PubMed · 13254137
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1955-05-22. [Chlorocid].. https://pubmed.ncbi.nlm.nih.gov/13254137/
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The extensive use of chloramphenicol (CAP) in livestock leads the accumulation of CAP in livestock manures, threatening environmental and human health. Therefore, eliminating or reducing CAP concentration in manures before its re-utilization and application through microbial remediation is necessary. Exiguobacterium sp. CAP4, isolated from the plastisphere in duck manures, was capable of degrading CAP with the biodegradation efficiency of 97.8 % at initial CAP concentration of 5 mg/L within 4 days. A total of twenty-four biotransformation products were determined, including two novel transformation products, TP166 and TP203, enriched the integrity of CAP biodegradation pathways. Furthermore, the biotransformation process was proposed as a detoxifying process through biotransformation products toxicity evaluation. Notably, Exiguobacterium sp. CAP4 successfully colonized in the cow manures after inoculation, and bioaugmented the biodegradation of CAP in virgin cow manures. This study significantly extended our understanding of the CAP biotransformation fate, and provided a promising bacterial strain for bioremediation of CAP containing wastewater in situ.
OBJECTIVE: To explore the possibility of phenotypic conversion of clinical chloromycetin (Cm)-resistant isolates of E.coli to drug-sensitive ones with external guide sequences (EGS) in vitro. METHODS: Recombinant EGS plasmids directed against Cm acetyl transferase (cat) and containing kanamycin (Km) drug-resistance gene and control plasmids only containing kanamycin-resistance gene without EGS were constructed. By using CaCl(2) method, the recombinant plasmids were introduced into the clinically isolated Cm-resistant E.coli strains. Extraction of plasmids and PCR were applied to identify the EGS positive clones; The growth rate in liquid broth culture of Cm-resistant bacteria after EGS containing plasmid transformation was determined by spectrophotometer A(600). Drug sensitivity was tested in solid culture by using KB method. RESULTS: Transformation studies were carried out on 16 clinically isolated Cm-resistant E.coli strains with pEGFP-C1-EGS + cat1 + cat2 recombinant plasmid. Transformants were screened on LB-agar plates containing Km after transformation using EGS. In 4 tested strains of them, transformants with specific EGS plasmid showed growth inhibition when grown in liquid broth culture containing 100 approximately 200 micro g/ml of Cm. They were sensitive to Cm on LB-agar plates containing 100 approximately 200 micro g/ml of Cm in drug-sensitivity test. Extraction of plasmids showed the existence of EGS bands. PCR amplified products of EGS. The above facts indicated that the 4 strains out of the 16 clinical isolates had been converted to drug-sensitive phenotype, and Cm-resistant clinically isolated E. coli resumed sensitivity to Cm. CONCLUSION: EGS has the capability of converting the phenotype of clinical drug-resistant isolates to drug sensitivity.
A method based on liquid chromatography-tandem mass spectrometry was developed and validated for the qualitative and quantitative detection of chloramphenicol (CAP) in seafood samples. The analysis of CAP residues in seafood is important because CAP can cause serious acute reactions in humans, including aplastic anemia and leukemia. The proposed methodology includes a cleanup solid-phase extraction procedure with high recovery efficiency (>90%). Chromatographic separation of CAP and the internal standard (IS) was carried out on a C(18) column, followed by mass spectrometric detection using electrospray ionization in the negative-ion mode. The precursor/product ion transitions 321-->257 (CAP) and 354-->290 (IS) were monitored. Statistical evaluation of this multiple reaction monitoring mass spectrometric procedure reveals good linearity, accuracy, and inter- and intraday precisions. The limit of detection was 0.1 ng/mL, and the limit of quantification for CAP in seafood samples is 0.02 microg/kg. Application in seafood samples allowed the detection of CAP in low parts per billion levels.