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1.
In Salmonella enterica, resistance to antibiotics can be caused by the presence of SGI1, transposons or conjugative plasmids. In this study we were interested in the relative contribution of these genetic elements to the antibiotic resistance of S. enterica isolates collected within a single year in the Czech Republic from animal sources. Altogether 123 antibiotic-resistant isolates belonging to 16 different S. enterica serovars were classified into 3 groups according to the presence of SGI1 and the presence of integrons. The first group consisted of 62 strains in which neither SGI1 nor class 1 integron was detected. A high diversity among serovars and resistance phenotypes was found in this group. The second group consisted of 56 strains positive for both the SGI1 and class 1 integron, out of which 55 belonged to serovar Typhimurium and one to a nonmotile serovar [4,12] which harboured the SGI1-B variant. The third group comprised five strains which were positive for class 1 integron but negative for the SGI1. Sequencing of the integrons in these isolates identified integron with sat1 and aadA1 gene cassettes in S. Sandiego and S. Pullorum, dfrA1 and aadA1 gene cassettes in S. Typhimurium integron, and aadA21 gene cassette in S. Braenderub and S. Zanzibar.  相似文献   

2.
Zheng F  Lin G  Zhou J  Cao X  Gong X  Wang G  Qiu C 《Veterinary microbiology》2012,156(3-4):434-438
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3.
查明辽宁地区整合子在猪源大肠埃希菌中的分布及整合子携带耐药基因盒的种类,可为该病的综合防控提供科学依据。本研究利用整合酶基因PCR扩增法检测整合子,并对整合子可变区进行扩增测序。结果表明,71.43%(40/56)的菌株为Ⅰ类整合子阳性,1.79%(1/56)的菌株同时为Ⅰ类和Ⅱ类整合子阳性,未检测到Ⅲ类整合子;87.8%(36/41)的菌株表现为Ⅰ类整合子可变区扩增阳性,扩增产物大小在116bp~2 307bp之间,100%(1/1)菌株表现为Ⅱ类整合子可变区扩增阳性,大小为2 106bp;整合子可变区含有编码对氨基糖苷类抗生素耐药的基因(aadA1、aadA2、aadA5、aadA22、aadB、aacA4和sat2),编码对磺胺类抗生素耐药的基因(dfrA1、dfrA12、dfrA17),编码对氯霉素抗生素耐药的基因(cmlA1、cmlA6)。因此,整合子在大肠埃希菌中广泛存在,辽宁地区大肠埃希菌中整合子主要携带编码对氨基糖苷类、磺胺类和氯霉素耐药基因盒。  相似文献   

4.
In our studies on FimH adhesins expressed by different Salmonella serovars, we cloned and sequenced the fimH genes from Salmonella enterica ssp. Enterica ser. Gallinarum biovar Gallinarum and S. enterica ssp. Enterica ser. Gallinarum biovar Pullorum. Comparison of the nucleotide sequences revealed the presence of a single-nucleotide polymorphism (SNP) at position 544 bp from the A of the start codon of the fimH open reading frame (ORF). Further analysis of the restriction enzyme sites in fimH gene showed that the SNP at this position is responsible for a sequence specifically recognized by SacI in S. Gallinarum biovar Gallinarum only, making it possible to differentiate both biovars with the use of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Digestion of PCR amplicons of the fimH gene from S. Gallinarum biovar Gallinarum strains with SacI gave two DNA fragments of 554 and 472 bp and only one fragment of 1026 bp for S. Gallinarum biovar Pullorum. This allows a clear differentiation between these two biovars.  相似文献   

5.
对河南省鸡源大肠杆菌Ⅰ类、Ⅱ类和Ⅲ类整合子及其携带的耐药基因盒进行了分子流行病学研究。结果表明：51株鸡源大肠杆菌中86．3％（44／51）检出Ⅰ类整合子,3．9％（2／51）检出Ⅱ类整合子,未检出Ⅲ类整合子。Ⅰ类整合子共检出5种类型的基因盒,分剐是sat基因盒（100％）,dfrAl＋aadAl基因盒（45．4％,20／44）,dfrAl7＋aadA5基因盒（22．5％,9／44）,dfrAl＋sat＋aadA2基因盒（6．8％,3／44）和4800bp未知基因盒（27．3％,12／44）,其中4800bp未知基因盒的下游携带有ESBLCTX-M基因,Ⅱ类整合子的基因盒携带dfrAl＋sat＋aadAl3种基因。  相似文献   

