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Shinji Yamasaki - One of the best experts on this subject based on the ideXlab platform.
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resistance class 1 Integron in clinical methicillin resistant staphylococcus aureus strains in southern china 2001 2006
Clinical Microbiology and Infection, 2011Co-Authors: Mark E Shirtliff, M J Alam, Shinji Yamasaki, Lei Shi, Brian M Peters, Y PengAbstract:Abstract As a novel antibiotic resistance determinant, investigation of the occurrence and characteristics of class 1 Integron was performed on nosocomial methicillin‐resistant Staphylococcus aureus (MRSA) strains sampled during 2001–2006. Seventy‐six out of 179 (42.5%) of the tested strains were found to carry class 1 Integrons, with four unique arrays of gene cassettes detected. This is the first report of the comprehensive identification and typing of class 1 Integrons in clinical MRSA isolates over a 6‐year period, representing the first evidence for class 1 Integrons as possible antibiotic resistance determinants in clinical MRSA strains.
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Integron bearing methicillin resistant coagulase negative staphylococci in south china 2001 2004
Fems Microbiology Letters, 2008Co-Authors: Zhenbo Xu, M J Alam, Lin Li, Shinji YamasakiAbstract:A total of 53 methicillin-resistant coagulase-negative staphylococci strains isolated in a hospital in Guangzhou, China, were analyzed to detect class 1 Integrons and SCC mec typing. Thirty strains had the class 1 integrase ( intI1 ) gene and 26 strains possessed the 3′ conserved region of qacE Δ 1 - sul1 . Four different types of gene cassette arrays were found and a highly prevalent array of dfrA12-orfF-aadA2 gene cassettes was observed. Thirty class 1 Integron-positive coagulase-negative staphylococci strains were subjected to Southern hybridization analysis; the result showed that class 1 Integrons were located on chromosome, not plasmid. According to the results of SCC mec typing for 30 Integron-bearing MRCNS strains, five, 15 and five strains belonged to type I, II and III SCC mec , respectively, and five strains were untypeable. For 23 non-Integron-bearing methicillin-resistant coagulase-negative staphylococci strains, four, nine and seven strains belonged to type I, II and III SCC mec , respectively, and three strains were untypeable. None of the strains belonged to type IV or V. Twenty-three coagulase-negative staphylococci isolates of three Staphylococcal species that contained the dfrA12-orfF-aadA2 gene cassette array were phylogenetically unrelated to each other by randomly amplified polymorphic DNA, indicating that the gene cassettes might be disseminated in the clinical strains by a horizontal gene transfer.
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Integron bearing methicillin resistant coagulase negative staphylococci in south china 2001 2004
Fems Microbiology Letters, 2008Co-Authors: M J Alam, Shinji Yamasaki, Lei ShiAbstract:A total of 53 methicillin-resistant coagulase-negative staphylococci strains isolated in a hospital in Guangzhou, China, were analyzed to detect class 1 Integrons and SCCmec typing. Thirty strains had the class 1 integrase (intI1) gene and 26 strains possessed the 3' conserved region of qacEDelta1-sul1. Four different types of gene cassette arrays were found and a highly prevalent array of dfrA12-orfF-aadA2 gene cassettes was observed. Thirty class 1 Integron-positive coagulase-negative staphylococci strains were subjected to Southern hybridization analysis; the result showed that class 1 Integrons were located on chromosome, not plasmid. According to the results of SCCmec typing for 30 Integron-bearing MRCNS strains, five, 15 and five strains belonged to type I, II and III SCCmec, respectively, and five strains were untypeable. For 23 non-Integron-bearing methicillin-resistant coagulase-negative staphylococci strains, four, nine and seven strains belonged to type I, II and III SCCmec, respectively, and three strains were untypeable. None of the strains belonged to type IV or V. Twenty-three coagulase-negative staphylococci isolates of three Staphylococcal species that contained the dfrA12-orfF-aadA2 gene cassette array were phylogenetically unrelated to each other by randomly amplified polymorphic DNA, indicating that the gene cassettes might be disseminated in the clinical strains by a horizontal gene transfer.
