Within a veterinary framework, Hendriksen et al. (2008a,2008b) surveyed
resistance across Europe among bacterial pathogens and indicator bacteria for
pigs and cattle. While their work did not incorporate harmonisation efforts into
the data collection process, it did provide a positive step forward towards the
creation of national surveillance schemes.
3.4 Impact of Antibiotic Use on Resistance
Since humans share a number of pathogens with food-producing animals (where
they can be pathogenic or benign), it is frequently alleged that particular resistance
patterns detected in human pathogens result from veterinary antibiotic use. The use
of antibiotics as growth promoters in agriculture was challenged and was subse-
quently banned in Europe (Phillips 2007 ).
Even though some of the proposed links between observed resistance in particu-
lar bacterial species and the use of particular drugs in agriculture are seemingly
obvious, a detailed examination of available data reveals the presence of complex
issues and disparate opinions. There are authors who believe it unlikely that
agricultural usage poses a major risk to human health. These authors base their
opinion either upon conclusions that there is little to no role of veterinary usage in
the selection or propagation of resistant strains, or that such situations, if they exist,
pose minimal risk to human health (see review of Wassenaar 2005 and Casewell
et al. 2003 ; Phillips et al.2004a,b; Phillips 2007 ). Conversely, other investigators
subscribe to a different view (Aarestrup et al. 1998 ; Bager et al. 2002 ; Chiller et al.
2004 ; Collignon 2004 ; Jensen et al. 2004 ; McEwen and Fedorka-Cray 2002 ;
Phillips et al.2004a,2004b; Phillips 2007 ; Tollefson 2004 ). This ongoing debate,
as exemplified by the diversity of views in these citations, reflects the difficulty
associated with assigning causality to human adverse effects as a consequence of
antimicrobial resistance arising from antimicrobial drug use in animals.
Regardless of the varying opinions on this topic, recent evidence clearly sup-
ports the view that certain antimicrobial agents may contribute to the prevalence of
plasmid-mediated drug and indeed chromosomal resistance in bacteria that infect
both humans and animals (Turnidge 2004 ). Since animals and humans provide
overlapping reservoirs of antimicrobial resistance determinants, the issue cannot be
ignored. The concern is, therefore, that indiscriminate use of antimicrobial agents in
food animal production may result in the transfer of resistant bacteria and resistance
genes to human pathogens, thereby compromising the treatment of infectious
diseases in people (McEwen and Fedorka-Cray 2002 ; O’Brien 2002 ; Turnidge
2004 ).
Despite differing opinions of the extent to which the use of antimicrobial drugs
in food animals poses a threat to human health, most workers agree on the
importance of minimising the potential health hazards resulting from antimicrobial
resistance. One suggested solution was to eliminate the use of all antimicrobial
drugs used in humans as animal growth promoters. However, some investigators
Antimicrobial Drug Resistance 239