Antimicrobial Activity of Ceftazidime-Avibactam, Ceftolozane-Tazobactam and Comparators Tested Against Pseudomonas aeruginosa and Klebsiella pneumoniae Isolates from United States Medical Centers in 2016-2018

Novel β-lactam-β-lactamase inhibitors as monotherapy versus combination for the treatment of drug-resistant Pseudomonas aeruginosa infections: A multicenter cohort study

BACKGROUND

Data comparing the clinical outcomes of novel β-lactam-β-lactamase inhibitors given in combination versus monotherapy for the treatment of multidrug-resistant (MDR) P. aeruginosa infections are lacking.

METHOD

This retrospective cohort study included patients who received novel β-lactam-β-lactamase inhibitors as monotherapy or in combination for the treatment of MDR P. aeruginosa infections. The study was conducted between 2017 and 2022 in 6 tertiary care hospitals in Saudi Arabia. Overall in-hospital mortality, 30-day mortality, clinical cure, and acute kidney injury (AKI) were compared between recipients of monotherapy versus combination using multivariate logistic regression analysis.

RESULT

118 patients and 82 patients were included in monotherapy and combination therapy arms, respectively. The cohort represented an ill population with 56% in the intensive care unit and 37% in septic shock. A total of 19% of patients presented with bacteremia. Compared to monotherapy, combination therapy did not significantly differ in clinical cure (57% vs. 68%; P = 0.313; OR, 0.63; 95% CI, 0.36-1.14) in-hospital mortality (45% vs. 37%; P = 0.267; OR, 1.38; 95% CI, 0.78-2.45), or 30-day mortality (27% vs. 24%; P = 0.619; OR, 1.18; 95% CI, 0.62-1.25). However, AKI (32% vs. 12%; P = 0.0006; OR, 3.45; 95% CI, 1.67-7.13) was significantly more common in patients who received combination therapy.

CONCLUSION

Novel β-lactam-β-lactamase inhibitors when used in combination with other antibiotics did not add clinical benefit compared to their use as monotherapy in the treatment of MDR P. aeruginosa infections. A Combination regimen was associated with an increased risk of nephrotoxicity.

Identification of bla OXA-23 gene in resistant Pseudomonas aeruginosa strains isolated from cows and humans in Basra province, Iraq

Background and Aim

Pseudomonas aeruginosa is an infectious agent of great importance for animals and humans. It causes serious infections that show high resistance to antibiotics. This study investigated the molecular detection of blaOXA-23 gene in antibiotic-resistant P. aeruginosa strains isolated from cows and humans.

Materials and Methods

In total, 120 samples, comprised 60 from cows (30 milk and 30 nasal discharge) and 60 from their owners (30 urine and 30 sputum), were individually collected, cultured, and tested for P. aeruginosa through molecular analysis targeting the blaOXA-23 gene. P. aeruginosa antibiotic-resistant isolates were identified by performing antibiotic susceptibility testing and detecting biofilm formation.

Results

In total, 74.17% positive P. aeruginosa isolates, including 66.67% and 81.67% for cows and humans, respectively. Subsequently, positive cow isolates were detected in 60% of milk samples and 73.33% of nasal discharge samples; while positive human isolates were detected in 76.67% of urine samples and 86.66% of sputum samples. Targeting blaOXA-23 gene, 58.43% of cultured isolates were positive for P. aeruginosa by polymerase chain reaction. Respectively, positive isolates were detected in 66.67% and 45.46% of cow milk and nasal discharges as well as in 60.87% and 61.54% of human urine and sputum. The antibiotic susceptibility test revealed that all isolates were resistant to all applied antibiotics, particularly imipenem. Results of biofilm formation revealed 67.31% total positives, including 51.43% strong, 34.285% moderate, and 14.285% weak reactions. In addition, although values of the total positive cows and humans differed insignificantly, total positives showed insignificant variation between values of milk and nasal discharges of cows as well as between urine and sputum of humans; however, significant differences were identified in the distribution of strong, moderate, and weak positivity of these samples.

Conclusion

Antibiotic overuse contributes extensively to increasing the prevalence of resistant P. aeruginosa isolates carrying the blaOXA-23 gene in both cows and humans. Furthermore, studies in other Iraqi areas are necessary to support our findings. The main limitations include that the number of tested samples is relatively low, and there is a need to use a large number of samples from different sources. Also, the current methods for detection of resistant isolates are still culture-based approaches.

