Increasing trend in fusidic acid resistance among MRSA isolates in the Netherlands, 2016–23

Abstract

Objectives

Recently, several MRSA community outbreaks occurred in the Netherlands, including one caused by an impetigo-causing MRSA strain resistant to fusidic acid. Since fusidic acid and flucloxacillin are the main treatment options for impetigo, increasing resistance limits treatment possibilities. We examined trends in fusidic acid resistance percentages among MRSA isolates in the Netherlands.

Materials and methods

Data on routine bacteriological cultures between 2016 and 2023 from 30 laboratories were extracted from the national surveillance system on antimicrobial resistance (ISIS–AR). Fusidic acid resistance percentages per year were calculated both overall and per age group for all MRSA isolates, and more specific, for the subset of MRSA isolates from wound/pus/skin samples collected by general practitioners (WPS-GP). Trends were determined using logistic regression and compared with trends among MSSA isolates.

Results

We found an increase in fusidic acid resistance among MRSA isolates from 15% (2016) to 29% (2023) (P < 0.001), which differed significantly (P < 0.001) from the trend among MSSA isolates (10%–12%). An increase was also found in MRSA WPS-GP isolates, both among young children and the population of 13–64 years old, but not among elderly. The trends remained significant after exclusion of isolates associated with known fusidic acid-resistant MRSA outbreaks, both among MRSA isolates overall (OR = 1.10, 95% CI: 1.07–1.14, P < 0.001) and among MRSA WPS-GP isolates (OR = 1.14, 1.07–1.21, P < 0.001).

Conclusions

In conclusion, an increasing trend in fusidic acid resistance was found among MRSA isolates. Since impaired treatment for impetigo might ease the spread of (fusidic acid-resistant) MRSA, extra vigilance is warranted.

Introduction

Staphylococcus aureus is a commensal bacterium that can act as a pathogen causing skin infections such as impetigo.^1,2 Topical fusidic acid is the first-line treatment of impetigo in the Netherlands, as well as in other European countries,^3,4 and is often prescribed empirically by general practitioners (GPs).⁵ In the Netherlands, oral flucloxacillin is the second choice in case of treatment failure (only effective against MSSA).

Transmission of impetigo with fusidic acid-resistant S. aureus has been reported in the Netherlands and other European countries,^2,6–8 and a slight increase of fusidic acid resistance was found among wound and pus samples collected by GPs between 2019 (20%) and 2023 (23%) in the Netherlands.⁹ In Norway and Denmark, countries with a similar percentage of MRSA among S. aureus as the Netherlands (for the percentage of MRSA in the Netherlands, see Figure S1, available as Supplementary data at JAC-AMR Online), fusidic acid resistance was found on the rise between 2016 and 2023 among MRSA isolates specifically.^10–12 Besides, multiple outbreaks with fusidic acid-resistant MRSA have been reported to the ECDC in recent years: among others, an outbreak of impetigo cases in the Netherlands in 2019 caused by an MRSA MT4627 (ST121) strain.¹³ This raised concern as fusidic acid and flucloxacillin are both ineffective in this case. The increase of fusidic acid resistance in MRSA is especially worrisome as this may lead to unnoticed spread of MRSA. Since GPs in the Netherlands generally only take cultures in case of treatment failure, patients with insufficiently treated impetigo will stay contagious for a longer period, thereby facilitating transmission of MRSA.

The National Institute for Public Health and the Environment (RIVM) carries out surveillance on antimicrobial resistance (AMR) in the Netherlands based on data from the Infectious Diseases Surveillance Information System–Antimicrobial Resistance (ISIS–AR). The aim of this study was to investigate fusidic acid resistance percentages among MRSA isolates in the Netherlands between 2016 and 2023, using data from this surveillance system. To identify whether potential changes in fusidic acid resistance were specific for MRSA or whether they account for S. aureus in general, these data were compared with fusidic acid resistance percentages among MSSA isolates.

