RESUMEN
Objective To analyze the distribution of class 1,2 and 3 integrons and their gene cassettes,and to explore its relationship with drug resistance in Shigella.Methods Antimicrobial susceptibility was detected by minimal inhibitory concentration (MIC) method.All the genes of integrons and gene cassettes were amplified by polymerase chain reaction (PCR).The amplicons were identified by amplified fragment length polymorphism (AFLP) and sequencing.Results Fifty seven multi-drug resistant strains were identified from a total of 62 Shigella strains (91.9％).Among multi drug resistant strains,52 strains carried integrons of class 1 (91.2 ％) and 55 strains carried integrons of class 2 (96.5％).Only 2 strains carried class 1 integrons alone,5 strains carried class 2 integrons alone and 50 strains had both class 1 and class 2 integrons.Class 3 integrons were not detected.The gene cassettes of typical class 1 integrons,dfrV and dfrA17-aadA5,were detected in 6 strains and 2 strains,respectively.Atypical class 1 integrons with gene cassettes blaOxA30 aadA1 were detected in 44 strains.The typical and atypical class 1 integrons coexisted in 6 Shigella flexneri strains.Gene cassettes for class 2 integrons were dfrA1 sat1-aadA1.Conclusions The multi-drug resistant Shigella strains are widely distributed in Ji'nan,and the atypical class 1 integrons and class 2 integrons are common in these strains.Coexistence of the two integrons is observed in some of the strains.
RESUMEN
Objective To explore the association of ATP-binding cassette (ABC) efflux pump gene Rv1217c-Rv1218c and the drug resistance of Mycobacterium tuberculosis.Methods A total of 34 Mycobacterium tuberculosis clinical isolates including 24 drug-resistance isolates which were resistant to riffampicin,isoniazid,streptomycin or ethambutol and resistant to at least one second-line antituberculosis drug,and 10 drug-sensitive isolates were involved in this study.The RNA of isolated strains was extracted and then reverse transcribed. Gene expression was performed by real-time polymerase chain reaction (PCR) and data was analyzed by t test and Logistic regression analysis.Results The expressions of Rv1217c in rifampicin-resistant group (2.13 ± 1.89,t =3.44,P＜0.01),isoniazid-resistant group ( 1.84 ± 1.86,t =3.16,P＜ 0.05),streptomycin-resistant group ( 1.86 ±1.96,t=2.78,P＜0.05) and ethambutol-resistant groups (3.36±2.35,t=3.04,P＜0.05) were all higher than sensitive isolates (0.42 ± 0.31).The expressions of Rv1218c in rifampicin-resistant group (2.54±1.84,t=3.82,P＜0.01),isoniazid-resistant group (2.34± 1.84,t=3.72,P＜0.01),streptomycin-resistant group (2.15±1.86,t=3.01,P＜0.01) and ethambutol-resistant groups (3.78± 1.78,t=4.22,P＜0.01 ) were all higher than sensitive isolates (0.65 ± 0.42).The expressions of Rv1217c and Rv1218c in multidrug resistant group were 2.74±2.07 and 3.33± 1.77,respectively,which were both higher than polydrug resistant group (0.79 ± 0.47 and 1.03 ± 0.79,respectively; t =2.91,P＜0.05 ; t =3.84,P＜0.01,respectively).Logistic regression analysis found that high Rv1217c expression was positively correlated with rifampicin resistance and negatively correlated with isoniazid resistance (both P＜ 0.01 ),while high Rv1218c expression was negatively correlated with rifampicin resistance and positively correlated with isoniazid resistance (both P＜0.01 ).High expressions of two genes were both positively correlated with ethambutol resistance and multidrug resistance (both P＜0.01 ) and not statistically correlated with streptomycin resistance (P＞0.05).Conclusions The expressions of ABC efflux pump gene,Rv1217c-Rv1218c,are correlated with multiple drug resistance.The overexpression may contribute to the multidrug resistance of Mycobacterium tuberculosis.
