Linezolid and vancomycin for nosocomial infections in pediatric patients: a systematic review

Abstract Objective: To investigate the effectiveness of linezolid and vancomycin for the treatment of nosocomial infections in children under 12 years old. Data sources: This is a systematic review in which five randomized clinical trials about the effectiveness of linezolid and vancomycin, involving a total of 429 children with nosocomial infections, were evaluated. They were searched in scientific databases: PubMed, Bvs, and SciELO. Summary of findings: The main nosocomial infections that affected children were bacteremia, skin, and soft tissue infections followed by nosocomial pneumonia. Most infections were caused by Gram-positive bacteria, which all studies showed infections caused by Staphylococcus aureus, with methicillin-resistant S. aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci strains being isolated. Both linezolid and vancomycin showed high therapeutic efficacy against different types of nosocomial infections, ranging from 84.4% to 94% for linezolid and 76.9% to 90% for vancomycin. Patients receiving linezolid had lower rates of rash and red man syndrome compared to those receiving vancomycin. However, despite the adverse reactions, antimicrobials can be safely administered to children to treat nosocomial infections caused by resistant Gram-positive bacteria. Conclusion: Both linezolid and vancomycin showed good efficacy in the treatment of bacterial infections caused by resistant Gram-positive bacteria in hospitalized children. However, linezolid stands out regarding its pharmacological safety. Importantly, to strengthen this conclusion, further clinical trials are needed to provide additional evidence.

Treating Pythiosis with Antibacterial Drugs Targeting Protein Synthesis: An Overview.

This review article explores the effectiveness of antibacterial drugs that inhibit protein synthesis in treating pythiosis, a difficult-to-treat infection caused by Pythium insidiosum. The article highlights the susceptibility of P. insidiosum to antibacterial drugs, such as macrolides, oxazolidinones, and tetracyclines. We examine various studies, including in vitro tests, experimental infection models, and clinical case reports. Based on our synthesis of these findings, we highlight the potential of these drugs in managing pythiosis, primarily when combined with surgical interventions. The review emphasizes the need for personalized treatment strategies and further research to establish standardized testing protocols and optimize therapeutic approaches.

Theoretical study of the interaction between the antibiotic linezolid and the active site of the 50S ribosomal subunit of the bacterium Haloarcula marismortui.

First antibiotic in the oxazolidinone class, linezolid fights gram-positive multiresistant bacteria by inhibiting protein synthesis through its interaction with the 50S subunit of the functional bacterial ribosome. For its antimicrobial action, it is necessary that its chiral carbon located in the oxazolidinone ring is in the S-conformation. Computational calculation at time-dependent density functional theory methodology, ultraviolet-visible (UV-Vis), and electronic circular dichroism spectra was obtained for noncomplexed and complexed forms of linezolid to verify the possible chirality of nitrogen atom in the acetamide group of the molecule. The molecular system has two chiral centers. So, there are now four possible configurations: RR, RS, SR, and SS. For a better understanding of the system, the electronic spectra at the PBE0/6-311++G(3df,2p) level of theory were obtained. The complexed form was obtained from the crystallographic data of the ribosome, containing the S-linezolid molecular system. The computational results obtained for the electronic properties are in good agreement with the experimental crystallographic data and available theoretical results.

Linezolid and vancomycin for nosocomial infections in pediatric patients: a systematic review.

OBJECTIVE: To investigate the effectiveness of linezolid and vancomycin for the treatment of nosocomial infections in children under 12 years old. DATA SOURCES: This is a systematic review in which five randomized clinical trials about the effectiveness of linezolid and vancomycin, involving a total of 429 children with nosocomial infections, were evaluated. They were searched in scientific databases: PubMed, Bvs, and SciELO. SUMMARY OF FINDINGS: The main nosocomial infections that affected children were bacteremia, skin, and soft tissue infections followed by nosocomial pneumonia. Most infections were caused by Gram-positive bacteria, which all studies showed infections caused by Staphylococcus aureus, with methicillin-resistant S. aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci strains being isolated. Both linezolid and vancomycin showed high therapeutic efficacy against different types of nosocomial infections, ranging from 84.4% to 94% for linezolid and 76.9% to 90% for vancomycin. Patients receiving linezolid had lower rates of rash and red man syndrome compared to those receiving vancomycin. However, despite the adverse reactions, antimicrobials can be safely administered to children to treat nosocomial infections caused by resistant Gram-positive bacteria. CONCLUSION: Both linezolid and vancomycin showed good efficacy in the treatment of bacterial infections caused by resistant Gram-positive bacteria in hospitalized children. However, linezolid stands out regarding its pharmacological safety. Importantly, to strengthen this conclusion, further clinical trials are needed to provide additional evidence.

