Table I.

List of studies showing the role of efflux pumps to biocide/antiseptic tolerance in K. pneumoniae, 2002–2022

Citation	Study	Conclusion
Fang et al. [67]	Cloning of a cation efflux pump gene associated with Chlorhexidine resistance in K. pneumoniae.	CepA is associated with Chlorhexidine resistance and may act as a cation efflux pump.
Abuzaid et al. [45]	Klebsiella pneumoniae susceptibility to biocides and its association with cepA, qacΔE1 and qacE efflux pump genes and antibiotic resistance.	There was a close link between carriage of efflux pump genes, cepA, qacΔE1 and qacE genes and reduced biocide susceptibility, but not antibiotic resistance, in K. pneumoniae clinical isolates.
Napasterk et al. [39]	Reduced susceptibility to chlorhexidine in extremely-drug-resistant strains of Klebsiella pneumoniae.	Reduced susceptibility to chlorhexidine appeared to be independent of the expression of cepA, acrA and kdeA efflux pumps.
Azadpour et al. [49]	Prescence of cepA and qacED1 genes and susceptibility to hospital biocides in clinical isolates of K. pneumoniae in Iran.	No significant association of biocide resistance and cepA and qacED1 was observed, rather a close association between qacED1 and antibiotic resistance.
Guo et al. [68]	Determining the resistance of Carbapenem resistant K. pneumoniae to common disinfectants and elucidating the underlying mechanisms	The pan-resistant CRKP contained various MDR genes (qacA, qacE, qacED1, acrA) and exhibited resistance to ethyl-alcohol, iodophor and chlorhexidine acetate.
Vijaykumar et al. [48]	Distribution of biocide resistance genes and biocides susceptibility in multi-drug resistant K. pneumoniae, P. aeruginosa and A. baumannii	No significant correlation between presence or absence of biocide resistance genes and MIC observed.
Wand et al. [55]	SmvA is an important efflux pump for cationic biocides in K. pneumoniae and other Enterobacteriaceae	Increased expression of SmvA results in increased Chlorhexidine resistance. Also, loss of the smvA regulator, SmvR results in increased smvA expression and, consequently, increased chlorhexidine resistance.
Gual-de-Torrella et al. [40]	In vitro activity of six biocides against Carbapenemase-producing K. pneumoniae and presence of genes encoding efflux pumps	The activity of some biocides is affected by temperature and growth media. This activity, in terms of MICs, are not related to the type of clone, ST, Carbapenemase or the presence of the efflux pump genes.
Wand et al. [38]	Contribution of the efflux pump AcrAB-TolC to the tolerance of chlorhexidine and other biocides in Klebsiella spp	Biocide tolerance in K. pneumoniae is dependent upon several components, with increased efflux through AcrAB-TolC being an important one.
Ni et al. [52]	Disinfection strategies for Carbapenem-resistant K.pneumoniae in a Healthcare facility.	The CRKP strains showed extensive resistance to clinically used disinfectants, with high efflux pump gene carrier rates.