Lei Shi - One of the best experts on this subject based on the ideXlab platform.
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resistance class 1 Integron in clinical methicillin resistant staphylococcus aureus strains in southern china 2001 2006
Clinical Microbiology and Infection, 2011Co-Authors: Mark E Shirtliff, M J Alam, Shinji Yamasaki, Lei Shi, Brian M Peters, Y PengAbstract:Abstract As a novel antibiotic resistance determinant, investigation of the occurrence and characteristics of class 1 Integron was performed on nosocomial methicillin‐resistant Staphylococcus aureus (MRSA) strains sampled during 2001–2006. Seventy‐six out of 179 (42.5%) of the tested strains were found to carry class 1 Integrons, with four unique arrays of gene cassettes detected. This is the first report of the comprehensive identification and typing of class 1 Integrons in clinical MRSA isolates over a 6‐year period, representing the first evidence for class 1 Integrons as possible antibiotic resistance determinants in clinical MRSA strains.
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Integron bearing methicillin resistant coagulase negative staphylococci in south china 2001 2004
Fems Microbiology Letters, 2008Co-Authors: M J Alam, Shinji Yamasaki, Lei ShiAbstract:A total of 53 methicillin-resistant coagulase-negative staphylococci strains isolated in a hospital in Guangzhou, China, were analyzed to detect class 1 Integrons and SCCmec typing. Thirty strains had the class 1 integrase (intI1) gene and 26 strains possessed the 3' conserved region of qacEDelta1-sul1. Four different types of gene cassette arrays were found and a highly prevalent array of dfrA12-orfF-aadA2 gene cassettes was observed. Thirty class 1 Integron-positive coagulase-negative staphylococci strains were subjected to Southern hybridization analysis; the result showed that class 1 Integrons were located on chromosome, not plasmid. According to the results of SCCmec typing for 30 Integron-bearing MRCNS strains, five, 15 and five strains belonged to type I, II and III SCCmec, respectively, and five strains were untypeable. For 23 non-Integron-bearing methicillin-resistant coagulase-negative staphylococci strains, four, nine and seven strains belonged to type I, II and III SCCmec, respectively, and three strains were untypeable. None of the strains belonged to type IV or V. Twenty-three coagulase-negative staphylococci isolates of three Staphylococcal species that contained the dfrA12-orfF-aadA2 gene cassette array were phylogenetically unrelated to each other by randomly amplified polymorphic DNA, indicating that the gene cassettes might be disseminated in the clinical strains by a horizontal gene transfer.
Mariececile Ploy - One of the best experts on this subject based on the ideXlab platform.
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the stringent response promotes antibiotic resistance dissemination by regulating Integron integrase expression in biofilms
Mbio, 2016Co-Authors: Emilie Strugeon, Valentin Tilloy, Mariececile PloyAbstract:ABSTRACT Class 1 Integrons are genetic systems that enable bacteria to capture and express gene cassettes. These Integrons, when isolated in clinical contexts, most often carry antibiotic resistance gene cassettes. They play a major role in the dissemination of antibiotic resistance among Gram-negative bacteria. The key element of Integrons is the integrase, which allows gene cassettes to be acquired and shuffled. Planktonic culture experiments have shown that integrase expression is regulated by the bacterial SOS response. In natural settings, however, bacteria generally live in biofilms, which are characterized by strong antibiotic resilience and by increased expression of stress-related genes. Here, we report that under biofilm conditions, the stringent response, which is induced upon starvation, (i) increases basal integrase and SOS regulon gene expression via induction of the SOS response and (ii) exerts biofilm-specific regulation of the integrase via the Lon protease. This indicates that biofilm environments favor Integron-mediated acquisition of antibiotic resistance and other adaptive functions encoded by gene cassettes. IMPORTANCE Multidrug-resistant bacteria are becoming a worldwide health problem. Integrons are bacterial genetic platforms that allow the bacteria to capture and express gene cassettes. In clinical settings, Integrons play a major role in the dissemination of antibiotic resistance gene cassettes among Gram-negative bacteria. Cassette capture is catalyzed by the Integron integrase, whose expression is induced by DNA damage and controlled by the bacterial SOS response in laboratory planktonic cultures. In natural settings, bacteria usually grow in heterogeneous environments known as biofilms, which have very different conditions than planktonic cultures. Integrase regulation has not been investigated in biofilms. Our results showed that in addition to the SOS response, the stringent response (induced upon starvation) is specifically involved in the regulation of class 1 Integron integrases in biofilms. This study shows that biofilms are favorable environments for Integron-mediated acquisition/exchange of antibiotic resistance genes by bacteria and for the emergence of multidrug-resistant bacteria.
