Double beta-lactam regimen compared to an aminoglycoside/beta-lactam regimen as empiric antibiotic therapy for febrile granulocytopenic cancer patients

High potency of sequential therapy with only β-lactam antibiotics

Evolutionary adaptation is a major source of antibiotic resistance in bacterial pathogens. Evolution-informed therapy aims to constrain resistance by accounting for bacterial evolvability. Sequential treatments with antibiotics that target different bacterial processes were previously shown to limit adaptation through genetic resistance trade-offs and negative hysteresis. Treatment with homogeneous sets of antibiotics is generally viewed to be disadvantageous as it should rapidly lead to cross-resistance. We here challenged this assumption by determining the evolutionary response of Pseudomonas aeruginosa to experimental sequential treatments involving both heterogenous and homogeneous antibiotic sets. To our surprise, we found that fast switching between only β-lactam antibiotics resulted in increased extinction of bacterial populations. We demonstrate that extinction is favored by low rates of spontaneous resistance emergence and low levels of spontaneous cross-resistance among the antibiotics in sequence. The uncovered principles may help to guide the optimized use of available antibiotics in highly potent, evolution-informed treatment designs.

Overuse of antibiotic drugs is leading to the appearance of antibiotic-resistant bacteria; this is, bacteria with mutations that allow them to survive treatment with specific antibiotics. This has made some bacterial infections difficult or impossible to treat. Learning more about how bacteria evolve resistance to antibiotics could help scientists find ways to prevent it and develop more effective treatments.

Changing antibiotics frequently may be one way to prevent bacteria from evolving resistance. That way if a bacterium acquires mutations that allow it to escape one antibiotic, another antibiotic will kill it, stopping it from dividing and preventing the appearance of descendants with resistance to several antibiotics. In order to use this approach, testing is needed to find the best sequences of antibiotics to apply and the optimal timings of treatment.

To find out more, Batra, Roemhild et al. grew bacteria in the laboratory and exposed them to different sequences of antibiotics, switching antibiotics at different time intervals. This showed that sequential treatments with different antibiotics can limit bacterial evolution, especially when antibiotics are switched quickly. Unexpectedly, one of the most effective sequences used very similar antibiotics. This was surprising because using similar antibiotics should lead to the evolution of cross-resistance, which is when a drug causes changes that make the bacterium less sensitive to other treatments. However, in the tested case, cross-resistance did not evolve when antibiotics were switched quickly, thereby ensuring efficiency of treatment.

Batra et al. show that alternating sequences of antibiotics may be an effective strategy to prevent drug resistance. Because the experiments were done in a laboratory setting it will be important to verify the results in studies in animals and humans before the approach can be used in medical or veterinary settings. If the results are confirmed, it could reduce the need to develop new antibiotics, which is expensive and time consuming.

Comparable Efficacy and Better Safety of Double β-Lactam Combination Therapy versus β‑Lactam plus Aminoglycoside in Gram-Negative Bacteria in Randomized, Controlled Trials

There is a great need for efficacious therapies against Gram-negative bacteria. Double β-lactam combination(s) (DBL) are relatively safe, and preclinical data are promising; however, their clinical role has not been well defined. We conducted a metaanalysis of the clinical and microbiological efficacy of DBL compared to β-lactam plus aminoglycoside combinations (BLAG). PubMed, Embase, ISI Web of Knowledge, and Cochrane Controlled Trials Register database were searched through July 2018. We included randomized controlled clinical trials that compared DBL with BLAG combinations. Clinical response was used as the primary outcome and microbiological response in Gram-negative bacteria as the secondary outcome; sensitivity analyses were performed for Pseudomonas aeruginosa, Klebsiella spp., and Escherichia coli Heterogeneity and risk of bias were assessed. Safety results were classified by systems and organs. Thirteen studies evaluated 2,771 cases for clinical response and 665 cases for microbiological response in various Gram-negative species. DBL achieved slightly, but not significantly, better clinical response (risk ratio, 1.05; 95% confidence interval [CI], 0.99 to 1.11) and microbiological response in Gram-negatives (risk ratio, 1.11; 95% CI, 0.99 to 1.25) compared with BLAG. Sensitivity analyses by pathogen showed the same trend. No significant heterogeneity across studies was found. DBL was significantly safer than BLAG regarding renal toxicity (6.6% versus 8.8%, P = 0.0338) and ototoxicity (0.7 versus 3.1%, P = 0.0137). Other adverse events were largely comparable. Overall, empirically designed DBL showed comparable clinical and microbiological responses across different Gram-negative species, and were significantly safer than BLAG. Therefore, DBL should be rationally optimized via the latest translational approaches, leveraging mechanistic insights and newer β-lactams for future evaluation in clinical trials.

