Effect of intervention on the occurrence of antimicrobial resistance.
Explore the source record for details and available documents.
Animal Husbandry↗
Biomedical subjects
F M Aarestrup
Publications and source records attributed to F M Aarestrup.
Experimental Mycobacterium leprae infection in BALB/c mice: effect of BCG administration on TNF-alpha production and granuloma development.
In the present study, the experimental model of Mycobacterium leprae infection in the foot pads of BALB/c mice was used to investigate the effects of BCG administration on tumor necrosis factor-alpha (TNF-alpha) production and granuloma development. It was observed that mice intravenously infected with BCG 7 months after M. leprae inoculation into the foot pads presented a more effective mycobacteria clearance, revealed by a significant reduction of BCG-colony forming units in the spleen and by the reduction of acid-fast bacilli (AFB) in the foot pads. BCG infection at the peak of M. leprae infection also modulated the granulomatous response to M. leprae by converting mononuclear granulomas into an epithelioid-cell granuloma. Furthermore, lower TNF-alpha serum levels were detected in M. leprae-infected mice when compared to mice infected with M. leprae + BCG. An analysis of the TNF-alpha gene expression in the spleen by semiquantitative reverse transcription-polymerase chain reactions (RT-PCR) demonstrated that co-infection with BCG induced an earlier expression of TNF-alpha mRNA than in M. leprae-infected mice. The numbers of TNF-alpha-positive cells and apoptotic cells were also enhanced in epithelioid versus non-epithelioid granulomas. As a whole, the data suggest that co-infection of M. leprae-infected mice with BCG modulates TNF-alpha synthesis which, in turn, leads to induction of protective epithelioid granuloma formation in the foot pads and subsequent mycobacterial clearance. Macrophage differentiation into epithelioid cells, in association with the enhancement of TNF-alpha production at the granuloma site, may represent a triggering signal that induced apoptosis in these cells, leading to mycobacterial elimination. Moreover, the rate of apoptosis in epithelioid granulomas may well be related to the extent of immunopathologically mediated tissue damage.
Animals↗
Occurrence, selection and spread of resistance to antimicrobial agents used for growth promotion for food animals in Denmark.
UNLABELLED: 14.1 INTRODUCTION: This thesis is based on a number of monitoring and research programmes initiated at the Danish Veterinary Laboratory with the aim to determine the occurrence, selection and spread of resistance to antimicrobial agents used for growth promotion. The thesis gives a brief overview of the use, consumption, function and benefit of antimicrobial growth promoters and a more thorough description of the potential resistance problems arising by the use of these agents. 14.2 THE USE OF ANTIMICROBIAL AGENTS IN A HISTORICAL PERSPECTIVE: Soon after the introduction of antimicrobial agents for therapy of bacterial infections in humans and animals, the growth promoting effect of antimicrobial agents was observed, and since the beginning of the 1950'ties antimicrobial agents have been included in feed for food animals as a way to improve growth and reduce production costs. 14.3 CONSUMPTION OF ANTIMICROBIAL GROWTH PROMOTERS: Exact figures on the consumption of antimicrobial agents for clinical and growth promoting purposes are very difficult to get, and estimates are only available for a few countries. In Denmark, the total annual consumption of antimicrobial agents for growth promotion increased from 67 tonnes to 116 tonnes from 1989 to 1995. After the ban on avoparcin in 1995 the total consumption of growth promoters decreased to 94 tonnes. An increase up to 107 tonnes took place during 1996 and 1997, but during 1998, the consumption decreased to approximately 49 tonnes. The data that are available for different countries show that the use of antimicrobial agents for growth promotion normally equals or exceeds the usage of antimicrobial agents for therapy for food animals. Based on the information available, it can be estimated that the financial sale of antimicrobial agents for animals amounts to approximately 25% to 35% of the world-wide sale, of which the use of antimicrobial agents as feed additives is at least 50%. 14.4 MODE OF ACTION OF ANTIMICROBIAL GROWTH PROMOTERS: The mode of action of antimicrobial growth promoters is not fully understood. However, the main effects are believed to be a reduction of the growth of bacteria in the intestinal tract and thereby less microbial degradation of useful nutritients, and the prevention of infections with pathogenic bacteria. 14.5 BENEFIT FROM THE USE OF ANTIMICROBIAL GROWTH PROMOTERS: Numerous studies on the economic benefit of the use of antimicrobial growth promoters have been performed. The growth response is normally larger in young animals than in older animals. Large variations in the estimates have been observed, but in general a improvement in growth rate and feed utilisation has been observed. 