceptibility Reporting for Polymyxin Antibiotics. J Clin Microbiol 2021; 59:e0033221. [PMID: 34165324 DOI: 10.1128/jcm.00332-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Accurate and reproducible antimicrobial susceptibility testing (AST) of polymyxin antibiotics is critical, as these drugs are last-line therapeutic options for the treatment of multidrug-resistant Gram-negative bacterial infections. However, polymyxin AST in the routine laboratory remains challenging. In this study, we evaluated the performance of an automated broth microdilution (BMD) system (Sensititre, ThermoFisher) compared to that of agar dilution (AD) for colistin and polymyxin B AST of 129 Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii complex clinical isolates. MICs derived from the Sensititre instrument based on two operator comparisons demonstrated overall categorical agreement (CA) of 86% and 89% compared to AD for colistin and 89% and 92% compared to AD for polymyxin B. However, error rates were higher than recommended by CLSI. Manual inspection of microdilution wells revealed microbial growth and skip wells which were erroneously interpreted by the Aris 2X instrument. Using manually interpreted BMD MICs read by two operators increased the overall categorical agreements to 88% and 95% compared to AD for colistin and 92% and 96% compared to AD for polymyxin B. Laboratories choosing to use the Sensititre platform for polymyxin AST should consider manual evaluation of wells as part of their algorithm.
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Wang X, Chaney WE, Pavlidis HO, McGinnis JP, Byrd JA, Farnell YZ, Johnson TJ, McElroy AP, Farnell MB. Determination of Antimicrobial Resistance Patterns in Salmonella from Commercial Poultry as Influenced by Microbiological Culture and Antimicrobial Susceptibility Testing Methods. Microorganisms 2021; 9:microorganisms9061319. [PMID: 34204397 PMCID: PMC8235701 DOI: 10.3390/microorganisms9061319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 06/06/2021] [Accepted: 06/12/2021] [Indexed: 11/16/2022] Open
Abstract
Monitoring antimicrobial resistance of foodborne pathogens in poultry is critical for food safety. We aimed to compare antimicrobial resistance phenotypes in Salmonella isolated from poultry samples as influenced by isolation and antimicrobial susceptibility testing methods. Salmonella isolates were cultured from a convenience sample of commercial broiler ceca with and without selective broth enrichment, and resistance phenotypes were determined for 14 antimicrobials using the Sensititre® platform and a qualitative broth breakpoint assay. The broth breakpoint method reported higher resistance to chloramphenicol, sulfisoxazole, and the combination of trimethoprim and sulfamethoxazole, and lower resistance to streptomycin as compared to the Sensititre® assay in trial one. Selective enrichment of samples containing Salmonella in Rappaport-Vassiliadis broth reported lowered detectable resistance to amoxicillin/clavulanic acid, ampicillin, azithromycin, cefoxitin, ceftriaxone, nalidixic acid, and meropenem, and increased resistance to streptomycin and tetracycline than direct-plating samples in trial one. Using matched isolates in trial two, the Sensititre® assay reported higher resistance to chloramphenicol and gentamicin, and lower resistance to nalidixic acid as compared to the broth breakpoint method. These results suggest methodology is a critical consideration in the detection and surveillance of antimicrobial resistance phenotypes in Salmonella isolates from poultry samples and could affect the accuracy of population or industry surveillance insights and intervention strategies.
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Affiliation(s)
- Xi Wang
- Department of Poultry Science, Texas A&M AgriLife Research, College Station, TX 77843, USA; (X.W.); (Y.Z.F.); (A.P.M.)
| | - W. Evan Chaney
- Diamond V, Cedar Rapids, IA 52404, USA; (W.E.C.); (H.O.P.); (J.P.M.); (J.A.B.); (T.J.J.)
| | - Hilary O. Pavlidis
- Diamond V, Cedar Rapids, IA 52404, USA; (W.E.C.); (H.O.P.); (J.P.M.); (J.A.B.); (T.J.J.)
| | - James P. McGinnis
- Diamond V, Cedar Rapids, IA 52404, USA; (W.E.C.); (H.O.P.); (J.P.M.); (J.A.B.); (T.J.J.)
| | - J. Allen Byrd
- Diamond V, Cedar Rapids, IA 52404, USA; (W.E.C.); (H.O.P.); (J.P.M.); (J.A.B.); (T.J.J.)
