Animal Waste, Water Quality and Human Health

Assessing the importance of zoonotic waterborne pathogens 51methicillin-resistant Staphylococcus aureus (MRSA) and bacteria withextended-spectrum beta-lactamase activity that are resistant to all penicillin andcephalosporin based antibiotics (Kadlec et al. 2009, Van den Eede et al. 2009).AMR bacteria from animals are, therefore, of serious concern as a potentialsource of antimicrobial-resistant determinants that may spread to humansthrough food and through the water supply (Collignon et al. 2009). The concernis not only about the transmission of animal pathogens such as multiple AMRSalmonella Typhimurium to humans but also the transmission of AMRdeterminants from animal-specific pathogens to related human-specificpathogens. It is clearly important to improve the management of the use ofantimicrobials in livestock production, so that cross-resistance to antimicrobialsused in human medicine is prevented, and, in so doing, preserve the benefits ofthese antimicrobials as a future resource for use in treating human infections.The World Health Organization has developed and applied criteria to rankantimicrobials according to their relative importance in human medicine.Clinicians, regulatory agencies, policy makers, and other stakeholders areencouraged to use this ranking when developing risk management strategies forthe use of antimicrobials in food production animals (Collignon et al. 2009).Based on this ranking, the antimicrobials of most concern when used in animalproduction are the fluoroquinolones, macrolides, and third- and fourthgenerationcephalosporins.By way of example of the potential problem arising from antibiotic use inanimal production, consider one of the leading zoonotic waterborne pathogenicgenera, Campylobacter, which causes gastroenteritis in humans. Campylobactersare increasingly resistant to antibiotics, especially fluoroquinolones andmacrolides, which are the most frequently used antimicrobials for the treatmentof campylobacteriosis (Bostan et al. 2009, Luangtongkum et al. 2009). Forexample, in the Canadian swine industry, over 60% of Campylobacter spp. areresistant to two or more antimicrobial classes (e.g. 71% are resistant toclindamycin, azithromycin, and erythromycin; Rosengren et al. 2009). Bycontrast, the odds of resistance to a quinolone were nine times higher inCampylobacter from herds with beta-lactam exposure in grow-finish pigscompared with those with no exposure. Such extreme clustering demonstratesthe potential for herd and, in other studies, flock-level interventions to influenceantimicrobial resistance (Rosengren et al. 2009, Schwaiger et al. 2009).In addition to managing antimicrobial resistance in livestock production,manure management can also play an important role. Inactivation of AMRpathogens normally occurs during waste storage and can be accelerated bythermal treatments such as composting; however, some feel that resistance genesmay persist and be passed onto other microbiota which survive heat treatment