Meropenem/Vaborbactam Plus Aztreonam as a Possible Treatment Strategy for Bloodstream Infections Caused by Ceftazidime/Avibactam-Resistant Klebsiella pneumoniae: A Retrospective Case Series and Literature Review

Evolving resistance landscape in gram-negative pathogens: An update on β-lactam and β-lactam-inhibitor treatment combinations for carbapenem-resistant organisms

Antibiotic resistance has become a global threat as it is continuously growing due to the evolution of β-lactamases diminishing the activity of classic β-lactam (BL) antibiotics. Recent antibiotic discovery and development efforts have led to the availability of β-lactamase inhibitors (BLIs) with activity against extended-spectrum β-lactamases as well as Klebsiella pneumoniae carbapenemase (KPC)-producing carbapenem-resistant organisms (CRO). Nevertheless, there is still a lack of drugs that target metallo-β-lactamases (MBL), which hydrolyze carbapenems efficiently, and oxacillinases (OXA) often present in carbapenem-resistant Acinetobacter baumannii. This review aims to provide a snapshot of microbiology, pharmacology, and clinical data for currently available BL/BLI treatment options as well as agents in late stage development for CRO harboring various β-lactamases including MBL and OXA-enzymes.

Meropenem/Vaborbactam: β-Lactam/β-Lactamase Inhibitor Combination, the Future in Eradicating Multidrug Resistance

Due to the fact that there is a steadily increasing trend in the area of antimicrobial resistance in microorganisms, there is a need to look for new treatment alternatives. One of them is the search for new β-lactamase inhibitors and combining them with β-lactam antibiotics, with the aim of increasing the low-dose efficacy, as well as lowering the resistance potential of bacterial strains. This review presents the positive effect of meropenem in combination with a vaborbactam (MER-VAB). This latest antibiotic-inhibitor combination has found particular use in the treatment of infections with the etiology of carbapenem-resistant Enterobacterales (CRE), Gram-negative bacteria, with a high degree of resistance to available antimicrobial drugs.

Ceftazidime/Avibactam and Meropenem/Vaborbactam for the Management of Enterobacterales Infections: A Narrative Review, Clinical Considerations, and Expert Opinion

This comprehensive review examines the unique attributes, distinctions, and clinical implications of ceftazidime-avibactam (CAZ-AVI) and meropenem-vaborbactam (MEM-VAB) against difficult-to-treat Enterobacterales infections. Our manuscript explores these antibiotics' pharmacokinetic and pharmacodynamic properties, antimicrobial activities, in vitro susceptibility testing, and clinical data. Moreover, it includes a meticulous examination of comparative clinical and microbiological studies, assessed and presented to provide clarity in making informed treatment choices for clinicians. Finally, we propose an expert opinion from a microbiological and a clinical point of view about their use in appropriate clinical settings. This is the first review aiming to provide healthcare professionals with valuable insights for making informed treatment decisions when combating carbapenem-resistant pathogens.

Novel Antimicrobial Agents for Gram-Negative Pathogens

Gram-negative bacterial resistance to antimicrobials has had an exponential increase at a global level during the last decades and represent an everyday challenge, especially for the hospital practice of our era. Concerted efforts from the researchers and the industry have recently provided several novel promising antimicrobials, resilient to various bacterial resistance mechanisms. There are new antimicrobials that became commercially available during the last five years, namely, cefiderocol, imipenem-cilastatin-relebactam, eravacycline, omadacycline, and plazomicin. Furthermore, other agents are in advanced development, having reached phase 3 clinical trials, namely, aztreonam-avibactam, cefepime-enmetazobactam, cefepime-taniborbactam, cefepime-zidebactam, sulopenem, tebipenem, and benapenem. In this present review, we critically discuss the characteristics of the above-mentioned antimicrobials, their pharmacokinetic/pharmacodynamic properties and the current clinical data.

Impact of a Pro-Active Infectious Disease Consultation on the Management of a Multidrug-Resistant Organisms Outbreak in a COVID-19 Hospital: A Three-Months Quasi-Experimental Study

Background: Antimicrobial and diagnostic stewardship (AS/DS) principles are crucial for the management of multidrug-resistant organisms (MDROs) infections. We evaluated the impact of a pro-active Infectious Disease (ID) consultation on the mortality risk of patients during an MDROs outbreak in a COVID-19 hospital. Methods: A quasi-experimental study was performed in a dedicated COVID-19 hospital, including patients with suspected/confirmed infection and/or colonization by MDROs, which were managed as follows: (i) according to the standard of care during the pre-phase and (ii) in collaboration with a dedicated ID team performing a pro-active bedside evaluation every 48–72 h in the post-phase. Results: Overall, 112 patients were included (pre-phase = 89 and post-phase = 45). The AS interventions included the following: therapy optimization (33%), de-escalation to narrow the spectrum (24%) or to lessen toxic drugs (20%), and discontinuation of antimicrobials (64%). DS included the request of additional microbiologic tests (82%) and instrumental exams (16%). With the Cox model, after adjusting for age, sex, COVID-19 severity, infection source, etiological agents, and post-phase attendance, only age predicted an increased risk of mortality, while attendance in the post-phase resulted in a decreased risk of mortality. Conclusions: Implementation of AS and DS intervention through a pro-active ID consultation may reduce the risk of 28-day mortality of COVID-19 patients with MDROs infections.

