Effect of Platelet Parameters on Linezolid-Related Thrombocytopenia in Hospitalized Patients

Background

Linezolid-induced thrombocytopenia incidence varies considerably. Linezolid-related thrombocytopenia in patients has received few studies which have investigated risk factors including platelet parameters except for platelet counts. The study aims to analyze the effect of platelet parameters, including mean platelet volume and platelet large cell ratio, on linezolid-related thrombocytopenia in patients.

Methods

The effect of platelet parameters on linezolid-related thrombocytopenia was identified by univariate and multivariate logistic regressions. A Kaplan-Meier survival analysis was carried out to compare the survival of patients who developed linezolid-related thrombocytopenia with patients who did not.

Results

Thrombocytopenia occurred at a rate of 41.5% (66/159) after linezolid therapy in hospitalized patients. Platelet parameters, including the difference in mean platelet volume (MPV/fL=0.08 (-1.2-0.9)vs-0.5 (-1.5-0.3), (OR, 0.459; P = 0.001), the difference in platelet large cell ratio (PLCR/fL=0.9 (-5.1-6.2)vs-3.8 (-8.6-2.4), (OR, 1.156; P = 0.001), baseline platelet counts (OR, 0.995; P = 0.006) and duration of linezolid therapy≥10d (OR, 1.346; P = 0.007), were significantly associated with linezolid-related thrombocytopenia in hospitalized patients. In addition, other risk factors which also are associated with linezolid-related thrombocytopenia include baseline red blood cells, co-medication with parecoxib and co-medication with caspofungin. Accumulated in-hospital mortality of patients with thrombocytopenia was significantly higher than that of patients without thrombocytopenia during linezolid treatment (19.7% vs 8.6%, P = 0.003).

Conclusion

The difference in mean platelet volume, the difference in large platelet ratio, baseline platelet counts and duration of linezolid therapy≥10d significantly affected the development of linezolid-related thrombocytopenia in hospitalized patients.

The Properties of Linezolid, Rifampicin, and Vancomycin, as Well as the Mechanism of Action of Pentamidine, Determine Their Synergy against Gram-Negative Bacteria

Combining pentamidine with Gram-positive-targeting antibiotics has been proven to be a promising strategy for treating infections from Gram-negative bacteria (GNB). However, which antibiotics pentamidine can and cannot synergize with and the reasons for the differences are unclear. This study aimed to identify the possible mechanisms for the differences in the synergy of pentamidine with rifampicin, linezolid, tetracycline, erythromycin, and vancomycin against GNB. Checkerboard assays were used to detect the synergy of pentamidine and the different antibiotics. To determine the mechanism of pentamidine, fluorescent labeling assays were used to measure membrane permeability, membrane potential, efflux pump activity, and reactive oxygen species (ROS); the LPS neutralization assay was used to evaluate the target site; and quantitative PCR was used to measure changes in efflux pump gene expression. Our results revealed that pentamidine strongly synergized with rifampicin, linezolid, and tetracycline and moderately synergized with erythromycin, but did not synergize with vancomycin against E. coli, K. pneumoniae, E. cloacae, and A. baumannii. Pentamidine increased the outer membrane permeability but did not demolish the outer and inner membranes, which exclusively permits the passage of hydrophobic, small-molecule antibiotics while hindering the entry of hydrophilic, large-molecule vancomycin. It dissipated the membrane proton motive force and inactivated the efflux pump, allowing the intracellular accumulation of antimicrobials that function as substrates of the efflux pump, such as linezolid. These processes resulted in metabolic perturbation and ROS production which ultimately was able to destroy the bacteria. These mechanisms of action of pentamidine on GNB indicate that it is prone to potentiating hydrophobic, small-molecule antibiotics, such as rifampicin, linezolid, and tetracycline, but not hydrophilic, large-molecule antibiotics like vancomycin against GNB. Collectively, our results highlight the importance of the physicochemical properties of antibiotics and the specific mechanisms of action of pentamidine for the synergy of pentamidine-antibiotic combinations. Pentamidine engages in various pathways in its interactions with GNB, but these mechanisms determine its specific synergistic effects with certain antibiotics against GNB. Pentamidine is a promising adjuvant, and we can optimize drug compatibility by considering its functional mechanisms.

A cost minimisation analysis comparing oral linezolid and intravenous daptomycin administered via an outpatient parenteral antibiotic therapy programme in patients requiring prolonged antibiotic courses

This study is an economic analysis seeking to examine cost savings that may be accrued from usage of oral linezolid in place of OPAT IV daptomycin in patients requiring prolonged courses of IV or highly bioavailable oral antibiotic therapy. In order to do so we conducted a literature review to establish the scenarios in which the agents could be considered equivalent. We then, using a decision-tree model, conducted a cost analysis to establish differences in cost between the approaches. Under the model base-case, the total cost of treatment with OPAT daptomycin was €3,496.84 and the total cost of treatment with oral linezolid was €772.01. Therefore the oral linezolid strategy would be projected to save the Irish health service €2,724.83 per patient. These results were robust to one-way deterministic sensitivity analyses and probabilistic sensitivity analysis. Our study suggests that significant savings could be safely accrued in the management of these patients.

