High intermittent colonization by diverse clones of β-lactam-resistant Gram-negative bacilli suggests an excessive antibiotic use and different sources of transmission in haemodialysis patients.

Background: The spread of β-lactam-resistant Gram-negative bacilli (GNB) is a topic of worldwide concern; however, knowledge about colonization by these bacteria in haemodialysis patients is limited.

Aim: To analyse the dynamics and factors associated with colonization by β-lactam-resistant GNB in a dialysis centre.

Methods: A longitudinal study was conducted. Stool samples were collected for each patient to evaluate extended-spectrum β-lactamase (ESBL)- and carbapenemase-producing Gram-negative bacilli. Colonization screens were performed at three time-points and then classified as absent, intermittent, or persistent. Molecular typing included enterobacterial repetitive intergenic consensus (ERIC)-polymerase chain reaction, pulsed-field gel electrophoresis (PFGE), and multi-locus sequence typing (MLST). Clinical information was obtained from medical records and personal interview. A generalized estimating equations model was performed to determinate factors associated with the colonization.

Findings: A total of 210 patients were included. ESBL-producing and carbapenem-resistant GNB colonization reached 41.2% and 11.5%, respectively. Most patients were intermittent carriers with frequencies of 73.9% and 92.95% for each bacteria group. The most frequent ESBL was CTX-M-G1, while the most common carbapenemase was KPC. ERIC-PCR and PFGE revealed high genetic diversity among strains and the Escherichia coli clone ST131 was the most important by MLST. Fluoroquinolone use (odds ratio: 3.13; 95% confidence interval: 1.03-9.44; P [cap] = 0.043) and chronic obstructive lung disease (odds ratio: 3.53; 1.42-8.74; P = 0.006) were associated with ESBL-producing GNB colonization.

Conclusion: Our findings indicate a high intermittent colonization by diverse clones of β-lactam-resistant GNB in haemodialysis patients. It suggests excessive antibiotic pressure that favours the acquisition of bacteria with diverse genetic profiles and different transmission sources.