Materials and methods

Data collection

ISIS–AR systematically collects, integrates and analyses microbiological and epidemiological data from medical microbiology laboratories (MMLs) across the Netherlands. The database includes detailed information from routine diagnostics of positive bacterial cultures, including bacterial species identification, antimicrobial susceptibility test results (AST), patient demographics (such as age, sex and type of healthcare setting where the sample was taken), specimen type (e.g. blood, urine) and sampling date.¹⁴ From the 48 MMLs in the Netherlands, 37 continuously delivered data from 2016 until 2023. The first diagnostic (infection-related) S. aureus isolate per patient per year was selected as well as information on AST for fusidic acid and results from MRSA confirmation tests. In addition, AST results were included for cefoxitin and/or flucloxacillin and/or oxacillin, whichever was available. To minimize bias, an antibiotic agent should be tested in at least 50% of the isolates and at least 80% of the crude test results should be reinterpretable by EUCAST breakpoints for each MML. This resulted in 30 MMLs eligible for inclusion in the analyses.

Calculation of resistance percentages

An S. aureus isolate was considered MRSA if the presence of a mecA or mecC gene or pbp2 production was demonstrated, or in case data on such confirmation tests was unavailable, if resistance to cefoxitin based on laboratory interpretation was demonstrated or, if also unavailable, if resistance to flucloxacillin/oxacillin based on laboratory interpretation was demonstrated. To approximate the population with impetigo as closely as possible, for both MRSA and MSSA a subset of isolates was identified that were isolated from wound/pus/skin samples collected by GPs (hereafter referred to as WPS-GP). Susceptibility to topical fusidic acid was estimated based on reinterpretation of raw testing values according to EUCAST version 14.0 (R > 0.5 mg/L). Within both the MRSA and MSSA group the prevalence of fusidic acid resistance was calculated as percentage of the total number of isolates. Furthermore, fusidic acid resistance percentages were calculated for WPS-GP MRSA isolates. Lastly, MRSA WPS-GP isolates were categorized by age group (0–12, 13–64 and ≥65 years old) since resistance patterns and type of diagnosis might be different between age groups, as impetigo mainly affects the age group 0–12. We therefore assume that the approximation of impetigo-related isolates is most accurate for the MRSA WPS-GP isolates within the youngest age group. Resistance was calculated per year.

Calculation of time trends

Time trends were assessed using logistic regression models for both MSSA and MRSA within all materials and healthcare settings and for WPS-GP specifically, overall and stratified by age group, covering the period from 2016 to 2023. Models were fitted only where the number of susceptible and resistant isolates for all strata for all years was ≥10. Logistic regression was performed with the AST interpretation for topical fusidic acid as the binary outcome (resistant versus non-resistant) and the Akaike information criterion (AIC) was used to choose the best fitting model. In case a nonlinear trend fitted the data best for one of the groups (i.e. MSSA or MRSA within all materials and healthcare settings and WPS-GP specifically, overall or stratified by age group) both a linear and nonlinear trend were calculated for all groups. The nonlinear trends were calculated per 2 years for interpretation purposes. The variables age and sex were explored as potential confounders and added to the regression model. For comparing trends between MRSA and MSSA isolates an interaction term for MRSA/MSSA was added to the model. Calculations were performed in R version 4.4.3. A two-sided P value of <0.05 was considered statistically significant.

Sensitivity analysis

To minimize the potential impact of overrepresentation of MRSA outbreak-related isolates with fusidic acid resistance on observed trends, we repeated the analyses after excluding these outbreak-related isolates. In the Netherlands, multiple-locus variable number of tandem repeat analysis (MLVA) complex MC0005 (mostly ST5) and MLVA type MT4627 (ST121), which is part of MLVA complex MC0030, are associated with fusidic acid resistance (∼50% and 100% fusidic acid-resistant in 2023, respectively) and related to community MRSA outbreaks.¹³ To identify isolates in the ISIS–AR database belonging to this complex and type, molecular typing results from the Dutch national MRSA surveillance system (Type-Ned) were linked to the ISIS–AR dataset.¹⁵ First, isolates were matched based on laboratory, sample number, isolate number and species. If matching failed, isolates were matched on the basis of patient characteristics.

Results

The number of isolates included and associated patient characteristics are shown in Table 1. Overall, we included 344 387 MSSA isolates from 308 606 different patients, 7553 MRSA isolates from 7150 patients, 59 498 MSSA WPS-GP isolates from 57 511 patients and 1677 MRSA WPS-GP isolates from 1648 patients. Of the MRSA WPS-GP isolates 242 (14.4%) came from patients aged 0–12 years, 1168 (69.6%) from patients aged 13–64 years and 267 (15.9%) from patients aged ≥65 years.

