Publikationsdatenbank

Biocide susceptibility testing:
development of a broth microdilution method (2019)

Art

Poster

Autoren

Schug, Angela R. (WE 7)

Feßler, Andrea T. (WE 7)

Bartel, Alexander (WE 16)

Scholtzek, Anissa D. (WE 7)

Meurer, Marita

Brombach, Julian (WE 7)

Hensel, Vivian

Schwarz, Stefan (WE 7)

Kongress

8th Symposium on Antimicrobial Resistance in Animals and the Environment

Tours Val de Loire - France, 01. – 03.07.2019

Quelle

8th Symposium on Antimicrobial Resistance in Animals and the Environment : Abstracts book : 1-3 July 2019 — UMR 1282 Infectiologie et Santé Publique Institut National de la Recherche Agronomique (Hrsg.)

France: INRA Science & Impact, 2019 — S. 62

Sprache

Englisch

Verweise

URL (Volltext): https://symposium.inrae.fr/arae2019/Abstract-Book

Kontakt

Institut für Mikrobiologie und Tierseuchen

Robert-von-Ostertag-Str. 7-13
14163 Berlin
+49 30 838 51843 / 66949
mikrobiologie@vetmed.fu-berlin.de

Abstract / Zusammenfassung

Background and objectives:
In contrast to biocide efficacy testing, biocide susceptibility testing (BST) lacks standardized methods. Therefore, a broth macrodilution protocol has been developed [1], based on which a broth microdilution method for BST should be established.

Materials and methods:
The reference strainsStaphylococcus aureusATCC®6538, Entero-coccus hiraeATCC®10541, Escherichia coli ATCC®10536 and Pseudomonas aeruginosaATCC®15442 were comparatively investigated seventimes by broth microdilution for their minimal inhibitory concentrations (MIC) to benzalkonium chloride (BAC), glutardialdehyde (GLU), chlorhexidine (CHX) and isopropanol (ISO). The following parameters were tested:i) 1stsubculture (SC), and 2ndSC, ii)inoculum preparation by direct colony suspension method (DCS) with/without glass beads (GB) and iii) incubation for 24, 48, and 72 h.

Results:
For each reference strain/biocide combination (with all aforementioned parameters), a total of 84 MIC values were determined. The modal MIC ± one dilution step was defined as the acceptable range. In total, 88.1-100 % of the MIC values were within this range for S.aureusATCC®6538, 85.7-100% for E.hiraeATCC®10541, 94.5-100% for E.coli ATCC®10536, and 96.4-100% for P.aeruginosa ATCC®15442. Statistical analysis revealed no significant differences regarding the stability of the method within the different parameters. However, increased incubation times resulted in higher MIC values. Within the 24 h-values of all subgroups (subgroup= one species/biocide combination, regarding the parameters i) + ii)), only six of 64 parameter-combinations (9.38 %) yielded values outside the acceptable range, and those being equally distributed between DCS with or without GB.Regarding the different SCs used, 4/64 for 1stSC and 2/64 for 2ndSC were outside the acceptable range. The proposed broth microdilution method for BST of bacteria is as follows: use of a fresh overnight culture (1stSC or 2ndSC), inoculum preparation via DCS with or without GB, and incubation at 37 °C for 24 h. The broth microdilution MIC values differed only slightly from the broth macrodilution results obtained for BAC, GLU and ISO (same modal MIC values for 7/12 reference strain/biocide combinations;5/12 within ± one dilution step) [1].

Conclusion:
This method allows an easier BST than the labour-intensive broth macrodilution and can contribute to a harmonization of the BST of bacterial pathogens in routine diagnostics.