| | - Yuhua Z. Farnell
- Department of Poultry Science, Texas A&M AgriLife Research, College Station, TX 77843, USA; (X.W.); (Y.Z.F.); (A.P.M.)
| | - Timothy J. Johnson
- Diamond V, Cedar Rapids, IA 52404, USA; (W.E.C.); (H.O.P.); (J.P.M.); (J.A.B.); (T.J.J.)
| | - Audrey P. McElroy
- Department of Poultry Science, Texas A&M AgriLife Research, College Station, TX 77843, USA; (X.W.); (Y.Z.F.); (A.P.M.)
| | - Morgan B. Farnell
- Department of Poultry Science, Texas A&M AgriLife Research, College Station, TX 77843, USA; (X.W.); (Y.Z.F.); (A.P.M.)
- Correspondence:
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Kaprou GD, Bergšpica I, Alexa EA, Alvarez-Ordóñez A, Prieto M. Rapid Methods for Antimicrobial Resistance Diagnostics. Antibiotics (Basel) 2021; 10:209. [PMID: 33672677 PMCID: PMC7924329 DOI: 10.3390/antibiotics10020209] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 02/09/2021] [Accepted: 02/13/2021] [Indexed: 02/06/2023] Open
Abstract
Antimicrobial resistance (AMR) is one of the most challenging threats in public health; thus, there is a growing demand for methods and technologies that enable rapid antimicrobial susceptibility testing (AST). The conventional methods and technologies addressing AMR diagnostics and AST employed in clinical microbiology are tedious, with high turnaround times (TAT), and are usually expensive. As a result, empirical antimicrobial therapies are prescribed leading to AMR spread, which in turn causes higher mortality rates and increased healthcare costs. This review describes the developments in current cutting-edge methods and technologies, organized by key enabling research domains, towards fighting the looming AMR menace by employing recent advances in AMR diagnostic tools. First, we summarize the conventional methods addressing AMR detection, surveillance, and AST. Thereafter, we examine more recent non-conventional methods and the advancements in each field, including whole genome sequencing (WGS), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) spectrometry, Fourier transform infrared (FTIR) spectroscopy, and microfluidics technology. Following, we provide examples of commercially available diagnostic platforms for AST. Finally, perspectives on the implementation of emerging concepts towards developing paradigm-changing technologies and methodologies for AMR diagnostics are discussed.
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Affiliation(s)
- Georgia D. Kaprou
- Department of Food Hygiene and Technology, University of León, 24071 León, Spain; (I.B.); (E.A.A.); (A.A.-O.); (M.P.)
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, L-4367 Belvaux, Luxembourg
| | - Ieva Bergšpica
- Department of Food Hygiene and Technology, University of León, 24071 León, Spain; (I.B.); (E.A.A.); (A.A.-O.); (M.P.)
- Institute of Food Safety, Animal Health and Environment BIOR, LV-1076 Riga, Latvia
| | - Elena A. Alexa
- Department of Food Hygiene and Technology, University of León, 24071 León, Spain; (I.B.); (E.A.A.); (A.A.-O.); (M.P.)
| | - Avelino Alvarez-Ordóñez
- Department of Food Hygiene and Technology, University of León, 24071 León, Spain; (I.B.); (E.A.A.); (A.A.-O.); (M.P.)
- Institute of Food Science and Technology, University of León, 24071 León, Spain
| | - Miguel Prieto
- Department of Food Hygiene and Technology, University of León, 24071 León, Spain; (I.B.); (E.A.A.); (A.A.-O.); (M.P.)
