Search Results (363)

Enterococcus spp. are opportunistic and nosocomial pathogens. Intensive pig farms have been recently described as important hotspots for antibiotic resistance and reservoirs of potentially pathogenic enterococci, including other species than the most known E. faecalis and E. faecium. Here, we identified Linezolid-resistant non-E. faecalis and E. faecium (NFF) Enterococcus strains isolated from different production stages (suckling piglets, weaning pigs, and fatteners) across six intensive pig farms. The transferability of the linezolid-resistance determinants was assessed by bacterial conjugation and strains were also characterized for biofilm production, hemolytic and gelatinase activity. Among 64 identified NFF Enterococcus strains, 27 were resistant to at least three different antibiotic classes and 8/27 specifically to Linezolid. E. gallinarum and E. casseliflavus both transferred their Linezolid resistance determinants to the main pathogenic species E. faecium. Remarkably, this is the first report of the optrA gene transfer from E. casseliflavus to E. faecium by conjugation, which can greatly contribute to the spread of antibiotic resistance genes among pathogenic enterococcal species. The “weaning pigs” stage exhibited a significantly higher number of antibiotic-resistant enterococci than the “fatteners”. These findings highlight the importance of monitoring pig farms as hotspots for the spread of antibiotic-resistant enterococci, especially in the early stages of production. Furthermore, they underscore the significant role of NFF Enterococcus species as carriers of antibiotic resistance genes, even to last-resort antibiotics, which may be transferable to the major enterococcal species. Full article

Background: Broad-spectrum antibiotics are often used for suspected infections in patients with hematologic malignancies due to the risk of severe infections. Although antibiotic use can lead to antimicrobial resistance and microbiome dysbiosis, the effects of antibiotics on the microbiome and resistome in patients with acute myeloid leukemia (AML) undergoing remission induction chemotherapy (RIC) are not well understood. Methods: Various statistical models were utilized to examine the effects of antibiotic administration on the microbiome and resistome over time, as well as differences in AR-infection (ARI) and colonization (ARC) by important CDC-threats in 119 AML patients. Results: A greater number of unique antibiotic classes administered correlated with a loss of unique antibiotic resistance genes (ARGs) (R = −0.39, p = 0.008). Specifically, although a greater number of oxazolidinone administrations was correlated with a greater loss of diversity (R = −0.58, p < 0.001), each additional day of linezolid reduced the risk of ARC by ~30% (HR: 0.663, p = 0.047) and decreased the odds of acquiring genes predicted to confer macrolide (HR: 0.50, p = 0.026) resistance. Conclusions: The number of antibiotic administrations and the types of antibiotics used can influence the risk of antibiotic resistance gene (ARG) expansion and ARC events in AML patients undergoing RIC. While certain antibiotics may reduce microbial diversity, they are not always linked to an increase in ARGs or ARC events. Full article

Linezolid, an antimicrobial agent, has been linked to lactic acidosis, oxidative stress, and liver damage. Oxidative stress is considered to play a key role in this damage. Thiamine pyrophosphate (TPP), the active form of thiamine, may prevent lactate accumulation and enhance aerobic capacity. Therefore, this study aimed to evaluate the protective effect of TPP against possible linezolid-induced liver damage and lactic acidosis in rats. Twenty-four male Wistar albino rats were randomly assigned to four groups (n = 6): healthy control (HG), linezolid (LZD), thiamine plus linezolid (TLZD), and TPP plus linezolid (TPLZD). Thiamine and TPP (20 mg/kg, intraperitoneal (i.p.)) were administered once daily, while linezolid (125 mg/kg, per os (p.o.)) was given twice daily (250 mg/kg/day) for 28 days. Animals were euthanized under high-dose anesthesia (with 50 mg/kg, i.p. thiopental sodium). Liver tissues were analyzed for MDA, tGSH, SOD, and CAT, and examined histopathologically. Blood samples were collected prior to euthanasia to assess lactate, LDH, ALT, AST, and TPP levels. In the LZD group, MDA, lactate, ALT, AST, and LDH levels significantly increased, while tGSH, SOD, CAT, and TPP decreased (p < 0.001). Histopathology showed hydropic degeneration, necrosis, and mononuclear cell infiltration (p < 0.05). Thiamine did not prevent these alterations (p > 0.05), whereas TPP significantly prevented both biochemical and histopathological changes (p < 0.05), indicating its protective efficacy. TPP may offer significant protection against linezolid-induced hepatotoxicity and lactic acidosis. Full article

