Monitoring for the development of antimicrobial resistance during the use of olaquindox as a feed additive on commercial pig farms

Abstract

Since 1982, when olaquindox was introduced as a pig-feed additive in the UK, about 12 commercial farms in Suffolk have been monitored annually to check for the possible emergence of resistance to olaquindox and chloramphenicol among the coliform flora of the pigs and their environment. In spite of the sampling variability and the impossibility of controlling the use of feed additives and management on the farms, the overall results obtained were consistent and, it is suggested, the method is widely applicable. A steady, albeit low, increasing incidence and level of resistance to olaquindox was recorded (1982-1984) on farms using it and, to a lesser degree, on neighbouring farms that did not. No significant increase in the level of chloramphenicol resistance was observed. Genetical studies on a selection of olaquindox-resistant isolates suggested that the genes determining resistance were likely to be borne on the chromosome.

Conjugative Plasmid Conferring Resistance to Olaquindox

“…Other studies have demonstrated increased resistance to olaquindox on pig farms using olaquindox. There was a slight correlation between resistance to olaquindox and resistance to chloramphenicol or ampicillin (5,7). The aim of the present study was to find out if plasmid-bound olaquindox resistance exists.…”

“…It is active against coliform bacteria (3), where it inhibits DNA synthesis (10). Resistance has been defined with a breakpoint of 64 g/ml (3) or 50 g/ml (7). Until 2000, the compound has been allowed in concentrations of up to 100 mg/kg in feed for pigs younger than 4 months.…”

“…Since the introduction of the compound in the 1980s, there has been some concern about whether resistance would arise and, if so, whether this resistance would be transferable and whether it would be linked to other resistance determinants (2,5,7). A survey study in Denmark has demonstrated the presence of a small fraction of olaquindox-resistant coliform bacteria in farm animals (3).…”

Necessary Usage of Antibiotics in Animals

“…Meanwhile, resistance to ampicillin needs to develop more gradually [44]. Similarly, tetracycline and avoparcin persistence are widely affected by many interfered factors including the re-exposure withdrawn antibiotics [42,45].…”

“…When livestock flocks treated with sulfonamides, amino glycosides or tetracyclines, widespread resistance of bacteria was observed. While the corresponding resistances to other antibiotics like ampicillin and olaquindox is less widespread [44]. It is worthy to mention that multiple resistances to more than one class of antibiotics seemed to be common with animal strains of E. coli.…”