In Vitro Activity of Ceftolozane-Tazobactam against Multidrug-Resistant Nonfermenting Gram-Negative Bacilli Isolated from Patients with Cystic Fibrosis

Global mapping of antibiotic resistance rates among clinical isolates of Stenotrophomonas maltophilia: a systematic review and meta-analysis

INTRODUCTION

Infections caused by Stenotrophomonas maltophilia are clinically important due to its intrinsic resistance to a broad range of antibiotics. Therefore, selecting the most appropriate antibiotic to treat S. maltophilia infection is a major challenge.

AIM

The current meta-analysis aimed to investigate the global prevalence of antibiotic resistance among S. maltophilia isolates to the develop more effective therapeutic strategies.

METHOD

A systematic literature search was performed using the appropriate search syntax after searching Pubmed, Embase, Web of Science and Scopus databases (May 2023). Statistical analysis was performed using Pooled and the random effects model in R and the metafor package. A total of 11,438 articles were retrieved. After a thorough evaluation, 289 studies were finally eligible for inclusion in this systematic review and meta-analysis.

RESULT

Present analysis indicated that the highest incidences of resistance were associated with doripenem (97%), cefoxitin (96%), imipenem and cefuroxime (95%), ampicillin (94%), ceftriaxone (92%), aztreonam (91%) and meropenem (90%) which resistance to Carbapenems is intrinsic. The lowest resistance rates were documented for minocycline (3%), cefiderocol (4%). The global resistance rate to TMP-SMX remained constant in two periods before and after 2010 (14.4% vs. 14.6%). A significant increase in resistance to tigecycline and ceftolozane/tazobactam was observed before and after 2010.

CONCLUSIONS

Minocycline and cefiderocol can be considered the preferred treatment options due to low resistance rates, although regional differences in resistance rates to other antibiotics should be considered. The low global prevalence of resistance to TMP-SMX as a first-line treatment for S. maltophilia suggests that it remains an effective treatment option.

In Vitro Susceptibility of Achromobacter Species Isolated from Cystic Fibrosis Patients: a 6-Year Survey

We conducted in vitro antimicrobial susceptibility testing of 267 Achromobacter isolates for 16 antibiotics from 2017 to 2022. The highest susceptibility was found for piperacillin-tazobactam (70%) and ceftazidime-avibactam (62%). Between 30% and 49% of strains were susceptible to tigecycline, ceftazidime, and meropenem. We applied species-specific Achromobacter xylosoxidans breakpoints for piperacillin-tazobactam, meropenem, and trimethoprim-sulfamethoxazole and EUCAST pharmacokinetic/pharmacodynamic (PK/PD) breakpoints for the others. A. xylosoxidans was the most frequently isolated species, followed by Achromobacter insuavis and Achromobacter ruhlandii.

Antimicrobial resistance of Pseudomonas aeruginosa in a cystic fibrosis population after introduction of a novel cephalosporin/β-lactamase inhibitor combination

Ceftolozane-tazobactam is a new β-lactam/β-lactamase inhibitor combination approved by the U.S. Food and Drug Administration in 2019 for the treatment of hospital-acquired and ventilator-associated pneumonia. The combination is a particularly potent inhibitor of penicillin-binding proteins with higher affinity than other β-lactam agents. Persons with cystic fibrosis (pwCF) often harbour resistant Gram-negative bacteria in the airways and need antibiotics to prevent declining lung function. To test whether the introduction of ceftolozane-tazobactam in the period 2015-2020 led to a bacterial population level increase in cephalosporin resistance in a Danish CF population. In vitro, activity of ceftolozane-tazobactam was evaluated by susceptibility testing of clinical Pseudomonas aeruginosa isolated from pwCF from January 1, 2015, to June 1, 2020. Six thousand three hundred thirty two isolates collected from 210 adult pwCF were included. Thirty pwCF were treated with ceftolozane-tazobactam at least once. Ceftolozane-tazobactam exposure did not increase cephalosporin resistance on an individual or population level. However, resistance to ceftolozane-tazobactam was recorded despite no prior exposure in four pwCF. Compared to ceftazidime, ceftolozane-tazobactam had a better in vitro activity on P. aeruginosa. The percentage of non-mucoid P. aeruginosa isolates susceptible to ceftolozane-tazobactam were higher or equal to 5 other β-lactams. Ceftolozane-tazobactam expands the armamentaria against P. aeruginosa with acceptable levels for a selection of drug resistance.

