Introduction of a penicillin allergy de-labelling program with direct oral challenge and its effects on utilization of beta-lactam antimicrobials: a multicenter retrospective parallel cohort study.

BACKGROUND: Self-reported penicillin allergy labels are common and often inaccurate after assessment. These labels can lead to reduced use of first-line beta-lactam antibiotics and worse outcomes. We measured the impact of a previously performed inpatient proactive systematic penicillin allergy de-labelling program on subsequent antibiotic use. This prior program included assessment, risk-stratification, and low risk direct oral amoxicillin challenge. METHODS: We performed a retrospective comparison of parallel cohorts from two separate tertiary care hospital campuses in Ottawa, Canada across two penicillin de-labelling intervention periods across April 15th to April 30th, 2021, and February 15th to March 8th, 2022. Outcomes, including penicillin allergy labelling and antibiotic use, were collected for the index admission and the subsequent 6-month period. Descriptive statistics and multivariate regression analyses were performed. RESULTS: A total of 368 patients with penicillin allergy label were included across two campuses and study periods. 24 (13.8%) patients in the intervention groups had sustained penicillin allergy label removal at 30 days from admission vs. 3 (1.5%) in the non-intervention group (p < 0.001). In the 6-months following admission, beta-lactams were prescribed more frequently in the intervention groups vs. the non-intervention groups for all patients (28 [16.1%] vs.15 [7.7%], p = 0.04) and were prescribed more frequently amongst those who received at least one antibiotic (28/46 [60.9%] vs.15/40 [37.5%], p = 0.097). In a multivariate regression analysis, the intervention groups were found to be associated with an increased odds of beta-lactam prescribing in all patients (OR 2.49, 95%CI 1.29-5.02) and in those prescribed at least one antibiotic (OR 2.44, 95%CI 1.00-6.15). No drug-related adverse events were reported. CONCLUSIONS: Proactive penicillin allergy de-labelling for inpatients was associated with a reduction in penicillin allergy labels and increased utilization of beta-lactams in the subsequent 6-months.

WHO's essential medicines and AWaRe: recommendations on first- and second-choice antibiotics for empiric treatment of clinical infections.

The WHO Model List of Essential Medicines (EML) prioritizes medicines that have significant global public health value. The EML can also deliver important messages on appropriate medicine use. Since 2017, in response to the growing challenge of antimicrobial resistance, antibiotics on the EML have been reviewed and categorized into three groups: Access, Watch, and Reserve, leading to a new categorization called AWaRe. These categories were developed taking into account the impact of different antibiotics and classes on antimicrobial resistance and the implications for their appropriate use. The 2023 AWaRe classification provides empirical guidance on 41 essential antibiotics for over 30 clinical infections targeting both the primary health care and hospital facility setting. A further 257 antibiotics not included on the EML have been allocated an AWaRe group for stewardship and monitoring purposes. This article describes the development of AWaRe, focussing on the clinical evidence base that guided the selection of Access, Watch, or Reserve antibiotics as first and second choices for each infection. The overarching objective was to offer a tool for optimizing the quality of global antibiotic prescribing and reduce inappropriate use by encouraging the use of Access antibiotics (or no antibiotics) where appropriate. This clinical evidence evaluation and subsequent EML recommendations are the basis for the AWaRe antibiotic book and related smartphone applications. By providing guidance on antibiotic prioritization, AWaRe aims to facilitate the revision of national lists of essential medicines, update national prescribing guidelines, and supervise antibiotic use. Adherence to AWaRe would extend the effectiveness of current antibiotics while helping countries expand access to these life-saving medicines for the benefit of current and future patients, health professionals, and the environment.

The Impact of Antimicrobial Therapy Duration in the Treatment of Prosthetic Joint Infections Depending on Surgical Strategies: A Systematic Review and Meta-analysis.

The aim of this systematic review was to address the question if short antibiotic treatment (SAT; at least 4 but <12 weeks) versus long antibiotic treatment (LAT) affects outcomes in prosthetic joint infections (PJIs). Database research (Medline, Embase, Web of Science, Scopus, Cochrane) retrieved 3740 articles, of which 10 studies were included in the analysis. Compared to LAT, 11% lower odds of treatment failure in the SAT group were found, although the difference was not statistically significant (pooled odds ratio, 0.89 [95% confidence interval, .53-1.50]). No difference in treatment failure was found between SAT and LAT once stratified by type of surgery, studies conducted in the United States versus Europe, study design, and follow-up. There is still no conclusive evidence that antibiotic treatment of PJIs for 12 weeks or longer is associated with better outcomes, irrespective of the type of surgical procedure. Most recent, high-quality studies tend to favor longer antibiotic courses, making them preferable in most situations.

