Evaluation of three commercial methods of susceptibility testing for ceftolozane/tazobactam against carbapenem-resistant Pseudomonas aeruginosa / Evaluación de 3 métodos comerciales de determinación de sensibilidad de ceftolozano/tazobactam frente a Pseudomonas aeruginosa resistente a las carbapenemas

Introduction: Ceftolozane/tazobactam has shown excellent activity against Pseudomonas aeruginosa, but this drug is not always included in commercial panels. The aim of the study was to evaluate the performance of 2 gradient strips (BioMérieux and Liofilchem) and a commercial microdilution panel (Sensititre, EURGNCOL panel) using this combination against carbapenem-resistant P. aeruginosa isolates. Methods: Three commercial methods were tested with 41 metallo-beta-lactamase-producing and 59 non-carbapenemase-producing P. aeruginosa isolates. Broth microdilution was used as reference. Results: All carbapenemase-producing isolates and only one non-producing isolate were resistant to this antibiotic. Both essential agreement and bias were outside the acceptance intervals since MIC values were higher than reference values for all three methods. The Kappa index indicated poor or weak agreement. Changes in clinical categories were observed in 3 isolates. Conclusions: The three methods yielded poor agreement with the reference. Despite the differences in MIC values, fewer than 3% involved category changes.(AU)

Introducción: La combinación ceftolozano/tazobactam ha mostrado una actividad excelente frente a Pseudomonas aeruginosa, pero este fármaco no siempre se incluye en los paneles comerciales. El objetivo de este estudio es evaluar el rendimiento de 2 tiras de gradiente (BioMérieux® y Liofilchem®) y un panel de microdilución comercial (Sensititre®, panel EURGNCOL) utilizando esta combinación frente a aislados de P. aeruginosa resistente a los carbapenémicos. Métodos: Se probaron 3 métodos comerciales con 41 aislados productores de metalobetalactamasas y 59 aislados no productores de carbapenemasas de P. aeruginosa. La microdilución de caldo se utilizó como referencia. Resultados: Todos los aislados productores de carbapenemasas y solo un aislado no productor fueron resistentes a este antibiótico. Tanto la concordancia esencial como el sesgo se encontraron fuera de los intervalos de aceptación, dado que los valores CMI eran superiores que los valores de referencia para los 3 métodos. El índice de Kappa indicó una concordancia pobre o débil. Se observaron cambios en las categorías clínicas en 3 aislados. Conclusiones: Los 3 métodos presentaron una baja concordancia con la microdilución de referencia. A pesar de las diferencias en los valores MIC, menos del 3% implicaron cambios de categoría.(AU)

Evaluation of three commercial methods of susceptibility testing for ceftolozane/tazobactam against carbapenem-resistant Pseudomonas aeruginosa.

INTRODUCTION: Ceftolozane/tazobactam has shown excellent activity against Pseudomonas aeruginosa, but this drug is not always included in commercial panels. The aim of the study was to evaluate the performance of 2 gradient strips (BioMérieux and Liofilchem) and a commercial microdilution panel (Sensititre, EURGNCOL panel) using this combination against carbapenem-resistant P. aeruginosa isolates. METHODS: Three commercial methods were tested with 41 metallo-beta-lactamase-producing and 59 non-carbapenemase-producing P. aeruginosa isolates. Broth microdilution was used as reference. RESULTS: All carbapenemase-producing isolates and only one non-producing isolate were resistant to this antibiotic. Both essential agreement and bias were outside the acceptance intervals since MIC values were higher than reference values for all three methods. The Kappa index indicated poor or weak agreement. Changes in clinical categories were observed in 3 isolates. CONCLUSIONS: The three methods yielded poor agreement with the reference. Despite the differences in MIC values, fewer than 3% involved category changes.

Photodynamic Therapy Combined with Antibiotics or Antifungals against Microorganisms That Cause Skin and Soft Tissue Infections: A Planktonic and Biofilm Approach to Overcome Resistances.

