Multidrug-resistant Gram-negative clinical isolates with reduced susceptibility/resistance to cefiderocol: which are the best present and future therapeutic alternatives?

PURPOSE

To evaluate the different present and future therapeutic β-lactam/β-lactamase inhibitor (BL/BLI) alternatives, namely aztreonam-avibactam, imipenem-relebactam, meropenem-vaborbactam, cefepime-zidebactam, cefepime-taniborbactam, meropenem-nacubactam, and sulbactam-durlobactam against clinical isolates showing reduced susceptibility or resistance to cefiderocol in Enterobacterales, Acinetobacter baumannii, and Pseudomonas aeruginosa.

METHODS

MIC values of aztreonam, aztreonam-avibactam, cefepime, cefepime-taniborbactam, cefepime-zidebactam, imipenem, imipenem-relebactam, meropenem, meropenem-vaborbactam, meropenem-nacubactam, sulbactam-durlobactam, and cefiderocol combined with a BLI were determined for 67, 9, and 11 clinical Enterobacterales, P. aeruginosa or A. baumannii isolates, respectively, showing MIC values of cefiderocol being ≥1 mg/L. If unavailable, the respective β-lactam breakpoints according to EUCAST were used for BL/BLI combinations.

RESULTS

For Enterobacterales, the susceptibility rates for aztreonam, cefepime, imipenem, and meropenem were 7.5%, 0%, 10.4%, and 10.4%, respectively, while they were much higher for cefepime-zidebactam (91%), cefiderocol-zidebactam (91%), meropenem-nacubactam (71.6%), cefiderocol-nacubactam (74.6%), and cefiderocol-taniborbactam (76.1%), as expected. For P. aeruginosa isolates, the higher susceptibility rates were observed for imipenem-relebactam, cefiderocol-zidebactam, and meropenem-vaborbactam (56% for all combinations). For A. baumannii isolates, lower susceptibility rates were observed with commercially or under development BL/BLI combos; however, a high susceptibility rate (70%) was found for sulbactam-durlobactam and when cefiderocol was associated to some BLIs.

CONCLUSIONS

Zidebactam- and nacubactam-containing combinations showed a significant in vitro activity against multidrug-resistant Enterobacterales clinical isolates with reduced susceptibility to cefiderocol. On the other hand, imipenem-relebactam and meropenem-vaborbactam showed the highest susceptibility rates against P. aeruginosa isolates. Finally, sulbactam-durlobactam and cefiderocol combined with a BLI were the only effective options against A. baumannii tested isolates.

Occurrence of plasmid-mediated fosfomycin resistance (fos genes) among Escherichia coli isolates, Portugal

OBJECTIVES

To evaluate the occurrence of plasmid-mediated fos genes among fosfomycin-resistant Escherichia coli isolates collected from patients in Lisbon, Portugal, and characterize the fos-positive strains.

METHODS

A total of 19 186 E. coli isolates were prospectively collected between April 2022 and January 2023 from inpatients and outpatients at a private laboratory in Lisbon. Fosfomycin resistance was initially assessed by semi-automated systems and further confirmed by the disc diffusion method. Resistant isolates were investigated for plasmid-mediated fos genes (fosA1-fosA10, fosC and fosL1-fosL2) and extended-spectrum beta-lactamases (ESBLs) by PCR and sequencing. Multilocus sequence typing was performed to evaluate the clonal relationship among fos-carrying isolates.

RESULTS

Out of the 19 186 E. coli isolates, 100 were fosfomycin-resistant (0.5%), out of which 15 carried a fosA-like gene (15%). The most prevalent fosfomycin-resistant determinant was fosA3 (n = 11), followed by fosA4 (n = 4). Among the 15 FosA-producing isolates, 10 co-produced an ESBL (67%), being either of CTX-M-15 (n = 8) or CTX-M-14 (n = 2) types. The fosA3 gene was carried on IncFIIA-, IncFIB-, and IncY-type plasmids, whereas fosA4 was always located on IncFIB-type plasmids. Most FosA4-producing isolates belonged to a single sequence type ST2161, whereas isolates carrying the fosA3 gene were distributed into nine distinct genetic backgrounds.

