Impact of Feed Supplementation with Antimicrobial Agents on Growth Performance of Broiler Chickens,Clostridium perfringensandEnterococcusCounts, and Antibiotic Resistance Phenotypes and Distribution of Antimicrobial Resistance Determinants inEscherichia coliIsolates

Abstract

The effects of feed supplementation with the approved antimicrobial agents bambermycin, penicillin, salinomycin, and bacitracin or a combination of salinomycin plus bacitracin were evaluated for the incidence and distribution of antibiotic resistance in 197 commensal Escherichia coli isolates from broiler chickens over 35 days. All isolates showed some degree of multiple antibiotic resistance. Resistance to tetracycline (68.5%), amoxicillin (61.4%), ceftiofur (51.3%), spectinomycin (47.2%), and sulfonamides (42%) was most frequent. The levels of resistance to streptomycin, chloramphenicol, and gentamicin were 33.5, 35.5, and 25.3%, respectively. The overall resistance levels decreased from day 7 to day 35 (P < 0.001). Comparing treatments, the levels of resistance to ceftiofur, spectinomycin, and gentamicin (except for resistance to bacitracin treatment) were significantly higher in isolates from chickens receiving feed supplemented with salinomycin than from the other feeds (P < 0.001). Using a DNA microarray analysis capable of detecting commonly found antimicrobial resistance genes, we characterized 104 tetracycline-resistant E. coli isolates from 7-to 28-day-old chickens fed different growth promoters. Results showed a decrease in the incidence of isolates harboring tet(B), bla TEM , sulI, and aadA and class 1 integron from days 7 to 35 (P < 0.01). Of the 84 tetracycline-ceftiofur-resistant E. coli isolates, 76 (90.5%) were positive for bla CMY-2 . The proportions of isolates positive for sulI, aadA, and integron class 1 were significantly higher in salinomycin-treated chickens than in the control or other treatment groups (P < 0.05). These data demonstrate that multiantibiotic-resistant E. coli isolates can be found in broiler chickens regardless of the antimicrobial growth promoters used. However, the phenotype and the distribution of resistance determinants in E. coli can be modulated by feed supplementation with some of the antimicrobial agents used in broiler chicken production.

Characterization and antimicrobial resistance patterns of Escherichia coli isolated from feces of healthy broiler chickens

“…Therefore, it is essential to identify microbial populations that potentially may cause intestinal imbalances and diseases affecting the health and the weight gain of poultry. Increasing resistance to firstline antimicrobial agents among E. coli isolates represents a potential threat both to animal's and human's health (Diarra et al, 2007). In this study, antimicrobial resistance was more generalized among potential APEC isolates; however, there were variations, and for some antimicrobials, such as enrofloxacin, gentamicin and nitrofurantoin, the non-APEC isolates were more resistant.…”

Dynamics of CMY-2 producing E. coli in a broiler parent flock

“…Despite the high prevalence at day 7, CMY-2-E. coli was not able to persist in the chickens. Other studies in poultry have also shown a decreasing prevalence of antibiotic resistant bacteria, with and without the use of antibiotics (Diarra et al, 2007;Baron et al, 2014;Huijbers et al, 2015). However, most of these studies report limited reduction.…”

Rational Use of Antimicrobials in Animal Production:A Prerequisite to Stem the Tide of Antimicrobial Resistance

“…The transfer of MRSA (clonal complex 398) has been shown to occur from infected humans to pigs and later from infected pigs to humans 50 . The selective pressure exerted by prophylactic use of antimicrobial drugs in poultry production has also resulted in the emergence of resistant E. coli and Enterococcus strains 51 . The ubiquitous nature of these organisms and their ability to adapt to different hosts and environments, further increases the transmission threats to susceptible human and animal populations.…”