In vivo development of resistance to novel ß-lactam/ß-lactamase inhibitor combinations in KPC-producing Klebsiella pneumoniae infections: a case series.

INTRODUCTION: Understanding the dynamics that may characterize the emergence of KPC variants with resistance to novel ß-lactam/ß-lactamase inhibitor combinations (ßL/ßLICs) represents a challenge to be overcome in the appropriate use of recently introduced antibiotics. METHODS: Retrospective case series describing development of multiple resistance to novel ßL/ßLICs in patients with KPC-producing Klebsiella pneumoniae (KPC-Kp) infections treated with these drugs. Clinical-microbiological investigation and characterization of longitudinal strains by Whole-Genome Sequencing were performed. RESULTS: Four patients with KPC-Kp bloodstream infections were included. Most frequent clinical features were kidney disease, obesity, cardiac surgery as reason for admission, ICU stay, treatment with ceftazidime/avibactam, and pneumonia and/or acute kidney injury needing renal replacement therapy as KPC-Kp sepsis-associated complications. The development of resistance to ceftazidime/avibactam was observed in four longitudinal strains (three of which were co-resistant to aztreonam/avibactam and cefiderocol) following treatments with ceftazidime/avibactam (n = 3) or cefiderocol (n = 1). Resistance to meropenem/vaborbactam and imipenem/cilastatin/relebactam was observed in one case after exposure to ceftazidime/avibactam and imipenem/cilastatin/relebactam. Resistome analysis showed that resistance to novel ßL/ßLICs was related to specific mutations within blaKPC carbapenemase gene (D179Y mutation [KPC-33]; deletion Δ242-GT-243 [KPC-14]) in three longitudinal strains, while porin loss (truncated OmpK35 and OmpK36 porins) was observed in one case. CONCLUSION: Therapy with novel ßL/ßLICs or cefiderocol may lead to the selection of resistant mutants in the presence of factors influencing the achievement of PK/PD targets. KPC variants are mainly associated with resistance to ceftazidime/avibactam, and some of them (e.g. KPC-14) may also be associated with reduced susceptibility to aztreonam/avibactam and/or cefiderocol. Loss of function of the OmpK35 and OmpK36 porins appears to play a role in the development of resistance to meropenem/vaborbactam and/or imipenem/relebactam, but other mechanisms may also be involved.

Suitable Mouse Model to Study Dynamics of West Nile Virus Infection in Culex quinquefasciatus Mosquitoes.

West Nile Virus (WNV) poses a significant global public health threat as a mosquito-borne pathogen. While laboratory mouse models have historically played a crucial role in understanding virus biology, recent research has focused on utilizing immunocompromised models to study arboviruses like dengue and Zika viruses, particularly their interactions with Aedes aegypti mosquitoes. However, there has been a shortage of suitable mouse models for investigating WNV and St. Louis encephalitis virus interactions with their primary vectors, Culex spp. mosquitoes. Here, we establish the AG129 mouse (IFN α/ß/γ R-/-) as an effective vertebrate model for examining mosquito-WNV interactions. Following intraperitoneal injection, AG129 mice exhibited transient viremia lasting several days, peaking on the second or third day post-infection, which is sufficient to infect Culex quinquefasciatus mosquitoes during a blood meal. We also observed WNV replication in the midgut and dissemination to other tissues, including the fat body, in infected mosquitoes. Notably, infectious virions were present in the saliva of a viremic AG129 mouse 16 days post-exposure, indicating successful transmission capacity. These findings highlight the utility of AG129 mice for studying vector competence and WNV-mosquito interactions.

Detection of volatile organic compounds as new paradigm to accelerate antimicrobial susceptibility testing: performance evaluation of VITEK® REVEAL™.