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diversity of class 1 Integron gene cassette rearrangements selected under antibiotic pressure
Journal of Bacteriology, 2015Co-Authors: Olivier Barraud, Mariececile PloyAbstract:Integrons are bacterial genetic elements able to capture and express genes contained within mobile gene cassettes. Gene cassettes are expressed via a Pc promoter and can be excised from or integrated into the Integron by integrase IntI. Although the mechanisms of gene cassette integration and excision are well known, the kinetics and modes of gene cassette shuffling leading to new gene cassette arrays remain puzzling. It has been proposed that under antibiotic selective pressure, IntI-mediated rearrangements can generate Integron variants in which a weakly expressed gene cassette moves closer to Pc, thus leading to higher-level resistance. To test this hypothesis, we used an Integron with four gene cassettes, intI1-aac(6′)-Ib-dfrA15-aadA1-catB9, and applied selective pressure with chloramphenicol, resistance to which is encoded by catB9. Experiments were performed with three different Pc variants corresponding to three IntI1 variants. All three integrases, even when not overexpressed, were able to bring catB9 closer to Pc via excision of the dfrA15 and aadA1 gene cassettes, allowing their host bacteria to adapt to antibiotic pressure and to grow at high chloramphenicol concentrations. Integrase IntI1R32_H39, reported to have the highest recombination activity, was able, when overexpressed, to trigger multiple gene cassette rearrangements. Although we observed a wide variety of rearrangements with catB9 moving closer to Pc and leading to higher chloramphenicol resistance, “cut-and-paste” relocalization of catB9 to the first position was not detected. Our results suggest that gene cassette rearrangements via excision are probably less cost-effective than excision and integration of a distal gene cassette closer to Pc. IMPORTANCE Integrons are bacterial genetic elements able to capture and express gene cassettes. Gene cassettes are expressed via a Pc promoter; the closer they are to Pc, the more strongly they are expressed. Gene cassettes can be excised from or integrated into the Integron by integrase IntI. The kinetics and modes of gene cassette shuffling, leading to new gene cassette arrays remain puzzling. We used an Integron with 4 antibiotic resistance gene cassettes and applied selective pressure with the antibiotic for which resistance was encoded by cassette 4. All IntI variants were able to bring cassette 4 closer to Pc. Rearrangements occur via excision of the previous gene cassettes instead of cut-and-paste relocalization of the fourth gene cassette.