CONCLUSION

The prevalence of fosfomycin-resistant E. coli isolates is still low in Portugal. Notably, 15% of fosfomycin-resistant isolates harbour a transferable fosA gene, among which there is a high rate of ESBL producers, turning traditional empirical therapeutical options used in Portugal (fosfomycin and amoxicillin-clavulanic acid) ineffective.

Resist Acineto rapid immunological test for the detection of acquired carbapenemase producers among Acinetobacter spp

The Resist Acineto from Coris Bioconcept is a novel immunochromatographic test for detection of the major acquired carbapenemases (OXA-23, OXA-40, OXA-58, and NDM) identified in Acinetobacter spp. This rapid and easy-to-perform test showed an excellent specificity and sensitivity, with positive and negatives predictive values of 100% in both cases.

Rapid culture-based LNZ test for detection of linezolid susceptibility/resistance in staphylococci and enterococci

A rapid, easy-to-handle, cost-effective and universal culture-based test was developed for the identification of linezolid resistance among the most clinically relevant enterococcal and staphylococcal species. Our technique was tested using linezolid-resistant (n = 50) and linezolid-susceptible (n = 67) Gram-positive isolates: 34 Enterococcus faecium, 20 Enterococcus faecalis, 20 Staphylococcus aureus, 38 Staphylococcus epidermidis, and 5 Staphylococcus capitis. The susceptibility/resistance phenotype of E. faecium, E. faecalis, S. aureus, and S. epidermidis to linezolid was detected within 4.5 hours, while an extended timeframe was actually required for S. capitis (6.5 hours). The Rapid LNZ test showed a full agreement with the standard broth microdilution method, independently of the molecular resistance mechanism and MIC values, with sensitivities and specificities of 100% for all species.

ESBL- and Carbapenemase-Producing Escherichia coli and Klebsiella pneumoniae among Bivalves from Portuguese Shellfish Production Areas

Bivalves are filter-feeding organisms and biomarkers of bacterial pollution. Our study aimed to analyze the occurrence and characteristics of extended-spectrum β-lactamase (ESBL)- and carbapenemase-producing Escherichia coli among bivalves. A total of 522 bivalve samples were collected along Portuguese shellfish production areas. Homogenized samples were screened for E. coli contamination on corresponding selective plates, allowing for concomitant growth of Klebsiella pneumoniae. E. coli growth was observed in 39% of the samples. Subsequent selective screening identified nine samples (4.4%) contaminated with ESBL producers, corresponding to E. coli (n = 7) and K. pneumoniae (n = 2), while a single carbapenemase-producing K. pneumoniae (0.5%) was identified. ESBLs were all CTX-M-types commonly identified in human isolates, i.e., CTX-M-32 (n = 4), CTX-M-15 (n = 4), and CTX-M-14 (n = 1). The carbapenemase producer harbored the bla_GES-5 gene located on a ColE plasmid. Clonality was evaluated by multilocus sequence typing, identifying E. coli backgrounds as ST10, ST23, ST540, ST617, ST746, SLV206, and SLV2325, commonly identified among environmental and human strains. The K. pneumoniae isolates belonged to ST834, ST15, and DLV644. The occurrence of ESBL- and carbapenemase-producing Enterobacteriaceae in bivalves reveals how the marine environment constitutes a reservoir of critical bacterial pathogens, thus potentially representing a risk to human health.

Multiplex PCR for detection of acquired plasmid-borne fosfomycin resistance fos genes in Escherichia coli

A rapid (<3 hours) and reliable multiplex PCR was developed for detecting simultaneously known plasmid-mediated fos genes conferring acquired resistance to fosfomycin. Our technique was tested on a collection of Escherichia coli isolates previously identified as bearing the fosA-, fosC- and fosL-like genes, showing a sensitivity and a specificity of 100%.

