New Delhi metallo-β-lactamases (NDMs) are major contributors to the spread of carbapenem resistance globally. In Australia, NDMs were previously associated with international travel, but from 2019 we noted increasing incidence of NDM-positive clinical isolates. We investigated the clinical and genomic epidemiology of NDM carriage at a tertiary-care Australian hospital from 2016 to 2021.

We identified 49 patients with 84 NDM-carrying isolates in an institutional database, and we collected clinical data from electronic medical record. Short- and long-read whole genome sequencing was performed on all isolates. Completed genome assemblies were used to assess the genetic setting of blaNDM genes and to compare NDM plasmids.

Of 49 patients, 38 (78%) were identified in 2019–2021 and only 11 (29%) of 38 reported prior travel, compared with 9 (82%) of 11 in 2016–2018 (P = .037). In patients with NDM infection, the crude 7-day mortality rate was 0% and the 30-day mortality rate was 14% (2 of 14 patients). NDMs were noted in 41 bacterial strains (ie, species and sequence type combinations). Across 13 plasmid groups, 4 NDM variants were detected: blaNDM-1, blaNDM-4, blaNDM-5, and blaNDM-7. We noted a change from a diverse NDM plasmid repertoire in 2016–2018 to the emergence of conserved blaNDM-1 IncN and blaNDM-7 IncX3 epidemic plasmids, with interstrain spread in 2019–2021. These plasmids were noted in 19 (50%) of 38 patients and 35 (51%) of 68 genomes in 2019–2021.

Increased NDM case numbers were due to local circulation of 2 epidemic plasmids with extensive interstrain transfer. Our findings underscore the challenges of outbreak detection when horizontal transmission of plasmids is the primary mode of spread.

To evaluate the impact of serial interventions on the incidence of methicillin-resistant Staphylococcus aureus (MRSA).

Longitudinal observational study before and after interventions.

The Alfred Hospital is a 350-bed tertiary referral hospital with a 35-bed intensive care unit (ICU).

A series of interventions including the introduction of an antimicrobial hand-hygiene gel to the intensive care unit and a hospitalwide MRSA surveillance feedback program that used statistical process control charts but not active surveillance cultures.

Serial interventions were introduced between January 2003 and May 2006. The incidence and rates of new patients colonized or infected with MRSA and episodes of MRSA bacteremia in the intensive care unit and hospitalwide were compared between the preintervention and intervention periods. Segmented regression analysis was used to calculate the percentage reduction in new patients with MRSA and in episodes of MRSA bacteremia hospitalwide in the intervention period.

The rate of new patients with MRSA in the ICU was 6.7 cases per 100 patient admissions in the intervention period, compared with 9.3 cases per 100 patient admissions in the preintervention period (P = .047). The hospitalwide rate of new patients with MRSA was 1.7 cases per 100 patient admissions in the intervention period, compared with 3.0 cases per 100 patient admissions in the preintervention period (P < .001). By use of segmented regression analysis, the maximum and conservative estimates for percentage reduction in the rate of new patients with MRSA were 79.5% and 42.0%, respectively, and the maximum and conservative estimates for percentage reduction in the rate of episodes of MRSA bacteremia were 87.4% and 39.0%, respectively.

A sustained reduction in the number of new patients with MRSA colonization or infection has been demonstrated using minimal resources and a limited number of interventions.