Detection of Covid-19 Outbreaks Using Built Environment Testing for SARS-CoV-2.

Built Environment Testing for SARS-CoV-2Wastewater testing has proven to be a valuable tool for forecasting Covid-19 outbreaks. Fralick et al. now report that swabbing of surfaces (i.e., floors) for SARS-CoV-2 may provide a similar benefit for predicting outbreaks in long-term care homes.

The WHO essential medicines list AWaRe book: from a list to a quality improvement system.

Antibiotics are often prescribed inappropriately, either when they are not necessary or with an unnecessarily broad spectrum of activity. AWaRe (AccessWatchReserve) is a system developed by WHO to classify antibiotics based on their spectrum of activity and potential for favouring the development of antibiotic resistance (Access: narrow spectrum/low potential for resistance; Watch: broader spectrum/higher potential for resistance; Reserve: last resort antibiotics to use very selectively). The WHO target is that by 2023, at least 60% of prescribed antibiotics globally should be from the Access category. The WHO AWaRe Book aims to improve empiric antibiotic prescribing by providing simple guidance for common infections based on the principles of AWaRe in alignment with the Model Lists of Essential Medicines for adults and children.

Microbiological efficacy and skin tolerance of commonly used nonantiseptic inpatient bathing practices in non-ICU settings: A systematic review.

BACKGROUND: Nonantiseptic bathing practices among inpatients and residents of nursing homes vary in terms of frequency, bathing type and product. We performed a systematic review to compare the efficacy of different bathing practices in reducing skin colonization, health care-associated infections (HAI) or their impact on skin integrity. METHODS: We searched Medline and Embase up until February 2018 testing a combination of terms for 3 concepts: (1) personal hygiene, (2) inpatients, (3) skin colonization, integrity or HAIs. Studies set in ICUs or including children were excluded. This review was registered in PROSPERO: CRD42018091639. RESULTS: Seven studies were included. No statistically significant impact in terms of reduced skin colonization was described irrespective of bathing product, type or frequency except for a reduced burden of C difficile on the skin of infected patients after showering compared to bathing. One study addressing impact on HAI did not detect a significant difference when a waterless no-rinse product was used. Integrity of the skin was better preserved by no-rinse products. CONCLUSIONS: No study described a statistically significant reduction of bacterial skin colonization or incidence of HAI after bathing hospitalized patients with nonantiseptic products. However, waterless no-rinse products were associated with less skin damage in most studies.

Factors determining the adherence to antimicrobial guidelines and the adoption of computerised decision support systems by physicians: A qualitative study in three European hospitals.

BACKGROUND AND OBJECTIVES: Antimicrobial stewardship (AMS) programs aim to optimize antibiotic use and reduce inappropriate prescriptions through a panel of interventions. The implementation of clinical guidelines is a core strategy of AMS programs. Nevertheless, their dissemination and application remain low. Computerised decision support systems (CDSSs) offer new opportunities for semi-automated dissemination of guidelines. This qualitative study aimed at gaining an in-depth understanding of the determinants of adherence to antimicrobial prescribing guidelines and CDSSs adoption and is part of a larger project, the COMPASS trial, which aims to assess a CDSS for antimicrobial prescription. The final objective of this qualitative study is to 1) provide insights from end-users to assist in the design of the COMPASS CDSS, and to 2) help with the interpretation of the quantitative findings of the randomised controlled trial assessing the COMPASS CDSS, once data will be analysed. METHODS: We conducted semi-structured individual interviews among in-hospital physicians in two hospitals in Switzerland and one hospital in France. Physicians were recruited by convenience sampling and snowballing until data saturation was achieved. RESULTS: Twenty-nine physicians were interviewed. We identified three themes related to the potential barriers to guideline adherence: 1) insufficient clarity, accessibility and applicability of guidelines, 2) need of critical thinking skills to adhere to guidelines and 3) impact of the team prescribing process and peers on physicians in training. As to the perception of CDSSs, we identified four themes that could affect their adoption: 1) CDSSs are perceived as time-consuming, 2) CDSSs could reduce physicians' critical thinking and professional autonomy and raise new medico-legal issues, 3) effective CDSSs would require specific features, such as ease of use and speed, which affect usability and 4) CDSSs could improve physicians' adherence to guidelines and patient care. DISCUSSION: CDSSs have the potential to overcome several barriers for adherence to guidelines by improving accessibility and providing individualised recommendations backed by patient data. When designing CDSSs, mixed clinical and information technology teams should focus on user-friendliness, ergonomics, workflow integration and transparency of the decision-making process.

