Clinical Microbiology and Infectious Diseases Department, Gregorio Marañón Hospital Fundación para la Investigación Biomédica del Hospital Gregorio Marañón
Microbiology (medical), Orthopedics and Sports Medicine, Microbiology, Infectious Diseases
129
Scopus Publications
Scopus Publications
Clinical Efficacy and Safety of Multiple High-Dose Antibiotic-Loaded Cement Spacers in the Two-Stage Revision of Gram-Positive Periprosthetic Joint Infection Miguel Márquez-Gómez, Lourdes Prats-Peinado, José Antonio Matas Díaz, Mar Sánchez-Somolinos, María Guembe, et al. Microorganisms, 2026 Periprosthetic joint infection (PJI) is a devastating complication after total joint arthroplasty, typically managed through a two-stage revision protocol involving antibiotic-loaded spacers. This study aimed to evaluate the clinical outcomes and safety of a new multiple high-dose antibiotic-loaded cement (MHDALC) spacer against alternative classical antibiotic combinations for Gram-positive PJI. In this retrospective observational study of 102 patients (30 MHDALC vs. 72 control), the MHDALC cohort received spacers prepared with commercial cement (1 g clindamycin and 1 g gentamicin per 40 g) supplemented with manual additions of 4 g vancomycin and 2 g ceftazidime per 40 g of cement, while the control group received the same commercial cement supplemented with 4 g of vancomycin alone. Treatment failure was significantly lower in the MHDALC group (6.6%) compared to the control group (20.8%; p = 0.005). Furthermore, the time to second-stage reimplantation was drastically reduced in the MHDALC cohort (9.1 vs. 17.8 weeks; p = 0.001). Despite the substantially higher antibiotic load, no significant differences were observed regarding mechanical or surgical complications between the two groups (p = 1.00). In conclusion, the use of MHDALC spacers is an effective and safe strategy for treating Gram-positive PJI, significantly improving eradication rates and accelerating the transition to definitive reconstruction without compromising structural integrity.
Quantification and Comparison of Different Biofilm Components from Methicillin-Susceptible Staphylococcus aureus Treated with Tranexamic Acid Using an In Vitro Model Marta Díaz-Navarro, Antonio Benjumea, Andrés Visedo, Patricia Muñoz, Javier Vaquero, et al. Microorganisms, 2025 As we previously demonstrated that tranexamic acid (TXA), an antifibrinolytic, showed an antibacterial effect alone and in combination with vancomycin and gentamicin, we now wanted to analyze its own efficacy using new, different fluorescent staining reagents that target different components of the biofilm matrix and compare which one quantifies biofilm reduction better. A 108 cfu/mL suspension of the Staphylococcus aureus (ATCC29213) strain was placed into the wells of a 24-multiwell plate covered with glass slides coated with 10% poly-L-lysine under agitation for 24 h at 37 °C. After 3 washes with PBS, wells were treated with either TXA 10 mg/mL or sterile water and incubated for 24 h at 37 °C. After three washes with PBS, the density area of the following biofilm components was calculated using confocal laser scanning microscopy: extracellular proteins (Sypro Ruby), α-extracellular polysaccharides (ConA-Alexa fluor 633), α or β-extracellular polysaccharides (GS-II-Alexa fluor 488), bacterial DNA (PI), and eDNA (TOTO®-1). We observed a statistically significant reduction in the occupied area by all components of the S. aureus biofilm (p < 0.001) after TXA 10 mg/mL treatment, compared to the positive control. All biofilm components’ reduction percentages reached ≥90.0%. We demonstrated that TXA reduced both bacteria and extracellular matrix components of S. aureus biofilm by using five different stain reagents, with all being equally valid for quantification.
Assessment of the Anti-Biofilm Effect of Cefiderocol Against 28 Clinical Strains of Multidrug-Resistant Gram-Negative Bacilli Marta Díaz-Navarro, Emilia Cercenado, Andrés Visedo, Mercedes Marín, Marina Machado, et al. Antibiotics, 2025 Objectives: Cefideroccol (FDC) is a siderophore cephalosporin with potent antibacterial activity against a wide range of Gram-negative multidrug-resistant (MDR) microorganisms. We investigated the anti-biofilm capacity of FDC against clinical strains. Methods: This multicenter study was conducted on 28 selected strains of MDR Gram-negative bacilli isolated from clinical samples of Pseudomonas aeruginosa (n = 5), Acinetobacter baumannii (n = 11), and Klebsiella pneumoniae (n = 12). We first determined the minimum inhibitory concentration (MIC) of each strain using the microdilution method. We also defined the minimum biofilm inhibitory concentration (MBIC) as a ≥50% reduction in tetrazolium salt (XTT) (as recommended in the 2017 Spanish Microbiology Protocols [SEIMC] for the microbiological diagnosis of infections related to the formation of biofilms). We also analyzed the reduction in the following biofilm variables after an 8 mg/mL FDC treatment: the CFU count, the cell viability, the biomass, the metabolic activity, and extracellular α or β polysaccharides. Results: The MIC50 and MBIC50 of FDC were 0.5 mg/L and 64 mg/L, respectively. We observed a mean (SD) fold increase in the susceptibility to FDC between planktonic and sessile cells for P. aeruginosa, A. baumannii, and K. pneumoniae of 9.60 (0.55), 6.27 (2.28), and 6.25 (2.80), respectively. When 8 mg/mL of FDC was tested, we observed that the best median (IQR) percentage reductions were obtained for cell viability and the extracellular matrix (73.1 [12.4–86.5] and 79.5 [37.3–95.5], respectively), particularly for P. aeruginosa. The lowest percentage reduction rates were those obtained for biomass. Conclusions: We demonstrated that the susceptibility to FDC was significantly reduced when strains were in a biofilm state. The best percentage reduction rates for all biofilm-defining variables were observed for P. aeruginosa. Our results need to be validated using a larger collection of clinical samples.
