Analysis of a single reference strain for determination of gentamicin regression line constants and inhibition zone diameter breakpoints in quality control of disk diffusion antibiotic susceptibility testing.

Abstract Background Detection of ceftazidime/avibactam (CAZ/AVI) antibacterial activity is absolutely vital with the rapid growth of carbapenem resistant Enterobacteriaceae (CRE). But now, there is no available automated antimicrobial susceptibility testing card for CAZ/AVI, so Kirby-Bauer has become an economical and practical method for detecting CAZ/AVI antibacterial activity against Enterobacteriaceae. Result In this study, antimicrobial susceptibility testing of CAZ/AVI against 386 Enterobacteriaceae (188 Klebsiella pneumoniae, 122 Escherichia coli, 76 Enterobacter cloacae) isolated from clinical patients was performed by broth microdilution. Of the 386 strains, 54 extended spectrum β lactamases negative (ESBL(−)), 104 extended spectrum β lactamases positive (ESBL(+)), 228 CRE. 287 isolates were susceptible to CAZ/AVI and 99 isolates were resistant to CAZ/AVI. At the same time, to obtain optimal content avibactam (AVI) disk containing ceftazidime (30 μg), inhibition zone diameter of four kinds of ceftazidime (30 μg) disk containing different AVI content (0 μg, 10 μg, 25 μg, 50 μg) were tested by Kirby-Bauer method. The microdilution broth method interpretation was used as the standard to estimate susceptible or resistance and then coherence analysis was carried out between Kirby-Bauer and broth microdilution. The result shows the inhibition zone diameter of 30 μg/50 μg disk, susceptible isolates: 20.5 mm–31.5 mm, resistance isolates: 8.25 mm–21.5 mm. The inhibition zone diameter of 30 μg/25 μg disk, susceptible isolates: 19.7 mm–31.3 mm, resistance isolates: 6.5 mm–19.2 mm. The inhibition zone diameter of 30 μg/10 μg disk, susceptible isolates: 19.5 mm–31 mm, resistance isolates: 6.5 mm–11 mm. The inhibition zone diameter of ceftazidime (30 μg), susceptible isolates: 6.5 mm–27.5 mm, resistance isolates 6.5 mm. Conclusion Our results show that 30 μg/50 μg, 30 μg/25 μg, 30 μg/10 μg CAZ/AVI disk have significant statistical differences to determinate CAZ/AVI antibacterial activity, but for 30 μg/50 μg disk, there has a cross section between susceptible isolates (minimum 20.5 mm) and resistance isolates (maximum 21.5 mm). For 30 μg/25 μg disk, it is hard to distinguish the difference between susceptible isolates (minimum 19.7 mm) and resistance isolates (maximum 19.2 mm), so 30 μg/10 μg CAZ/AVI disk is more conducive to determinate antibacterial activity.

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Antibiotic determination of antibiotic susceptibility testing disks using liquid chromatography and microbiological assay

The International Arabic Journal of Antimicrobial Agents ◽

10.3823/818 ◽

2018 ◽

Vol 8 (1) ◽

Author(s):

Amine Ousaid ◽

Jaouad Akrim ◽

Youssef Khayati

Keyword(s):

Quality Control ◽

High Performance Liquid Chromatography ◽

Liquid Chromatography ◽

Clavulanic Acid ◽

Antibiotic Susceptibility ◽

High Performance ◽

Susceptibility Testing ◽

Antibiotic Susceptibility Testing ◽

Microbiological Method ◽

Amoxicillin Clavulanic Acid

Introduction: The aim of this work was to control the quality of some antibiotics cartridges (ampicillin, amoxicillin-clavulanic acid, ciprofloxacin and vancomycin) used for antibiotic susceptibility testing by disk diffusion method. Antibiotics were determined in disks and two techniques were compared for this purpose, chromatographic and microbiological method. Methods: Chromatographic method (High-Performance Liquid Chromatography: HPLC) was used for determining ampicillin, amoxicillin-clavulanic acid and ciprofloxacin, and microbiological method for vancomycin and ampicillin. We used the European Pharmacopoeia 8th edition monographs and a simple and adapted method published in 2015 by Ramli Y. et Al. Results: Dosage results reveal that 35% of unexpired cartridges had low content and all the expired AB’s disks gave low results. Conclusion: Our study demonstrated that the content of antibiotics in disks could decrease if the storage and transport conditions (temperature and relative humidity) of disk cartridges were not respected. Therefore, properly performed quality control of antibiotic disks before use in laboratories would aid in providing accurate and reproducible results of dosage. Keywords: Antibiotic disks, Quality control, Antibiogram, High Performance Liquid Chromatography, Microbiological method.

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Categorization of temocillin susceptibility using the disc diffusion method: Susceptible, Intermediate, Resistant or Undetermined?

10.21203/rs.2.21085/v1 ◽

2020 ◽

Author(s):

Amandine HENRY ◽

Anthony Michaud ◽

Nicolas Degand ◽

Emmanuelle Bille ◽

Damien Fournier ◽

...