Exploring the diet of arctic wolves (Canis lupus arctos) at their northern range limit

The grey wolf (Canis lupus Linnaeus, 1758) is one of the most widespread large carnivores on Earth, and occurs throughout the Arctic. Although wolf diet is well studied, we have scant information from high Arctic areas. Global warming is expected to increase the importance of predation for ecosystem regulation in Arctic environments. To improve our ability to manage Arctic ecosystems under environmental change, we therefore need knowledge about Arctic predator diets. Prey remains in 54 wolf scats collected at three sites in the high Arctic region surrounding the Hall Basin (Judge Daly Promontory, Ellesmere Island, Canada, and Washington Land and Hall Land, both in northwestern Greenland) pointed to a dietary importance of arctic hare (Lepus arcticus Ross, 1819; 55% frequency of occurrence) and muskoxen (Ovibos moschatus (Zimmermann, 1780); 39% frequency of occurrence), although we observed diet variation among the sites. A literature compilation suggested that arctic wolves (Canis lupus arctos Pocock, 1935) preferentially feed on caribou (Rangifer tarandus (Linnaeus, 1758)) and muskoxen, but can sustain themselves on arctic hares and Greenland collared lemmings (Dicrostonyx groenlandicus (Traill, 1823)) in areas with limited or no ungulate populations. We suggest that climate change may alter the dynamics among wolves, arctic hare, muskoxen, and caribou, and we encourage further studies evaluating how climate change influences predator–prey interactions in high Arctic environments.

Fluorescent Detection of Oral Pathogens by a Solid-Phase Immunoassay on PDMS

We have developed an array of sensors for the oral pathogen Streptococcus mutans (S. mutans) using an enzymelinked linked immunosorbent assay (ELISA) on a polydimethylsiloxane (PDMS) device. The model bacterial analyte, S. mutans, has been implicated in the initiation and progression of dental caries. The PDMS was modified with 3-aminopropyltriethoxysilance (APTS) and glutaraldehyde to covalently crosslink monoclonal anti-S. mutans immunoglobulin G (IgG) to the sensor surface. Successful IgG immobilization was verified by AFM and fluorescence imaging. Colloidal bacteria were captured on the sensor surface and labeled with immuno-active quantum dots (QDs), whose fluorescence was excited by an LED and detected by a CCD. The system was capable of detecting S. mutans concentrations as low as 6 10⁶cells/ml in a 20 &#956;l sample. This work represents a stable foundation for the development of a chair side diagnostic system capable of specific and sensitive detection of pathogens directly from oral fluid.

Flavonoid Rutin Alters the Viability and Function of Mitogen-Stimulated Splenocytes and Thymocytes Compared with Non Stimulated Cells

Rutin is a flavonoid obtained from Dimorphandra mollis (Benth.), a medicinal Brazilian plant used as antioxidative, antihemorrhagic, and blood vessel protector. The present study has examined its effects on the viability and function of immune system cells in vitro. Rat spleen and thymus cells were cultured with 10 nM, 1 microM, and 10 microM of the drug in the presence or absence of PWM, LPS, or ConA mitogens. Cellular proliferation was analyzed by H(3)-thymidin uptake and IFN-gamma and IL-10 were measured by ELISA after 48 and 72 hr. Viability was measured by flow cytometry using Annexin V and PI after 24 and 48 hr. The flavonoid rutin inhibited splenocytes and thymocytes proliferation under ConA stimulation observed by an increase on apoptosis levels of thymocytes stimulated with PWM in 24 hr and on splenocytes stimulated with PWM in 48 hr. Function studies showed a decrease on IFN-gamma production by splenocytes and thymocytes stimulated with PWM or ConA. Spleen cells cultured with LPS and rutin showed a decrease on apoptosis after 24 hr and an increase on the IL-10 levels after 48 hr. There was no significant variation on the necrosis rate, viability, and function of cells treated with rutin in the absence of mitogenic stimulus.

