Pseudomonas aeruginosa is a major opportunistic human pathogen, responsible for nosocomial infections and infections in patients with impaired immune systems. Little data exist about the faecal colonisation by P. aeruginosa isolates in healthy humans. The occurrence, antimicrobial resistance phenotype, virulence genotype, and genetic lineages of P. aeruginosa from faecal samples of children from two different Spanish regions were characterised. Seventy-two P. aeruginosa were isolated from 1,443 faecal samples. Low antimicrobial resistance levels were detected: ceftazidime (8%), cefepime (7%), aztreonam (7%), gentamicin (3%), ciprofloxacin (1%), and imipenem (1%); susceptibility to meropenem, amikacin, tobramycin, levofloxacin, and colistin. Four multidrug-resistant strains were found. Important differences were detected between both geographical regions. Forty-one sequence types were detected among the 48 tested strains. Virulence and quorum sensing genes were analysed and 13 virulotypes were detected, being 26 exoU-positive strains. Alteration in protein OprD showed eight different patterns. The unique imipenem-resistant strain showed a premature stop codon in OprD. Intestinal colonisation by P. aeruginosa, mainly by international clones (as ST244, ST253, and ST274), is an important factor for the systemic infections development and the environmental dissemination. Periodic active surveillance is useful to identify these community human reservoirs and to control the evolution of antibiotic resistance and virulence activity.

This study aimed at determining the mechanisms of linezolid resistance and the molecular characteristics of clinical Staphylococcus aureus ( n = 2) and coagulase-negative staphylococci ( n = 15) isolates obtained from four Spanish hospitals. The detection of linezolid resistance mechanisms (mutations and acquisition of resistance genes) was performed by PCR/sequencing. The antimicrobial resistance and virulence profile was determined, and the isolates were typed by different molecular techniques. Moreover, the genetic environment of the cfr gene was determined by whole-genome sequencing. The cfr gene was detected in one methicillin-resistant S. aureus (MRSA) that also displayed the amino acid change Val118Ala in the ribosomal protein L4. The second S. aureus isolate was methicillin susceptible and showed different alterations in the ribosomal protein L4. All remaining linezolid-resistant Staphylococcus epidermidis ( n = 14) and Staphylococcus hominis isolates ( n = 1) showed the mutation G2576T ( n = 14) or C2534T ( n = 1) in the 23S rRNA. Moreover, different amino acid changes were detected in the ribosomal proteins L3 and L4 in S. epidermidis isolates. All S. epidermidis isolates belonged to the multilocus sequence type ST2. Linezolid-resistant staphylococci (LRS) showed a multiresistance phenotype, including methicillin resistance that was detected in all isolates but one, and was mediated by the mecA gene. The cfr gene in the MRSA isolate was located together with the fexA gene on a conjugative 38,864 bp plasmid. Linezolid- and methicillin-resistant S. epidermidis ST2 showing mutations in the 23S rRNA and in the ribosomal proteins L3 and L4 are spread among Spanish hospitals, whereas LRS carrying acquired linezolid resistance genes are rarely detected.

Antimicrobial stewardship programs (ASPs) are a central component in reducing the overprescription of unnecessary antibiotics, with multiple studies showing benefits in the reduction of bacterial resistance. Less commonly, ASPs have been performed in outpatient settings, but there is a lack of available data in these settings. We implemented an ASP in a large regional outpatient setting to assess its feasibility and effectiveness. Over a 5-year post-implementation period, compared to the pre-intervention period, a significant reduction in antibiotic prescription occurred, with a reduction in resistance in E. coli urinary isolates. ASP activities also were found to be cost-effective, with a reduction in medication prescription.

Invasive meningococcal disease (IMD) is associated with significant global morbidity and mortality and is addressed by conjugated polysaccharide and subcapsular vaccines. In Spain, data on 4CMenB vaccine strain coverage and antimicrobial susceptibility are limited. This study aimed to describe the genomic epidemiology, predict 4CMenB vaccine strain coverage, and assess antimicrobial susceptibility of 323 Neisseria meningitidis isolates causing IMD, collected from 57 Clinical Microbiology Laboratories in Spain over 12 years (2011/12-2022/23). Whole genome sequencing was performed to identify serogroup, clonal complex (cc), and antimicrobial resistance determinants. Vaccine strain coverage for serogroup B (MenB) isolates was predicted using the genetic Meningococcal Antigen Typing System approach. The most prevalent serogroups were B (57.9%), W (21.4%), C (10.4%), and Y (8.4%). MenB predominated throughout most seasons, except during the 2019/20 season when serogroup W peaked. Post-COVID-19 pandemic, MenB remained the most frequent (70.2%). Thirteen cc were identified among MenB isolates, with cc213 being the most prevalent (40.1%). Only 28.9% of MenB isolates were predicted to be covered by 4CMenB, with cc213 showing an exceptionally low coverage rate (5.3%) due to antigenic variants poorly targeted by the vaccine. Notably, cc213 was responsible for twice the proportion of MenB cases in 4CMenB-vaccinated versus unvaccinated. All isolates were susceptible to third generation cephalosporins, and 13.5% showed penicillin resistance. This study highlights the alarming prevalence of cc213 among MenB IMD cases in Spain and the limited 4CMenB coverage against this cc. The disproportionate representation of cc213 in vaccinated individuals underscores its potential to compromise vaccine effectiveness.