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At least 127 records · Page 7Linked to original sources
PubMed2005

Incidence of class 1 integrons in multiple antibiotic-resistant Gram-negative copiotrophic bacteria from the River Torsa in India.

The presence of class 1 integrons in multiple-antibiotic-resistant (MAR) Gram-negative copiotrophic bacteria from the River Torsa in India was detected using a polymerase chain reaction (PCR)-based screening method. Among 100 isolates that were resistant to at least five of the twelve antibiotics tested, 40 carried class 1 integrons, with inserted DNA regions of 0.7-3.2 kb. Carriage of integrons in strains of higher MAR index was found to be statistically significant. DNA sequencing was used to identify the genetic content of the integron-variable regions. In addition to the identification of gene cassettes dfrA1, dfrA5, dfrA7, dfrA17 and a variant of dfrA12 for trimethoprim, aac(6')-Ib for amikacin and tobramycin and aadA1 and aadA6 for streptomycin and spectinomycin resistance, a novel ORF predicted from a sequence of Morganella sp. TR 90 bearing homology with the Vibrio cholerae dfrA1 gene cassette was characterized. To our knowledge, this is the first report of the incidence and abundance of class 1 integrons in copiotrophic river water bacteria from India.

DNA, Bacterial↗
PubMed2006

Class 1 integrons in Dutch Salmonella enterica serovar Dublin isolates from clinical cases of bovine salmonellosis.

Fifty-nine Salmonella enterica serovar Dublin (Salmonella Dublin) isolates from clinical cases of bovine salmonellosis between 1993 and 2004 were tested for their susceptibility to 15 antimicrobial agents and the presence of class 1 integrons. Integrons were further analyzed by conserved segment PCR-RFLP. DNA sequencing was used to identify the inserted gene cassette. Twelve (20.3%) isolates were multidrug-resistant. A combination of resistance against chloramphenicol, streptomycin and sulphonamides was the most common phenotype observed. Multidrug-resistance (MDR) was found to be strongly associated with the presence of integrons, since a class 1 integron with the aadA1 gene cassette encoding resistance to streptomycin and spectinomycin was found in all 12 multidrug-resistant isolates. The presence of the aadA1 gene in Salmonella Dublin has not been reported before. None of the integron carrying Salmonella Dublin isolates could transfer its antimicrobial resistance to E. coli K12 by conjugation. Analysis of plasmid profiles and pulsed field gel electrophoresis (PFGE) patterns showed at least some clonality among the Salmonella Dublin isolates, but 11 different types could be distinguished based on both XbaI and BlnI-PFGE patterns. Thus, the Dutch Salmonella Dublin strains were closely related but not clonal.

Animals↗
PubMed2002

Distribution and characterization of class 1 integrons in Salmonella enterica serotype Gallinarum biotype Gallinarum.

Fowl typhoid caused by Salmonella enterica subsp. enterica serotype Gallinarum biotype Gallinarum is the most important chicken disease in Korea. Due to appearance of new or multiple antibiotics resistances in the recently isolated strains, it was difficult to control the disease using antibiotics in our country. Therefore, the prevalence and genetic contents of class 1 integrons in biotype Gallinarum isolated between 1992 and 2001 were investigated by PCR and direct sequencing, respectively. Out of 90 strains, 35 (39%) carried class 1 integrons. The 1.0, 1.6 and 2.0kbp amplicons were amplified in 32 strains (36%), 2 strains (2%) and 1 strain (1%), respectively. The 1.0, 1.6 and 2.0 kbp amplicons contained one (aadA1a), two (aadB-aadA1b) and three cassettes (dhfrXII-orfF-aadA2), respectively, providing resistances against aminoglycosides (aadA1a, aadA1b, aadB, and aadA2) and trimethoprim (dhfrXII). The integron-carrying strains of biotype Gallinarum appeared in 1996 and acquired additional cassettes in 2000. Although the resistances to ampicillin, tetracycline and chloramphenicol are unrelated to class 1 integrons, relatively high prevalence of integron in biotype Gallinarum may be a dormant threat to the chemotherapy of the disease in the near future because of potency to acquire additional antibiotics resistances.

