Prevalence and evolution of transmitted HIV drug resistance in Belgium between 2013 and 2019

Abstract Background To assess the prevalence and evolution of transmitted drug resistance (TDR) in Belgium a total of 3708 baseline HIV-1 polymerase sequences from patients diagnosed between 2013 and 2019 were analysed. Methods Protease and reverse transcriptase HIV-1 sequences were collected from the seven national Aids Reference Laboratories (ARL). Subtype determination and drug resistance scoring were performed using the Stanford HIV Drug Resistance Database. Trends over time were assessed using linear regression and the maximum likelihood approach was used for phylogenetic analysis. Results 17.9% of the patients showed evidence of TDR resulting in at least low level resistance to one drug (Stanford score ≥ 15). If only the high-level mutations (Stanford score ≥ 60) were considered, TDR prevalence dropped to 6.3%. The majority of observed resistance mutations impacted the sensitivity for NNRTI (11.4%), followed by NRTI (6.2%) and PI (2.4%). Multi-class resistance was observed in 2.4%. Clustered onward transmission was evidenced for 257 of 635 patients (40.5%), spread over 25 phylogenetic clusters. Conclusions The TDR prevalence remained stable between 2013 and 2019 and is comparable to the prevalence in other Western-European countries. The high frequency of NNRTI mutations requires special attention and follow-up. Phylogenetic analysis provided evidence for local clustered onward transmission of some frequently detected mutations.