Household Antibacterial Product Use May Promote Microbial Resistance

Laurie Barclay, MD

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July 3, 2008 — Antibacterial product use may lead to decreased susceptibility to other antibacterial ingredients and antibiotic resistance in the home, according to the results of a study reported at the 2008 Annual Conference on Antimicrobial Resistance held in Bethesda, Maryland.

“Quaternary ammonium compounds (QACs), such as benzalkonium chloride [BZK], are broad-spectrum antimicrobials that have been widely used for decades to disinfect environmental surfaces in clinical and industrial settings,” presenter and lead author Allison Aiello, PhD, MS, an assistant professor of epidemiology at the University of Michigan School of Public Health in Ann Arbor, told Medscape Infectious Diseases. “With increasing use of cleaning and hygiene products containing QACs in the home, there is a valid public health concern that biocide resistance may emerge in the community environment,” she said.

“Antibacterial consumer products leave residues on home surfaces, exposing bacterial species to low levels of the agent and creating conditions favorable for development of resistance to both biocides and antibiotics.” Dr. Aiello said. “Currently, reports examining the relationships between biocide use and bacterial resistance among isolates from the community setting are limited. The purposes of the present study were to assess the effect of antibacterial product usage in the home environment on the susceptibility to QACs and to examine the possible correlation between QACs and antibiotic resistance among bacterial isolates sampled from the hands of study participants.”

In this study, 238 households were randomly assigned to use either antibacterial or non-antibacterial cleaning products. At baseline and 1 year later, 645 bacterial isolates, including gram-negative and staphylococcal species, were isolated from hands of participants and tested for minimum inhibitory concentrations to BZK, triclosan, and several antibiotics.

Sensitivity testing was performed for all gram-negative bacteria against gentamicin, imipenem, and ciprofloxacin; for Acinetobacter baumannii and A lwoffii against amikacin and ticarcillin/clavulanate; for Enterobacter agglomerans and E cloacae against trimethoprim/sulfamethoxazole; for Klebsiella pneumonia against trimethoprim/sulfamethoxazole, piperacillin/tazobactam, and ceftriaxone; for Pseudomonas fluorescens/putida against piperacillin/tazobactam and ceftazidime; and for staphylococcal species against oxacillin for methicillin resistance.

The relationship between BZK, triclosan, and antibiotic resistance among bacterial species was determined using logistic regressions with generalized estimating equations.

For all species combined, there were no significant differences between assigned product use and BZK susceptibility. After 1 year, however, for all species combined, there was an association between decreased susceptibility to BZK and triclosan (odds ratio [OR], 2.18; 95% confidence interval [CI], 1.44 – 3.29) and between decreased susceptibility to BZK and antibiotic resistance to a combination of several antibiotics (OR, 2.45; 95% CI, 1.38 – 4.36).

“Our study reports, for the first time, a significant relationship between use of a common antibacterial cleaning agent ([BZK]) and cross-resistance with antibiotics and another antibacterial ingredient (triclosan) in the household setting,” Dr. Aiello said. “The results of our study suggest that the growing concern over the emergence of cross-resistance between biocides used in the household and clinically used antibiotics is warranted.”

A study limitation noted by Dr. Aiello is that the concentrations of biocide tested in the laboratory were much lower than concentrations recommended for home use. However, there have been reports in some clinical settings of diluting these products, although whether this practice occurs in the household setting is unclear.

“Diluting could lead to lower levels of the biocide, which may be an important factor in selecting for antibiotic resistance,” Dr. Aiello said. “There has been little research on how effective these surface and floor biocides are for reducing infectious illnesses in the home environment. Given that there may be a potential risk related to antibiotic resistance, we need to conduct further research on the potential benefits to accurately define the public health importance of these products.”

Medscape Infectious Diseases asked Elizabeth Scott, PhD, an assistant professor and codirector of the Simmons College Center for Hygiene and Health in Home and Community in Boston, Massachusetts, to review the strengths and limitations of this study. Dr. Scott was not involved with this research.

“This is an extensive study conducted over a substantial time period that adds another important piece of information to the growing body of knowledge on the relationship between BZK, triclosan and the potential for antibiotic resistance,” Dr. Scott said. “If the products tested are household cleaning products (as opposed to personal care products), it would have been useful to have tested bacterial cultures from household surfaces as well as from hands. Also, it is not clear whether or not other factors that can influence antibiotic resistance patterns were accounted for, such as skin condition and household antibiotic usage, as well as householder occupations, presence of pets, etc.”

In light of growing concerns about antibiotic resistance, and the need to balance these concerns against protection of an increasing population of vulnerable individuals from community-acquired infections, Dr. Scott recommends better education and dissemination of information on appropriate hygiene and cleaning practices for homes, daycares, schools, workplaces, and other settings.

“We need to be extremely vigilant in protecting the remaining, limited number of effective antibiotics,” Dr. Scott concluded. “This includes careful monitoring of antibacterial products, as well as practicing responsible antibiotic prescribing in both human and animal medicine and animal husbandry. At the same time, it is very important to encourage effective personal hygiene behaviors, as well as household and community cleaning and sanitation practices, as a means of preventing community-acquired infections and thus reducing the reliance on antibiotics — it’s the old adage of ‘prevention is better than cure.’ ”

Dr. Aiello and Dr. Scott have disclosed no relevant financial relationships.

2008 Annual Conference on Antimicrobial Resistance: Abstract S5. June 23–25, 2008.

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