Table 1.

Numbers of MSSA and MRSA isolates from samples from all materials and healthcare settings and from wound/pus/skin samples collected by GPs (WPS-GP), and related patient characteristics

	MSSA		MRSA		MSSA WPS-GP		MRSA WPS-GP
	N	%	N	%	N	%	N	%
Patients	308 606		7 150	2.3a	57 511		1 648	2.8a
Isolates	344 387		7 553	2.1a	59 498		1 677	2.7a
Age
0–12 years	30 068	8.7	751	9.9	10 254	17.2	242	14.4
13–64 years	164 154	47.7	4 470	59.2	31 788	53.4	1 168	69.6
≥65 years	150 165	43.6	2 332	30.9	17 456	29.3	267	15.9
Sex
Male	182 536	53.0	4 485	59.4	28 596	48.1	972	58.0
Female	161 851	47.0	3 068	40.6	30 902	51.9	705	42.0
Sample material
Blood	16 032	4.7	234	3.1
Respiratory	49 907	14.5	1 152	15.3
Wound/pus/skin	214 086	62.2	4 816	63.8	59 498	100	1 677	100
Other	64 362	18.7	1 351	17.9
Healthcare setting
General practitioner	98 369	28.6	2 477	32.8	59 498	100	1 677	100
Inpatient department	61 417	17.8	1 360	18.0
Outpatient department	142 525	41.4	2 655	35.2
Other	42 076	12.2	1 061	14.0

^aPercentage of MRSA among the number of patients and the number of isolates, of samples from all materials and healthcare settings and from WPS-GP.

The annual fusidic acid resistance percentage increased significantly from 15% in 2016 to 29% in 2023 among MRSA isolates (OR = 1.13, 95% CI: 1.09–1.16, P < 0.001) and from 10% in 2016 to 12% in 2023 among MSSA isolates (OR = 1.01, 95% CI: 1.00–1.02, P < 0.001) as determined by the linear regression model (Figure 1a). The difference between the trends of MRSA and MSSA was statistically significant (OR = 1.11, 95% CI: 1.08–1.14, P < 0.001). A rising trend was also found among WPS-GP samples and was more profound among MRSA isolates (OR = 1.16, 95% CI: 1.11–1.23, P < 0.001) compared with MSSA isolates (OR = 1.02, 95% CI: 1.01–1.03, P < 0.001) (Figure 1b). The difference between trends between both groups was again statistically significant (OR = 1.14, 95% CI: 1.08–1.20, P < 0.001). The quadratic model best fitted the time trend for both the MRSA and MSSA isolates from all materials and healthcare settings when comparing the AIC with the linear model. Therefore, additional ORs were calculated per 2 years which were highest and significant for 2022–2023 versus 2016–2017 (Table S1).

Figure 1.

Yearly fusidic acid resistance percentages in MSSA and MRSA isolates between 2016 and 2023 in the Netherlands. The left two panels (a) show resistance percentages in isolates from all materials and healthcare settings. The right two panels (b) show resistance percentages in isolates from WPS-GP. The error bars show the 95% CI. N indicates the total number of isolates tested for fusidic acid between 2016 and 2023. ^aLinear regression analysis significant with a P value of <0.001.

After stratification of MRSA WPS-GP isolates by age group, different resistance trends over time could be observed per age group (Figure 2). As the number of resistant isolates was below 10 for multiple years, no trend analyses were performed for the separate age groups. Visually, fusidic acid resistance increased over time among 0–12 year olds, with a peak in 2019, while among 13–64 year olds no such peak was visible and the trend of resistance percentages seemed less steep. Resistance percentages for the group ≥65 years old remained more stable.

Figure 2.

Yearly fusidic acid resistance percentages in MRSA from WPS-GP between 2016 and 2023 per age group in the Netherlands. Age groups are defined as follows: 0–12 years old, 13–64 years old and ≥65 years old. Numbers above bars show the total number of MRSA isolates tested for fusidic acid susceptibility per year. There were no trend analyses performed for the separate age groups as the number of resistant isolates was <10 for multiple years.

