avoparcin and Poultry-Diseases

The persistence or loss of acquired antimicrobial-drug resistance in bacterial populations previously exposed to drug-selective pressure depends on several biological processes. We review mechanisms promoting or preventing the loss of resistance, including rates of reacquisition, effects of resistance traits on bacterial fitness, linked selection, and segregational stability of resistance determinants. As a case study, we discuss the persistence of glycopeptide-resistant enterococci in Norwegian and Danish poultry farms 12 years after the ban of the animal growth promoter avoparcin. We conclude that complete eradication of antimicrobial resistance in bacterial populations following relaxed drug-selective pressures is not straightforward. Resistance determinants may persist at low, but detectable, levels for many years in the absence of the corresponding drugs.

Topics: Animal Husbandry; Animals; Anti-Bacterial Agents; Drug Resistance, Multiple, Bacterial; Enterococcus faecium; Glycopeptides; Humans; Poultry; Poultry Diseases; Selection, Genetic

Prevalence of vancomycin-resistant enterococci (VRE) was investigated in Korean livestock 4 years after the ban of avoparcin in feed additives. VRE were isolated from approximately 16.7% of the chicken samples (57 strains from 342 meat samples) and 1.9% of the pig samples (4 from 214 fecal samples). No VRE, however, was isolated from 110 bovine fecal samples. All the 61 VRE isolates were vanA-type Enterococcus faecium expressing a high-level resistance to vancomycin, and showed resistance to teicoplanin as well except two poultry isolates. In addition, the VRE isolates had heterogeneous pulsed-field gel electrophoresis (PFGE) patterns of SmaI-digested DNA, although identical or closely related profiles were observed among strains isolated from the same farm. Although the chicken isolates were all poultry type with G at position 8,234 of the vanX gene, the pig isolates were all swine type with T at position 8,234 of the vanX gene.

Topics: Animal Feed; Animals; Animals, Domestic; Anti-Bacterial Agents; Bacterial Proteins; Cattle; Cattle Diseases; Chickens; Electrophoresis, Gel, Pulsed-Field; Enterococcus faecium; Feces; Food Microbiology; Glycopeptides; Gram-Positive Bacterial Infections; Korea; Meat; Mutation; Poultry Diseases; Serine-Type D-Ala-D-Ala Carboxypeptidase; Swine; Swine Diseases; Vancomycin Resistance

When avoparcin was prohibited for use as feed additive in poultry in Norway on 31 May 1995, an increased incidence of Clostridium perfringens-associated necrotic enteritis (NE) and an increase in the use of antibacterial (AB) drug therapy in meat-type poultry was expected. The consumption of AB drugs for use against NE in poultry in the period 1990-2001 was investigated by use of sales statistics at the drug-wholesaler level. Defined daily dose (DDD) per kg live weight poultry was the unit of measurement for drug use (to correct for differences in the dosages). Sales figures of the AB drugs were converted to number of DDDpoultry sold for the numbers of broilers at risk (broilers were 97% of the slaughter poultry). Estimated annual percentages of the broilers treated against NE increased abruptly after the avoparcin ban--but in 1996, this figure declined to the same level as before the ban and has remained at that low level since then. In November 1995, narasin was approved temporarily as an ionophore feed additive (IFA) in broilers. The usage patterns of IFAs in broilers were measured as the weight of feed to which an IFA was added per broiler chicken produced. In 1996-2001, the IFAs used in broilers were predominantly narasin. We note that the temporary increase in NE after the avoparcin ban coincide with the period before narasin became available. The increase in the consumption of AB drugs for the treatment of NE in poultry following the avoparcin ban has been negligible.

Topics: Animal Feed; Animal Husbandry; Animals; Anti-Bacterial Agents; Chickens; Clostridium Infections; Clostridium perfringens; Drug and Narcotic Control; Enteritis; Glycopeptides; Ionophores; Legislation, Veterinary; Norway; Poultry Diseases; Pyrans; Turkeys

Fecal samples from poultry on farms established after the ban of avoparcin (study farms) and from poultry on farms previously exposed to avoparcin (control farms) were examined for the presence of vancomycin-resistant enterococci (VRE). The samples were collected during the autumn and winter of 2001-2002. One isolate from each positive sample was selected, identified to species level, and examined for the presence of the vanA gene. The concentration of VRE and generic enterococci in the samples were also determined. In addition, the susceptibility to the ionophoric coccidiostat narasin was examined in a number of enterococcal isolates from poultry and in some enterococci of porcine origin that had not been exposed to narasin. VanA-type VRE was detected in samples from 64% of the study farms and 96% of the control farms. However, the concentration of VRE in the control samples was about six times larger than in the samples from the study farms. The minimum inhibitory concentration values for narasin differed between the poultry (1-4 mg/liter) and the porcine (0.25-0.5 mg/liter) isolates, indicating a decreased susceptibility towards narasin among enterococci from poultry.