Ceftolozane-Tazobactam Versus Ceftazidime-Avibactam for the Treatment of Infections Caused by Multidrug-Resistant Pseudomonas aeruginosa: a Multicenter Cohort Study

Ceftolozane-tazobactam (C-T) and ceftazidime-avibactam (CAZ-AVI) are two novel antimicrobials that retain activity against resistant Pseudomonas aeruginosa. The comparative effectiveness and safety of C-T versus CAZ-AVI remain unknown. A retrospective, multicenter cohort study was performed in six tertiary centers in Saudi Arabia and included patients who received either C-T or CAZ-AVI for infections due to multidrug-resistant (MDR) P. aeruginosa. Overall in-hospital mortality, 30-day mortality, and clinical cure were the main study outcomes. Safety outcomes were also evaluated. A multivariate analysis using logistic regression was used to determine the independent impact of treatment on the main outcomes of interest. We enrolled 200 patients in the study (100 in each treatment arm). A total of 56% were in the intensive care unit, 48% were mechanically ventilated, and 37% were in septic shock. Approximately 19% of patients had bacteremia. Combination therapy was administered to 41% of the patients. The differences between the C-T and CAZ-AVI groups did not reach statistical significance in the overall in-hospital mortality (44% versus 37%; P = 0.314; OR, 1.34; 95% CI, 0.76 to 2.36), 30-day mortality (27% versus 23%; P = 0.514; OR, 1.24; 95% CI, 0.65 to 2.35), clinical cure (61% versus 66%; P = 0.463; OR, 0.81; 95% CI, 0.43 to 1.49), or acute kidney injury (23% versus 17%; P = 0.289; OR, 1.46; 95% CI, 0.69 to 3.14), even after adjusting for differences between the two groups. C-T and CAZ-AVI did not significantly differ in terms of safety and effectiveness, and they serve as potential options for the treatment of infections caused by MDR P. aeruginosa.

Cefiderocol Treatment for Patients with Multidrug- and Carbapenem-Resistant Pseudomonas aeruginosa Infections in the Compassionate Use Program

Cefiderocol is an option for infections caused by multidrug-resistant Pseudomonas aeruginosa, but its in vitro activity against these isolates and its clinical effectiveness for isolates with MICs of >1 μg/mL is unclear. We investigated the in vitro activity of cefiderocol against P. aeruginosa isolates collected from patients treated with cefiderocol through the compassionate use program and assessed physician-reported clinical response and 28-day all-cause mortality by cefiderocol MIC values. P. aeruginosa isolates underwent susceptibility testing to cefiderocol and comparator agents by using reference broth microdilution. U.S. Food and Drug Administration (FDA; susceptible, ≤1 μg/mL) and Clinical and Laboratory Standards Institute (CLSI; susceptible, ≤4 μg/mL) cefiderocol breakpoints were applied. Additionally, molecular characterization of β-lactamase genes was performed. Clinical response and vital status were reported by treating physicians. Forty-six patients with P. aeruginosa infections were evaluated. Twenty-nine (63%) and 42 (91%) isolates were susceptible to cefiderocol using FDA and CLSI breakpoints, respectively. Thirty-seven (80%) and 32 (70%) isolates were not susceptible to ceftolozane-tazobactam and ceftazidime-avibactam, respectively. The clinical response rate was 69% (20/29) with a cefiderocol MIC of ≤1 μg/mL, 69% (9/13) with a cefiderocol MIC of 2 to 4 μg/mL, and 100% (4/4) with an MIC of ≥8 μg/mL, while day 28 all-cause mortality rates were 23% (6/26; MIC ≤ 1 μg/mL), 33% (4/12; MIC, 2 to 4 μg/mL), and 0% (0/4; MIC ≥8 μg/mL), respectively. Cefiderocol was active in vitro against most P. aeruginosa isolated from patients with limited or no alternative therapies. Patients with cefiderocol MICs of 2 to 4 μg/mL did not have significantly worse outcomes than those with MICs of ≤1 μg/mL.

Molecular characterizations of antibiotic resistance, biofilm formation, and virulence determinants of Pseudomonas aeruginosa isolated from burn wound infection

BACKGROUND

Burn injuries result in disruption of the skin barrier against opportunistic infections. Pseudomonas aeruginosa is one of the main infectious agents colonizing burn wounds and making severe infections. Biofilm production and other virulence factors along with antibiotic resistance limit appropriate treatment options and time.

MATERIALS AND METHODS

Wound samples were collected from hospitalized burn patients. P. aeruginosa isolates and related virulence factors identified by the standard biochemical and molecular methods. Antibiotic resistance patterns were determined by the disc diffusion method and β-lactamase genes were detected by polymerase chain reaction (PCR) assay. To determine the genetic relatedness amongst the isolates, enterobacterial repetitive intergenic consensus (ERIC)-PCR was also performed.