Antimicrobial susceptibility of ceftolozane-tazobactam against multidrug-resistant Pseudomonas aeruginosa isolates from Melbourne, Australia

We collected 163 clinical Pseudomonas aeruginosa isolates at a tertiary hospital specialising in adult cystic fibrosis (CF) and lung transplantation (LTx) in Melbourne, Australia, to explore the activity of ceftolozane-tazobactam (C/T) in populations at high-risk for antimicrobial resistance. Of these, 144 (88.3%) were collected from sputum, and 19 (11.7%) from bronchoalveolar lavage. Most (85.3%) were derived from patients with cystic fibrosis and included a subset of patients that had undergone LTx. These isolates were tested against 11 antibiotics, including C/T, using Sensititre plates for broth microdilution (BMD) testing. Sixty (36.8%) isolates were classified as multidrug resistant (MDR) and 32 (19.6%) were extensively drug resistant (XDR). Overall, 133/163 (81.6%) isolates were susceptible to C/T. For MDR and XDR isolates, 88.3% and 28.1% were C/T susceptible, respectively. Among the non-MDR/XDR isolates, 100% remained susceptible to C/T. Comparisons of C/T susceptibility were made using BioMérieux Etests and Liofilchem MIC test strips (MTS). Categorical agreement to BMD was >93% for both test strips, but essential agreement to BMD was slightly higher with Etest (89.0%) compared to Liofilchem (74.8%). In conclusion, C/T retained activity against most MDR and over a quarter of XDR P. aeruginosa isolates from complex patients with CF and post-LTx.

Global prevalence and antibiotic resistance in clinical isolates of Stenotrophomonas maltophilia: a systematic review and meta-analysis

Introduction

Stenotrophomonas maltophilia is a little-known environmental opportunistic bacterium that can cause broad-spectrum infections. Despite the importance of this bacterium as an emerging drug-resistant opportunistic pathogen, a comprehensive analysis of its prevalence and resistance to antibiotics has not yet been conducted.

Methods

A systematic search was performed using four electronic databases (MEDLINE via PubMed, Embase, Scopus, and Web of Science) up to October 2019. Out of 6,770 records, 179 were documented in the current meta-analysis according to our inclusion and exclusion criteria, and 95 studies were enrolled in the meta-analysis.

Results

Present analysis revealed that the global pooled prevalence of S. maltophilia was 5.3 % [95% CI, 4.1-6.7%], with a higher prevalence in the Western Pacific Region [10.5%; 95% CI, 5.7-18.6%] and a lower prevalence in the American regions [4.3%; 95% CI, 3.2-5.7%]. Based on our meta-analysis, the highest antibiotic resistance rate was against cefuroxime [99.1%; 95% CI, 97.3-99.7%], while the lowest resistance was correlated with minocycline [4·8%; 95% CI, 2.6-8.8%].

Discussion

The results of this study indicated that the prevalence of S. maltophilia infections has been increasing over time. A comparison of the antibiotic resistance of S. maltophilia before and after 2010 suggested there was an increasing trend in the resistance to some antibiotics, such as tigecycline and ticarcillin-clavulanic acid. However, trimethoprim-sulfamethoxazole is still considered an effective antibiotic for treating S. maltophilia infections.