Topics: Agriculture; Animals; Anti-Bacterial Agents; Chickens; Enterococcus; Feces; Glycopeptides; Gram-Positive Bacterial Infections; Norway; Poultry Diseases; Prevalence; Pyrans; Turkeys; Vancomycin Resistance

Glycopeptide resistant enterococci (GRE) isolated from animals and humans were characterised using both AFPL typing and genetic characterisation of the glycopeptide resistance transposon Tn1546. All isolates were collected in 1997 when the glycopeptide avoparcin was still being used as growth promoter. All investigated animal isolates were from mixed pig and poultry farms in the Netherlands and the human isolated from the farmers of these farms. A total of 24 isolates were investigated. AFLP and Tn1546 typing revealed that both pig and poultry related enterococcal and vanA transposon genotypes were found among the human isolates indicating spread of glycopeptide resistance from both pig and poultry to the farmers. These findings contradict previous finding that showed that GRE recovered from the general population were genotypically undistinguishable from GRE isolated from pigs but are in line with other studies that demonstrated spread of GRE from poultry to farmers in poultry farms.

Topics: Agriculture; Animals; Anti-Bacterial Agents; Chickens; DNA, Bacterial; Enterococcus; Feces; Glycopeptides; Gram-Positive Bacterial Infections; Humans; Netherlands; Phylogeny; Polymerase Chain Reaction; Poultry Diseases; Swine; Swine Diseases; Vancomycin Resistance

The effects of the growth promoters avoparcin and avilamycin and the ionophore anticoccidials maduramicin, narasin and monensin on the growth of Clostridium perfringens (Cp) in the caeca and on performance of broiler chickens were tested in 2 experiments. The supplements were fed as single feed additives or in some combinations. No clinical signs or lesions caused by coccidia were observed in any of the studies. All supplements had an antibacterial effect on Cp and improved growth rate significantly. Carcass yield of birds fed growth promoters avilamycin or avoparcin was significantly higher compared with birds fed anticoccidials. These data indicate that, what concerns bird performance, during good hygienic conditions supplementation with antibiotic growth promoters may not be necessary when the diet is supplemented with an anticoccidial with antibacterial effects.

Topics: Animal Feed; Animals; Anti-Bacterial Agents; Cecum; Chickens; Clostridium Infections; Clostridium perfringens; Coccidiostats; Glycopeptides; Growth Substances; Ionophores; Lactones; Monensin; Oligosaccharides; Poultry Diseases; Pyrans; Random Allocation

We determined the association between the use of the glycopeptide antibiotic avoparcin as a growth promoter and the occurrence of Enterococcus faecium (VREF) with high-level resistance to vancomycin (MIC > or = 64 micrograms ml-1) on poultry and pig farms. The investigations were conducted as retrospective cohort studies, where groups of farms exposed or not exposed to avoparcin between September 1994 and April 1995 were compared. In poultry, the association between the use of avoparcin and the occurrence of VREF was confounded by the use of broad-spectrum antibiotics, and the adjusted relative risk was 2.9 (1.4-5.9). In pigs, the association had a similar magnitude with a non-adjusted relative risk of 3.3 (0.9-12.3). The similar findings in the two studies provide evidence in favour of a causal association between the use of avoparcin and the occurrence of VREF on farms, and suggest that food animals constitute a potential reservoir of infection for VREF in humans.

Topics: Animals; Anti-Bacterial Agents; Antibodies, Bacterial; Chickens; Cohort Studies; Denmark; Disease Susceptibility; Drug Resistance, Microbial; Enterococcus faecium; Female; Glycopeptides; Gram-Positive Bacterial Infections; Growth Substances; Male; Poultry; Poultry Diseases; Retrospective Studies; Specific Pathogen-Free Organisms; Swine; Swine Diseases; Vancomycin

The clinical, pathological, and bacteriological findings of a mild form of necrotic enteritis (NE) in broiler chickens are presented. The term subclinical NE (SNE) is proposed for this condition. A diagnosis of SNE was based on the detection of macroscopically visible, focal necrotic lesions in the small intestinal mucosa. The ileal gut contents from SNE birds yielded increased numbers of Clostridium perfringens and reduced numbers of coliform bacteria. Reduced numbers of lactobacilli and streptococci were detected in birds from SNE pens and coccidial oocysts were not found in the rectal contents of SNE birds. Statistical analyses showed strong correlations between SNE and increased feed conversion ratio and retarded growth rate. An increased occurrence of SNE was observed in birds on a diet containing a large amount of barley.