Emergence of optrA-mediated linezolid resistance in clinical isolates of Enterococcus faecalis from Argentina.

OBJECTIVES: The aim of this study was to characterize the first 14 optrA-carrying linezolid resistant E. faecalis clinical isolates recovered in seven Argentinian hospitals between 2016 and 2021. The epidemiology of optrA-carrying isolates and the optrA genetic context were determined. METHODS: The isolates were phenotypically and genotypically characterized. Susceptibility to 13 antimicrobial agents was performed; clonal relationship was assessed by pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Data provided by the whole-genome sequencing were used for identification of sequence types, antimicrobial resistance genes, optrA variants, phylogenetic tree, and mobile genetic elements responsible to the dissemination of these strains. RESULTS: All the optrA-carrying E. faecalis isolates were multidrug-resistant and harboured several antimicrobial resistance genes. They carried three optrA variants and belonged to different lineages; however, three of them belonged to the hyperepidemic CC16. Mobile genetic elements were detected in all the isolates. The analysis of the optrA flanking region suggests the plasmidic localization in most of the isolates. CONCLUSIONS: To the best of our knowledge, this is the first report of optrA-mediated linezolid resistance in Argentina. The emergence and dissemination of the optrA genes in clinical E. faecalis isolates are of concern and highlights the importance of initiating the antimicrobial surveillance of Enterococcus spp. under a One Health strategy.

Fierce poison to others: the phenomenon of bacterial dependence on antibiotics.

Beyond the development of resistance, the effects of antibiotics on bacteria and microbial communities are complex and far from exhaustively studied. In the context of the current global antimicrobial resistance crisis, understanding the adaptive and physiological responses of bacteria to antimicrobials is of paramount importance along with the development of new therapies. Bacterial dependence on antibiotics is a phenomenon in which antimicrobials instead of eliminating the pathogens actually provide a boost for their growth. This trait comprises an extreme example of the complexities of responses elicited by microorganisms to these drugs. This compelling evolutionary trait was readily described along with the first wave of antibiotics use and dependence to various antimicrobials has been reported. Nevertheless, current molecular characterizations have been focused on dependence on vancomycin, linezolid and colistin, three critically important antibiotics frequently used as last resource therapy for multi resistant pathogens. Outstanding advances have been made in understanding the molecular basis for the dependence to vancomycin, including specific mutations involved. Regarding linezolid and colistin, the general physiological components affected by the dependence, namely ribosomes and membrane function respectively, have been established. Nonetheless the implications of antibiotic dependence in clinically relevant features, such as virulence, epidemics, relationship with development of resistance, diagnostics and therapy effectiveness require clarification. This review presents a brief introduction of the phenomenon of bacterial dependence to antibiotics and a summary on early and current research concerning the basis for this trait. Furthermore, the available information on the effect of dependence in key clinical aspects is discussed. The studies performed so far underline the need to fully disclose the biological and clinical significance of this trait in pathogens to successfully assess its role in resistance and to design adjusted therapies.