14.6 SUSCEPTIBILITY AND RESISTANCE TO ANTIMICROBIAL GROWTH PROMOTERS: The definition of a bacterium as susceptible or resistant to an antimicrobial agent ultimately depends on clinical outcome. Since the exact mode of action of antimicrobial growth promoters are not known, the only way to define break points is based on the population distributions of susceptibilities to different agents. For antimicrobial agents used both for therapy and growth promotion the break points for therapy have been used. For avilamycin, avoparcin, flavomycin, monensin and salinomycin, that are used for growth promotion only, tentative break points based on population distributions have to be defined. The tentative break points for avoparcin and avilamycin have been confirmed by cross-resistance to other antimicrobial agents belonging to the same class and the presence of resistance mechanisms. 14.7 OCCURRENCE OF AND SELECTION FOR RESISTANCE TO ANTIMICROBIAL AGENTS USED FOR GROWTH PROMOTION: Information on the occurrence of resistance is needed to guide policy and detect changes that require intervention strategies. In 1995, a continuous monitoring of antimicrobial resistance in bacteria isolated from food animals was established in Denmark. Among food animals three categories of bacteria (indicator bacteria, zoonotic bacteria and animal pathogens) are continuously isolated from broilers, cattle and pigs and tested for susceptibility to antimicrobial agents used for therapy and growth promotion by disc diffusion or MIC-determinations. In all known cases antimicrobial resistance has emerged following the introduction of new antimicrobial compounds for therapy. The occurrence of resistance to antimicrobial agents used for growth promotion indicates that resistance will also emerge following the introduction of antimicrobials for growth promotion. Comparison of the occurrence of resistance among reservoirs with different usage of antimicrobial agents for growth promotion also shows that the occurrence of resistance will follow the usage. (ABSTRACT TRUNCATED)
Animal Husbandry↗
An outbreak of multidrug-resistant, quinolone-resistant Salmonella enterica serotype typhimurium DT104.
BACKGROUND: Food-borne salmonella infections have become a major problem in industrialized countries. The strain of Salmonella enterica serotype typhimurium known as definitive phage type 104 (DT104) is usually resistant to five drugs: ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline. An increasing proportion of DT104 isolates also have reduced susceptibility to fluoroquinolones. METHODS: The Danish salmonella surveillance program determines the phage types of all typhimurium strains from the food chain, and in the case of suspected outbreaks, five-drug-resistant strains are characterized by molecular methods. All patients infected with five-drug-resistant typhimurium are interviewed to obtain clinical and epidemiologic data. In 1998, an outbreak of salmonella occurred, in which the strain of typhimurium DT104 was new to Denmark. We investigated this outbreak and report here our findings. RESULTS: Until 1997, DT104 infections made up less than 1 percent of all human salmonella infections. The strain isolated from patients in the first community outbreak of DT104 in Denmark, in 1998 was resistant to nalidixic acid and had reduced susceptibility to fluoroquinolones. The outbreak included 25 culture-confirmed cases. Eleven patients were hospitalized, and two died. The molecular epidemiology and data from patients indicated that the primary source was a Danish swine herd. Furthermore, the investigation suggested reduced clinical effectiveness of treatment with fluoroquinolones. CONCLUSIONS: Our investigation of an outbreak of DT104 documented the spread of quinolone-resistant bacteria from food animals to humans; this spread was associated with infections that were difficult to treat. Because of the increase in quinolone resistance in salmonella, the use of fluoroquinolones in food animals should be restricted.
Abattoirs↗
The need for a veterinary antibiotic policy.
The international recognition of the 'stable to table' approach to food safety emphasises the need for appropriate and safe use of antibiotics in animal production. An appropriate use of antibiotics for food animals will preserve the long-term efficacy of existing antibiotics, support animal health and welfare and limit the risk of transfer of antibiotic resistance to humans. Furthermore, it may promote consumer confidence in the veterinary use of antibiotics. In advancing these arguments, the authors of this article argue that there is a need for a visible and operational policy for veterinary use of antibiotics, paying particular attention to the policies that are being developed in Denmark.