6.
To assess the prevalence of antimicrobial resistance and three classes of integrons in Escherichia coli (E. coli) strains (n = 57) isolated from bovine endometritis in Inner Mongolia of China, antimicrobial susceptibility and the presence of three types of integrons were characterized. Most isolates were susceptible to ceftiofur, furazolidone, ciprofloxacin and enrofloxacin, while 57 isolates were all resistant to sulfamethoxydiazine and trimethoprim. High resistant incidence rates were exhibited to sulfadiazine, tetracycline, oxytetracycline, cefazolin, chloramphenicol. Forty-six of 57 E. coli strains were resistant to above 10 antibiotics (80.70%). The integrase gene and gene cassettes of integrons were amplified by PCR. DNA sequencing and analysis were used to identify the genetic content of the integron-variable regions. Neither class II nor class III integron was detected, while 36.8% (n = 21) of the isolates were positive for the presence of intI1 gene. Analysis of gene cassettes revealed that six gene cassettes were found, which encoded resistance to trimethoprim (dhfr, dhfrI, dfrA17) and aminoglycosides (aadA1, aadA2, aadA5). Among them, the gene cassette array dfrA17–aadA5 was found most prevalent (66.7%). The resistance profile of positive-integron isolates was relatively broad and they were resistant to more than eight antimicrobials (n ? 8). The correlation analysis revealed the incidence of integrons among the isolates were related to the multiple antibiotic resistance profile, indicating integrons play an important role in the dissemination and spread of the antimicrobial resistant strains.  相似文献   

7.
Salmonella enterica subsp. enterica serovar Gallinarum biovars Gallinarum and Pullorum cause fowl typhoid and pullorum disease in avian species, respectively, and have been of considerable economic importance to the poultry industry in parts of the world. The definitive diagnosis of these diseases can be made only by isolation and identification of the causative agent. However, rapid identification of biovars Gallinarum and Pullorum is not easily feasible due to their common antigenic structure and genomic sequence similarity. We developed a duplex polymerase chain reaction (PCR) assay to identify and discriminate between strains of biovars Gallinarum and Pullorum. Duplex PCR primers were designed to target polymorphic regions of glgC and speC genes showing multiple mutations in the sequenced S. enterica subsp. enterica serovar Gallinarum 287/91 genome and were applied to the specific identification of biovars Gallinarum and Pullorum. Boiled lysates of 131 reference and field strains of Salmonella and other related Gram-negative bacteria were tested to validate the duplex PCR assay. All strains of biovars Gallinarum (n=53) and Pullorum (n=21) tested were correctly identified based on this assay (100% sensitivity) while the other strains (n=57) were PCR negative (100% specificity). These results demonstrate that a highly accurate biovar-specific duplex PCR assay can be performed for the rapid identification and discrimination of biovars Gallinarum and Pullorum from field isolates.  相似文献   

8.
To assess the prevalence of antimicrobial resistance and class I integrons in Escherichia coli strains (n=58) isolated from bovine mastitis in Inner Mongolia, antimicrobial susceptibility and the presence of various types of integrons were characterized. Most isolates were susceptible to amikacin, colistin, ceftazidime, gentamicin and kanamycin, while those also exhibited high resistant incidence rates to ampicillin, amoxicillin, sulfadiazine and sulfamethoxydiazine. The integrase gene of integrons was amplified by PCR using degenerate primers. The integrons were confirmed by restriction fragment length polymorphism (RFLP) analysis of positive PCR products. Neither class II nor class III integron was detected, while 56.90% (n=33) of the isolates were positive for the presence of intI1 gene. Sequencing analysis of gene cassettes revealed that seven gene cassettes were found, which encoded resistance to trimethoprim (dfrA1 and dfrA17), aminoglycosides (aacA4, aadA1 and aadA5) and chloramphenicol (catB3), respectively. Of them, the gene cassette array dfrA17-aadA5 was found most prevalent (62.96%). The percentage of positive-integron among the isolates whose resistant profile was relatively broad (n> or =7) is 100.00%, while the one in narrow-profile isolates (n=2-6) is 30.56%. The correlation analysis revealed the incidence of integrons among the isolates were highly related to the resistant profile, indicating integrons play an important role in the dissemination and spread of the antimicrobial resistant strains.  相似文献   

