Genomic Distribution of Pro-Virulent cpdB-like Genes in Eubacteria and Comparison of the Enzyme Specificity of CpdB-like Proteins from Salmonella enterica, Escherichia coli and Streptococcus suis.

The cpdB gene is pro-virulent in avian pathogenic Escherichia coli and in Salmonella enterica, where it encodes a periplasmic protein named CpdB. It is structurally related to cell wall-anchored proteins, CdnP and SntA, encoded by the also pro-virulent cdnP and sntA genes of Streptococcus agalactiae and Streptococcus suis, respectively. CdnP and SntA effects are due to extrabacterial hydrolysis of cyclic-di-AMP, and to complement action interference. The mechanism of CpdB pro-virulence is unknown, although the protein from non-pathogenic E. coli hydrolyzes cyclic dinucleotides. Considering that the pro-virulence of streptococcal CpdB-like proteins is mediated by c-di-AMP hydrolysis, S. enterica CpdB activity was tested as a phosphohydrolase of 3'-nucleotides, 2',3'-cyclic mononucleotides, linear and cyclic dinucleotides, and cyclic tetra- and hexanucleotides. The results help to understand cpdB pro-virulence in S. enterica and are compared with E. coli CpdB and S. suis SntA, including the activity of the latter on cyclic-tetra- and hexanucleotides reported here for the first time. On the other hand, since CpdB-like proteins are relevant to host-pathogen interactions, the presence of cpdB-like genes was probed in eubacterial taxa by TblastN analysis. The non-homogeneous genomic distribution revealed taxa with cpdB-like genes present or absent, identifying eubacteria and plasmids where they can be relevant.

Sobre los métodos microbiológicos para la detección de la resistencia a oxacilina en Staphylococcus coagulasa negativos / About microbiological methods for detection of oxacillin resistance in coagulase-negative staphylococci

Introducción. Los Staphylococcus coagulasa negativos (SCN) forman parte de la microbiota humana y están implicados en infecciones de materiales protésicos, dispositivos intravasculares o bacteriemias relacionadas con el catéter. Presentan mayor resistencia que Staphylococcus aureus frente a las diferentes familias de antimicrobianos, y existe un aumento de la morbi-mortalidad de los pacientes cuando se instaura un tratamiento inadecuado. Material y métodos. Analizar los resultados obtenidos mediante diferentes técnicas comerciales: dos sistemas de microdilución automática en placa (MicroScan y Vitek2 Compact), aglutinación de la PBP2a con y sin inducción previa con disco de oxacilina de 1 μg, y detección del gen mecA mediante técnicas de amplificación de ácidos nucleicos, para realizar el diagnóstico de resistencia a meticilina en 170 aislados de SCN provenientes de hemocultivos. Resultados. Se detectó la resistencia a meticilina en las 170 cepas mediante MicroScan, en 167 por Vitek 2 Compact, en 115 mediante PBP2a sin inducción con oxacilina de 1μg y en 168 tras la inducción. Finalmente, se detectó la presencia del gen mecA en 167 cepas mediante amplificación de ácidos nucleicos. Conclusiones. Es necesario realizar una inducción con oxacilina 1μg antes de realizar la detección de PBP2a para evitar falsos negativos. Existe una gran variabilidad fenotípica en la expresión de la resistencia a meticilina en SCN (AU)

Introduction. Coagulase-negative staphylococci (CoNS) take part of the human skin and mucous membranes, but they are also involving in infections with the increasing use of prosthetic, in-dwelling devices or intravascular catheter-related bacteraemia. They are more resistance than Staphylococcus aureus against a wide range of antimicrobial agents, and it have been observed an increase in morbidity and mortality of patients with incorrect treatment. Material and methods. To analyze the results obtained by different commercial techniques: two automatic microdilution systems (MicroScan and Vitek2 Compact), PBP2a agglutination test, with and without 1 μg oxacillin disk induction, and detection of mecA gene by nucleic acids amplification techniques, for the diagnosis of methicillin resistance staphylococci in 170 strains of CoNS isolated from blood cultures. Results. One hundred and seventy methicillin resistance staphylococci were detected by MicroScan, 167 strains by Vitek 2 Compact, 115 strains were PBP2a positive without oxacillin induction and 168 after oxacillin induction. Finally, 167 strains were mecA gene positive detected by nucleic acids amplification techniques. Conclusions. It is necessary to do oxacillin induction before PBP2a test to avoid false negatives. There are a great variability in the phenotypic expression of methicillin resistance in CoNS (AU)