Outpatient Clonal Propagation and Rapid Regional Establishment of an Emergent Carbapenem-Resistant Acinetobacter baumannnii Lineage Sequence Type 499Pas

Eliminating carbapenem-resistant Acinetobacter baumannii (CRAb) disease requires comprehensive knowledge of how this noncommensal organism propagates among at-risk hosts. We molecularly characterized an ongoing surge of CRAb cases among patients in a Midwest US healthcare system, which coincided with sustained reductions in hospital-acquired CRAb infections and falloffs of cases associated with distinctly more resistant antibiotypes. Genome sequencing revealed surge isolates belonged to an emergent Pasteur scheme sequence type 499 and comprised multiple contemporaneous clonal clusters. Detailed query of health records revealed no consistent hospital source but instead identified various outpatient healthcare settings linked to cluster cases. We show that CRAb can rapidly establish a regional presence even without gains in breadth of antibiotic resistance and negligible contribution from sustained intrahospital transmission. As CRAb lineages may sidestep control efforts via outpatient epidemiological niches, our approach can be implemented to investigate outpatient CRAb propagation and inform subsequent local surveillance outside hospital settings.

Comparison of the Clinical Characteristics of Hospital-Acquired and Non-Hospital-Acquired Acinetobacter calcoaceticus-baumannii Complex in a Large Midwest US Health Care System

We retrospectively compared the clinical characteristics of hospital-acquired (HA) vs non-hospital-acquired (nHA) Acinetobacter calcoaceticus-baumannii complex isolates in a large health care system in St. Louis, Missouri, from 2007 to 2017. More than 60% of the total isolates were nHA; they were predominantly from nonrespiratory sources and exhibited ~40% carbapenem resistance rates and stably persisted, though HA occurrence waned.

Seasonal Changes in the Prevalence of Antibiotic-Susceptible Acinetobacter calcoaceticus-baumannii Complex Isolates Result in Increased Multidrug Resistance Rates During Winter Months

Temporal analysis of Acinetobacter calcoaceticus-baumannii complex isolates in a large, US healthcare system demonstrated decreased occurrence of antibiotic-susceptible isolates between November and May, while resistant isolate occurrence was temporally stable. This resulted in 50%–100% seasonal increases of resistance rates. This work offers insight into the phenomenon of Gram-negative pathogen seasonality.