The present review covers combination approaches of antimicrobial photodynamic therapy (aPDT) plus antibiotics or antifungals to attack bacteria and fungi in vitro (both planktonic and biofilm forms) focused on those microorganisms that cause infections in skin and soft tissues. The combination can prevent failure in the fight against these microorganisms: antimicrobial drugs can increase the susceptibility of microorganisms to aPDT and prevent the possibility of regrowth of those that were not inactivated during the irradiation; meanwhile, aPDT is effective regardless of the resistance pattern of the strain and their use does not contribute to the selection of antimicrobial resistance. Additive or synergistic antimicrobial effects in vitro are evaluated and the best combinations are presented. The use of combined treatment of aPDT with antimicrobials could help overcome the difficulty of fighting high level of resistance microorganisms and, as it is a multi-target approach, it could make the selection of resistant microorganisms more difficult.

Photodynamic Inactivation of Staphylococcus aureus Biofilms Using a Hexanuclear Molybdenum Complex Embedded in Transparent polyHEMA Hydrogels.

Three new photoactive polymeric materials embedding a hexanuclear molybdenum cluster (Bu4N)2[Mo6I8(CH3COO)6] (1) have been synthesized and characterized by means of Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and emission spectroscopy. The materials are obtained in the format of transparent and thin sheets, and the formulations used to synthesize them are comprised of 2-hydroxyethyl methacrylate (HEMA), as a polymerizable monomer, and ethylene glycol dimethacrylate (EGDMA) or poly(ethylene glycol)dimethacrylate (PEGDMA), as cross-linkers. All the polymeric hydrogels generate singlet oxygen (1O2) upon irradiation with visible light (400-700 nm), as demonstrated by the reactivity toward two chemical traps of this reactive species (9,10-dimethylanthracene and 1,5-dihydroxynaphthalene). Some differences have been detected between the photoactive materials, probably attributable to variations in the permeability to solvent and oxygen. Notably, one of the materials resisted up to 10 cycles of photocatalytic oxygenation reactions of 1,5-dihydroxynaphthalene. All three of the polyHEMA hydrogels doped with 1 are efficient against S. aureus biofilms when irradiated with blue light (460 nm). The material made with the composition of 90% HEMA and 10% PEGDMA (Mo6@polymer-III) is especially easy to handle, because of its flexibility, and it achieves a notable level of bacterial population reduction (3.0 log10 CFU/cm2). The embedding of 1 in cross-linked polyHEMA sheets affords a protective environment to the photosensitizer against aqueous degradation while preserving the photochemical and photobactericidal activity.

Photodynamic therapy using methylene blue, combined or not with gentamicin, against Staphylococcus aureus and Pseudomonas aeruginosa.

Antimicrobial photodynamic therapy (a-PDT), combined or not with antibiotics, constitutes a promising therapy for superficial infections caused by bacteria implicated in multidrug resistance processes. We compared the efficacy of aPDT using the photosensitizer methylene blue (MB), combined or not with the antibiotic gentamicin (GN), against Staphylococcus aureus and Pseudomonas aeruginosa. Different concentrations of MB (0.03-7000 µg/mL), with or without GN (1-20 µg/mL), were added to planktonic cultures or biofilms and the samples irradiated with a LED lamp (λ 625 nm, 7 mW/cm2, 18 J/cm2). The number of viable bacteria in the samples and in corresponding nonirradiated controls was quantified by counting colony-forming units to evaluate the individual effects of MB, GN, and irradiation. MB-aPDT resulted in significant bacterial photoinactivation. The combination of GN and MB-aPDT exerted a synergistic bactericidal effect against planktonic cultures of S. aureus and P. aeruginosa. This combination did not significantly alter the photoinactivating effect of MB against S. aureus biofilms, but exerted a positive bactericidal effect against P. aeruginosa biofilms. These results underscore the need for further clinical studies of this therapeutic combination for the management of difficult-to-treat skin and mucous infections, especially those caused by P. aeruginosa.

