Susceptibility of cefiderocol and other antibiotics against carbapenem-resistant, Gram-negative bacteria

Introduction

With the extensive use of carbapenems, the emergence of carbapenem-resistant, Gram-negative bacteria has become a threat to public health worldwide. These pathogens are usually multidrug-resistant (MDR), show multiple mechanisms of resistance, and are highly resistant to commonly prescribed antimicrobial agents. Owing to the very limited therapeutic options, polymyxins and tigecycline are often prescribed as last-resort therapies. However, there are limitations to these therapies, such as the high nephrotoxicity of polymyxins and unsatisfactory pharmacokinetics of tigecycline (1,2). Furthermore, there is resistance to these therapies following their increased clinical application (3,4). Infections caused by carbapenem-resistant, Gram-negative bacteria are still associated with high morbidity and mortality rates, considerably increasing clinical and economic burdens.

In recent years, several new antibiotics have been developed for the treatment of carbapenem-resistant, Gram-negative bacteria. Among them, a novel synthetic siderophore-conjugated antibiotic, cefiderocol, has shown promise as an antimicrobial agent (5). The addition of a catechol siderophore moiety on the C-3 side-chain allows cefiderocol to hijack bacterial iron transport systems, facilitating entry into cells, and therefore achieving high periplasmic concentrations (6). In addition, cefiderocol has high affinity for penicillin-binding protein 3 and is less susceptible to β-lactamases, including Klebsiella pneumoniae carbapenemase (KPC), New Delhi metallo-β-lactamase (NDM), and oxacillinases (OXA) carbapenemases (7). Cefiderocol has been approved in the Food and Drug Administration for the treatment of nosocomial pneumonia and complicated urinary tract infections in 2019. Europe approved its use for the treatment of refractory MDR, Gram-negative infections with limited treatment options in 2020.

In the previous study, the in vitro activity of cefiderocol was evaluated against Gram-negative bacteria isolated from Europe, North America, Latin America, and Japan, showing good activity against MDR pathogens, including extended spectrum β-lactamase (ESBL)- and carbapenemase-producing isolates (8). However, susceptibility data on pathogens from mainland China have not been reported. Therefore, in the present study, we analyzed the antimicrobial susceptibility of cefiderocol against clinical isolates of several carbapenem-resistant, Gram-negative bacteria collected from Beijing, China. We present the following article in accordance with the MDAR reporting checklist (available at https://atm.amegroups.com/article/view/10.21037/atm-22-889/rc).

Methods

Four species of non-duplicate carbapenem-resistant, Gram-negative bacteria were isolated from inpatients at 4 tertiary A-level hospitals (Peking University People’s Hospital, The Sixth Medical Center of PLA General Hospital, Air Force Medical Center and Peking University First Hospital) in 2012–2018. These bacteria were carbapenem-resistant Klebsiella pneumoniae (CR-KP; n=105), carbapenem-resistant Pseudomonas aeruginosa (CR-PA; n=74), MDR Stenotrophomonas maltophilia (SM; n=72), and carbapenem-resistant Acinetobacter baumannii (CR-AB; n=126). Most isolates were isolated from sputum and blood samples. The isolates were stored at −80 ℃ before testing. They were recovered from Mueller-Hinton agar plates for 3 successive generations. All the isolates were identified using the VITEK automated platform (bioMérieux, Marcy-l’Étoile, France). Escherichia coli American Type Culture Collection 25922 was used as the quality control strain. As all in vitro samples were anonymized, the ethics committees waived the requirement for ethical approval of our study or informed consent from patients. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013).

