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Background <p>Colistin resistance mediated by <i>mcr</i> genes poses a critical threat to antimicrobial therapy, particularly in multidrug-resistant <i>Klebsiella pneumoniae</i>. While <i>mcr-1</i> has been previously identified in clinical <i>Escherichia coli</i> in Tunisia, no human clinical <i>K. pneumoniae</i> isolate carrying this gene has been reported to date.</p> Objectives <p>This study aims to assess colistin resistance rates in carbapenem-resistant clinical <i>K. pneumoniae</i> isolates, characterize genetic resistance determinants in resistant strains, and screen for the occurrence of the <i>mcr-1</i> gene.</p> Methods <p>This study was conducted from January to December 2024 at Habib Thameur Hospital, Tunis and investigated colistin resistance among carbapenem-resistant <i>K. pneumoniae</i> isolates. Colistin resistance was assessed via broth microdilution (EUCAST criteria). Resistance genes were detected via multiplex PCR and confirmed via Sanger sequencing. Sequence identity was analysed with BLASTn database.</p> Results <p>Among the 143 carbapenem-resistant <i>K. pneumoniae</i> isolates, 16 [11.2% (95% CI: 6.5–17.5%)] were colistin resistant. All the isolates were multidrug resistant, with a high prevalence of the <i>blaOXA-48-like</i> (14/16) and <i>blaNDM</i> (11/16) carbapenemase genes and the β-lactamases genes <i>blaCTX-M</i> (14/16) and <i>blaSHV</i> (11/16). Additional resistance determinants included the <i>qnrS</i> (14/16), <i>qnrB</i> (15/16), and 16&#xa0;S rRNA methylase genes (<i>rmtF</i>, <i>rmtC</i>, and <i>armA</i>). One isolate carried the <i>mcr-1</i> gene, displaying moderate colistin resistance (MIC: 4&#xa0;mg/L) and harbouring multiple resistance genes.</p> Conclusion <p>This study reports the first detection of the mobile colistin resistance gene <i>mcr-1</i> in a clinical <i>K. pneumoniae</i> isolate in Tunisia. While chromosomal mechanisms remain predominant in colistin-resistant <i>K. pneumoniae</i> in the country, this finding underscores the urgent need for enhanced molecular surveillance and antibiotic stewardship to curb the potential risk for future dissemination of mcr-mediated resistance in North Africa.</p>

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First report of the mcr-1 gene in colistin-resistant Klebsiella pneumoniae in a tertiary care hospital in Tunisia

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月31日

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  • Manel Ennaceur,
  • Hamza Ben Mesbeh,
  • Othman Bacha,
  • Imene Ouzari,
  • Farouk Barguellil,
  • Sonia Chouaieb

摘要

Background

Colistin resistance mediated by mcr genes poses a critical threat to antimicrobial therapy, particularly in multidrug-resistant Klebsiella pneumoniae. While mcr-1 has been previously identified in clinical Escherichia coli in Tunisia, no human clinical K. pneumoniae isolate carrying this gene has been reported to date.

Objectives

This study aims to assess colistin resistance rates in carbapenem-resistant clinical K. pneumoniae isolates, characterize genetic resistance determinants in resistant strains, and screen for the occurrence of the mcr-1 gene.

Methods

This study was conducted from January to December 2024 at Habib Thameur Hospital, Tunis and investigated colistin resistance among carbapenem-resistant K. pneumoniae isolates. Colistin resistance was assessed via broth microdilution (EUCAST criteria). Resistance genes were detected via multiplex PCR and confirmed via Sanger sequencing. Sequence identity was analysed with BLASTn database.

Results

Among the 143 carbapenem-resistant K. pneumoniae isolates, 16 [11.2% (95% CI: 6.5–17.5%)] were colistin resistant. All the isolates were multidrug resistant, with a high prevalence of the blaOXA-48-like (14/16) and blaNDM (11/16) carbapenemase genes and the β-lactamases genes blaCTX-M (14/16) and blaSHV (11/16). Additional resistance determinants included the qnrS (14/16), qnrB (15/16), and 16 S rRNA methylase genes (rmtF, rmtC, and armA). One isolate carried the mcr-1 gene, displaying moderate colistin resistance (MIC: 4 mg/L) and harbouring multiple resistance genes.

Conclusion

This study reports the first detection of the mobile colistin resistance gene mcr-1 in a clinical K. pneumoniae isolate in Tunisia. While chromosomal mechanisms remain predominant in colistin-resistant K. pneumoniae in the country, this finding underscores the urgent need for enhanced molecular surveillance and antibiotic stewardship to curb the potential risk for future dissemination of mcr-mediated resistance in North Africa.