Impact of extended use and decontamination with vaporized hydrogen peroxide on N95 respirator fit.

BACKGROUND: To address the shortage of N95 respirators in the wake of the COVID-19 pandemic, some organizations have recommended the decontamination of respirators using vaporized hydrogen peroxide (VHP) sterilizer for up to 10 times. However, these recommendations are based on studies that did not take into account the extended use of respirators, which can degrade respirator fit. METHODS: We investigated the impact of extended use and decontamination with VHP on N95 Respirator Fit. We performed a prospective cohort study to determine the number of times respirators can be decontaminated before respirator fit test failure. The primary outcome was the overall number of cycles required for half of the respirators to fail (either mechanical failure or fit test failure). RESULTS: Thirty-six participants completed 360 hours of respirator usage across 90 cycles. The median number of cycles completed by participants before respirator failure was 2. The overall number of cycles required for half of respirators to fail was 1, 3, 5, and 4 for the 3M 1860(S), 3M 1870+, Moldex 151X and ProGear 88020 respirators, respectively. CONCLUSIONS: The combination of prolonged usage and VHP decontamination was associated with early failure. Decontamination and prolonged usage of respirators must be done cautiously.

Increased Community-Associated Clostridioides difficile Infections in Quebec, Canada, 2008-20151.

The annual incidence rate of community-associated Clostridioides difficile infections in Quebec, Canada, has increased by 33.3%, from 0.51 (2008) to 0.68 (2015) cases/100,000 population, while incidence of healthcare-associated cases remained relatively stable. Possible causes include increased disease severity, increased antimicrobial drug use, emergence of virulent strains, and heightened physician awareness.

Selective reporting of antibiotic susceptibility testing results: a promising antibiotic stewardship tool.

Introduction: Selective reporting of antibiotic susceptibility testing (AST) results is a potentially interesting tool for antibiotic stewardship. It consists of performing AST according to usual practices, but the results are reported to the prescriber only for a few antibiotics (i.e. first-line agents) or not reported at all when colonization is likely.Areas covered: We retrieved 20 studies exploring the impact of selective reporting. Overall, selective reporting is able to influence antibiotic use, both discouraging prescription in case of colonization, and promoting the selection of narrow-spectrum agents. Most studies concerned urine samples. Evidence on the impact on antibiotic resistance is insufficient. Unintended consequences were not observed, but evidence on this topic is scarce. Selective reporting is well implemented in a few countries, and a huge heterogeneity of practices exists.Expert opinion: Evidence shows that selective reporting can help reducing inappropriate and unnecessary antibiotic prescriptions. Uncomplicated urinary tract infections are probably the best initial target, both in hospital and community settings, but other non-severe infections can be a suitable option. The implementation of selective reporting should be promoted by the scientific community, with detailed practical guidelines, and its impact should be further assessed in large interventional studies.

Antimicrobial resistance trends in Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis urinary isolates from Switzerland: retrospective analysis of data from a national surveillance network over an 8-year period (2009-2016).