RESULTS

Forty P. aeruginosa isolates were identified. All of these isolates were biofilm producers. Carbapenem resistance was detected in 40% of the isolates, and bla_TEM (37/5%), bla_VIM (30%), and bla_CTX-M (20%) were the most common β-lactamase genes. The highest resistance was detected to cefotaxime, ceftazidime, meropenem, imipenem and piperacillin, and 16 (40%) isolates were resistant to these antibiotics. The minimum inhibitory concentrations (MIC) of colistin was lower than 2 μg/mL and no resistance was observed. Isolates were categorized to 17 MDR, 13 mono-drug resistance, and 10 susceptible isolates. High genetic diversity was also observed among the isolates (28 ERIC types) and most carbapenem-resistant isolates were classified into four main types.

CONCLUSION

Antibiotic resistance, particularly carbapenem resistance was considerable among the P. aeruginosa isolates colonizing burn wounds. Combining carbapenem resistance with biofilm production and virulence factors would result in severe and difficult-to-treat infections.

Suboptimal Concentrations of Ceftazidime/Avibactam (CAZ-AVI) May Select for CAZ-AVI Resistance in Extensively Drug-Resistant Pseudomonas aeruginosa: In Vivo and In Vitro Evidence

This study correlates in vivo findings in a patient with an extensively drug-resistant (XDR) P. aeruginosa infection who developed resistance to ceftazidime-avibactam (CAZ-AVI) with in vitro results of a 7-day hollow-fiber infection model (HFIM) testing the same bacterial strain. The patient was critically ill with ventilator-associated pneumonia caused by XDR P. aeruginosa ST175 with CAZ-AVI MIC of 6 mg/L and was treated with CAZ-AVI in continuous infusion at doses adjusted for renal function. Plasma concentrations of CAZ-AVI were analyzed on days 3, 7, and 10. In the HIFM, the efficacy of different steady-state concentrations (Css) of CAZ-AVI (12, 18, 30 and 48 mg/L) was evaluated. In both models, a correlation was observed between the decreasing plasma levels of CAZ-AVI and the emergence of resistance. In the HIFM, a Css of 30 and 48 mg/L (corresponding to 5× and 8× MIC) had a bactericidal effect without selecting resistant mutants, whereas a Css of 12 and 18 mg/L (corresponding to 2× and 3× MIC) failed to prevent the emergence of resistance. CAZ/AVI resistance development was caused by the selection of a single ampC mutation in both patient and HFIM. Until further data are available, strategies to achieve plasma CAZ-AVI levels at least 4× MIC could be of interest, particularly in severe and high-inoculum infections caused by XDR P. aeruginosa with high CAZ-AVI MICs.

Clinical carbapenem-resistant Klebsiella pneumoniae isolates simultaneously harboring blaNDM-1, blaOXA types and qnrS genes from the Kingdom of Bahrain: Resistance profile and genetic environment

The prevalence of Carbapenem-resistant Klebsiella pneumoniae (CRKP) is currently increasing worldwide, prompting WHO to classify it as an urgent public health threat. CRKP is considered a difficult to treat organism owing to limited therapeutic options. In this study, a total of 24 CRKP clinical isolates were randomly collected from Salmaniya Medical Complex, Bahrain. Bacterial identification and antibiotic susceptibility testing were performed, on MALDI-TOF and VITEK-2 compact, respectively. The isolates were screened for carbapenem resistance markers (bla_NDM,bla_OXA-23,bla_OXA-48 and bla_OXA-51) and plasmid-mediated quinolone resistance genes (qnrA, qnrB, and qnrS) by monoplex PCR. On the other hand, only colistin-resistant isolates (n=12) were screened for MCR-1, MCR-2 and MCR-3 genes by monoplex PCR. Moreover, the Genetic environment of bla_NDM, integrons analysis, and molecular characterization of plasmids was also performed. Antibiotic susceptibility revealed that all the isolates (100%) were resistant to ceftolozane/tazobactam, piperacillin/tazobactam, 96% resistant to ceftazidime, trimethoprim/sulfamethoxazole, 92% resistant to meropenem, gentamicin and cefepime, 88% resistant to ciprofloxacin, imipenem, and 37% resistant to amikacin. Ceftazidime/avibactam showed the least resistance (12%). 75% (n=12/16) were resistant to colistin and 44% (n=7/16) showed intermediate susceptibility to tigecycline. The detection of resistant determinants showed that the majority (95.8%) of CRKP harbored bla_NDM-1, followed by bla_OXA-48 (91.6%) bla_OXA-51 (45.8%), and bla_OXA-23 (41.6%). Sequencing of the bla_NDM amplicons revealed the presence of bla_NDM-1. Alarmingly, 100% of isolates showed the presence of qnrS. These predominant genes were distributed in various combinations wherein the majority were bla_NDM-1 + bla_OXA-51+ qnrS + bla_OXA-48 (n =10, 41.7%), bla_NDM-1 + bla_OXA-23+ qnrS + bla_OXA-48 (n=8, 33.3%), among others. In conclusion, the resistance rate to most antibiotics is very high in our region, including colistin and tigecycline, and the genetic environment of CRKP is complex with the carriage of multiple resistance markers. Resistance to ceftazidime/avibactam is uncommon and hence can be used as a valuable option for empirical therapy. Molecular data on resistance markers and the genetic environment of CRKP is lacking from this geographical region; this would be the first report addressing the subject matter. Surveillance and strict infection control strategies should be reinforced in clinical settings to curb the emergence and spread of such isolates.