The minimum inhibitory concentrations (MICs) of various antimicrobial agents (ceftazidime, meropenem, imipenem, amikacin, ceftazidime, cefepime, ceftazidime/avibactam, piperacillin/tazobactam, ticarcillin/clavulanate, cefoperazone/sulbactam, tigecycline, minocycline, colistin, levofloxacin, ciprofloxacin, moxifloxacin, fosfomycin, rifampicin, trimethoprim-sulfamethoxazole, and chloramphenicol) were determined by standard broth microdilution methods with cation-adjusted Mueller Hinton broth (CAMHB) according to the recommendations of the Clinical and Laboratory Standards Institute (CLSI) (9). The MICs of cefiderocol were determined in iron-depleted CAMHB according to the CLSI (9). The MICs of cefiderocol were defined as the lowest concentration to completely inhibit organism growth or the lowest concentration at which growth was significantly reduced compared to that of the control well (trailing end-points were disregarded) (9). Isolates were tested in duplicate. If the results were not consistent, a third test was performed. The breakpoints for cefiderocol and other comparator agents were determined using the criteria established by the CLSI guidelines (9). The breakpoints for tigecycline against CR-KP were determined using the criteria established by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) (10). For cefiderocol, MIC ≤4 mg/L was considered susceptible, 8 mg/L as intermediate, and ≥16 mg/L as resistant.

All CR-KP isolates were screened for the presence of carbapenemases genes (bla_KPC, bla_NDM, bla_IMP, bla_VIM, bla_SIM and bla_OXA-48), and all CR-AB isolates were screened for various β-lactamase genes (bla_SHV, bla_PER, bla_TEM, bla_CTX-M-1, bla_CTX-M-2, bla_CTX-M-8, bla_CTX-M-9, bla_CTX-M-25, bla_GES, bla_IMP, bla_VIM, bla_OXA-23, bla_OXA-24 and bla_OXA-58) by polymerase chain reaction (PCR) assays, as previously described (11).

Statistical analysis

Statistical analyses were performed with GraphPad Prism 8.0 software (GraphPad Software Inc., La Jolla, CA, USA). Experimental data were expressed as mean ± standard deviation. P values were calculated using the Student’s t-test if calculation was needed, and P values <0.05 were considered statistically significant.

Results

Susceptibility of cefiderocol against CR-KP

MIC values of cefiderocol against the CR-KP isolates ranged from <0.03 to 2 mg/L, with MIC₅₀ and MIC₉₀ values of 0.125 and 1 mg/L, respectively (Table 1). Cefiderocol inhibited 100% of the tested isolates at the susceptibility breakpoint concentration of 4 mg/L. Susceptibility rates for colistin and ceftazidime/avibactam were 97.1% and 94.3%, respectively. MIC values of tigecycline ranged from 0.25 to 4 mg/L, and the susceptibility rate was 58.1%, with a breakpoint of 0.5 mg/L, according to the EUCAST. The curves of the cumulative percentage of CR-KP isolates inhibited at various concentrations of cefiderocol, colistin, tigecycline, minocycline, and ceftazidime/avibactam showed that cefiderocol was the most potent antimicrobial (Figure 1A). All isolates were screened for carbapenemase genes (bla_KPC, bla_NDM, bla_IMP, bla_VIM, bla_SIM, and bla_OXA-48) using PCR assay. Eight isolates harbored bla_NDM-1, whereas other isolates harbored bla_KPC-2. MICs of cefiderocol for most isolates harboring bla_KPC-2 were <0.5 mg/L. All isolates harboring bla_NDM-1 were resistant to ceftazidime/avibactam, with the MICs of cefiderocol ranging from 1 to 2 mg/L, which were relatively higher than those of isolates with bla_KPC-2.

Figure 1 Cumulative MIC distribution (percentage of isolates) of cefiderocol and comparator agents for CR-KP, CR-PA, SM and CR-AB. MIC, minimum inhibitory concentration; CR-KP, carbapenem-resistant Klebsiella pneumoniae; CR-PA, carbapenem-resistant Pseudomonas aeruginosa; SM, Stenotrophomonas maltophilia; CR-AB, carbapenem-resistant Acinetobacter baumannii.