Efficacy of Combination Therapies for the Treatment of Multi-Drug Resistant Gram-Negative Bacterial Infections Based on Meta-Analyses

There is increasing evidence regarding the optimal therapeutic strategies for multidrug-resistant (MDR) bacteria that cause common infections and are resistant to existing antibiotics. Combination therapies, such as β-lactam combined with β-lactamase inhibitors or combination antibiotics, is a therapeutic strategy to overcome MDR bacteria. In recent years, the therapeutic options have expanded as certain combination drugs have been approved in more countries. However, only a handful of guidelines support these options, and the recommendations are based on low-quality evidence. This review describes the significance and efficacy of combination therapy as a therapeutic strategy against Gram-negative MDR pathogens based on previously reported meta-analyses.

The Role of Colistin in the Era of New β-Lactam/β-Lactamase Inhibitor Combinations

With the current crisis related to the emergence of carbapenem-resistant Gram-negative bacteria (CR-GNB), classical treatment approaches with so-called “old-fashion antibiotics” are generally unsatisfactory. Newly approved β-lactam/β-lactamase inhibitors (BLBLIs) should be considered as the first-line treatment options for carbapenem-resistant Enterobacterales (CRE) and carbapenem-resistant Pseudomonas aeruginosa (CRPA) infections. However, colistin can be prescribed for uncomplicated lower urinary tract infections caused by CR-GNB by relying on its pharmacokinetic and pharmacodynamic properties. Similarly, colistin can still be regarded as an alternative therapy for infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) until new and effective agents are approved. Using colistin in combination regimens (i.e., including at least two in vitro active agents) can be considered in CRAB infections, and CRE infections with high risk of mortality. In conclusion, new BLBLIs have largely replaced colistin for the treatment of CR-GNB infections. Nevertheless, colistin may be needed for the treatment of CRAB infections and in the setting where the new BLBLIs are currently unavailable. In addition, with the advent of rapid diagnostic methods and novel antimicrobials, the application of personalized medicine has gained significant importance in the treatment of CRE infections.

Antimicrobial Treatment Strategies for Stenotrophomonas maltophilia: A Focus on Novel Therapies

Stenotrophomonas maltophilia is an urgent global threat due to its increasing incidence and intrinsic antibiotic resistance. Antibiotic development has focused on carbapenem-resistant Enterobacteriaceae, Pseudomonas, and Acinetobacter, with approved antibiotics in recent years having limited activity for Stenotrophomonas. Accordingly, novel treatment strategies for Stenotrophomonas are desperately needed. We conducted a systemic literature review and offer recommendations based on current evidence for a treatment strategy of Stenotrophomonas infection.

Multicenter surveillance of antimicrobial susceptibilities and resistance mechanisms among Enterobacterales species and non-fermenting Gram-negative bacteria from different infection sources in Taiwan from 2016 to 2018

OBJECTIVES

To explore the in vitro antimicrobial susceptibility among clinically important Gram-negative bacteria (GNB) in Taiwan.

METHODS

From 2016 through 2018, a total of 5458 GNB isolates, including Escherichia coli (n = 1545), Klebsiella pneumoniae (n = 1255), Enterobacter species (n = 259), Pseudomonas aeruginosa (n = 1127), Acinetobacter baumannii complex (n = 368), and Stenotrophomonas maltophilia (n = 179), were collected. The susceptibility results were summarized by the breakpoints of minimum inhibitory concentration (MIC) of CLSI 2020, EUCAST 2020 (for colistin), or published articles (for ceftolozane/tazobactam). The resistance genes among multidrug-resistant (MDR) or extensively drug-resistant (XDR)-GNB were investigated by multiplex PCR.