Keyword(s):

Susceptibility Testing ◽

Inhibition Zone ◽

Generation Cephalosporin ◽

Diffusion Method ◽

Disc Diffusion ◽

Disc Diffusion Method ◽

Beta Lactamases ◽

Inhibition Zone Diameter ◽

Zone Diameter ◽

Extended Spectrum Beta Lactamases

Abstract Background: Since the pandemic of ESBL (extended-spectrum beta-lactamases) and the emergence of carbapenemase-producing Enterobacterales there is a renewed interest in temocillin. However, as the molecule was little used, except in Belgium and UK, there are few guidelines for its antibiotic susceptibility testing (AST). We aim to assess the accuracy of the disc diffusion method (DDM) for temocillin susceptibility testing. Methods: Eight hundred eighty-eight Enterobacterales clinical strains of which 61.7% were resistant to 3 rd generation cephalosporin (3GC-R) were included. AST was performed using DDM in comparison to gradient strip tests (GST) and interpreted using the diameter breakpoint of 20mm and MIC breakpoint of 8 mg/L for DDM and GST as recommended by EUCAST-CASFM recommandations. Results: At breakpoint of 8mg/L, temocillin rates of susceptibility were 76.9%, 95.6% and 67.7% for overall, 3GC-S and 3GC-R strains respectively. Ninety-four (10.6%) discrepancies were noticed including 68 (72.3%) major errors and 26 (27.6%) very major errors. Sixty-eight (72.3%) of all errors correspond to inhibition diameters comprised between 17 and 23 mm. The presence of colonies within the inhibition diameter was noticed for 32 (5.3%) strains susceptible to temocillin. Conclusions: DDM lacks accuracy for strains displaying borderline inhibition zone diameter. We suggest applying the concept of area of technical uncertainty (ATU) for standard DDM. The strains displaying a diameter within the ATU should be tested by another method. The significance of colonies within the inhibition zone diameter should be explored.

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A novel concentration gradient microfluidic chip for high-throughput antibiotic susceptibility testing of bacteria

Analytical and Bioanalytical Chemistry ◽

10.1007/s00216-020-03076-8 ◽

2021 ◽

Author(s):

Jiadi Sun ◽

Yijing Ren ◽

Jian Ji ◽

Yu Guo ◽

Xiulan Sun

Keyword(s):

High Throughput ◽

Microfluidic Chip ◽

Concentration Gradient ◽

Antibiotic Susceptibility ◽

Susceptibility Testing ◽

Antibiotic Susceptibility Testing

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Fast Antibiotic Susceptibility Testing via Raman Microspectrometry on Single Bacteria: An MRSA Case Study

ACS Omega ◽

10.1021/acsomega.1c00170 ◽

2021 ◽

Author(s):

Armelle Novelli Rousseau ◽

Nicolas Faure ◽

Fabian Rol ◽

Zohreh Sedaghat ◽

Joël Le Galudec ◽

...

Keyword(s):

Antibiotic Susceptibility ◽

Susceptibility Testing ◽

Antibiotic Susceptibility Testing ◽

Raman Microspectrometry

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Longitudinal Characterization and Transmission Dynamics of Antibiotic-Resistant Organisms in an ICU (LOCATE AROs)

Infection Control and Hospital Epidemiology ◽

10.1017/ice.2020.524 ◽

2020 ◽

Vol 41 (S1) ◽

pp. s42-s43

Author(s):

Kimberley Sukhum ◽

Candice Cass ◽

Meghan Wallace ◽

Caitlin Johnson ◽

Steven Sax ◽

...

Keyword(s):

Antibiotic Susceptibility ◽

Environmental Samples ◽

Susceptibility Testing ◽

Marrow Transplant ◽

Transmission Dynamics ◽

Hospital Environment ◽

Antibiotic Susceptibility Testing ◽

Antibiotic Resistant ◽

Clonal Group ◽

Communal Areas

Background: Healthcare-associated infections caused by antibiotic-resistant organisms (AROs) are a major cause of significant morbidity and mortality. To create and optimize infection prevention strategies, it is crucial to delineate the role of the environment and clinical infections. Methods: Over a 14-month period, we collected environmental samples, patient feces, and patient bloodstream infection (BSI) isolates in a newly built bone marrow transplant (BMT) intensive care unit (ICU). Samples were collected from 13 high-touch areas in the patient room and 4 communal areas. Samples were collected from the old BMT ICU, in the new BMT ICU before patients moved in, and for 1 year after patients moved in. Selective microbiologic culture was used to isolate AROs, and whole-genome sequencing (WGS) was used to determine clonality. Antibiotic susceptibility testing was performed using Kirby-Bauer disk diffusion assays. Using linear mixed modeling, we compared ARO recovery across time and sample area. Results: AROs were collected and cultured from environmental samples, patient feces, and BSI isolates (Fig. 1a). AROs were found both before and after a patient entered the ICU (Fig. 1b). Sink drains had significantly more AROs recovered per sample than any other surface area (P < .001) (Fig. 1c). The most common ARO isolates were Pseudomonas aeruginosa and Stenotrophomonas maltophila (Fig. 1d). The new BMT ICU had fewer AROs recovered per sample than the old BMT ICU (P < .001) and no increase in AROs recovered over the first year of opening (P > .05). Furthermore, there was no difference before versus after patients moved into the hospital (P > .05). Antibiotic susceptibility testing reveal that P. aeruginosa isolates recovered from the old ICU were resistant to more antibiotics than isolates recovered from the new ICU (Fig. 2a). ANI and clonal analyses of P. aeruginosa revealed a large cluster of clonal isolates (34 of 76) (Fig. 2b). This clonal group included isolates found before patients moved into the BMT ICU and patient blood isolates. Furthermore, this clonal group was initially found in only 1 room in the BMT ICU, and over 26 weeks, it was found in sink drains in all 6 rooms sampled (Fig. 2b). Conclusions: AROs are present before patients move into a new BMT ICU, and sink drains act as a reservoir for AROs over time. Furthermore, sink-drain P. aeruginosa isolates are clonally related to isolates found in patient BSIs. Overall, these results provide insight into ARO transmission dynamics in the hospital environment.Funding: Research reported in this publication was supported by the Washington University Institute of Clinical and Translational Sciences grant UL1TR002345 from the National Center for Advancing Translational Sciences (NCATS) of the National Institutes of Health (NIH). The content is solely the responsibility of the authors and does not necessarily represent the official view of the NIH.Disclosures: None

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