Comparative Study of Linezolid and Vancomycin Regimens in One-Stage Surgery for Treating Limb Traumatic Osteomyelitis Caused by Methicillin-Resistant Staphylococcus aureus

To compare the clinical outcomes of linezolid and vancomycin regimens combined with one-stage surgery in treating traumatic osteomyelitis of the limbs caused by methicillin-resistant Staphylococcus aureus (MRSA) infection. A retrospective study was performed to analyze patients with traumatic osteomyelitis of the limbs attributable to MRSA infection. All of these patients received one-stage surgery to debride their wounds, with subsequent implantation of a vancomycin-loaded calcium sulfate artificial bone. Patients received either intravenous linezolid (study group) or vancomycin (control group) during the perioperative period. The postoperative inflammatory markers, renal function, duration of drainage catheter placement, duration of antibiotic administration, length of hospital stay, adverse events, and recurrence of osteomyelitis in these two groups were compared. The study group had a shorter duration of antibiotic administration and length of hospital stay (p < 0.05). There was a significant difference in the incidences of adverse events between the two groups (5.88% and 17.65% in the study and control groups, respectively, p < 0.05). There was no recurrence in either group during the three-year follow-up period. As of year, five after the surgery, one patient in the control group had a recurrence of osteomyelitis. The linezolid regimen should be preferred to the vancomycin regimen in patients with traumatic osteomyelitis of the extremities caused by MRSA infection because the linezolid regimen showed fewer adverse events, shorter periods of antibiotic use, and shorter hospital stay. However, both treatment regimens achieved satisfactory outcomes and warranted further investigations.

Combination effects of baicalin with linezolid against Staphylococcus aureus biofilm-related infections: in vivo animal model

Staphylococcus aureus is a gram-positive bacterium that can produce biofilm, and biofilm-associated infections are difficult to control. Biofilm prevents antibiotics from penetrating and killing the bacteria. Combined use of antimicrobials is a common strategy to treat S. aureus biofilm-related infections. In this in vivo study, the clinically isolated strain of S. aureus 17546 (t037) was selected to establish a biofilm-associated infection rat model, and baicalin and linezolid were used to treat the infection. CFU counting was used to determine the bacteria within the biofilm, the biofilm structure was viewed using scanning electron microscopy (SEM), histopathology was performed, and inflammatory factors were analyzed by ELISA. Baicalin was efficient in destroying the biofilm and exerted a synergistic bactericidal effect when combined with linezolid. Based on these findings, baicalin combined with linezolid may be efficacious in controlling S. aureus biofilm-related infections.

Inhibition of S. aureus biofilm formation by linezolid alleviates sepsis-induced lung injury caused by S. aureus infection through direct inhibition of icaA activity

Antibiotic-resistant S. aureus infections can be life-threatening. Linezolid is known to hinder S. aureus biofilm formation, but the underlying molecular mechanism remains unclear. Molecular docking revealed that linezolid can bind to icaA, and this was confirmed by thermal drift assays. Linezolid demonstrated a dose-dependent inhibition of icaA enzyme activity. Mutating Trp267, a key residue identified through molecular docking, significantly decreased linezolid binding and inhibitory effects on mutant icaA activity. However, the mutant icaA Trp267Ala showed only slight activity reduction compared to icaA. Linezolid had minimal impact on icaB's thermal stability and activity. The 50S ribosomal L3ΔSer145 mutant S. aureus exhibited similar growth and biofilm formation to the wild-type strain. Linezolid effectively suppressed the growth and biofilm formation of wildtype S. aureus. Although linezolid lost its ability to inhibit the growth of the mutant strain, it still effectively hindered its biofilm formation. Linezolid exhibited weaker attenuation of sepsis-induced lung injury caused by 50S ribosomal L3ΔSer145 mutant S. aureus compared to wild-type S. aureus. These findings indicate that linezolid hampers S. aureus biofilm formation by directly inhibiting icaA activity, independently of its impact on bacterial growth.

[Translated article] Influence of augmented renal clearance in the lower incidence of linezolid-related haematological toxicity

OBJECTIVES

Linezolid is an oxazolidin commonly related to the development of haematological toxicity, being renal clearance the major factor involved in the drug clearance. The aim of this study is to evaluate the influence of increased filtration rates in the incidence of linezolid-induced haematological toxicity by comparing augmented renal clearance (ARC) patients versus normal renal function patients.

