• Asian-Australasian Journal of Animal Sciences
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• v.20 no.6
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• pp.1007-1014
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• 2007

Acceptance of antibiotic growth promoters (AGP) in agricultural animal production is rapidly disappearing. Both government regulations and consumer preference are driving this change. Producers in any country that seek export markets will be forced to give up AGP if they are to sell to the EU and many other markets. This report will first review the history of AGP use in the animal industry and the concerns about development of antimicrobial resistance. A description of the development and structure of the gut and how it is affected by AGP administration will conclude with results of studies to replace AGP with antimicrobial organic acids.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.3
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• pp.248-253
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• 2005

AfsR2, originally identified from Streptomyces lividans, is a global regulatory protein which stimulates antibiotic biosynthesis. Through its stable chromosomal integration, the high level of gene expression of afsR2 significantly induced antibiotic production as well as the sporulation of S. lividans, implying the presence of yet-uncharacterized AfsR2-target proteins. To identify and evaluate the putative AfsR2-target proteins involved in antibiotic regulation, the proteomics-driven approach was applied to the wild-type S. lividans and the afsR2-integrated actinorhodin overproducing strain. The 20 gel-electrophoresis gave approximately 340 protein spots showing different protein expression patterns between these two S. lividans strains. Further MALDI-TOF analysis revealed several AfsR2-target proteins, including glyceraldehyde-3-phosphate dehydrogenase, putative phosphate transport system regulator, guanosine penta phosphate synthetase/polyribonucleotide nucleotidyltransferase, and superoxide dismutase, which suggests that the AfsR2 should be a pleiotropic regulatory protein which controls differential expressions of various kinds of genes in Streptomyces species.

• Applied Biological Chemistry
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• v.31 no.4
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• pp.371-375
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• 1988

Streptomycetes are attractive microorganisms for their production of various secondary metabolites such as antibiotics. Now, the development of gene manipulation in this microorganisms enables the cloning and analysis of the genes which coding for antibiotic biosynthesis and resistance to the drug. In this article, we reviewed the studies with respect to the mechanisms of self-protection and cloning of the genes cloning for antibiotic biosynthesis, particularly, in microorganisms which produce antibiotic inhibitors of protein synthesis.

• Asian-Australasian Journal of Animal Sciences
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• v.9 no.1
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• pp.27-30
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• 1996

One thousand eight hundreds and twenty two samples of raw milk were detected for antibiotic residues using Bacillus subtilis ATTCC 6633, B. stearothermophilus var. calidolactis C 593 and Micrococcus luteus ATCC 9341 as test organisms, were carried out from July 1991 through June 1992. Apparent antibiotic residues were found through out the study period, except in January. The detection rate varied from 0.7% in March and May to 11% in April. One hundred and thirty six (72%) samples of the 187 screening positive samples were considered to contain only the indigenous antimicrobial agents. Of the total, 51 (2.8%) samples were positive for antibiotic residues. Among the tested organisms, B. stearothermophilus var. calidolactis was the most sensitive organism in detection of the antibiotic residues.

• Journal of Microbiology and Biotechnology
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• v.7 no.6
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• pp.402-408
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• 1997

The antibiotic-producing strain HW-003 was screened from soil and found to be effective against the multidrug-resistant Staphylococcus aureus. The spore chain of HW-003 was retinaculiaperti, and the spore surface was spiny. Strain HW-003 has a LL-diaminopimelic acid isoform in the cell wall. The aerial mass color of the strain was gray, and the reverse side was yellow-brown. The strain produced melanin, but did not produce soluble pigments. According to the Taxon program, HW-003 showed best match with Streptomyces cyaneus. Antibiotic production reached a maximum after 72-h cultivation. The antibiotic was purified with silica gel column chromatography, octadecylsilyl column chromatography, and HPLC. The purified antibiotic, AMRSA1, showed strong inhibitory activity against multidrug-resistant Staphylococcus aureus and gram-positive bacteria. The molecular weight of AMRSA1 was about 1, 100. AMRSA1 was a peptide antibiotic containing alanine and serine.

• Journal of Environmental Health Sciences
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• v.32 no.5 s.92
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• pp.462-468
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• 2006

Antibiotics are manufactured and used for specific physiological functions, hence they may exert adverse ecological consequences when they are in contact with nontarget organisms. In the last decade, many reports have been made on the occurrences of various antibiotic compounds in surface water, and their potential impact to the environment has become an increasing concern. This study was conducted to prioritize antibiotic substances with potential environment risk in Korea. Human use antibiotics with an EIC (Expected Introduction Concentration) value greater than $1{\mu}g/l$, US FDA's action limit criteria, were selected. In order to calculate a worst-case EIC for each substance, annual production volume (in kg) of each antibiotic substance was derived using the Korea Pharmaceutical Manufacturers Association (KPMA)'s monetary database. Sixteen substances were preliminarily selected. The EICs of the 16 antibiotic substances were refined with the excretion rate of the parent substances. Ten antibiotic substances were identified to have EIC-corrected greater than $1{\mu}g/l$, which include Amoxicillin ($15.8{\mu}g/l$), Cefaclor ($10.1{\mu}/l$), Roxithromycin ($4.2{\mu}g/l$), Cephradine ($4.5{\mu}g/l$), Cefatrizine ($2.6{\mu}g/l$), Cefadroxil ($3.3{\mu}g/l$), Aztreonam ($2.3{\mu}g/l$), Ceftazidime ($2.8{\mu}g/l$), Ribostamycin ($1.3{\mu}g/l$), and Ceftezole ($1.3{\mu}g/l$). Additional risk assessments for these antibiotic substances are suggested.

