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Multicenter Study
. 2025 Jun 3;25(1):790.
doi: 10.1186/s12879-025-11178-w.

Convergence of multidrug resistance and efflux-mediated biocide tolerance in klebsiella pneumoniae ST307: implications for nosocomial infection control in Iranian hospitals

Rezvan Goodarzi  1 , Sima Kazemi  2 , Mohammad Hossein Nasershariati  3 , Babak Asghari  4   5
Affiliations
Multicenter Study

Convergence of multidrug resistance and efflux-mediated biocide tolerance in klebsiella pneumoniae ST307: implications for nosocomial infection control in Iranian hospitals

Rezvan Goodarzi et al. BMC Infect Dis. .

Abstract

Background: The relentless evolution of K. pneumoniae ST307 into a "superbug" with dual resistance to last-line antibiotics and hospital disinfectants poses an existential threat to infection control. This study characterizes the molecular epidemiology, resistance profiles, and biocide tolerance of ST307 isolates from Iranian hospitals, highlighting its role in nosocomial outbreaks.

Methods: A multicenter cross-sectional analysis of 500 K. pneumoniae isolates (2022-2024) utilized CLSI-compliant disk diffusion, broth microdilution, and PCR for resistance genes (blaCTX-M-15, blaNDM-1,cepA, qacED1). Biocide MICs were correlated with genetic markers.

Results: ST307 accounted for 30% (150/500) of isolates, predominantly from ICUs. Resistance rates included meropenem (60.0%; MIC₅₀ >32 µg/mL), ciprofloxacin (75.3%), and gentamicin (45.3%). Colistin retained efficacy (85.3% susceptibility). Elevated biocide MICs (chlorhexidine ≥ 0.5% [70.0%]; benzalkonium chloride ≥ 0.1% [65.3%]) correlated with cepA (65.3%) and qacED1 (70.0%) positivity (p < 0.01). Carbapenemase genes blaOXA-48 (22.0%) and blaNDM-1 (10.0%) co-occurred with ESBLs.

Conclusions: ST307's convergence of resistance mechanisms represents a catastrophic failure of current infection control frameworks. Without immediate interventions-such as ICU closures for deep disinfection, restricted colistin/tigecycline use, and genomic surveillance mandates-this clone will dominate Iranian hospitals within 3-5 years.

Keywords: Klebsiella pneumoniae ST307; bla CTX−M−15; Antimicrobial stewardship; Biocide tolerance; Carbapenem-resistant Enterobacteriaceae; Efflux pump-mediated resistance; Infection control; Molecular epidemiology; Multidrug resistance; Nosocomial infections.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: The study was approved by the Institutional Review Board of Arak Branch, Islamic Azad University, Arak, Iran (Ethical approval code: IR.ABIAU.REC.1402.927). Ethical Review Board approved informed consent taken from all the participants. All methods were carried out in accordance with relevant guidelines and regulations/Declaration of Helsinki. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests. Clinical trial: Not applicable.

Figures

Fig. 1
Fig. 1
Type of Klebsiella pneumoniae isolates
Fig. 2
Fig. 2
Antimicrobial Susceptibility Profiles
Fig. 3
Fig. 3
Molecular analysis prevalence of efflux pump genes
Fig. 4
Fig. 4
Molecular Characterization of Antimicrobial Resistance Genes
See this image and copyright information in PMC

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