Evaluation of epidemiological cut-off values indicates that biocide resistant subpopulations are uncommon in natural isolates of clinically-relevant microorganisms.
To date there are no clear criteria to determine whether a microbe is susceptible to biocides or not. As a starting point for distinguishing between wild-type and resistant organisms, we set out to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) distributions for four common biocides; triclosan, benzalkonium chloride, chlorhexidine and sodium hypochlorite for 3319 clinical isolates, with a particular focus on Staphylococcus aureus (N = 1635) and Salmonella spp. (N = 901) but also including Escherichia coli (N = 368), Candida albicans (N = 200), Klebsiella pneumoniae (N = 60), Enterobacter spp. (N = 54), Enterococcus faecium (N = 53), and Enterococcus faecalis (N = 56). From these data epidemiological cut-off values (ECOFFs) are proposed. As would be expected, MBCs were higher than MICs for all biocides. In most cases both values followed a normal distribution. Bimodal distributions, indicating the existence of biocide resistant subpopulations were observed for Enterobacter chlorhexidine susceptibility (both MICs and MBCs) and the susceptibility to triclosan of Enterobacter (MBC), E. coli (MBC and MIC) and S. aureus (MBC and MIC). There is a concern on the potential selection of antibiotic resistance by biocides. Our results indicate however that resistance to biocides and, hence any potential association with antibiotic resistance, is uncommon in natural populations of clinically relevant microorganisms.
Quotient Bioresearch, Fordham, United Kingdom.
Ian
I
Morrissey
Dipartimento de Biotecnologie, Università di Siena, Siena, Italy.
Marco Rinaldo
MR
Oggioni
Quotient Bioresearch, Fordham, United Kingdom.
Daniel
D
Knight
Servicio de Microbiología and CIBER en Epidemiología y Salud Pública and Instituto Ramón y Cajal de Investigación Sanitaria, Madrid, Spain.
Tania
T
Curiao
Servicio de Microbiología and CIBER en Epidemiología y Salud Pública and Instituto Ramón y Cajal de Investigación Sanitaria, Madrid, Spain.
Teresa
T
Coque
Gazi University School of Medicine, Department of Medical Microbiology, Ankara, Turkey.
Ayse
A
Kalkanci
Centro Nacional de Biotecnologia-CSIC, Madrid, Spain.
Jose Luis
JL
Martinez
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification; D001424:Bacterial Infections / Q000453:epidemiology* / Q000382:microbiology; D004202:Disinfectants / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D005658:Fungi / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification; D006801:Humans; D008826:Microbial Sensitivity Tests; D009181:Mycoses / Q000453:epidemiology* / Q000382:microbiology
D000900:Anti-Bacterial Agents; D004202:Disinfectants