Necrotizing soft tissue infections (NSTIs) are serious and aggressive infections which can result in significant morbidity and mortality. Both prompt surgical intervention and early antibiotics can decrease patient mortality. Based on microbiology, NSTIs can be categorized into four different types. Type I is polymicrobial, caused by a mix of both anaerobic and aerobic bacteria. Type II is monomicrobial, usually caused by either Streptococcus or Staphylococcus. Type III infections are caused by Gram-negative bacteria, often marine-related organisms, such as Vibrio. Lastly, Type IV infections are caused by fungi, and they are often associated with trauma. Despite the possibility of all these different pathogens in NSTI, early therapy often consists of a broad Gram-positive antimicrobial such as linezolid or vancomycin, and a broad Gram-negative agent such as piperacillin/tazobactam. Multiple factors including patient comorbidities, environmental exposures, and clinical presentation must also be considered when choosing antimicrobial agents and dosing. Adjunct medical therapies such as intravenous immunoglobulin (IVIG) and the antibiotics clindamycin and linezolid that are aimed at toxin suppression may be utilized to improve outcomes. Microbiological data are critical for optimizing the antimicrobial regimen. Full article

Background/Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus pseudintermedius (MRSP) represent important antimicrobial resistance threats related to companion animals, which can directly or indirectly lead to adverse health effects in humans and animals living in close contact. Characterizing the phenotypic resistance of MRSA and MRSP to a panel of antimicrobials relevant to both veterinary and human medicine is crucial within a “One Health” framework. Methods: In this study, a total of 79 presumptive MRSA isolates (34 from cats, 45 from dogs) and 110 presumptive MRSP isolates (105 from dogs, 5 from cats) from clinical cases were analysed. Real-time PCR was used to detect the presence of mecA and mecC genes, and susceptibility testing was performed using the Sensititre EUST2 panel. Results: Most of the isolates (88.9%, 168/189) were positive for the mecA gene, while a minority (1.1%, 2/189) were mecC-positive (2 MRSA, 1 dog, 1 cat). MRSP isolates exhibited acquired resistance to a broader range of antibiotics compared to MRSA strains. Furthermore, several isolates demonstrated acquired resistance to antibiotics considered critically important for human medicine. Resistance to vancomycin was found in an MRSP isolate from a dog, and resistance to linezolid in an MRSP isolate from a cat. This study reveals that 83.3% (30/36) of MRSA isolates from dogs and 89.3% (25/28) from cats were multidrug-resistant organisms, while MRSP isolates exhibited multidrug resistance in 99% (101/102) of cases for dogs and 100% (4/4) for cats. Conclusions: The extremely high level of multidrug resistance, with some isolates resistant to critically important antibiotics used in human medicine, highlight the importance of monitoring antimicrobial susceptibility in MRSA and MRSP isolates collected from cats and dogs in a One Health perspective. Full article

Background: Due to the high prevalence of severe infections, antibiotics are frequently administered in anaesthesia and intensive care units. Despite their therapeutic efficacy, several antibiotics exhibit neurotoxic potential, resulting in central and peripheral neurological complications in patients. This review aims to summarise the current evidence on antibiotic-induced neurotoxicity, particularly in critical care settings. Methods: A comprehensive literature analysis was performed to assess the neurotoxic profiles, underlying mechanisms, and clinical manifestations associated with different antibiotic classes, including beta-lactams, fluoroquinolones, macrolides, aminoglycosides, and others. Results: Beta-lactam antibiotics (especially cephalosporins and carbapenems) are strongly associated with seizures, encephalopathy, and EEG abnormalities, mainly through GABAergic inhibition and mitochondrial dysfunction. Fluoroquinolones and macrolides can cause psychosis, insomnia, and neuropathy via NMDA activation and oxidative stress. Linezolid carries the risk of serotonin syndrome and optic neuropathy, while glycopeptides and aminoglycosides are primarily associated with ototoxicity. Risk factors include advanced age, renal or hepatic impairment, and high serum drug levels. Conclusions: The neurotoxic potential of antibiotics is a critical but under-recognised aspect of pharmacotherapy in intensive care. Improved awareness, pharmacovigilance, dose adjustment, and drug monitoring are crucial for mitigating adverse neurological effects. Full article

