Evaluation of epidemiological cut-off values indicates that biocide resistant subpopulations are uncommon in natural isolates of clinically-relevant microorganisms

• Published in: PloS one Vol. 9; no. 1; p. e86669
• Main Authors: Morrissey, Ian, Oggioni, Marco Rinaldo, Knight, Daniel, Curiao, Tania, Coque, Teresa, Kalkanci, Ayse, Martinez, Jose Luis
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 23.01.2014; Public Library of Science (PLoS)
• Subjects: Analysis; Anti-Bacterial Agents - pharmacology; Antibiotic resistance; Antibiotics; Bacteria - classification; Bacteria - drug effects; Bacteria - isolation & purification; Bacterial Infections - epidemiology; Bacterial Infections - microbiology; Benzalkonium chloride; Biocides; Biology; Chlorhexidine; Chlorides; Clinical isolates; Consortia; Disinfectants - pharmacology; Drug resistance; Drug Resistance, Microbial; E coli; Epidemiology; Escherichia coli; Fungi - classification; Fungi - drug effects; Fungi - isolation & purification; Genes; Hospitals; Humans; Klebsiella; Laboratories; Medical schools; Medicine; Microbial drug resistance; Microbial Sensitivity Tests; Microorganisms; Minimum inhibitory concentration; Mycoses - epidemiology; Mycoses - microbiology; Natural populations; Normal distribution; Nosocomial infections; Salmonella; Sodium; Sodium hypochlorite; Staphylococcus aureus; Subpopulations; Surface active agents; Surveillance; Triclosan; Ankara Turkey; Turkey; United Kingdom > UK; Western Australia Australia; Spain
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0086669

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.