OBJECTIVES: The measurement of VOCs release in the headspace of a bacterial culture represents a new approach to rapidly assess antimicrobial susceptibility. Herein, we evaluated the diagnostic performance of the VITEK® REVEAL™ system directly from a collection of Gram-negative positive blood cultures. MATERIALS AND METHODS: One hundred and twenty-eight positive blood cultures were included in the analysis (Enterobacterales, n = 95; Pseudomonas aeruginosa, n = 21; Acinetobacter baumannii complex, n = 12). Samples were processed using VITEK® REVEAL™ according to the manufacturer's recommendations, and MICs of 22 antimicrobials were compared with those obtained using reference methods. Categorical agreement (CA), essential agreement (EA) and categorical errors were calculated. RESULTS: Overall, 2220 strain/antibiotic pair combinations were analysed. Of these, most were classified as resistant by reference antimicrobial susceptibility testing (1091/2220; 48.7%). The overall CA and EA were 97.6% and 97.7%, respectively. CA ranged from 97.5% in Enterobacterales to 97.9% in both P. aeruginosa and A. baumannii complex. The overall number of categorical discrepancies were: 18 very major errors (1.6%), 13 major errors (1.2%) and 22 minor errors (2.4%). EA ranged from 95.2% in P. aeruginosa to 98.1% in Enterobacterales. Screening test for ESBL phenotype was positive, indeterminate and negative in 13.7%, 32.6% and 27.4% of Enterobacterales isolates tested by both VITEK® REVEAL™ and the reference method, showing 100% CA. CONCLUSIONS: VITEK® REVEAL™ represents a reliable tool to obtain antimicrobial susceptibility results of the main Gram-negative species directly from positive blood cultures with time to results of less than 8 h.

Clinical and microbiological features of positive blood culture episodes caused by non-fermenting gram-negative bacilli other than Pseudomonas and Acinetobacter species (2020-2023).

INTRODUCTION: Non-fermenting Gram-negative bacilli (NFGNB) other than Pseudomonas aeruginosa and Acinetobacter baumannii complex are pathogens of interest due to their ability to cause health-care associated infections and display complex drug resistance phenotypes. However, their clinical and microbiological landscape is still poorly characterized. METHODS: Observational retrospective study including all hospitalized patients presenting with a positive positive blood culture (BC) episode caused by less common NFGNB over a four-year period (January 2020-December 2023). Clinical-microbiological features and factors associated with mortality were investigated. RESULTS: Sixty-six less common NFGNB isolates other than Pseudomonas and Acinetobacter species causing 63 positive BC episodes were recovered from 60 patients. Positive BC episodes were predominantly sustained by Stenotrophomonas maltophilia (49.2%) followed by Achromobacter species (15.9%) that exhibited the most complex resistance phenotype. Positive BC episodes had bloodstream infection criteria in 95.2% of cases (60 out 63), being intravascular device (30.2%) and respiratory tract (19.1%) the main sources of infection. Fourteen-day, 30-day, and in-hospital mortality rates were 6.4%, 9.5%, and 15.9%, respectively. The longer time from admission to the positive BC episode, older age, diabetes, admission due to sepsis, and higher Charlson Comorbidity Index were identified as the main predictors of in-hospital mortality. CONCLUSIONS: Positive BC episodes sustained by NFGNB other than Pseudomonas and Acinetobacter species were predominantly sustained by Stenotrophomonas maltophilia and Achromobacter species, having bloodstream infection criteria in the vast majority of cases. Factors that have emerged to be associated with mortality highlighted how these species may have more room in prolonged hospitalisation and at the end of life for patients with chronic organ diseases.

From Forgotten Pathogen to Target for New Vaccines: What Clinicians Need to Know about Respiratory Syncytial Virus Infection in Older Adults.

Respiratory syncytial virus (RSV) is increasingly recognized as being implicated in acute illness in older adults, with a significant weight in hospitalizations for respiratory illness and death. By means of a best-evidence review, this paper aims to investigate whether RSV can be considered a forgotten pathogen in older patients, looking at trends in the literature volume and exploring possible epidemiological and clinical features underlying the focus given to it. We then present an assessment of its disease burden and present and future strategies for its reduction, particularly in light of the recent availability of new vaccines.

The High Capacity of Brazilian Aedes aegypti Populations to Transmit a Locally Circulating Lineage of Chikungunya Virus.

