Effects of intramuscularly administered enrofloxacin on the susceptibility of commensal intestinal Escherichia coli in pigs (sus scrofa domestica)

Abstract

BackgroundIn the European Union, various fluoroquinolones are authorised for the treatment of food producing animals. Each administration poses an increased risk of development and spread of antimicrobial resistance. The aim of this study was to investigate the impact of parenteral administration of enrofloxacin on the prevalence of enrofloxacin and ciprofloxacin susceptibilities in the commensal intestinal E. coli population.Methods E. coli isolates from faeces of twelve healthy pigs were included. Six pigs were administered enrofloxacin on day 1 to 3 and after two weeks for further three days. The other pigs formed the control group. MIC values were determined. Virulence and resistance genes were detected by PCR. Phylogenetic grouping was performed by PCR. Enrofloxacin and ciprofloxacin were analysed in sedimentation samples by HPLC.ResultsSusceptibility shifts in commensal E. coli isolates were determined in both groups. Non-wildtype E. coli could be cultivated from two animals of the experimental group for the first time one week after the first administration and from one animal of the control group on day 28. The environmental load with enrofloxacin in sedimentation samples showed the highest amount between days one and five. The repeated parenteral administration of enrofloxacin to pigs resulted in rapidly increased MIC values (day 28: MIC up to 4 mg/L, day 35: MIC ≥ 32mg/L). E. coli populations of the control group in the same stable without direct contact to the experimental group were affected.ConclusionThe parenteral administration of enrofloxacin to piglets considerably reduced the number of the susceptible intestinal E. coli population which was replaced by E. coli strains with increased MIC values against enrofloxacin. Subsequently also pigs of the control were affected suggesting a transferability of strains from the experimental group through the environment to the control group especially as we could isolate the same PFGE strains from both pig groups and the environment.

The impact of therapeutic-dose induced intestinal enrofloxacin concentrations in healthy pigs on fecal Escherichia coli populations

“…Taking into account these limitations, the presented results still indicate a significant impact of ENR on the fecal microbiota. Two studies using a similar methodology [13,14] (i.e. plating of pig fecal material on a selective agar base to enumerate E. coli from the microbiota) demonstrated a similar susceptibility shift for E. coli from the fecal microbiota after treatment with ENR.…”

“…Previously, it has been demonstrated that the FQ antimicrobials have a detrimental effect on the Gram-negative aerobic microbiota [ 12 ]. Römer et al demonstrated that parenteral administration of ENR in piglets caused a considerable reduction of the susceptible intestinal E. coli population, in favor of resistant E. coli isolates [ 13 ]. Wiuff et al also demonstrated a rapid development of resistance in coliforms in the gut of pigs after PO or IM administration of ENR [ 14 ].…”

Antimicrobial Drug Consumption on Swiss Pig Farms: A Comparison of Swiss and European Defined Daily and Course Doses in the Field

“…These findings are comparable to results recently published from the EFFORT consortium (27), but varying from results of a previous study, where a lower AMU quantification of HPCIAs for pigs in Switzerland based on total amount of given active ingredient was observed (33). Due to the documented spread of resistance genes e.g., against fluoroquinolones in the pig sector (34), every use of these substances should be of concern and further research investigating restriction of indications and potential reductions in usage is needed.…”

Occurrence of quinolone-resistant Escherichia coli in environmental samples from a sow pool system in Switzerland

“…On the other hand, the half-life of FQ in pigs is short. 2,23 While some studies show a duration of an increased excretion of antimi crobial resistant germs for three to four weeks after treatment, 10,22,29 or no increased excretion of fluoroquinolone-resistant E. coli after treating pigs with FQ , 7 other authors isolated FQ resistant E coli up to eight weeks after treatment with FQ 26 and some data indicates that all antimicrobial therapies over the entire life are relevant, not only those carried out shortly before sampling. 1 The most frequent indication for the use of antibiotics in sows in Switzerland is PDS, 16 which usually occurs shortly after farrowing.…”

“…17,21 A shift in susceptibility of commensal E. coli towards resistance could be shown in pigs intramusculary treated with fluoroquionolones and in untreated penmates. 26 In the case of oral therapy with pharmaceutical premixes, surrounding bacterial flora come into direct contact with residues of active substances in dust and feed in the barn. 14 Certain active substances, such as tetracyclines or fluoroquinolones, undergo limited metabolization in pigs and are thus effectively excreted.…”