C-terminal deletion of RelA protein is suggested as a possible cause of infective endocarditis recurrence with Enterococcus faecium.

Infective endocarditis (IE) caused by Enterococcus spp. represents the third most common cause of IE, with high rates of relapse compared with other bacteria. Interestingly, late relapses (>6 months) have only been described in Enterococcus faecalis, but here we describe the first reported IE relapse with Enterococcus faecium more than a year (17 months) after the initial endocarditis episode. Firstly, by multi locus sequence typing (MLST), we demonstrated that both isolates (EF646 and EF641) belong to the same sequence type (ST117). Considering that EF641 was able to overcome starvation and antibiotic treatment conditions surviving for a long period of time, we performed bioinformatic analysis in identifying potential genes involved in virulence and stringent response. Our results showed a 13-nucleotide duplication (positions 1638-1650) in the gene relA, resulting in a premature stop codon, with a loss of 167 amino acids from the C-terminal domains of the RelA enzyme. RelA mediates the stringent response in bacteria, modulating levels of the alarmone guanosine tetraphosphate (ppGpp). The relA mutant (EF641) was associated with lower growth capacity, the presence of small colony variants, and higher capacity to produce biofilms (compared with the strain EF646), but without differences in antimicrobial susceptibility patterns according to standard procedures during planktonic growth. Instead, EF641 demonstrated tolerance to high doses of teicoplanin when growing in a biofilm. We conclude that all these events would be closely related to the long-term survival of the E. faecium and the late relapse of the IE. These data represent the first clinical evidence of mutations in the stringent response (relA gene) related with E. faecium IE relapse.

Efficacy and safety of an early oral switch in low-risk Staphylococcus aureus bloodstream infection (SABATO): an international, open-label, parallel-group, randomised, controlled, non-inferiority trial.

BACKGROUND: Staphylococcus aureus bloodstream infection is treated with at least 14 days of intravenous antimicrobials. We assessed the efficacy and safety of an early switch to oral therapy in patients at low risk for complications related to S aureus bloodstream infection. METHODS: In this international, open-label, randomised, controlled, non-inferiority trial done in 31 tertiary care hospitals in Germany, France, the Netherlands, and Spain, adult patients with low-risk S aureus bloodstream infection were randomly assigned after 5-7 days of intravenous antimicrobial therapy to oral antimicrobial therapy or to continue intravenous standard therapy. Randomisation was done via a central web-based system, using permuted blocks of varying length, and stratified by study centre. The main exclusion criteria were signs and symptoms of complicated S aureus bloodstream infection, non-removable foreign devices, and severe comorbidity. The composite primary endpoint was the occurrence of any complication related to S aureus bloodstream infection (relapsing S aureus bloodstream infection, deep-seated infection, and mortality attributable to infection) within 90 days, assessed in the intention-to-treat population by clinical assessors who were masked to treatment assignment. Adverse events were assessed in all participants who received at least one dose of study medication (safety population). Due to slow recruitment, the scientific advisory committee decided on Jan 15, 2018, to stop the trial after 215 participants were randomly assigned (planned sample size was 430 participants) and to convert the planned interim analysis into the final analysis. The decision was taken without knowledge of outcome data, at a time when 126 participants were enrolled. The new sample size accommodated a non-inferiority margin of 10%; to claim non-inferiority, the upper bound of the 95% CI for the treatment difference (stratified by centre) had to be below 10 percentage points. The trial is closed to recruitment and is registered with ClinicalTrials.gov (NCT01792804), the German Clinical trials register (DRKS00004741), and EudraCT (2013-000577-77). FINDINGS: Of 5063 patients with S aureus bloodstream infection assessed for eligibility, 213 were randomly assigned to switch to oral therapy (n=108) or to continue intravenous therapy (n=105). Mean age was 63·5 (SD 17·2) years and 148 (69%) participants were male and 65 (31%) were female. In the oral switch group, 14 (13%) participants met the primary endpoint versus 13 (12%) in the intravenous group, with a treatment difference of 0·7 percentage points (95% CI -7·8 to 9·1; p=0·013). In the oral switch group, 36 (34%) of 107 participants in the safety population had at least one serious adverse event compared with 27 (26%) of 103 participants in the intravenous group (p=0·29). INTERPRETATION: Oral switch antimicrobial therapy was non-inferior to intravenous standard therapy in participants with low-risk S aureus bloodstream infection. However, it is necessary to carefully assess patients for signs and symptoms of complicated S aureus bloodstream infection at the time of presentation and thereafter before considering early oral switch therapy. FUNDING: Deutsche Forschungsgemeinschaft. TRANSLATIONS: For the German, Spanish, French and Dutch translations of the abstract see Supplementary Materials section.