Surveillance of nasal Staphylococcus aureus in patients undergoing breast surgery Ma Jesús Pérez-Granda, Andrés Visedo, Martín Olivares, Álvaro García-Cañal, Marta Díaz-Navarro, et al. Microbiology Spectrum, 2025 Screening and decolonization programs have proven effective in reducing the frequency of Staphylococcus aureus infections, mainly in orthopedic and cardiac procedures. Despite being classified as clean, breast surgery is associated with infection. Using culture and polymerase chain reaction (PCR) assay, we aimed to assess the frequency of nasal carriage of S. aureus in patients undergoing breast surgery. We conducted a prospective observational 10-month study at a large tertiary teaching hospital, including patients undergoing breast reconstruction surgery who met the eligibility criteria and signed the informed consent document. Nasal swabs were collected before surgery from patients with no signs of S. aureus infection and tested using both culture and the Xpert MRSA/SA SSTI PCR assay. The outcomes were nasal colonization by S. aureus , colonization rates at the time of surgery, infection, and length of hospital stay. We included 100 patients, 27% of whom were colonized. Of these, 20 patients were positive by culture and 27 by PCR. The median (IQR) age was 56.0 (49.0–63.7) years. A total of 6 patients had infection, and the median (IQR) number of days until onset of infection was 191 (186.25–197.00). Carriage of S. aureus before surgery was microbiologically confirmed in two patients. We demonstrated that 27% of patients undergoing breast surgery were nasal carriers of S. aureus , with PCR assay being the best diagnostic strategy. Future studies are needed to address the efficacy of bacterial decolonization of the nose and nipples to reduce the frequency of infection and complications. IMPORTANCE We showed that almost 30% of women undergoing breast surgery are nasal carriers of S. aureus , and PCR molecular technique was the best diagnostic tool. However, future studies are needed to implement decolonization of nasal and nipple to reduce infection and complications.
Is It Possible to Optimize the Elaboration and Preservation of a Vancomycin Catheter Lock Solution? Marta Díaz-Navarro, David Samitier, Félix García-Moreno, María Sanjurjo, Patricia Muñoz, et al. Antibiotics, 2025 Background/Objectives: Vancomycin (V) is widely used for catheter lock therapy. However, its ad hoc preparation in pharmacy departments involves discarding most of an intravenous vial and contributes to high workload. We aimed to assess the V concentration and minimum inhibitory biofilm concentration (MIBC) of a frozen V lock solution. Methods: Two V-2 mg/mL solutions were tested: (1) V + heparin 100 IU/mL and (2) V + citrate 2%. Solutions were frozen at −20 °C, followed by 48 h refrigeration, and analyses were performed at baseline and after 2, 4, 8, and 12 weeks (experiment 1). In addition, after the 12-week freezing period, solution 1 was also preserved for 1 and 2 weeks at both 4 °C and room temperature (experiment 2). V concentration was assessed by HPLC-DAD at 205 nm and validated with forced degradation tests. A <10% variation indicated significant change. MBIC was determined by XTT staining of 24 h biofilms exposed to decreasing concentrations of each solution. Microorganisms tested included methicillin-susceptible and -resistant Staphylococcus aureus (MSSA, MRSA), Staphylococcus epidermidis ATCC35984 (SE), and a highly biofilm-forming clinical S. epidermidis strain (SEclin). MIBC was defined as ≥50% reduction in metabolic activity. Results: In experiment 1, while V concentration remained stable over time, MIBC values varied, notably increasing from 8 weeks for all strains. Moreover, in experiment 2, significant reductions in both V concentration and MIBC were detected in the 2-week period. Conclusions: V lock solution appears to be able to be 12-weeks frozen followed by up to 1 week at refrigeration or room temperature. This facilitates the optimization of vial preparation in hospital pharmacy laboratories.
