Outbreak of New Delhi metallo-β-lactamase carbapenemase-producing Pseudomonas aeruginosa infections in a Southern California hospital

Jacob M Garrigues; Hannah K Gray; Ricardo P Ison; Daniel Z Uslan; Amorce Lima; Shekina Gonzalez-Ferrer; Marisol Trejo; Ran Zhuo; Colette J Matysiak Match; Erlinda R Ulloa; Sandeep Bhaurla; Vanessa Lewis; Urvashi Parti; Tessa Sandoval; Sebora Turay; Shaunté Walton; Kavitha Prabaker; Omai B Garner; Sukantha Chandrasekaran; Nicole M Green; Shangxin Yang

doi:10.1016/j.ajic.2025.06.005

Outbreak of New Delhi metallo-β-lactamase carbapenemase-producing Pseudomonas aeruginosa infections in a Southern California hospital

Am J Infect Control. 2025 Jun 13:S0196-6553(25)00416-X. doi: 10.1016/j.ajic.2025.06.005. Online ahead of print.

Authors

Jacob M Garrigues¹, Hannah K Gray², Ricardo P Ison³, Daniel Z Uslan⁴, Amorce Lima², Shekina Gonzalez-Ferrer², Marisol Trejo², Ran Zhuo², Colette J Matysiak Match², Erlinda R Ulloa⁵, Sandeep Bhaurla⁶, Vanessa Lewis³, Urvashi Parti³, Tessa Sandoval³, Sebora Turay³, Shaunté Walton³, Kavitha Prabaker⁴, Omai B Garner², Sukantha Chandrasekaran², Nicole M Green⁷, Shangxin Yang⁸

Affiliations

¹ Public Health Laboratories, County of Los Angeles Department of Public Health, Downey, CA.
² Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA.
³ Clinical Epidemiology & Infection Prevention, UCLA Health, Los Angeles, CA.
⁴ Clinical Epidemiology & Infection Prevention, UCLA Health, Los Angeles, CA; Division of Infectious Diseases, David Geffen School of Medicine, University of California, Los Angeles, CA.
⁵ Division of Infectious Diseases, Children's Hospital of Orange County, Orange, CA; Department of Pediatrics, University of California Irvine School of Medicine, Irvine, CA.
⁶ Acute Communicable Disease Control, County of Los Angeles Department of Public Health, Los Angeles, CA.
⁷ Public Health Laboratories, County of Los Angeles Department of Public Health, Downey, CA. Electronic address: nicgreen@ph.lacounty.gov.
⁸ Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA. Electronic address: shangxinyang@mednet.ucla.edu.

PMID: 40518051
DOI: 10.1016/j.ajic.2025.06.005

Abstract

Background: Carbapenemase-producing carbapenem-resistant Pseudomonas aeruginosa (CP-CRPA) is a major public health threat due to limited treatment options and high transmissibility. Though widespread globally, few instances of locally transmitted New Delhi metallo-β-lactamase (NDM)-producing CP-CRPA have been documented in the United States. Here, a cluster of locally transmitted NDM-1 CP-CRPA infections in Southern California is reported.

Methods: Epidemiologic investigations involving both patient screening and environmental surveillance by microbiological culture, carbapenemase testing, and bacterial whole-genome sequencing were conducted.

Results: Through extensive epidemiologic investigations, a sink environmental reservoir was identified. A genetically unique strain of NDM-CRPA was identified to be transmitted among seven patients in a single hospital over the course of 1.5 years. Changes in antimicrobial resistance genes harbored by a mobile genetic element were identified between the index and later cases, and the gene encoding NDM-1 resided within a mobile genetic element on the chromosome displaying evidence of widespread transmission between different species. Several interventions were implemented, including sink P-trap replacement and disinfectant against Pseudomonas biofilms. No additional cases were identified after the interventions.

Conclusions: Implementation of real-time pathogen surveillance enabled effective response to an ongoing outbreak that involved environmental sampling, microbiological testing, whole-genome sequencing, facility management, and updated infection prevention policies.

Keywords: Genomic surveillance; NDM; P-trap; Sink; Whole-genome sequencing.