Long-term outcomes of an educational paediatric antimicrobial stewardship programme: a quality improvement study.

BACKGROUND AND OBJECTIVES: Antimicrobial stewardship programmes (ASPs) have resulted in antimicrobial consumption (AMC) reduction and quality of prescription (QOP) improvement. However, evidence of ASP impact in paediatrics is still limited. This study aims to assess a paediatric ASP long-term outcomes. METHODS: A quality improvement study assessed by a interrupted time series analysis was conducted in a paediatric tertiary hospital. QOP expressed as proportion of adequate prescriptions, AMC measured by defined daily dose incidence per 1000 occupied bed days, incidence density of bloodstream infections (BSIs) and its related all-cause crude death rate (CDR) were compared between pre (from January 2013 to December 2015) and post (from January 2016 to December 2019) ASP activities intensification, which included a dedicated paediatric infectious diseases physician to actively perform educational interviews with prescribers. RESULTS: Inappropriate prescribing showed a significant downward shift associated to the intervention with a -51.4% (-61.2% to -41.8%) reduction with respect to the expected values. Overall AMC showed no trend change after the intervention. For neonatology a28.8% (-36.8% to -20.9%) reduction was observed. Overall anti-pseudomonal cephalosporin use showed a -51.2% (-57.0% to -45.4%) reduction. Decreasing trends were observed for carbapenem use, with a quarterly per cent change (QPC) of -2.4% (-4.3% to -0.4%) and BSI-related CDR (QPC=-3.6%; -5.4% to -1.7%) through the study period. Healthcare-associated multi-drug-resistant BSI remained stable (QPC=2.1; -0.6 to 4.9). CONCLUSIONS: Intensification of counselling educational activities within an ASP suggests to improve QOP and to partially reduce AMC in paediatric patients. The decreasing trends in mortality remained unchanged.

Implementation of a PCR-based strategy to control an outbreak by Serratia marcescens in a Neonatal Intensive Care Unit.

OBJECTIVES: To evaluate the clinical and epidemiological impact of a new molecular surveillance strategy based on qPCR to control an outbreak by Serratia marcescens in a Neonatal Intensive Care Unit (NICU). METHODS: We design a specific qPCR for the detection of S. marcescens in rectal swabs of patients admitted to a NICU. We divided the surveillance study into two periods: (a) the pre-PCR, from the outbreak declaration to the qPCR introduction, and (b) the PCR period, from the introduction of the qPCR until the outbreak was solved. In all cases, S. marcescens isolates were recovered and their clonal relationship was analysed by PFGE. Control measures were implemented during the outbreak. Finally, the number of bloodstream infections (BSI) was investigated in order to evaluate the clinical impact of this molecular strategy. RESULTS: Nineteen patients colonized/infected by S. marcescens were detected in the pre-PCR period (October 2020-April 2021). On the contrary, after the PCR implementation, 16 new patients were detected. The PFGE revealed 24 different pulsotypes belonging to 7 different clonal groups, that were not overlapping at the same time. Regarding the clinical impact, 18 months after the qPCR implementation, no more outbreaks by S. marcescens have been declared in the NICU of our hospital, and only 1 episode of BSI has occurred, compared with 11 BSI episodes declared previously to the outbreak control. CONCLUSIONS: The implementation of this qPCR strategy has proved to be a useful tool to control the nosocomial spread of S. marcescens in the NICU.

BIChromET: A Chromogenic Culture Medium for Detection of Piperacillin/Tazobactam and Cefepime Resistance in Pseudomonas aeruginosa.