The incidence of chikungunya has dramatically surged worldwide in recent decades, imposing an expanding burden on public health. In recent years, South America, particularly Brazil, has experienced outbreaks that have ravaged populations following the rapid dissemination of the chikungunya virus (CHIKV), which was first detected in 2014. The primary vector for CHIKV transmission is the urban mosquito species Aedes aegypti, which is highly prevalent throughout Brazil. However, the impact of the locally circulating CHIKV genotypes and specific combinations of local mosquito populations on vector competence remains unexplored. Here, we experimentally analyzed and compared the infectivity and transmissibility of the CHIKV-ECSA lineage recently isolated in Brazil among four Ae. aegypti populations collected from different regions of the country. When exposed to CHIKV-infected AG129 mice for blood feeding, all the mosquito populations displayed high infection rates and dissemination efficiency. Furthermore, we observed that all the populations were highly efficient in transmitting CHIKV to a vertebrate host (naïve AG129 mice) as early as eight days post-infection. These results demonstrate the high capacity of Brazilian Ae. aegypti populations to transmit the locally circulating CHIKV-ECSA lineage. This observation could help to explain the high prevalence of the CHIKV-ECSA lineage over the Asian lineage, which was also detected in Brazil in 2014. However, further studies comparing both lineages are necessary to gain a better understanding of the vector's importance in the epidemiology of CHIKV in the Americas.

Performance evaluation of Bruker UMIC® microdilution panel and disc diffusion to determine cefiderocol susceptibility in Enterobacterales, Acinetobacter baumannii, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Achromobacter xylosoxidans and Burkolderia species.

PURPOSE: Cefiderocol susceptibility testing (AST) represents an open challenge for clinical microbiology. Herein, we evaluated the performance of the UMIC® Cefiderocol broth microdilution (BMD) test and disc diffusion on Gram-negative species. METHODS: UMIC® Cefiderocol BMD test, disc diffusion and reference BMD were in parallel performed on a collection of 256 clinical isolates. Categorical agreement (CA), essential agreement (EA), bias, major errors (MEs) and very major errors (VMEs) were calculated for both AST methods. RESULTS: The UMIC® Cefiderocol BMD strip exhibited an EA < 90% (85.5%), a CA higher than 90% (93.7%) and a low number of VMEs (n = 4, 4.2%) and MEs (n = 12, 7.4%). UMIC® Cefiderocol identified 96.2% of the resistant isolates [Enterobacterales, (39/40); P. aeruginosa (19/19); A. xylosoxidans (5/6); S. maltophilia (5/6); Burkholderia spp. (8/8)]. Disc diffusion showed a high CA (from 94.9 to 100%) regardless of disc manufacturer in Enterobacterales, P. aeuroginosa, A. baumannii and S. maltophilia. However, high rates of results falling in the area of technical uncertainty (ATU) were observed in Enterobacterales (34/90, 37.8%) and P. aeruginosa (16/40, 40%). Disc diffusion showed a poor performance in A. xylosoxidans and Burkholderia spp. if PK/PD breakpoint was used (overall, 5/9 VMEs; in contrast, the use of P. aeruginosa-specific breakpoints resulted in 100% of CA with 24.6% of results in the ATU). CONCLUSION: In conclusion, disc diffusion and UMIC® Cefiderocol are valid methods for the determination of cefiderocol susceptibility. Given the high number of results in the ATU by disc diffusion, a combined use of both AST methods may represent a solution to overcome the challenge of cefiderocol susceptibility testing in routine microbiology laboratories.

Prevalence and mortality of ceftazidime/avibactam-resistant KPC-producing Klebsiella pneumoniae bloodstream infections (2018-2022).