- Institute of Food Science and Technology, University of León, 24071 León, Spain
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Evaluation of the MicroScan Colistin Well and Gradient Diffusion Strips for Colistin Susceptibility Testing in Enterobacteriaceae. J Clin Microbiol 2019; 57:JCM.01866-18. [PMID: 30814260 DOI: 10.1128/jcm.01866-18] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Accepted: 02/24/2019] [Indexed: 01/25/2023] Open
Abstract
Many laboratories are unable to perform colistin susceptibility testing. Diffusion-based antimicrobial susceptibility testing methods are not recommended, and not all laboratories have the capacity to perform broth microdilution (BMD). Using a multistep tiered approach, we investigated whether the adapted use of the MicroScan colistin well (4 μg/ml) could enhance laboratory capacity for the detection and subsequent molecular characterization of colistin-resistant Enterobacteriaceae For the MicroScan colistin well, categorical agreement with BMD was 92.7%, and the very major error rate was 10.7%. For gradient diffusion strips, the categorical agreement was 86.4%, and the very major error rate was 53.6%. The MicroScan colistin well detected all isolates carrying mcr-1 or mcr-2 genes (n = 16), but gradient diffusion strips identified an MIC of ≥4 for colistin for only 62.5% of these isolates. A 6-month prospective phenotypic and genotypic study performed at a single clinical microbiology laboratory assessed isolates growing in the MicroScan colistin well for concordance. While 37 of 39 isolates growing in the MicroScan colistin well displayed a colistin MIC of ≥4 by BMD, all were determined to be negative for the mcr-1 and mcr-2 genes by PCR. A retrospective review of all Escherichia coli, Klebsiella spp., and Enterobacter spp. tested by MicroScan at this laboratory in 2016 identified 260 of 7,894 (3.3%) isolates that grew in the MicroScan colistin well. Based on the data presented, clinical and public health laboratories could use the MicroScan colistin well as a first screen for the detection of isolates displaying elevated colistin MICs, which could then undergo further characterization.
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Antimicrobial Susceptibility Testing for Polymyxins: Challenges, Issues, and Recommendations. J Clin Microbiol 2019; 57:JCM.01390-18. [PMID: 30541939 DOI: 10.1128/jcm.01390-18] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Polymyxins, including polymyxin B and polymyxin E (colistin), are now increasingly being used worldwide to treat patients with multidrug-resistant (MDR) Gram-negative bacterial infections. This necessitates that laboratories employ an accurate and reliable method for the routine performance of polymyxin susceptibility testing. A number of reasons have accounted for the difficulties with susceptibility testing for the polymyxins, including their multicomponent composition, poor diffusion in the agar medium, adsorption to microtiter plates, the lack of a reliable susceptibility test, the lack of a specific breakpoint from professional organizations, the synergistic effect of polysorbate 80, and the development of heteroresistance. This minireview discusses such problems that impact the results of currently available susceptibility testing methods. We also provide emerging concepts on mechanisms of polymyxin resistance, including chromosomally and plasmid-mediated mcr-related resistance. Broad-range investigations on such critical issues in relation to polymyxins can be beneficial for the implementation of effective treatment against MDR Gram-negative bacterial infections.
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Effects of Microplate Type and Broth Additives on Microdilution MIC Susceptibility Assays. Antimicrob Agents Chemother 2018; 63:AAC.01760-18. [PMID: 30397070 PMCID: PMC6325200 DOI: 10.1128/aac.01760-18] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 10/27/2018] [Indexed: 11/20/2022] Open
Abstract
The determination of antibiotic potency against bacterial strains by assessment of their minimum inhibitory concentration normally uses a standardized broth microdilution assay procedure developed more than 50 years ago. However, certain antibiotics require modified assay conditions in order to observe optimal activity. The determination of antibiotic potency against bacterial strains by assessment of their minimum inhibitory concentration normally uses a standardized broth microdilution assay procedure developed more than 50 years ago. However, certain antibiotics require modified assay conditions in order to observe optimal activity. For example, daptomycin requires medium supplemented with Ca2+, and the lipoglycopeptides dalbavancin and oritavancin require Tween 80 to be added to the growth medium to prevent the depletion of free drug via adsorption to the plastic microplate. In this report, we examine systematically the effects of several different plate types on microdilution broth MIC values for a set of antibiotics against Gram-positive and Gram-negative bacteria, both in medium alone and in medium supplemented with the commonly used additives Tween 80, lysed horse blood, and 50% human serum. We observed very significant differences in measured MICs (up to 100-fold) for some lipophilic antibiotics, such as the Gram-positive lipoglycopeptide dalbavancin and the Gram-negative lipopeptide polymyxins, and found that nonspecific binding plates can replace the need for surfactant additives. Microtiter plate types and any additives should be specified when reporting broth dilution MIC values, as results can vary dramatically for some classes of antibiotics.
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