The antimicrobial resistance (AMR) surveillance network has been monitoring bloodstream bacterial pathogens and their resistance since 1999 in Tunisia. We report the long-term trends in the distribution of bloodstream bacterial pathogens and their resistance patterns from this surveillance database. We analyzed antibiotic resistance rates in 11 tertiary teaching hospital laboratories under the AMR surveillance network during 2011–2023, focusing on six priority bacterial pathogens, using the Cochrane–Armitage test for trend analysis. Of 22,795 isolates, K. pneumoniae (38.5%) was the most common, followed by S. aureus (20.4%), E. coli (13.6%), and A. baumannii (10.3%). Carbapenem resistance was highest in A. baumannii (77%), followed by Pseudomonas aeruginosa (29.3%), K. pneumoniae (19.4%), and Enterobacter cloacae (6.8%). Carbapenem-resistant Enterobacterales and third-generation cephalosporin-resistant Enterobacterales (3GCREB) increased from 10.6% to 26.3% (p-value < 0.001), and from 39% to 50.2%, respectively, during 2011–2023 (p-value < 0.001). Vancomycin resistance (38.3%) and the emergence of linezolid resistance in 2019 (2.4%) were reported in E. faecium isolates. Resistance to carbapenems and 3GC is a major challenge to controlling BSI in Tunisia. The national AMR surveillance network helps monitor annual patterns and guides empirical therapy. An integrated database combining clinical profiles and resistance data via real-time data-sharing platforms could improve clinical decision-making. Full article

The treatment of Mycobacterium avium complex (MAC) remains a clinical challenge as multidrug regimens are needed and may be limited by treatment-related toxicity. The Clinical and Laboratory Standards Institute (CLSI) endorses breakpoints for several agents used for MAC infection treatment. Amikacin has distinct breakpoints for intravenous (IV) therapy and inhaled therapy using amikacin liposome inhalation suspension (ALIS) for MAC pulmonary disease. The purpose of the present retrospective cohort study of MAC pulmonary isolates was to assess the number of amikacin non-susceptible isolates by the IV breakpoints that remain susceptible to the inhaled breakpoints. One isolate per patient per year was assessed and susceptibility was described for amikacin IV, amikacin inhaled, clarithromycin, moxifloxacin, and linezolid per the CLSI. Of the 218 isolates, 94% [204/218] tested as susceptible to amikacin per the IV breakpoints compared with 99.5% [217/218] to the inhaled breakpoints. Of the amikacin IV non-susceptible isolates, 93% [13/14] were susceptible by the inhaled breakpoints. For comparison, clarithromycin was the next most active agent followed by moxifloxacin and linezolid with 97% [211/218], 82% [178/218], and 66% [143/218] of isolates testing as susceptible to each, respectively. These data highlight the importance of laboratories to report both the IV and inhaled amikacin interpretive criteria so that clinicians do not disregard potential therapeutic options for the treatment of MAC pulmonary disease. Full article

Background/Objectives: The optimal therapy for polymicrobial wound infections is poorly defined. We sought to characterize the ability of linezolid to combat mixed cultures of Staphylococcus aureus and Pseudomonas aeruginosa. Methods: The antistaphylococcal activity of linezolid was assessed in 24-h time-killing experiments that used S. aureus and P. aeruginosa isolated from polymicrobial wound infections. Clindamycin was also evaluated as a comparator. A Hill-type mathematical model was used to assess the maximum killing of S. aureus (E_max). The ability of linezolid to potentiate the activity of host defense peptides against P. aeruginosa was evaluated using LL-37. Results: In the presence of P. aeruginosa, the E_max of linezolid decreased in 5/9 co-culture experiments and increased in 4/9 co-culture experiments in comparison to linezolid against S. aureus alone. The potency of linezolid was not significantly impacted by the presence of P. aeruginosa. In comparison, the maximal S. aureus killing achieved by clindamycin decreased in eight out of nine experiments, and somewhat paradoxically, the potency increased in nine out of nine experiments. In the host defense peptide assay, the supratherapeutic linezolid concentration of 64 mg/L did not significantly enhance the killing of the LL-37 peptides (p ≥ 0.121), but the concentration of linezolid was significantly associated with the killing of one of three P. aeruginosa isolates (p = 0.005). Conclusions: P. aeruginosa had a minimal impact on the antistaphylococcal activity of linezolid in comparison to clindamycin. Linezolid did not exert a consistent ability to enhance the antipseudomonal activity of host defense peptides. These data may help inform antimicrobial selection during polymicrobial wound infections. Full article