WCK 5107 (Zidebactam) and WCK 5153 Are Novel Inhibitors of PBP2 Showing Potent "β-Lactam Enhancer" Activity against Pseudomonas aeruginosa, Including Multidrug-Resistant Metallo-β-Lactamase-Producing High-Risk Clones

Zidebactam and WCK 5153 are novel β-lactam enhancers that are bicyclo-acyl hydrazides (BCH), derivatives of the diazabicyclooctane (DBO) scaffold, targeted for the treatment of serious infections caused by highly drug-resistant Gram-negative pathogens. In this study, we determined the penicillin-binding protein (PBP) inhibition profiles and the antimicrobial activities of zidebactam and WCK 5153 against Pseudomonas aeruginosa, including multidrug-resistant (MDR) metallo-β-lactamase (MBL)-producing high-risk clones. MIC determinations and time-kill assays were conducted for zidebactam, WCK 5153, and antipseudomonal β-lactams using wild-type PAO1, MexAB-OprM-hyperproducing (mexR), porin-deficient (oprD), and AmpC-hyperproducing (dacB) derivatives of PAO1, and MBL-expressing clinical strains ST175 (bla_VIM-2) and ST111 (bla_VIM-1). Furthermore, steady-state kinetics was used to assess the inhibitory potential of these compounds against the purified VIM-2 MBL. Zidebactam and WCK 5153 showed specific PBP2 inhibition and did not inhibit VIM-2 (apparent K_i [K_iapp] > 100 μM). MICs for zidebactam and WCK 5153 ranged from 2 to 32 μg/ml (amdinocillin MICs > 32 μg/ml). Time-kill assays revealed bactericidal activity of zidebactam and WCK 5153. LIVE-DEAD staining further supported the bactericidal activity of both compounds, showing spheroplast formation. Fixed concentrations (4 or 8 μg/ml) of zidebactam and WCK 5153 restored susceptibility to all of the tested β-lactams for each of the P. aeruginosa mutant strains. Likewise, antipseudomonal β-lactams (CLSI breakpoints), in combination with 4 or 8 μg/ml of zidebactam or WCK 5153, resulted in enhanced killing. Certain combinations determined full bacterial eradication, even with MDR MBL-producing high-risk clones. β-Lactam-WCK enhancer combinations represent a promising β-lactam "enhancer-based" approach to treat MDR P. aeruginosa infections, bypassing the need for MBL inhibition.

Dual beta-lactam therapy for serious Gram-negative infections: is it time to revisit?

We are rapidly approaching a crisis in antibiotic resistance, particularly among Gram-negative pathogens. This, coupled with the slow development of novel antimicrobial agents, underscores the exigency of redeploying existing antimicrobial agents in innovative ways. One therapeutic approach that was heavily studied in the 1980s but abandoned over time is dual beta-lactam therapy. This article reviews the evidence for combination beta-lactam therapy. Overall, in vitro, animal and clinical data are positive and suggest that beta-lactam combinations produce a synergistic effect against Gram-negative pathogens that rivals that of beta-lactam-aminoglycoside or beta-lactam-fluoroquinolone combination therapy. Although the precise mechanism of improved activity is not completely understood, it is likely attributable to an enhanced affinity to the diverse penicillin-binding proteins found among Gram negatives. The collective data indicate that dual beta-lactam therapy should be revisited for serious Gram-negative infections, especially in light of the near availability of potent beta-lactamase inhibitors, which neutralize the effect of problematic beta-lactamases.

In vitro activity of ceftaroline alone and in combination against clinical isolates of resistant gram-negative pathogens, including beta-lactamase-producing Enterobacteriaceae and Pseudomonas aeruginosa