MATERIAL AND METHODS

A retrospective, observational study was conducted on hospitalized patients treated with linezolid for 5 days or more during 2014-2019 period. Patients with a filtration rate of ≥130 mL/min versus reference patients (60-90 mL/min) were compared. Haematological toxicity was defined as a decrease of 25% in platelets, of 25% in haemoglobin, and/or 50% in neutrophils from baseline. Toxicity relevance was classified according to Common Terminology Criteria for Adverse Events v5. Incidence of haematological toxicity between groups was studied by chi-square and Fisher test. Furthermore, percentage diminution of all 3 parameters was calculated and compared by Mann-Whitney test and treatment interruption and transfusion requirements were registered.

RESULTS

30 ARC patients and 38 reference patients were included. Haematological toxicity was observed in 16.66% of ARC patients vs 44.74% of reference patients (P=.014); thrombocytopenia in 13.33% vs 36.84% (P=.051), anaemia in 3.3% vs 10.52% (P=.374) and neutropenia in 10% vs 23.68% (P=.204). Median percentage of platelets decrease in ARC patients was -10.36 (-193.33-62.03) vs 2.68 (-163.16-82.71) in reference patients (P=.333), while haemoglobin decrease was 2.50 (-12.12-25.93) vs 9.09 (-17.72-30.63) (P=.047) and neutrophils decrease was 9.14 (-73.91-76.47) vs 27.33 (-86.66-90.90) (P=.093). 10.5% of normal renal function patients reported at least 1 adverse event grade 3 or superior while 2.6% of them interrupted treatment and 5.2% had transfusion requirements. No major events or interruptions were reported in ARC patients.

CONCLUSION

Our findings suggest a lower incidence and clinical relevance of haematological toxicity in augmented renal clearance patients. Thrombocytopenia was the major event in both populations. This might be related to a lower exposure to the drug due to the higher clearance and likely lower therapeutic efficiency. These results suggest a potential benefit of therapeutic drug monitoring on high risk patients.

Favourable outcomes in RR-TB patients using BPaL and other WHO-recommended second-line anti-TB drugs

SETTING: According to reports in South Africa, treatment failure rates for rifampicin-resistant TB (RR-TB) are significant and below the WHO target of ≥70%. HIV infection and the use of highly active antiretroviral therapy (HAART) influence how patients receiving anti-TB drugs respond to therapy. In the treatment of RR-TB, more recent medications, including bedaquiline, pretomanid and linezolid (BPaL), have shown promising results.OBJECTIVE: To assess treatment outcomes in RR-TB patients using BPaL and other second-line anti-TB drugs as recommended by the WHO in the South African population.DESIGN: The databases Medline, PubMed, Google Scholar and Embase were searched for studies between 2015 and 2022, which investigated BPaL outcomes in South Africa.RESULTS: Of the 27,259 participants, 21% were on bedaquiline, 1% were taking pretomanid and 9% were taking linezolid as part of their background regimen. About 68% of the patients were HIV-positive, with 59% of them taking HAART.CONCLUSION: Overall, 66% of patients taking BPaL drugs as part of their background regimen had favourable treatment outcomes. Additionally, patients with RR-TB who were HIV-positive and taking HAART while receiving BPaL drugs as part of a background regimen had improved treatment outcomes.

Successful Treatment of Infective Endocarditis With Oral Antibiotics: A Case Report

Infective endocarditis (IE) is a serious and potentially life-threatening infection of the heart valves. It is commonly treated with prolonged courses of intravenous antibiotics, and in some cases, surgical intervention may also be necessary. While the use of oral antibiotics in the treatment of IE is generally limited, there are select cases where they may be considered as an alternative treatment option. Here, we report a case of staphylococcal right-sided IE successfully treated with oral antibiotics (linezolid and rifampicin). Our case highlights the potential for oral antibiotics to be used as step-down therapy for select patients with IE.

Linezolid induced hypoglycemia and anemia: A case report

Key Clinical Message

Linezolid (LZD) is an efficient addition antibiotic against multidrug-resistant strains. However, clinicians should pay attention to the adverse reactions such as hypoglycemia and anemia in using LZD, especially in elderly patients and patients with abnormal liver and kidney function who need to use LZD for a long time.

Abstract

Severe hypoglycemia and anemia caused by linezolid (LZD) are rare, with potentially serious adverse effects. The report of LZD-induced hypoglycemia and anemia is extremely rare. Thus far, this is the first report. We presented LZD-induced recurrent hypoglycemia and anemia in a 93-year-old patient who has been prescribed LZD 600 mg once daily for 42 days for treatment of tuberculosis (TB) pleurisy and pneumonia. The patient began to experience recurrent hypoglycemic episodes and anemia 5 days and 2 weeks after LZD medication, respectively. Using Naranjo's Adverse Drug Reaction Assessment Scale, the patient scored 8 points with the category of "probable". His hypoglycemia and anemia gradually improved 1 month after LZD withdrawal. Clinicians should pay attention to the adverse reactions such as hypoglycemia and anemia in using LZD, especially in elderly patients and patients with abnormal liver and kidney function who need to use LZD for a long time. Patients should regularly monitor blood routine, blood glucose, and liver and kidney functions during LZD exposure, which may avoid adverse reactions and improve their prognosis.