RESULTS

Significantly higher rates of non-susceptibility (NS) to ertapenem and carbapenemase production, predominantly KPC and OXA-48-like beta-lactamase, were observed in Enterobacterales isolates causing respiratory tract infection than those causing complicated urinary tract or intra-abdominal infection (12.7%/3.44% vs. 5.7%/0.76% or 7.7%/0.97%, respectively). Isolates of Enterobacter species showed higher rates of phenotypic extended-spectrum β-lactamase and NS to ertapenem than E. coli or K. pneumoniae isolates. Although moderate activity (54-83%) was observed against most potential AmpC-producing Enterobacterales isolates, ceftolozane/tazobactam exhibited poor in vitro (44.7-47.4%) activity against phenotypic AmpC Enterobacter cloacae isolates. Additionally, 251 (22.3%) P. aeruginosa isolates exhibited the carbapenem-NS phenotype, and their MDR and XDR rate was 63.3% and 33.5%, respectively. Fifteen (75%) of twenty Burkholderia cenocepacia complex isolates were inhibited by ceftolozane/tazobactam at MICs of ≤4 μg/mL.

CONCLUSIONS

With the increase in antibiotic resistance in Taiwan, it is imperative to periodically monitor the susceptibility profiles of clinically important GNB.

Achromobacter Infections and Treatment Options

Achromobacter is a genus of nonfermenting Gram-negative bacteria under order Burkholderiales Although primarily isolated from respiratory tract of people with cystic fibrosis, Achromobacter spp. can cause a broad range of infections in hosts with other underlying conditions. Their rare occurrence and ever-changing taxonomy hinder defining their clinical features, risk factors for acquisition and adverse outcomes, and optimal treatment. Achromobacter spp. are intrinsically resistant to several antibiotics (e.g., most cephalosporins, aztreonam, and aminoglycosides), and are increasingly acquiring resistance to carbapenems. Carbapenem resistance is mainly caused by multidrug efflux pumps and metallo-β-lactamases, which are not expected to be overcome by new β-lactamase inhibitors. Among the other new antibiotics, cefiderocol, and eravacycline were used as salvage therapy for a limited number of patients with Achromobacter infections. In this article, we aim to give an overview of the antimicrobial resistance in Achromobacter species, highlighting the possible place of new antibiotics in their treatment.

Use of continuous infusion ceftolozane-tazobactam with therapeutic drug monitoring in a patient with cystic fibrosis

PURPOSE

The safe and effective use of ceftolozane-tazobactam delivered via continuous infusion in a cystic fibrosis (CF) patient with reduced body weight and presumed augmented renal clearance is reported.

SUMMARY

A 30-year-old woman with CF was admitted for acute pulmonary exacerbations with positive respiratory cultures for Pseudomonas aeruginosa and extended-spectrum β-lactamase-producing Escherichia coli. Susceptibility testing confirmed multidrug resistance, and the patient was transitioned to ceftolozane-tazobactam for definitive therapy. A novel strategy of administering ceftolozane-tazobactam 6 g by continuous i.v. infusion over 24 hours was initiated during hospitalization and continued at discharge for a total of 10 days. Therapeutic drug monitoring over the first 36 hours of the continuous infusion confirmed adequate exposure. The patient had clinical resolution with return to baseline of pulmonary function tests and no noted adverse drug events.

CONCLUSION

A continuous infusion regimen of ceftolozane-tazobactam was successfully used in a CF patient with augmented renal clearance.

Defining the Role of Novel β-Lactam Agents That Target Carbapenem-Resistant Gram-Negative Organisms

With the current carbapenem-resistant organism crisis, conventional approaches to optimizing pharmacokinetic-pharmacodynamic parameters are frequently inadequate, and traditional salvage agents (eg, colistin, tigecycline, etc) confer high toxicity and/or have low efficacy. However, several β-lactam agents with activity against carbapenem-resistant organisms were approved recently by the US Food and Drug Administration, and more are anticipated to be approved in the near future. The primary goal of this review is to assist infectious disease practitioners with preferentially selecting 1 agent over another when treating patients infected with a carbapenem-resistant organism. However, resistance to some of these antibiotics has already developed. Antibiotic stewardship programs can ensure that they are reserved for situations in which other options are lacking and are paramount for the survival of these agents.

