Chlortetracycline residues in the meat of slaughter calves in relation to transmissible microbial resistance to antibiotics

The occurrence of chlortetracycline residues in the meat of slaughter calves in 62% herds under study (the additive of the medicated premix AUREOVIT to feed without observing the withdrawal times) did not influence significantly the Gram-negative resistant and R+ microflora isolated from the same material, in comparison with control herds that were administered no antibiotics. Neither was the spectrum of donors and transferring R plasmids influenced significantly nor the incidence of different resistance determinants. The effect of chlortetracycline addition to feed was negative (at P = 0.05) only in the occurrence of R+ microflora isolated from stable environment where the slaughtered calves had been housed.     

基于药效和作用机制拮抗的防耐药性新策略研究

1 基于新型PK/PD的MSW理论及其防耐药用药策略 1.1防细菌耐药突变体选择浓度和突变选择窗最小防突变浓度(MPC)是指抑制细菌耐药突变体被选择性富集扩增所需的最低抗菌药物浓度.     

The situation concerning antibiotic resistance from the viewpoint of the bacteriologist

Already fifty years ago, when antibiotics were introduced, their effectiveness was challenged by certain bacteria which had the ability to resist the bacteriocidal effect of the antibiotics. Development of such resistance is due to selection pressure that results from the use of antibiotics in therapy, particularly in human medicine. In Switzerland, the veterinary public health aspect of this problem has become of current interest. The ban on the use of growth promoters has triggered the need for an update of the statistical information on the phenomena of resistance and the setting up of a surveillance system of antibioresistance in animals and in products of animal origin.     

The occurrence and antibiotic resistance of motile Aeromonas in livestock

The present study was carried out to assess the prevalence of motile Aeromonas spp. in the faeces of clinically healthy sheep, cattle and horses and evaluate their susceptibility to some anti-microbial agents. Rectal swabs from 120 sheep, 85 cattle and 20 horses were examined for Aeromonas species using alkaline peptone water (pH 8.4) as the enrichment medium and Aeromonas Selective Agar containing 5 mg/l ampicillin as the isolation medium. Identification and antibiotic resistance of motile Aeromonas strains was performed using Gram Negative Enteric ID panel. Motile aeromonads were isolated from 12 (10%) sheep, 7 (8.2%) cattle and 1 (5%) horse. Of these 20 aeromonad isolates, 13 were A. caviae, 6 were A.sobria and 1 was A. hydrophila. Aeromonas species in the faeces of livestock might pose a public health problem for humans who are in direct contact with contaminated animals. However, further studies should be performed on aeromonads relating to their transmission between animals and humans.     

Homologies between the major histocompatibility complex of man and cattle: consequences for disease resistance and susceptibility

The major histocompatibility complex (MHC) of mammals contains a large number of mostly duplicated genes. In the HLA system (the MHC of man), which is by far the best-studied major histocompatibility system so far, roughly 20 genes have been defined and mapped. They code for three classes of proteins: HLA-A, -B and -C (Class I), HLA-DP, -DQ and -DR (Class II) and serum complement components C2, C4 and Bf (Class III). Furthermore, the region contains genes for 21-hydroxylase (21-OH) and tumor necrosis factor (TNF). The MHC thus forms a chromosomal segment containing several clusters of genes of only partially defined biological significance, but ondoubtedly playing a role in disease susceptibility. In view of the recently obtained structural information on BoLA, the MHC of cattle, it is hypothesized that susceptibility to diseases in cattle is associated with BoLA in the same way as human diseases. Finally, new technical and conceptual developments in the field of MHC research and their application to the BoLA system are discussed.     

The antibiotic resistance of pathogenic staphylococci and streptococci isolated from dogs

The antibiotic resistance of strains of Staphylococcus aureus and beta–haemolytic streptococci of canine origin were assessed against eight drugs using the disc diffusion technique. Of 398 strains of Staph, aureus eight were resistant to neomycin, 15 to ampicillin, 23 to lincomycin, while of 87 streptococci, one was resistant to ampicillin, two to lincomycin and four to penicillin. In addition 4 of 340 Staph, aureus strains tested against cloxacillin were resistant.     

