Isolation and molecular characterization of a cax gene from Capsella bursa-pastoris

A new cation exchangers (CAXs) gene was cloned and characterized from Capsella bursa-pastoris by rapid amplification of cDNA ends (RACE). The full-length cDNA sequence of cax from C. bursa-pastoris (designated as Cbcax51) was 1754 bp containing a 1398 bp open reading frame encoding a polypeptide of 466 amino-acid residues with a calculated molecular mass of 50.5 kDa and an isoelectric point of 5.69. The predicted CbCAX51 contained an IMP dehydrogenase/GMP reductase domain, two Na+/Ca2+ exchanger protein domains. Comparative and bioinformatics analyses revealed that CbCAX51 showed extensive homology with CAX from other plant species. The expression analysis by different treatments indicated that Cbcax51 could be activated by cold triggering and was related to the cold acclimation process, but its expression is regulated negatively by drought and not affected by ABA or salt.

Tetracycline and oxytetracycline resistance determinants detected in Bacillus cereus strains isolated from honey samples / Detección de determinantes de resistencia a tetraciclina y oxitetraciclina en cepas de Bacillus cereus aisladas de muestras de miel

The aim of this study was to investigate the presence of tetracycline and oxytetracycline resistance determinants in Bacillus cereus strains isolated from honey samples. Of a total of 77 isolates analyzed, 30 (39%) exhibited resistance to tetracyclines according to the results of a disk diffusion method. Resistant strains (n=30) were screened by PCR for the presence of the resistant determinants tetK, tetL, tetM, tetO, tetW, otrA and otrB and their MIC values for tetracycline, oxytetracycline and minocycline were assessed. According to the PCR results, 23 isolates (77%) presented at least one tetracycline or oxytetracycline resistance determinant. The tetK genotype was present in 10 isolates while the tetL, tetM, and otrA genotypes were present in 3, 2, and 5 isolates, respectively. In addition, 2 isolates of the tetK plus tetM genotype, 1 of the tetK plus tetL genotype, and 1 of the tetK plus otrA genotype were found. All isolates were tetW, tetO and otrB negatives. On the other hand, 7 isolates (23%) showed a tetracycline-resistant and/or minocyclineresistant phenotype (MIC) but did not carry any of the tet or otr determinants investigated in this study. This research has shown that B. cereus isolates from honey samples contain a variety of tetracycline and oxytetracycline resistance genes, including the tetK and tetL determinants which encode for efflux proteins, and tetM and otrA, which encode for ribosomal protection proteins. These findings indicate that strains isolated from honeys could represent a reservoir for tetracycline resistance genes. To our knowledge, this is the first report of tetracycline-resistant and oxytetracyclineresistant B. cereus strains carrying the tetK determinant, and also the first report of oxytetracycline-resistant and tetracycline- resistant Bacillus species carrying the otrA determinant.

El objetivo del presente estudio ha sido investigar la presencia de diversos determinantes de resistencia a tetraciclina y oxitetraciclina en las poblaciones de Bacillus cereus presentes en la miel. De un total de 77 aislamientos evaluados, 30 (39%) resultaron resistentes a tetraciclina y/o minociclina de acuerdo con los resultados de las pruebas de difusión en disco. Dentro del grupo que presentó un fenotipo resistente, se investigó la presencia de los determinantes tetK, tetL, tetM, tetO, tetW, otrA y otrB por PCR y se determinaron los valores de CIM para tetraciclina, oxitetraciclina y minociclina. De acuerdo con los resultados obtenidos por PCR, 23 aislamientos (77%) presentaron al menos un determinante de resistencia a tetraciclina o a oxitetraciclina; el genotipo tetK se encontró en 10 de esos aislamientos, mientras que los genotipos tetL, tetM y otrA se hallaron en 3, 2 y 5 aislamientos, respectivamente. Ningún aislamiento presentó los genotipos tetW, tetO ni otrB. Adicionalmente, se encontraron los genotipos tetK plus tetM (2 aislamientos); tetK plus tetL (1 aislamiento) y tetK plus otrA (1 aislamiento). Por otra parte, 7 cepas (23%) resultaron resistentes a tetraciclina, oxitetraciclina y/o minociclina por CIM, pero no presentaban ninguno de los determinantes tet u otr estudiados. Estos resultados indican la existencia de un alto porcentaje de cepas de B. cereus aisladas de miel con genes de resistencia a tetraciclina y oxitetraciclina, incluyendo los determinantes tetK, tetL, tetM y otrA. Este estudio constituye el primer registro de la presencia del determinante tetK de resistencia a tetraciclina en B. cereus, como así también la presencia del determinante otrA dentro del género Bacillus.

The involvement of tetA and tetE tetracycline resistance genes in plasmid and chromosomal resistance of Aeromonas in Brazilian strains

This study analyzed the involvement of tetA and tetE genes in the tetracycline resistance of 16 strains of genus Aeromonas, isolated from clinical and food sources. Polymerase chain reactions revealed that 37.5 percent of the samples were positive for tetA, and also 37.5 percent were tetE positive. One isolate was positive for both genes. Only the isolate A. caviae 5.2 had its resistance associated to the presence of a plasmid, pSS2. The molecular characterization of pSS2 involved the construction of its restriction map and the determination of its size. The digestion of pSS2 with HindIII originated two fragments (A and B) that were cloned separately into the pUC18 vector. The tetA gene was shown to be located on the HindIII-A fragment by PCR. After transforming a tetracycline-sensitive strain with pSS2, the transformants expressed the resistance phenotype and harbored a plasmid whose size was identical to that of pSS2. The results confirmed the association between pSS2 and the tetracycline resistance phenotype, and suggest a feasible dissemination of tetA and tetE among strains of Aeromonas. This study suggests the spreading tetA and tetE genes in Aeromonas in Brazil and describes a resistance plasmid that probably contributes to the dissemination of the resistance.