Animal Husbandry↗
Characterization of Staphylococcus simulans strains isolated from cases of bovine mastitis.
This study was conducted to characterize Staphylococcus simulans isolated from cases of bovine mastitis. A total of 134 isolates of S. simulans selected from 80 quarters from 61 cows or heifers in 37 different herds were characterized by EcoRI ribotyping. From 22 quarters two to seven consecutive isolates taken at weekly intervals were selected. Furthermore, three isolates from clinical infections in humans and two reference strains were included. A total of 16 different ribotypes were found, however, two types predominated. In most herds more than one type was found. From the 22 different quarters, where 76 paired or multiple isolates were at disposal, the same ribotype was constantly found in the same quarter. This study showed that S. simulans causing bovine mastitis could be divided into relatively large number of different types, but that two types predominated. More than one type could be found in the same herd and within different quarters of the same cow, but ribotyping confirmed that S. simulans could be the cause of persistent and stable infections.
Animals↗
Susceptibility testing of Actinobacillus pleuropneumoniae in Denmark. Evaluation of three different media of MIC-determinations and tablet diffusion tests.
This study was conducted to compare the applicability of three different media in sensitivity testing of Actinobacillus pleuropneumoniae by means of MIC and tablet diffusion tests. The media used were: modified PPLO agar, chocolatized Mueller-Hinton-II and Columbia agar supplemented with NAD. Seven antimicrobial agents were tested: ceftiofur, enrofloxacin, penicillin, spectinomycin, tiamulin, trimethoprim + sulfadiazine and tylosin, against 40 randomly selected A. pleuropneumoniae isolates. In general, good agreement was found between results obtained with all combinations of media, most antimicrobials tested and the two-test systems. Some variations between media were observed for spectinomycin, tiamulin and tylosin. For ceftiofur and trimethoprim + sulfadiazine some isolates with low MIC-values were classified as resistant using tablet diffusion, indicating that the break points of resistance for these antimicrobials using the tablet diffusion tests need adjustment. Using current break points for resistance with MIC-determinations, all isolates tested susceptible to ceftiofur, enrofloxacin, penicillin, tiamulin and trimethoprim + sulfadiazine. A larger number of isolates tested resistant to spectinomycin and tylosin on all three media using both MIC determinations and tablet diffusion.
Actinobacillus Infections↗
Presence of erm gene classes in gram-positive bacteria of animal and human origin in Denmark.
A classification of the different erm gene classes based on published sequences was performed, and specific primers to detect some of these classes designed. The presence of ermA (Tn554), ermB (class IV) and ermC (class VI) was determined by PCR in a total of 113 enterococcal, 77 streptococcal and 68 staphylococcal erythromycin resistant isolates of animal and human origin. At least one of these genes was detected in 88% of the isolates. Four isolates contained more than one erm gene. ermB dominated among the enterococci (88%) and streptococci (90%) and ermC among staphylococci (75%) with ermA (Tn554) present in some isolates (16%). Variations in the presence of the different genes when comparing staphylococcal isolates of human and animal origin were observed.
Animals↗
Association between the consumption of antimicrobial agents in animal husbandry and the occurrence of resistant bacteria among food animals.
Antimicrobial agents are used in food animals for therapy and prophylaxis of bacterial infections and in feed to promote growth. The use of antimicrobial agents for food animals may cause problems in the therapy of infections by selecting for resistance among bacteria pathogenic for animals or humans. The emergence of resistant bacteria and resistance genes following the use of antimicrobial agents is relatively well documented and it seems evident that all antimicrobial agents will select for resistance. However, current knowledge regarding the occurrence of antimicrobial resistance in food animals, the quantitative impact of the use of different antimicrobial agents on selection for resistance and the most appropriate treatment regimens to limit the development of resistance is incomplete. Surveillance programmes monitoring the occurrence and development of resistance and consumption of antimicrobial agents are urgently needed, as is research into the most appropriate ways to use antimicrobial agents in veterinary medicine to limit the emergence and spread of antimicrobial resistance.
Animals↗
The effects of antibiotic usage in food animals on the development of antimicrobial resistance of importance for humans in Campylobacter and Escherichia coli.
