# Molecular epidemiology and antimicrobial resistance profiles of Pseudomonas aeruginosa causing bloodstream infections in neutropenic cancer patients

## TL;DR

This study examines Pseudomonas aeruginosa bloodstream infections in cancer patients with weakened immune systems, focusing on genetic diversity, drug resistance, and factors affecting mortality.

## Contribution

The study identifies ST175 as a dominant high-risk Pseudomonas aeruginosa clone and links specific clinical factors to early mortality in neutropenic cancer patients.

## Key findings

- ST175 was the most prevalent Pseudomonas aeruginosa clone, associated with antimicrobial resistance.
- ExoU toxin was present in 24.4% of strains, linked to serotype O11 and ST253.
- Inadequate antibiotic therapy and septic shock significantly increased 7-day mortality.

## Abstract

Bloodstream infections (BSI) in neutropenic cancer patients, particularly those caused by Pseudomonas aeruginosa (PA), are associated with high morbidity and mortality. The increasing prevalence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) PA strains complicates clinical management. This study aimed to characterise PA strains causing BSI in neutropenic cancer patients and assess the association between microbiological features and clinical outcomes.

We analysed PA strains from 94 BSI episodes in neutropenic cancer patients across five Spanish hospitals (2006–2018). Antimicrobial resistance, alginate and pigment production were assessed. Whole-genome sequencing was performed to identify resistance mutations and virulence genes.

PA strains exhibited high genetic diversity, with ST175 as the most prevalent clone (28.7%). MDR non-XDR and XDR strains accounted for 10.3% and 18.1% of cases, respectively. The highest resistance rates were for ciprofloxacin (42.6%) and imipenem (36.2%). Resistance was primarily driven by chromosomal mutations. ExoU was present in 24.4% of strains, associated with serotype O11 and ST253. Seven-day and 30-day mortality were 21.3% and 31.9%, respectively. Mortality was not significantly influenced by resistance phenotypes or the presence of ExoU. Polymicrobial infection (p = 0.016), septic shock (p < 0.001), Intensive Care Unit admission (p = 0.002), and inadequate empirical antibiotic therapy (p = 0.002), were linked to increased 7-day mortality.

ST175 was the dominant high-risk clone, associated with antimicrobial resistance, while virulence traits were more common in susceptible strains. Inadequate empirical antibiotic therapy and septic shock significantly impacted early 7-day mortality, underscoring the need for early diagnosis and optimised treatment strategies.