  OBJECTIVES: Most urinary tract infections (UTIs) are treated empirically with antibiotics, making comprehensive resistance surveillance data essential to guide empiric regimens. We describe trends in the antibiotic resistance of urinary Enterobacteriaceae isolates in Switzerland between 2009 and 2016. METHODS: We analysed data from routinely collected Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis urinary samples from community and hospital settings in Switzerland. The data were collected by ANRESIS, the national laboratory-based antimicrobial resistance surveillance system. Our analyses focused on resistance to antibiotics commonly prescribed for UTIs for the period 2009–2016. Only the first isolate per patient per year was included. RESULTS: 297,200 urinary samples were included in the analysis, of which 246,656 (83.0%) were E. coli isolates. Overall, E. coli showed high susceptibility to 3rd/4th-generation cephalosporins, nitrofurantoin and fosfomycin, with the annual proportions of resistant isolates <6%, <5% and <2%, respectively, for all study years. Resistance to fluoroquinolones was >14% and increased over time (from 14.5% in 2009 to 19.3% in 2016). Resistance to cotrimoxazole was >20% for the whole study period. K. pneumoniae (n = 32,757; 11.0%) showed low resistance to cotrimoxazole and quinolones (<11% and <12%, respectively), while for P. mirabilis (n = 17,787; 6.0%) the proportion of resistant isolates was <35% for cotrimoxazole and <18% for quinolones. Even though quinolone resistance remained low for both pathogens (<12% for K. pneumoniae and <18% for P. mirabilis), it increased significantly over time. Proportions of isolates resistant to 3rd/4th generation cephalosporins remained low (<5% for K. pneumoniae and <2% for P. mirabilis), but in the case of K. pneumoniae they increased over time. CONCLUSIONS: Swiss surveillance data confirm that resistance among uropathogenic E. coli isolates to nitrofurantoin and fosfomycin remains low. While resistance to 3rd/4th-generation cephalosporins also remains relatively low, it has been increasing and needs further surveillance. As for K. pneumoniae and P. mirabilis, high levels of susceptibility to 3rd-generation cephalosporins and quinolones were confirmed, while high prevalences of resistance to nitrofurantoin and fosfomycin discourage their use as first-line therapies for these pathogens.  .

Control of Carbapenem-resistant Enterobacteriaceae, Acinetobacter baumannii, and Pseudomonas aeruginosa in Healthcare Facilities: A Systematic Review and Reanalysis of Quasi-experimental Studies.

Carbapenem-resistant Enterobacteriaceae (CRE), Acinetobacter baumannii (CRAB), and Pseudomonas aeruginosa (CRPsA) are a serious cause of healthcare-associated infections, although the evidence for their control remains uncertain. We conducted a systematic review and reanalysis to assess infection prevention and control (IPC) interventions on CRE-CRAB-CRPsA in inpatient healthcare facilities to inform World Health Organization guidelines. Six major databases and conference abstracts were searched. Before-and-after studies were reanalyzed as interrupted time series if possible. Effective practice and organization of care (EPOC) quality criteria were used. Seventy-six studies were identified, of which 17 (22%) were EPOC-compatible and interrupted time series analyses, assessing CRE (n = 11; 65%), CRAB (n = 5; 29%) and CRPsA (n = 3; 18%). IPC measures were often implemented using a multimodal approach (CRE: 10/11; CRAB: 4/5; CRPsA: 3/3). Among all CRE-CRAB-CRPsA EPOC studies, the most frequent intervention components included contact precautions (90%), active surveillance cultures (80%), monitoring, audit and feedback of measures (80%), patient isolation or cohorting (70%), hand hygiene (50%), and environmental cleaning (40%); nearly all studies with these interventions reported a significant reduction in slope and/or level. The quality of EPOC studies was very low to low.

Ensuring Antibiotic Development, Equitable Availability, and Responsible Use of Effective Antibiotics: Recommendations for Multisectoral Action.

Antibiotic resistance is a growing threat to global public health. The World Health Organization's Global Action Plan on Antimicrobial Resistance recommends engaging multisectoral stakeholders to tackle the issue. However, so far, few studies have addressed barriers to antibiotic development, equitable availability, and responsible antibiotic use from the perspective of stakeholders outside healthcare facilities or patient communities: the so-called third-party stakeholders. Third-party stakeholders include, inter alia, governments, regulatory agencies, and professionals working in antibiotic research and development and medical ethics. This viewpoint provides an overview of barriers to antibiotic development, equitable availability of effective antibiotics, and the responsible use of antibiotics. The barriers were identified in an exploratory, qualitative interview study with an illustrative sample of 12 third-party stakeholders. Recommendations to lift these barriers are presented, together with examples of recently-made progress. The recommendations should guide future antibiotic policies and multisectoral policy action.

Quality indicators assessing antibiotic use in the outpatient setting: a systematic review followed by an international multidisciplinary consensus procedure.