INTRODUCTION: Ceftazidime/avibactam-resistance in Klebsiella pneumoniae carbapenemase-producing Klebsiella pneumoniae (KPC-Kp) is a topic of great interest for epidemiological, diagnostic, and therapeutical reasons. However, data on its prevalence and burden on mortality in patients with bloodstream infection (BSI) are lacking. This study was aimed at identifying risk factors for mortality in patients suffering from ceftazidime/avibactam-resistant KPC-Kp BSI. METHODS: An observational retrospective study (January 2018-December 2022) was conducted at a tertiary hospital including all consecutive hospitalized adult patients with a ceftazidime/avibactam-resistant KPC-Kp BSI. Data on baseline clinical features, management, and admission outcomes were analyzed. RESULTS: Over the study period, among all the KPC-Kp BSI events recorded, 38 (10.5%) were caused by ceftazidime/avibactam-resistant KPC-Kp strains, 37 events being finally included. The ceftazidime/avibactam-resistant KPC-Kp strains revealed susceptibility restoration to at least one carbapenem in more than 60% of cases. In-hospital and 30-day all-cause mortality rates were 22% and 16.2%, respectively. Non-survivors suffered from more baseline comorbidities and experienced a more severe ceftazidime/avibactam-resistant KPC-Kp BSI presentation (i.e., both the Pitt Bacteremia and INCREMENT-CPE scores were significantly higher). Presenting with a higher Charlson Comorbidity Index, chronic kidney disease-KDIGO stage 3A or worse-having recently gone through renal replacement therapy, having suffered from an acute kidney injury following the ceftazidime/avibactam-resistant KPC-Kp BSI, and being admitted for cardiac surgery were the strongest predictors of mortality. CONCLUSION: Ceftazidime/avibactam resistance in KPC-Kp BSI easily emerged in our highly KPC-Kp endemic area with remarkable mortality rates. Our findings might provide physicians possibly actionable information when managing patients with a ceftazidime/avibactam-resistant KPC-Kp BSI.

Bloodstream Infections by Pantoea Species: Clinical and Microbiological Findings from a Retrospective Study, Italy, 2018-2023.

(1) Background: The widespread use of MALDI-TOF coupled to mass spectrometry has improved diagnostic accuracy by identifying uncommon bacteria. Among Enterobacterales, Pantoea species have been seen to be implicated in several human infections, but their clinical and microbiological framework is currently based on a few anecdotal reports. (2) Methods: We conducted this five-year (2018-2023) single-center study aimed at investigating the prevalence and clinical and microbiological findings of Pantoea species bloodstream infections. (3) Results: Among the 4996 bloodstream infection Gram-negative isolates collected during the study period, Pantoea species accounted for 0.4% (n = 19) of isolates from 19 different patients, 5 of them being pediatric cases. Among Pantoea species isolates, P. agglomerans was the most frequently detected (45%; n = 9) followed by P. eucrina (30%; n = 6) and P. septica (15%; n = 3). Malignancy (35.7%) in adults and malignancy (40%) and cerebrovascular disease following meconium aspiration (40%) in pediatric patients as comorbidities and shivering and/or fever following parenteral infusion (36.8%) as a symptom/sign of Pantoea species bloodstream infection onset were the most frequently observed clinical features. Among adults, primary bloodstream infection was the most frequent (50%), whereas among pediatric patients, the most commonly identified sources of infection were catheter-related (40%) and the respiratory tract (40%). Overall, Pantoea species bloodstream infection isolates displayed high susceptibility to all the antibiotics except for ampicillin (63.2%), fosfomycin (73.7%), and piperacillin/tazobactam (84.2%). Targeted antibiotic treatment was prescribed as monotherapy for adults (71.4%) and combination therapy for pediatric patients (60%). The most prescribed antibiotic regimens were piperacillin/tazobactam (21.4%) in adults and meropenem- (40%) and aminoglycoside-containing (40%) antibiotics in pediatric patients. The overall 28-day all-cause mortality rate was 5.3% (n = 1). (4) Conclusions: The prevalence and 28-day mortality rate of Pantoea species bloodstream infections were low. The prescription of targeted therapy including broad-spectrum antibiotics could indicate an underestimation of the specific involvement of the Pantoea species in the onset of the disease, warranting further studies defining their pathogenic potential.

High capacity of Brazilian Aedes aegypti populations to transmit a locally circulating lineage of Chikungunya virus.

The global incidence of chikungunya has surged in recent decades, with South America, particularly Brazil, experiencing devastating outbreaks. The primary vector for transmitting CHIKV in urban areas is the mosquito species Aedes aegypti, which is very abundant in Brazil. However, little is known about the impact of locally circulating CHIKV genotypes and specific combinations of mosquito populations on vector competence. In this study, we analyzed and compared the infectivity and transmissibility of a recently isolated CHIKV-ECSA lineage from Brazil among four Ae. aegypti populations collected from different regions of the country. When exposed to CHIKV-infected mice for blood feeding, all mosquito populations showed high infection rates and dissemination efficiency. Moreover, using a mouse model to assess transmission rates in a manner that better mirrors natural cycles, we observed that these populations exhibit highly efficient transmission rates of CHIKV-ECSA. Our findings underscore the robust capability of Brazilian Ae. aegypti populations to transmit the locally circulating CHIKV-ECSA lineage, potentially explaining its higher prevalence compared to the Asian lineage also introduced in Brazil.