OBJECTIVES: The BIChromET selective medium for detecting piperacillin-tazobactam (TZP) and cefepime (FEP) resistant Pseudomonas aeruginosa was developed. METHODS: The performance of this medium was first evaluated using a collection of 100 P. aeruginosa clinical strains (70 TZP-susceptible, 30 TZP-resistant, 58 FEP-susceptible, and 42 FEP-resistant). Then, we performed clinical validation by testing 173 respiratory clinical samples. RESULTS: The BIChromET medium showed excellent sensitivity (TZP (avg. 96.7%); FEP (avg. 92.7%)) and specificity (TZP (avg. 98.9%); FEP (avg. 98%)) in distinguishing the detection limit ranging from 104 to 108 CFU/mL. Then, testing the bronchoalveolar lavage (BAL) and tracheobronchial aspirate (TBA) clinical specimens (N = 173) revealed the excellent performance of the medium with P. aeruginosa, showing 100% and 92.6% of categorical agreements with the results obtained via the broth microdilution methods (BMD) for TZP and FEP, respectively. CONCLUSION: This medium allows for easy and accurate detection of TZP/FEP-resistant isolates regardless of their resistance mechanisms.

Safety of early oral ambulatory treatment of adult patients with bloodstream infections discharged from the emergency department.

This study evaluates the safety of early oral ambulatory treatment of adult patients diagnosed with bacteremia after their discharge from the emergency department. A cohort of 206 febrile ambulatory patients was assessed. Bacteremic low-risk patients were recommended an oral treatment and were compared with matched febrile non-bacteremic outpatients. Rates of 14-day mortality and unplanned re-consultations were similar and below 5% in both cohorts, highlighting the safety of oral therapy of low-risk bacteremia, even from its onset.

[Translated article] Analysis of the appropriateness of antibiotic prophylaxis in surgical procedures in Spain. Protocol for the "ProA-Q" study.

Surgical antibiotic prophylaxis is one of the most useful measures to prevent surgical wound infection. OBJECTIVE: The aim of this project is to evaluate the appropriateness of the use of antibiotic prophylaxis in surgical procedures performed in Spanish hospitals, both globally and according to the type of surgery performed. METHOD: For this purpose, an observational, retrospective, cross-sectional, and multicentre study has been designed to collect all the variables that allow the evaluation of the appropriateness of surgical antibiotic prophylaxis by comparing the prescribed treatment, the recommendations included in the local guidelines, and the consensus document of the Spanish Society of Infectious Diseases and Clinical Microbiology and the Spanish Association of Surgeons. Indication, choice of antimicrobial, dose, route and duration of administration, timing, re-dosing, and duration of the prophylaxis will be taken into account. The sample will consist of patients who underwent scheduled or emergency surgery, either as inpatients or outpatients, in hospitals in Spain. A sample size of 2335 patients has been established to estimate, with 95% confidence and 80% power, a percentage of appropriateness that is expected to be around 70%. Differences between variables will be analysed using Student's t-test, Mann-Whitney U test, Chi-square test, or Fisher's test, as appropriate. The degree of agreement between the antibiotic prophylaxis recommended by the guidelines of the different hospitals and that recommended in the literature will be analysed by calculating the Cohen's kappa indicator. Binary logistic regression analysis using generalised linear mixed models will be performed to identify possible factors associated with differences in the appropriateness of antibiotic prophylaxis. DISCUSSION: The results of this clinical study will allow us to focus on specific surgical areas with higher rates of inappropriateness, identify key points of action and guide future strategies for antimicrobial stewardship programs in the area of antibiotic prophylaxis.

Análisis de la adecuación de la profilaxis antibiótica en procedimientos quirúrgicos en España. Protocolo del estudio ProA-Q / Analysis of the appropriateness of antibiotic prophylaxis in surgical procedures in Spain. Protocol for the "ProA-Q" study