Antimicrobial photodynamic activity of Rose Bengal, alone or in combination with Gentamicin, against planktonic and biofilm Staphylococcus aureus.

Antimicrobial photodynamic therapy (aPDT) could constitute an alternative therapy to antibiotics especially against superficial infections caused by bacteria involved in multidrug resistance processes. The aim of this study is to compare the efficacy of aPDT using the photosensitizer rose bengal (RB), combined or uncombined with gentamicin (GN), against Staphylococcus aureus. Different concentrations of RB (ranging from 0.03 to 64 µg/ml) were added to S. aureus in water suspensions or forming biofilms in the absence or presence of GN (1-40 µg/ml) and the samples were irradiated (18 or 37 J/cm2). The number of viable bacteria was quantified by counting colony-forming units. RB-aPDT shows significant photoactivity. The combination of GN and RB-aPDT exerts a synergistic bactericidal effect against planktonic S. aureus. On the other hand, a synergistic effect is observed only when the maximum concentration tested of RB and GN was used in biofilm. According to these result the use of RB-aPDT alone or in combination with GN could be implemented against S. aureus.

Bactericidal Effect of Photodynamic Therapy, Alone or in Combination with Mupirocin or Linezolid, on Staphylococcus aureus.

Antibiotic treatments frequently fail due to the development of antibiotic resistance, underscoring the need for new treatment strategies. Antimicrobial photodynamic therapy (aPDT) could constitute an alternative therapy. In bacterial suspensions of Staphylococcus aureus, which is commonly implicated in cutaneous and mucosal infections, we evaluated the in vitro efficacy of aPDT, using the photosensitizing agents rose bengal (RB) or methylene blue (MB), alone or combined with the antibiotics mupirocin (MU) or linezolid (LN). RB or MB, at concentrations ranging from 0.03 to 10 µg/ml, were added to S. aureus ATCC 29213 suspensions containing >108 cells/ml, in the absence or presence of MU or LN (1 or 10 µg/ml). Suspensions were irradiated with a white metal halide (λ 420-700 nm) or light-emitting diode lamp (λ 515 and λ 625 nm), and the number of viable bacteria quantified by counting colony-forming units (CFU) on blood agar. Addition of either antibiotic had no significant effect on the number of CFU/ml. By contrast, RB-aPDT and MB-aPDT effectively inactivated S. aureus, as evidenced by a 6 log10 reduction in bacterial growth. In the presence of MU or LN, the same 6 log10 reduction was observed in response to aPDT, but was achieved using significantly lower concentrations of the photosensitizers RB or MB. In conclusion, the combination of MU or LN and RB/MB-aPDT appears to exert a synergistic bactericidal effect against S. aureus in vitro.

Antimicrobial photodynamic activity of hypericin against methicillin-susceptible and resistant Staphylococcus aureus biofilms.

AIM: To evaluate the effectiveness of the photodynamic therapy using hypericin (HYP) against both planktonic and biofilm-forming Staphylococcus aureus. MATERIALS & METHODS: HYP photoactivity was evaluated against methicillin-susceptible and resistant S. aureus. Bacterial suspension or biofilm were preincubated with HYP and subjected to LED illumination. Viable bacteria were determined by colony counting. RESULTS: Preincubation with HYP (5 min) plus light exposure (10 min) showed bactericidal effect against planktonic methicillin-susceptible S. aureus and methicillin-resistant S. aureus. Longer preincubation times (24 h) and time light exposure (30 min) were required to reach HYP-photoactivity against S. aureus biofilms. HYP-photoactivity was correlated to the biofilm production. CONCLUSION: HYP could be a potential photosensitizer for the inactivation of staphylococcal biofilms forming on the surfaces accessible to visible light.

Assessment of periodontal and opportunistic flora in patients with peri-implantitis.