Modern food animal production depends on use of large amounts of antibiotics for disease control. This provides favourable conditions for the spread and persistence of antimicrobial-resistant zoonotic bacteria such as Campylobacter and E. coli O157. The occurrence of antimicrobial resistance to antimicrobials used in human therapy is increasing in human pathogenic Campylobacter and E. coli from animals. There is an urgent need to implement strategies for prudent use of antibiotics in food animal production to prevent further increases in the occurrence of antimicrobial resistance in food-borne human pathogenic bacteria such as Campylobacter and E. coli.
Animals↗
Glycopeptide resistance in Enterococcus faecium from broilers and pigs following discontinued use of avoparcin.
The use of the glycopeptide growth promoter avoparcin was discontinued in Denmark in 1995 following concerns that vancomycin-resistant Enterococcus faecium occurring as a result of its use could be transferred to humans via food. The present study is an analysis of results obtained by the continuous surveillance of an antimicrobial resistance in Denmark (DANMAP) with the aim of determining the effect of the ban on the occurrence of glycopeptide resistance among E. faecium isolated from broilers and pigs. Among isolates from broilers, the proportion that were resistant to glycopeptides has shown a statistically high significant decline between the end of 1995 and the first half of 1998, whereas in pigs the ban appears to have no such effect. One possible explanation is that the broiler industry generally uses all in-all out production compared with continuous production in pig herds. Alternatively, the results indicate that the different outcomes may result from different co-selection patterns in pigs and broilers. In pigs, the antimicrobials most commonly used favored co-selection of glycopeptide resistant strains of E. faecium while in broilers the antimicrobials most widely used selected for glycopeptide-susceptible strains. The results show that intervention to reduce antimicrobial resistance may not always be effective and preventing resistance problems therefore becomes essential.
Animals↗
Associations of Streptococcus suis serotype 2 ribotype profiles with clinical disease and antimicrobial resistance.
A total of 122 Streptococcus suis serotype 2 strains were characterized thoroughly by comparing clinical and pathological observations, ribotype profiles, and antimicrobial resistance. Twenty-one different ribotype profiles were found and compared by cluster analysis, resulting in the identification of three ribotype clusters. A total of 58% of all strains investigated were of two ribotypes belonging to different ribotype clusters. A remarkable relationship existed between the observed ribotype profiles and the clinical-pathological observations because strains of one of the two dominant ribotypes were almost exclusively isolated from pigs with meningitis, while strains of the other dominant ribotype were never associated with meningitis. This second ribotype was isolated only from pigs with pneumonia, endocarditis, pericarditis, or septicemia. Cluster analysis revealed that strains belonging to the same ribotype cluster as one of the dominant ribotypes came from pigs that showed clinical signs similar to those of pigs infected with strains with the respective dominant ribotype profiles. Furthermore, strains belonging to different ribotype clusters had totally different patterns of resistance to antibiotics because strains isolated from pigs with meningitis were resistant to sulfamethazoxazole and strains isolated from pigs with pneumonia, endocarditis, pericarditis, or septicemia were resistant to tetracycline.
Animals↗
Experimental infection of pregnant cows with Bacillus licheniformis bacteria.
To study the abortifacient potential and fetoplacental tropism of Bacillus licheniformis bacteria, eight cows in the sixth to eighth month of gestation were inoculated intravenously either once (n = 4) or on four successive days (n = 4) with B. licheniformis at doses ranging from 10(9) to 10(12) colony-forming units. Cows were euthanatized and necropsied prior to abortion (n = 2), at the time of abortion (n = 2), or at calving (n = 4). Live-born calves (n = 5) were euthanatized immediately after delivery and necropsied. B. licheniformis was reisolated from placentomes/endometrium in six of eight (75%) cows and from one fetus aborted 43 days after inoculation. Lesions associated with B. licheniformis were restricted to the pregnant uterus, with the exception of one cow, which developed pneumonia. Necrosis in the fetal compartment of the placenta were present in three of four (75%) cows of both inoculation groups. Lesions were mainly restricted to fetal membranes and especially to the fetal side of the placentomes. Necrosis and diffuse neutrophil infiltrations of both villi and intervillous areas occurred in the fetal part of the placenta, and the placentomal interface was distended by bacteria, neutrophils, erythrocytes, and debris. Within trophoblasts, bacteria were located both free in the cytoplasm and in cytoplasmatic vesicles. Inflammation was present in three of eight (38%) calves. Placental and fetal lesions were similar to those found in cases of spontaneous abortions associated with B. licheniformis. The abortifacient potential of B. licheniformis and the tropism for the bovine placenta is demonstrated here for the first time.