La profilaxis antibiótica quirúrgica es una de las medidas más útiles para la prevención de la infección de la herida quirúrgica.Objetivoel objetivo de este proyecto es evaluar la adecuación del uso de profilaxis antibiótica en procedimientos quirúrgicos realizados en centros hospitalarios españoles, tanto de forma global como en función del tipo de cirugía realizada. Metodología para ello, se ha diseñado un estudio observacional, retrospectivo, transversal y multicéntrico, donde se recopilarán todas aquellas variables que permitan evaluar la adecuación de la profilaxis antibiótica quirúrgica mediante la comparación del tratamiento prescrito, las recomendaciones recogidas en las guías locales y el documento de consenso de la Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica y la Asociación Española de Cirujanos. Se tendrán en cuenta la indicación, elección del antimicrobiano, dosis, vía de administración y tiempo de infusión, momento de la administración de la primera dosis, redosificación y la duración de la profilaxis. La muestra estará constituida por pacientes que hayan sido intervenidos de forma programada o urgente, en régimen de hospitalización o ambulatorio, en centros hospitalarios de España. Se ha establecido un tamaño muestral de 2.335 pacientes para estimar con una confianza del 95% y una potencia del 80%, un porcentaje de adecuación que se espera esté en torno al 70%. Las diferencias entre las variables se analizarán mediante la prueba t-Student, U de Mann-Whitney, el test Chi2 o test de Fisher, según proceda. El grado de concordancia entre la profilaxis antibiótica recomendada por las guías de los distintos hospitales y la recomendada en la literatura se analizará mediante el cálculo del indicador Kappa de Cohen... (AU)

Surgical antibiotic prophylaxis is one of the most useful measures to prevent surgical wound infection. Objective The aim of this project is to evaluate the appropriateness of the use of antibiotic prophylaxis in surgical procedures performed in Spanish hospitals, both globally and according to the type of surgery performed. Method For this purpose, an observational, retrospective, cross-sectional and multicenter study has been designed to collect all the variables that allow the evaluation of the appropriateness of surgical antibiotic prophylaxis by comparing the prescribed treatment, the recommendations included in the local guidelines and the consensus document of the Spanish Society of Infectious Diseases and Clinical Microbiology and the Spanish Association of Surgeons. Indication, choice of antimicrobial, dose, route and duration of administration, timing, re-dosing and duration of the prophylaxis will be taken into account. The sample will consist of patients who underwent scheduled or emergency surgery, either as inpatients or outpatients, in hospitals in Spain. A sample size of 2,335 patients has been established to estimate, with 95% confidence and 80% power, a percentage of appropriateness that is expected to be around 70%. Differences between variables will be analyzed using Student's t-test, Mann-Whitney U test, Chi-square test, or Fisher's test, as appropriate. The degree of agreement between the antibiotic prophylaxis recommended by the guidelines of the different hospitals and that recommended in the literature will be analyzed by calculating the Cohen's kappa indicator. Binary logistic regression analysis using generalized linear mixed models will be performed to identify possible factors associated with differences in the appropriateness of antibiotic prophylaxis... (AU)

Role of blaTEM and OmpC in the piperacillin-tazobactam resistance evolution by E. coli in patients with complicated intra-abdominal infection.

Piperacillin-tazobactam resistance (P/T-R) is increasingly reported among Escherichia coli isolates. Although in vitro experiments have suggested that blaTEM gene plays a key role in the P/T-R acquisition, no clinical in vivo study has yet confirmed the role of blaTEM or other genes. Therefore, we aimed to identify the mechanisms underlying P/T-R by following up patients with E. coli complicated intra-abdominal infections (cIAI) who experienced P/T treatment failure. Four pairs of strains, clonally related from four patients, were isolated both before and after treatment with P/T dosed at 4 g/0.5 g intravenously. The P/T MIC was tested using broth microdilution, and ß-lactamase activity was determined in these isolates. Whole-genome sequencing (WGS) was performed to decipher the role of blaTEM and other genes associated with P/T-R. Changes in the outer membrane protein (OMP) profile were analyzed using SDS-PAGE, and blaTEM and ompC transcription levels were measured by RT-qPCR. In addition, in vitro competition fitness was performed between each pairs of strains (P/T-susceptible vs. P/T-resistant). We found a higher copy number of blaTEM gene in P/T-R isolates, generated by three different genetic events: (1) IS26-mediated duplication of the blaTEM gene, (2) generation of a small multicopy plasmid (ColE-like) carrying blaTEM, and (3) adaptive evolution via reduction of plasmid size, leading to a higher plasmid copy number. Moreover, two P/T-R strains showed reduced expression of OmpC. This study describes the mechanisms involved in the acquisition of P/T-R by E. coli in patients with cIAI. The understanding of P/T-R evolution is crucial for effectively treating infected patients and preventing the spread of resistant microorganisms.

Post-mortem findings in Spanish patients with COVID-19; a special focus on superinfections.