Role of Brazilian native medicinal plants on VEGF and PDGF receptors expression by glioblastoma cell line GL-15

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Background: Malignant gliomas are typically angiogenic and express greater amounts of angiogenic factors. Vascular endothelial growth factor (VEGF) and platelet derived growth factor (PDGF) are prominent glioblastoma-associated multifunctional cytokines that stimulate migration, invasion and angiogenesis. Their receptor inhibiton is considered an important target for anitumoral therapy. Flavonoids obtained from Dimorphandra mollis and Croton betulaster, native medicinal plants from Bahia-Brazil, have been described as proliferation inhibitors of a human glioblastoma derived cell line and reduce VEGF production by GL-15. In this study, VEGF and PDGF receptors expression by GL-15 cultures treated with bevacizumab and flavonoids were evaluated. Methods: GL-15 cultures were treated or not with pendulitin and rutin flavonoids (100μM) and bevacizumab (1μg/mL). After 24 hours VEGF and PDGF receptors were analyzed by flow cytometry using monoclonal antibodies labeled with FITC. Results: Flow cytometry showed that the GL-15 cells expressed PDGFR alfa (10%), PDGFR beta (52%), VEGFR 1 (26%) and VEGFR 2 (95%). It was observed that the pendulitin and rutin flavonoids treated cells showed a reduction on PDGFR alfa expression (2 and 1,6 % respectively) but the other receptors expression was similar to the non-treated or DMSO treated controls. Conclusions: GL-15 human glioblastoma derived cell line expresses receptors to the angiogenic cytokines studied. VEGFR 2 expression was predominant and bevacizumab didn’t alter the receptors production. Flavonoids extracted from D. mollis and C. betulaster seem to have an inhibitory action on the PDGRF alfa expression but not on the others receptors.

No significant financial relationships to disclose.

Different effects of arborinine alkaloid obtained from Brazilian Erthela baihensis on spleen and thymus cells stimulated in vitro with different mitogens

The present study has examined the effects of arborinine, an alkaloid obtained from Erthela bahiensis, a Brazilian plant popularly used as diuretic, antidiabetic, antithermic and expectorant, on the viability and function of immune system cells in vitro using a murine model. Rat spleen and thymus cells were cultured with 10 nM, 1 microM, 10 microM of the drug in the presence or absence of pokeweed (PWM), lipopolysaccharide (LPS), or concanavallin (ConA) mitogens. Cellular proliferation was analyzed by H3-thymidin uptake after 48 and 72 hr. Our results showed an inhibitory effect of arborinine on splenocytes proliferation under ConA or PWM stimulation and increased apoptosis on splenocytes and thymocytes stimulated with PWM in 24 hr. A decrease was observed on Interferon gamma (IFN-gamma) production by ConA- or LPS-stimulated splenocytes in 48 hr and 72 hr and ConA- or PWM-stimulated thymocytes in 72 hr. In contrast, an increase on lymphoproliferation was observed on LPS-stimulated splenocytes and ConA- or PWM-stimulated thymocytes in 48 hr. On this period, apoptosis decreased on LPS- or PWM-stimulated splenocytes and IFN-gamma production increased in PWM stimulated thymocytes. Arborinine also induced a decrease on Interleukin-10 production by splenocytes and thymocytes stimulated with ConA or PWM. There was no significant variation on the necrosis rate of the cells treated with arborinine or any change on their viability or function values in the absence of mitogenic stimulus.

In vitro IFN-gamma production by goat blood cells after stimulation with somatic and secreted Corynebacterium pseudotuberculosis antigens

Corynebacterium pseudotuberculosis is the causal agent of caseous lymphadenitis, a chronic illness that attacks goats and sheep characterized by pyogranulomas formation in lymph nodes and organs. Regarding the current knowledge of the pathogenesis of the caseous lymphadenitis, there is evidence that besides the humoral response the induction of a durable cellular response is fundamental for its control. In this sense, research on antigens of C. pseudotuberculosis that are capable to inducing cellular immunity is an important step for the development of diagnosis tests and more efficient vaccines. In the present study, the interferon-gamma production in cultures of whole blood from infected goats stimulated with secreted bacterial antigen or somatic antigen were used to evaluate the cellular response. The results demonstrated a significant difference in the ability of the two antigens to induce a cellular response. That is, IFN-gamma production was high with cells from infected animals in response to the secreted antigen while IFN-gamma production was low when somatic antigen was used. The concomitant use of these antigens with PWM also showed differences. That is, the secreted antigen increased the IFN-gamma production induced by PWM, while the somatic antigen seems not to have altered the response to PWM.