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Prevalence of SOS-mediated control of Integron integrase expression as an adaptive trait of chromosomal and mobile Integrons
Mobile DNA, 2011Co-Authors: Guillaume Cambray, Mariececile Ploy, Didier Mazel, Neus Sanchez-alberola, Susana Campoy, Émilie Guerin, Bruno González-zorn, Jordi Barbé, Ivan ErillAbstract:Background Integrons are found in hundreds of environmental bacterial species, but are mainly known as the agents responsible for the capture and spread of antibiotic-resistance determinants between Gram-negative pathogens. The SOS response is a regulatory network under control of the repressor protein LexA targeted at addressing DNA damage, thus promoting genetic variation in times of stress. We recently reported a direct link between the SOS response and the expression of Integron integrases in Vibrio cholerae and a plasmid-borne class 1 mobile Integron. SOS regulation enhances cassette swapping and capture in stressful conditions, while freezing the Integron in steady environments. We conducted a systematic study of available Integron integrase promoter sequences to analyze the extent of this relationship across the Bacteria domain. Results Our results showed that LexA controls the expression of a large fraction of Integron integrases by binding to Escherichia coli -like LexA binding sites. In addition, the results provide experimental validation of LexA control of the integrase gene for another Vibrio chromosomal Integron and for a multiresistance plasmid harboring two Integrons. There was a significant correlation between lack of LexA control and predicted inactivation of integrase genes, even though experimental evidence also indicates that LexA regulation may be lost to enhance expression of Integron cassettes. Conclusions Ancestral-state reconstruction on an Integron integrase phylogeny led us to conclude that the ancestral Integron was already regulated by LexA. The data also indicated that SOS regulation has been actively preserved in mobile Integrons and large chromosomal Integrons, suggesting that unregulated integrase activity is selected against. Nonetheless, additional adaptations have probably arisen to cope with unregulated integrase activity. Identifying them may be fundamental in deciphering the uneven distribution of Integrons in the Bacteria domain.
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The SOS response controls Integron recombination
Science, 2009Co-Authors: Émilie Guerin, Mariececile Ploy, Guillaume Cambray, Neus Sanchez-alberola, Susana Campoy, Bruno González-zorn, Jordi Barbé, Ivan Erill, Didier MazelAbstract:Integrons are found in the genome of hundreds of environmental bacteria but are mainly known for their role in the capture and spread of antibiotic resistance determinants among Gram-negative pathogens. We report a direct link between this system and the ubiquitous SOS response. We found that LexA controlled expression of most Integron integrases and consequently regulated cassette recombination. This regulatory coupling enhanced the potential for cassette swapping and capture in cells under stress, while minimizing cassette rearrangements or loss in constant environments. This finding exposes Integrons as integrated adaptive systems and has implications for antibiotic treatment policies.
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description of an unusual class 2 Integron in shigella sonnei isolates in senegal sub saharan africa
Journal of Antimicrobial Chemotherapy, 2008Co-Authors: Amy Gassama Sow, Mariececile Ploy, Awa Aidarakane, Mamadou Hadi Diallo, Martine Gatet, F DenisAbstract:Sir, Integrons are genetic elements that acquire gene cassettes by integrase-catalysed site-specific recombination. Integrons contain various combinations of gene cassettes encoding antibiotic resistance determinants and are widespread among Gram-negative bacteria. Five classes of Integrons have been described to date, based on the integrase coding sequence. Classes 1 and 2 are the most frequent. Class 2 was found in transposon Tn7 and its derivatives (Tn1825, Tn1826 and Tn4132), and its 30 segment contains five tns genes involved in transposon movements. The intI2 integrase gene of class 2 Integrons contains a premature stop codon at position 179, rendering the integrase non-functional. Therefore, class 2 Integrons usually contain the same array of four gene cassettes, three antibiotic resistance gene cassettes (dfrA1, sat and aadA1, conferring resistance to trimethoprim, streptothricin and spectinomycin/streptomycin, respectively) and