Introduction: Whole-body autopsies may be crucial to understand coronavirus disease 2019 (COVID-19) pathophysiology. We aimed to analyze pathological findings in a large series of full-body autopsies, with a special focus on superinfections. Methods: This was a prospective multicenter study that included 70 COVID-19 autopsies performed between April 2020 and February 2021. Epidemiological, clinical and pathological information was collected using a standardized case report form. Results: Median (IQR) age was 70 (range 63.75-74.25) years and 76% of cases were males. Most patients (90%,) had at least one comorbidity prior to COVID-19 diagnosis, with vascular risk factors being the most frequent. Infectious complications were developed by 65.71% of the patients during their follow-up. Mechanical ventilation was required in most patients (75.71%) and was mainly invasive. In multivariate analyses, length of hospital stay and invasive mechanical ventilation were significantly associated with infections (p = 0.036 and p = 0.013, respectively). Necropsy findings revealed diffuse alveolar damage in the lungs, left ventricular hypertrophy in the heart, liver steatosis and pre-infection arteriosclerosis in the heart and kidneys. Conclusion: Our study confirms the main necropsy histopathological findings attributed to COVID-19 in a large patient series, while underlining the importance of both comorbid conditions and superinfections in the pathology.

Lipid signatures of West Nile virus infection unveil alterations of sphingolipid metabolism providing novel biomarkers.

West Nile virus (WNV) is a neurotropic flavivirus transmitted by the bites of infected mosquitoes. Severe forms of West Nile disease (WND) can curse with meningitis, encephalitis or acute flaccid paralysis. A better understanding of the physiopathology associated with disease progression is mandatory to find biomarkers and effective therapies. In this scenario, blood derivatives (plasma and serum) constitute the more commonly used biofluids due to its ease of collection and high value for diagnostic purposes. Therefore, the potential impact of this virus in the circulating lipidome was addressed combining the analysis of samples from experimentally infected mice and naturally WND patients. Our results unveil dynamic alterations in the lipidome that define specific metabolic fingerprints of different infection stages. Concomitant with neuroinvasion in mice, the lipid landscape was dominated by a metabolic reprograming that resulted in significant elevations of circulating sphingolipids (ceramides, dihydroceramides, and dihydrosphingomyelins), phosphatidylethanolamines and triacylglycerols. Remarkably, patients suffering from WND also displayed an elevation of ceramides, dihydroceramides, lactosylceramides, and monoacylglycerols in their sera. The dysregulation of sphingolipid metabolism by WNV may provide new therapeutic opportunities and supports the potential of certain lipids as novel peripheral biomarkers of WND progression.

Analysis of the appropriateness of antibiotic prophylaxis in surgical procedures in Spain. Protocol for the "ProA-Q" study. / Análisis de la adecuación de la profilaxis antibiótica en procedimientos quirúrgicos en España. Protocolo del estudio ProA-Q.

Surgical antibiotic prophylaxis is one of the most useful measures to prevent surgical wound infection. OBJECTIVE: The aim of this project is to evaluate the appropriateness of the use of antibiotic prophylaxis in surgical procedures performed in Spanish hospitals, both globally and according to the type of surgery performed. METHOD: For this purpose, an observational, retrospective, cross-sectional and multicenter study has been designed to collect all the variables that allow the evaluation of the appropriateness of surgical antibiotic prophylaxis by comparing the prescribed treatment, the recommendations included in the local guidelines and the consensus document of the Spanish Society of Infectious Diseases and Clinical Microbiology and the Spanish Association of Surgeons. Indication, choice of antimicrobial, dose, route and duration of administration, timing, re-dosing and duration of the prophylaxis will be taken into account. The sample will consist of patients who underwent scheduled or emergency surgery, either as inpatients or outpatients, in hospitals in Spain. A sample size of 2,335 patients has been established to estimate, with 95% confidence and 80% power, a percentage of appropriateness that is expected to be around 70%. Differences between variables will be analyzed using Student's t-test, Mann-Whitney U test, Chi-square test, or Fisher's test, as appropriate. The degree of agreement between the antibiotic prophylaxis recommended by the guidelines of the different hospitals and that recommended in the literature will be analyzed by calculating the Cohen's kappa indicator. Binary logistic regression analysis using generalized linear mixed models will be performed to identify possible factors associated with differences in the appropriateness of antibiotic prophylaxis. DISCUSSION: The results of this clinical study will allow us to focus on specific surgical areas with higher rates of inappropriateness, identify key points of action and guide future strategies for antimicrobial stewardship programs in the area of antibiotic prophylaxis.