Animals↗
PubMed2002

The role of integrons in the dissemination of antibiotic resistance among clinical isolates of Pseudomonas aeruginosa from an intensive care unit in Brazil.

Eighty-five Pseudomonas aeruginosa isolates resistant to various antibiotics were selected from the intensive care unit of a Brazilian hospital and analyzed for integron content by PCR. Fifty-four of them had class-1-related integrons, some of which were identical. Integron-positive isolates were statistically more resistant to aminoglicoside, quinolone and beta-lactam compounds. Ribotyping of integron-positive isolates demonstrated the presence of identical integrons among genetically unrelated strains in the hospital environment, confirming its role in the spread of gene cassettes in bacterial populations of clinical importance.

Anti-Bacterial Agents↗
PubMed2006

Antimicrobial resistance in nontyphoidal Salmonella from food sources in Colombia: evidence for an unusual plasmid-localized class 1 integron in serotypes Typhimurium and Anatum.

Seventy-two isolates representing 18 serotypes recovered from various food samples collected in Colombia were tested for antimicrobial susceptibilities. The collection was further characterized for extended-spectrum cephalosporin, aminoglycoside, and tetracycline resistance markers. Multidrug resistant (MDR) isolates were further investigated for class 1 integrons and were evaluated for the presence of conjugative plasmids along with a determination of the incompatibility group by polymerase chain reaction (PCR). Antibiogram analysis showed that the incidence rate of ceftiofur resistance was moderately high (15%). A similar level of resistance to neomycin and oxytetracycline (11% and 10%, respectively) was also observed. There was a high prevalence of gene cassettes as part of one or more class 1 integrons (61%), many of which contained determinants that contributed to the resistance profile. Class 1 integrons identified in MDR Salmonella enterica serotypes Typhimurium and Anatum isolates were characterized. Sequencing identified several incomplete open reading frames (ORFs) as part of a gene cassette (bla-( imp-13 ), dfr7, blr1088, and aac8) along with a complete gene cassette (bla-(oxa2)) in each case. A mosaic of gene cassettes was identical in the two Salmonella serotypes. These integrons were located to a conjugative replicon. Plasmid profiling and incompatibility typing identified three plasmids belonging to Inc groups A/C, P, and W. Our study highlights the role of integrons, contributing to a MDR phenotype that is capable of dissemination to other bacteria.

Anti-Bacterial Agents↗
PubMed2003

Prevalence and types of class 1 integrons in aminoglycoside-resistant Enterobacteriaceae from several Chilean hospitals.

Members of the family Enterobacteriaceae are responsible for a variety of nosocomial infections, treatment of which is limited due to their increasing resistance to antibiotics. Some bacterial genes encoding antibiotic resistance comprise the major part of gene cassettes, most of which are associated with integrons. In this work, the carriage of class 1, 2 and 3 integrons was investigated in 191 Enterobacteriaceae isolates from clinical specimens of hospitalized patients. Class 1 integrons were found to be the most common, whereas no class 3 integrons were detected. The variable regions of 13 class 1 integrons were characterized and four types were found. Type 1 harbours only ant(3")I, type 2 harbours ant(2")I and ant(3")I, type 3 harbours aac(6')Ib and ant(3")I and type 4 lacks inserted gene cassettes.

Aminoglycosides↗
PubMed2004

Molecular characterization of class 1 integrons from Irish thermophilic Campylobacter spp.

