SPM-1-producing Pseudomonas aeruginosa: analysis of the ancestor relationship using multilocus sequence typing, pulsed-field gel electrophoresis, and automated ribotyping.

In Brazil, the spread of an endemic clone of SPM-1-producing Pseudomonas aeruginosa has been reported. Recently, a higher genomic variety has been observed among the SPM-1-producing P. aeruginosa isolates. The principal aim of this study was to analyze through multilocus sequence typing (MLST) analysis whether the recently isolated SPM-1-producing P. aeruginosa descend or not from a common ancestor. A total of 50 SPM-1-producing P. aeruginosa exhibiting 11 distinct ribotyping genotypes collected from 11 different Brazilian cities were studied. Three IMP-1-producing P. aeruginosa and two non-metallo-beta-lactamase-producing P. aeruginosa isolates were included in the study as controls. For assignment of allelic numbers and subsequent determination of sequence type (ST), the obtained sequences were compared to existing sequences in the MLST database (www.pubmlst.org/paeruginosa). The eBURSTv3 software was used in this study for establishing the evolutionary relationship and phylogenetic analysis. A total of 5 different STs were identified among 55 P. aeruginosa isolates. All of the SPM-1-producing P. aeruginosa presented an identical allelic profile (ST277), except for one strain. The three IMP-1-producing P. aeruginosa strains were classified as belonging to the ST593, whereas the non-metallo-beta-lactamase-producing P. aeruginosa showed two new distinct STs, ST594 and ST595. Our study shows that SPM-1-producing P. aeruginosa isolates as well as the IMP producers evaluated in this study descend from a common ancestor.

First description of bla(CTX-M-14)- and bla(CTX-M-15)-producing Escherichia coli isolates in Brazil.

We evaluated the antimicrobial resistance patterns and molecular characteristics of 11 extraintestinal Escherichia coli strains and 1 intestinal E. coli from human infections collected in Brazil. Two E. coli strains were nonsusceptible to extended spectrum cephalosporins (cefotaxime, ceftazidime, and cefepime); one isolated from diarrhea carried bla(CTX-M-14) and bla(TEM-1), whereas the other, isolated from tracheal secretion, carried bla(CTX-M-15) and bla(OXA-1). Five E. coli strains showed resistance to quinolones. Integrase associated with class 1 integron (intl1) was detected in 8 of the 12 E. coli strains belonging to various serotypes and this gene was carried by plasmids showing similar size. Pulsed-field gel electrophoresis showed that E. coli strains were genetically diverse, and phylogenetic grouping showed that the E. coli strains belonged to groups A, B2, and D (33.3%), respectively. This is the first report of E. coli isolates carrying bla(CTX-M-14) and bla(CTX-M-15) in Brazil. The presence of mobile elements containing antimicrobial resistance genes is worrisome since it could promote the dissemination of resistance and lead to the acquisition of resistance to other antimicrobials agents such as the carbapenems.

Molecular characterization of serine-, alanine-, and proline-rich proteins of Trypanosoma cruzi and their possible role in host cell infection.

We previously reported the isolation of a novel protein gene family, termed SAP (serine-, alanine-, and proline-rich protein), from Trypanosoma cruzi. Aided by the availability of the completed genome sequence of T. cruzi, we have now identified 39 full-length sequences of SAP, six pseudogenes and four partial genes. SAPs share a central domain of about 55 amino acids and can be divided into four groups based on their amino (N)- and carboxy (C)-terminal sequences. Some SAPs have conserved N- and C-terminal domains encoding a signal peptide and a glycosylphosphatidylinositol anchor addition site, respectively. Analysis of the expression of SAPs in metacyclic trypomastigotes by two-dimensional electrophoresis and immunoblotting revealed that they are likely to be posttranslationally modified in vivo. We have also demonstrated that some SAPs are shed into the extracellular medium. The recombinant SAP exhibited an adhesive capacity toward mammalian cells, where binding was dose dependent and saturable, indicating a possible ligand-receptor interaction. SAP triggered the host cell Ca2+ response required for parasite internalization. A cell invasion assay performed in the presence of SAP showed inhibition of internalization of the metacyclic forms of the CL strain. Taken together, these results show that SAP is involved in the invasion of mammalian cells by metacyclic trypomastigotes, and they confirm the hypothesis that infective trypomastigotes exploit an arsenal of surface glycoproteins and shed proteins to induce signaling events required for their internalization.