Academic journal article Environmental Health Perspectives

Human Health Risk Assessment (HHRA) for Environmental Development and Transfer of Antibiotic Resistance

Academic journal article Environmental Health Perspectives

Human Health Risk Assessment (HHRA) for Environmental Development and Transfer of Antibiotic Resistance

Article excerpt

Introduction

A workshop (Antimicrobial Resistance in the Environment: Assessing and Managing Effects of Anthropogenic Activities), held in March 2012 in Quebec, Canada, focused on antibiotic resistance in the environment and approaches to assessing and managing effects of anthropogenic activities. The human health concern was identified as environmentally derived antibiotic-resistant bacteria (ARB) that may adversely affect human health (e.g., reduced efficacy in clinical antibiotic use, more serious or prolonged infection) either by direct exposure of patients to antibiotic-resistant pathogen(s) or by exposure of patients to resistance determinants and subsequent horizontal gene transfer (HGT) to bacterial pathogen(s) on or within a human host, as conceptualized in Figure 1. ARB hazards develop in the environment as a result of direct uptake of antibiotic-resistant genes (ARG) via various mechanisms (e.g., mobile genetic elements such as plasmids, integrons, gene cassettes, or transposons) and/or proliferate under environmental selection caused by antibiotics and coselecting agents such as biocides, toxic metals, and nanomaterial stressors (Qiu et al. 2012; Taylor et al. 2011), or by gene mutations (Gillings and Stokes 2012). Depending on the presence of recipient bacteria, these processes generate either environmental antibiotic-resistant bacteria (eARB) or pathogens with antibiotic-resistance (pARB) (Figure 1).

Human health risk assessment (HHRA) is the process used to estimate the nature and probability of adverse health effects in humans who may be exposed to hazards in contaminated environmental media, now or in the future [U.S. Environmental Protection Agency (EPA) 2012]. In this review we focus on how to apply HHRA to the risk of infections with pathogenic ARB because they are an increasing cause of morbidity and mortality, particularly in developing regions (Grundrnann et al. 2011). An antimicrobial-resistant microorganism has the ability to multiply or persist in the presence of an increased level of an antimicrobial agent compared with a susceptible counterpart of the same species. For this review, we limited the resistant group of microorganisms to bacteria and therefore to antibiotic resistance, an area in which the term "antibiotic" is used synonymously with "antibacterial." It is important to understand the contribution that the environment has on the development of resistance in both human and animal pathogens because therapeuti-cresistant infections may lead to longer hospitalization, longer treatment time, failure of treatment therapy, and the need for treatment with more toxic or costly antibiotics, as well as an increased likelihood of death.

A vast amount of work has been undertaken to understand the contribution and roles played by hospital and community settings in the dissemination and maintenance of ARB infections in humans. A particular area of focus in terms of exposure in a community setting has been antibiotic use in livestock production and the presence of eARB and pARB in food of animal origin. In 2011, the Codex Alimentarius Commission [established in 1963 by the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) to harmonize international food standards, guidelines, and codes of practice to protect the health of consumers and ensure fair trade practices in the food trade] released guidelines on processes and methodologies for applying risk analysis methods to foodborne antimicrobial resistance related to the use of antimicrobials in veterinary medicine and agriculture (Codex Alimentarius Commission 2011).

Other sources of antibiotics and other antimicrobials in the environment are human sewage (Dolejska et al. 2011), intensive animal husbandry, and waste from the manufacture of pharmaceuticals (Larsson et al. 2007). The environmental consequences from the use and release of antibiotics from various sources (Kummerer 2009a, 2009b) and the HGT of antibiotic-resistance genes (ARG) between indigenous environmental and pathogenic bacteria and their resistance determinants (Borjesson et al. …

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