Comparación de regímenes de linezolid, en adición a bedaquilina y pretomanida, para el manejo de tuberculosis farmacorresistente (estudio ZeNix): Lectura crítica / Comparison of linezolid regimens, in addition to bedaquiline and pretomanid, for the management of drug-resistant tuberculosis (the ZeNix study): Critical reading

RESUMEN Presentación: En el presente artículo exponemos nuestra valoración crítica de un ensayo clínico aleatorizado publicado en la revista New England Journal of Medicine el año 2022. Conclusiones del estudio: El estudio compara cuatro regímenes de linezolid (en adición a bedaquilina y pretomanid) para el manejo de tuberculosis farmacorresistente. Finalmente, se demuestra que el régimen de 600 mg de linezolid durante 26 semanas tuvo menos frecuencia de falla terapéutica y eventos adversos (en comparación con darlo por menos semanas o a más dosis). Comentario crítico: El artículo es relevante porque aún no es clara la dosis adecuada de linezolid y la duración del tratamiento con este agente para minimizar los efectos adversos y mantener la eficacia contra la tuberculosis altamente resistente. A pesar de algunas limitaciones como el bajo número de participantes, la alta pérdida al seguimiento, y el no realizar comparaciones estadísticas entre grupos; los resultados son relativamente confiables para la toma de decisiones.

ABSTRACT Presentation: In this article we present our critical appraisal of a randomized clinical trial published in the New England Journal of Medicine in 2022. Study conclusions: The study compares four linezolid regimens (in addition to bedaquiline and pretomanid) for the management of drug-resistant tuberculosis. Finally, it shows that the regimen of 600 mg of linezolid for 26 weeks had less frequency of therapeutic failure and adverse events (compared to giving it for fewer weeks or at higher doses). Critical comment: The article is relevant because the appropriate dose of linezolid and duration of treatment with this agent to minimize adverse effects and maintain efficacy against highly resistant tuberculosis is still unclear. Despite some limitations such as low number of participants, high loss to follow-up, and no statistical comparisons between groups, the results are relatively reliable for decision making.

Mucoid Staphylococcus haemolyticus: an unheeded multidrug-resistant pathogen.

Coagulase-negative Staphylococci (CoNS) are among the most abundant members of human skin microbiome. CoNS have lately been recognized as substantial agents in plethora of infections, especially nosocomial infections in preterm infants and immunocompromised patients. Staphylococcus haemolyticus is the second most common species isolated from blood, and identification is further hindered when there is a deviation in morphology from the classical one. Here, we report an uncommon case of multidrug resistant mucoid S. hemolyticus isolated from blood in a patient of polytrauma. The patient was managed with ceftriaxone-sulbactam, gentamicin, and meropenem as empirical therapy, which was subsequently changed to intravenous vancomycin. The patient showed favorable response to treatment. Mucoid isolates are known to be more virulent and multi-drug resistant than the classical morphotypes. We also conducted systematic review to decipher the prevalence of mucoid S. hemolyticus and linezolid (LZD) resistance in the same. This case highlights the significance of awareness of mucoid phenotypes of Gram-positive cocci for clinical microbiologists to reach accurate identification. Resistance to LZD further underscores the need of restriction policies in hospitals and to roll out antimicrobial stewardship program stringently, so that the growing resistance could be contained.

Avances en tuberculosis en el 54° congreso chileno de enfermedades respiratorias. 1ra parte: nuevos esquemas acortados para tuberculosis drogoresistente ¿son adecuados para todos? / New shortened schemes for drug-resistant tuberculosis: are they suitable for everyone?

En esta presentación se realiza un recorrido a través de los diferentes esquemas terapéuticos de la tuberculosis drogo-resistente. Se muestra como los investigadores utilizan los nuevos fármacos disponibles y desarrollan diferentes esquemas cada vez más acortados y de administración por vía oral exclusiva, con la intención de lograr una mayor eficacia de curación de la tuberculosis resistente, con menos efectos colaterales y menor letalidad. La búsqueda de esquemas con una duración similar a las terapias de casos sensibles de tuberculosis (esquemas primarios de 6 meses) es el objetivo principal. Las pruebas moleculares como el Xpert ayudan enormemente a seleccionar los esquemas de terapia, según el perfil de susceptibilidad de los casos (resistencia a isoniazida, rifampicina, fluorquinolonas y combinaciones). Las terapias actuales de la tuberculosis drogo-resistente se basan en nuevos fármacos como fluorquinolonas, bedaquilina y linezolid, pero otros fármacos como pretomanid y delamanid también están siendo recomendados.