Objectives: Linezolid resistance among Enterococcus species poses a growing clinical and public health concern, especially due to the dissemination of transferable resistance genes, such as optrA. This study aimed to evaluate the prevalence of linezolid resistance and to characterize the molecular epidemiology and genetic contexts of optrA-positive linezolid-resistant Enterococcus (LRE) isolates from clinical and animal sources in South Korea. Methods: A total of 2156 Enterococcus isolates, collected through nationwide surveillance from hospitalized patients and healthy livestock (pigs, cattle, and chickens) between 2017 and 2019, were retrospectively analyzed. Phenotypic susceptibility testing, optrA gene screening, and whole-genome sequencing were performed to investigate genetic environments and phylogenetic relationships. Results: The prevalence of linezolid resistance was 0.2% in clinical isolates, 3.3% in pigs, 4.3% in cattle, and 1.4% in chickens. optrA-positive linezolid-resistant isolates were less frequent, with rates of 0.1%, 1.4%, 0.9%, and 1.0%, respectively. Multilocus sequence typing identified sequence types (STs) 330 and ST476 in E. faecalis from humans, with no shared STs between human and livestock isolates. The optrA gene was located either chromosomally, frequently associated with transposon Tn6674, or on multidrug resistance plasmids. Notably, optrA variants exhibited host-specific distribution patterns. Phylogenetic analysis demonstrated considerable genomic diversity, and Korean ST476 isolates were genetically related to international strains reported from livestock, poultry products, and wild birds, suggesting potential global dissemination. Conclusions: This study provides a comprehensive, nationally representative assessment of linezolid resistance in South Korea. The findings highlight the zoonotic potential and possible international dissemination of optrA-carrying ST476 lineages, underscoring the need for integrated One Health surveillance to monitor and control the spread of transferable resistance genes. Full article

The emergence of antimicrobial resistance (AMR) in Clostridium difficile (C. difficile), particularly to last-line antibiotics such as linezolid, represents a critical challenge in clinical settings. This study investigates the genomic epidemiology of linezolid-resistant C. difficile, focusing on the distribution and mutational patterns of the chloramphenicol–florfenicol resistance (cfr) gene and its association with multidrug resistance. We analyzed 514 clinical isolates (354 from NCBI Pathogen Detection, 160 from EnteroBase), revealing distinct prevalence patterns among cfr subtypes: cfr(C) was dominant (156/354 NCBI strains; 101/160 EnteroBase strains), whereas cfr(B) frequently harbored missense mutations (p.R247K, p.V294I, and less commonly p.A334T). The cfr(E) subtype was exclusively identified in ribotype 027 (RT027) strains. Notably, cfr(C) exhibited a strong association with RT017, correlating with a conserved 99 bp genomic deletion. Phylogenetic analysis linked cfr-carriage to predominant sequence types (ST1 in NCBI strains, ST37 in EnteroBase isolates). Furthermore, the co-occurrence of cfr with additional AMR genes conferred resistance to macrolides (erythromycin, azithromycin) and tetracyclines, indicating a convergent evolution toward multidrug resistance. These findings underscore the interplay between cfr mutations, hypervirulent ribotypes, and AMR dissemination, necessitating enhanced surveillance to mitigate the spread of resistant C. difficile lineages. Full article

Bacillus Calmette–Guerin (BCG) central nervous system (CNS) infections are one of the rarest complications following BCG exposure. A 77-year-old male, with bladder cancer previously treated with BCG instillation, presented with fever, confusion, and brain magnetic resonance imaging (MRI) consistent with encephalitis one month after the last BCG instillation. Cerebrospinal fluid (CSF) showed marked hypoglycorrhachia, hyperproteinorrachia, and lymphocytic pleocytosis. Despite CSF culture negativity, the presentation was considered suggestive of BCG-related encephalitis, and the empirical standard antitubercular treatment (rifampin, isoniazid and ethambutol), plus dexamethasone, was initiated. Following initial improvement, gait ataxia and hemiplegia were observed at the 4-month follow-up. MRI revealed an excluded enlarged left lateral ventricle with signs of ventriculitis, requiring surgical drainage. CSF collected during neurosurgery resulted positive on PCR for M. tuberculosis complex. Adjunctive linezolid was initiated, replaced by levofloxacin due to adverse events after 2 weeks. The patient was discharged following a normal CSF analysis. Oral antitubercular therapy was prescribed for 14 months and there were no signs of relapse at the 24-month follow-up. Previously, 16 cases of CNS BCGitis have been reported, without any cases of clinical relapse during antitubercular treatment. Furthermore, our study reports the use of linezolid as a 4th antitubercular drug for CNS BCGitis. Full article

