Insertion sequences(ISs)promote the transmission of antimicrobial resistance genes(ARGs)across bacterial populations.However,their contributions and dynamics during the transmission of resistance remain unclear.In thi...Insertion sequences(ISs)promote the transmission of antimicrobial resistance genes(ARGs)across bacterial populations.However,their contributions and dynamics during the transmission of resistance remain unclear.In this study,we selected is26 as a representative transposable element to decipher the relationship between ISs and ARGs and to investigate their transfer features and transmission trends.We retrieved 2656 translocatable IS26-bounded units with ARGs(tiS26-bUs-ARGs)in complete bacterial genomes from the NCBI RefSeq database.In total,124 ARGs spanning 12 classes of antibiotics were detected,and the average contribution rate of IS26 to these genes was 41.2%.We found that IS26-bounded units(IS26-bUs)mediated extensive ARG dissemination within the bacteria of the Gammaproteobacteria class,showing strong transfer po-tential between strains,species,and even phyla.The Is26-bUs expanded in bacterial populations over time,and their temporal expansion trend was significantly correlated with antibiotic usage.This wide dissemination could be due to the nonspecific target site preference of is26.Finally,we experimentally confirmed that the introduction of a single copy of is26 could lead to the formation of a composite transposon mediating the transmission of“passenger”genes.These observations extend our knowledge of the IS26 and provide new insights into the mediating role of ISs in the dissemination of antibiotic resistance.展开更多
Polymyxin B and polymyxin E(colistin)are presently considered the last line of defense against human infections caused by multidrug-resistant Gram-negative organisms such as carbapenemase-producer Enterobacterales,Aci...Polymyxin B and polymyxin E(colistin)are presently considered the last line of defense against human infections caused by multidrug-resistant Gram-negative organisms such as carbapenemase-producer Enterobacterales,Acinetobacter baumannii,and Klebsiella pneumoniae.Yet resistance to this last-line drugs is a major public health threat and is rapidly increasing.Polymyxin S2(S2)is a polymyxin B analogue previously synthesized in our institute with obviously high antibacterial activity and lower toxicity than polymyxin B and colistin.To predict the possible resistant mechanism of S2for wide clinical application,we experimentally induced bacterial resistant mutants and studied the preliminary resistance mechanisms.Mut-S,a resistant mutant of K.pneumoniae ATCC BAA-2146(Kpn2146)induced by S2,was analyzed by whole genome sequencing,transcriptomics,mass spectrometry and complementation experiment.Surprisingly,large-scale genomic inversion(LSGI)of approximately 1.1 Mbp in the chromosome caused by IS26mediated intramolecular transposition was found in Mut-S,which led to mgrB truncation,lipid A modification and hence S2resistance.The resistance can be complemented by plasmid carrying intact mgrB.The same mechanism was also found in polymyxin B and colistin induced drug-resistant mutants of Kpn2146(Mut-B and Mut-E,respectively).This is the first report of polymyxin resistance caused by IS26 intramolecular transposition mediated mgrB truncation in chromosome in K.pneumoniae.The findings broaden our scope of knowledge for polymyxin resistance and enriched our understanding of how bacteria can manage to survive in the presence of antibiotics.展开更多
The tet C gene has been found to be one of the most widely distributed tetracycline resistance( tet) genes in various environmental niches, but the detailed dissemination mechanisms are still largely unknown. In the p...The tet C gene has been found to be one of the most widely distributed tetracycline resistance( tet) genes in various environmental niches, but the detailed dissemination mechanisms are still largely unknown. In the present study, 11 tet C-containing Aeromonas media strains were isolated from an aerobic biofilm reactor under oxytetracycline stresses, and the genome of one strain was sequenced using the Pac Bio RSII sequencing approach to reveal the genetic environment of tet C. The tet C gene was carried by an IS 26 composite transposon, named Tn 6434. The tet C-carrying Tn 6434 structure was detected in all of the A. media strains either in a novel plasmid p Aeme2( n = 9) or other DNA molecules( n = 2) by PCR screening. The NCBI database searching result shows that this structure was also present in the plasmids or chromosomes of other 13 genera, indicating the transferability of Tn 6434. Inverse PCR and sequencing confirmed that Tn 6434 can form a circular intermediate and is able to incorporate into a preexisting IS 26 element, suggesting that Tn 6434 might be responsible for the dissemination of tet C between different DNA molecules. This study will be helpful in uncovering the spread mechanism of tet genes in water environments.展开更多
基金supported by the National Key R&D Program of China(grant No.2021YFC2302005)the National Natural Science Foundation of China(grant Nos.32300162 and 32070075).