This presentation takes a tour through the different therapeutic schemes of drug-resistant tuberculosis. It shows how researchers use the new drugs available and develop different increasingly shortened schedules and exclusive oral administration, with the intention of achieving greater efficacy in curing resistant tuberculosis, with fewer side effects and lower lethality. The search for regimens with a duration similar to therapies of sensitive cases of tuberculosis (primary regimens of 6 months) is the main objective. Molecular tests, such as Xpert, greatly help in selecting therapy regimens, according to the susceptibility profile of the cases (resistance to isoniazid, rifampicin, fluorquinolones and combinations). Current drug-resistant tuberculosis therapies are based on new drugs such as fluorquinolones, bedaquiline and linezolid, but other drugs such as pretomanid and delamanid are also being recommended.

Transição de via de linezolida endovenosa para via oral: uma análise de custo-minimização / Switching from intravenous to oral linezolid therapy: a cost-minimization analysis

Objetivo: Comparar custos da terapia endovenosa exclusiva com linezolida com os custos da terapia iniciada por via endovenosa com transição para via oral após 72 horas, como estratégia de intervenção em programas de gestão de antimicrobianos. Métodos: Avaliação econômica de custo-minimização comparando custos diretos da terapia endovenosa exclusiva com linezolida com a terapia endovenosa seguida de transição para via oral em cenário simulado, sob a perspectiva do Sistema Único de Saúde (SUS), com árvore de decisão como modelo para tomada de decisão. Resultados: A alternativa englobando a transição de via mostrou-se a mais econômica em todos os cenários analisados. Para 28 dias de tratamento com linezolida, houve redução de 22% nos custos, considerando o paciente internado. Ao considerar alta após o sexto dia de tratamento, a redução de custos variou de 26%, com financiamento pelo SUS do restante do tratamento, a 84%, com financiamento do tratamento pós-alta pelo paciente. Conclusão: Conclui-se que a transição de via de linezolida é uma importante estratégia nos programas de gerenciamento de antimicrobianos, capaz de gerar economia significativa para a instituição. As avaliações econômicas de custo-minimização, nesse contexto, são uma importante ferramenta para demonstrar o aspecto econômico com potencial para sensibilizar gestores e tomadores de decisão.

Objective: To compare the direct costs of linezolid intravenous therapy with the costs of intravenous therapy switching to oral therapy after 72 hours as an intervention strategy in antimicrobial stewardship programs. Methods: Economic evaluation cost-minimization comparing direct costs of exclusive linezolid intravenous therapy with intravenous therapy for 72 hours and after switching to oral therapy in a simulated scenario, from the perspective of the National Health Service, with a decision tree as a decision modeling. Results: The alternative encompassing the therapy transition proved to be the most economical in all analyzed scenarios. For 28 days of treatment with linezolid, there was a 22% reduction in costs, considering the hospitalized patient. When considering discharge after the sixth day of treatment, the cost reduction ranged from 26%, with funding from the National Health Service for the rest of the treatment, to 84%, with funding for the post-discharge treatment by the patient. Conclusion: It was concluded that the linezolid therapy transition is an important strategy in antimicrobial management programs, capable of generating significant savings for the institution. In this context, economic cost-minimization assessments are an important tool to demonstrate the economic aspect with the potential to raise awareness among managers and decision-makers.

Risk of acute kidney injury and cost-effectiveness analysis comparing vancomycin and linezolid for the treatment of pediatric patients infected with Gram-positive bacteria / Risco de lesão renal aguda e custo-efetividade comparando vancomicina e linezolida para o tratamento de pacientes pediátricos infectados por bactérias Gram-positivas

