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Nocardia pyomyositis in immunocompetent patients is a rare occurrence. The diagnosis may be missed or delayed with the risk of progressive infection and suboptimal or inappropriate treatment. We present the case of a 48-year-old immunocompetent firefighter diagnosed with pyomyositis caused by Nocardia brasiliensis acquired by direct skin inoculation from gardening activity. The patient developed a painful swelling on his right forearm that rapidly progressed proximally and deeper into the underlying muscle layer. Ultrasound imaging of his right forearm showed a 7-mm subcutaneous fluid collection with surrounding edema. Microbiologic analysis of the draining pus was confirmed to be N brasiliensis by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) Mass Spectrometry. After incision and drainage deep to the muscle layer to evacuate the abscess and a few ineffective antibiotic options, the patient was treated with intravenous ceftriaxone and oral linezolid for 6 weeks. He was then de-escalated to oral moxifloxacin for an additional 4 months to complete a total antibiotic treatment duration of 6 months. The wound healed satisfactorily and was completely closed by the fourth month of antibiotic therapy. Six months after discontinuation of antibiotics, the patient continued to do well with complete resolution of the infection. In this article, we discussed the risk factors for Nocardia in immunocompetent settings, the occupational risks for Nocardia in our index patient, and the challenges encountered with diagnosis and treatment. Nocardia should be included in the differential diagnosis of cutaneous infections, particularly if there is no improvement of "cellulitis" with traditional antimicrobial regimens and the infection extends into the deeper muscle tissues.

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INTRODUCTION: Ventilator-associated pneumonia (VAP) is a prominent cause of morbidity and mortality in intensive care unit (ICU) patients. Due to the increase in Methicillin resistant Staphylococcus aureus infection, it is important to consider other more effective and safer alternatives compared to vancomycin. This motivates evaluating whether the use of an apparently more expensive drug such as linezolid can be cost-effective in Colombia. METHODS: A decision tree was used to simulate the results in terms of the cost and proportion of cured patients. In the simulation, patients can receive antibiotic treatment with linezolid (LZD 600 mg IV/12 h) or vancomycin (VCM 15 mg/kg iv/12 h) for 7 days, patients they can experience events adverse (renal failure and thrombocytopenia). The model was analyzed probabilistically, and a value of information analysis was conducted to inform the value of conducting further research to reduce current uncertainties in the evidence base. Cost-effectiveness was evaluated at a willingness-to-pay (WTP) value of US$5180. RESULTS: The mean incremental cost of LZD versus VCM is US$-517. This suggests that LZD is less costly. The proportion of patients cured when treated with LZD compared with VCM is 53 vs. 43%, respectively. The mean incremental benefit of LZD versus VCM is 10 This position of absolute dominance (LZD has lower costs and higher proportion of clinical cure than no supplementation) is unnecessary to estimate the incremental cost-effectiveness ratio. There is uncertainty with a 0.999 probability that LZD is more cost-effective than VCM. Our base-case results were robust to variations in all assumptions and parameters. CONCLUSION: LNZ is a cost-effective strategy for patients, ≥ 18 years of age, with VAP in Colombia- Our study provides evidence that can be used by decision-makers to improve clinical practice guidelines.

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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.

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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.

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BACKGROUND Cutaneous adverse drug reactions are the skin's response to a systemic exposure to drugs. Linezolid is an oral oxazolidine used to treat methicillin-resistant Staphylococcus aureus infections. Even though it has well-known adverse effects, purpuric cutaneous adverse drug reactions to linezolid have been scarcely described. This report is of a Puerto Rican man in his 80s who developed an extensive purpuric drug eruption secondary to linezolid use. Clinicians should be aware of this phenomenon, since prompt identification and discontinuation of the agent are essential for recovery. CASE REPORT An 89-year-old Puerto Rican man was given oral linezolid therapy for healthcare-associated pneumonia and developed a widespread, purpuric cutaneous eruption 5 days into therapy. His condition prompted immediate discontinuation of the drug. Forty-eight hours after stopping the medication, he visited the Emergency Department. Abdominal punch biopsy revealed a superficial and perivascular lymphocytic infiltrate with dermal eosinophils, a pathologic finding consistent with a purpuric drug eruption. This allowed for a timely diagnosis, exclusion of other mimickers, such as cutaneous vasculitis, and effective management. CONCLUSIONS Cutaneous adverse drug reactions to linezolid have been scarcely reported in the literature. Due to the low incidence of this manifestation, the identification of the causative agent and accompanying treatment may be delayed. Mainstays in therapy are avoidance of the offending agent and treatment with corticosteroids, antihistamines, barrier ointments, and oral analgesics. Primary healthcare providers should be aware of linezolid-induced cutaneous manifestations, diagnostic clues, and treatment options so they can rapidly identify and effectively treat such complications.

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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.

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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.

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Adverse reaction reporting is essential to understand the actual safety of marketed medicines. There are cases of patients with multidrug intolerance syndrome, an under-reported entity, which can occur when adverse reactions to more than two pharmacologically unrelated drugs occur in the same patient. We describe the case of a woman diagnosed with multisensitive Staphylococcus aureus endocarditis who experienced adverse reactions to five structurally unrelated antibiotics with different mechanisms of action in two consecutive hospitalisations. The reactions were secondary to cefazolin (tricytopenia), vancomycin (renal injury), daptomycin (elevated creatine phosphokinase) and linezolid (hepatotoxicity) in the first hospitalization, and to cotrimoxazole (thrombocytopenia) in the second. Transient damage to different organ systems was observed in all cases. Finally, hospital discharge was granted with clindamycin without further intercurrences until treatment was completed. This case could correspond to the aforementioned syndrome or to an as yet uncharacterized entity.

La información sobre reacciones adversas es fundamental para conocer la seguridad real de los medicamentos comercializados. Existen casos de pacientes con síndrome de intolerancia a múltiples drogas, una entidad poco reportada, la que puede presentarse cuando en un mismo paciente ocurren reacciones adversas a más de dos medicamentos no relacionados farmacológicamente. Se describe el caso de una mujer con diagnóstico de endocarditis por Staphylococcus aureus multisensible, que cursó con reacciones adversas a cinco antibióticos estructuralmente no relacionados y con mecanismos de acción diferentes, en dos internaciones consecutivas. Las reacciones fueron secundarias a cefazolina (tricitopenia), vancomicina (injuria renal), daptomicina (elevación de creatina fosfoquinasa) y linezolid (hepatotoxicidad) en la primera internación, y a cotrimoxazol (plaquetopenia) en la segunda. En todos los casos se observó daño transitorio en diferentes sistemas de órganos. Finalmente, se otorgó alta hospitalaria con clindamicina sin nuevas intercurrencias hasta finalizar tratamiento. Este caso podría corresponder al síndrome antes mencionado o a una entidad aún no caracterizada.

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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.

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