What to Do with the New Antibiotics?

Multidrug-resistant Gram-negative bacteria-related infections have become a real public health problem and have exposed the risk of a therapeutic impasse. In recent years, many new antibiotics have been introduced to enrich the therapeutic armamentarium. Among these new molecules, some are mainly of interest for the treatment of the multidrug-resistant infections associated with Pseudomonas aeruginosa (ceftolozane/tazobactam and imipenem/relebactam); others are for carbapenem-resistant infections associated with Enterobacterales (ceftazidime/avibactam, meropenem/vaborbactam); and finally, there are others that are effective on the majority of multidrug-resistant Gram-negative bacilli (cefiderocol). Most international guidelines recommend these new antibiotics in the treatment of microbiologically documented infections. However, given the significant morbidity and mortality of these infections, particularly in the case of inadequate therapy, it is important to consider the place of these antibiotics in probabilistic treatment. Knowledge of the risk factors for multidrug-resistant Gram-negative bacilli (local ecology, prior colonization, failure of prior antibiotic therapy, and source of infection) seems necessary in order to optimize antibiotic prescriptions. In this review, we will assess these different antibiotics according to the epidemiological data.

Carbapenem-Resistant Klebsiella pneumoniae: Virulence Factors, Molecular Epidemiology and Latest Updates in Treatment Options

Klebsiella pneumoniae is a Gram-negative opportunistic pathogen responsible for a variety of community and hospital infections. Infections caused by carbapenem-resistant K. pneumoniae (CRKP) constitute a major threat for public health and are strongly associated with high rates of mortality, especially in immunocompromised and critically ill patients. Adhesive fimbriae, capsule, lipopolysaccharide (LPS), and siderophores or iron carriers constitute the main virulence factors which contribute to the pathogenicity of K. pneumoniae. Colistin and tigecycline constitute some of the last resorts for the treatment of CRKP infections. Carbapenemase production, especially K. pneumoniae carbapenemase (KPC) and metallo-β-lactamase (MBL), constitutes the basic molecular mechanism of CRKP emergence. Knowledge of the mechanism of CRKP appearance is crucial, as it can determine the selection of the most suitable antimicrobial agent among those most recently launched. Plazomicin, eravacycline, cefiderocol, temocillin, ceftolozane-tazobactam, imipenem-cilastatin/relebactam, meropenem-vaborbactam, ceftazidime-avibactam and aztreonam-avibactam constitute potent alternatives for treating CRKP infections. The aim of the current review is to highlight the virulence factors and molecular pathogenesis of CRKP and provide recent updates on the molecular epidemiology and antimicrobial treatment options.

Efficacy and Safety of Colistin versus Tigecycline for Multi-Drug-Resistant and Extensively Drug-Resistant Gram-Negative Pathogens-A Meta-Analysis

Background: We intended to compare the efficacy and safety outcomes of colistin versus tigecycline as monotherapy or combination therapy against multi-drug resistant (MDR) and extensively drug-resistant (XDR) pathogens. Methods: A search was conducted in PubMed, Cochrane CENTRAL, EMBASE, and in the grey literature (i.e., ClinicalTrials.gov and Google Scholar) up to May 2021. Outcomes were clinical response, mortality, infection recurrence, and renal and hepatic toxicity. We pooled odd ratios (OR) using heterogeneity-guided random or fixed models at a statistical significance of p < 0.05. Results: Fourteen observational studies involving 1163 MDR/XDR pathogens, receiving tigecycline versus colistin monotherapy or combination, were included. Base-case analyses revealed insignificant differences in the clinical response, reinfection, and hepatic impairment. The 30-day mortality was significantly relatively reduced with tigecycline monotherapy (OR = 0.35, 95% CI 0.16−0.75, p = 0.007). The colistin monotherapy significantly relatively reduced in-hospital mortality (OR = 2.27, 95%CI 1.24−4.16, p = 0.008). Renal impairment rates were lower with tigecycline monotherapy or in combination, and were lower with monotherapy versus colistin-tigecycline combination. Low-risk of bias and moderate/high evidence quality were associated with all studies. Conclusions: Within the limitations of this study, it can be concluded that there were no statistically significant differences in main efficacy outcomes between colistin and tigecycline monotherapies or combinations against MDR/XDR infections, except for lower rates of 30-day mortality with tigecycline and in-hospital mortality with colistin. Tigecycline was associated with favourable renal toxicity outcomes.