Objective: This study aimed to compare the occurrence of acute kidney injury (AKI) in pediatric patients who used vancomycin (VAN) or linezolid (LNZ) to treat Gram-positive coccus (GPC) infections and to assess which treatment (VAN or LNZ) is the most cost-effective considering a pediatric hospital perspective. Methods: A retrospective cohort was performed to evaluate the occurrence of nephrotoxicity in pediatric patients without previous AKI, with GPC infections that used LNZ, or VAN monitored by serum VAN levels. Initially, descriptive analysis and Fisher and chisquare test were performed for this comparison. Then, a cost-effectiveness analysis was conducted through a decision tree model. The outcomes of interest were the rate of AKI related to the drug and the rate of admission to the intensive care unit (ICU) and cure. Results: In patients without previous acute kidney injury (AKI), 20% developed nephrotoxicity associated with VAN versus 9.6% in the LNZ group (p = 0.241). As there was no difference in nephrotoxicity between VAN andlinezolid (LNZ), vancomycin (VAN) monitored by serum VAN levels can optimize and rationalize the treatment. The nephrotoxicity risk criterion should not guide the prescription for LNZ. Furthermore, the average global cost of treatment with VAN was approximately R$ 43,000, while for LNZ, it was R$ 71,000. Conclusion: VAN was considered dominant (lower cost and greater effectiveness) over LNZ for treating patients with GPC infection.

Objetivo: Este estudo objetivou comparar a ocorrência de lesão renal aguda (LRA) em pacientes pediátricos que usaram vancomicina (VAN) ou linezolida (LNZ) para tratar infecções por cocos Gram-positivos (CGP) e avaliar qual tratamento (VAN ou LNZ) é o mais custo-efetivo considerando a perspectiva de um hospital pediátrico. Métodos: Foi realizada uma coorte retrospectiva para avaliar a ocorrência de nefrotoxicidade em pacientes pediátricos sem LRA prévia, com infecções por CGP que utilizaram LNZ ou VAN, combinada com vancocinemia. Para essa comparação, inicialmente foram realizados análise descritiva e testes de Fisher e qui-quadrado. Em seguida, foi realizada uma análise de custo-efetividade por meio de um modelo de árvore de decisão. Os desfechos de interesse foram a taxa de LRA relacionada ao medicamento e a taxa de internação em unidade de terapia intensiva e cura. Resultados: Nos pacientes sem LRA prévia, 20% deles desenvolveram nefrotoxicidade associada à VAN versus 9,6% no grupo LNZ (p = 0,241). Como não houve diferença na nefrotoxicidade entre VAN e LNZ, a VAN combinada com a vancocinemia pode otimizar e racionalizar o tratamento, e a prescrição de LNZ não deve ser guiada pelo critério de risco de nefrotoxicidade. Além disso, o custo médio global do tratamento com VAN foi de aproximadamente R$ 43.000, enquanto para LNZ foi de R$ 71.000. Conclusão: Assim, a VAN foi considerada dominante (menor custo e maior eficácia) sobre a LNZ para o tratamento de pacientes com infecção por CGP.

Risk Factors Associated with Failure of Linezolid Therapy in Vancomycin-Resistant Enterococcus faecium Bacteremia: A Retrospective Cohort Study in a Referral Center in Mexico.

We aimed to assess the factors associated with 30-day mortality in patients with vancomycin-resistant Enterococcus faecium (VREf) bloodstream infection (BSI) who received treatment with linezolid in an 11-year retrospective cohort of patients with VREf BSI. A univariate and stepwise multivariate logistic regression analysis was performed to determine 30-day mortality factors. Moreover, a Cox proportional hazards analysis of predictor covariates of mortality was performed. Eighty patients were included in the final analysis; 42 (53%) died and 38 (47%) survived 30 days after the index bacteremia. Thirteen patients of 42 (31%) died in the first 7 days. The Acute Physiology and Chronic Health Evaluation II (APACHE II) score was significantly associated with 30-day mortality (adjusted odds ratio [aOR], 1.46; 95% confidence interval [CI]: 1.22-1.76; p < 0.001) in the multivariate analysis. Moreover, VREf BSI persisting for more than 48 hours was a strong factor related to 30-day mortality (aOR, 19.6; 95% CI: 1.46-263; p = 0.01). Adequate control of infection source showed a trend to be protective without reaching significance in the multivariate analysis (aOR, 0.19; 95% CI: 0.04-1.0; p = 0.05). The Cox proportional hazards analysis confirmed the same significant mortality predictor besides linezolid treatment within the first 48 hours as a protective factor (hazard ratio 0.46; 95% CI: 0.23-0.92, p = 0.02). Severely ill patients with high APACHE II score and persistent bacteremia have a higher risk of failure with linezolid therapy.