9.
By PCR using the ant(3")-Ia primer pair the aadA gene was detected in 34 streptomycin- and spectinomycin-resistant Salmonella enterica serotype Typhimurium strains. Out of them 12 belonged to DT104 and 22 to non-DT104 phage type. Using different primer combinations it was demonstrated that this gene was integron-associated in all cases: in the DT104 strains it was generally contained by a 1 kb integron while in the majority of the non-DT104 strains by a 2.05 kb (less often by a 1.9 or 1 kb) integron. In the case of integrons carrying multiple cassettes the cassette containing the aadA gene was located closer to the 3' end of the integron. The aadA genes of DT104 and non-DT104 strains were different: in the former group the aadA2 gene, while in the latter group (constituted by strains of five different phages types as well as unclassifiable and untypable strains) the aadA1 gene could be identified. The RH50/RH51 primer pair described by Collis and Hall (1992) proved to be suitable for rapid discrimination between the aadA1 and aadA2 genes on the basis that the RH51 primer bound exclusively to the aadA2 gene.  相似文献   

10.
Salmonella enterica serovar Typhimurium (S. Typhimurium) isolated and identified from swine were subjected for the analysis of antibiotic resistance pattern and clinically important class 1 and 2 integrons. In addition, S. Typhimurium isolates exhibiting ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, tetracycline and florfenicol (ACSSuTF) resistance pattern as described in most Salmonella enterica serotype Typhimurium definitive type 104 (DT104) were characterized by polymerase chain reaction. All the isolates were resistant to more than four antibiotics and showed the highest resistance to streptomycin (94.1%), followed by tetracycline (90.1%), ampicillin (64.7%), chloramphenicol (56.8%) and gentamicin (54.9%). MIC value for the ten isolates ranged between 0.125-2 mug/ml for ciprofloxacin. Among the beta-lactams used, only one of the isolate exhibited resistance to ceftiofur (MIC 8 microg/ml). Sixty eight percent of these multi drug resistance (MDR) S. Typhimurium isolates carried clinically important class 1 integron with 1kb (aadA) and/or 2kb (dhfrXII-orfF-aadA2) resistance gene cassettes. This study reports the increasing trend of multi drug resistance (MDR) S. Typhimurium with clinically important class 1 integron in pigs. In addition, emergence of the ACSSuTF-type resistance in S. Typhimurium PT other than DT104 may limit the use of resistance gene markers in its detection methods by PCR.  相似文献   

11.
目的为了解猪源大肠杆菌中Ⅰ型整合子的流行情况,探讨Ⅰ型整合子与大肠杆菌耐药表型的相关性。方法采用微量肉汤稀释法测定119株猪源大肠杆菌对8类14种抗菌药物的耐药性,并采用PCR法检测猪源大肠杆菌Ⅰ型整合酶基因(int I1)并扩增其可变区,对PCR产物进行酶切分析,测序分析整合子可变区携带的耐药基因盒。结果 119株大肠杆菌耐药现象十分严重,对四环素、磺胺异恶唑、新诺明全部耐药,所有菌株均呈多重耐药。119株猪源大肠杆菌中有92株含Ⅰ型整合子,检出率77.31%。扩增出7类大小不同的基因盒插入区片段,范围为1008bp～3149bp。7类Ⅰ型整合子在119株猪源大肠杆菌中存在13种流行组合。78.15%大肠杆菌菌株的Ⅰ型整合子携带2种或2种以上的基因盒,其中以携带编码氨基糖苷类药物耐药基因(aadA1、aadA2、aadA5、aadA22、aadB)最多,其次为编码磺胺类药物耐药基因(dfrA1、dfrA12、dfrA17、dfrA27),此外还携带编码利福平、林可霉素和氯霉素的基因lnuF、cmlA6、aar-3、orf。结论Ⅰ型整合子普遍存在于大肠杆菌中,且呈流行上升趋势;Ⅰ型整合子参与耐药及多重耐药,但单株细菌携带的耐药基因盒与其耐药表型无对应关系。  相似文献   

12.
To establish a molecular differentiation method for Salmonella enterica subsp. enterica, a hyper-variable region of RNA polymerase beta-subunit (rpoB) of S. enterica subsp. enterica (I), serotype Typhimurium, and Escherichia coli were investigated through comparison of nucleotide sequence of the region. The hyper-variable region was identified at 612-937 of the gene. After PCR amplification of the region in the 17 serotypes and two biotypes of serotype Gallinarum of S. enterica subsp. enterica (I), the nucleotide sequences of the region were determined and compared. All serotypes were distantly related to E. coli with 82.8-84.7% identities in nucleotide sequence while showing 96.6-100% identities with each other. According to the phylogenetic analysis based on the sequenced region with the neighbor-joining method, relatedness of biotype Gallinarum to serotype Enteritidis and biotype Pullorum was determined. Biotype Gallinarum was more closely related to serotype Enteritidis than biotype Pullorum. These results suggested that the 612-937 variable region of rpoB might be useful for molecular evolutionary analysis of serotypes of S. enterica subsp. enterica (I).  相似文献   