(1) Background: Spontaneous bacterial peritonitis (SBP) is associated with a 20% mortality and is mainly caused by Gram-negative bacteria (GNB); Gram-positive bacteria (GPB) were predominant in some areas; and increased antibiotic resistance was recorded. (2) Methods: A retrospective study was performed between 2018 and 2024. The type of isolated strains, antibiotic susceptibility, and mortality (in-hospital; 30-day; 90-day; and 1-year) were estimated; multivariate analyses evaluated predictive factors for in-hospital mortality risk. (3) Results: 45 culture-positive SBP, 28 culture-negative SBP, 6 bacterascites, and 670 control ascites were diagnosed; GPB represented 60%; two Candida peritonitis and 11 polymicrobial peritonitis (21.6%) were noted (without surgery; peritoneal dialysis; or tegumentary lesion). High resistance rates to cephalosporins and quinolones, and high carbapenem resistance for nosocomial GNB were recorded. A low resistance rate to Tigecycline was noted in all infection types; GPB was susceptible to Linezolid and Vancomycin; and GNB was susceptible to Aztreonam and Colistin. In-hospital mortality was 26.7% (40% for GNB-SBP; 20% for GPB-SBP), similar to culture-negative SBP (21.3%), and higher than in the control group (9%); long-term mortality remained higher. (4) Conclusions: microbial changes to GPB etiology and increasing resistance were noted, but with a lower mortality compared to GNB; higher mortality rates up to 1 year for culture-positive and culture-negative SBP were recorded Full article

This study examines temporal patterns in pathogens isolated from prosthetic joint infection (PJI) cases and antimicrobial resistance patterns at a Romanian orthopedic center. We have conducted a retrospective cohort study that included 674 patients undergoing hip or knee replacement revision surgery between January 2016 and December 2023. From these, 102 confirmed PJI cases requiring surgical intervention were selected for analysis. We isolated 27 microorganisms from acute PJI cultures and 82 from chronic PJIs. Staphylococcus epidermidis (33 cases, 30.3%; 95% CI 22.0–40.3) was the predominant pathogen, with coagulase-negative Staphylococci (22 cases, 20.18%; 95% CI 0.9–41.3) and Enterobacteriaceae (13 cases, 11.9%; 95% CI 6.4–18.3) also prevalent. Methicillin resistance was identified in 43.6% of coagulase-negative staphylococci and 45.5% of Staphylococcus aureus isolates. All Gram-positive isolates remained susceptible to vancomycin, linezolid, and tigecycline. Among Gram-negative bacilli, Klebsiella oxytoca and Proteus mirabilis showed resistance to third-generation cephalosporins, with phenotypic profiles suggestive of extended-spectrum β-lactamase (ESBL) production. All Escherichia coli, Enterobacter spp., and Citrobacter freundii strains were fully susceptible to tested agents, while Pseudomonas aeruginosa exhibited reduced susceptibility to ciprofloxacin, aztreonam, and imipenem. Among the isolated strains, 47 were multidrug-resistant (MDR), with Staphylococcus aureus accounting for the highest MDR count, including methicillin resistance. The distribution of microorganism types and MDR strains remained consistent throughout the study period, with no significant association between infection type and MDR strain presence or between infection site and microorganism presence except for a strong association between MDR strains and the type of microorganism (p < 0.05). The microbial profile and resistance patterns in PJIs have remained stable over eight years. Our observations do not suggest that MDR PJIs are more commonly acute cases, contrary to what has been highlighted in previous reports. The ongoing prevalence of MDR strains underscores the importance of targeted antimicrobial treatments based on local susceptibility profiles. Full article

Background/Objective:Staphylococcus aureus produces staphyloferrin A (Sfna) siderophores to sequester host iron during infection and rapid cell proliferation We examined drug susceptibility, siderophore production, and genome sequencing of clinical isolates of S. aureus. Methods: A total of 100 specimens, including pus, sputum, hemoculture, urine, tissue, fluid, and skin scrap specimens, were grown in iron-deprived Luria broth agar. The isolates were investigated for spectral signature using MALDI–TOF/MS, while antibiotic susceptibility and siderophore content were assessed using the chrome azurol S method. Whole genome and partial 16S rRNA DNA sequences were employed, and VITEK/MS revealed specific spectra. Results: Clindamycin, erythromycin, gentamicin, linezolid, moxifloxacin, oxacillin, trimethoprim/sulfamethoxazole, and vancomycin (100%) were the most common antibiotics to which the S. aureus isolates were susceptible. Sfna was not detectable in fluid and skin scrap isolates, which were encoded by sfnaB, sfnaD, and sfnaB/sfnaD genes. However, they were detectable in pus (73.8%), sputum (85.3%), hemoculture (50.0%), and urine (85.7%) isolates. The aureus subspecies, JKD6159, SA268, and MN8, were found to be 72.73% according to genome sequencing. Conclusion: most staphylococci in the isolates, including S. aureus JKD6159, SA268, and MN8, were sensitive to antibiotics and were detected by MALDI–TOF/MS, resulting in the production of Sfna encoded by sfna genes. Full article