OBJECTIVES: In this study a large random collection (n = 378) of Irish thermophilic Campylobacter isolates were investigated for the presence of integrons, genetic elements associated with the dissemination of antimicrobial resistance. METHODS: Purified genomic DNA from each isolate was analysed by PCR for the presence of class 1 integrons. Four gene cassette-associated amplicons were completely characterized. RESULTS: Sixty-two of the isolates possessed a complete class 1 integron with a recombined gene cassette located within a 1.0 kb amplicon containing an aadA2 gene. This cassette was present in both Campylobacter jejuni and Campylobacter coli isolates and following sequence analysis was shown to be similar to sequences recently reported in Salmonella enterica Hadar and on an 85 kb plasmid conferring quinolone resistance in Escherichia coli. CONCLUSIONS: Aminoglycoside aadA2-encoding class 1 integrons were identified among unrelated Campylobacter spp. Amino acid sequence comparisons revealed identical structures in both Salmonella and E. coli. The presence of class 1 integrons in Campylobacter spp. may be significant should these organisms enter the food chain and especially when antimicrobial treatment for severe infections is being considered.

Animals↗
PubMed2005

Occurrence of integrons and resistance genes among sulphonamide-resistant Shigella spp. from Brazil.

OBJECTIVES: To determine the occurrence of class 1 and 2 integrons and antimicrobial resistance genes among sulphonamide-resistant Shigella strains isolated in Brazil during 1999-2003. METHODS: Sixty-two Shigella (Shigella flexneri, n = 47 and Shigella sonnei, n = 15) were tested against 21 antimicrobial agents. The presence of integrons classes 1 and 2 and antimicrobial resistance genes was investigated by PCR using specific primers. RESULTS: A total of eight antimicrobial resistance profiles were identified, with the profile of resistance to sulfamethoxazole, trimethoprim, spectinomycin, streptomycin and tetracycline being the most common among S. sonnei, and additionally to ampicillin and chloramphenicol among S. flexneri. Class 1 integrons were found in only two strains, whereas class 2 integrons were found in 56 (90.3%) of the strains. All class 2-positive strains had a similar fragment of 2214 bp harbouring a gene cassette array conferring resistance to trimethoprim, streptothricin and spectinomycin/streptomycin. The genes coding for resistance to chloramphenicol (catA1), tetracycline [tet(A) and tet(B)] and ampicillin (bla(OXA) and bla(TEM)), were detected in resistant strains. CONCLUSIONS: The detection of class 1 and 2 integrons and additional antimicrobial resistance genes allowed us to identify the most frequent antimicrobial resistance patterns of Shigella spp. isolated in Brazil.

DNA Transposable Elements↗
PubMed2005

Class 1 integron-associated gene cassettes in Salmonella enterica subsp. enterica serovar Agona isolated from pig carcasses in Brazil.

OBJECTIVES: Two multiresistant Salmonella enterica subsp. enterica serovar Agona isolates from pig carcasses were investigated for antimicrobial resistance genes and their location with particular reference to the detection of class 1 integrons. METHODS: The two S. Agona isolates were investigated for their in vitro susceptibility to antimicrobial agents and their plasmid content. The resistance genes and class 1 amplicons were identified by PCR assays. Amplicons of class 1 integrons were cloned and sequenced. Transferability of resistance plasmids was confirmed by conjugation. RESULTS: Both S. Agona isolates carried conjugative plasmids of approximately 150 kb which harboured all resistance genes detected in the respective isolates. S. Agona 231 was resistant to chloramphenicol by catA1, to tetracycline and minocycline by tet(B), and to sulphonamides by sul1. In addition, it harboured a streptomycin resistance gene strA and a class 1 integron with a new aadA variant designated aadA23, which mediates resistance to streptomycin and spectinomycin. S. Agona 242 also carried the genes catA1, tet(B), and sul1. Moreover, it harboured a second sulphonamide resistance gene, sul2, and a class 1 integron with intact gene cassettes carrying new variants of the trimethoprim resistance gene dfrA15b or the chloramphenicol resistance gene cmlA4. The third gene cassette consisted of a truncated aadA2 gene. CONCLUSIONS: The results of this study show that large conjugative multiresistance plasmids are present in S. Agona from pigs. Analysis of the class 1 integrons revealed the presence of new variants of resistance genes so far not detected in Salmonella isolates.

Abattoirs↗
PubMed2006

Distribution and characterization of integrons in various serogroups of Vibrio cholerae strains isolated from diarrhoeal patients between 1992 and 2000 in Kolkata, India.