Tuning of Silver Content on the Antibacterial and Biological Properties of Poly(ɛ-caprolactone)/Biphasic Calcium Phosphate 3D-Scaffolds for Bone Tissue Engineering.

There is a growing interest in tissue engineering, in which biomaterials play a pivotal role in promoting bone regeneration. Furthermore, smart functionalization can provide biomaterials with the additional role of preventing orthopedic infections. Due to the growing microbial resistance to antimicrobials used to treat those infections, metal ions, such as silver, thanks to their known wide range of bactericidal properties, are believed to be promising additives in developing antibacterial biomaterials. In this work, novel poly(ε-caprolactone) (PCL)-based 3D scaffolds have been designed and developed, where the polymer matrix was modified with both silver (Ag), to supply antibacterial behavior, and calcium phosphates (biphasic calcium phosphate, BCP) particles to impart bioactive/bioresorbable properties. The microstructural analysis showed that constructs were characterized by square-shaped macropores, in line with the morphology and size of the templating salts used as pore formers. Degradation tests demonstrated the important role of calcium phosphates in improving PCL hydrophilicity, leading to a higher degradation degree for BCP/PCL composites compared to the neat polymer after 18 days of soaking. The appearance of an inhibition halo around the silver-functionalized PCL scaffolds for assayed microorganisms and a significant (p < 0.05) decrease in both adherent and planktonic bacteria demonstrate the Ag+ release from the 3D constructs. Furthermore, the PCL scaffolds enriched with the lowest silver percentages did not hamper the viability and proliferation of Saos-2 cells. A synergic combination of antimicrobial, osteoproliferative and biodegradable features provided to 3D scaffolds the required potential for bone tissue engineering, beside anti-microbial properties for reduction in prosthetic joints infections.

Prevalence and Impact on Mortality of Colonization and Super-Infection by Carbapenem-Resistant Gram-Negative Organisms in COVID-19 Hospitalized Patients.

BACKGROUND: The relationship between superinfection by multidrug-resistant Gram-negative bacteria and mortality among SARS-CoV-2 hospitalized patients is still unclear. Carbapenem-resistant Acinetobacter baumannii and carbapenemase-producing Enterobacterales are among the most frequently isolated species when it comes to hospital-acquired superinfections among SARS-CoV-2 patients. METHODS: Herein, a retrospective study was carried out using data from adult patients hospitalized for COVID-19. The interaction between in-hospital mortality and rectal carriage and superinfection by carbapenemase-producing Enterobacterales and/or carbapenem-resistant Acinetobacter baumannii was assessed. RESULTS: The incidence of KPC-producing Klebsiella pneumoniae and/or carbapenem-resistant Acinetobacter baumannii rectal carriage was 30%. Bloodstream infection and/or pneumonia due to KPC-producing Klebsiella pneumoniae and/or carbapenem-resistant Acinetobacter baumannii occurred in 20% of patients. A higher Charlson comorbidity index (OR 1.41, 95% CI 1.24-1.59), being submitted to invasive mechanical ventilation/ECMO ≥ 96 h (OR 6.34, 95% CI 3.18-12.62), being treated with systemic corticosteroids (OR 4.67, 95% CI 2.43-9.05) and having lymphopenia at the time of admission (OR 0.54, 95% CI 0.40-0.72) were the features most strongly associated with in-hospital mortality. CONCLUSIONS: Although KPC-producing Klebsiella pneumoniae and/or carbapenem-resistant Acinetobacter baumannii rectal carriage, and/or bloodstream infection/pneumonia were diagnosed in a remarkable percentage of COVID-19 patients, their impact on in-hospital mortality was not significant. Further studies are needed to assess the burden of antimicrobial resistance as a legacy of COVID-19 in order to identify future prevention opportunities.

Impact of NG-Test CTX-M MULTI Immunochromatographic Assay on Antimicrobial Management of Escherichia coli Bloodstream Infections.