Early appropriate diagnostics and treatment of MDR Gram-negative infections

The term difficult-to-treat resistance has been recently coined to identify Gram-negative bacteria exhibiting resistance to all fluoroquinolones and all β-lactam categories, including carbapenems. Such bacteria are posing serious challenges to clinicians trying to identify the best therapeutic option for any given patient. Delayed appropriate therapy has been associated with worse outcomes including increase in length of stay, increase in total in-hospital costs and ∼20% increase in the risk of in-hospital mortality. In addition, time to appropriate antibiotic therapy has been shown to be an independent predictor of 30 day mortality in patients with resistant organisms. Improving and anticipating aetiological diagnosis through optimizing not only the identification of phenotypic resistance to antibiotic classes/agents, but also the identification of specific resistance mechanisms, would have a major impact on reducing the frequency and duration of inappropriate early antibiotic therapy. In light of these considerations, the present paper reviews the increasing need for rapid diagnosis of bacterial infections and efficient laboratory workflows to confirm diagnoses and facilitate prompt de-escalation to targeted therapy, in line with antimicrobial stewardship principles. Rapid diagnostic tests currently available and future perspectives for their use are discussed. Early appropriate diagnostics and treatment of MDR Gram-negative infections require a multidisciplinary approach that includes multiple different diagnostic methods and further consensus of algorithms, protocols and guidelines to select the optimal antibiotic therapy.

Treatment of carbapenem-resistant Pseudomonas aeruginosa infections: a case for cefiderocol

INTRODUCTION

Carbapenem-resistant (CR) Pseudomonas aeruginosa infections constitute a serious clinical threat globally. Patients are often critically ill and/or immunocompromised. Antibiotic options are limited and are currently centered on beta-lactam-beta-lactamase inhibitor (BL-BLI) combinations and the siderophore cephalosporin cefiderocol.

AREAS COVERED

This article reviews the mechanisms of P. aeruginosa resistance and their potential impact on the activity of current treatment options, along with evidence for the clinical efficacy of BL-BLI combinations in P. aeruginosa infections, some of which specifically target infections due to CR organisms. The preclinical and clinical evidence supporting cefiderocol as a treatment option for P. aeruginosa involving infections is also reviewed.

EXPERT OPINION

Cefiderocol is active against most known P. aeruginosa mechanisms mediating carbapenem resistance. It is stable against different serine- and metallo-beta-lactamases, and, due to its iron channel-dependent uptake mechanism, is not impacted by porin channel loss. Furthermore, the periplasmic level of cefiderocol is not affected by upregulated efflux pumps. The potential for on-treatment resistance development currently appears to be low, although more clinical data are required. Information from surveillance programs, real-world compassionate use, and clinical studies demonstrate that cefiderocol is an important treatment option for CR P. aeruginosa infections.

Infectious Diseases Society of America 2022 Guidance on the Treatment of Extended-Spectrum β-lactamase Producing Enterobacterales (ESBL-E), Carbapenem-Resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with Difficult-to-Treat Resistance (DTR-P. aeruginosa)

BACKGROUND

The Infectious Diseases Society of America (IDSA) is committed to providing up-to-date guidance on the treatment of antimicrobial-resistant infections. The initial guidance document on infections caused by extended-spectrum β-lactamase producing Enterobacterales (ESBL-E), carbapenem-resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-P. aeruginosa) was published on 17 September 2020. Over the past year, there have been a number of important publications furthering our understanding of the management of ESBL-E, CRE, and DTR-P. aeruginosa infections, prompting a rereview of the literature and this updated guidance document.

