Looking beyond ceftazidime-avibactam resistance in KPC-producing Klebsiella pneumoniae: in vitro activity of the novel meropenem-vaborbactam in combination with the old fosfomycin

Synergistic Activity of Temocillin and Fosfomycin Combination against KPC-Producing Klebsiella pneumoniae Clinical Isolates

Infections caused by KPC-producing K. pneumoniae continue to pose a significant clinical challenge due to their emerging resistance to new antimicrobials. We investigated the association between two drugs whose roles have been repurposed against multidrug-resistant bacteria: fosfomycin and temocillin. Temocillin exhibits unusual stability against KPC enzymes, while fosfomycin acts as a potent "synergizer". We conducted in vitro antimicrobial activity studies on 100 clinical isolates of KPC-producing K. pneumoniae using a combination of fosfomycin and temocillin. The results demonstrated synergistic activity in 91% of the isolates. Subsequently, we assessed the effect on Galleria mellonella larvae using five genetically different KPC-Kp isolates. The addition of fosfomycin to temocillin increased larvae survival from 73 to 97% (+Δ 32%; isolate 1), from 93 to 100% (+Δ 7%; isolate 2), from 63 to 86% (+Δ 36%; isolate 3), from 63 to 90% (+Δ 42%; isolate 4), and from 93 to 97% (+Δ 4%; isolate 10). Among the temocillin-resistant KPC-producing K. pneumoniae isolates (24 isolates), the addition of fosfomycin reduced temocillin MIC values below the resistance breakpoint in all isolates except one. Temocillin combined with fosfomycin emerges as a promising combination against KPC-producing K. pneumoniae, warranting further clinical evaluation.

Simultaneous post-neurosurgical ventriculitis and bacteraemia by two different strains of KPC-producing K. pneumoniae successfully treated with meropenem/vaborbactam and high dose of fosfomycin

OBJECTIVE

A case of post-neurosurgical ventriculitis caused by a KPC-producing Klebsiella pneumoniae (KPC-Kp) with a ceftazidime/avibactam-resistant, meropenem-susceptible phenotype is reported.

METHODS AND RESULTS

The patient had a concomitant bloodstream infection with a wild-type KPC-Kp with a ceftazidime/avibactam-susceptible, meropenem-resistant phenotype. Prolonged treatment with intravenous fosfomycin and meropenem/vaborbactam achieved clinical success. Therapeutic drug monitoring performed during the first days of treatment showed for the first time that vaborbactam efficiently penetrates cerebrospinal fluid. In contrast, meropenem was undetectable in cerebrospinal fluid at each sampling, suggesting that additional doses of meropenem may be required to appropriately prescribe meropenem/vaborbactam for central nervous system infections. Plasma and cerebrospinal fluid levels of fosfomycin were adequate, confirming the potential of this agent possibly even in the fight against multidrug-resistant organisms.

CONCLUSIONS

This case highlights the need for therapeutic drug monitoring as a crucial tool for optimizing treatment in complicated cases where the pharmacokinetic behaviour of antibiotics is difficult to predict.

Clinical Characteristics and Outcome of Ceftazidime/Avibactam-Resistant Klebsiella pneumoniae Carbapenemase-Producing Klebsiella pneumoniae Infections: A Retrospective, Observational, 2-Center Clinical Study

Background

Recently, Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae (KPC-Kp) with resistance to ceftazidime/avibactam (CZA-R) has been described, including KPC variants that restore carbapenem susceptibility. The aim of the study was to analyze the clinical characteristics and outcomes of infections caused by CZA-R KPC-Kp.

Methods

From 2019 to 2021, a retrospective 2-center study including patients with infections due to CZA-R KPC-Kp hospitalized at 2 academic hospitals in Rome was conducted. Demographic and clinical characteristics were collected. Principal outcome was 30-day all-cause mortality. Statistical analyses were performed with Stata-IC17 software.

Results

Overall, 59 patients were included (mean age, 64.4 ± 14.6 years; mean Charlson comorbidity index score, 4.5 ± 2.7). Thirty-four patients (57.6%) had infections caused by CZA-R and meropenem (MEM)-susceptible strains. A previous CZA therapy was observed in 40 patients (67.8%), mostly in patients with MEM-susceptible KPC variant (79.4% vs 52%, P = .026). Primary bacteremia was observed in 28.8%, followed by urinary tract infections and pneumonia. At infection onset, septic shock was present in 15 subjects (25.4%). After adjustment for confounders, only the presence of septic shock was independently associated with mortality (P = .006).

Conclusions

Infections due to CZA-R KPC-Kp often occur in patients who had previously received CZA, especially in the presence of strains susceptible to MEM. Nevertheless, one-third of patients had never received CZA before KPC-Kp CZA-R. Since the major driver for mortality was infection severity, understanding the optimal therapy in patients with KPC-Kp CZA-R infections is of crucial importance.

New evidence for managing Gram-negative bloodstream infections

PURPOSE OF REVIEW

Gram-negative bloodstream infections (GNBSI) are common and carry considerable mortality. Treatment is complicated by increasing antimicrobial resistance, posing a challenge for timely appropriate antibiotics and limiting the choices of effective definitive therapy. The present review aims to summarize recent studies addressing the management of GNBSI.

RECENT FINDINGS

New rapid diagnostic tests (RDT) for pathogen identification and antibiotic susceptibility are associated with improved antimicrobial stewardship and reduced length of stay. No mortality benefit or patient-related outcomes are reported. Data regarding the use of new beta-lactam beta-lactamase inhibitors (BLBLIs) for treating multidrug resistance Gram-negative bacteria is supportive, though questions regarding combinations, optimal dosing, mode of administration, and resistance emergence remain to be clarified. Current data regarding cefiderocol necessitates further studies in order to support its use in GNBSI. Shortened (≤7 days) duration of therapy and early oral step down for GNBSI are supported by the literature. The role of repeated blood cultures should be further defined.

SUMMARY

RDTs should be implemented to improve antibiotic stewardship. Clinical implications on patient-related outcomes should be evaluated. New BLBLIs show promise in the treatment of GNBSI. Additional data are needed regarding the use of cefiderocol. Antibiotic therapy should be shortened and early oral step down should be considered.