Lactic acidosis associated with standard dose linezolid in a kidney recipient with impaired renal function.

Severe lactic acidosis, a mitochondrial toxicity caused by the recommended standard dosage of linezolid (LZD), may occur in patients with impaired renal function. We describe an adult male who underwent kidney transplantation with stably impaired renal function, severe dyspnea, and abdominal discomfort. He received a standard oral dose of LZD (600 mg twice daily) and azithromycin for three weeks with a reduced immunosuppressant dose due to pulmonary non-tuberculosis mycobacterial infection. He was alert and afebrile, with a blood pressure of 140/60 mmHg. Pertinent laboratory data showed: pH 7.12, PaCO2 13.6 mmHg; HCO3- 4.3 mmol/L and serum lactate 18.4 mmol/L. His trough serum LZD concentration reached toxic levels (21.4 µg/mL). With hemodialysis, his clinical symptoms improved, with a decline in serum LZD (9.8µg/mL) and lactate (3.2 mmol/L). Chronic standard dose LZD in patients with impaired renal function can lead to life-threatening lactic acidosis, especially in coexisting conditions that reduce LZD metabolism.

Lactic acidosis associated with standard dose linezolid in a kidney recipient with impaired renal function

Abstract Severe lactic acidosis, a mitochondrial toxicity caused by the recommended standard dosage of linezolid (LZD), may occur in patients with impaired renal function. We describe an adult male who underwent kidney transplantation with stably impaired renal function, severe dyspnea, and abdominal discomfort. He received a standard oral dose of LZD (600 mg twice daily) and azithromycin for three weeks with a reduced immunosuppressant dose due to pulmonary non-tuberculosis mycobacterial infection. He was alert and afebrile, with a blood pressure of 140/60 mmHg. Pertinent laboratory data showed: pH 7.12, PaCO2 13.6 mmHg; HCO3- 4.3 mmol/L and serum lactate 18.4 mmol/L. His trough serum LZD concentration reached toxic levels (21.4 μg/mL). With hemodialysis, his clinical symptoms improved, with a decline in serum LZD (9.8μg/mL) and lactate (3.2 mmol/L). Chronic standard dose LZD in patients with impaired renal function can lead to life-threatening lactic acidosis, especially in coexisting conditions that reduce LZD metabolism.

Potential activity of Linezolid against SARS-CoV-2 using electronic and molecular docking study.

The crescent evolution of a global pandemic COVID-19 and its respiratory syndrome (SARS-Cov-2) has been a constant concern (Ghosh 2021; Khan et al. 2021; Alazmi and Motwalli 2020; Vargas et al. 2020). The absence of a proven and effective medication has compelled all the scientific community to search for a new drug. The use of known drugs is a faster way to develop new therapies. Molecular docking is a powerful tool (Gao et al. J Mol Model 10: 44-54, 2004; Singh et al. J Mol Model 18: 39-51, 2012; Schulz-Gasch and Stahl J Mol Model 9:47-57, 2003) to study the interaction of potential drugs with SARS-CoV-2, Alsalme et al. (2020) and Sanders et al. (2020) spike protein as a consequence the main goal of this article is to present the result of the study of an interaction between (R and S)-Linezolid with receptor-binding domain (RBD) of SARS-Cov-2 spike protein complexed with human Angiostensin-converting enzyme 2 (ACE2) (6vW1 - from PDB). The Linezolid enantiomers were optimized at B3LYP/6-311++G(2d,p) level of theory. Molecular docking of the system (S)-Linezolid⋯RBD⋯ACE2 and (R)-Linezolid⋯RBD⋯ACE2 was performed, the analysis was made using LigPlot+ and NCIplot software packages, to understand the intermolecular interactions. The UV-Vis and ECD of the complexes - (R and S)-Linezolid⋯RBD⋯ACE2 were performed in two layers with DFT/6-311++G(3df,2p) and DFT/6-31G(d), respectively. The results showed that only the (S)-Linezolid had a stable interaction with - 8.05 kcal.mol- 1, whereas all the R-enantiomeric configurations had positive values of binding energy. The (S)-Linezolid had the same interactions as in the (S)-Linezolid ⋯ Haluarcula morismortui Ribosomal system, where it is well-known the fact that the latter has biological activity. A specific interaction on the fluorine ring justified an attenuation on the ECD signal, in comparison to isolated species. Therefore, some biological activity of (S)-Linezolid with SARS-CoV-2 RBD was expected, indicated by the modification of its ECD signal and justified by a similar interaction in the S-Linezolid⋯Haluarcula marismortui Ribosomal system.