A total of 133 clinical strains of Vibrio cholerae comprising 44 strains of O1, 45 strains of O139 and 44 strains of non-O1, non-O139 serogroups isolated from hospitalized patients in Kolkata, India, from 1992 to 2000 was examined for the presence of class 1, 2 and 4 integrons. By PCR and DNA sequencing, seven strains of O1, one strain of O139 and six strains of non-O1, non-O139 serogroups were found to contain class 1 integron-harbouring genes aadA1, aadA2 (encoding resistance to streptomycin and spectinomycin), blaP1 (resistance to beta-lactams), aar-3 (resistance to rifampicin), aacA4 (resistance to kanamycin and gentamicin), and dfrA1 and dfrA15 (resistance to trimethoprim). Most strains produced one or two bands using primers specific for the amplification of the variable region where the antibiotic-resistance genes are located, and their sizes ranged from 700 to 1250 bp. However, one strain of V. cholerae O1 isolated in 1994 gave a 2483 bp fragment, the largest fragment so far found in a class 1 integron of V. cholerae O1. No strain was positive for the intI2 gene. All V. cholerae strains, regardless of serogroup, were positive for the intI4 gene by PCR and using a colony hybridization test. Amplification of the intI4 gene by PCR yielded a 2200 bp fragment (1260 bp larger than the expected size) from three V. cholerae O139 strains isolated in 1999. Sequence analysis of this amplicon revealed an insertion of IS1359 in the middle of the intI4 gene. These data indicate that a class 1 integron is present in some clinical strains of V. cholerae isolated in Kolkata, India, and that a class 4 integron is ubiquitously distributed among V. cholerae strains regardless of serogroup.

Anti-Bacterial Agents↗
PubMed2005

The native Pseudomonas stutzeri strain Q chromosomal integron can capture and express cassette-associated genes.

The integron-gene cassette system contributes to multiple antibiotic resistance in bacteria and is likely to be of broader evolutionary significance. However, the majority of integron diversity consists of chromosomal integrons (CIs), with mostly unknown phenotypes, which are poorly characterized. A pUC-based reporter plasmid (pUS23) was developed containing a recombination site [aadB 59 base element (59-be)] upstream of promoterless aadB [gentamicin (Gm) resistance] and gfp (green fluorescence) genes, and this construct was used to investigate the recombination and expression activities of the CI in Pseudomonas stutzeri strain Q. Electroporation of pUS23 into P. stutzeri Q gave ampicillin-resistant transformants, which yielded Gm(R) green fluorescent recombinants after plating on Gm medium. Site-specific integration of pUS23 at attI was detected by PCR in 8 % of Gm(R) colonies and the frequency of attI integration was estimated as 2.0 x 10(-8) per P. stutzeri Q(pUS23) cell. RT-PCR confirmed integron-mediated expression of aadB in one recombinant strain (Q23-17) and a promoter (P(c)) was localized to the 5' end of the intI gene. The integrated pUS23 and flanking integron DNA were cloned from genomic DNA of strain Q23-17 and sequenced, confirming that site-specific integration of the entire reporter plasmid had occurred at the attI site. An insertion sequence (ISPst5; IS5 family) was discovered in the vector backbone of the reporter plasmid integrated at attI and also in a pUS23 derivative recovered as a plasmid in Escherichia coli JM109. This is the first demonstration that wild-type CIs can capture gene cassettes and express cassette-associated genes.

Ampicillin Resistance↗
PubMed2002

Occurrence of antibiotic resistance gene cassettes aac(6')-Ib, dfrA5, dfrA12, and ereA2 in class I integrons in non-O1, non-O139 Vibrio cholerae strains in India.

