Biomedical subjects

Jorge Leitao

Publications and source records attributed to Jorge Leitao.

4 recordsLinked to original sources

PubMed2006

The presence of a conjugative Gram-positive Tn2009 in Gram-negative commensal bacteria.

OBJECTIVES: To determine whether mef(A)-msr(D) and tet(M) genes are linked in representative Gram-negative isolates and/or transferred together during conjugation. To molecularly characterize the Acinetobacter junii element and compare the structure and sequence with the non-conjugative Streptococcus pneumoniae Tn2009 element. METHODS: PCR assays, DNA-DNA hybridization and sequencing of PCR products were used. Nucleotide sequences were determined at the integration site of the mef(A) element into Tn916 and upstream and downstream flanking regions of the element. RESULTS: A total of 10 mef(A)-msr(D)- and tet(M)-positive isolates carried conjugative element(s). The A. junii Tn2009 element was indistinguishable from S. pneumoniae Tn2009. The region upstream of the A. junii Tn2009 contained an orf that was 89-91% identical to an S. pneumoniae spr1206 gene found upstream of the streptococcal Tn2009. In the A. junii, the spr1206 gene was separated by 67 bp from the end of the Tn2009, while 29 bp were found separating spr1206 from the streptococcal Tn2009. The 1201 bp downstream A. junii sequences included 913 unique sequences. CONCLUSIONS: A total of 10 different Gram-negative genera were found to carry the tet(M) genes, including the first description in three genera (Citrobacter, Proteus and Stenotrophomonas). All isolates were able to transfer the genes into > or =1 recipient with macrolide selection. Over 3000 bp were sequenced on each side of the insertion mef junction region in the A. junii and were indistinguishable from the streptococcal Tn2009. The A. junii Tn2009 element was flanked by an S. pneumoniae gene upstream and a unique sequence downstream, suggesting that the A. junii Tn2009 could be part of a larger element.

Acinetobacter↗

PubMed2006

Staphylococcus efflux msr(A) gene characterized in Streptococcus, Enterococcus, Corynebacterium, and Pseudomonas isolates.

The staphylococcal msr(A) gene, coding for a macrolide efflux protein, was identified in three new gram-positive genera and one gram-negative genus. These msr(A) genes shared 99 to 100% identity with each other and the staphylococcal gene. This study demonstrates that the msr(A) gene has a wider host range than previously reported.

Corynebacterium↗

PubMed2004

Gram-positive merA gene in gram-negative oral and urine bacteria.

Clinical mercury resistant (Hg(r)) Gram-negative bacteria carrying Gram-positive mercury reductase (merA)-like genes were characterized using DNA-DNA hybridization, PCR and sequencing. A PCR assay was developed which discriminated between the merA genes related to Staphylococcus and those related to the Bacillus/Streptococcus merA genes by the difference in size of the PCR product. DNA sequence analysis correlated with the PCR assay. The merA genes from Acinetobacter junii, Enterobacter cloacae and Escherichia coli were sequenced and shared 98-99% identical nucleotide (nt) and 99.6-100% amino acid identity with the Staphylococcus aureus MerA protein. A fourth merA gene, from Pantoeae agglomerans, was partially sequenced (60%) and had 99% identical nt and 100% amino acid identity with the Streptococcus oralis MerA protein. All the Hg(r) Gram-negative bacteria transferred their Gram-positive merA genes to a Gram-positive Enterococcus faecalis recipient with the resulting transconjugants expressing mercury resistance. These Gram-positive merA genes join Gram-positive tetracycline resistance and Gram-positive macrolide resistance genes in their association with mobile elements which are able to transfer and express in Gram-negative bacteria.

Amino Acid Sequence↗

PubMed2002

Presence and antibiotic resistance of Porphyromonas gingivalis, Prevotella intermedia, and Prevotella nigrescens in children.

BACKGROUND/AIMS: Only limited information exists about the prevalence in children of pathogens associated with periodontitis. The aim of the present study was to determine by culture whether 8-11-year-old children carry Porphyromonas gingivalis, Prevotella intermedia, and/or P. nigrescens in samples from the gingiva and/or the buccal mucosa taken before, and after caries treatment and oral hygiene instruction. A second aim was to assess the proportion of subjects who had gram-negative anaerobes carrying the tet(Q) and erm(F) genes, suggesting antibiotic resistance to tetracycline or erythromycin. METHOD: A total of 150 children provided gingival and buccal swab bacterial samples that were cultured for P. gingivalis, P. intermedia, and P. nigrescens. The species was verified using DNA-DNA hybridization with species-specific probes made from the variable region of the 16S rRNA sequences. Antibiotic-resistant genes, tet(Q) and erm(F), were identified using specific DNA-DNA hybridization with specific DNA probes. RESULTS: A total of 116 isolates of black-pigmented bacteria were cultured from 47 (31%) of 150 children. Five isolates were identified as P. gingivalis, 29 as P. intermedia, 33 as P. nigrescens, and 49 as other species. In general, the bacteria were not culturable at more than one time period. We found that 55% of these 47 children harbored black pigmented bacteria that carried either one or both of the two antibiotic-resistant genes studied (tet(Q), and erm(F)). CONCLUSION: The present study demonstrated that children not exposed to regular dental treatment carry bacteria outside the gingival sulcus that have been associated with periodontitis, and that standard treatment procedures may not clear the presence of the putative pathogens. In addition, antibiotic-resistant genes are common in identifiable gram-negative anaerobes, including putative pathogens.

Analysis of Variance↗