Application of new indicators to assess the quality of antimicrobial use in intensive care units.

This study explored the feasibility of a bundle of indicators aimed at assessing the quality of antimicrobial use in intensive care units (ICUs) through an observational prospective study spanning 12 quarters (January 2019-December 2021) in a 1290-bed teaching hospital in Spain. Members of the antimicrobial stewardship programme team selected the indicators to analyse the quality of antimicrobial use based on consumption data from a list proposed in a previous study. Antimicrobial use in the ICU was measured as defined daily dose (DDD) per 100 occupied bed-days. Trends and points of change were analysed with segmented regression. The intravenous macrolides/intravenous respiratory fluoroquinolones ratio in the ICU increased progressively, although not significantly, by 11.14% per quarter, likely related to prioritization of the use of macrolides in serious community-acquired pneumonia and the coronavirus disease 2019 pandemic. A remarkable upward trend of 2.5% per quarter was detected in the anti-methicillin-susceptible Staphylococcus aureus/anti-methicillin-resistant S. aureus agents ratio in the ICU, which could be explained by the low prevalence of methicillin-resistant S. aureus at the study centre. Patterns of amoxicillin-clavulanic acid/piperacillin-tazobactam ratio and diversification of anti-pseudomonal beta-lactams showed an increment in use over the study. The use of these novel indicators provides additional information for the current analysis of DDD. Implementation is feasible, and led to the detection of patterns that agree with local guidelines and cumulative antibiogram reports, and foster targeted improvement actions within antimicrobial stewardship programmes.

Evaluation of the MDR Direct Flow Chip Kit for the Detection of Multiple Antimicrobial Resistance Determinants.

The objective of this study was to evaluate the accuracy of the MDR Direct Flow Chip Kit for the detection of antimicrobial resistance (AMR) determinants from bacterial colonies. Ninety-two clinical isolates with known AMR determinants genotypically characterized were used. The MDR Direct Flow Chip Kit is a microarray-based assay that included 55 AMR determinants for beta-lactams (23), quinolones (13), aminoglycosides (5), macrolides (5), sulfonamides (3), colistin (2), vancomycin (2), chloramphenicol (1), and linezolid (1). The MDR Direct Flow Chip Kit correctly detects 52 of 53 AMR determinants tested. The cfr gene (linezolid resistance) was not detected. The global sensibility, specificity, positive predictive value, and the negative predictive value calculated were 98%, 100%, 100%, and 97%. The Cohen's Kappa coefficient calculated was 0.97 [95% Confidence Interval (0.90-1.03)]. In conclusion, the MDR Direct Flow Chip is an accurate assay for the detection of multiple AMR determinants in one simple reaction.

High-level delafloxacin resistance through the combination of two different mechanisms in Staphylococcus aureus.

Delafloxacin is a new fluoroquinolone indicated for the treatment of complicated bacterial skin infections caused by Staphylococcus aureus. Despite its recent approval by the US Food and Drug Administration, the emergence of S. aureus-resistant strains has been reported. As such, this study aimed to investigate the activity of delafloxacin against a collection of S. aureus, and to determine the mechanisms of resistance. The activity of delafloxacin was measured in 59 S. aureus clinical isolates [40 methicillin-resistant S. aureus (MRSA) and 19 methicillin-susceptible S. aureus (MSSA)]. Whole-genome sequencing (WGS) was performed in the isolates resistant to delafloxacin. The minimum inhibitory concentrations required to inactivate 50% and 90% of the isolates (MIC50 and MIC90, respectively) were higher in MRSA (0.19 mg/L and 0.75 mg/L, respectively) than in MSSA (0.008 mg/L and 0.25 mg/L, respectively). Furthermore, 10 S. aureus clinical isolates (16.9%) were categorized as resistant to delafloxacin. Regarding the WGS data, several mutations were found in the quinolone resistance-determining region. Nevertheless, a mutation in the same position (E84K and E84V) of topoisomerase IV (ParC) was found exclusively in the four high-level delafloxacin-resistant isolates. Interestingly, a plasmid-encoded qacC gene (efflux pump) was found to be harboured by the isolate with the highest delafloxacin MIC value (32 mg/L). The use of a wide-spectrum efflux pump inhibitor revealed an important contribution of this system to the acquisition of delafloxacin resistance. In conclusion, delafloxacin has activity against S. aureus, including MRSA. However, this study showed that mutations in position 84 of ParC and the acquisition of a QacC efflux pump are key factors for the development of delafloxacin resistance in S. aureus.