an orfX of unknown function. However, variations of the cassette contents have been described, resulting from Intl1 integrase-catalysed co-integrate formation between a class 1 and a class 2 Integron, or from an RecA-dependent homologous recombination between two copies of the same cassette found in both classes of Integron. Indeed, the dfrA1 and aadA1 cassettes, initially described in class 2 Integrons, have also been found in class 1 Integrons. Class 1 and 2 Integrons have frequently been found in Shigella strains, and class 2 Integrons predominate in Shigella sonnei and Shigella flexneri. – 5 We have previously described Integron structures in S. sonnei strains isolated in Senegal; they included a class 2 Integron of 4 kb found in two epidemiologically related isolates. Here, we describe the organization of this class 2 Integron. The following primers were used for PCR mapping of the class 2 Integron: hep74 in attI2, ORFX1 (CTCGTACTTG CGATGGCATC) in ORFX, and int2CS2 and int7S, both located in tnsE. Amplification was performed with the Expand Long Template PCR System (Roche Molecular Biochemicals, Roche Diagnostics GmbH, Germany). With primers hep74 and ORFX1, agarose gel electrophoresis identified a 4074 bp DNA fragment (data not shown) in both isolates, instead of the expected 3095 bp product. No PCR product was obtained with primers int2CS2 and int7S, suggesting a different arrangement in the 30 region of this class 2 Integron. The entire class 2 Integron was amplified with primer int2S in intI2 and with primer ORFX3 located in Tn7, downstream of the ORFX cassette. A PCR product of 4174 bp was purified with the QIAquick kit (Qiagen SA, Courtaboeuf, France), cloned with the pGEM-T vector system (Promega, Madison, WI, USA), transformed into XL1-Blue competent cells (Stratagene, Garden Grove, CA, USA) and sequenced. Sequence analysis of the 4174 bp insert of the recombinant plasmid showed that this Integron harboured the four gene cassettes usually found in class 2 Integrons, namely dfrA1, sat1, aadA1 and orfX (accession no. EU732664). However, the sat1 cassette was interrupted at position 186 by a complete copy of the insertion sequence IS911, a member of the IS3 family. IS911 was initially isolated from Shigella dysenteriae, but has since been detected (10–20 copies per cell) in the four Shigella species. As usually described for IS911, its insertion generated a 3 bp duplication (TAT) in the target sat1 sequence. To our knowledge, two ISs have previously been described in class 2 Integrons, but not within the array of gene cassettes. Dubois et al. described a class 2 Integron with an IS630 element in a strain of S. flexneri, and Biskri and Mazel described a class 2 Integron with an IS1 in a strain of Escherichia coli. Both were located between intI2 and the first gene cassette. To determine whether the resistance determinants carried by the Integron were transferable, we performed a conjugation experiment on MH agar plates from S. sonnei to an E. coli strain resistant to nalidixic acid. We used a selective medium containing 50 mg/L nalidixic acid plus 100 mg/L trimethoprim. No transconjugants were obtained, suggesting the chromosomal location of this Tn7-containing class 2 Integron as previously described in Shigella isolates. Pan et al. described a class 2 Integron on transposon Tn7 inserted into the Tn7-specific target attTn7 of the S. sonnei chromosome downstream of the glmUS operon. Thus, to confirm the chromosomal insertion of Tn7, we successfully performed a PCR with primers Tn7R-F and glmS-R as described by Pan et al. Another feature of this atypical class 2 Integron is the deletion of the tns genes, described in Tn7 and its derivatives. A class 2 Integron lacking the tns genes has previously been described in Acinetobacter baumannii, but the 30 segment of the class 2 Integron contained the ORFs found in the 30 segment of class 1 Integrons (qacED1, sul1 and ORF5). The PCR method previously used to detect such a chimeric Integron with primers aadAL and ORFR was unsuccessful, suggesting that the class 2 Integron that we describe here is not a hybrid class 2/class 1 Integron. In conclusion, we describe an unusual class 2 Integron in a S. sonnei strain isolated in Africa. This new class 2 Integron is characterized by the presence of one complete copy of the IS911 element inserted within the sat1 gene cassette. Journal of Antimicrobial Chemotherapy 62, 843–851 doi:10.1093/jac/dkn264 Advance Access publication 18 June 2008
M J Alam - One of the best experts on this subject based on the ideXlab platform.
