by William A. Rutala, PhD, MPH, David J. Weber MD, MPH
Carbapenem-resistant Enterobacteriaceae (CRE) have broad resistance to most β-lactam antibiotics and are a growing worldwide problem. CRE infections are difficult to treat, have a substantial mortality, and are involved in healthcare-associated outbreaks via contaminated environmental surfaces and medical equipment. Colistin-resistant Enterobacteriaceae carrying the mcr-1 gene are a global health concern since colistin is often a last-line antibiotic used to treat CRE. Furthermore, a recent study from China described a hospital outbreak caused by MCR-1-producing Klebsiella pneumoniae with potential spread of mcr-1 via the hospital environment.
Although there is currently no strong scientific evidence demonstrating that clinical use of disinfectants/antiseptics is associated with selection of antibiotic-resistant organisms, some studies have described reduced susceptibility to disinfectants (e.g., quaternary ammonium compounds [QAC]), antiseptics (e.g., chlorhexidine), and cross-resistance (e.g., benzalkonium chloride/quinolones). Susceptibility to germicides (e.g., disinfectants, antiseptics) for carbapenem- or
colistin-resistant Enterobacteriaceae is poorly described. Kanamori et al recently published a paper on the efficacy of multiple germicides against these emerging antibiotic-resistant pathogens using a disc-based quantitative carrier test method.
The efficacy of germicides with active ingredient, product name, and classification against test organisms is summarized in Table 1. Overall, most germicides reached at least 3-log10 reduction (20/22 [91%] for KPC-K. pneumoniae, 22/22 [100%] for KPC-E. cloacae, 18/22 [82%] for KPC-E.coli, 19/22 [86%] for MCR-1-E. coli). Furthermore, all germicides, except for two products (1% chlorhexidine gluconate plus 61% ethyl alcohol and 3% hydrogen peroxide) against MCR-1-E. coli, demonstrated at least 2-log10 reduction for these pathogens even in challenging test conditions (5% FCS and 1 minute exposure time). Given that hospital environmental surfaces generally have <2-log10 organisms/cm2, this level of kill is likely sufficient for use as a surface disinfectant. Thus, these study results demonstrated that germicides commonly used in healthcare facilities likely will be effective against carbapenem/colistin-resistant Enterobacteriaceae when used appropriately. See Table 1 next page.
Reference
Kanamori H, Rutala WA, Gergen MF, Sickbert-Bennett EE, Weber DJ. Germicidal activity against carbapenem-resistant Enterobacteriaceae using a quantitative carrier test method. Antimicrob Agents Chemotherapy 2018;60:1-5
Table 1. Efficacy (mean log10 reductions) of the 21 germicides against carbapenem/colistin-resistant Enterobacteriaceae using a quantitative carrier test method.
| Active Ingredient | Formulation Tested | Classification |
KPC E. coli |
KPC K. pneumoniae |
KPC E. cloacae |
MCR-1 E. coli |
| 70% ethanol | Undiluted | Antiseptic | 4.6 | 3.5 | 4.1 | 4.2 |
| 10% povidone-iodine / 1% titratable iodine | Undiluted | Antiseptic | 3.4 | 2.9 | 3.5 | 3.9 |
| 0.5% triclosan | Undiluted | Antiseptic / Handwash | 2.3 | 2.9 | 3.3 | 3.8 |
| 1% chloroxylenol | Undiluted | Antiseptic / Handwash | 4.3 | 3.7 | 4.5 | 4.4 |
| 1% chlorhexidine gluconate solution, 61% ethyl alcohol | Undiluted | Antiseptic / Surgical Hand Scrub | 2.6 | 3.8 | 3.7 | 1.8 |
| 2% chlorhexidine gluconate solution | Undiluted | Antiseptic / Surgical Hand Scrub / Handwash | 3.4 | 3.5 | 3.4 | 4.1 |
| 4% chlorhexidine gluconate solution | Undiluted | Antiseptic / Surgical hand scrub / Handwash | 3.1 | 4.0 | 3.5 | 4.4 |
| 70% isopropyl alcohol | Undiluted | Antiseptics / Disinfectant | 4.6 | 4.0 | 4.9 | 4.4 |
| 5.25% sodium hypochlorite | 1:10 dilution | Disinfectant | 4.9 | 5.6 | 5.9 | 4.4 |
| 5.25% sodium hypochlorite | 1:50 dilution | Disinfectant | 4.9 | 3.5 | 3.4 | 4.4 |
| 9.09% o-phenylphenol, 7.66% p-tertiary amylphenol | 1:128 dilution | Disinfectant | 4.9 | 5.6 | 5.8 | 4.4 |
| 3% hydrogen peroxide | Undiluted | Disinfectant | 2.2 | 3.5 | 3.2 | 1.7 |
| 1.4% hydrogen peroxide | Undiluted | Disinfectant | 4.9 | 5.6 | 5.8 | 4.4 |
| 58% ethanol, 0.1% QACa | Undiluted | Disinfectant | 4.9 | 5.6 | 5.8 | 4.4 |
| 21.7% QACb | 1:256 dilution | Disinfectant | 4.9 | 3.5 | 4.7 | 4.4 |
| 55% isopropyl alcohol, 0.5% QACc | Undilutede | Disinfectant | 4.9 | 5.2 | 5.8 | 4.4 |
| 28.7% isopropyl alcohol, 27.3% ethyl alcohol, 0.61% QACd | Undilutede | Disinfectant | 4.8 | 5.6 | 5.9 | 4.4 |
| 35% peracetic acid | 0.20% | High-level Disinfectant / Chemical Sterilant | 4.9 | 5.6 | 5.8 | 4.4 |
| 0.55% ortho-phthalaldehyde | Undiluted | High-level Disinfectant / Chemical Sterilant | 2.4 | 4.8 | 3.4 | 2.0 |
| 2.4% glutaraldehyde | Undiluted | High-level Disinfectant / Chemical Sterilant | 4.9 | 5.6 | 5.8 | 4.4 |
| 27.5% hydrogen peroxide, 5.8% peroxyacetic acid | 1:43 dilution | High-level Disinfectant / Chemical Sterilant | 4.9 | 5.6 | 5.8 | 4.4 |
| 2% accelerated hydrogen peroxide | Undiluted | High-level Disinfectant / Chemical Sterilant | 5.2 | 5.9 | 5.8 | 4.4 |
Values are shown in mean log10 reductions under a test condition of 106 test organisms with 5% fetal calf serum and 1 minute contact time.
a, QAC, quaternary ammonium compounds: Alkyl (C14 50%, C12 40%, C16 10%) dimethyl benzyl ammonium saccharinate 0.1%.
b, QAC: Octyl decyl dimethyl ammonium chloride 6.51%; Dioctyl dimethyl ammonium chlorid 2.604%; Didecyl dimethyl ammonium chlorid 3.906%; Alkyl (50% C14, 40% C12, 10%