Susceptibility of cefiderocol against CR-PA

As shown in Table 1, the MIC values of cefiderocol ranged from <0.03 to 4 mg/L, with MIC₅₀ and MIC₉₀ values of 0.5 and 4 mg/L, respectively. Other active agents against CR-PA were colistin, with 97.3% of isolates found to be susceptible, and amikacin, with 80% of isolates found to be susceptible. Figure 1B shows the cumulative percentage of CR-PA isolates inhibited at various concentrations of cefiderocol and comparator agents. A further analysis showed that the MIC₅₀ and MIC₉₀ values for cefiderocol tested against CR-PA with concurrent cefepime resistance (n=23) were 2 and 4 mg/L, respectively, whereas those for cefepime non-resistant isolates (n=51) were 0.25 and 2 mg/L, respectively (Table 2).

Susceptibility of cefiderocol against MDR SM

All the SM isolates tested in this study were MDR, with a resistance rate to trimethoprim-sulfamethoxazole of 77.8%. As shown in Table 1, the MIC values of cefiderocol ranged from <0.03 to 128 mg/L, with MIC₅₀ and MIC₉₀ values of 0.125 and 0.5 mg/L, respectively. One isolate was resistant to cefiderocol. Figure 1C shows the cumulative percentage of MDR SM isolates inhibited at various concentrations of cefiderocol and comparator agents. Cefiderocol was the most active agent, followed by minocycline, with a susceptibility rate of 93%. MICs of tigecycline and moxifloxacin ranged from 0.5–32 mg/L and 0.25–>16 mg/L, respectively, with MIC₅₀ values of 2 and 1 mg/L, respectively.

Susceptibility of cefiderocol against CR-AB

MIC values of cefiderocol against the various CR-AB isolates ranged from 0.06 to >128 mg/L, with MIC₅₀ and MIC₉₀ values of 0.5 and 128 mg/L, respectively (Table 1). The susceptibility rate for cefiderocol was only 62.7%, with a resistance rate of 35%. Susceptibility rates for colistin and amikacin was 97.6% and 40.5%, respectively. MIC values of tigecycline ranged from 0.125 to 8 mg/L, with MIC₅₀ and MIC₉₀ values of 1 and 2 mg/L, respectively. Figure 1D shows the cumulative percentage of isolates inhibited at various MICs of cefiderocol and comparator agents against CR-AB isolates, indicating that colistin was the most active comparator agent.

We further screened all the CR-AB isolates for various β-lactamase genes (bla_SHV, bla_PER, bla_TEM, bla_CTX-M-1, bla_CTX-M-2, bla_CTX-M-8, bla_CTX-M-9, bla_CTX-M-25, bla_GES, bla_IMP, bla_VIM, bla_OXA-23, bla_OXA-24 and bla_OXA-58) using PCR assay. Most cefiderocol-susceptible CR-AB isolates were found to be positive for bla_OXA-23 and bla_TEM, whereas all the cefiderocol non-susceptible CR-AB isolates were found to be positive for the bla_PER genes, in addition to bla_OXA-23 and bla_TEM. The MIC distributions of cefiderocol against bla_PER-positive and bla_PER-negative CR-AB was shown in Figure 2.

Figure 2 Cefiderocol MIC distributions against bla_PER-positive and bla_PER-negative CR-AB. MIC, minimum inhibitory concentration; CR-AB, carbapenem-resistant Acinetobacter baumannii.

Discussion

MDR, Gram-negative bacteria, including carbapenem-resistant Enterobacteriaceae, CR-AB, and CR-PA, and MDR SM, are considered superbugs in healthcare settings. They are associated with resistance to nearly all classes of antibiotics commonly used in clinical settings. Current available treatment options for systemic infections caused by these organisms are limited. Cefiderocol, the novel siderophore cephalosporin, has showed potent in vitro activity against carbapenem-resistant, Gram-negative bacteria, giving hope for combating these superbugs. However, resistance to a novel antibiotic could already exist. Therefore, antimicrobial resistance surveillance from both a global and local scale can provide useful information for guidance on the empirical use of antibiotics and the development of rational antimicrobial stewardship policies.