METHODS

A panel of 6 infectious diseases specialists with expertise in managing antimicrobial-resistant infections reviewed, updated, and expanded previously developed questions and recommendations about the treatment of ESBL-E, CRE, and DTR-P. aeruginosa infections. Because of differences in the epidemiology of resistance and availability of specific anti-infectives internationally, this document focuses on the treatment of infections in the United States.

RESULTS

Preferred and alternative treatment recommendations are provided with accompanying rationales, assuming the causative organism has been identified and antibiotic susceptibility results are known. Approaches to empiric treatment, duration of therapy, and other management considerations are also discussed briefly. Recommendations apply for both adult and pediatric populations.

CONCLUSIONS

The field of antimicrobial resistance is highly dynamic. Consultation with an infectious diseases specialist is recommended for the treatment of antimicrobial-resistant infections. This document is current as of 24 October 2021. The most current versions of IDSA documents, including dates of publication, are available at www.idsociety.org/practice-guideline/amr-guidance/.

Therapeutic Strategies for Emerging Multidrug-Resistant Pseudomonas aeruginosa

Multidrug-resistant (MDR) and extensively drug-resistant (XDR) Pseudomonas aeruginosa isolates are frequent causes of serious nosocomial infections that may compromise the selection of antimicrobial therapy. The goal of this review is to summarize recent epidemiologic, microbiologic, and clinical data pertinent to the therapeutic management of patients with infections caused by MDR/XDR-P. aeruginosa. Historically, conventional antipseudomonal β-lactam antibiotics have been used for the empiric treatment of MDR/XDR-P. aeruginosa. Owing to the remarkable capacity of P. aeruginosa to confer resistance via multiple mechanisms, these traditional therapies are often rendered ineffective. To increase the likelihood of administering empiric antipseudomonal therapy with in vitro activity, a second agent from a different antibiotic class is often administered concomitantly with a traditional antipseudomonal β-lactam. However, combination therapy may pose an increased risk of antibiotic toxicity and secondary infection, notably, Clostridioides difficile. Multiple novel agents that demonstrate in vitro activity against MDR-P. aeruginosa (e.g., β-lactam/β-lactamase inhibitor combinations and cefiderocol) have been recently granted US Food and Drug Administration (FDA) approval and are promising additions to the antipseudomonal armamentarium. Even so, comparative clinical data pertaining to these novel agents is sparse, and concerns surrounding the scarcity of antibiotics active against refractory MDR/XDR-P. aeruginosa necessitates continued assessment of alternative therapies. This is particularly important in patients with cystic fibrosis (CF) who may be chronically colonized and suffer from recurrent infections and disease exacerbations due in part to limited efficacious antipseudomonal agents. Bacteriophages represent a promising candidate for combatting recurrent and refractory infections with their ability to target specific host bacteria and circumvent traditional mechanisms of antibiotic resistance seen in MDR/XDR-P. aeruginosa. Future goals for the management of these infections include increased comparator clinical data of novel agents to determine in what scenario certain agents may be preferred over others. Until then, appropriate treatment of these infections requires a thorough evaluation of patient- and infection-specific factors to guide empiric and definitive therapeutic decisions.

Rapid detection of Pseudomonas aeruginosa based on lab-on-a-chip platform using immunomagnetic separation, light scattering, and machine learning

The rapid detection of the pathogenic bacteria in patient samples is crucial to expedient patient care. The proposed approach reports the development of a novel lab-on-a-chip device for the rapid detection of P. aeruginosa based on immunomagnetic separation, optical scattering, and machine learning. The immunomagnetic particles with a diameter of 5 μm were synthesized for isolating P. aeruginosa from the test sample. A microfluidic chip was fabricated, and three optical fibers were embedded for connecting a laser light and two photodetectors. The laser light was pointed towards the channel to pass light through the sample. A pair of photodetectors via optical fibers were arranged symmetrically at 45° to the channel. The photodetectors acquired scattered light from the flowing sample and converted the light to an electrical signal. The sample containing immunomagnetic beads linked with bacteria was injected into the microfluidic chip. The optimized conditions for performing the experiments were characterized for real-time detection of P. aeruginosa. The data acquisition system recorded the real-time light scattering from the test sample. After removing noise from the output waveform, five different time-domain statistical features were extracted from each waveform: standard mean, standard variance, skewness, kurtosis, and coefficient of variation. The pathogens classification was performed by training the discrimination model using extracted features based on machine learning algorithms. The support vector machines (SVM) with a sigmoid function kernel showed superior classification performance with 97.9% accuracy among other classifiers, including k-nearest neighbors (KNN), logistic regression (LR), and naïve Bayes (NB). The method can detect P. aeruginosa specifically and quantitatively with a limit of detection of 10² CFU/mL. The device can classify P. aeruginosa within 10 min with a total assay time of 25 min. The device was used to test its ability to detect pathogen from the serum and sputum specimens spiked with 10⁵ CFU/mL concentration of P. aeruginosa. The results indicate that light scattering combined with machine learning can be used to detect P. aeruginosa. The proposed technique is anticipated to be helpful as a rapid device for diagnosing P. aeruginosa related infections.

