Biology subjects

Bou, G.

Publications and source records attributed to Bou, G..

5 recordsLinked to original sources

bioRxiv2026

Widespread occurrence of ampicillin-susceptible Enterococcus faecium and Enterococcus lactis clinical isolates with low MICs to cephalosporins from Spain and Portugal

Reduced cephalosporin resistance in Enterococcus faecium has traditionally been reported in laboratory mutants and, more recently, in a single clinical ampicillin-susceptible (AmpS) isolate. Herein, we investigated whether this phenotype is widespread by analysing 95 clinical enterococcal isolates (78 AmpS and 17 ampicillin resistant [AmpR]) collected from three hospitals in Spain and Portugal (2009-2025). Low ceftriaxone MICs ([≤]4 mg/L) were detected in 19/51 (37.3%) AmpS E. faecium and 7/27 (25.9%) E. lactis but in none of the AmpR isolates. Low ceftriaxone MICs were associated with older patient age in both species and with prior ampicillin therapy in E. faecium, but not with other clinical or epidemiological variables. Ceftaroline MICs were consistently low among AmpS isolates, while ceftriaxone and cefotaxime showed greater variability. Low-MIC isolates were distributed across multiple clonal lineages and hospitals and did not share a distinctive resistance or virulence gene profile. PBP5 phylogeny and variation at the psr-pbp5 region separated AmpS from AmpR E. faecium but did not explain variability in ceftriaxone MICs. Five AmpS isolates with reduced ceftriaxone MICs carried chromosomal deletions that included the psr-pbp5 region and genes with diverse cellular functions. Variation in other candidate resistance genes (pbpA, ponA, pbpF, croRS, stpA/stk and murAA) did not consistently explain the MIC differences. These results reveal unexpected heterogeneity in intrinsic cephalosporin resistance in clinical E. faecium and E. lactis and suggest that additional genetic or regulatory mechanisms underlie reduced susceptibility.

microbiology↗

bioRxiv2024

Analysis of high-molecular-weight proteins using MALDI-TOF MS and Machine Learning for the differentiation of clinically relevant Clostridioides difficile ribotypes

Clostridioides difficile is the main cause of antibiotic related diarrhea and some ribotypes (RT), such as RT027, RT181 or RT078, are considered high risk clones. A fast and reliable approach for C. difficile ribotyping is needed for a correct clinical approach. This study analyses high-molecular-weight proteins for C. difficile ribotyping with MALDI-TOF MS. Sixty-nine isolates representative of the most common ribotypes in Europe were analyzed in the 17,000-65,000 m/z region and classified into 4 categories (RT027, RT181, RT078 and Other RTs). Five supervised Machine Learning algorithms were tested for this purpose: K-Nearest Neighbors, Support Vector Machine, Partial Least Squares-Discriminant Analysis, Random Forest and Light-Gradient Boosting Machine. All algorithms yielded cross-validation results >70%, being RF and Light-GBM the best performing, with 88% of agreement. Area under the ROC curve of these two algorithms was >0.9. RT078 was correctly classified with 100% accuracy and isolates from the RT181 category could not be differentiated from RT027.

microbiology↗

bioRxiv2021

Evaluation of the rapidBACpro(R) II kit for the rapid identification of microorganisms directly from blood cultures using MALDI-TOF MS