In the current study, all CR-KP isolates were susceptible to cefiderocol. Cefiderocol showed more potent in vitro antimicrobial activity than colistin, tigecycline, and ceftazidime/avibactam. In China, the main carbapenemases in CR-KP are KPC, followed by NDM (12). We further found that the MICs of cefiderocol for CR-KP with bla_NDM-1 ranged from 1 to 2 mg/L, which were relatively higher than those of isolates with bla_KPC-2. These findings were in accordance with those reported in the SIDERO-CR study, which showed that cefiderocol had less potent activity against NDM-producing isolates compared with other isolates (13). It has been reported that the use of ceftazidime/avibactam to treat KPC-producing CR-KP could lead to a shift in the carbapenemase landscape, from the KPC to MBLs (14). The wide of use cefiderocol in future may also lead to the selection of NDM-producing isolates.

Previous susceptibility has demonstrated the potency of cefiderocol against the CR-AB. The ARGONAUT-I study tested the MIC values of cefiderocol against 101 CR-AB isolates, with MICs ranging from ≤0.03 to >64 mg/L, and MIC₅₀ and MIC₉₀ values of 0.25 and 1 mg/L, respectively (15). In their study, Falagas et al. included 107 CR-AB isolates collected from 18 Greek hospitals, with MIC₅₀ and MIC₉₀ values of cefiderocol of 0.06 and 0.5 mg/L, respectively (16). Hackel et al.’s study included 368 MDR AB isolates collected from laboratories from 52 countries in 2014 to 2016. They found that the MIC₅₀ and MIC₉₀ values of cefiderocol were 0.25 and 8 mg/L, respectively (17). Surprisingly, the susceptibility rate for cefiderocol against CR-AB in our study was much lower than those reported in the above studies. It has been reported that PER β-lactamase is associated with cefiderocol resistance in CR-AB (18). We found that all cefiderocol non-susceptible CR-AB isolates were positive for the bla_PER gene, in addition to bla_OXA-23 and bla_TEM, suggesting that PER β-lactamase contributes to decreased cefiderocol susceptibility and a possible high prevalence of bla_PER in CR-AB isolates in Beijing, China.

Cefiderocol at a concentration of 4 mg/L inhibited 100% of all CR-PA isolates and 98.6% of all MDR SM isolates, indicating that cefiderocol had potent in vitro activity against these 2 non-fermentative bacteria in the present study. The MIC distribution for SM was similar to that reported in other studies (19-21). Nevertheless, the MIC values for CR-PA (MIC₉₀ =4 mg/L) were generally higher than those reported by other centers. The ARGONAUT-I study tested the MIC values of cefiderocol against 27 CR-PA isolates, with the MICs ranging from 0.03 to 1 mg/L and MIC₅₀ and MIC₉₀ values of 0.25 and 0.5 mg/L, respectively (15). A study by Kazmierczak et al., which included 353 meropenem non-susceptible PA isolates collected from Europe and North America in the SIDERO-WT-2014 surveillance project, showed that the MIC₅₀ and MIC₉₀ values of cefiderocol were 0.12 and 1 mg/L, respectively (11). Liu et al.’s study, which included 150 CR-PA isolates collected from Taiwan, China, showed MIC₅₀ and MIC₉₀ values of cefiderocol of 0.25 and 1 mg/L, respectively (22). Our further analysis showed the MICs for cefiderocol tested against CR-PA isolates with concurrent cefepime resistance were generally higher than those for cefepime non-resistant isolates. The concrete mechanisms of cefepime resistance and the relationship between cefepime resistance and decreased cefiderocol susceptibility should be further investigated.

Our study has several limitations. First, a relatively small number of isolates collected from a single region were tested. Second, we did not perform an in-depth investigation of the molecular epidemiology of the isolates. Therefore, the generalizability of our findings to other centers and regions where the genotypes and the frequency of different β-lactamase genes might differ requires further confirmation.

