Investigation of the First Case of New Delhi Metallo-β-Lactamase-1–Producing Pseudomonas aeruginosa in Texas

Abstract

Background: New Delhi metallo-β-lactamases impart resistance to carbapenems. Enterobacteriaceae carrying New Delhi metallo-β-lactamases have been reported before. However, only 7 cases of blaNDM-carrying Pseudomonas aeruginosa has been reported from 4 states in the United States as of January 1, 2018, according to the CDC. We describe an epidemiologic investigation of the first reported case of blaNDM-carrying Pseudomonas aeruginosa in Texas and the measures that controlled the spread of the organisms carrying this gene at a 30-bed spinal cord injury unit (SCI) and the acute-care hospital within the Veterans’ Affairs North Texas Health Care System. Methods: After identification of blaNDM-1–carrying P. aeruginosa from a urine culture in an SCI patient who received medical treatment in Thailand prior to transfer, we performed a rectal screen for the presence of blaNDM in the index patient’s hospital roommates. Based on the results, we expanded the investigation to other patient care units that had provided care to the patient. We initiated universal contact isolation precautions, 1:1 nursing care, restricted movement, phased point-prevalence testing, and intense environmental cleaning until the threat of blaNDM was mitigated. Whole-genome sequencing (WGS) was performed on clinical isolates from the index patient and the roommates by the CDC. Results: Of the 2 roommates of the index, 1 patient had a urine culture positive for blaNDM-5-carrying Escherichia coli. The second roommate has subsequently grown blaNDM-1-carrying P. aeruginosa from a clinical culture. A third patient who was in the same unit as the index patient but not in the same room in an acute-care unit tested positive for blaNDM in a rectal screen. Of the 54 patients who were hospitalized in the same unit as the index patient, 26 refused to get the test and 28 tested negative. In addition, point-prevalence rectal screening was conducted in the SCI in 3 phases that were 3 to 4 weeks apart. All of these screening tests were negative. WGS revealed that the index patient and roommate 2 had blaNDM-1–carrying P. aeruginosa, whereas the roommate 1 had blaNDM-5–carrying E. coli. No further spread occurred. Conclusions: Our aggressive efforts quickly mitigated further spread of blaNDM. Our epidemiologic investigation indicates that an intergenus transfer of blaNDM from P. aeruginosa to E. coli likely took place. In addition, it appears there was an evolution of NDM-1 to NDM-5, which differs from the former by 2 amino acid substitutions at positions 88 (Val→Leu) and 154 (Met→Leu). This type of evolution has been shown by prior studies to confer increased antibiotic resistance in certain resource limited settings.Funding: NoneDisclosures: None