Molecular mechanisms of multidrug resistance in Vibrio cholerae belonging to non-O1, non-O139 serogroups isolated during 1997 to 1998 in Calcutta, India, were investigated. Out of the 94 strains examined, 22 strains were found to have class I integrons. The gene cassettes identified were dfrA1, dfrA15, dfrA5, and dfrA12 for trimethoprim; aac(6')-Ib for amikacin and tobramycin; aadA1 and aadA2 for streptomycin and spectinomycin; and ereA2 for erythromycin resistance. To our knowledge, this is the first report of the presence of dfrA5, dfrA12, aac(6')-Ib, and ereA2 cassettes in class I integrons of V. cholerae. Forty-three of 94 strains also had plasmids, and out of these, 14 contained both class I integrons and plasmids. Pulsed-field gel electrophoresis followed by Southern hybridization revealed that in the 14 plasmid-bearing strains, class I integrons resided either on chromosomes, on plasmids, or on both. Our results indicated that besides class I integrons and plasmids, a conjugative transposon element, SXT, possibly contributed to the multiple antibiotic resistance.

Blotting, Southern↗
PubMed2006

Complex genetic structures with repeated elements, a sul-type class 1 integron, and the blaVEB extended-spectrum beta-lactamase gene.

Two clinical isolates of Pseudomonas aeruginosa, TL-1 and TL-2, were isolated from a patient transferred from Bangladesh and hospitalized for osteomyelitis in Paris, France. P. aeruginosa TL-1 expressed the extended-spectrum beta-lactamase VEB-1a and was susceptible only to imipenem and colistin, while P. aeruginosa TL-2 expressed only the naturally occurring bla(AmpC) gene at a basal level and exhibited a wild-type beta-lactam resistance phenotype. In TL-1, the typical 5'-end conserved sequence (5'-CS) region of class 1 integrons usually present upstream of the bla(VEB-1a) gene was replaced by a truncated 3'-CS and a 135-bp repeated element (Re). Downstream of the bla(VEB-1a) gene, an insertion sequence, ISPa31 disrupted by ISPa30, and an orf513 sequence, belonging to a common region (conserved region 1 [CR1]) immediately upstream of the aphA-6 gene, were present. Further downstream, a second truncated 3'-CS region in direct repeat belonged to In51, an integron containing two gene cassettes (aadA6 and the OrfD cassette). Thus, the overall structure corresponded to a sul-type class 1 integron termed In121. Genetic analyses revealed that both isolates were clonally related and differed by a ca. 100-kb fragment that contained In121. Both isolates contained another integron, In122, that carried three gene cassettes: aadB, dfrA1, and the OrfX cassette. This work identifies for the first time the spread of Re-associated bla(VEB) genes located on a sul-type integron. It also reports for the first time a CR1 element in P. aeruginosa that is associated with an aminoglycoside resistance aphA-6 gene that is expressed from a composite promoter.

Alleles↗
PubMed2006

Emergence of dhfrXVb and blaCARB-4 gene cassettes in class 1 integrons from clinical Pseudomonas aeruginosa isolated in Amazon region.

Integrons play a role in horizontal acquisition and expression of genes, as well as gene reservoir, contributing for the resistance phenotype, particularly relevant to bacteria of clinical importance. We aimed to determine the composition and the organization of the class 1 integron variable region present in Pseudomonas aeruginosa clinical isolates from Brazil. Strains carrying class 1 integrons were resistant to the majority of antibiotics tested, except to imipenem and ceftazidime. Sequence analysis of the integron variable region revealed the presence of the blaCARB-4 gene into two distinct cassette arrays: aacA4-dhfrXVb-blaCARB-4 and aadB-aacA4-blaCARB-4. dhfrXVb gene cassette, which is rare in Brazil and in P. aeruginosa species, was found in one isolate. PFGE analysis showed the spread of blaCARB-4 among P. aeruginosa clones. The occurrence of blaCARB-4 and dhfrXVb in Brazil may contribute for developing resistance to clinically important antibiotics, and shows a diversified scenarium of these elements occurring in Amazon clinical settings, where no study about integron dynamics was performed to date.

Alleles↗
PubMed2003

Characterization of integron mediated antimicrobial resistance in Salmonella isolated from diseased swine.