Síndrome serotoninérgico como reacción adversa infrecuente ante la sinergia entre Linezolid y Fentanilo: presentación de caso / Serotonin syndrome as an infrequent adverse reaction to synergy between Linezolid and Fentanyl: case presentation

Resumen El síndrome serotoninérgico es una condición potencialmente mortal causada por medicamentos que afectan el metabolismo de la serotonina o que actúan como agonistas directos del receptor de esta o una combinación de ambos. El síndrome da lugar a una variedad de manifestaciones mentales, autonómicas y neuromusculares, que pueden variar desde leves hasta potencialmente mortales. Se reporta el caso clínico de un paciente el cual desarrolló este síndrome por la coadministración y sinergismo de linezolid y fentanilo, con una gran variedad de características clínicas, desde las más sutiles, como cifras tensionales altas de difícil manejo mientras se encontraba bajo el efecto de sedoanalgesia, hasta las manifestaciones más floridas del síndrome posterior a la suspensión de esta. La asociación de estos medicamentos representa una etiología poco informada que puede favorecer la aparición del síndrome, mientras que el uso de benzodiazepinas puede enmascarar el cuadro dificultando su diagnóstico. MÉD.UIS.2020;33(3): 59-66

Abstract Serotonin syndrome is a life-threatening condition caused by medications that affect serotonin metabolism or that act as direct agonists for serotonin receptor or a combination of both. The syndrome gives rise to a variety of mental, autonomic, and neuromuscular manifestations, which can range from mild to life-threatening. We report a clinical case of a patient who developed this syndrome due to the co-administration and synergism of linezolid and fentanyl, with a wide variety of clinical characteristics, from the most subtle, such as high blood pressure levels difficult to manage while under the effect of sedoanalgesia, to the most florid manifestations of the syndrome after 48 hours of its suspension. The association of these drugs represents a poorly reported etiology that may favor the appearance of the syndrome, while the use of benzodiazepines may mask the condition, making its diagnosis difficult. MÉD.UIS.2020;33(3): 59-66

Novel Linezolid analogues with antiparasitic activity against Hymenolepis nana.

The stereoselective synthesis and anti- Hymenolepis nana activity of six Linezolid-type compounds, obtained by chemical modification of l-Alanine, are reported in this work. The synthetic strategy was to prepare diasteromeric N,N-dibenzylamino oxazolidinones 1 and 2, and coupling with 4-(4-bromophenyl)morpholine (3) to obtain N,N-dibenzylamino Linezolid analogues 4 and 5. A hydrogenolysis reaction over 4 and 5 resulted in amino-free Linezolid analogues 6 and 7, which were acetylated to reach diasteromeric Linezolid analogues 8 and 9. The six Linezolid analogues 4-9 show in vitro antiparasitic activity against Hymenolepis nana cestode, but not against several bacterial strains. Interestingly, compounds 6, 7 and 9 exhibit high potency, having shorter paralysis and death times after exposure (6-10 and 18-21 min, respectively), shorter than those found with antihelmintic compound Praziquantel (20 and 30 min) at 20 mg/mL. In addition, a cytocompatibility assay of 6-9 with human cells (ARPE-19 cells) demonstrate a non-cytotoxic effect at 0.4 mM. These results show the pharmacological potential of the newly reported Linezolid-type analogues as antiparasitic agents against Hymenolepis nana.

