Three kinds of plasmid-mediated quinolone resistance (PMQR) determinants have been discovered and have been shown to be widely distributed among clinical isolates: qnr genes, aac(6 ′ )-Ib-cr , and qepA . Few data on the prevalence of these determinants in strains from animals are available. The presence of PMQR genes in isolates from animals was determined by PCR amplification and DNA sequencing. The production of extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases in the strains was detected, and their genotypes were determined. The genetic environment of PMQR determinants in selected plasmids was analyzed. All samples of ceftiofur-resistant (MICs ≥ 8 μg/ml) isolates of the family Enterobacteriaceae were selected from 36 companion animals and 65 food-producing animals in Guangdong Province, China, between November 2003 and April 2007, including 89 Escherichia coli isolates, 9 Klebsiella pneumoniae isolates, and isolates of three other genera. A total of 68.3% (69/101) of the isolates produced ESBLs and/or AmpC β-lactamases, mainly those of the CTX-M and CMY types. Of the 101 strains, PMQR determinants were present in 35 (34.7%) isolates, with qnr, aac(6 ′ )-Ib - cr , and qepA detected alone or in combination in 8 (7.9%), 19 (18.8%), and 16 (15.8%) strains, respectively. The qnr genes detected included one qnrB4 gene, four qnrB6 genes, and three qnrS1 genes. Five strains were positive for both aac(6 ′ )-Ib - cr and qepA , while one strain was positive for qnrS1, aac(6 ′ )-Ib - cr , and qepA. qnrB6 was flanked by two copies of IS CR1 with an intervening dfr gene downstream and sul1 and qacE Δ 1 genes upstream. In another plasmid, aac(6 ′ )-Ib-cr followed intI1 and arr-3 was downstream. PMQR determinants are highly prevalent in ceftiofur-resistant Enterobacteriaceae strains isolated from animals in China. This is the first report of the occurrence of PMQR determinants among isolates from companion animals.

Colorectal cancer (CRC) is one of the most common types of cancers in humans and is closely linked to the global cancer-related mortalities worldwide. Molecular pathological epidemiology studies can reveal the risk factors of CRC and contribute to biomarker research and precision medicine. The current clinical treatment for CRC mainly involves surgery and chemotherapy. However, because of the occurrence of side effects and the emergence of drug resistance, there is an urgent need to find new and more effective drugs for CRC treatment. An increasing number of studies have demonstrated that many natural products possess effective anti-CRC effects and may serve as alternative chemotherapy agents for CRC treatment. In this review, we summarize the natural products with anti-CRC effects from different sources based on the chemical structures such as alkaloids, polysaccharides, polyphenols, terpenoid, unsaturated fatty acids, and discuss the natural product-derived drugs used clinically for colorectal cancer treatment. Furthermore, natural products of marine origin are also discussed for their enormous potential to serve as the candidate drugs. Notably, we generalize the experiment-based molecular mechanisms and the regulatory networks whereby natural products exert anticancer effects on cell proliferation, metastasis, apoptosis, autophagy, and angiogenesis.

Tuberculosis remains one of the world’s deadliest communicable diseases, novel anti-tuberculosis agents are urgently needed due to severe drug resistance and the co-epidemic of tuberculosis/human immunodeficiency virus. Here, we show the isolation of six anti-mycobacterial ilamycin congeners (1–6) bearing rare L-3-nitro-tyrosine and L-2-amino-4-hexenoic acid structural units from the deep sea-derived Streptomyces atratus SCSIO ZH16. The biosynthesis of the rare L-3-nitrotyrosine and L-2-amino-4-hexenoic acid units as well as three pre-tailoring and two post-tailoring steps are probed in the ilamycin biosynthetic machinery through a series of gene inactivation, precursor chemical complementation, isotope-labeled precursor feeding experiments, as well as structural elucidation of three intermediates (6–8) from the respective mutants. Most impressively, ilamycins E₁/E₂, which are produced in high titers by a genetically engineered mutant strain, show very potent anti-tuberculosis activity with an minimum inhibitory concentration value ≈9.8 nM to Mycobacterium tuberculosis H37Rv constituting extremely potent and exciting anti-tuberculosis drug leads.

To investigate the occurrence of 16S rRNA methylases conferring high-level resistance to aminoglycosides in Enterobacteriaceae isolated from two pig farms in China. Enterobacteriaceae isolated from 151 pig rectal swab samples and 9 environmental samples were screened for the presence of the rmtA, rmtB, armA and rmtC genes by PCR and sequencing. Conjugation experiments were carried out to study the transferability of the 16S rRNA methylase genes. All isolates and their transconjugants were tested for susceptibility to antimicrobial agents. The clonal relatedness of RmtB-producing Escherichia coli was assessed by PFGE with XbaI. Of 152 Enterobacteriaceae isolates recovered from pigs, 49 (32%) were positive for the rmtB gene, including 48 E. coli and a single isolate of Enterobacter cloacae. Of the nine Enterobacteriaceae isolates from environmental samples, no 16S rRNA methylase gene was identified. The 49 rmtB-positive isolates showed resistance to ampicillin, tetracycline and trimethoprim and also carried a bla_TEM gene. Transfer of the rmtB and bla_TEM genes by conjugation experiments of all 49 isolates was successful, suggesting that the rmtB-containing plasmids in the E. coli and E. cloacae isolates were self-transmissible. Conjugative transfer frequencies varied from 2.2 × 10⁻¹⁰ to 1.3 × 10⁻⁶ transconjugants per recipient. The transfer of non-aminoglycoside antimicrobial resistance traits was also observed in most cases. Forty-four rmtB-positive E. coli showed 30 different PFGE types. The rmtB gene was detected on conjugative plasmids of porcine E. coli and E. cloacae isolates. Both horizontal gene transfer and clonal spread were responsible for the dissemination of the rmtB gene. The emergence of 16S rRNA methylases in Enterobacteriaceae isolates is described for the first time in China. This is also the first report of rmtB-positive Enterobacteriaceae among healthy food-producing animals.