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resistance class 1 Integron in clinical methicillin resistant staphylococcus aureus strains in southern china 2001 2006
Clinical Microbiology and Infection, 2011Co-Authors: Mark E Shirtliff, M J Alam, Shinji Yamasaki, Lei Shi, Brian M Peters, Y PengAbstract:Abstract As a novel antibiotic resistance determinant, investigation of the occurrence and characteristics of class 1 Integron was performed on nosocomial methicillin‐resistant Staphylococcus aureus (MRSA) strains sampled during 2001–2006. Seventy‐six out of 179 (42.5%) of the tested strains were found to carry class 1 Integrons, with four unique arrays of gene cassettes detected. This is the first report of the comprehensive identification and typing of class 1 Integrons in clinical MRSA isolates over a 6‐year period, representing the first evidence for class 1 Integrons as possible antibiotic resistance determinants in clinical MRSA strains.
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Integron bearing methicillin resistant coagulase negative staphylococci in south china 2001 2004
Fems Microbiology Letters, 2008Co-Authors: Zhenbo Xu, M J Alam, Lin Li, Shinji YamasakiAbstract:A total of 53 methicillin-resistant coagulase-negative staphylococci strains isolated in a hospital in Guangzhou, China, were analyzed to detect class 1 Integrons and SCC mec typing. Thirty strains had the class 1 integrase ( intI1 ) gene and 26 strains possessed the 3′ conserved region of qacE Δ 1 - sul1 . Four different types of gene cassette arrays were found and a highly prevalent array of dfrA12-orfF-aadA2 gene cassettes was observed. Thirty class 1 Integron-positive coagulase-negative staphylococci strains were subjected to Southern hybridization analysis; the result showed that class 1 Integrons were located on chromosome, not plasmid. According to the results of SCC mec typing for 30 Integron-bearing MRCNS strains, five, 15 and five strains belonged to type I, II and III SCC mec , respectively, and five strains were untypeable. For 23 non-Integron-bearing methicillin-resistant coagulase-negative staphylococci strains, four, nine and seven strains belonged to type I, II and III SCC mec , respectively, and three strains were untypeable. None of the strains belonged to type IV or V. Twenty-three coagulase-negative staphylococci isolates of three Staphylococcal species that contained the dfrA12-orfF-aadA2 gene cassette array were phylogenetically unrelated to each other by randomly amplified polymorphic DNA, indicating that the gene cassettes might be disseminated in the clinical strains by a horizontal gene transfer.
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Integron bearing methicillin resistant coagulase negative staphylococci in south china 2001 2004
Fems Microbiology Letters, 2008Co-Authors: M J Alam, Shinji Yamasaki, Lei ShiAbstract:A total of 53 methicillin-resistant coagulase-negative staphylococci strains isolated in a hospital in Guangzhou, China, were analyzed to detect class 1 Integrons and SCCmec typing. Thirty strains had the class 1 integrase (intI1) gene and 26 strains possessed the 3' conserved region of qacEDelta1-sul1. Four different types of gene cassette arrays were found and a highly prevalent array of dfrA12-orfF-aadA2 gene cassettes was observed. Thirty class 1 Integron-positive coagulase-negative staphylococci strains were subjected to Southern hybridization analysis; the result showed that class 1 Integrons were located on chromosome, not plasmid. According to the results of SCCmec typing for 30 Integron-bearing MRCNS strains, five, 15 and five strains belonged to type I, II and III SCCmec, respectively, and five strains were untypeable. For 23 non-Integron-bearing methicillin-resistant coagulase-negative staphylococci strains, four, nine and seven strains belonged to type I, II and III SCCmec, respectively, and three strains were untypeable. None of the strains belonged to type IV or V. Twenty-three coagulase-negative staphylococci isolates of three Staphylococcal species that contained the dfrA12-orfF-aadA2 gene cassette array were phylogenetically unrelated to each other by randomly amplified polymorphic DNA, indicating that the gene cassettes might be disseminated in the clinical strains by a horizontal gene transfer.
Ruth M Hall - One of the best experts on this subject based on the ideXlab platform.