新媒体营销在饲料企业中的应用探究

新媒体伴随着互联网技术和数字技术而产生,新媒体营销使众多实体企业步入新媒体营销领域.在网络化时代的快速发展背景下,新媒体营销为饲料企业的产品营销提供了一个全新的发展路径,加上新冠疫情对营商环境带来的致命打击,新媒体营销更是彰显了独特的活力.在当下复杂的发展环境中,饲料企业唯有充分利用新媒体营销平台,抓住新媒体平台提供的...     

Identification and characterization of rat intestinal lamina propria cells: consequences of microbial colonization.

Germ-free (GF) animals exhibit an abnormally diminished, cell-mediated immune response which can be rapidly normalized by bacterial colonization of the intestine. This conventionalization suggests that the development and/or regulation of the immune system is dependent upon intestinal bacteria or their products. Here we consider the ontogeny of gut-associated lymphoid tissue (GALT) immunocytes by isolating and characterizing the intestinal lamina propria cells (LPC) of GF rats responding to bacterial colonization or an irrelevant protein antigen, and compared to LPC of specific pathogen-free (SPF) rats which were conventionalized (CV) from birth. Isolation of cells was accomplished by successive EDTA washings of small intestine to remove the epithelium, and enzymatic digestion of the tissue generating single-cell suspensions. Resulting cell suspensions were characterized by monoclonal antibodies directed against leukocyte epitopes using flow cytometry. Functional characterization was measured by the tritiated thymidine proliferation assay with concanavalin A (Con A) and lipopolysaccharide (LPS) as co-stimulators. Germ-free and SPF rats had fewer total LPC than CV rats. Antibody staining revealed that GF rats had fewer total leukocytes than CV and SPF rats, and that CV rats had a greater percentage of T-cells and cells positive for the C3 receptor than GF rats. Co-stimulation of LPC with mitogens only increased proliferation of cells from CV rats compared to GF and SPF rats. In addition, spleen cells from CV rats demonstrated significantly enhanced proliferative responses compared to spleen cells from GF rat and were more analogous to spleen cells from SPF rats in their ability to proliferate in vitro, with and without mitogens. We conclude that T-cells and CD35-positive (C3BR+) cells are recruited and/or proliferate in response to intestinal bacteria and/or their products, and that this results in the induction of immune competency.     

Salmonella spp. in Bavarian liquid pig manure: occurrence and relevance for the distribution of antibiotic resistance

In a representative study, 380 manure samples of pig farms distributed all over Bavaria (Germany) were screened for the presence of Salmonella spp. at the time of manure application to soil using methods adapted to DIN EN ISO 6579. The isolates were tested according to DIN 58940 for their susceptibility towards 26 antimicrobial substances - such substances partly administered in animals, but mainly used in human therapy. Six out of 380 manure samples and, in addition, the only separated liquid manure sample examined, contained Salmonella isolates. Serotypes represented S. Typhimurium (n = 5), S. Derby (n = 1) and S. Infantis/S. Serogroup C1-(6,7:r:-)-form (each n = 1). Within the serovar S. Typhimurium, the most common phage type was DT104 (n = 3). All Salmonella isolates originated from 'big' farms (>30/45 sows on combined/breeding farms or >220 fattening pigs). Four out of six manure samples contained resistant isolates; all resistant Salmonellae were multi-resistant. Two out of three DT104-isolates showed the typical penta-resistance pattern often found in S. Typhimurium DT104, which was, furthermore, supplemented by other resistances. One Escherichia coli isolated together with a phage type DT104 S. Typhimurium also expressed the same penta-resistance pattern.     

Influence of oral antibiotics on resistance and enterotoxigenicity of Escherichia coli.

Three groups of five piglets were formed and 1390 Escherichia coli isolates were obtained during the 45-day period of observation. One of the groups received feed without antibiotic whereas the second received feed containing 100 ppm neomycin and the third feed with 100 ppm neomycin plus 100 ppm tetracycline. Rectal swabbings for bacterial isolation were repeated ten times, twice during an adaptation period and eight times during the treatment period. Resistance among the isolates to tetracycline, streptomycin and triple sulfas remained high throughout this experiment whereas resistance to neomycin, chloramphenicol and ampicillin were found to increase significantly under the influence of antibiotic supplemented feed. This increase of antibiotic resistance was associated with an increase of the percentage of isolates harboring an R. factor. When comparing the ability of strains harboring an R factor to receive the plasmid Ent from the E. coli K12 (P155) with isolates not harboring such a plasmid, no significant difference was observed in their ability to receive the Ent plasmid.