Sensitivity analysis

Of the patients with MRSA and MRSA from WPS-GP, 5737 (80.2%) and 1384 (84.0%) could be linked to an MRSA isolate in Type-Ned with molecular typing data, respectively. The distribution of age, sex, sample material and healthcare setting were similar between the full MRSA dataset and the MRSA dataset with linked molecular typing data, as well as between the MRSA-WPS-GP dataset and the MRSA-WPS-GP with linked molecular typing data (data not shown).

When excluding MLVA complex MC0005 (mostly ST5) and MLVA type MT4627 (ST121), which is part of MLVA complex MC0030, from the MRSA dataset including all materials and healthcare settings, we found a less steep but still significant trend for fusidic acid resistance percentages. The percentage increased from 12% in 2016 to 22% in 2023 (OR = 1.10, 95% CI: 1.07–1.14, P < 0.001) (Figure 3). When excluding MLVA complex MC0005 and MLVA type MT4627 from the MRSA-WPS-GP dataset, we again found a less steep but still significant trend with fusidic acid resistance percentages increasing from 9% in 2016 to 21% in 2023 (OR = 1.14, 95% CI: 1.07–1.21, P < 0.001). The proportions of MLVA-complexes over time for both the MRSA isolates from all materials and healthcare settings and from WPS-GP are shown in the Supplementary figures, with Figures S2 and S3 showing proportions for fusidic acid-resistant MRSA specifically and Figure S4 and S5 for fusidic acid-resistant and -susceptible MRSA combined.

Figure 3.

Yearly fusidic acid resistance percentages in MRSA linked to genotyping information from the national MRSA surveillance (Type-Ned) between 2016 and 2023 in the Netherlands. The left two panels (a) show isolates from all materials and healthcare settings including and excluding MC0005 (mostly ST5) and MT4627 (ST121). The right two panels (b) show isolates from WPS-GP including and excluding MC0005 and MT4627. The error bars show the 95% CI. N indicates the total number of isolates tested for fusidic acid between 2016 and 2023. ^aLinear regression analysis significant with a P value of <0.001.

Discussion

The aim of this study was to investigate trends in fusidic acid resistance percentages among MRSA isolates over a period of 8 years in the Netherlands using surveillance data from ISIS–AR. The results show an increase in fusidic acid resistance among MRSA isolates from 15% to 29%, with the increase being more pronounced compared with fusidic acid resistance in MSSA. Analyses focusing on MRSA WPS-GP isolates showed similar findings, with a sudden increase from 2018 in young children (≤12 years old). In sensitivity analyses, on exclusion of MLVA complex MC0005 (mostly ST5) and MLVA type MT4627 (ST121) that are associated with fusidic acid-resistant MRSA outbreaks, the rising trend was still visible, although less steep. This finding suggests that the observed increase in resistance could not be fully attributed to this MLVA complex and MLVA type.

In the Netherlands, fusidic acid is the first choice treatment for impetigo. In case of treatment failure, flucloxacillin is prescribed. Impetigo caused by fusidic acid-resistant MSSA, therefore, usually is successfully treated with flucloxacillin after the first-line therapy fails. However, although ongoing transmission is reduced as soon as the second-line treatment is started, the patient with fusidic acid-resistant impetigo has been contagious for a longer time than if it would have been susceptible to first-line treatment. This longer time of contagiousness may be a driver for the spread of fusidic acid-resistant strains. The more pronounced increase in fusidic acid resistance among MRSA isolates compared with MSSA isolates may be explained by the ineffective treatment of impetigo infections caused by fusidic acid-resistant MRSA. If the impetigo is caused by fusidic acid-resistant MRSA, both first- and second-line treatments are ineffective, and patients are likely to remain contagious within the community for an even longer period, facilitating transmission and contributing to an increased proportion of resistant isolates. Although, due to the higher numbers, fusidic acid-resistant MSSA probably is the main driver of the spread of fusidic acid resistance, the increase in fusidic acid resistance percentages among MRSA isolates poses a potential threat to public health. For fusidic acid-resistant MRSA limited treatment options are available and the spread of MRSA is eased. It may, therefore, be advisable to culture skin lesions caused by impetigo at an earlier stage than only after treatment failure. As a reaction to the outcomes of this study, the Dutch General Practitioner Federation indeed advised GPs to culture patients with impetigo infection prior to antibiotic treatment in case of increased risk of MRSA or in case the patient may be part of a regional cluster of patients with fusidic acid treatment failure.¹⁶