In vitro activity of β-lactams in combination with avibactam against multidrug-resistant Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Achromobacter xylosoxidans isolates from patients with cystic fibrosis

The in vitro activity of anti-pseudomonal β-lactams in combination with avibactam was evaluated against 54 multidrug-resistant non-fermenting Gram-negative bacilli isolated from cystic fibrosis patients. Avibactam increased and/or restored the antibacterial activities of ceftazidime and aztreonam against Pseudomonas aeruginosa and Stenotrophomonas maltophilia, respectively. No β-lactam-avibactam combination was active against Achromobacter xylosoxidans.

In Vitro Activity of Ceftolozane/Tazobactam vs Nonfermenting, Gram-Negative Cystic Fibrosis Isolates

Ceftolozane/tazobactam (C/T) was tested and compared against 93 nonfermenting, Gram-negative clinical isolates from cystic fibrosis specimens. Based on current breakpoints for intra-abdominal and urinary tract infections (which may not be appropriate for pulmonary infections), C/T was found to be the most active agent against P. aeruginosa (95.7% susceptible), followed by piperacillin/tazobactam (89.4% susceptible). For other Gram-negative pathogens included, C/T had varying activity.

Multi-resistant Pseudomonas aeruginosa ST235 in cystic fibrosis

Chronic Pseudomonas aeruginosa infection is associated with a decline in lung function and overall poorer prognosis in the cystic fibrosis population. Molecular typing of P. aeruginosa has identified multiple clonal strains with increased virulence and transmissibility. P. aeruginosa ST235 is an emerging clonal strain with multi-drug resistance and is associated with more virulent infections. Novel cephalosporins, which have recently been introduced to clinical practice, may have higher efficacy against multi-drug resistant bacteria.

In vitro antimicrobial activity of ceftolozane/tazobactam against Pseudomonas aeruginosa and other non-fermenting Gram-negative bacteria in adults with cystic fibrosis

OBJECTIVES

Pulmonary exacerbations in patients with cystic fibrosis (CF) caused by chronic Gram-negative bacterial infections are associated with reduced survival. These pathogens are usually treated with repeated courses of systemic antimicrobial agents. However, there is associated emergence of multidrug-resistant (MDR) pathogens. Ceftolozane/tazobactam (C/T) is a novel cephalosporin/β-lactamase inhibitor combination that has been demonstrated to have good activity against MDR Pseudomonas aeruginosa.

METHODS

In this study, C/T was compared with other commonly used intravenous antimicrobial agents against 193 non-fermenting Gram-negative bacteria isolated from CF sputum specimens, including P. aeruginosa, Achromobacter xylosoxidans, Stenotrophomonas maltophilia and Burkholderia cenocepacia. Minimum inhibitory concentrations (MICs) to C/T were determined by standard Etest assay and were interpreted according to current European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines.

RESULTS

C/T had good in vitro antimicrobial activity against CF clinical isolates of P. aeruginosa in comparison with other antimicrobial agents, with the exception of colistin. C/T also had activity against S. maltophilia but was not active against B. cenocepacia or A. xylosoxidans.

CONCLUSION

C/T showed excellent in vitro activity against P. aeruginosa CF clinical isolates. This antimicrobial agent is a potential therapeutic option when presented with challenging MDR P. aeruginosa and S. maltophilia exacerbations. Further clinical experience and trials in CF are required to determine the place of C/T in clinical practice.

In Vitro Activity of Ceftolozane-Tazobactam and Other Antimicrobial Agents against Burkholderia cepacia Complex and Burkholderia gladioli

We tested the activities of ceftolozane-tazobactam and 13 other antimicrobial agents against 221 strains of Burkholderia cepacia complex and Burkholderia gladioli Most strains (82%) were cultured from persons with cystic fibrosis, and most (85%) were recovered since 2011. The ceftolozane-tazobactam MIC was ≤8 μg/ml for 77% of the strains. However, the MIC range was broad (≤0.5 to >64 μg/ml; MIC_50/90, 2/32 μg/ml). Significant differences in susceptibility to some antimicrobial agents were observed between species.