Overall, the first susceptibility surveillance on cefiderocol from mainland China found that cefiderocol had potent in vitro activity against CR-KP, CR-PA, and MDR SA isolates collected from Beijing, China. However, the resistance rate for cefiderocol against CR-AB was higher than that reported by other research centers (8), and the presence of bla_PER might be related to cefiderocol resistance in those non-susceptible CR-AB.

Acknowledgments

Funding: This research was funded by Peking University People’s Hospital Research and Development Funds (Grant No. RS2020-04).

Footnote

Reporting Checklist: The authors have completed the MDAR reporting checklist. Available at https://atm.amegroups.com/article/view/10.21037/atm-22-889/rc

Data Sharing Statement: Available at https://atm.amegroups.com/article/view/10.21037/atm-22-889/dss

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://atm.amegroups.com/article/view/10.21037/atm-22-889/coif). WN reports that this research was funded by Peking University People’s Hospital Research and Development Funds (Grant No. RS2020-04). The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. As all in vitro samples were anonymized, the ethics committees waived the requirement for ethical approval of our study or informed consent from patients. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013).

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Wagenlehner F, Lucenteforte E, Pea F, et al. Systematic review on estimated rates of nephrotoxicity and neurotoxicity in patients treated with polymyxins. Clin Microbiol Infect 2021; Epub ahead of print. [Crossref] [PubMed]
2. Leng B, Yan G, Wang C, et al. Dose optimisation based on pharmacokinetic/pharmacodynamic target of tigecycline. J Glob Antimicrob Resist 2021;25:315-22. [Crossref] [PubMed]
3. Poirel L, Jayol A, Nordmann P. Polymyxins: Antibacterial activity, susceptibility testing, and resistance mechanisms encoded by plasmids or chromosomes. Clin Microbiol Rev 2017;30:557-96. [Crossref] [PubMed]
4. Sun J, Chen C, Cui CY, et al. Plasmid-encoded tet(X) genes that confer high-level tigecycline resistance in Escherichia coli. Nat Microbiol 2019;4:1457-64. [Crossref] [PubMed]
5. Zhanel GG, Golden AR, Zelenitsky S, et al. Cefiderocol: A Siderophore Cephalosporin with Activity Against Carbapenem-Resistant and Multidrug-Resistant Gram-Negative Bacilli. Drugs 2019;79:271-89. [Crossref] [PubMed]
6. Page MGP. The Role of Iron and Siderophores in Infection, and the Development of Siderophore Antibiotics. Clin Infect Dis 2019;69:S529-37. [Crossref] [PubMed]
7. Aoki T, Yoshizawa H, Yamawaki K, et al. Cefiderocol (S-649266), A new siderophore cephalosporin exhibiting potent activities against Pseudomonas aeruginosa and other gram-negative pathogens including multi-drug resistant bacteria: Structure activity relationship. Eur J Med Chem 2018;155:847-68. [Crossref] [PubMed]
8. Yamano Y. In Vitro Activity of Cefiderocol Against a Broad Range of Clinically Important Gram-negative Bacteria. Clin Infect Dis 2019;69:S544-51. [Crossref] [PubMed]
9. Clinical and Laboratory Standards Institute (CLSI). M100 Performance Standards for Antimicrobial Susceptibility Testing. 30th ed. Wayne: Clinical and Laboratory Standards Institute, 2020.
10. The European Committee on Antimicrobial Susceptibility Testing (EUCAST). The European Committee on Antimicrobial Susceptibility Testing. Breakpoint Tables for Interpretation of Mics and Zone Diameters (Version 11.0). 2021. Available online: https://www.eucast.org/fileadmin/src/media/PDFs/EUCAST_files/Breakpoint_tables/v_11.0_Breakpoint_Tables.pdf (accessed on 30 October 2021).