The increase in fusidic acid resistance percentage among MRSA isolates is also seen in other European countries, for example in Denmark (from 18% to 26% between 2016 and 2023) and Norway (from 12% to 16% between 2016 and 2023) and may be driven by the spread of a fusidic acid-resistant MRSA clone.^8,10–12 Meanwhile, the percentage fusidic acid resistance among S. aureus bacteraemia cases in Denmark remained stable between 2014 and 2023 at 12%, which corresponds to the resistance percentage that we found among MSSA isolates, although we did not analyse trends for bacteraemia cases specifically.¹¹ Similarly, a stable trend was found in Norway in fusidic acid resistance among S. aureus wound isolates between 2016 and 2023 at ∼7%.^10,12 Together, these results support our finding that the trend of fusidic acid resistance among MRSA isolates increases and can differ from MSSA isolates.

The steep increases in resistance visible in young children (age 0–12 years old) in 2018 with a peak around 2019 and 2023 may imply transmission of a fusidic acid-resistant MRSA strain. The peak in 2019 is likely influenced by the outbreak in the Netherlands that year.¹³ Impetigo is easily transmitted between children. In the Netherlands, children with impetigo are allowed to go to daycare and school, although notification of the impetigo to the childcare worker or teacher is recommended. This facilitates transmission, which may explain part of the increased spread of fusidic acid-resistant MRSA among 0–12 year-old children. However, the rising resistance trend among those between 13 and 64 years of age is more remarkable. This suggests that there may be a general increase in fusidic acid resistance among MRSA isolates that cannot be directly attributed to the known outbreak cluster. A possible explanation might be that the outbreak in 2019 led to an increased spread of fusidic acid-resistant MRSA causing other wound/pus/skin infections next to impetigo among those between 13 and 64 years of age. This spread might for example be driven by children infecting their parents and other relatives. Another reason for the increase outside the outbreak cluster could be that fusidic acid resistance genes (fusB and fusC) can be transferred between strains of different types of MRSA.¹⁷ The high diversity of types with resistance already in the early years of our observation period (see Figures S2–S5) suggests spread of these resistance genes occurred at some unknown time in the past.

The increase of fusidic acid resistance among MRSA isolates restricts the number of treatment options for impetigo. Possible alternative topical antibiotics are mupirocin and retapamulin. In the Netherlands, however, mupirocin is primarily used for eradication of MRSA carriage in healthcare professionals (also known as ‘the search and destroy’ policy).¹⁸ Owing to this policy, MRSA is still present at very low levels in the Netherlands.¹⁹ Only in recurrent cases of impetigo with S. aureus, mupirocin is advised. In France, mupirocin is the first choice treatment for impetigo infections due to already high percentages of fusidic acid resistance.²⁰ Retapamulin has been shown to be as effective as fusidic acid in clearing an impetigo infection in a randomized non-inferiority study across multiple countries.²¹ However, data on its effectiveness in eradicating MRSA impetigo infections are limited. As a reaction to the rise in fusidic acid resistance, a single blind randomized controlled trial was set up in New Zealand.²² The aim of this RCT was to determine non-inferiority treatment of antiseptics such as hydrogen peroxide, since this type of treatment could lower the risk of acquiring resistance. The results of this study are still awaited. Overall, topical treatment options for MRSA impetigo infections are limited as mupirocin is advised to be used only in specific cases and more research is needed to prove efficacy of alternative topical treatments.

One of the strengths of this study is the use of a large national database with a high coverage of MMLs across the Netherlands.¹⁴ Incoming data are checked on a regular basis and verified in consultation with MMLs before being validated and incorporated into the database. This quality check process results in a database in which inaccuracies are minimized. Another strength is that isolates from the ISIS–AR database were linked to data in the Type-Ned database, which enabled us to include molecular typing data in our analyses and exclude isolates associated with fusidic acid-resistant MRSA outbreaks.