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pcerc3 from a commensal st95 escherichia coli a colv virulence multiresistance plasmid carrying a sul3 associated class 1 Integron
Plasmid, 2016Co-Authors: Robert A Moran, Kathryn E Holt, Ruth M HallAbstract:The rare sulphonamide resistance gene sul3 was found in the commensal Escherichia coli ST95 strain 22.1-R1 that was isolated in 2010 from the faeces of a healthy Australian adult. The genome of 22.1-R1 was sequenced and a 144,344bp RepFII/FIB plasmid, pCERC3, carrying sul3 was assembled. The sul3 gene is part of a class 1 Integron featuring a sul3-containing conserved segment (sul3-CS) that replaced the classic sul1-containing 3'-conserved segment (3'-CS) usually seen in class 1 Integrons. The Integron contained the cassette array dfrA12-orfF-aadA2-cmlA1-aadA1-qacH, conferring resistance to trimethoprim, streptomycin, spectinomycin, chloramphenicol and quaternary ammonium compound. Two additional antibiotic resistance genes, blaTEM (ampicillin resistance) and tetA(B) (tetracycline) were adjacent to the Integron, forming a single resistance region. In pCERC3, the sul3-type class 1 Integron was flanked by sequence derived from the tnp and mer modules of Tn21 and was in the same location as In2, the sul1-containing In5-type class 1 Integron of Tn21. At one end the sequence extends into Tn2670-derived sequence and then into sequence derived from the plasmid NR1 (R100). Examination of the sequences of eleven more complete sul3-containing plasmids in GenBank confirmed the relationship between sul3-associated Integrons and Tn21/Tn2670/NR1. This suggests that the events that formed sul3-associated class 1 Integrons occurred within the Tn21/Tn2670 context, most likely in NR1 or a related plasmid. The backbone of pCERC3 is most closely related to the backbones of ColV virulence plasmids and contains a complete ColV operon as well as several virulence associated genes and gene clusters. Hence, pCERC3 is both an antibiotic resistance and virulence plasmid.
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transposons related to tn1696 in inchi2 plasmids in multiply antibiotic resistant salmonella enterica serovar typhimurium from australian animals
Microbial Drug Resistance, 2010Co-Authors: Amy K Cain, Steven P Djordjevic, Xiulan Liu, Ruth M HallAbstract:Conjugative IncHI2 plasmids carrying tetracycline, trimethoprim, and sulphonamide resistance genes were recovered from two multiply antibiotic resistant Salmonella enterica serovar Typhimurium isolates from Australian food-producing animals. Transposons related to the mercury resistance transposon Tn1696 were identified in both IncHI2 plasmids. These transposons contained an In4-type class 1 Integron that carried a dfrA5 trimethoprim resistance gene cassette and the sul1 sulfonamide resistance gene. These Integrons were located in the same position as In4 in Tn1696. The Integron from one isolate includes a large transposon-like structure containing four IS26 and the strAB, sul2, blaTEM, and aphA1 genes conferring resistance to streptomycin, sulphonamides, ampicillin, kanamycin, and neomycin, respectively. This structure is flanked by an 8-bp duplication, but it includes both the aphA1-containing transposon Tn4352 and a transposon, Tn6029, carrying genes derived from RSF1010 and from Tn2. However, Tn4352 a...