Dose optimisation of antibiotics used for meningitis

PURPOSE OF REVIEW

Central nervous system (CNS) infections such as ventriculitis and meningitis are associated with significant morbidity and mortality. In part, this may be due to increased difficulties in achieving a therapeutic antibiotic concentration at the site of infection due to both the pharmacokinetic (PK) changes observed during critical illness and the reduced antibiotic penetration through the blood brain barrier. This paper reviews the pharmacodynamics (PD) and CNS PKs of antibiotics used for Gram-negative bacterial CNS infections to provide clinicians with practical dosing advice.

RECENT FINDINGS

Recent PK studies have shown that currently used intravenous antibiotic dosing regimens may not achieve a therapeutic exposure within the CNS, even for reportedly 'susceptible' bacteria per the current clinical meningitis breakpoints. Limited data exist for new β-lactam antibiotic/β-lactamase inhibitor combinations, which may be required for multidrug resistant infections. Intraventricular antibiotic administration, although not a new concept, has further evidence demonstrating improved patient outcomes compared with intravenous therapy alone, despite the ongoing paucity of PK studies guiding dosing recommendations.

SUMMARY

Clinicians should obtain the bacterial minimum inhibitory concentration when treating patients with CNS Gram-negative bacterial infections and consider the underlying PK/PD principles when prescribing antibiotics. Therapeutic drug monitoring, where available, should be considered to guide dosing. Intraventricular therapy should also be considered for patients with ventricular drains to optimise clinical outcomes.

Novel β-Lactam/β-Lactamase Inhibitor Combinations versus Alternative Antibiotics in Adults with Hospital-Acquired Pneumonia or Ventilator-Associated Pneumonia: An Integrated Analysis of 3 Randomized Controlled Trials

OBJECTIVES

This study assessed the efficacy and safety of novel β-lactam/β-lactamase inhibitor combinations in adult patients with hospital-acquired pneumonia (HAP) or ventilator-associated pneumonia (VAP).

METHODS

PubMed, Web of Science, the Cochrane Library, Ovid MEDLINE, Embase and EBSCO databases were searched for randomized controlled trials (RCTs) published before September 13, 2020. Only RCTs comparing the treatment efficacy of novel β-lactam/β-lactamase inhibitor combinations with other antibiotics for HAP/VAP in adult patients were included in this integrated analysis.

RESULTS

Three RCTs were included, and no significant difference in clinical cure rate of the test of cure (TOC) was observed between the novel β-lactam/β-lactamase inhibitor combination and comparators (odds ratio [OR], 1.01; 95% CI, 0.81-1.27; I² = 35%). The 28-day all-cause mortality was 16.2% and 17.6% for patients receiving the novel β-lactam/β-lactamase inhibitor combination and those receiving comparators, respectively, and no significant difference was noted (OR, 0.90; 95% CI, 0.69-1.16; I² = 11%). Compared with the comparators, the novel β-lactam/β-lactamase inhibitor combination was associated with a similar microbiological response (OR, 1.06; 95% CI, 0.73-1.54; I² = 64%) and a similar risk of AEs (treatment-emergent AEs [TEAEs]: OR, 1.04; 95% CI, 0.83-1.30; I² = 0%; serious AEs: OR, 1.14; 95% CI, 0.79-1.63; I² = 68%; treatment discontinuation for TEAE: OR, 0.90; 95% CI, 0.62-1.31; I² = 11%).

CONCLUSIONS

The clinical and microbiological responses of novel β-lactam/β-lactamase inhibitor combinations in the treatment of HAP/VAP were similar to those of other available antibiotics. These combinations also shared a similar safety profile to that of comparators.