Abortion, Veterinary↗
Effect of the injection of an extract of Ascaris suum on macrophage activation during the early phase of Mycobacterium bovis BCG infection in C57Bl/6 mice.
Injection of an Ascaris suum extract (Asc) affects both the humoral and cellular immune responses to unrelated antigens when it is co-administered with these antigens. In the present study we evaluated the effect of Asc on macrophage activation in the early phase of Mycobacterium bovis BCG (Pasteur strain TMCC 1173) infection in C57Bl/6 mice. C57Bl/6 mice were injected intraperitoneally (ip) with 0.1 mg BCG (BCG group) or BCG plus 1 mg Asc (BCG + Asc group). The peritoneal exudates were obtained at 2, 7 and 14 days after infection. The numbers of IFN-gamma-secreting cells were assessed by the ELISPOT assay. Nitric oxide (NO) production was measured by the Griess method and by the evaluation of NADPH diaphorase activity in the peritoneal exudates. The administration of Asc extract increased NADPH diaphorase activity (2 days: control = 0, BCG = 7%, BCG + Asc = 13%, and Asc = 4%; 7 days: control = 4, BCG = 13%, BCG + Asc = 21%, and Asc = 4.5%) and TNF-alpha levels (mean +/- SD; 2 days: control = 0, BCG = 169 +/- 13, BCG + Asc = 202 +/- 37, and Asc = 0; 7 days: control = 0, BCG = 545 +/- 15.5, BCG + Asc = 2206 +/- 160.6, and Asc = 126 +/- 26; 14 days: control = 10 +/- 1.45, BCG = 9 +/- 1.15, BCG + Asc = 126 +/- 18, and Asc = 880 +/- 47.67 pg/ml) in the early phase of BCG infection. Low levels of NO production were detected at 2 and 7 days after BCG infection, increasing at 14 days (mean +/- SD; 2 days: control = 0, BCG = 3.7 +/- 1.59, BCG + Asc = 0.82 +/- 0.005, Asc = 0.48 +/- 0.33; 7 days: control = 0, BCG = 2.78 +/- 1.54, BCG + Asc = 3.07 +/- 1.05, Asc = 0; 14 days: control = 0, BCG = 9.05 +/- 0.53, BCG + Asc = 9.61 +/- 0.81, Asc = 10.5 +/- 0.2 (2 x 10(6)) cells/ml). Furthermore, we also observed that Asc co-injection induced a decrease of BCG-colony-forming units (CFU) in the spleens of BCG-infected mice during the first week of infection (mean +/- SD; 2 days: BCG = 1.13 +/- 0.07 and BCG + Asc = 0.798 +/- 0.305; 7 days: BCG = 1.375 +/- 0. 194 and BCG + Asc = 0.548 +/- 0.0226; 14 days: BCG = 0.473 +/- 0.184 and BCG + Asc = 0.675 +/- 0.065 (x 10(2)) CFU). The present data suggest that Asc induces the enhancement of the immune response in the early phase of BCG infection.
Animals↗
Frequency of alpha- and beta-haemolysin in Staphylococcus aureus of bovine and human origin. A comparison between pheno- and genotype and variation in phenotypic expression.
The phenotypic expression of haemolysins and the presence of genes encoding alpha and beta-haemolysin were determined in 105 Staphylococcus aureus isolates from bovine mastitis, 100 isolates from the nostrils of healthy humans, and 60 isolates from septicaemia in humans. Furthermore, the possible change in expression of haemolysins after subcultivation in human and bovine blood and milk was studied in selected isolates. Alpha-haemolysin was expressed phenotypically in 39 (37%) of the bovine isolates, in 59 (59%) of the human carrier isolates, and in 40 (67%) of the isolates from septicaemia. Beta-haemolysin was expressed in 76 (72%) bovine, 11 (11%) carrier, and 8 (13%) septicaemia isolates. Significantly more bovine than human isolates expressed beta-haemolysin and significantly fewer expressed alpha-haemolysin. Genotypically, the gene encoding alpha-haemolysin was detected in all isolates. A significant difference in the prevalence of the gene encoding beta-haemolysin between the bovine (96%), human carrier (56%) and isolates from septicaemia (57%) was found. Of the bovine isolates, 75% of those carrying the gene encoding beta-haemolysin expressed beta-haemolysin phenotypically, whereas only 20% of the carrier isolates and 24% of the septicaemia isolates did so. No change in expression of haemolysins could be observed after subcultivation of bovine isolates in human blood and milk. After 5 to 10 subcultures in bovine blood and 1 to 4 in bovine milk, 9 of 10 human isolates originally phenotypically beta-haemolysin negative initiated the expression of beta-haemolysin. This study showed that a larger proportion of S. aureus of bovine origin carry the beta-haemolysin gene compared to isolates from humans. Furthermore, a larger number of the isolates of bovine origin carrying the beta-haemolysin gene express this gene phenotypically compared to isolates of human origin.