13.
猪源大肠杆菌耐药性与I型整合子关系研究   总被引：1，自引：0，他引：1  
目的为了解猪源大肠杆菌中I型整合子的流行情况,探讨I型整合子与大肠杆菌耐药表型的相关性。方法采用微量肉汤稀释法测定119株猪源大肠杆菌对8类14种抗菌药物的耐药性,并采用PCR法检测猪源大肠杆菌I型整合酶基因（int11）并扩增其可变区,对PCR产物进行酶切分析,测序分析整合子可变区携带的耐药基因盒。结果119株大肠杆菌耐药现象十分严重,对四环素、磺胺异恶唑、新诺明全部耐药,所有菌株均呈多重耐药。119株猪源大肠杆菌中有92株含I型整合子,检出率77．31％。扩增出7类大小不同的基因盒插入区片段,范围为1008bp-3149bp。7类I型整合子在119株猪源大肠杆菌中存在13种流行组合。78．15％大肠杆菌菌株的I型整合子携带2种或2种以上的基因盒,其中以携带编码氨基糖苷类药物耐药基因（aadA1、aadA2、aadA5、aadA22、aadB）最多,其次为编码磺胺类药物耐药基因（dfrA1、dfrA12、dfrA17、dfrA27）,此外还携带编码利福平、林可霉素和氯霉素的基因1nuF、cm1A6、aar-3、off.结论I型整合子普遍存在于大肠杆菌中,且呈流行上升趋势;I型整合子参与耐药及多重耐药,但单株细菌携带的耐药基因盒与其耐药表型无对应关系。  相似文献   

14.
The aim of this study was to determine antimicrobial resistance of Aeromonas hydrophila isolated from farmed Nile Tilapia. A total of 50 A. hydrophila isolates from clinical cases were screened for the presence of class 1, 2 and 3 integrons and all the strains resistant to enrofloxacin and/or ciprofloxacin (n=19) examined for mutation in the quinolone resistance-determining regions (QRDRs) of gyrA and parC. The intI1 gene was detected in 23 A. hydrophila strains (46%) but no intl2 and intl3 were detected. Among these, 14 isolates (60.8%) carried gene cassettes inserted in variable regions i.e., partial aadA2, aadA2, dfrA1-orfC and dfrA12-aadA2, of which the most common gene cassette array was dfrA12-aadA2 (26.09%). Conjugal transfer of class 1 integrons with resistance gene array was detected. All the A. hydrophila strains resistant to enrofloxacin and/or ciprofloxacin possessed mutations in the QRDRs of gyrA and parC. Only a Ser-83-Ile substitution was identified in GyrA and only a Ser-80-Ile amino change was found in ParC. The data confirms that A. hydrophila from farm-raised Nile Telapia serve as a reservoir for antimicrobial resistance determinants.  相似文献   

15.
In our studies on FimH adhesins expressed by different Salmonella serovars, we cloned and sequenced the fimH genes from Salmonella enterica ssp. Enterica ser. Gallinarum biovar Gallinarum and S. enterica ssp. Enterica ser. Gallinarum biovar Pullorum. Comparison of the nucleotide sequences revealed the presence of a single‐nucleotide polymorphism (SNP) at position 544 bp from the A of the start codon of the fimH open reading frame (ORF). Further analysis of the restriction enzyme sites in fimH gene showed that the SNP at this position is responsible for a sequence specifically recognized by SacI in S. Gallinarum biovar Gallinarum only, making it possible to differentiate both biovars with the use of polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP). Digestion of PCR amplicons of the fimH gene from S. Gallinarum biovar Gallinarum strains with SacI gave two DNA fragments of 554 and 472 bp and only one fragment of 1026 bp for S. Gallinarum biovar Pullorum. This allows a clear differentiation between these two biovars.  相似文献   