RESUMEN
ObjectiveTo describe the novel variants of the Smqnr family of quinolone resistance genes and their distribution in clinical isolates of Stenotrophomonas maltophilia, and investigate the relationship between Smqnr and quinolone resistance. MethodsThe identification of 442 strains of Stenotrophomonas maltophilia were performed by VITEK automated identification and susceptibility. Minimum inhibitoryconcentrationsof tigecycline,chloramphenicol,ceftazidime,compoundsulfamethoxazole,ticarcillin/clavulanic acid, levofloxacin and moxifloxacin against Stenotrophomonas maltophilia were detected by standard agar dilution method. Full length of Smqnr gene was amplified by polymerase chain reaction (PCR) and sequenced. DNAMAN software was used to compare the sequence divergence and construct the genealogical tree to analyze the phylogenetic relationships of Smqnr family. Results Stenotrophomonas maltophilia was resistant to the 7 kinds of clinical antibiotics in various extent ( from 5％ to 50％ ). Levofloxacin showed s good antibacterial activity with the resistance rate of 6. 11％ (27/442), nevertheless the best was moxifloxacin with the resistance rate of 5. 88％ (25/442). Smqnr gene was detected in 114 of 442 strains of Stenotrophomonas maltophilia[25.79％ (114/442)], including 11 known genes and 20 novel variants of the Smqnr genes ( Smqnr28-47 ) which was caused by several genes mutation changing the translation of 219 amino acids. The gene detection rate of resistant, intermediate and sensitive strains was 42. 30％ (11/26), 34. 37％ (11/32) and 23.95％ (92/384), respectively. The Smqnr gene harbored the highest detection rote (37. 78％ ) in the sensitive strains of Stenotrophomonas maltophilia with minimal inhibitory concentration of 0. 125 μg/ml. Conclusions The gene coding region of Smqnr is highly polymorphic and the novel variants of Smqnr gene are caused by several genes mutation changing the translation of 219 amino acids. Smqnr gene in Stenotrophomonas maltophilia has a high detection rate and different distribution.
RESUMEN
ObjectiveTo investigate the variations and distributions of the plasmid-mediated quinolone resistance genes in clinical isolates of Shigella and their resistance to antimicrobial agents. Methodsqnr, aac(6')-Ib-cr and qepA genes were identified by polymerase chain reaction (PCR) in 137 clinical isolates of Shigella.DNA sequencing of gene-positive strains were analyzed and the conjugation experiment was performed. The minimal inhibitory concentrations (MIC) of Shigella isolates, recipient strains and transconjugants were tested by agar dilution method for quinolones and other antimicrobial agents. The genotype of transconjugants were determined by PCR and sequencing. ResultsFour (2.9％) strains of the 137 Shigella isolates were qnr gene positive, including 3 qnrS2 positive and 1 qnrB4 positive (GenBank accession numbers of the complete sequence were JF261185 and HQ917003, respectively).Furthermore,five (3.6％) aac ( 6')-Ib-cr gene-positive strains (GenBank accession number JF261186 ) and one (0.7％) qepA gene-positive strain were identified in all isolates. The conjugation experiments were successfully carried out in six out of ten PCR-positive isolates. The MIC of transconjugants against quinolones and other antimicrobial agents increased differently compared to recipient strains. Conclusions The plasmid-mediated quinolone resistance genes are lowly prevalent in clinical isolates of Shigella. However, these resistance genes have the characteristic of horizontal transfer, which indicates that more attention should be paid to this phenomenon.
RESUMEN
Objective To understand the erythromycin resistance rate and the erythromycin resistant gene spectrum in Streptococcus pyogenes strains isolated in Shanghai.Methods The outpatient children who were diagnosed with scarlatinal in the Children's Hospital of Fudan University from November 2004 to June 2006 were enrolled and 100 strains of Streptococcus pyogenes were isolated by pharyngeal swab culture.The distributions ofermA,ermB,mefA genes were determined by polymerase chain reaction(PCR)amplification.The relationship between ermA,ermB,mefA genes and erythromycin resistance were also analyzed.Results The erythromycin and clindamycin resistance rates of Streptococcus pyogenes in Shanghai were 98%and 95%,respectively;the concordance rate of these two drugs was 97%.Among 100 strains of Streptococcus pyogenes,94 strains(94%)contained ermB gene,with 100%of erythromycinresistance rate.Sixteen(16%)contained mefA gene,with 100% of erythromycin resistance rate.ermA was not detected inall the 100 strains.The ermB and mefA genes were not found in 5 strains,among which,2 were susceptible to erythromycin and 3wereresistant to erythromycin.Only 1%of isolates was mefA genesingle positive.Conclusions There is a high erythromycin resistance rate of Streptococcus pyogenes strains isolated inShanghai,and the cross resistance to clindamycin is high.TheermB gene is important erythromycin resistancedeterminants of Streptococcus pyogenes in Shanghai.