Reliability of differential time to positivity technique for diagnosing catheter-related bloodstream infections: a retrospective analysis Álvaro Irigoyen-von-Sierakowski, Marta Díaz-Navarro, Andrés Visedo, María Jesús Pérez-Granda, Pablo Martín-Rabadán, et al. Microbiology Spectrum, 2025 The differential time to positivity (DTTP) technique is the recommended conservative procedure to diagnose catheter-related bloodstream infection (C-RBSI). However, its reliability and accuracy remain under debate. Therefore, we aimed to compare the DTTP technique feasibility to detect C-RBSI compared to the catheter culture (CC) method. We conducted a 9-month retrospective study including bacteremic episodes in which both DTTP blood cultures (BC) and CC were obtained. We analyzed the diagnostic validity of the DTTP technique for detecting C-RBSI compared to the gold standard (C-RBSI with CC), along with patient clinical data. We included 37 episodes of C-RBSI where both DTTP BC and CC were obtained. C-RBSI was confirmed by both techniques in only 13 episodes (35.1%), whereas in 11 (29.7%) and 13 (35.1%), only DTTP BC or DTTP BC with CC (with a difference between catheter lumen and peripheral BC growth of <2 hours) was positive, respectively. Therefore, the validity values of the DTTP technique for predicting C-RBSI were as follows: sensitivity, 50.0%; specificity, 71.8%; positive predictive value, 54.2%; and negative predictive value, 68.3%. The distribution of microorganisms was similar among the three groups. All patients in whom colonization was not demonstrated by CC ( n = 11) had been receiving antibiotics before catheter withdrawal. DTTP is a conservative technique that might help to diagnose C-RBSI mostly in situations where catheter removal cannot be achieved. However, it should be interpreted with caution and never be used to rule out C-RBSI. CC before starting antimicrobial therapy remains the most reliable method to diagnose and confirm an episode of C-RBSI. IMPORTANCE We try to clarify the reliability of the differential time to positivity technique to predict C-RBSI. It may be interpreted with caution and considering clinical signs, as some C-RBSI can be misdiagnosed.
Virulence profile of carbapenem-resistant Klebsiella pneumoniae strains by an in vivo model of Galleria mellonella María Guembe, Rama Hafian, Marta Díaz-Navarro, Andrés Visedo, Flavio De Maio, et al. Microbiology Spectrum, 2025 Klebsiella pneumoniae is a significant healthcare-associated pathogen, notable for its diverse virulence and antibiotic resistance profiles. This study aimed to characterize the genotypic and phenotypic diversity of K. pneumoniae isolates and evaluate their virulence using the Galleria mellonella model. Biomass production, metabolic activity, capsule formation, and siderophore production were assessed in 27 K . pneumoniae isolates from hospital-associated infections. Lethality curves were generated using the G. mellonella model, with survival monitored hourly from 16 to 48 hours. The most common sequence types (ST) identified were the high-risk clones ST307 ( N = 10), ST512 ( N = 8), ST101 ( N = 7), and ST661 ( N = 2). These STs were associated with distinct K-locus, including KL102, KL107, KL17, and KL39. Most isolates belonged to the O2afg locus ( N = 18), with the K. pneumoniae carbapenemase genotype detected in 96.3% of strains. None of the isolates were classified as hypervirulent. Phenotypically, ST661 exhibited the highest biomass production despite showing similar metabolic activity to other STs. A positive correlation was observed between biomass and siderophore production, while capsule production was inversely correlated with biomass. In the G. mellonella model, ST661 demonstrated the highest virulence, resulting in 100% mortality by 48 hours, compared to survival rates of 21.4% for ST101, 38.0% for ST307, and 31.2% for ST512. These findings underscore the pathogenic potential of ST661 isolates with enhanced biofilm production. The G. mellonella model may serve as an effective in vivo system for evaluating the virulence of emerging K. pneumoniae lineages. IMPORTANCE We demonstrate that the Galleria mellonella model is a useful tool to analyze the virulence of carbapenem-resistant Klebsiella pneumoniae strains. Our findings highlight the pathogenicity of carbapenem-resistant K pneumoniae isolates, particularly the role of the ST661 that, despite being a rare lineage, harbors the blaVIM gene and is associated with high biofilm production and the highest mortality rates.
2016 Expert consensus document on prevention, diagnosis and treatment of short-term peripheral venous catheter-related infections in adult Revista Espanola De Quimioterapia Publicacion Oficial De La Sociedad Espanola De Quimioterapia, 2016
Evolution of antimicrobial susceptibility patterns of aerobic and facultative gram-negative bacilli causing intra-abdominal infections: Results from the SMART studies 2003-2007 Revista Espanola De Quimioterapia, 2008