Successful Treatment of Cutibacterium acnes Prosthetic Joint Infection With Single-Stage Exchange and Oral Antibiotics

Interest has grown in less invasive surgical treatment and early use of oral antibiotics in the treatment of Cutibacterium acnes prosthetic joint infection. We report a series of patients who were successfully treated with single-stage exchange and an all-oral course of rifampin and linezolid.

Detection of Genes Related to Linezolid Resistance (poxtA, cfr, and optrA) in Clinical Isolates of Enterococcus spp. from Humans: A First Report from Iran

Background

Enterococci may develop resistance to linezolid through chromosomal mutations that involve specific linezolid resistance genes, such as cfr, optrA, and poxtA. The objective of this study was to evaluate the antibiotic susceptibility of enterococcal isolates and identify cfr, optrA, and poxtA genes in MDR isolates.

Materials and Methods

Enterococcal isolates were collected from various clinical specimens at Al-Zahra, Amin, and Khorshid Hospitals in Isfahan. The Enterococcus isolates were identified as belonging to the E. faecalis and E. faecium species by using specific gene (D alanine D alanine ligase ddl) sets in PCR. To detect cfr, optrA, and poxtA genes among the species, a multiplex-PCR assay was performed.

Results

Out of 175 isolates, E. faecalis predominated 129/175 (73.7%). Furthermore, the prevalence of vancomycin-resistant Enterococci (VRE) and linezolid-resistant Enterococci (LRE) was 29.7% and 4%, respectively. The overall prevalence of MDR was 91.1%, 68.9%, and 66.6% of E. faecium, E. faecalis, and other Enterococcus spp., respectively. Interestingly, the frequency of optrA (71.4%) in E. faecium and poxtA and crf (42.8%) in E. faecalis were detected among LRE species. A statistically significant relationship (P < 0.05) was found between the presence of the three genes and the occurrence of LRE.

Conclusion

This is the first study to report the detection of linezolid resistance genes (cfr, optrA, and poxtA) in clinical Enterococcus spp. isolates from Iran, conducted at Isfahan University of Medical Sciences hospitals. The emergence of enterococcal strains that resist linezolid is concerning as it can lead to the spread of resistant strains among patients, resulting in treatment failure.

Two-Stage Revision Arthroplasty for Resistant Gram-Positive Periprosthetic Joint Infections Using an Oral Linezolid-Based Antibiotic Regime

BACKGROUND

Increasing antibiotic resistance has been reported as an issue in the systemic treatment of periprosthetic joint infection (PJI). Linezolid offers the advantages of high oral bioavailability and little resistance; however, efficacy in the treatment of PJI varies considerably, and studies reporting consistent surgical treatment are scarce.

METHODS

This is a retrospective, single-center analysis of two-stage revisions performed between 2008 and 2017. We identified 111 patients who met the inclusion criteria. Oral linezolid was given for 28 days following 14 days of intravenous tailored antibiotics in resistant gram-positive PJI. A total of 64% of the patients had methicillin-resistant coagulase-negative staphylococci. The median follow-up was 43 (interquartile range (IQR) 30-57) months.

RESULTS

22% (24/111) of the patients underwent surgery for subsequent infection. The 5-year infection-free survival probability was 77% (95% confidence interval (CI) 69-85). A total of 5% of the patients (6/111) had the same organism at the time of reinfection. The patients with infections caused by other organisms than Coagulase-negative staphylococci tended to have a worse reinfection-free survivorship at five years (70% vs. 81%, p = 0.09). Furthermore, the patients with obesity tended to have reduced reinfection-free survivorship at five years (69% vs. 84%, p = 0.08). Overall, 5% (6/111) of the patients had blood count abnormalities with no treatment discontinuations.

CONCLUSION

Two-stage revision arthroplasty with systemic oral linezolid treatment for resistant gram-positive PJI results in an infection control of 77% at the mid-term.

Therapeutics for Vancomycin-Resistant Enterococcal Bloodstream Infections

Vancomycin-resistant enterococci (VRE) are common causes of bloodstream infections (BSIs) with high morbidity and mortality rates. They are pathogens of global concern with a limited treatment pipeline. Significant challenges exist in the management of VRE BSI, including drug dosing, the emergence of resistance, and the optimal treatment for persistent bacteremia and infective endocarditis. Therapeutic drug monitoring (TDM) for antimicrobial therapy is evolving for VRE-active agents; however, there are significant gaps in the literature for predicting antimicrobial efficacy for VRE BSIs. To date, TDM has the greatest evidence for predicting drug toxicity for the three main VRE-active antimicrobial agents daptomycin, linezolid, and teicoplanin. This article presents an overview of the treatment options for VRE BSIs, the role of antimicrobial dose optimization through TDM in supporting clinical infection management, and challenges and perspectives for the future.