RESUMEN
In order to understand the role of the upstream region of the Mycobacterium leprae 18-kDa gene on the gene regulation, the region was divided into two at the -50 position from the first start codon of the gene and their effect on transcription was examined by using a LacZ transcriptional reporter gene assay. The presence of each of these two regions conferred transcription repression not only on its cognate M. lepraerae 18-kDa gene promoter, but also on a heterologous promoter such as the Mycobacterium bovis BCG hsp65 gene promoter. Moreover, it was found that these regions could confer transcription repression activity in both cases in an orientation-independent manner. Thus, these results indicate that the upstream region of the M. leprae 18-kDa gene harbors transcription repression responsive element(s) acting as an operator and can be further divided into two separately functional regions, suggesting a bipartite structure of the element(s). The identification of transcription repression activity of the upstream region in the M. leprae 18-kDa gene will contribute greatly for the understanding of the 18-kDa gene regulation mechanism, and provide also useful information for the manipulation of mycobacterium gene expression.
Asunto(s)
Proteínas Bacterianas/genética , Regulación hacia Abajo/genética , Regulación Bacteriana de la Expresión Génica , Mycobacterium leprae/genética , Elementos de Respuesta/genética , Transcripción GenéticaRESUMEN
Objective To study the relationship between the mutation of the inverted repeat (IR) gene in the multiple transferable resistant (mtr) system and multiple antibiotic resistance of Neisseria gonorrhoeae. Methods The antimicrobial susceptibilities of isolated strains were tested. An agar plate dilution method was used to determine the minimum inhibitory concentrations. The target genes were amplified by PCR and subjected to sequencing. Results No mutation was found in the IR gene of either of 2 sensitive or 5 penicillin-resistant Neisseria gonorrhoeas strains. Among the 17 multiple-antibiotic-resistant strains, a strain with both azithromycin- and penicillin-resistance had T/A and T/A insertions, and another had A/T deletion. Conclusion Mutations in the IR gene of the mtr system of Neisseria gonorrhoeae might result in multiple antibiotic resistance.
RESUMEN
Objective To investigate the variability of katG gene in Mycobacterium tuberculosis strains isolated in China,and screen the new isoniazid resistance related mutation sites meanwhile. Methods 429 clinical Mycobacterium tuberculosis isolates were included in our research.PCR-RFLP method was applied to screen for the S315T mutation firstly.Whole katG gene sequencing was done in those resistant strains without S315T mutation to explore the unknown mutated sites associated with isoniazid resistance.Results S315 mutation were found in 76.9% (166/216)resistant stains. Complete or part deletion of katG gene was detected in 2 highly-resistant isolates.Sequencing in 48 resistant strains showed that 315,463 and 234 sites were the most frequent mutation sites,other sites were also found but distributed dispersedly with low prevalence rate as less than 5%.Besides S315T, S315N were also common in China (8.7%).The most common variation is still site mutation.Con- clusions The results from the study of genotypes associated with most common clinical resistant phe notypes can be helpful to develop new methods to detect the resistant M.tuberculosis.
RESUMEN
Objective To investigate the effects of staphylococcal enterotoxin A SEA gene on target cells mediated by replicative-deficient recombinant adenovirus vector. Methods Lymphocytes of C57BL/6 mice were infected with various titers of recombinant adenoviruses. Supernatants were collected after 12 h, 24 h, 48 h, 72 h, 96 h, 120 h and 144 h of incubation and analyzed for proliferation of lymphocytes by MTT assay. IL-2 level in the culture supernatants was measured with ELISA. The killing effect of lymphocytes was also observed by MTT assay. Results Proliferation response and elevated levels of IL-2 were observed in experimental group. The killing effect on B16 cells was stronger in experimental group, which seemed to be dose-dependent with the increase of ratio of lymphocytes/target cells. Conclusions SEA gene can be expressed in lymphocytes of C57BL/6 mice mediated by replicative-deficient recombinant adenovirus vector. The expressing products can activate lymphocytes of C57BL/6 mice, which kill B16 cells in vitro.