Combined Resistance to Ceftolozane-Tazobactam and Ceftazidime-Avibactam in Extensively Drug-Resistant (XDR) and Multidrug-Resistant (MDR) Pseudomonas aeruginosa: Resistance Predictors and Impact on Clinical Outcomes Besides Implications for Antimicrobial Stewardship Programs

A retrospective case-control study was conducted at Modena University Hospital from December 2017 to January 2019 to identify risk factors and predictors of MDR/XDR Pseudomonas aeruginosa (PA) isolation with resistance to ceftazidime/avibactam (CZA) and ceftolozane/tazobactam (C/T), and of mortality among patients infected/colonized. Among 111 PA isolates from clinical/surveillance samples, 60 (54.1%) were susceptible to both drugs (S-CZA-C/T), while 27 (24.3%) were resistant to both (R-CZA-C/T). Compared to patients colonized/infected with S-CZA-C/T, those with R-C/T + CZA PA had a statistically significantly higher Charlson comorbidity score, greater rate of previous PA colonization, longer time before PA isolation, more frequent presence of CVC, higher exposure to C/T and cephalosporins, longer hospital stay, and higher overall and attributable mortality. In the multivariable analysis, age, prior PA colonization, longer time from admission to PA isolation, diagnosis of urinary tract infection, and exposure to carbapenems were associated with the isolation of a R-C/T + CZA PA strain, while PA-related BSI, a comorbidity score > 7, and ICU stay were significantly associated with attributable mortality. C/T and CZA are important therapeutic resources for hard-to-treat PA-related infections, thus specific antimicrobial stewardship interventions should be prompted in order to avoid the development of this combined resistance, which would jeopardize the chance to treat these infections.

Antimicrobial activity of ceftazidime/avibactam, ceftolozane/tazobactam and comparator agents against Pseudomonas aeruginosa from cystic fibrosis patients

Objectives

To evaluate the antimicrobial susceptibility patterns of Pseudomonas aeruginosa isolates collected from the lower respiratory tract of cystic fibrosis (CF) patients.

Methods

We susceptibility tested 273 contemporary P. aeruginosa isolates from 39 hospitals worldwide (17 countries) by the reference broth microdilution method.

Results

Ceftazidime/avibactam [MIC_50/90, 2/8 mg/L; 96.0% susceptible (S)] was the most active agent, followed by ceftolozane/tazobactam (MIC_50/90, 1/4 mg/L; 90.5% S), ceftazidime (MIC_50/90, 2/>32 mg/L; 80.6% S), piperacillin/tazobactam (MIC_50/90, 4/128 mg/L; 80.2% S) and tobramycin (MIC_50/90, 2/>16 mg/L; 76.6% S). Ceftazidime/avibactam retained activity against P. aeruginosa isolates non-susceptible to meropenem (86.5% S to ceftazidime/avibactam), piperacillin/tazobactam (85.2% S to ceftazidime/avibactam) or ceftazidime (79.2% S to ceftazidime/avibactam). MDR phenotype was observed among 36.3% of isolates, and 88.9% and 73.7% of MDR isolates were susceptible to ceftazidime/avibactam and ceftolozane/tazobactam, respectively. Against isolates non-susceptible to meropenem, piperacillin/tazobactam and ceftazidime, susceptibility rates were 78.9% for ceftazidime/avibactam and 47.4% for ceftolozane/tazobactam. Ceftazidime/avibactam was active against 65.4% of ceftolozane/tazobactam-non-susceptible isolates and ceftolozane/tazobactam was active against 18.2% of ceftazidime/avibactam-non-susceptible isolates.

Conclusions

Ceftazidime/avibactam and ceftolozane/tazobactam exhibited potent and broad-spectrum activity against P. aeruginosa isolated from CF patients worldwide, but higher susceptibility rates for ceftazidime/avibactam compared with ceftolozane/tazobactam were observed among the resistant subsets. Ceftazidime/avibactam and ceftolozane/tazobactam represent valuable options to treat CF pulmonary exacerbations caused by P. aeruginosa.