Prevalence and risk factors for severe linezolid-associated thrombocytopenia in pediatric patients: An analysis of a public database

Linezolid is widely used in various clinical settings. Studies have revealed that it may cause thrombocytopenia in adults. However, the correlation between the use of linezolid and thrombocytopenia in pediatric patients is still unclear. This study aimed to identify the impact of Linezolid on the occurrence of thrombocytopenia in children. A retrospective observational study was conducted using data on patients treated with linezolid from the Pediatric Intensive Care clinical database. Univariate and multiple logistic regression analyses were performed to identify the risk factors of linezolid-related severe thrombocytopenia. A total of 134 patients were included. The prevalence of severe thrombocytopenia was 8.96% (12/134). Univariate analysis indicated that the severe thrombocytopenia group showed significantly higher proportion of concomitant carbapenem (75% vs 44.3%; P < .05) and piperacillin/tazobactam (25% vs 6.6%; P < .05) than that of the non-severe thrombocytopenia group. Multivariate analysis also revealed that the occurrence of severe thrombocytopenia was significantly associated with concurrent use of carbapenem (odd ratio = 4.058; 95% confidence interval: 1.012-16.274; P = .048) and piperacillin/tazobactam (odd ratio = 5.335; 95% confidence interval: 1.117-25.478; P = .036). 75% of patients (9/12) developed severe thrombocytopenia within the first 7 days of linezolid use. The concomitant use of carbapenem and piperacillin/tazobactam was associated with an increased probability of severe thrombocytopenia in pediatric patients undergoing linezolid treatment. Further prospective clinical studies are required, and more detailed mechanisms of blood toxicity in pediatric patients must be investigated.

Linezolid-Resistant Enterococcus faecalis of Chicken Origin Harbored Chromosome-Borne optrA and Plasmid-Borne cfr, cfr(D), and poxtA2 Genes

The aim of this study was to investigate the transferability of acquired linezolid resistance genes and associated mobile genetic elements in an Enterococcus faecalis isolate QZ076, cocarrying optrA, cfr, cfr(D), and poxtA2 genes. MICs were determined by broth microdilution. Whole-genome sequencing (WGS) was performed using the Illumina and Nanopore platforms. The transfer of linezolid resistance genes was investigated by conjugation, using E. faecalis JH2-2 and clinical methicillin-resistant Staphylococcus aureus (MRSA) 109 as recipients. E. faecalis QZ076 harbors four plasmids, designated pQZ076-1 to pQZ076-4, with optrA located in the chromosomal DNA. The gene cfr was located on a novel pseudocompound transposon, designated Tn7515, integrated into the 65,961-bp pCF10-like pheromone-responsive conjugative plasmid pQZ076-1. Tn7515 generated 8-bp direct target duplications (5'-GATACGTA-3'). The genes cfr(D) and poxtA2 were colocated on the 16,397-bp mobilizable broad-host-range Inc18 plasmid pQZ076-4. The cfr-carrying plasmid pQZ076-1 could transfer from E. faecalis QZ076 to E. faecalis JH2-2, along with the cfr(D)- and poxtA2-cocarrying plasmid pQZ076-4, conferring the corresponding resistant phenotype to the recipient. Moreover, pQZ076-4 could also transfer to MRSA 109. To the best of our knowledge, this study presented the first report of four acquired linezolid resistance genes [optrA, cfr, cfr(D), and poxtA2] being simultaneously present in the same E. faecalis isolate. The location of the cfr gene on a pseudocompound transposon in a pheromone-responsive conjugative plasmid will accelerate its rapid dissemination. In addition, the cfr-carrying pheromone-responsive conjugative plasmid in E. faecalis was also able to mobilize the interspecies transfer of the cfr(D)- and poxtA2-cocarrying plasmid between enterococci and staphylococci. IMPORTANCE In this study, the simultaneous occurrence of four acquired oxazolidinone resistance genes [optrA, cfr, cfr(D), and poxtA2] was identified in an E. faecalis isolate of chicken origin. The association of the cfr gene with a novel pseudocompound transposon Tn7515 integrated into a pCF10-like pheromone-responsive conjugative plasmid will accelerate its dissemination. Moreover, the location of the resistance genes cfr(D) and poxtA2 on a mobilizable broad-host-range Inc18 family plasmid represents the basis for their intra- and interspecies dissemination with the aid of a conjugative plasmid and further accelerates the spreading of acquired oxazolidinone resistance genes, such as cfr, cfr(D), and poxtA2, among Gram-positive pathogens.