Forty-two Salmonella isolates obtained from diseased swine were genetically characterized for the presence of specific antimicrobial resistance mechanisms. Twenty of these isolates were characterized as S. Typhimurium DT104 strains. Pulsed-field gel electrophoresis was used to determine genetic relatedness and revealed 20 distinct genetic patterns among the 42 isolates. However, all DT104 isolates fell within 2 closely related genetic clusters. Other Salmonella isolates were genetically grouped together according to serotype. All DT104 isolates displayed the penta-resistance phenotype to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline. Resistance to sulfamethoxazole, tetracycline, streptomycin, kanamycin, and ampicillin was most common among the non-DT104 Salmonella isolates. All DT104 strains contained 2 chromosomal integrons of 1000 and 1200 base pairs. The DNA sequencing revealed that the 2 integrons contained genes encoding a resistance to streptomycin and ampicillin, respectively. None of the non-DT104 strains showed the same pattern, although several strains possessed integrons of 1000 base pairs or larger. However, the majority of non-DT104 Salmonella strains did not possess any integrons. Two Salmonella isolates displayed tolerance to the organic solvent cyclohexane, indicating the possibility that they are overexpressing chromosomal regulatory genes marA or soxS or the associated multidrug efflux pump, acrAB. This research suggests that integrons contribute to antimicrobial resistance among specific swine Salmonella serotypes; however, they are not as widely disseminated among non-Typhimurium swine Salmonella serotypes as previously thought.

Animals↗
PubMedDate not supplied

[Integrons of bacteria isolated from aquatic environment].

Bacteria of the genus Pseudomonas, isolated from the water of the lakes Shira and Itkul (Republic of Khakassia, Russia) were shown to contain integrons of class 1 with gene cassettes, contained in the variable segment (sized 1 and 1.3 kb), were shown. Out of three detected integrons only one integron (in P. aeruginosa) included the sulfanilamide resistance gene contained in the 3'-conservative segment. The resistance of bacteria to kanamycin and ceftazidime was not seemingly linked with the presence of integrons. On the whole, the study revealed the presence of a significant proportion (27%) of integron-positive strains among aquatic bacteria with pronounced resistance to antibiotics.

Anti-Bacterial Agents↗
PubMed1996

Plasmid pDGO100 contains a second integron with the trimethoprim resistance gene dfrA7 as the inserted cassette.

Southern hybridization analysis of the IncC plasmid pDGO100 showed that, in addition to the well-characterized integron In7, there is a second integron which is located on a 3.6-kb BamHI fragment. This integron also possesses the qacE delta l and sulI genes typically found as part of the 3'-conserved segment of integrons. The 3.6-kb BamHI fragment, when cloned into pUC19 to form pDGO301, conferred resistance to trimethoprim as well as sulfamethoxazole. The DNA sequence of the trimethoprim resistance gene in pDGO301 was determined and it was shown that the gene was precisely inserted as a cassette in an integron with 100% identity to the trimethoprim resistance gene dfrA7.

Base Sequence↗
PubMed1998

The uvp1 gene on the R46 plasmid encodes a resolvase that catalyzes site-specific resolution involving the 5'-conserved segment of the adjacent integron In1.

The product of the uvp1 gene of the R46 plasmid, a member of the DNA invertase-resolvase family, was studied to characterize its recombination activity on the R46 plasmid. The purified Uvp1 protein specifically binds to a 256-bp DNA fragment located immediately upstream of the uvp1 gene itself, and overlapping the 5'-conserved segment (5'-CS) of the R46 integron In1. We identified on this fragment a putative resolution (res) site. Using an in vitro assay, we demonstrated the ability of the protein to resolve a synthetic cointegrate containing a direct repeat of the res site. In vivo, we obtained cointegrate resolution in Uvp1-expressing recA- cells. Sites I and II, subsites of the putative res site, lie within the outer boundary of the integron 5'-CS which is common to all the known integrons. Furthermore, a 69-bp DNA element (containing site I) is required for cointegrate resolution. We propose that this recombination mechanism protects R46 plasmid against unequal distribution following fusion with either identical or different integron-bearing plasmids. Moreover, Uvp1 might have a role in generating gene cassette diversity between the two conserved segments of the integron.

Bacterial Proteins↗