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Background <p>Antimicrobial resistance (AMR) among Gram-negative bacteria represents a major global public health challenge, severely limiting therapeutic options and increasing morbidity and mortality. In particular, the widespread dissemination of extended-spectrum β-lactamase (ESBL)-producing Enterobacterales and the emergence of carbapenem-resistant organisms are critical concerns in both hospital and community settings. In Italy, particularly in southern regions, high rates of multidrug-resistant pathogens have been reported.</p> Methods and results <p>A total of 145 non-duplicate Gram-negative isolates were collected from hospitalized patients in Calabria, Southern Italy, and analyzed by standard antimicrobial susceptibility testing and endpoint PCR for detection of carbapenemase genes (<i>bla</i>KPC, <i>bla</i>VIM, <i>bla</i>NDM, <i>bla</i>OXA-48) and ESBL genes (<i>bla</i>TEM, <i>bla</i>SHV, <i>bla</i>CTX-M). Carbapenem resistance was observed in 60.7% of isolates, predominantly in <i>Klebsiella pneumoniae</i> and <i>Acinetobacter baumannii</i>. Carbapenemase genes were detected in 84.1% of resistant isolates, with <i>bla</i>VIM being the most prevalent (53.4%), followed by <i>bla</i>KPC (34.1%), <i>bla</i>NDM (28.4%), and <i>bla</i>OXA-48 (14.8%); multiple genes were identified in 21.6% of cases. Among carbapenem-susceptible Enterobacterales, 81.3% were phenotypically ESBL producers. Genotypic analysis showed predominance of <i>bla</i>CTX-M (45.8%), followed by <i>bla</i>TEM (29.2%) and <i>bla</i>SHV (16.7%). Discrepancies between phenotypic and genotypic ESBL detection were observed. Also, sequence analysis of <i>ompK35</i> and <i>ompK36</i> in <i>Klebsiella pneumoniae</i> isolates revealed mutations and structural alterations potentially associated with reduced outer membrane permeability.</p> Conclusions <p>This study documents the circulation of carbapenemase and ESBL determinants among Gram-negative clinical isolates in Southern Italy, highlighting the complexity of β-lactam resistance mechanisms. These findings reinforce the importance of integrating molecular surveillance with antimicrobial stewardship and infection control strategies to monitor the dissemination of multidrug-resistant pathogens.</p>

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Molecular characterization of β-lactamase genes and porin alterations in multidrug-resistant Gram-negative clinical isolates from Calabria, Southern Italy

  • 期刊论文

  • 发表日期：

    2026年7月28日

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  • Teresa Maria Rosaria Regina,
  • Chiara Anastasio,
  • Ilaria Gismondo,
  • Maria Teresa Iacino,
  • Paola Crea,
  • Emilia Zicca,
  • Emanuela Oliverio,
  • Carolina Fedele,
  • Cosimo Infusini

摘要

Background

Antimicrobial resistance (AMR) among Gram-negative bacteria represents a major global public health challenge, severely limiting therapeutic options and increasing morbidity and mortality. In particular, the widespread dissemination of extended-spectrum β-lactamase (ESBL)-producing Enterobacterales and the emergence of carbapenem-resistant organisms are critical concerns in both hospital and community settings. In Italy, particularly in southern regions, high rates of multidrug-resistant pathogens have been reported.

Methods and results

A total of 145 non-duplicate Gram-negative isolates were collected from hospitalized patients in Calabria, Southern Italy, and analyzed by standard antimicrobial susceptibility testing and endpoint PCR for detection of carbapenemase genes (blaKPC, blaVIM, blaNDM, blaOXA-48) and ESBL genes (blaTEM, blaSHV, blaCTX-M). Carbapenem resistance was observed in 60.7% of isolates, predominantly in Klebsiella pneumoniae and Acinetobacter baumannii. Carbapenemase genes were detected in 84.1% of resistant isolates, with blaVIM being the most prevalent (53.4%), followed by blaKPC (34.1%), blaNDM (28.4%), and blaOXA-48 (14.8%); multiple genes were identified in 21.6% of cases. Among carbapenem-susceptible Enterobacterales, 81.3% were phenotypically ESBL producers. Genotypic analysis showed predominance of blaCTX-M (45.8%), followed by blaTEM (29.2%) and blaSHV (16.7%). Discrepancies between phenotypic and genotypic ESBL detection were observed. Also, sequence analysis of ompK35 and ompK36 in Klebsiella pneumoniae isolates revealed mutations and structural alterations potentially associated with reduced outer membrane permeability.

Conclusions

This study documents the circulation of carbapenemase and ESBL determinants among Gram-negative clinical isolates in Southern Italy, highlighting the complexity of β-lactam resistance mechanisms. These findings reinforce the importance of integrating molecular surveillance with antimicrobial stewardship and infection control strategies to monitor the dissemination of multidrug-resistant pathogens.