Towards a Harmonized Terminology: A Glossary for Biocide Susceptibility Testing

Biocide resistance in Klebsiella pneumoniae: a narrative review

Klebsiella pneumoniae is among the World Health Organization's list of priority pathogens, notorious for its role in causing healthcare-associated infections and neonatal sepsis globally. Containment of K. pneumoniae transmission depends on the continued effectiveness of antimicrobials and of biocides used for topical antisepsis and surface disinfection. Klebsiella pneumoniae is known to disseminate antimicrobial resistance (AMR) through a large auxiliary genome made up of plasmids, transposons and integrons, enabling it to evade antimicrobial killing through the use of efflux systems and biofilm development. Because AMR mechanisms are also known to impart tolerance to biocides, AMR is frequently linked with biocide resistance (BR). However, despite extensive research on AMR, there is a gap in knowledge about BR and the extent to which AMR and BR mechanisms overlap remains debatable. The aim of this paper is to review and summarise the current knowledge on the determinants of BR in K. pneumoniae and highlight content areas that require further inquiry.

Enterobacteria in anaerobic digestion of dairy cattle wastewater: Assessing virulence and resistance for one health security

Samples from a dairy cattle waste-fed anaerobic digester were collected across seasons to assess sanitary safety for biofertilizer use. Isolated enterobacteria (suggestive of Escherichia coli) were tested for susceptibility to biocides, antimicrobials, and biofilm-forming capability. Results revealed a decrease in total bacteria, coliforms, and enterobacteria in biofertilizer compared to the effluent. Among 488 isolates, 98.12 % exhibited high biofilm formation. Biofertilizer isolates exhibited a similar biofilm formation capability as effluent isolates in summer, but greater propensity in winter. Resistance to biocides and antimicrobials varied, with tetracycline resistance reaching 19 %. Of the isolates, 25 were multidrug-resistant (MDR), with 64 % resistant to three drugs. Positive correlations were observed between MDR and increased biofilm formation capacity in both samples, while there was negative correlation between MDR and increased biocide resistance. A higher number of MDR bacteria were found in biofertilizer compared to the effluent, revealing the persistence of E. coli resistance, posing challenges to food safety and public health.

Biocide Susceptibility and Antimicrobial Resistance of Escherichia coli Isolated from Swine Feces, Pork Meat and Humans in Germany

Phenotypic susceptibility testing of Escherichia (E.) coli is an essential tool to gain a better understanding of the potential impact of biocide selection pressure on antimicrobial resistance. We, therefore, determined the biocide and antimicrobial susceptibility of 216 extended-spectrum β-lactamase-producing (ESBL) and 177 non-ESBL E. coli isolated from swine feces, pork meat, voluntary donors and inpatients and evaluated associations between their susceptibilities. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of benzalkonium chloride, chlorhexidine digluconate (CHG), chlorocresol (PCMC), glutaraldehyde (GDA), isopropanol (IPA), octenidine dihydrochloride and sodium hypochlorite (NaOCl) showed unimodal distributions, indicating the absence of bacterial adaptation to biocides due to the acquisition of resistance mechanisms. Although MIC₉₅ and MBC₉₅ did not vary more than one doubling dilution step between isolates of porcine and human origin, significant differences in MIC and/or MBC distributions were identified for GDA, CHG, IPA, PCMC and NaOCl. Comparing non-ESBL and ESBL E. coli, significantly different MIC and/or MBC distributions were found for PCMC, CHG and GDA. Antimicrobial susceptibility testing revealed the highest frequency of resistant E. coli in the subpopulation isolated from inpatients. We observed significant but weakly positive correlations between biocide MICs and/or MBCs and antimicrobial MICs. In summary, our data indicate a rather moderate effect of biocide use on the susceptibility of E. coli to biocides and antimicrobials.