A limitation of this study is the lack of clinical data within ISIS–AR. By selecting WPS-GP we attempted to approximate the population with impetigo as closely as possible. However, part of the selection might be non-impetigo related, especially among the ≥65 age group. In this age group we also expect patients with other infections such as surgical site infections or diabetic foot ulcers. Another limitation is that the protocol for the national Type-Ned MRSA surveillance prescribes to send only one MRSA isolate per patient per 3 years for molecular typing. In addition to this, ISIS–AR collects the first S. aureus isolate per patient per year, either MSSA or MRSA. Therefore, only part of the ISIS–AR dataset could be linked to the Type-Ned dataset and only for a part of all MRSA isolates from ISIS–AR molecular data was available. However, patient characteristics from the linked sub-selection were similar to the selection for the main analyses, meaning that differences in outcomes cannot be attributed to different patient populations.

For the interpretation of the resistance percentages, we must consider that GPs usually do not take cultures for impetigo, unless after treatment failure, resulting in overestimation of resistance percentages in WPS-GP. We assumed that culture practice did not change over time, except during the outbreak in 2019 in that specific geographical area,¹³ and that selective sampling would not have influenced trends over time. It is, however, possible that the outbreak led to more awareness of fusidic acid-resistant MRSA among GPs, resulting in a sustained, low-threshold approach to performing cultures.

To conclude, this study shows an increasing trend in fusidic acid resistance among MRSA isolates, which is more profound compared with the trend in MSSA isolates and cannot be fully explained by a specific MLVA complex or type associated with fusidic acid-resistant MRSA outbreaks. Although the percentage of MRSA among S. aureus isolates in the Netherlands is still low, the increase of fusidic acid resistance among MRSA isolates might pose a public health threat as impaired treatment can lead to the spread of MRSA. On the basis of these findings, surveillance to detect fusidic acid resistance among S. aureus isolates in a timely fashion is warranted to optimize treatment guidelines. Furthermore, fusidic acid resistance should be monitored for MRSA and MSSA separately, as this study shows that resistance percentages differ. When focusing on S. aureus isolates overall, this steeper increase in MRSA would not have been noticed. Finally, it is recommended to culture patients with impetigo before antibiotic treatment in case of increased risk of MRSA. Future research could aim to acquire an unbiased selection of samples, for example, by sampling all patients with impetigo at GPs. This would gain insight into the actual resistance percentages and the impact of impetigo outbreaks on these resistance percentages.

