Clinical presentation and outcomes of bloodstream infection with intrinsically carbapenem-resistant non-fermenting gram-negative organisms: Stenotrophomonas maltophilia, Elizabethkingia spp. and Chryseobacterium spp. in Singapore, from 2012 to 2024.

Background: Bloodstream infections with the non-fermenting Gram-negative organisms Stenotrophomonas maltophilia, Elizabethkingia spp. or Chryseobacterium spp. are observed in nosocomial settings. Comparative description of their clinical presentation, microbiological characteristics, treatment options and outcomes remain to be investigated.

Methods: We performed a retrospective single-centre analysis of bloodstream infections with the abovementioned three organisms from 1 Jan 2012 to 30 Jun 2024.

Results: A total of 349 distinct encounters (from 322 unique patients) were identified with bacteraemia. Stenotrophomonas maltophilia was the commonest (197/349, 56.4%), followed by Elizabethkingia spp. (127/349, 36.4%) and Chryseobacterium spp. (25/349, 7.2%). Prior carbapenem exposure was observed in 59.9% of cases. The majority were related to central lines (58.2%). Most cases were nosocomial in onset (82.5%), and a third were from the intensive care unit (32.1%). A significant proportion of our Stenotrophomonas maltophilia (32.8%) and Chryseobacterium spp. (22.7%) isolates were resistant to levofloxacin, while a majority of the organisms retained susceptibility to trimethoprim-sulfamethoxazole (TMP-SMX) and minocycline. Dual antibiotics were used in a minority of encounters (23/349, 6.6%). Mortality was high across infections with the three organisms, but highest amongst those with Stenotrophomonas maltophilia bacteraemia (41.6%), followed by Elizabethkingia spp. (29.9%) and Chryseobacterium spp. (20.0%).

Conclusions: Stenotrophomonas, Elizabethkingia or Chryseobacterium spp bacteraemia was associated with significant mortality. Most cases were nosocomial in acquisition, with prior carbapenem exposure or indwelling central catheters. Fluoroquinolone resistance was common for Stenotrophomonas maltophilia and Chryseobacterium spp., but less prevalent in Elizabethkingia spp., while TMP-SMX and minocycline retained susceptibility. Monitoring these trends would be critical in guiding empiric therapy for these organisms.