Pharmacokinetic/Pharmacodynamic Adequacy of Novel β-Lactam/β-Lactamase Inhibitors against Gram-Negative Bacterial in Critically Ill Patients

The optimal regimens of novel β-lactam/β-lactamase inhibitors (BLBLIs), ceftazidime/avibactam, ceftolozane/tazobactam, and meropenem/vaborbactam, are not well defined in critically ill patients. This study was conducted to identify optimal regimens of BLBLIs in these patients. A Monte Carlo simulation was performed using the published data to calculate the joint probability of target attainment (PTA) and the cumulative fraction of response (CFR). For the target of β-lactam of 100% time with free drug concentration remains above minimal inhibitory concentrations, the PTAs of BLBLIs standard regimens were <90% at a clinical breakpoint for Enterobacteriaceae and Pseudomonas aeruginosa. For ceftazidime/avibactam, 2000 mg/500 mg/8 h by 4 h infusion achieved >90% CFR for Escherichia coli; even for 4000 mg/1000 mg/6 h by continuous infusion, CFR for Klebsiella pneumoniae was <90%; the CFRs of 3500 mg/875 mg/6 h by 4 h infusion and 4000 mg/1000 mg/8 h by continuous infusion were appropriate for Pseudomonas aeruginosa. For ceftolozane/tazobactam, the CFR of standard regimen was >90% for Escherichia coli, however, 2000 mg/1000 mg/6 h by continuous infusion achieved <90% CFRs for Klebsiella pneumoniae and Pseudomonas aeruginosa. For meropenem/vaborbactam, standard regimen achieved optimal attainments for Escherichia coli and Klebsiella pneumoniae; 2000 mg/2000 mg/6 h by 5 h infusion, 2500 mg /2500 mg/6 h by 4 h infusion, 3000 mg/3000 mg/6 h by 3 h infusion and 4000 mg/4000 mg/8 h by 5 h infusion achieved >90% CFRs for Pseudomonas aeruginosa. The CFRs of three BLBLIs were similar for Escherichia coli, but meropenem/vaborbactam were superior for Klebsiella pneumoniae and Pseudomonas aeruginosa.

An Update on Eight "New" Antibiotics against Multidrug-Resistant Gram-Negative Bacteria

Infections in the ICU are often caused by Gram-negative bacteria. When these microorganisms are resistant to third-generation cephalosporines (due to extended-spectrum (ESBL) or AmpC beta-lactamases) or to carbapenems (for example carbapenem producing Enterobacteriales (CPE)), the treatment options become limited. In the last six years, fortunately, there have been new antibiotics approved by the U.S. Food and Drug Administration (FDA) with predominant activities against Gram-negative bacteria. We aimed to review these antibiotics: plazomicin, eravacycline, temocillin, cefiderocol, ceftazidime/avibactam, ceftolozane/tazobactam, meropenem/vaborbactam, and imipenem/relebactam. Temocillin is an antibiotic that was only approved in Belgium and the UK several decades ago. We reviewed the in vitro activities of these new antibiotics, especially against ESBL and CPE microorganisms, potential side effects, and clinical studies in complicated urinary tract infections (cUTI), intra-abdominal infections (cIAI), and hospital-acquired pneumonia/ventilator-associatedpneumonia (HAP/VAP). All of these new antibiotics are active against ESBL, and almost all of them are active against CPE caused by KPC beta-lactamase, but only some of them are active against CPE due to MBL or OXA beta-lactamases. At present, all of these new antibiotics are approved by the U.S. Food and Drug Administration for cUTI (except eravacycline) and most of them for cIAI (eravacycline, ceftazidime/avibactam, ceftolozane/tazobactam, and imipenem/relebactam) and for HAP or VAP (cefiderocol, ceftazidime/avibactam, ceftolozane/tazobactam, and imipenem/relebactam).

Interplay between ESKAPE Pathogens and Immunity in Skin Infections: An Overview of the Major Determinants of Virulence and Antibiotic Resistance

The skin is the largest organ in the human body, acting as a physical and immunological barrier against pathogenic microorganisms. The cutaneous lesions constitute a gateway for microbial contamination that can lead to chronic wounds and other invasive infections. Chronic wounds are considered as serious public health problems due the related social, psychological and economic consequences. The group of bacteria known as ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter sp.) are among the most prevalent bacteria in cutaneous infections. These pathogens have a high level of incidence in hospital environments and several strains present phenotypes of multidrug resistance. In this review, we discuss some important aspects of skin immunology and the involvement of ESKAPE in wound infections. First, we introduce some fundamental aspects of skin physiology and immunology related to cutaneous infections. Following this, the major virulence factors involved in colonization and tissue damage are highlighted, as well as the most frequently detected antimicrobial resistance genes. ESKAPE pathogens express several virulence determinants that overcome the skin's physical and immunological barriers, enabling them to cause severe wound infections. The high ability these bacteria to acquire resistance is alarming, particularly in the hospital settings where immunocompromised individuals are exposed to these pathogens. Knowledge about the virulence and resistance markers of these species is important in order to develop new strategies to detect and treat their associated infections.