Javier Aznar

Escherichia coli is the most frequent Gram-negative bacilli involved in intra-abdominal infections. However, despite high mortality rates associated with biliary tract infections due to E. coli, there is no study focusing on this pathogen. In this study, we have characterized a group of 15 E. coli isolates obtained from 12 patients with biliary tract infections. Demographic and clinical data of the patients were recovered. Phylogeny, resistome, and virulome analysis through whole genome sequencing and biofilm formation were investigated. Among the 15 E. coli isolates, no predominant sequence type (ST) was identified, although 3 of them belonged to unknown STs (20%). Resistance to ampicillin, amoxicillin/clavulanic acid, cotrimoxazole, and quinolones was more present in these isolates; whereas, third and fourth generation cephalosporins, carbapenems, amikacin, tigecycline, and colistin were highly active. Moreover, high diversity of virulence factors has been found, with sfa, fimH, and gad the most frequently detected genes. Interestingly, 26.6% of the E. coli isolates were high biofilm-producers. Altogether, our data characterized for the first time E. coli isolates associated with biliary tract infections in terms of genomic relationship, resistome, and virulome.

The appearance and dissemination of MDR among pathogenic bacteria has forced the search for new antimicrobials. Bacteriocins have been proposed as potential alternatives for the treatment of infections due to multiresistant strains. To analyse the activity of R-pyocins against clinical isolates of Pseudomonas aeruginosa from patients with cystic fibrosis and other sources and evaluate them as a potential adjuvant or alternative to the current antibiotic treatment. The activity of R-pyocins against 150 strains of P. aeruginosa isolated from patients with cystic fibrosis or bacteraemia was studied through spot assay. Interactions between R-pyocins and antipseudomonal agents were quantitatively studied by the chequerboard method. The proportion of P. aeruginosa isolates susceptible to R-pyocins was found to be higher in cystic fibrosis isolates compared with bacteraemia isolates (79.41% versus 50%). Moreover, no interactions were found between common antipseudomonal agents and R-pyocin susceptibility, except for the ST175 high-risk clone. Our results highlight the possibility of using R-pyocins as therapeutic agents, alone or as adjuvants, against P. aeruginosa in cystic fibrosis.

We present the case of a 6-year-old boy diagnosed with stage III mediastinal Non Hodgkin Lymphoblastic T cell Lymphoma who suffered from catheter-related bloodstream infection (CRBI) due to Mycobacterium fortuitum whilst receiving chemotherapy. Isolation of this rare pathogen was done directly from blood culture and identification was made rapidly within 48 h using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectro­metry as well as specific polymerase chain reaction (PCR)-reverse hybridization method. This allowed prompt directed antibiotic therapy apart from central venous catheter removal and resulted in an excellent clinical response. This case highlights the potential benefit of using MALDI-TOF mass spectrometry, a fast, cost-effective and precise methodology, in the diagnosis and subsequent management of invasive bacterial infection. Wir präsentieren einen 6 Jahre alten Jungen mit lymphoblastischem Non-Hodgkin-T-Zell-Lymphom, der an einer durch Mycobacterium fortuitum verursachten Zentralvenenkatheter(ZVK)-Infektion erkrankte. Die Isolierung dieses seltenen Mikroorganismus erfolgte direkt aus der Blutkulturflasche. Die korrekte Identifizierung gelang innerhalb von 48 h mittels Matrix-assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) Mass Spectro­metry und wurde durch die para­llel durchgeführte spezifische Polymerase-Chain-Reaction(PCR)-re­verse Hybridisationsmethode bestätigt. Dieses Vorgehen ermöglichte eine schnelle und organismusgezielte Antibio­tikatherapie und resultierte zusammen mit der prompten Entfernung des ZVK zu einem exzellenten klinischen Erfolg. Der hier präsentierte Fall verdeutlicht die Relevanz der MALDI-TOF Mass Spectrometry als schnelle, kostengünstige und präzise Diagnostikmethode in der Identifizierung und Behandlung schwerer bakterieller Infekte. ^* These two authors are shared 1st author/contributed equally.

To model the standard broth microdilution method, based on a modified Gompertz function, to obtain accurate vancomycin MIC values for methicillin-resistant Staphylococcus aureus (MRSA). The effect of these MIC values on the vancomycin therapeutic target of AUC_0–24/MIC ≥400 was evaluated. Three clinical isolates of MRSA with different vancomycin MIC values were used in this model. The optical densities (OD) of each MIC determination were modelled by a non-linear regression method using an F-test. The OD data were adjusted to the Gompertz equation to obtain the MIC values. The mean vancomycin AUC_0–24 obtained with a 30 mg/kg/day dosing schedule was calculated using a Monte Carlo simulation over 5000 subjects, using the pharmacokinetic data obtained in vancomycin-treated patients in our hospital. Although the MIC values obtained with this model were lower than those of the diffusion method (Etest) in all three cases, this did not affect the AUC_0–24/MIC ratio for the strains with MICs of 1 mg/L by Etest. However, in those strains with MIC values >1 mg/L, the confidence intervals obtained for this ratio included values <400. The inherent variability of the broth microdilution method could explain the differences in the clinical outcome in MRSA-infected patients treated with vancomycin, mainly in those due to strains with MIC values of 1.5–2 mg/L by Etest, because the corresponding MIC values would range from 0.84 to 1.52 mg/L by the microdilution method, which could affect the therapeutic target.