AIM: To assess the presence of periodontal and opportunistic organisms in patients with peri-implantitis. MATERIAL AND METHODS: Thirty-three partially edentulous subjects (22 women, 11 men), aged 32-90 years, who had one or more implants with peri-implantitis were included. Peri-implantitis was defined as: (i) the presence of bleeding on probing and/or suppuration and (ii) radiographic images showed marginal bone loss >1.8 mm after 1 year in function. Criteria for inclusion were: (i) partially edentulous patients having at least one implant diagnosed with peri-implantitis; (ii) no antibiotic therapy for 6 months prior to clinical examination. Following this definition, a total of 48 implants were diagnosed with peri-implantitis. Subgingival bacterial samples were obtained with sterile paper points from infected implants and selected teeth of each individual. Periodontopathogens (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia and Treponema denticola) were detected by multiplex PCR targeting 16S rDNA. Samples were placed in reduced transport medium and cultured for opportunistic pathogens (Staphylococcus aureus, enteric bacteria, Pseudomonas and yeasts). RESULTS: Twenty-two patients yielded positive results for P. gingivalis, 25 for T. forsythia, eight for P. intermedia and 13 for T. denticola. None of the patients yielded a positive result for A. actinomycetemcomitans. Non-periodontal species were found in five patients (15% of total). P. aeruginosa was found in four (12%) patients, and C. albicans (3%) and S. aureus in one patient (3%) each. In two cases of peri-implantitis, none of the periodontal or opportunistic microorganisms studied were detected in either implant or tooth samples. When results of the periodontopathic bacteria from the implant and tooth samples of the same patient were compared, 18 patients (54%) showed the same results for both samples and 15 (45%) patients different results. CONCLUSIONS: The implant surface may be colonized with pathogens different from periodontal bacteria. Opportunistic pathogens such as P. aeruginosa, S. aureus and C. albicans may be associated with implant failure.

Postorthodontic external root resorption in root-filled teeth is influenced by interleukin-1ß polymorphism.

INTRODUCTION: External apical root resorption (EARR) is a frequent iatrogenic effect of orthodontic treatment. The way root-filled teeth respond to orthodontic forces with respect to EARR has been reported as varying widely between individuals. Genetic variants in the interleukin-1 gene have been associated with an increased risk of experiencing postorthodontic EARR on vital teeth. The objective of this study is to determine whether variants in the interleukin-1 gene have a positive or negative influence on EARR on teeth that have been endodontically treated. METHODS: Ninety-three orthodontic patients underwent genetic screening for 2 single nucleotide polymorphisms (rs1800587, rs1143634) in the IL1 gene cluster. Subjects were divided into 2 groups depending on the presence (affected group) or absence (control group) of more than 2 mm of EARR on root-filled teeth after orthodontic treatment as shown by radiography. Logistic regression analysis was used to obtain adjusted estimates of EARR and IL1 polymorphisms. Allele frequencies, genotype distributions, and adjusted odds ratios were also calculated (95% confidence interval). RESULTS: No positive or negative statistical association was found between postorthodontic treatment EARR in root-filled teeth and genetic variations in IL1A (P > .05). A direct relationship was found for the IL1B gene in the comparative analysis of homozygous subjects (2/2[TT]) and (1/1[CC]), which led to an increased risk of experiencing postorthodontic treatment EARR in root-filled teeth (odds ratio = 11.59; P = .006; confidence interval, 95%) and (odds ratio = 2.54; P = .035; confidence interval, 95%), respectively. CONCLUSIONS: The development of EARR in subjects with root-filled teeth who undergo orthodontic treatment might be attributable to genetic variations in the interleukin-1ß gene (rs1143634).

