Abstract
Norway has a favourable situation with regard to health status and antimicrobial usage in the pig production sector. However, one of the major disease-causing agents in the commercial pig population is Actinobacillus pleuropneumoniae (APP). In some herds, APP eradication has been performed by using enrofloxacin in combination with a partial herd depopulation. The aim of this study was to investigate the long-term effects of a single treatment event with enrofloxacin on the occurrence of quinolone resistant Escherichia coli (QREC). The study was designed as a retrospective case/control study, where the herds were selected based on treatment history. Faecal samples were taken from sows, gilts, fattening pigs and weaners for all herds where available. A semi-quantitative culturing method was used to identify the relative quantity of QREC in the faecal samples. A significant difference in overall occurrence and relative quantity of QREC was identified between the case and control herds, as well as between each animal age group within the case/control groups. The results indicate that a single treatment event with enrofloxacin significantly increased the occurrence of QREC in the herd, even years after treatment and with no subsequent exposure to quinolones.
Highlights
Quinolones are categorized as a highest priority drug on the WHO list of critically important antibiotics for human medicine [1], and are restricted for use in animals by the EU AntimicrobialAdvice ad hoc Expert Group (AMEG) [2]
Little is known about the long-term persistence of quinolone resistant Escherichia coli (QREC) among pig herds, as most studies have only investigated the persistence of QREC a few months after treatment [4,5]
Less than 1% of the antibiotics used for pigs are quinolones [6], and quinolone resistance among E. coli has only been detected at low levels [7]
Summary
Quinolones are categorized as a highest priority drug on the WHO list of critically important antibiotics for human medicine [1], and are restricted for use in animals by the EU AntimicrobialAdvice ad hoc Expert Group (AMEG) [2]. Quinolones are categorized as a highest priority drug on the WHO list of critically important antibiotics for human medicine [1], and are restricted for use in animals by the EU Antimicrobial. Since quinolones are highly mutagenic, the use of such compounds has been linked to an increased occurrence of quinolone resistant E. coli (QREC) [3]. In Norway, antibiotics are not allowed to be used as growth promoters (feed additives) or for routine prevention of infection in any animal production, and the use of antibiotics in pig production is very low [6]. Less than 1% of the antibiotics used for pigs are quinolones [6], and quinolone resistance among E. coli has only been detected at low levels [7].
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