Rapid Detection of Piperacillin-Tazobactam Resistance in Klebsiella pneumoniae and Escherichia coli.

Rapid determination of susceptibility to piperacillin-tazobactam (TZP) is very important since the development of antibiotic resistance and inadequate treatment could increase the risk of clinical failure in infected patients, especially if such resistance is unknown to the clinician. Therefore, based on color change from orange to yellow of phenol red due to glucose metabolism (bacterial growth) in the presence of an adequate concentration of TZP (10 mg/L piperacillin and 5 mg/L tazobactam), the RapidTZP test has been developed to detect TZP resistance in Escherichia coli and Klebsiella pneumoniae isolates in a maximum of 3 h. A total of 140 isolates, 43 of E. coli and 97 of K. pneumoniae, were used to evaluate the performance of the test, 60 being resistant to TZP. The sensitivity and specificity of the test were 98.24% and 100%, respectively. Additionally, the RapidTZP test was validated by a pellet obtained directly from blood culture bottles. A total of 37 positive blood cultures for E. coli and 43 for K. pneumoniae were used for validation, 8 of them resistant to TZP. The sensitivity and specificity shown in the evaluation were 100% for both parameters. This new test is easy, fast, and accurate, providing results in 3 h. IMPORTANCE TZP is an antibiotic widely used for the empirical treatment of severe infections such as bloodstream infections. However, resistance to TZP in K. pneumoniae and E. coli has been increasing in the last few years. Thus, rapid detection of TZP resistance is critical to optimize the empirical treatment of patients with severe infections. In this study, we developed and evaluated a rapid test (RapidTZP) for the detection of TZP resistance in K. pneumoniae and E. coli directly from positive hemocultures in just 3 h. This rapid test has been validated on 138 K. pneumoniae and E. coli clinical isolates directly from agar plates and 80 K. pneumoniae and E. coli isolates causing bloodstream infections. The results demonstrate that the RapidTZP test has great clinical potential to optimize the empirical treatment of patients with bloodstream infections.

In Vitro and In Vivo Virulence Study of Listeria monocytogenes Isolated from the Andalusian Outbreak in 2019.

In 2019, the biggest listeriosis outbreak by Listeria monocytogenes (Lm) in the South of Spain was reported, resulting in the death of three patients from 207 confirmed cases. One strain, belonging to clonal complex 388 (Lm CC388), has been isolated. We aimed to determine the Lm CC388 virulence in comparison with other highly virulent clones such as Lm CC1 and Lm CC4, in vitro and in vivo. Four L. monocytogenes strains (Lm CC388, Lm CC1, Lm CC4 and ATCC 19115) were used. Attachment to human lung epithelial cells (A549 cells) by these strains was characterized by adherence and invasion assays. Their cytotoxicities to A549 cells were evaluated by determining the cells viability. Their hemolysis activity was determined also. A murine intravenous infection model using these was performed to determine the concentration of bacteria in tissues and blood. Lm CC388 interaction with A549 cells is non-significantly higher than that of ATCC 19115 and Lm CC1, and lower than that of Lm CC4. Lm CC388 cytotoxicity is higher than that of ATCC 19115 and Lm CC1, and lower than that of Lm CC4. Moreover, Lm CC388 hemolysis activity is lower than that of the Lm CC4 strain, and higher than that of Lm CC1. Finally, in the murine intravenous infection model by Lm CC388, higher bacterial loads in tissues and at similar levels of Lm CC4 were observed. Although a lower rate of mortality of patients during the listeriosis outbreak in Spain in 2019 has been reported, the Lm CC388 strain has shown a greater or similar pathogenicity level in vitro and in an animal model, like Lm CC1 and Lm CC4.