Intracellular penetration and activity of UB-8902 in human polymorphonuclear leukocytes

Se ha evaluado la penetración intracelular y la actividad de UB-8902 en leucocitos polimorfomucleares humanos. La concentración intracelular de UB-8902 fue más de 6 veces superior a la concentración extracelular. La penetración intracelular fue un proceso rápido, reversible, saturable y no se afectó por el pH del medio. UB-8902 se mostró activo intracelularmente frente a cepas de Staphylococcus aureus que presentaban mutaciones en los genes gyrA y/o grlA, asociadas a resistencia a fluorquinolonas (AU)

The intracellular penetration and activity of UB-8902 in human polymorphonuclear leukocytes was evaluated. Intracellular UB-8902 concentrations were 6-fold higher than extracellular levels. Uptake was rapid, reversible, saturable, and affected by external pH. UB-8902 showed intracellular activity against Staphylococcus aureus strains presenting mutations associated with fluoroquinolone resistance in the gyrA and/or grlA genes (AU)

Intracellular penetration and activity of UB-8902 in human polymorphonuclear leukocytes.

The intracellular penetration and activity of UB-8902 in human polymorphonuclear leukocytes was evaluated. Intracellular UB-8902 concentrations were 6-fold higher than extracellular levels. Uptake was rapid, reversible, saturable, and affected by external pH. UB-8902 showed intracellular activity against Staphylococcus aureus strains presenting mutations associated with fluoroquinolone resistance in the gyrA and/or grlA genes.

[Fresh versus pasteurized yogurt: comparative study of the effects on microbiological and immunological parameters, and gastrointestinal comfort]. / Yogures frescos frente a pasteurizados: estudio comparativo de sus efectos sobre los parámetros microbiológicos, inmunológicos y el bienestar gastrointestinal.

OBJECTIVE: To determine whether the beneficial effects of yogurt are dependent on the viability of lactic bacteria and exclusive to fresh yogurt, by comparison with the effects of yogurt that is pasteurized after fermentation. MATERIAL AND METHOD: Using a double-blind design in a healthy adult population over 75 days, we compared the effects of fresh and pasteurized yogurt on microbiological (presence of viable bacteria in yogurt and DNA detection in feces) and immunological (nephelometry, hematometry, and flow cytometry) parameters. A questionnaire was used to assess gastrointestinal comfort. Differences in lactose absorption after ingestion of fresh or pasteurized yogurt were determined by breath hydrogen analysis. RESULTS: There were no significant differences in the results obtained for microbiological or immunological parameters, gastrointestinal comfort, or lactose test between the two types of yogurt ingested. Lactobacillus delbrueckii ssp. bulgaricus (L. bulgaricus) was isolated in 0.7% of the fecal samples analyzed. Streptococcus thermophilus was not found in any sample. DNA from lactic bacteria was detected in only 12.5% of the samples analyzed. CONCLUSION: Transit through the gastrointestinal tract affects survival of L. bulgaricus and S. thermophilus. No differences were found in the immunological parameters, gastrointestinal comfort, or lactose overload after intake of fresh or pasteurized yogurt.

Yogures frescos frente a pasteurizados: estudio comparativo de sus efectos sobre los parámetros microbiológicos, inmunológicos y el bienestar gastrointestinal / Fresh versus pasteurized yogurt: comparative study of the effects on microbiological and immunological parameters, and gastrointestinal comfort

OBJETIVO. Determinar si los efectos beneficiosos del yogur dependen de la viabilidad de las bacterias lácticas y son exclusivos de los yogures frescos, en comparación con los obtenidos de los yogures pasteurizados tras la fermentación. MATERIAL Y MÉTODO. Mediante un ensayo enmascarado en una población adulta sana y durante 75 días, comparamos los efectos de la ingestión de yogures frescos y pasteurizados sobre los parámetros microbiológicos(presencia de bacterias vivas del yogur y detección de ADN en heces) e inmunológicos (mediante nefelometría, hematimetría y citometría de flujo). Con un cuestionario se evaluó el bienestar gastrointestinal y se utilizó una prueba de aliento para medir las diferencias en un ensayo de sobrecarga de lactosa tras el consumo de yogures. RESULTADOS. No hubo diferencias significativas entre los resultados obtenidos para los parámetros inmunológicos, bienestar gastrointestinal y sobrecarga de lactosa de los voluntarios tras el consumo de yogures, con independencia del tipo de yogur ingerido. Lactobacillus delbrueckii ssp. bulgaricus (L. bulgaricus) sólo se aisló en el 0,7% de las muestras de heces analizadas. Streptococcus thermophilus no se aisló en ninguna de las muestras. EL ADN de las bacterias lácticas del yogur sólo fue detectado en el 12,5% de las muestras analizadas. CONCLUSIÓN. El tránsito gástrico afectó a la supervivencia de L. bulgaricus y S. thermophylus. No se encontraron diferencias respecto a los efectos que la ingestión de yogures frescos o pasteurizados pudieran tener sobre los parámetros inmunológicos, los valores de las pruebas desobrecarga de lactosa, ni sobre el bienestar gastrointestinal (AU)