11. Kazmierczak KM, Tsuji M, Wise MG, et al. In vitro activity of cefiderocol, a siderophore cephalosporin, against a recent collection of clinically relevant carbapenem-non-susceptible Gram-negative bacilli, including serine carbapenemase- and metallo-β-lactamase-producing isolates (SIDERO-WT-2014 Study). Int J Antimicrob Agents 2019;53:177-84. [Crossref] [PubMed]
12. Wang Q, Wang X, Wang J, et al. Phenotypic and Genotypic Characterization of carbapenem-resistant Enterobacteriaceae: Data from a longitudinal large-scale CRE study in China (2012-2016). Clin Infect Dis 2018;67:S196-205. [Crossref] [PubMed]
13. Longshaw C, Manissero D, Tsuji M, et al. In vitro activity of the siderophore cephalosporin, cefiderocol, against molecularly characterized, carbapenem-non-susceptible Gram-negative bacteria from Europe. JAC Antimicrob Resist 2020;2:dlaa060.
14. Papadimitriou-Olivgeris M, Bartzavali C, Lambropoulou A, et al. Reversal of carbapenemase-producing Klebsiella pneumoniae epidemiology from blaKPC- to blaVIM-harbouring isolates in a Greek ICU after introduction of ceftazidime/avibactam. J Antimicrob Chemother 2019;74:2051-4. [Crossref] [PubMed]
15. Jacobs MR, Abdelhamed AM, Good CE, et al. ARGONAUT-I: Activity of Cefiderocol (S-649266), a Siderophore Cephalosporin, against Gram-Negative Bacteria, Including Carbapenem-Resistant Nonfermenters and Enterobacteriaceae with Defined Extended-Spectrum β-Lactamases and Carbapenemases. Antimicrob Agents Chemother 2019;63:e01801-18. [Crossref] [PubMed]
16. Falagas ME, Skalidis T, Vardakas KZ, et al. Activity of cefiderocol (S-649266) against carbapenem-resistant Gram-negative bacteria collected from inpatients in Greek hospitals. J Antimicrob Chemother 2017;72:1704-8. [Crossref] [PubMed]
17. Hackel MA, Tsuji M, Yamano Y, et al. In vitro activity of the siderophore cephalosporin, cefiderocol, against carbapenem-nonsusceptible and multidrug-resistant isolates of Gram-negative bacilli collected worldwide in 2014 to 2016. Antimicrob Agents Chemother 2018;62:e01968-17. [Crossref] [PubMed]
18. Poirel L, Sadek M, Nordmann P. Contribution of PER-Type and NDM-Type β-lactamases to cefiderocol resistance in Acinetobacter baumannii. Antimicrob Agents Chemother 2021;65:e0087721. [Crossref] [PubMed]
19. Hackel MA, Tsuji M, Yamano Y, et al. In vitro activity of the siderophore cephalosporin, cefiderocol, against a recent collection of clinically relevant Gram-Negative bacilli from North America and Europe, including carbapenem-nonsusceptible isolates (SIDERO-WT-2014 Study). Antimicrob Agents Chemother 2017;61:e00093-17. [Crossref] [PubMed]
20. Karlowsky JA, Hackel MA, Tsuji M, et al. In vitro activity of cefiderocol, a siderophore cephalosporin, against Gram-negative bacilli isolated by clinical laboratories in North America and Europe in 2015-2016: SIDERO-WT-2015. Int J Antimicrob Agents 2019;53:456-66. [Crossref] [PubMed]
21. Cercenado E, Cardenoso L, Penin R, et al. In vitro activity of cefiderocol and comparators against isolates of Gram-negative bacterial pathogens from a range of infection sources: SIDERO-WT-2014-2018 studies in Spain. J Glob Antimicrob Resist 2021;26:292-300. [Crossref] [PubMed]
22. Liu PY, Ko WC, Lee WS, et al. In vitro activity of cefiderocol, cefepime/enmetazobactam, cefepime/zidebactam, eravacycline, omadacycline, and other comparative agents against carbapenem-non-susceptible Pseudomonas aeruginosa and Acinetobacter baumannii isolates associated from bloodstream infection in Taiwan between 2018-2020. J Microbiol Immunol Infect 2021; Epub ahead of print. [Crossref] [PubMed]

(English Language Editor: R. Scott)