When Combined with Pentamidine, Originally Ineffective Linezolid Becomes Active in Carbapenem-Resistant Enterobacteriaceae

The increasing prevalence of carbapenem-resistant Enterobacteriaceae (CRE) and their biofilm-relevant infections pose a threat to public health. The drug combination strategy provides a new treatment option for CRE infections. This study explored the synergistic antibacterial, antibiofilm activities as well as the in vivo efficacy against CRE of pentamidine combined with linezolid. This study further revealed the possible mechanisms underlying the synergy of the combination. The checkerboard and time-kill assays showed that pentamidine combined with linezolid had significant synergistic antibacterial effects against CRE strains (9/10). Toxicity assays on mammal cells (mouse RAW264.7 and red blood cells) and on Galleria mellonella confirmed that the concentrations of pentamidine and/or linezolid that were used were relatively safe. Antibiofilm activity detection via crystal violet staining, viable bacteria counts, and scanning electron microscopy demonstrated that the combination enhanced the inhibition of biofilm formation and the elimination of established biofilms. The G. mellonella infection model and mouse thigh infection model demonstrated the potential in vivo efficacy of the combination. In particular, a series of mechanistic experiments elucidated the possible mechanisms for the synergy in which pentamidine disrupts the outer membranes, dissipates the membrane potentials, and devitalizes the efflux pumps of CRE, thereby facilitating the intracellular accumulation of linezolid and reactive oxygen species (ROS), which ultimately kills the bacteria. Taken together, when combined with pentamidine, which acts as an outer membrane permeabilizer and as an efflux pump inhibitor, originally ineffective linezolid becomes active in CRE and exhibits excellent synergistic antibacterial and antibiofilm effects as well as a potential therapeutic effect in vivo on CRE-relevant infections. IMPORTANCE The multidrug resistance and biofilm formation of Gram-negative bacteria (GNB) may lead to incurable "superbug" infections. Drug combinations, with the potential to augment the original treatment ranges of drugs, are alternative treatment strategies against GNB. In this study, the pentamidine-linezolid combination showed notable antibacterial and antibiofilm activity both in vitro and in vivo against the problem carbapenem-resistant Enterobacteriaceae (CRE). Pentamidine is often used as an antiprotozoal and antifungal agent, and linezolid is a defensive Gram-positive bacteria (GPB) antimicrobial. Their combination expands the treatment range to GNB. Hence, the pentamidine-linezolid pair may be an effective treatment for complex infections that are mixed by GPB, GNB, and even fungi. In terms of mechanism, pentamidine inhibited the outer membranes, membrane potentials, and efflux pumps of CRE. This might be a universal mechanism by which pentamidine, as an adjuvant, potentiates other drugs, similar to linezolid, thereby having synergistic antibacterial effects on CRE.

Oxazolidinone resistance genes in florfenicol-resistant enterococci from beef cattle and veal calves at slaughter

Background

Linezolid is a critically important oxazolidinone antibiotic used in human medicine. Although linezolid is not licensed for use in food-producing animals, the use of florfenicol in veterinary medicine co-selects for oxazolidinone resistance genes.

Objective

This study aimed to assess the occurrence of cfr, optrA, and poxtA in florfenicol-resistant isolates from beef cattle and veal calves from different herds in Switzerland.

Methods

A total of 618 cecal samples taken from beef cattle and veal calves at slaughter originating from 199 herds were cultured after an enrichment step on a selective medium containing 10 mg/L florfenicol. Isolates were screened by PCR for cfr, optrA, and poxtA which are genes known to confer resistance to oxazolidinones and phenicols. One isolate per PCR-positive species and herd was selected for antimicrobial susceptibility testing (AST) and whole-genome sequencing (WGS).

Results

Overall, 105 florfenicol-resistant isolates were obtained from 99 (16%) of the samples, corresponding to 4% of the beef cattle herds and 24% of the veal calf herds. Screening by PCR revealed the presence of optrA in 95 (90%) and poxtA in 22 (21%) of the isolates. None of the isolates contained cfr. Isolates included for AST and WGS analysis were Enterococcus (E.) faecalis (n = 14), E. faecium (n = 12), E. dispar (n = 1), E. durans (n = 2), E. gallinarum (n = 1), Vagococcus (V.) lutrae (n = 2), Aerococcus (A.) urinaeequi (n = 1), and Companilactobacillus (C.) farciminis (n = 1). Thirteen isolates exhibited phenotypic linezolid resistance. Three novel OptrA variants were identified. Multilocus sequence typing identified four E. faecium ST18 belonging to hospital-associated clade A1. There was a difference in the replicon profile among optrA- and poxtA-harboring plasmids, with rep9 (RepA_N) plasmids dominating in optrA-harboring E. faecalis and rep2 (Inc18) and rep29 (Rep_3) plasmids in poxtA-carrying E. faecium.

Conclusion

Beef cattle and veal calves are reservoirs for enterococci with acquired linezolid resistance genes optrA and poxtA. The presence of E. faecium ST18 highlights the zoonotic potential of some bovine isolates. The dispersal of clinically relevant oxazolidinone resistance genes throughout a wide variety of species including Enterococcus spp., V. lutrae, A. urinaeequi, and the probiotic C. farciminis in food-producing animals is a public health concern.

