BackgroundVietnam has high rates of antimicrobial resistance (AMR) but limited genomic surveillance, impeding our ability to assess transmission dynamics. This study aimed to use whole genome ssequencing (WGS) to examine the transmission of key AMR pathogens in two intensive care units in Hanoi, Vietnam.MethodsA prospective surveillance study of all adults admitted to two intensive care units (ICUs) at the National Hospital for Tropical Diseases (NHTD) and Bach Mai Hospital (BMH) was conducted between June 2017 and January 2018. Clinical and environmental samples were cultured on selective media, characterised using MALDI TOF MS, and Illumina sequenced. Phylogenies based on the de novo assemblies (SPAdes) were constructed using Mafft (PARsnp), Gubbins and RAxML. Resistance genes were detected using Abricate against the NCBI database.Findings3,153 Escherichia coli, Klebsiella pneumoniae and Acinetobacter baumannii isolates from 369 patients were analysed. Phylogenetic analysis revealed predominant lineages within A. baumannii (global clone [GC]2, sequence types [ST]2, ST571) and K. pneumoniae (ST15, ST16, ST656, ST11, ST147) isolates. Colonisation was most common with E. coli (88.9%) followed by K. pneumoniae (62.4%). 91% of E. coli carried a blaCTX-M variant, while 81% of K. pneumoniae isolates carried blaNDM (54%) and/or blaKPC (45%). Transmission analysis using single nucleotide polymorphisms (SNPs) identified 167 clusters involving 251 (68%) patients, in some cases involving patients from both ICUs. There were no significant differences between the lineages or AMR genes recovered between the two ICUs.InterpretationThis study represents the largest prospective surveillance study of key AMR pathogens in Vietnamese ICUs. Clusters of closely related isolates in patients across both ICUs suggests recent transmission prior to ICU admission in other healthcare settings or in the community.FundingThis work was funded by the Medical Research Council Newton Fund, United Kingdom; the Ministry of Science and Technology, Vietnam (HNQT/SPÐP/04.16) and the Wellcome Trust, United Kingdom.Research in contextEvidence before this studyGlobally, antimicrobial resistance (AMR) is projected to cause 10 million deaths annually by 2050. While 90% of these deaths are expected to occur in African and Asian low- and middle-income countries (LMIC), attributing morbidity and mortality is difficult without the availability of comprehensive AMR data in these settings. Whilst efforts have been made to improve AMR surveillance in these settings, this is often hampered by limited infrastructure, training and financial resources.Added value of this studyThis is the largest prospective surveillance study of three key AMR pathogens (E. coli, K. pneumoniae and A. baumannii) conducted in critical care settings in Vietnam. All patients were colonised or infected with one or more extended spectrum beta-lactamase (ESBL) producing and/or carbapenem-resistant organism. Colonisation with more than one organism was very common, with resistant E. coli predominantly isolated from stool. A small number of predominant lineages were identified for K. pneumoniae and A. baumannii, while the E. coli isolates were highly genetically diverse. A large number of genomic clusters were identified within the two ICUs, some of which spanned both ICUs. There were no significant differences between lineages or AMR genes between the two ICUs.Implications of all the available evidenceThis study found high rates of colonisation and infection with three key AMR pathogens in adults admitted to two Vietnamese ICUs. Whilst transmission was common within ICUs the finding of similar lineages and AMR genes in both ICUs suggests that dissemination of AMR occurs prior to ICU admission, from either referral sites or in community settings prior to hospital admission. Strategies to tackle AMR in Vietnam will need to account for this by extending surveillance beyond ICU to hospital and community settings.