Abstract

Hamza Bougoun*, Zaghloul Samy, Rim Messaoudi, Amina Benouda

ABSTRACT

Background. Bacterial colonization frequently precedes documented infection in patients with acute leukemia. The prognostic value of multi-site colonization burden remains insufficiently characterized in North African hematology settings. Objective. To describe bacterial colonization and infection among leukemia patients in a Moroccan center and to assess the association between the number of positive carriage sites, colonization-infection concordance, and cytopenia depth. Methods. We conducted a retrospective single-center study over 2023-2025. Bacteriology records from 97 patients with acute leukemia or related hematological disorders were linked to bone marrow aspirate data using patient identifiers. Specimens were categorized as carriage/colonization or suspected/documented infection. The primary outcome was infection with a carried organism, defined by species-level concordance between a carriage isolate and an infection isolate in the same patient. Trends were assessed using the Cochran-Armitage test. Results. Overall, 1,017 bacteriological specimens and 301 isolates were analyzed. Carriage/colonization specimens accounted for 740/1,017 specimens (72.8%), and 292 specimens (28.7%) were bacteriologically positive. Twenty-nine patients (29.9%) carried at least one multidrug-resistant isolate, mostly ESBL-producing bacteria (51/52 MDR isolates). A single carbapenem-resistant Pseudomonas aeruginosa isolate was identified, with no MRSA. Among 32 patients with suspected infection, 17 (53.1%) developed infection with a previously carried species; carriage strictly preceded infection in 11 patients (34.4%). Infection with the carried organism increased with the number of positive carriage sites: 0% for 0 site, 10.0% for 1 site, 21.1% for 2 sites, and 42.9% for >=3 sites (trend p = 0.0013). Rectal and nasal positivity were significantly associated with concordant infection (p = 0.010 and p = 0.008). Concordant infection also increased with cytopenia depth (trend p = 0.046). Conclusion. Multi-site bacterial colonization burden was a simple, graded marker of infection risk in leukemia patients. Structured multi-site screening may refine microbiological risk stratification and empirical treatment decisions.