ObjectivesIdentification of microorganisms directly from blood cultures (BCs) using MALDI-TOF MS has shown to be the application with most impact in this methodology. In this study, a novel commercial method, the rapidBACpro(R) II, was evaluated in four clinical microbiology laboratories. MethodsPositive blood culture samples (n=801) were processed using the rapidBACpro(R) II kit and then compared with routine gold standard. A subset of monomicrobial BCs (n=560) were analyzed in parallel with the Sepsityper(R) kit (Bruker Daltonics, Bremen, Germany) and compared with the rapidBACpro(R) II kit. In addition, the rapidBACpro(R) II kit was also compared with two different in-house methods. ResultsOverall, 80.0% of the monomicrobial isolates (609/761) were correctly identified by the rapidBACpro(R) II kit at the species level (92.3% of the Gram negative and 72.4% of the Gram positive bacteria). The comparison with the Sepsityper(R) kit yielded higher rates of correct species-level identification provided by the rapidBACpro(R) II kit for all categories (p>0.0001) except for yeasts identified with score values >1.7. It also proved superior to the ammonium chloride method (p>0.0001) but the differential centrifugation method allowed higher rates of correct identification for Gram negative bacteria (p>0.1). ConclusionsThe rapidBACpro(R) II kit allowed a high rate of microorganisms correctly identified. The percentage of accurate species-level identification of Gram positive bacteria was particularly noteworthy in comparison with other commercial and in-house methods. This fact was especially interesting in the case of Staphylococcus sp. and Streptococcus sp. in order to elucidate their clinical impact, for example in device-associated bacteremia.

microbiology↗

bioRxiv2019

In vitro and in vivo efficacy of the combination of colistin and endolysins against clinical strains of Multi-Drug Resistant (MDR) pathogens

The multidrug resistance (MDR) among pathogenic bacteria is jeopardizing the worth of antimicrobials, which had previously changed medical sciences. In this study, we used bioinformatic tools to identify the endolysins ElyA1 and ElyA2 (GH108-PG3 family) present in the genome of bacteriophages Ab1051{Phi} and Ab1052{Phi}, respectively. The muralytic activity of these endolysins over MDR clinical isolates (Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae) was tested using the turbidity reduction assay. The minimal inhibitory concentrations (MICs) of endolysin, colistin and their combination were determined using the microdilution checkerboard method. The antimicrobial activity of the combinations was confirmed by time kill curves and in vivo assays in larvae of Galleria mellonella. Our results showed that ElyA1 displayed activity against all 25 strains of A. baumannii and P. aeruginosa tested and against 13 out of 17 strains of K. pneumoniae. No activity was detected when assays were done with endolysin ElyA2. The combined antimicrobial activity of colistin and endolysin ElyA1 yielded a reduction in the colistin MIC for all strains studied, except K. pneumoniae. These results were confirmed in vivo in G. mellonella survival assays. In conclusion, the combination of colistin with new endolysins such as ElyA1 could increase the bactericidal activity and reduce the MIC of the antibiotic, thus also reducing the associated toxicity.\n\nIMPORTANCEThe development of multiresistance by pathogen bacteria increases the necessity of the development of new antimicrobial strategies. In this work, we combined the effect of the colistin with a new endolysin, ElyA1, from a bacteriophage present in the clinical strain of Acinetobacter baumannii Ab105. ElyA1 is a lysozyme-like family (GH108-GP3), whose antimicrobial activity was described for first time in this work. Also, another endolysin, ElyA2, with the same origin and family, was characterized but in this case no activity was detected. ElyA1 presented lytic activity over a broad spectrum of strains from A. baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae. When colistin was combined with ElyA1 an increase of the antimicrobial activity was observed with a reduced concentration of colistin, and this observation was also confirmed in vivo in Galleria mellonella larvae. The combination of colistin with new endolysins as ElyA1 could increase the bactericidal activity and lowering the MIC of the antibiotic, thus also reducing the associated toxicity.

microbiology↗

bioRxiv2019

Implication of HisF from Acinetobacter baumannii in persistence during a pneumonia infection

The hisF gene from A. baumannii ATCC 17978 was found over-expressed during a murine pneumonia infection. A mutant strain lacking hisF showed its involvement in virulence during mice pneumonia as well as in host inflammatory response, where the product of HisF may act as negative regulator in the production of pro-inflammatory cytokines. This work evaluates the role of HisF in the A. baumannii pathogenesis and suggests its potential as a new target for antimicrobial therapies.

microbiology↗