文摘Insertion sequences(ISs)promote the transmission of antimicrobial resistance genes(ARGs)across bacterial populations.However,their contributions and dynamics during the transmission of resistance remain unclear.In this study,we selected is26 as a representative transposable element to decipher the relationship between ISs and ARGs and to investigate their transfer features and transmission trends.We retrieved 2656 translocatable IS26-bounded units with ARGs(tiS26-bUs-ARGs)in complete bacterial genomes from the NCBI RefSeq database.In total,124 ARGs spanning 12 classes of antibiotics were detected,and the average contribution rate of IS26 to these genes was 41.2%.We found that IS26-bounded units(IS26-bUs)mediated extensive ARG dissemination within the bacteria of the Gammaproteobacteria class,showing strong transfer po-tential between strains,species,and even phyla.The Is26-bUs expanded in bacterial populations over time,and their temporal expansion trend was significantly correlated with antibiotic usage.This wide dissemination could be due to the nonspecific target site preference of is26.Finally,we experimentally confirmed that the introduction of a single copy of is26 could lead to the formation of a composite transposon mediating the transmission of“passenger”genes.These observations extend our knowledge of the IS26 and provide new insights into the mediating role of ISs in the dissemination of antibiotic resistance.
基金supported by the National Natural Science Foundation of China(32141003)the CAMS Innovation Fund for Medical Sciences(CIFMS)(2021-I2M-1-030,2021-I2M-1-039,China)+1 种基金the Fundamental Research Funds for the Central Universities(2021-PT350-001,China)the National Science and Technology Infrastructure of China(NPRC-32)。
文摘Polymyxin B and polymyxin E(colistin)are presently considered the last line of defense against human infections caused by multidrug-resistant Gram-negative organisms such as carbapenemase-producer Enterobacterales,Acinetobacter baumannii,and Klebsiella pneumoniae.Yet resistance to this last-line drugs is a major public health threat and is rapidly increasing.Polymyxin S2(S2)is a polymyxin B analogue previously synthesized in our institute with obviously high antibacterial activity and lower toxicity than polymyxin B and colistin.To predict the possible resistant mechanism of S2for wide clinical application,we experimentally induced bacterial resistant mutants and studied the preliminary resistance mechanisms.Mut-S,a resistant mutant of K.pneumoniae ATCC BAA-2146(Kpn2146)induced by S2,was analyzed by whole genome sequencing,transcriptomics,mass spectrometry and complementation experiment.Surprisingly,large-scale genomic inversion(LSGI)of approximately 1.1 Mbp in the chromosome caused by IS26mediated intramolecular transposition was found in Mut-S,which led to mgrB truncation,lipid A modification and hence S2resistance.The resistance can be complemented by plasmid carrying intact mgrB.The same mechanism was also found in polymyxin B and colistin induced drug-resistant mutants of Kpn2146(Mut-B and Mut-E,respectively).This is the first report of polymyxin resistance caused by IS26 intramolecular transposition mediated mgrB truncation in chromosome in K.pneumoniae.The findings broaden our scope of knowledge for polymyxin resistance and enriched our understanding of how bacteria can manage to survive in the presence of antibiotics.
基金supported by the Project of International Cooperation and Exchanges NSFC(No.31861143049)the National Natural Scientific Foundation of China(Nos.51978645,21437005)the China Postdoctoral Science Foundation(No.2019M661756).
文摘The tet C gene has been found to be one of the most widely distributed tetracycline resistance( tet) genes in various environmental niches, but the detailed dissemination mechanisms are still largely unknown. In the present study, 11 tet C-containing Aeromonas media strains were isolated from an aerobic biofilm reactor under oxytetracycline stresses, and the genome of one strain was sequenced using the Pac Bio RSII sequencing approach to reveal the genetic environment of tet C. The tet C gene was carried by an IS 26 composite transposon, named Tn 6434. The tet C-carrying Tn 6434 structure was detected in all of the A. media strains either in a novel plasmid p Aeme2( n = 9) or other DNA molecules( n = 2) by PCR screening. The NCBI database searching result shows that this structure was also present in the plasmids or chromosomes of other 13 genera, indicating the transferability of Tn 6434. Inverse PCR and sequencing confirmed that Tn 6434 can form a circular intermediate and is able to incorporate into a preexisting IS 26 element, suggesting that Tn 6434 might be responsible for the dissemination of tet C between different DNA molecules. This study will be helpful in uncovering the spread mechanism of tet genes in water environments.