Ampicillin-resistant and vancomycin-susceptible Enterococcus faecium bacteremia: a clinical narrative review

INTRODUCTION

Enterococcus faecium is a commensal microorganism that can cause infections such as bacteremia. Incidence of ampicillin-resistant and vancomycin-susceptible E. faecium (EfARSV) bacteremia is on the rise, and the mortality rate is high. Despite much data, the most appropriate treatment remains a question.

AREAS COVERED

This article mostly reviews the relevant aspects of EfARSV bacteremia: microbiology, gastrointestinal tract colonization and invasion, antibiotic resistance, epidemiology, risk factors, mortality, and treatment, including pharmacologic components of employed agents and related clinical evidence. A literature search was conducted on PubMed on 31 July 2022, which was updated on 15 November 2022.

EXPERT OPINION

EfARSV bacteremia presents high mortality. However, it is uncertain whether mortality is attributable to or a marker of severity/comorbidities. Considering its antibiotic resistance pattern, EfARSV is considered a difficult-to-treat microorganism. Glycopeptides have been used to treat EfARSV, with linezolid and daptomycin serving as potential alternative agents. Yet, the use of daptomycin is controversial due to a higher risk of treatment failures. Clinical evidence on this issue is scarce, unfortunately, and subject to many limitations. Despite increased incidence and mortality, EfARSV bacteremia presents multiple aspects to be addressed in well-conducted studies.

Analysis of Dynamic Efficacy Endpoints of the Nix-TB Trial

BACKGROUND

Safer, better, and shorter treatments for multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) are an urgent global health need. The phase 3 clinical trial Nix-TB (NCT02333799) tested a 6-month treatment of MDR and XDR-TB consisting of high-dose linezolid, bedaquiline, and pretomanid (BPaL). In this study, we investigate the relationship between the pharmacokinetic characteristics of the drugs, patient characteristics and efficacy endpoints from Nix-TB.

METHODS

Pharmacokinetic data were collected at weeks 2, 8, and 16. Efficacy endpoints including treatment outcomes, time to stable culture conversion, and longitudinal time to positivity in the mycobacterial growth indicator tube assay were each characterized using nonlinear mixed-effects modeling. Relationships between patient, treatment pharmacokinetics, and disease characteristics and efficacy endpoints were evaluated.

RESULTS

Data from 93 (85% of the total) participants were analyzed. Higher body mass index was associated with a lower incidence of unfavorable treatment outcomes. Median time to stable culture conversion was 3 months in patients with lower baseline burden compared with 4.5 months in patients with high baseline burden. Participants with minimal disease had steeper time to positivity trajectories compared with participants with high-risk phenotypes. No relationship between any drugs' pharmacokinetics (drug concentration or exposure metrics) and any efficacy outcomes was observed.

CONCLUSIONS

We have successfully described efficacy endpoints of a BPaL regimen from the Nix-TB trial. Participants with high-risk phenotypes significantly delayed time to culture conversion and bacterial clearance. The lack of a relationship between pharmacokinetic exposures and pharmacodynamic biomarkers opens the possibility to use lower, safer doses, particularly for toxicity-prone linezolid.

CLINICAL TRIALS REGISTRATION

NCT02333799.

Linezolid-induced black hairy tongue in a patient treated for idiopathic granulomatous mastitis: a case report

Linezolid-induced black hairy tongue (BHT) is a highly scarce adverse event of linezolid therapy. To date, there are very few reported cases in contemporary literature. The onset and mechanism of BHT are also not well understood.

Case report

In this article, the authors report a case of BHT in a 28-year-old female following 5 days of therapy with linezolid. The patient recovered well within few days of discontinuation of the drug and maintaining oral hygeine. Patient reassurance and counselling was integral to the management.

Discussion and conclusion

This case report and review depict a rare adverse effect of linezolid and discuss its clinical implications aiding healthcare professionals in an early diagnosis and cromulent management strategy. The authors also present a compilation of previously reported literature on linezolid-induced BHT to support the discussion.

