Case: FDA Policy Effects on Antimicrobial Resistance in Salmonella Dublin Isolates

Submission Category: Cases and Abstracts

Assessing FDA policy effects on antimicrobial resistance in Salmonella Dublin isolates

Angelica Collins & Casey Cazer

Department of Population Medicine & Diagnostic Sciences, Cornell University College of Veterinary Medicine

In 2012 the Food and Drug Administration (FDA) prohibited the extra-label use of cephalosporin class antimicrobials in food-producing animals to reduce the risk of cephalosporin-resistant zoonotic bacteria. The objective of this study is to assess the prevalence of antimicrobial resistant (AMR) Salmonella enterica serotype Dublin before and after this policy change. We have analyzed Salmonella Dublin isolate antimicrobial susceptibility data collected by the National Antimicrobial Resistance Monitoring System at the slaughter stage between 1998 and 2017. Internationally accepted breakpoint values were used to determine if the isolates were resistant or susceptible. Chi-square tests were performed to compare the proportion of resistance before (2006-2011) and after (2012-2017) implementation of the policy. Survival analysis was used to assess shifts in MIC distributions; growth inhibition is used as the event and concentration of the antimicrobial that inhibits growth is used as the time. The chi-square tests showed statistically significant (P < 0.05) increases in the prevalence of resistance to cefoxitin and ceftriaxone, cephalosporin-class antimicrobials, following the implementation of the policy. Chi-square tests also showed statistically significant increases in resistance after the policy for amoxicillin-clavulanic acid, chloramphenicol, ciprofloxacin, nalidixic acid, and streptomycin. There were no significant decreases in resistance. Analysis of the resistance patterns of Salmonella Dublin following the implementation of the FDA policy demonstrate the policy was ineffective at decreasing resistance in Salmonella Dublin. Assessing FDA policy effects on antimicrobial resistance in Salmonella Dublin isolatesAngelica Collins & Casey CazerDepartment of Population Medicine & Diagnostic Sciences, Cornell University College ofVeterinary MedicineIn 2012 the Food and Drug Administration (FDA) prohibited the extra-label use ofcephalosporin class antimicrobials in food-producing animals to reduce the risk ofcephalosporin-resistant zoonotic bacteria. The objective of this study is to assess the prevalenceof antimicrobial resistant (AMR) Salmonella enterica serotype Dublin before and after thispolicy change. We have analyzed Salmonella Dublin isolate antimicrobial susceptibility datacollected by the National Antimicrobial Resistance Monitoring System at the slaughter stagebetween 1998 and 2017. Internationally accepted  breakpoint values were used to determine if theisolates were resistant or susceptible. Chi-square tests were performed to compare the proportionof resistance before (2006-2011) and after (2012-2017) implementation of the policy. Survivalanalysis was used to assess shifts in MIC distributions; growth inhibition is used as the eventand concentration of the antimicrobial that inhibits growth is used as the time. The chi-squaretests showed statistically significant (P < 0.05) increases in the prevalence of resistance tocefoxitin and ceftriaxone, cephalosporin-class antimicrobials, following the implementation ofthe policy. Chi-square tests also showed statistically significant increases in resistance after thepolicy for amoxicillin-clavulanic acid, chloramphenicol, ciprofloxacin, nalidixic acid, andstreptomycin. There were no significant decreases in resistance. Analysis of the resistancepatterns of Salmonella Dublin following the implementation of the FDA policy demonstrate thepolicy was ineffective at decreasing resistance in Salmonella Dublin.