Ceftaroline is a novel broad-spectrum cephalosporin that exhibits bactericidal activity against many gram-positive and -negative pathogens. However, the activity of ceftaroline cannot be solely relied upon for eradication of multidrug-resistant gram-negative isolates, such as Pseudomonas aeruginosa and extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae, which represent a current clinical concern. As drug combinations might be beneficial by potential synergy, we evaluated the in vitro activity of ceftaroline combined with meropenem, aztreonam, cefepime, tazobactam, amikacin, levofloxacin, and tigecycline. Susceptibility testing was performed for 20 clinical P. aeruginosa isolates, 10 ESBL-producing Escherichia coli isolates, 10 ESBL-producing Klebsiella pneumoniae isolates, and 10 AmpC-derepressed Enterobacter cloacae isolates. Time-kill experiments were performed for 10 isolates using antimicrobials at one-fourth the MIC. Ceftaroline exhibited a MIC range of 0.125 to 1,024 microg/ml and was reduced 2- to 512-fold by combination with tazobactam (4 microg/ml) for ESBL-producing strains. In time-kill experiments, ceftaroline plus amikacin was synergistic against 90% of the isolates (and indifferent for one P. aeruginosa isolate). Ceftaroline plus tazobactam was indifferent for E. cloacae and P. aeruginosa strains but synergistic against 100% of E. coli and K. pneumoniae isolates. Combinations of ceftaroline plus meropenem or aztreonam were also synergistic for all E. coli and E. cloacae isolates, respectively, but indifferent against 90% of the other isolates. Finally, combinations of ceftaroline plus either tigecycline, levofloxacin, or cefepime were indifferent for 100% of the isolates. No antagonism was observed with any combination. Ceftaroline plus amikacin appeared as the most likely synergistic combination. This represents a promising therapeutic option, and further studies are warranted to elucidate the clinical value of ceftaroline combinations against resistant gram-negative pathogens.

Inhibition of flucloxacillin tubular renal secretion by piperacillin

AIMS

To explore the extent, time course, site(s), mechanism and possible clinical relevance of the pharmacokinetic (PK) interaction between piperacillin and flucloxacillin.

METHODS

A single-dose, randomized, six-way crossover study in 10 healthy volunteers where all subjects received all of the following as 5-min intravenous infusions: (i) 1.5 g piperacillin, (ii) 0.5 g flucloxacillin, (iii) 1.5 g piperacillin + 0.5 g flucloxacillin, (iv) 3 g piperacillin, (v) 1 g flucloxacillin, and (vi) 3 g piperacillin + 1 g flucloxacillin. Drug concentrations in plasma and urine were determined by high-performance liquid chromatography. WinNonlin was used for PK modelling and statistics.

RESULTS

Piperacillin significantly decreased the renal clearance of flucloxacillin from 5.44 to 2.29 l h(-1) (medians, P < 0.01) and the nonrenal clearance of flucloxacillin from 2.67 to 1.80 l h(-1) (P < 0.01). The renal clearance of flucloxacillin was reduced to 45% (point estimate, 90% confidence interval 40 to 50%) and the nonrenal clearance to 66% (59, 73). The extent of interaction was larger at the higher doses. Competitive inhibition of tubular secretion by piperacillin was identified as the most likely mechanism for the decreased renal clearance of flucloxacillin. Piperacillin had a 15-times higher affinity for the renal transporter than flucloxacillin based on the molar ratio. Piperacillin PK was only slightly affected by flucloxacillin.

CONCLUSIONS

Piperacillin inhibits renal and nonrenal elimination of flucloxacillin. This interaction seems clinically significant, as total clearance was reduced by a factor of 1.5 for the lower and 2.1 for the higher doses. PK interactions, especially with piperacillin, are likely to occur also with other beta-lactam combinations and might be useful to improve the effectiveness of antibacterial treatment.

Amikacin and ceftazidime as empirical antibiotic therapy in severely neutropenic patients: analysis of prognostic factors

This study aimed to evaluate the efficacy of amikacine and ceftazidime as an empirical antibiotic therapy for neutropenic patients affected by haematological neoplasms and to investigate the presence of prognostic features suggesting a poor outcome with this antibiotic combination at the onset of infection. This could allow the identification of subgroups of patients with a low rate of response to amikacin/ceftazidime therapy; in these patients different initial empirical therapy may be indicated. The study population comprised 166 severely neutropenic (absolute neutrophil count below 500/microliters) oncohaematological patients with fever or clinical signs of infection. Multivariate analysis confirmed four negative prognostic factors: 3 or more days of hospitalization at the onset of an infectious episode, a diagnosis of acute myelmany factors are present, cases can be stratified into three groups, of significantly different prognosis: favourable (0 or 1 factor) 76% success; intermediate (2 factors) 52% success; unfavourable (3 or 4 factors) 19% success. At the onset of an infectious episode a subgroup of patients with a very low response rate to empirical amikacin/ceftazidime antibiotic therapy is identifiable, for whom a different therapy is indicated. Because of the high rate of proven or probable fungal infections in this group, the immediate administration of a systemic antifungal therapy, in addition to antibacterial agents, could be considered in these high-risk patients. Studies should be specifically addressed to evaluating a stratification of empirical antibiotic therapy according to risk factors present at the onset of infection.