Objectives: Quality indicators (QIs) assessing the appropriateness of antibiotic use are essential to identify targets for improvement and guide antibiotic stewardship interventions. The aim of this study was to develop a set of QIs for the outpatient setting from a global perspective. Methods: A systematic literature review was performed by searching MEDLINE and relevant web sites in order to retrieve a list of QIs. These indicators were extracted from published trials, guidelines, literature reviews or consensus procedures. This evidence-based set of QIs was evaluated by a multidisciplinary, international group of stakeholders using a RAND-modified Delphi procedure, using two online questionnaires and a face-to-face meeting between them. Stakeholders appraised the QIs' relevance using a nine-point Likert scale. This work is part of the DRIVE-AB project. Results: The systematic literature review identified 43 unique QIs, from 54 studies and seven web sites. Twenty-five stakeholders from 14 countries participated in the consensus procedure. Ultimately, 32 QIs were retained, with a high level of agreement. The set of QIs included structure, process and outcome indicators, targeting both high- and middle- to low-income settings. Most indicators focused on general practice, addressing the common indications for antibiotic use in the community (particularly urinary and respiratory tract infections), and the organization of healthcare facilities. Twelve indicators specifically addressed outpatient parenteral antimicrobial therapy (OPAT). Conclusions: We identified a set of 32 outpatient QIs to measure the appropriateness of antibiotic use. These QIs can be used to identify targets for improvement and to evaluate the effects of antibiotic stewardship interventions.

Metrics to assess the quantity of antibiotic use in the outpatient setting: a systematic review followed by an international multidisciplinary consensus procedure.

Background: The international Innovative Medicines Initiative (IMI) project DRIVE-AB (Driving Reinvestment in Research and Development and Responsible Antibiotic Use) aims to develop a global definition of 'responsible' antibiotic use. Objectives: To identify consensually validated quantity metrics for antibiotic use in the outpatient setting. Methods: First, outpatient quantity metrics (OQMs) were identified by a systematic search of literature and web sites published until 12 December 2014. Identified OQMs were evaluated by a multidisciplinary, international stakeholder panel using a RAND-modified Delphi procedure. Two online questionnaires and a face-to-face meeting between them were conducted to assess OQM relevance for measuring the quantity of antibiotic use on a nine-point Likert scale, to add comments or to propose new metrics. Results: A total of 597 articles were screened, 177 studies met criteria for full-text screening and 138 were finally included. Twenty different OQMs were identified and appraised by 23 stakeholders. During the first survey, 14 OQMs were excluded and 6 qualified for discussion. During the face-to-face meeting, 10 stakeholders retained five OQMs and suggestions were made considering context and combination of metrics. The final set of metrics included defined daily doses, treatments/courses and prescriptions per defined population, treatments/courses and prescriptions per defined number of physician contacts and seasonal variation of total antibiotic use. Conclusions: A small set of consensually validated metrics to assess the quantity of antibiotic use in the outpatient setting was obtained, enabling (inter)national comparisons. The OQMs will help build a global conceptual framework for responsible antibiotic use.

Quality indicators for responsible antibiotic use in the inpatient setting: a systematic review followed by an international multidisciplinary consensus procedure.

Background: This study was conducted as part of the Driving Reinvestment in Research and Development and Responsible Antibiotic Use (DRIVE-AB) project and aimed to develop generic quality indicators (QIs) for responsible antibiotic use in the inpatient setting. Methods: A RAND-modified Delphi method was applied. First, QIs were identified by a systematic review. A complementary search was performed on web sites of relevant organizations. Duplicates were removed and disease and patient-specific QIs were combined into generic indicators. The relevance of these QIs was appraised by a multidisciplinary international stakeholder panel through two questionnaires and an in-between consensus meeting. Results: The systematic review retrieved 70 potential generic QIs. The QIs were appraised by 25 international stakeholders with diverse backgrounds (medical community, public health, patients, antibiotic research and development, regulators, governments). Ultimately, 51 QIs were selected in consensus. QIs with the highest relevance score included: (i) an antibiotic plan should be documented in the medical record at the start of the antibiotic treatment; (ii) the results of bacteriological susceptibility testing should be documented in the medical record; (iii) the local guidelines should correspond to the national guidelines but should be adapted based on local resistance patterns; (iv) an antibiotic stewardship programme should be in place at the healthcare facility; and (v) allergy status should be taken into account when antibiotics are prescribed. Conclusions: This systematic and stepwise method combining evidence from literature and stakeholder opinion led to multidisciplinary international consensus on generic inpatient QIs that can be used globally to assess the quality of antibiotic use.

Variation in antibiotic use among and within different settings: a systematic review.