Members of the ISIS-AR study group

J.W.T. Cohen Stuart, Noordwest Ziekenhuisgroep, Department of Medical Microbiology, Alkmaar. D.C. Melles, Meander Medical Center, Department of Medical Microbiology, Amersfoort. K. van Dijk, Amsterdam UMC, University of Amsterdam, Department of Medical Microbiology and Infection Prevention, Amsterdam Infection and Immunity Institute, Amsterdam. R. Schade, Amsterdam UMC, University of Amsterdam, Department of Medical Microbiology and Infection Prevention, Amsterdam Infection and Immunity Institute, Amsterdam. A. Alzubaidy, Atalmedial, Department of Medical Microbiology, Amsterdam. M. Scholing, OLVG Lab BV, Department of Medical Microbiology, Amsterdam. S.D. Kuil, Public Health Service, Public Health Laboratory, Amsterdam. G.J. Blaauw, Gelre Hospitals, Department of Medical Microbiology and Infection prevention, Apeldoorn. ISIS-AR Project team: W. Altorf-van der Kuil, S.M. Bierman, S.C. de Greeff, S.R. Groenendijk, R. Hertroys, L. Kruithof, I.M. Nauta, D.W. Notermans, J. Polman, W.J. van den Reek, A.F. Schoffelen, F. Velthuis, C.C.H. Wielders, B.J. de Wit, R.E. Zoetigheid, Centre for Infectious Disease Control (CIb), National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands. W. van den Bijllaardt, Microvida Amphia, Laboratory for Microbiology and Infection Control, Breda. E.M. Kraan, IJsselland hospital, Department of Medical Microbiology, Capelle a/d IJssel. M.B. Haeseker, Reinier de Graaf Group, Department of Medical Microbiology, Delft. J.M. da Silva, Deventer Hospital, Department of Medical Microbiology, Deventer. E. de Jong, Slingeland Hospital, Department of Medical Microbiology, Doetinchem. B. Maraha, Albert Schweitzer Hospital, Department of Medical Microbiology, Dordrecht. M.P.A. van Meer, Department of Medical Microbiology and Immunology, Dicoon, Elst. B.B. Wintermans, Admiraal De Ruyter Hospital, Department of Medical Microbiology, Goes. V. Hira, Groene Hart Ziekenhuis, Department of Medical Microbiology and Infection Prevention, Gouda. A.E. Muller, Haaglanden MC, Department of Medical Microbiology, ‘s-Gravenhage. M. Wong, Haga Hospital, Department of Medical Microbiology, ‘s-Gravenhage. P. Huizinga, Certe, Groningen. E. Bathoorn, University of Groningen, University Medical Center, Department of Medical Microbiology, Groningen. M. Lokate, University of Groningen, University Medical Center, Department of Medical Microbiology, Groningen. J. Sinnige, Regional Public Health Laboratory Haarlem, Haarlem. L.E.A. Bank, St Jansdal Hospital, Department of Medical Microbiology, Harderwijk. F.W. Sebens, Labmicta, Hengelo. E. Kolwijck, Jeroen Bosch Hospital, Department of Medical Microbiology and Infection Control, ‘s-Hertogenbosch. E.A. Reuland, CBSL, Tergooi MC, Department of Medical Microbiology, Hilversum. J.W. Dorigo-Zetsma, CBSL, Tergooi MC, Department of Medical Microbiology, Hilversum. S. de Jager, Comicro, Department of Medical Microbiology, Hoorn. M.A. Leversteijn-van Hall, Eurofins Clinical Diagnostics, Department of Medical Microbiology, Leiden. M.T. van der Beek, Leiden University Medical Center, Department of Medical Microbiology, Leiden. S.P. van Mens, Maastricht University Medical Centre, Department of Medical Microbiology, Infectious Diseases and Infection Prevention, Maastricht. E. Schaftenaar, St Antonius Hospital, Department of Medical Microbiology and Immunology, Nieuwegein/Utrecht. J.C. Rahamat-Langendoen, Radboud University Medical Center, Department of Medical Microbiology, Nijmegen. P.D.J. Sturm, Laurentius Hospital, Roermond. B.M.W. Diederen, Bravis Hospital, Department of Medical Microbiology, Roosendaal. L.G.M. Bode, Erasmus University Medical Center, Department of Medical Microbiology and Infectious Diseases, Rotterdam. D.S.Y. Ong, Franciscus Gasthuis and Vlietland, Department of Medical Microbiology and Infection Control, Rotterdam. M. van Rijn, Ikazia Hospital, Department of Medical Microbiology, Rotterdam. S. Dinant, Maasstad Hospital, Department of Medical Microbiology, Rotterdam. M. den Reijer, Star-SHL, Rotterdam. D.W. van Dam, Zuyderland Medical Centre, Department of Medical Microbiology and Infection Control, Sittard-Geleen. E.I.G.B. de Brauwer, Zuyderland Medical Centre, Department of Medical Microbiology and Infection Control, Sittard-Geleen. A.L.E. van Arkel, Microvida ZorgSaam, Department of Medical Microbiology, Terneuzen. J.J.J.M. Stohr, Microvida Elisabeth-Tweesteden Hospital, Department of Medical Microbiology, Tilburg. A.L.M. Vlek, Diakonessenhuis, Department of Medical Microbiology and Immunology, Utrecht. M. de Graaf, Saltro Diagnostic Centre, Department of Medical Microbiology, Utrecht. A. Troelstra, University Medical Center Utrecht, Department of Medical Microbiology, Utrecht. F.N.J. Frakking, University Medical Center Utrecht, Department of Medical Microbiology, Utrecht. K.B. Gast, Eurofins-PAMM, Department of Medical Microbiology, Veldhoven. H.R.A. Streefkerk, VieCuri Medical Center, Department of Medical Microbiology, Venlo. S.B. Debast, Isala Hospital, Laboratory of Medical Microbiology and Infectious Diseases, Zwolle.

Funding

This work was supported by the Dutch Ministry of Health, Welfare and Sport.

Transparency declarations

None declared.

Supplementary data

Figures S1–S5 and Table S1 are available as Supplementary data at JAC-AMR Online.