Topics: Animal Feed; Animals; Anti-Bacterial Agents; Chickens; Clostridium perfringens; Colony Count, Microbial; Enteritis; Enterobacteriaceae; Glycopeptides; Hordeum; Intestinal Mucosa; Intestine, Small; Lactobacillus; Necrosis; Poultry Diseases; Random Allocation; Streptococcus; Weight Gain

1. The anticoccidial activity of maduramicin ammonium (5 mg/kg food) administered alone or with roxarsone (50 mg/kg food) and/or avoparcin (10 mg/kg food) was evaluated in battery-reared broilers artificially challenged with recent field culture mixtures containing Eimeria acervulina, E. maxima and E. tenella or E. mivati, E. necatrix and E. brunetti. 2. Maduramicin ammonium exhibited a high degree of anticoccidial activity and the addition of roxarsone and/or avoparcin in food at recommended concentrations did not adversely affect the activity.

Topics: Animals; Anti-Bacterial Agents; Arsenicals; Chickens; Coccidiosis; Drug Combinations; Drug Evaluation; Glycopeptides; Lactones; Male; Poultry Diseases; Roxarsone

The influence of growth additives on the duration of salmonella shedding has been variously reported. The different conclusions reached were mainly because of the different experimental systems used. In this paper a naturally infected chicken model for evaluating this problem is described. It simulates commercial conditions and proved to be reproducible in 13 groups, each of 125 birds, over a two-year period.

Topics: Age Factors; Animals; Anti-Bacterial Agents; Cecum; Chickens; Cloaca; Female; Food Additives; Glycopeptides; Male; Monensin; Poultry Diseases; Salmonella; Salmonella Infections, Animal; Species Specificity

Chickens were readily infected with salmonella organisms when fed diets containing unsterilized bone-meal or provided with drinking water containing a suspension of natural salmonella infected chicken faeces. When fed diets containing avoparcin at concentrations of 10 or 100 mg/kg chickens infected in these ways excreted larger numbers of salmonellas for longer periods than did chickens fed a nonmedicated diet.

Topics: Animal Feed; Animals; Anti-Bacterial Agents; Chickens; Feces; Glycopeptides; Poultry Diseases; Salmonella; Salmonella Infections, Animal; Species Specificity

In two experiments (Experiments A and B) chickens experimentally infected with S. infantis at 7 days of age and fed diets containing both avoparcin (10 ppm) and monensin (90 ppm) showed a higher frequency of Salmonella-positive livers and higher caecal counts of Salmonella 1 and 2 weeks after challenge than similarly infected chickens fed only avoparcin (10 ppm). The results may indicate a synergistic action between the two drugs on the ability of chickens to withstand Salmonella infections.

Topics: Animals; Anti-Bacterial Agents; Cecum; Chickens; Female; Food Additives; Furans; Glycopeptides; Liver; Male; Monensin; Poultry Diseases; Salmonella; Salmonella Infections, Animal

Groups of 33 chickens were fed continuously on diets containing feed additives that are employed commercially for a variety of purposes, and were infected orally when 4 days old with a nalidixic acid-resistant mutant of Salmonella typhimurium. The amount of S. typhimurium organisms excreted in their faeces was estimated by culturing them at intervals and in a standard manner on brilliant green agar containing sodium nalidixate; when the chickens were killed their caecal contents were examined by the same technique.Avoparcin and lincomycin, like nitrovin and tylosin (Smith & Tucker, 1975b), favoured colonization of the alimentary tract by the S. typhimurium organisms as shown by the fact that the chickens to which they were fed excreted these organisms in their faeces in higher concentration and for longer periods of time than did chickens fed on non-medicated diets. Amprolium, monensin, dimetridazole, arsenilic acid and nitro-hydroxyphenylarsonate had no obvious effect on the salmonella excretion pattern.When only five chickens in each group were experimentally infected so that the effect of the feed additives on infections acquired by contact could be monitored, avoparcin, lincomycin, nitrovin and tylosin again favoured colonization of the alimentary tract with the S. typhimurium organisms and so did dimetridazole. Arsenilic acid, in contrast, hindered the development of infection. Amprolium, monensin and nitro-hydroxyphenylarsonate were without obvious effect.Many of the chickens that were fed on diets that favoured S. typhimurium colonization, but not those fed on non-medicated diets, were still excreting S. typhimurium organisms in their faeces when they were killed at 56 days of age, the age at which broiler chickens kept under commercial conditions are usually slaughtered.

Topics: Amprolium; Animal Feed; Animals; Anti-Bacterial Agents; Arsenicals; Chickens; Digestive System; Dimetridazole; Feces; Glycopeptides; Leucomycins; Lincomycin; Monensin; Nitrovin; Poultry Diseases; Salmonella typhimurium