Animals↗
Transfer of antibiotic resistant bacteria from animals to man.
Antibiotic resistance develops in zoonotic bacteria in response to antibiotics used in food animals. A close association exists between the amounts of antibiotics used and the levels of resistance observed. The classes of antibiotics routinely used for treatment of human infections are also used for animals either for therapy or for growth promotion. Antibiotic resistance in zoonotic bacteria constitute a public health hazard, primarily through the increased risk of treatment failures. This paper describes the zoonotic bacteria, salmonella, campylobacter, yersinia and entero-haemorrhagic E. coli (EHEC). Infections with these agents do not generally require antibiotic therapy, but in some cases antibiotics are essential to obtain a successful cure. The levels and types of resistance observed in zoonotic bacteria in some countries, especially the increasing levels of fluoroquinolone resistance in salmonella and campylobacter, gives cause for concern. The principles of controlling resistance development involve infection control at herd level and prudent use of antibiotics.
Animals↗
Design of a system for monitoring antimicrobial resistance in pathogenic, zoonotic and indicator bacteria from food animals.
DANMAP is a Danish programme for integrated monitoring of and research on antimicrobial resistance in bacteria from food animals, food and humans. The paper describes how bacteria from broilers, pigs, and cattle are collected, as well as the procedures for data handling and presentation of results. The bacteria from animals include certain pathogens, selected so that they are representative for submissions to Danish diagnostic laboratories, as well as zoonotic bacteria (Campylobacter, Salmonella and Yersinia) and indicator bacteria (E. coli, E. faecium and E. faecalis), from samples collected at abattoirs. The latter samples are selected so that they are representative of the respective animal populations. Therefore, the apparent prevalence of antimicrobial resistance in the populations may be calculated. The isolates are identified to species level and the results of susceptibility testing are stored as continuous variables. All isolates are maintained in a strain collection so that they are available for subsequent research projects. The data handling facilities makes it possible to present results as percent resistant isolates or as the apparent prevalence of resistance in the population, or alternatively as graphical distributions of mm inhibition zones or MIC values. Computer routines have been established that make it possible to detect specific phenotypic expressions of resistance that may be of particular interest.
Animals↗
Effects of the antimicrobial growth promoter tylosin on subclinical infection of pigs with Salmonella enterica serotype Typhimurium.
OBJECTIVE: To determine whether feeding tylosin, an antimicrobial growth promoter, to pigs was associated with increased risk of infection with and excretion of Salmonella enterica serotype Typhimurium. ANIMALS: 17 healthy pigs. PROCEDURE: A commercial pelleted dry feed was given in 2 feeding trials. In trial A, 11 pigs were given feed with tylosin, 11 pigs were given feed without tylosin, and 11 pigs were given feed with tylosin before and feed without tylosin after inoculation with S Typhimurium. In trial B, 44 pigs were given feed that contained tylosin, and 44 pigs were given feed without tylosin. Three weeks after the start of each trial, pigs were orally inoculated with approximately 5 x 10(6) colony-forming units of S Typhimurium. Feces were examined for S Typhimurium, using semiquantitative microbiologic techniques before and for 5 or 6 weeks after inoculation. Serum antibody titers against S enterica were measured by use of ELISA. RESULTS: None of the pigs developed clinical signs of salmonellosis. However, after inoculation, S Typhimurium was isolated from feces of most pigs, and all but 2 pigs developed serum antibodies against S enterica. Significant differences were not detected between experimental and control groups in either trial. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that tylosin fed as an antimicrobial growth promoter to pigs may not be an important factor in promoting infection with or excretion of S enterica serotype Typhimurium.
Animal Feed↗