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sgi2 a relative of salmonella genomic island sgi1 with an independent origin
Antimicrobial Agents and Chemotherapy, 2008Co-Authors: Renee S Levings, Steven P Djordjevic, Ruth M HallAbstract:Multiply antibiotic-resistant Salmonella enterica serovar Emek strains isolated in Australia and the United Kingdom had similar features, suggesting that they all belong to a single clone. These strains all contain SGI2 (formerly SGI1-J), an independently formed relative of Salmonella genomic island SGI1. In SGI2, the complex class 1 Integron which includes all of the resistance genes is not located between tnpR (S027) and S044 as in SGI1 and SGI1 variants. Instead, tnpR was found to be adjacent to S044, and the Integron is located 6.9 kb away, within S023. In both SGI1 and SGI2, the 25-bp inverted repeats that mark the outer ends of class 1 Integrons are flanked by a 5-bp duplication of the target, indicating that incorporation of the Integron was by transposition. A small number of differences between the sequences of the backbones of SGI1 and SGI2 were also found. Hence, a class 1 Integron has entered two different variants of the SGI backbone to generate two distinct lineages. Despite this, the Integron in SGI2 has a complex structure that is very similar to that of In104 in SGI1. Differences are in the cassette arrays and in the gene which encodes the chloramphenicol and florfenicol efflux protein. The CmlA9 protein, encoded by InEmek, is only 92.8% identical to FloRc (also a CmlA family protein) from SGI1. A variant form of SGI2, SGI2-A, which has lost the tet(G) and cmlA9 resistance determinants, was found in one strain.
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sgi1 k a variant of the sgi1 genomic island carrying a mercury resistance region in salmonella enterica serovar kentucky
Antimicrobial Agents and Chemotherapy, 2007Co-Authors: Renee S Levings, Sally R Partridge, Steven P Djordjevic, Ruth M HallAbstract:A multiple-antibiotic-resistant Salmonella enterica serovar Kentucky strain was found to contain SGI1-K, a variant form of the Salmonella genomic island 1 (SGI1) with an In4-type class 1 Integron that contains only one cassette array, aacCA5-aadA7, and an adjacent mercury resistance module. Part of the 3′-conserved segment (3′-CS) of the Integron, together with the inverted short segment from the right-hand end of the Integron transposition module normally found between the 3′-CS and IS6100 in In4 family Integrons, has been removed by an IS6100-mediated deletion. IRt, the right-hand inverted repeat found at the outer end of the Integron, abuts a mercury resistance region instead of the usual SGI1 backbone segment. The mer module is a hybrid of those found in Tn501 and Tn21. This mer region and a further uncharacterized segment of at least 10 kb appear to have been incorporated between IRt and the SGI1 backbone. These findings demonstrate that the multidrug resistance region in SGI1 can incorporate new DNA segments in the same way as multiple antibiotic resistance regions in plasmids.
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transposons tn1696 and tn21 and their Integrons in4 and in2 have independent origins
Antimicrobial Agents and Chemotherapy, 2001Co-Authors: Sally R Partridge, H W Stokes, Heidi J Brown, Ruth M HallAbstract:The first 13.6 kb of the mercury and multidrug resistance transposon Tn1696, which includes the class 1 Integron In4, has been sequenced. In4 is 8.33 kb long and contains the 5′-conserved segment (5′-CS) and 2.24 kb of the 3′-conserved segment (3′-CS) flanking four integrated cassettes. The 3′-CS region is followed by one full copy and an adjacent partial copy of the insertion sequence IS6100 flanked, in inverse orientation, by two short segments (123 and 152 bp) from the outer right-hand end of class 1 Integrons. This structure is representative of a distinct group of class 1 Integrons that differs from In2, found in Tn21, and other related class 1 Integrons. In4 does not include transposition genes but is bounded by characteristic 25-bp inverted repeats and flanked by a direct duplication of 5 bp of the target sequence, indicating that it was inserted by a transpositional mechanism. In4 lies between the resII and resI sites of a backbone mercury resistance transposon which is >99.5% identical to Tn5036. Although Tn21 and Tn1696 are both classified as members of the Tn21 subfamily of the Tn3 transposon family, the backbone mercury resistance transposons are only 79 to 96% identical. Tn21 also contains a region of about 0.7 kb not found in Tn1696. The Integrons In2 and In4 carrying the antibiotic resistance genes have been inserted at different locations into distinct ancestral mercury resistance transposons. Thus, Tn21 and Tn1696 have independent histories and origins. Other transposons (Tn1403 and Tn1412) that include a class 1 Integron also have independent origins. In all except Tn21, the Integron is located within the res region of the backbone transposon.