This study examined the incorporation of benzalkonium chloride into palygorskite and montmorillonite, assessing their potential as drug carriers. The aim was to evaluate the use of both clay minerals as viable options for antibacterial drug delivery. Various amounts (0.5, 1.0 and 2.0 times the cation-exchange capacity) of benzalkonium chloride were incorporated into both clay minerals, and the resulting materials were characterized using Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction and elemental analysis using both CHNS-O elemental analysis and energy-dispersive X-ray spectroscopy. The Fourier-transform infrared spectroscopy and elemental analysis results indicate that benzalkonium chloride was incorporated successfully into the clay minerals. The X-ray diffraction traces of organo-montmorillonite indicate that the d-value increased as benzalkonium chloride content increased, confirming the intercalation of benzalkonium chloride within the montmorillonite interlayer space. By contrast, this behaviour was not observed for palygorskite. For the benzalkonium chloride-release studies, an initial burst release was found within the first 5 h, followed by a sustained release of benzalkonium chloride during the remaining testing time (24 h). Drug-release profiles were similar for modified palygorskite or montmorillonite during the testing time (24 h). Both clay minerals modified with benzalkonium chloride are promising materials for use as antibacterial fillers for several applications, including in the dental care industry.

The present study investigates the effect of adaptive resistance to ciprofloxacin (Cip) and benzalkonium chloride (BC) on biofilm formation potential (BFP), efflux pump activity (EPA) and haemolysin activity of Escherichia coli isolates of dairy origin. All the isolates, irrespective of antimicrobial susceptibility, developed significant adaptive resistance (P < 0·05). All the resistant phenotypes (antibiotic resistant: AR; & biocide resistant: BR) were stronger biofilm former and post-adaptation, an insignificant change was observed in their BFP. Whereas, post-adaptation, non-resistant isolates (antibiotic non-resistant: ANR; biocide non-resistant: BNR) transformed from poor or moderate to strong biofilm formers. Post-adaptive percentage increase in EPA was highly significant in non-resistant categories (P < 0·01) and significant at P < 0·05 in BR category. Interestingly, post-adaptive increase in EPA in BR isolates was more than that in AR yet, the latter exhibited greater adaptive resistance than the former. These findings indicated prevalence of some other specific resistance mechanism/s responsible for adaptive resistance against Cip. Strain specific variations were observed for stability of adaptive resistance and haemolysin activity for all the categories. Our findings especially in reference to post-adaptation upgradation of BFP status of non-resistant isolates seems to be providing an insight into the process of conversion of non-resistant isolate into resistant ones with enhanced BFP. These observations emphasize the serious implications of sub-lethal residual levels of antimicrobials in food environments and suggest a role of food chain in emergence of antimicrobial resistances.