Prompt and Appropriate Antimicrobial Therapy Improves Outcomes of NDM-Producing and KPC-Producing Klebsiella pneumoniae Bloodstream Infections in Patients Hospitalized for COVID-19: A Comparative Retrospective Case-Series

Secondary bloodstream infections (BSIs) caused by KPC- and NDM-producing Klebsiella pneumoniae (K.p.) during the course of COVID-19 infections lead to significant mortality. Herein, a comparative retrospective case series of KPC- or NDM-K.p. BSIs occurring in COVID-19 subjects treated with Ceftazidime/Avibactam (CAZ/AVI) for KPC-K.p., or CAZ/AVI+ Aztreonam (ATM) for NDM-K.p is reported. All patients hospitalized for COVID-19 in two Italian hospitals with a BSI between March and September 2021 were included. The main outcome was 14-day mortality. Overall, 44 patients were included: 23 with KPC-K.p. and 21 with NDM-K.p. BSIs. The median (q1–q3) age was 67 (57–75) years, and 32 (72%) were males. The two groups were similar in terms of baseline comorbidity, or severity of COVID-19. Notably, 14-day mortality of KPC-K.p. BSIs and NDM-K.p. BSIs (26% vs. 38%, p = 0.521) and 28-day mortality (35% vs. 48%, p = 0.541) were similar. A Cox regression model of delayed initiation of an appropriate antibiotic therapy after the onset of symptoms independently predicted mortality: initiation between 24 and 72 h (aHR = 12.03; 95% CI = 1.10–130, p = 0.041); and initiation after 72h (aHR = 36.9, 95% CI = 3.22–424, p = 0.004). Moreover, a trend towards an increased risk of mortality was observed for polymicrobial infections (aHR = 3.73, 95% CI = 0.87–15.8, p = 0.074), while a protective effect was observed for a beta-lactam loading dose at the start of treatment (aHR = 0.16, 95% CI = 0.02–1.10, p = 0.064). The high mortality of KPC and NDM-K.p. BSIs in COVID-19 patients may be reduced by an early and appropriate antibiotic therapy. Further efforts should be made to develop antimicrobial stewardship and infection control programs in COVID-19 wards.

Detecting KPC-2 and NDM-1 Coexpression in Klebsiella pneumoniae Complex from Human and Animal Hosts in South America

Reports of Gram-negative bacteria harboring multiple carbapenemase genes have increased in South America, leading to an urgent need for appropriate microbiological diagnosis. We evaluated phenotypic methods for detecting Klebsiella pneumoniae carbapenemase 2 (KPC-2) and New Delhi metallo-β-lactamase-1 (NDM-1) coexpression in members of the K. pneumoniae complex (i.e., K. pneumoniae, K. quasipneumoniae, and K. variicola) isolated from human and animal hosts, based on inhibition of ceftazidime-avibactam (CZA) and aztreonam (ATM) by dipicolinic acid (DPA), EDTA, or avibactam (AVI). While the presence of blaKPC-2 and blaNDM-1 genes was confirmed by whole-genome sequencing, PCR, and/or GeneXpert, coexpression was successfully detected based on the following: (i) a ≥5-mm increase in the zone diameter of ATM (30 µg) disks plus AVI (4 or 20 µg) and ≥4-mm and ≥10-mm increases in the zone diameters for "CZA 50" (30 µg ceftazidime [CAZ] and 20 µg AVI) and "CZA 14" (10 µg CAZ and 4 µg AVI) disks, respectively, when we added DPA (1 mg/disk) or EDTA (5 mM) in a combined disk test (CDT); (ii) a positive ghost zone (synergism) between ATM (30 µg) and CZA 50 disks and between CZA 50 and DPA (1 mg) disks, using the double-disk synergy test (DDST) at a disk-disk distance of 2.5 cm; (iii) ≥3-fold MIC reductions of ATM and CZA in the presence of AVI (4 µg/mL), DPA (500 µg/mL), or EDTA (320 µg/mL); and (iv) immunochromatography. Although our results demonstrated that inhibition by AVI, DPA, and EDTA may provide simple and inexpensive methods for the presumptive detection of coexpression of KPC-2 and NDM-1 in members of the K. pneumoniae complex, additional studies are necessary to confirm the accuracy of these methodologies by testing other Gram-negative bacterial species and other KPC and NDM variants coexpressed by WHO critical priority pathogens detected worldwide. IMPORTANCE Alerts regarding the emergence and increase of combinations of carbapenemases in Enterobacterales in Latin America and the Caribbean have recently been issued by PAHO and WHO, emphasizing the importance of appropriate microbiological diagnosis and the effective and articulated implementation of infection prevention and control programs. In this study, we evaluated methods based on inhibition of ceftazidime (CAZ), ceftazidime-avibactam (CZA), and aztreonam (ATM) by dipicolinic acid (DPA), EDTA, and avibactam (AVI) inhibitors for the identification of KPC-2- and NDM-1-coexpression in members of the K. pneumoniae complex recovered from human and animal hosts. Our results demonstrate that inhibition by AVI, DPA, and EDTA may provide simple and inexpensive methods for the presumptive detection of coexpression of KPC-2 and NDM-1 in members of the K. pneumoniae complex.