Objectives: Variation in antibiotic use may reflect inappropriate use. We aimed to systematically describe the variation in measures for antibiotic use among settings or providers. This study was conducted as part of the innovative medicines initiative (IMI)-funded international project DRIVE-AB. Methods: We searched for studies published in MEDLINE from January 2004 to January 2015 reporting variation in measures for systemic antibiotic use (e.g. DDDs) in inpatient and outpatient settings. The ratio between a study's reported maximum and minimum values of a given measure [maximum:minimum ratio (MMR)] was calculated as a measure of variation. Similar measures were grouped into categories and when possible the overall median ratio and IQR were calculated. Results: One hundred and forty-three studies were included, of which 85 (59.4%) were conducted in Europe and 12 (8.4%) in low- to middle-income countries. Most studies described the variation in the quantity of antibiotic use in the inpatient setting (81/143, 56.6%), especially among hospitals (41/81, 50.6%). The most frequent measure was DDDs with different denominators, reported in 23/81 (28.4%) inpatient studies and in 28/62 (45.2%) outpatient studies. For this measure, we found a median MMR of 3.7 (IQR 2.6-5.0) in 4 studies reporting antibiotic use in ICUs in DDDs/1000 patient-days and a median MMR of 2.3 (IQR 1.5-3.2) in 18 studies reporting outpatient antibiotic use in DDDs/1000 inhabitant-days. Substantial variation was also identified in other measures. Conclusions: Our review confirms the large variation in antibiotic use even across similar settings and providers. Data from low- and middle-income countries are under-represented. Further studies should try to better elucidate reasons for the observed variation to facilitate interventions that reduce unwarranted practice variation. In addition, the heterogeneity of reported measures clearly shows that there is need for standardization.

Metrics for quantifying antibiotic use in the hospital setting: results from a systematic review and international multidisciplinary consensus procedure.

Background: Quantifying antibiotic use is an essential element of antibiotic stewardship since it allows comparison between different settings and time windows, and measurement of the impact of interventions. However, quantity metrics (QMs) and methods have not been standardized. Objectives: To propose a set of QMs for antibiotic use in inpatients (IQMs) that are accepted globally by professionals in a range of disciplines. The study was conducted within the Driving Reinvestment in Research and Development and Responsible Antibiotic Use (DRIVE-AB) project. Methods: A systematic literature review using MEDLINE identified articles on measuring inpatient antibiotic use, published up to 29 January 2015. A consensually selected list of national and international web sites was screened for additional IQMs. IQMs were classified according to the type of numerator used and presented to a multidisciplinary panel of stakeholders. A RAND-modified Delphi consensus procedure, which consisted of two online questionnaires and a face-to-face meeting, was performed. Results: The systematic literature review and web site search identified 168 eligible articles from which an initial list of 20 IQMs, composed of 20 different numerators and associated denominators was developed. The consensus procedure resulted in a final set of 12 IQMs. Among this final set, DDDs per 100(0) patient-days and days of therapy per patient-days were most frequently found in the review. The panel recommended that antibiotic use should be expressed in at least two metrics simultaneously. Conclusions: Our consensus procedure identified a set of IQMs that we propose as an evidence-based global standard.

Dolutegravir maintains a durable effect against HIV replication in tissue culture even after drug washout.

OBJECTIVES: Of the currently approved HIV integrase strand transfer inhibitors (INSTIs), dolutegravir has shown greater efficacy than raltegravir at suppressing HIV-1 replication in treatment-experienced individuals. Biochemical experiments have also shown that dolutegravir has a longer dissociative half-life when bound to HIV integrase than does raltegravir. In order to study the intracellular efficacy of various INSTIs, we asked whether drug removal from INSTI-treated HIV-1-infected cells would result in different times to viral rebound. In addition, we assessed the role of the R263K substitution within the integrase ORF that is associated with low-level resistance to dolutegravir. METHODS: HIV-infected MT-2 cells were treated with dolutegravir, raltegravir or a third experimental INSTI (MK-2048) and the drugs were washed out after varying times. Viral replication was monitored by measuring reverse transcriptase (RT) activity in the culture fluids. RESULTS: We observed a significantly slower increase in RT activity after the removal of dolutegravir compared with raltegravir or MK-2048. The incubation time before the drug was removed also had an impact on the level of RT activity independently of the drug and virus used. The R263K substitution did not significantly impact on levels of RT activity after drug washout, suggesting that dolutegravir remained tightly bound to the integrase enzyme despite the presence of this mutation. CONCLUSIONS: These results suggest that the residency time of INSTIs on integrase is a key factor in the activity of these drugs and that the anti-HIV activity of dolutegravir persists more effectively than that of other INSTIs after drug washout.