Vascular endothelial growth factor (VEGF) levels as a tool to discriminate between malignant and nonmalignant ascites

Ascites formation is commonly associated with cancer, although it is also present in other diseases. The aim of this study was to evaluate the usefulness of vascular endothelial growth factor as a malignancy marker in ascites of different etiologies. The levels of VEGF in 32 malignant and in 31 non-malignant ascites were determined by enzyme immunoassay (ELISA). VEGF levels were significantly higher in malignant than in non-malignant ascites (median=1265.9 pg/ml x 114.6 pg/ml; p<0.0001). We observed 72% sensitivity and 90% specificity, using 662 pg/ml as a cut-off value. Therefore, this approach can be used as a marker for a first screening to discriminate between malignant and nonmalignant ascites.

Tissue distribution of bovine spongiform encephalopathy agent in primates after intravenous or oral infection

BACKGROUND

The disease-associated form of prion protein (PrP(res)) has been noted in lymphoreticular tissues in patients with variant Creutzfeldt-Jakob disease (vCJD). Thus, the disease could be transmitted iatrogenically by surgery or use of blood products. We aimed to assess transmissibility of the bovine spongiform encephalopathy (BSE) agent to primates by the intravenous route and study its tissue distribution compared with infection by the oral route.

METHODS

Cynomolgus macaques were infected either intravenously or orally with brain homogenates from first-passage animals with BSE. They were clinically monitored for occurrence of neurological signs and killed humanely at the terminal stage of the disease. Brain, lymphoreticular tissues, digestive tract, and peripheral nerves were obtained and analysed by sandwich ELISA and immunohistochemistry for quantitative and qualitative assessment of their PrP(res) content.

FINDINGS

Incubation periods after intravenous transmission of BSE were much shorter than after oral infection. We noted that PrP(res) was present in lymphoreticular tissues such as spleen and tonsils and in the entire gut from the duodenum to the rectum. In the gut, PrP(res) was present in Peyer's patches and in the enteric nervous system and nerve fibres of intestinal mucosa. Furthermore, PrP(res) was found in locomotor peripheral nerves and the autonomic nervous system. Amount of PrP(res) ranged from 0.02% to more than 10% of that recorded in brain. Distribution of PrP(res) was similar in animals infected by the intravenous or oral route.

INTERPRETATION

Our findings suggest that the possible risk of vCJD linked to endoscopic procedures might be currently underestimated. Human iatrogenic vCJD cases infected intravenously raise the same public-health concerns as primary cases and need the same precautionary measures with respect to blood and tissue donations and surgical procedures.

Removal of cadmium and mercury ions from aqueous solution by sorption on treated Pinus pinaster bark: kinetics and isotherms

Formaldehyde pretreated Pinus pinaster bark was used to sorb Cd2+ and Hg2+ from aqueous solutions. The sorption kinetics showed hyperbolic dependence of the proportion of cation adsorbed on time, and the sorption isotherms were satisfactorily fitted by Freundlich equations, with k and n values showing Hg2+ to be more efficiently sorbed than Cd2+. Except for low cation concentrations, for which sorption was practically total at all initial pH > or = 6, sorption increased in this range, in keeping with a mechanism based on ion exchange with the hydroxyl protons of ring B of the procyanidin units of the tannins in the bark.

Preliminary studies on TCF bleaching of Pinus pinaster acetosolv pulps

Oxygen pre-treatment of Pinus pinaster acetosolv pulps has been studied as a first step towards TCF bleaching. Using a 2(3) factorial design, the influence of temperature (80-120 degrees C), time (1-2 h) and NaOH concentration (1.5-3%) on pulp yield in the oxygen stage, chemical composition and physical properties of the pulps obtained was studied. Pulps pre-bleached with oxygen in the conditions selected as optimal (80 degrees C, 1 h with 2.25% NaOH) have been bleached with TCF sequences which included stages with hydrogen peroxide or hydrogen peroxide-oxygen under pressure. Even if high degrees of delignification were reached, with a reduction in Kappa number up to 95% and without important loss of viscosity, the carbohydrates degradation, especially hemicelluloses in the acetic acid delignification, reduces the strength potential of the pulps.