Rapid detection of extended-spectrum-ß-lactamase (ESBL) is of paramount importance to accelerate clinical decision-making, optimize antibiotic treatment, and implement adequate infection control measures. This study was aimed at assessing the impact of direct detection of CTX-M ESBL-producers on antimicrobial management of Escherichia coli bloodstream infections over a 2-year period. This study included all E. coli bloodstream infection (BSI) events that were serially processed through a rapid workflow with communication to the clinicians of direct detection of CTX-M ESBL-producers and conventional culture-based workflow. Antimicrobial management was retrospectively analyzed to assess the contribution of the rapid test result. A total of 199 E. coli BSI events with a report of direct detection of CTX-M ESBL production results were included. Of these, 33.7% (n = 67) and 66.3% (n = 132) were reported as positive and negative CTX-M producers, respectively. Detection of CTX-M positive results induced more antibiotic therapy modifications (mainly towards carbapenem-containing regimens, p < 0.01), and antimicrobial susceptibility testing results of CTX-M ESBL-producing E. coli isolates induced more antibiotic escalations towards carbapenem-containing regimens (p < 0.01). Direct detection of CTX-M ESBL-producing E. coli resulted in a remarkable rate of antibiotic optimizations on the same day of blood culture processing. Observing antibiotic management following the availability of antimicrobial susceptibility testing results, additional early optimizations in escalation could probably have been made if the rapid test data had been used. Detection of CTX-M negative results resulted in few therapeutic changes, which could have probably been higher, integrating epidemiological and clinical data.

Disc Diffusion and ComASP® Cefiderocol Microdilution Panel to Overcome the Challenge of Cefiderocol Susceptibility Testing in Clinical Laboratory Routine.

Cefiderocol susceptibility testing represents a major challenge for clinical microbiology. Although disc diffusion showed robustness to test cefiderocol susceptibility, large areas of technical uncertainty (ATU) are reported by current EUCAST breakpoints. Herein, we evaluated the in vitro activity of cefiderocol on a collection of 286 difficult-to-treat Gram-negative isolates using disc diffusion and ComASP® cefiderocol microdilution panel. Broth microdilution (BMD) in iron-depleted Mueller-Hinton broth was used as reference method. Following the EUCAST guidelines, disc diffusion allowed to determine cefiderocol susceptibility (susceptible or resistant) in 78.6%, 88.1%, 85.4% and 100% of Enterobacterales, P. aeruginosa, A. baumannii and S. maltophilia isolates tested, respectively. ComASP® cefiderocol panel showed 94% and 84% of overall categorical agreement and essential agreement. Only one very major error and two major errors were observed, for MIC values nearly close to the resistance breakpoint (2 mg/L). Overall, 20.5% of the carbapenemase-producing Enterobacterales that achieved ATU results by the disc diffusion method tested resistant by both ComASP® panel and reference BMD. Conversely, all VIM-producing P. aeruginosa showed MIC values in the susceptible range (≤2 mg/L). Lastly, only six out of seven (85.7%) A. baumannii isolates showing inhibition zones <17 mm tested resistant by both ComASP® panel and the reference BMD suggesting that inhibition zone <17 mm are not unequivocally suggestive of resistance. Our results, although obtained on a limited number of isolates, suggest that the combination of disc diffusion with a ComASP® cefiderocol microdilution panel could be a viable solution to overcome the challenge of cefiderocol susceptibility testing in routine microbiology laboratories.

Multicentre Surveillance of Candida Species from Blood Cultures during the SARS-CoV-2 Pandemic in Southern Europe (CANCoVEU Project).