• Journal of Microbiology and Biotechnology
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• v.24 no.9
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• pp.1226-1231
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• 2014

The rare actinomycete Pseudonocardia autotrophica was previously shown to produce a solubility-improved toxicity-reduced novel polyene compound named $\underline{N}ystatin$-like $\underline{P}seudonocardia$ $\underline{P}olyene$ (NPP). The low productivity of NPP in P. autotrophica implies that its biosynthetic pathway is tightly regulated. In this study, $wblA_{pau}$ was isolated and identified as a novel negative regulatory gene for NPP production in P. autotrophica, which showed approximately 49% amino acid identity with a global antibiotic down-regulatory gene, wblA, identified from various Streptomycetes species. Although no significant difference in NPP production was observed between P. autotrophica harboring empty vector and the S. coelicolor wblA under its native promoter, approximately 12% less NPP was produced in P. autotrophica expressing the wblA gene under the strong constitutive $ermE^*$ promoter. Furthermore, disruption of the $wblA_{pau}$ gene from P. autotrophica resulted in an approximately 80% increase in NPP productivity. These results strongly suggest that identification and inactivation of the global antibiotic down-regulatory gene wblA ortholog are a critical strategy for improving secondary metabolite overproduction in not only Streptomyces but also non-Streptomyces rare actinomycete species.

• Journal of Microbiology and Biotechnology
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• v.26 no.2
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• pp.241-247
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• 2016

Natamycin is a widely used antifungal antibiotic. For natamycin biosynthesis, the gene pimE encodes cholesterol oxidase, which acts as a signalling protein. To confirm the positive effect of the gene pimE on natamycin biosynthesis, an additional copy of the gene pimE was inserted into the genome of Streptomyces gilvosporeus 712 under the control of the ermE* promoter (p_ermE*) using intergeneric conjugation. Overexpression of the target protein engendered 72% and 81% increases in the natamycin production and cell productivity, respectively, compared with the control strain. Further improvement in the antibiotic production was achieved in a 1 L fermenter to 7.0 g/l, which was a 153% improvement after 120 h cultivation. Exconjugants highly expressing pimE and pimM were constructed to investigate the effects of both genes on the increase of natamycin production. However, the co-effect of pimE and pimM did not enhance the antibiotic production obviously, compared with the exconjugants highly expressing pimE only. These results suggest not only a new application of cholesterol oxidase but also a useful strategy to genetically engineer natamycin production.

• Food Science of Animal Resources
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• v.37 no.2
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• pp.264-273
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• 2017

The aim of this study was to investigate the effects of production systems and milk collection periods on the somatic cell count (SCC), some microbiological properties, total aerobic mesophilic bacteria (TAMB), coliform, Staphylococcus aureus (S. aureus), yeast and mould) and antibiotic residue of milk; in Turkey. Milk samples were collected from 9 conventional farms and 9 organic farms during one year time, at six different months (December 2013 to October 2014), and all farms were selected from the same geographical locations. All organically managed farms had organic production certificates given by the Republic of Turkey Ministry of Food, Agriculture and Livestock. The count of TAMB, coliform, and coagulase positive S. aureus were affected by production systems at the level of p<0.01; yeast and mold, and somatic cell count (SCC) were affected at the level of p<0.05. But, differences according to months were statistically significant only on TAMB (p<0.01) and coliform (p<0.05) counts. The general means of TAMB, coliform and yeast and mould counts of the organic milk (OM) were significantly lower (p<0.05), while the general means of SCC and coagulase positive S. aureus count of the OM was significantly higher (p<0.05) compared to conventional milk (CM). Antibiotic residue was determined in one of the CM sample and in two of the OM samples. Our study is the first research that compared conventional and organic milk in Turkey. This study indicated that the microbiological quality of OM was the higher in terms of TAMB, coliform and yeast and mould, whereas was the lower in relation to SCC and coagulase positive S. aureus counts. But, the quality of both milk types should be improved.

• Korean Journal of Veterinary Research
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• v.55 no.3
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• pp.191-197
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• 2015

Escherichia (E.) coli is commensal bacteria found in the intestine; however, some pathogenic strains cause diseases in animals and humans. Although E. coli does not typically produce hydrogen sulfide ($H_2S$), $H_2S$-producing strains of E. coli have been identified worldwide. The relationship between virulence and $H_2S$ production has not yet been determined. Therefore, characteristics of $H_2S$-producing isolates obtained from swine feces were evaluated including antibiotic resistance patterns, virulence gene expression, and genetic relatedness. Rates of antibiotic resistance of the $H_2S$-producing E. coli varied according to antibiotic. Only the EAST1 gene was detected as a virulence gene in five $H_2S$-producing E. coli strains. Genes conferring $H_2S$ production were not transmissible although the sseA gene encoding 3-mercaptopyruvate sulfurtransferase was detected in all $H_2S$-producing E. coli strains. Sequences of the sseA gene motif CGSVTA around Cys238 were also identical in all $H_2S$- producing E. coli strains. Diverse genetic relatedness among the isolates was observed by pulsed-field gel electrophoresis analysis. These results suggested that $H_2S$-producing E. coli strains were not derived from a specific clone and $H_2S$ production in E. coli is not associated with virulence genes.