Sustained Release of Linezolid from Prepared Hydrogels with Polyvinyl Alcohol and Aliphatic Dicarboxylic Acids of Variable Chain Lengths.

A series of hydrogels with a specific release profile of linezolid was successfully synthesized. The hydrogels were synthesized by cross-linking polyvinyl alcohol (PVA) and aliphatic dicarboxylic acids, which include succinic acid (SA), glutaric acid (GA), and adipic acid (AA). The three crosslinked hydrogels were prepared by esterification and characterized by equilibrium swelling ratio, infrared spectroscopy, thermogravimetric analysis, mechanical properties, and scanning electron microscopy. The release kinetics studies of the linezolid from prepared hydrogels were investigated by cumulative drug release and quantified by chromatographic techniques. Mathematical models were carried out to understand the behavior of the linezolid release. These data revealed that the sustained release of linezolid depends on the aliphatic dicarboxylic acid chain length, their polarity, as well as the hydrogel crosslinking degree and mechanical properties. The in vitro antibacterial assay of hydrogel formulations was assessed in an Enterococcus faecium bacterial strain, showing a significant activity over time. The antibacterial results were consistent with cumulative release assays. Thus, these results demonstrated that the aliphatic dicarboxylic acids used as crosslinkers in the PVA hydrogels were a determining factor in the antibiotic release profile.

[National surveillance of clinical isolates of Enterococcus faecalis resistant to linezolid carrying the optrA gene in Colombia, 2014-2019]. / Vigilancia nacional de aislamientos clínicos de Enterococcus faecalis resistentes al linezolid portadores del gen optrA en Colombia, 2014-2019.

OBJECTIVE: To describe the epidemiological, phenotypical and genetic characteristics of clinical isolates carrying the optrA gene identified in antimicrobial resistance surveillance by the laboratory of the National Institute of Health of Colombia. METHODS: Between October 2014 and February 2019, 25 isolates of Enterococcus spp. resistant to linezolid were received. Antimicrobial identification and sensitivity were determined using Vitek 2 and the minimum inhibitory concentration (MIC) to linezolid was established with E-test. The optrA gene was detected by PCR, and the genetic diversity of optrA-positive isolates was tested with Diversilab®. Six isolates were selected to perform whole genome sequencing. RESULTS: The optrA gene was confirmed in 23/25 isolates of E. faecalis from seven departments in Colombia. The isolates presented a MIC to linezolid between 8 and >256µg/mL. Typing by Diversilab® showed a wide genetic variability. All the isolates analyzed by whole genome sequencing showed the resistance genes fexA, ermB, lsaA, tet(M), tet(L) and dfrG in addition to optrA and were negative for other mechanisms of resistance to linezolid. Three type sequences and three optrA variants were identified: ST16 (optrA-2), ST476 (optrA-5) and ST618 (optrA-6). The genetic environment of the optrA-2 (ST16) isolates presented the impB, fex, optrA segment, associated with plasmid, while in two isolates (optrA-6 and optrA-5) the transferable chromosomal element Tn6674-like was found. CONCLUSION: OptrA-positive clinical isolates present a high genetic diversity, with different optrA clones and variants related to two types of structures and different mobile genetic elements.

Isolation and first draft genome sequence of a linezolid-dependent Staphylococcus aureus clinical strain.

Background: Antibiotic-dependent pathogenic bacteria are sporadically isolated from patients that received prolonged antibiotic treatments. Evolution of antibiotics dependence and its clinical implications are scarcely studied. Materials & methods: A linezolid-dependent Staphylococcus aureus strain was isolated from a cystic fibrosis patient. A draft genome sequence was obtained and searched for known antibiotics resistance determinants and virulence factors. Results: The genome was assembled into 79 contigs for a total of 2.83 Mbp. This strain is a sequence type 5 methicillin-resistant Staphylococcus aureus with a type I SCCmec cassette also conserving the Panton-Valentine leukocidin. The G2576T substitution, conferring linezolid resistance, was harbored by all five copies of the 23S rRNA. Conclusion: The linezolid-dependent strain is related to a strain circulating in Latin America that acquired a mutation conferring linezolid resistance.