Introduction: Surveillance of Candida species isolates from blood cultures (BCs) in Europe is considered fragmented, unable to allow the definition of targets of antifungal stewardship recommendations especially during the SARS-CoV-2 pandemic. Methods: We performed a multicentric retrospective study including all consecutive BC Candida isolates from six Southern European tertiary hospitals (1st January 2020 to 31st December 2021). Etiology, antifungal susceptibility patterns, and clinical setting were analyzed and compared. Results: C. albicans was the dominant species (45.1%), while C. auris was undetected. Candida species positive BC events increased significantly in COVID-19 ICUs in 2021 but decreased in other ICUs. Resistance to azole increased significantly and remained very high in C. albicans (fluconazole from 0.7% to 4.5%, p = 0.03) and C. parapsilosis complex (fluconazole up to 24.5% and voriconazole up to 8.9%), respectively. Resistance to caspofungin was remarkable in C. tropicalis (10%) and C. krusei (20%), while resistance to at least one echinocandin increased in 2021, especially in C. parapsilosis complex (from 0.8% to 5.1%, p = 0.05). Although no significant differences were observed over the study period, fluconazole and echinocandin resistance increased in COVID-19 ICUs by up to 14% and 5.8%, respectively, but remained undetected in non-intensive COVID-19 wards. Conclusions: Antifungal stewardship activities aimed at monitoring resistance to echinocandin in C. tropicalis and C. krusei, and against the spread of fluconazole resistant C. parapsilosis complex isolates are highly desirable. In COVID-19 patients, antifungal resistance was mostly present when the illness had a critical course.

Rapid diagnostics and ceftazidime/avibactam for KPC-producing Klebsiella pneumoniae bloodstream infections: impact on mortality and role of combination therapy.

This study was aimed at investigating risk factors for mortality in patients suffering from KPC-producing Klebsiella pneumoniae (KPC-Kp) bloodstream infections (BSIs), evaluating the impact of rapid diagnostics and ceftazidime/avibactam use. This observational retrospective study (January 2017-May 2021) included all patients with a KPC-Kp BSI. Uni-multivariable analyses were carried out to evaluate the effect of clinical variables on both in-hospital death (IHD) and 30-day all-cause mortality, and the role of the combination of ceftazidime/avibactam plus polymyxin. One hundred and ninety-six patients met the study's inclusion criteria. Older age, having undergone renal replacement therapy during the 30 days preceding the KPC-Kp BSI onset, having an INCREMENT-CPE score ≥ 8, and having suffered from a superimposed and/or following KPC-Kp BSI treatment candidemia were found to be the main factors associated with both mortality rates. Among protective factors, the centrality of ceftazidime/avibactam in monotherapy (IHD: OR: 0.34; CI 95%: 0.11-1.00-30-day all-cause mortality: OR: 0.18; CI 95%: 0.04-0.77) or combination (IHD: OR: 0.51; CI 95%: 0.22-1.19-30-day all-cause mortality: OR: 0.62; CI 95%: 0.21-1.84) emerged and became even more evident once the effect of ceftazidime/avibactam plus polymyxin was removed. Rapid diagnostics may be useful to adopt more effective strategies for the treatment of KPC-Kp BSI patients and implement infection control measures, even if not associated with higher patient survival. Ceftazidime/avibactam, even when used alone, represents an important option against KPC-Kp, while combined use with polymyxin might not have altered its efficacy. Patient comorbidities, severity of BSI, and complications such as candidemia were confirmed to have a significant burden on survival.

Dalbavancin Boosts the Ability of Neutrophils to Fight Methicillin-Resistant Staphylococcus aureus.

Polymorphonuclear leukocytes (PMNs) are the most important cell type involved in the early nonspecific host response to bacterial pathogens. Staphylococcus aureus has evolved mechanisms to evade immune responses that contribute to its persistence in PMNs, and acquired resistance to several antimicrobials. Additionally, methicillin-resistant S. aureus (MRSA) is one of the most common causes of acute bacterial skin and skin-structure infections (ABSSSIs). Dalbavancin (DBV), a lipoglycopeptide, is indicated for the treatment of ABSSSIs, and has a broad spectrum of action against most microorganisms. Here, we sought to determine the effect of DBV on the neutrophil killing of MRSA and its potential immunomodulating activity. Our results revealed that DBV boosts MRSA killing by acting on both bacteria and PMNs. DBV pre-treatment of PMNs did not change the respiratory burst or degranulation, while an increased trend in neutrophil extracellular traps-associated elastase and in the production of TNFα and CXCL8 was revealed. In parallel, DBV caused a delay in the apoptosis of MRSA-infected neutrophils. In conclusion, we demonstrated a cooperative effect between the antimicrobial properties of PMNs and DBV, thus owing to their immunomodulatory activity. In the choice of the treatment management of serious S. aureus infections, DBV should be considered as an outstanding option since it reinforces PMNs pathogen clearance capability by exerting its effect directly, not only on MRSA but also on neutrophils.