Frequency of mutations in erm(39) related to clarithromycin resistance and in rrl related to linezolid resistance in clinical isolates of Mycobacterium fortuitum in Iran

Mycobacterium fortuitum is a clinically important species among nontuberculous mycobacteria (NTM). Treatment of diseases caused by NTM is challenging. The aim of this study was identification of drug susceptibility and detection of mutations in erm(39) related to clarithromycin resistance and in rrl related to linezolid resistance in clinical isolates of M. fortuitum in Iran. In the study, 328 clinical NTM isolates were subjected to identification based on rpoB and 15% of isolates were assigned to M. fortuitum. Minimum inhibitory concentration for clarithromycin and linezolid was determined by E-test. Altogether 64% of M. fortuitum isolates showed resistanc to clarithromycin and 18% of M. fortuitum isolates showed resistance to linezolid. PCR and DNA sequencing were performed in erm(39) and in rrl genes for detection of mutations related to clarithromycin and linezolid resistance, respectively. Sequencing analysis revealed (84.37%) single nucleotide polymorphisms in the erm(39). A total 55.55% of M. fortuitum isolates harbored an A→G, 14.81% harbored an C→A, 29.62% harbored an G→T mutation in erm(39) at position 124, 135, 275. Seven strains harbored point mutation in the rrl gene either at T2131C or at A2358G. Our findings showed M. fortuitum isolates have become a serious problem with high-level antibiotic resistance. The existence of drug resistance to clarithromycin and linezolid indicates more attention to the study of drug resistance in M. fortuitum.

Adverse Drug Reactions Relevant to Drug Resistance and Ineffectiveness Associated with Meropenem, Linezolid, and Colistin: An Analysis Based on Spontaneous Reports from the European Pharmacovigilance Database

Antimicrobial resistance is considered one of the major threats to public health and is an important factor that influences the patient's outcome in the intensive care unit. Pharmacovigilance can help raise awareness of potential drug resistance (DR) or ineffectiveness (DI) through adverse drug reaction reports that are submitted to different spontaneous reporting systems. Based on spontaneous Individual Case Safety Reports from EudraVigilance, we conducted a descriptive analysis of adverse drug reactions associated with meropenem, colistin, and linezolid, with a focus on DR and DI. Of the total adverse drug reactions (ADRs) reported for each analyzed antibiotic by 31 December 2022, between 2.38-8.42% and 4.15-10.14% of the reports were related to DR and DI, respectively. A disproportionality analysis was conducted to evaluate the frequency of reporting adverse drug reactions relevant to the DR and DI of the analyzed antibiotics compared to other antimicrobials. Based on the analysis of the collected data, this study underlines the importance of post-marketing drug safety monitoring in raising a warning signal regarding antimicrobial resistance, thereby potentially contributing to the reduction in antibiotic treatment failure in an intensive care setting.

Modulating liposomal nanoparticles to enhance uptake and targeting of methicillin-resistant Staphylococcus aureus

Aims: To explore the role of modifying the phospholipid composition of liposomal nanoparticles (LNPs) on their uptake. Methods: Different LNPs were labeled with a fluorescent marker and their uptake by human lung fibroblast (WI-38) cells was evaluated using flow cytometry and confocal microscopy. Linezolid was loaded in LNPs showing enhanced uptake, and their ability to reduce intracellular methicillin-resistant Staphylococcus aureus (MRSA) was investigated by in vitro infection. Results: Liposomes with disaturated dipalmitoylphosphatidylcholine-phosphatidylglycerol-phosphatidylethanolamine at a molar ratio of 60:10:10, mimicking that of WI-38 cells, were more effectively uptaken. Linezolid-loaded LNPs significantly reduced intracellular MRSA viable count. Conclusion: Modified LNPs could be promising antibiotic nanocarriers for targeting intracellular MRSA, which are usually resistant to conventional antibiotics.

Real-world evaluation of linezolid-associated serotonin toxicity with and without concurrent serotonergic agents

BACKGROUND

The risk of linezolid-associated serotonin toxicity remains unclear. We sought to evaluate the incidence of serotonin toxicity among hospitalized patients who received linezolid with or without concurrent serotonergic agents (SA). Secondary outcomes were to assess the dose, agent selection, and number of SA.

METHODS

A single-center, retrospective cohort study was performed of hospitalized patients ≥18 years of age who received ≥1 dose of linezolid with or without SA between 1/1/14-6/30/2021. Patients were excluded if <18 years of age, had linezolid ordered but not administered, were pregnant, or incarcerated. Up to five concurrent SA were assessed, and dose category was divided into low, moderate, and high based on if the dose was <33%, 33-66%, and >66% of the maximum daily dose, respectively. Serotonin toxicity was identified by searching patients' electronic medical records. If identified, the Sternbach Criteria and Hunter criteria were applied.

RESULTS

Of 2022 patients screened, 1743 were included. Mean age, weight, and linezolid duration were 58.5 years, 90.7 kg, and 3.8 days, respectively. Approximately 67% (1168/1743) received linezolid with ≥1 SA, and several patients received multiple SA. Most patients (53.8%; 616/1144) received moderate and/or high dose SA. Only 2 patients (0.11%) were identified as possible serotonin toxicity based on the electronic medical record search. However, the incidence of serotonin toxicity was 0.06% (1/1743) and 0% (0/1743) based on Sternbach Criteria and Hunter Criteria, respectively.

CONCLUSIONS

Serotonin toxicity among hospitalized patients who received linezolid with or without SA was exceedingly rare, even among those who received multiple and higher dose SA.