monensin and olaquindox

Antibiotics are commonly used as growth promoters in animal husbandry worldwide. This practice has been linked to the emergence of particular antibiotic-resistant bacteria, and is now controversial. In this study, the ability of growth-promoting antibiotics to induce Shiga toxin (Stx)-converting bacteriophages from Stx-producing Escherichia coli (STEC) strains was investigated. Subinhibitory concentrations of the antibacterial growth promoters olaquindox, carbadox, tylosin and monensin were used for induction experiments. The amount of mature Stx-converting phage particles released from induced and non-induced cultures was determined, and the production of Stx was simultaneously measured by ELISA. Whereas the quinoxaline-1,4-dioxide-type antibiotics olaquindox and carbadox enhanced the release of Stx-converting phage particles from STEC cells, tylosin and monensin decreased phage induction. The production of Stx increased or decreased simultaneously with the amount of free phages. The results of this study show that particular antibacterial growth promoters can induce Stx phages. In vivo induction of Stx phages from lysogenic STEC may increase the amount of free phages in the intestine and therefore may contribute to the spread of STEC and development of new STEC pathotypes.

Topics: Animal Husbandry; Anti-Bacterial Agents; Anti-Infective Agents; Bacterial Toxins; Bacteriophages; Carbadox; Escherichia coli O157; Growth Substances; Microbial Sensitivity Tests; Monensin; Quinoxalines; Shiga Toxins; Tylosin; Viral Plaque Assay

Clinical signs of proliferative haemorrhagic enteropathy (PHE) including anaemia, dysentery and sudden death were observed in finisher pigs and young breeding stock on 2 farms. On farm A, PHE occurred 12 months after repopulation of the farm. Other outbreaks of PHE occurred after the withdrawal of therapeutic concentrations of in-feed antibacterial agents (farm A), or after monensin sodium (100 g/t) replaced olaquindox (100 g/t) in feed (farm B). The outbreaks, the possible sources of contamination and the role of antibacterial feed additives in the treatment and control of PHE are described.

Topics: Anemia; Animal Feed; Animals; Anti-Bacterial Agents; Antiprotozoal Agents; Bacterial Infections; Disease Outbreaks; Drug Therapy, Combination; Dysentery; Enteritis; Epithelium; Female; Gastrointestinal Hemorrhage; Intestine, Large; Intestine, Small; Male; Monensin; Pregnancy; Quinoxalines; Swine; Swine Diseases; Victoria