Activity of cefiderocol and synergy of novel ß-lactam-ß-lactamase inhibitor-based combinations against metallo-ß-lactamase-producing gram-negative bacilli: insights from a two-year study (2019-2020).

This study was aimed at analyzing the prevalence of metallo-ß-lactamase-producing Gram-negative bacilli (MBL-GNB) and evaluating both in vitro activity of cefiderocol and synergy of novel ß-lactam-ß-lactamase inhibitor-based combinations. Carbapenemase-producing Enterobacterales and meropenem-non-susceptible P. aeruginosa clinical strains were collected (2019-2020) and prevalence of MBL-producers investigated. Activity of cefiderocol was evaluated and synergistic effects of cefiderocol in combination with ceftazidime/avibactam vs aztreonam plus ceftazidime/avibactam vs meropenem/vaborbactam plus aztreonam were compared. Among carbapenemase-producing Enterobacterales, 87% (n = 307) produced KPC, 11.6% (n = 41) produced MBL, and 1.4% (n = 5) produced OXA-48-like. Among MBL-producing Enterobacterales, 78.1% (n = 32) and 21.9% (n = 9) were VIM- and NDM-producers, respectively. Among meropenem-non-susceptible P. aeruginosa, 1.9% (n = 8) produced VIM-type MBL. Cefiderocol resistance rate in VIM-producing Enterobacterales, VIM-producing P. aeruginosa, and NDM-producing Enterobacterales, was 6.2%, 12.5%, and 88.9%, respectively. Among MBL-producers tested, cefiderocol in combination with ceftazidime/avibactam showed a synergy rate of 20%, while for both aztreonam plus ceftazidime/avibactam and meropenem/vaborbactam plus aztreonam was 40%. Prevalence of MBL-producing Enterobacterales was remarkable. VIM-producing isolates were almost all susceptible to cefiderocol, while NDM-producers were often resistant. Meropenem/vaborbactam in combination with aztreonam showed similar synergistic activity to ceftazidime/avibactam plus aztreonam but the addition of aztreonam reduced MICs below the resistance breakpoint only for meropenem/vaborbactam.

Synergistic Effect of Clinically Available Beta-Lactamase Inhibitors Combined with Cefiderocol against Carbapenemase-Producing Gram-Negative Organisms.

The role of ß-lactamases in reduced susceptibility or resistance to cefiderocol has been supported by recent reports. The purpose of this study was to investigate the in vitro impact of clinically available ß-lactamase inhibitors on cefiderocol activity against characterized carbapenemase-producing Gram-negative isolates. A collection of 39 well-characterized Gram-negative isolates obtained from various clinical sources and countries were included. Cefiderocol antimicrobial susceptibility was evaluated via reference broth microdilution. The chequerboard microdilution method and time-kill assays were used to determine the synergy of tazobactam, avibactam, vaborbactam and relebactam in combination with cefiderocol. MICs of cefiderocol presented a 4- to 256-fold reduction against Klebsiella pneumoniae carbapenemase (KPC)-producing Gram-negative isolates (predominantly K. pneumoniae) when avibactam, vaborbactam and relebactam were combined individually. Notably, the KPC-inhibitors led to a 4- to 32-fold reduction in cefiderocol MICs in the four cefiderocol-resistant KPC-producing K. pneumoniae isolates, showing restoration of cefiderocol susceptibility (MIC ≤ 2 mg/L) in ten out of twelve cases. Tazobactam led to a 4- to 64-fold decrease in cefiderocol MICs only in K. pneumoniae strains harbouring blaKPC-41, blaKPC-31, blaKPC-53 and blaKPC-66. The synergistic effect of all serine-ß-lactamase inhibitors on cefiderocol activity was also shown in OXA-48-like-producing Enterobacterales strains. Conversely, a combination of ß-lactamases inhibitors with cefiderocol was not synergistic with all OXA-23-like-producing strains and most metallo-ß-lactamases producers. In conclusion, the addition of clinically available serine ß-lactamase inhibitors to cefiderocol might represent an important development in the formulation to increase its spectrum and therapeutic efficacy, and to limit in vivo resistance emergence.