16.
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.  相似文献   

17.
During a study on Salmonella enterica subsp. enterica serovar Derby from slaughter-age pigs in Brazil, two epidemiologically unrelated multi-resistant S. Derby isolates were found to carry a class 1 integron with a single gene cassette. Sequence analysis confirmed that this gene cassette harboured an aadA2 gene. The aadA2 gene codes for an aminoglycoside adenyltransferase, which mediates resistance to the aminoglycoside streptomycin and the aminocyclitol spectinomycin. Although aadA2 gene cassettes are widely distributed among Salmonella, database searches identified an AadA2 protein indistinguishable from that of S. Derby only in single isolates of S. enterica subsp. enterica Enteritidis from France and S. enterica subsp. enterica Typhimurium from Japan. Structural analysis of the 59-base element revealed at least one base pair difference between the 59-base element of the aadA2 cassette from S. Derby and any of the 59-base elements deposited in the databases.  相似文献   

18.
To investigate the prevalence and molecular characterization of class Ⅰ integron in Escherichia coli isolated from beef cattle, and analyze the relationship between integron and antimicrobial resistance, susceptibilities to 11 antimicrobials were conducted on 92 isolates, the presence and characterization of class Ⅰ integrons and inserted gene cassettes were performed using PCR combined with sequencing analysis. The results showed that 29 isolates had been detected positive for class Ⅰ integron integrase gene (intⅠ1) among 92 isolates, and aadA1 and dfrA17＋aadA5 were the most prevalent gene cassette arrays detected. The resistance rates of 92 isolates to ampicillin, streptomycin, sulfisoxazole and tetracycline were all more than 45.0%. As revealed by analyzing the association between resistance phenotypes and class Ⅰ integron, isolates that contained the class Ⅰ integron were significantly highly resistant to ampicillin, chloramphenicol, streptomycin, sulfisoxazole and sulfamethoxazole-trimethoprim (P<0.05), but not to quinolones and amoxicillin/clavulanic acid. The conclusion was that E.coli isolated from beef cattle were seriously resistant to antimicrobials,and integron/cassettes widely existed. The presence of integrons and the association of antimicrobial resistance determinants with transferable elements might play a crucial role in the dissemination of antibiotic resistance among E.coli. Data reported here clearly emphasized the need for a stricter application of antimicrobials restriction policies in feedlot setting.  相似文献   

19.
The aim of the present study was to contribute to the knowledge on extended-spectrum beta-lactamases (ESBL's), AmpC beta-lactamases and integrons in Enterobacteriaceae isolated from horses, which is still limited. The susceptibility of 1581 clinical isolates from animals to ceftiofur was tested. Most of these isolates (n=1347) originated from horses. Seven ceftiofur-resistant equine isolates (four Escherichia coli and three Klebsiella pneumoniae) were identified and all seven were multidrug-resistant. These isolates were further studied for the presence of ESBL's, AmpC beta-lactamases and class 1 integrons. The potential for the horizontal transfer of resistance genes among these clinical isolates was also studied. ESBL-type resistance genes were found in five isolates, AmpC-type genes in one isolates and integrons in six isolates. Nucleotide sequence analysis revealed that the isolates carried the bla(CTX-M-1), bla(CMY-2), bla(TEM-1) and/or bla(SHV-1) genes. This is the first report describing the in vitro conjugal transfer of the bla(CTX-M-1) genes from a clinical E. coli isolate to Salmonella isolates. Gene cassettes encoding resistance to aminoglycosides (aadA1, aadA2 and aadA5), and trimethoprim (dfrA1, drfA12 and dfrA17) were found on the integrons present in the isolates. The cassette arrays of the dfrA17-aadA5 and dfrA1-aadA1 genes in the two integrons of a single E. coli isolate have not yet been described before. To our knowledge this is the first report on ESBL's and AmpC beta-lactamases in equine E. coli and Klebsiella isolates.  相似文献   

20.
Salmonella enterica serotype Gallinarum (S. Gallinarum) is the causative agent of fowl typhoid (FT) in chickens. FT is a severe systemic disease of chickens causing heavy economic losses to the poultry industry through mortality, reduced egg production and culling of precious breeding stocks. In this study, a metC (encoding cystathionine beta lyase) mutant was produced from a virulent strain of S. Gallinarum by Mini-Tn5 insertional inactivation. The mutant was significantly attenuated in virulence for 1-day-old White Leghorn chickens. Inactivation of metC resulted in 10(4)-fold increase in the LD50 when compared with the wild type parent. The metC mutant showed an in vivo competitiveness defect in the challenged chickens and significantly lower (P < 0.01) bacterial burden in the reticuloendothelial organs when compared with the wild-type parent. These results indicate that metC gene is important for virulence of S. Gallinarum in chickens.  相似文献   

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