76 Chapter 4 Discussion The main finding of our study is the success rate of decolonization of 74% after the first treatment attempt, which is relatively high when compared to previous literature. In the Dutch study by Ammerlaan et al. in 2011, this rate was 56% [18]. A possible explanation for this difference may be that the guideline adherence for treatment choice was much lower in the study by Ammerlaan (62%) compared to our study (90%). A second explanation may be that in our study – in the majority of cases – household members were screened and treated simultaneously, preventing failure because of recolonization by untreated colonized household contacts. In the time of the study by Ammerlaan et al, according to the Dutch guideline, household members were only screened if the first decolonization attempt had failed. Routine screening of household members before starting treatment was not included in the guideline until 2012. The success rate of topical treatment in combination with systemic antibiotics – in our study – is decidedly high compared to topical treatment without systemic antibiotics in the literature, supporting the current guideline. Earlier studies have shown a success rate of approximately 40% after the first decolonization attempt in patients that were treated with topical treatment alone [21, 22]. There were no apparent differences in success rates between different antibiotic regimens. The combination of doxycycline-rifampicin had the highest success rate but this did not reach statistically significance. This combination is one of the first choice regimens in the Dutch guideline. There was no difference in effectivity between a treatment duration of 7 days as compared to 10-14 days. This supports the guideline recommendation of a minimum antibiotic treatment of 7 days [12]. Being part of a known household cluster and immunocompromised status were associated with failure at the first treatment attempt. In multivariable analysis only immunocompromised status remained an independent risk factor for failure at the first treatment attempt, although there were few patients (12) in this group. This differs from an earlier study by Ammerlaan et al, in which chronic pulmonary disease, ADL dependency, throat carriage, perineal carriage and the presence of a device were associated with treatment failure [20]. This difference may be explained by the difference in study population, as Ammerlaan et al did not exclude uncomplicated carriers from their analyses. The fact that 27/224 (12%) of the referred patients were no longer colonized with MRSA at the time of visiting the outpatient clinic is a relevant observation. It illustrates the possibility of spontaneous clearance and the importance of repeated screening before starting treatment.
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