OBJECTIVE. To determine whether the beneficial effects of yogurt are dependent on the viability of lactic bacteria and exclusive to fresh yogurt, by comparison with the effects of yogurt that is pasteurized after fermentation. MATERIAL AND METHOD. Using a double-blind design in a healthy adult population over 75 days, we compared the effects of fresh and pasteurized yogurt on microbiological(presence of viable bacteria in yogurt and DNA detection in feces) and immunological (nephelometry, hematometry, and flow cytometry) parameters. A questionnaire was used to assess gastrointestinal comfort. Differences in lactose absorption after ingestion of fresh or pasteurized yogurt were determined by breath hydrogen analysis. RESULTS. There were no significant differences in the results obtained for microbiological or immunological parameters, gastrointestinal comfort, or lactose test between the two types of yoghourt ingested. Lactobacillusdelbrueckii ssp. bulgaricus (L. bulgaricus) was isolated in 0.7% of the fecal samples analyzed. Streptococcusthermophilus was not found in any sample. DNA from lactic bacteria was detected in only 12.5% of the samples analyzed. CONCLUSION. Transit through the gastrointestinal tract affects survival of L. bulgaricus and S. thermophilus. Nodifferences were found in the immunological parameters, gastrointestinal comfort, or lactose overload after intake of fresh or pasteurized yogurt (AU)

[Activity and penetration of linezolid and vancomycin against Staphylococcus epidermidis biofilms]. / Actividad y permeabilidad de linezolid y vancomicina en biocapas de Staphylococcus epidermidis.

INTRODUCTION: The activity and capacity for penetration of linezolid and vancomycin were comparatively evaluated against Staphylococcus epidermidis biofilms. METHODS: The activity of linezolid versus vancomycin was assessed against 24-hour S. epidermidis biofilms developed on silicon catheters. Penetration of the two antimicrobial agents was measured in biofilms developed on polycarbonate membrane filters. Penetration and activity were comparatively tested using S. epidermidis, slime-producing and non-slime-producing strains. RESULTS: The activity of linezolid against S. epidermidis biofilms was significantly greater than that of vancomycin for both strains. Neither antimicrobial completely eradicated bacterial survival in 24-hour biofilms. Linezolid penetration in biofilms was greater than that of vancomycin for both S. epidermidis strains. CONCLUSIONS: Linezolid showed higher in vitro activity than vancomycin against S. epidermidis biofilms on silicone catheters. This effect may be due to the capability of linezolid to cross the bacterial biofilm.

Intracellular penetration and activity of DX-619 in human polymorphonuclear leukocytes.

The intracellular penetration and activity of DX-619 in human polymorphonuclear leukocytes have been evaluated. DX-619 reached intracellular concentrations 10 times higher than the extracellular concentrations reached. Uptake was rapid, reversible, nonsaturable, and affected by environmental temperature, some metabolic inhibitors, and a soluble membrane activator. DX-619 showed intracellular activity against Staphylococcus aureus.

Uptake and intracellular activity of voriconazole in human polymorphonuclear leucocytes.

OBJECTIVES: The intracellular penetration of voriconazole into human polymorphonuclear leucocytes (PMNs) and its intracellular activity against Candida spp. were evaluated. METHODS: The intracellular penetration of voriconazole into PMNs was evaluated by a radiometric assay. The effect of cell viability, environmental conditions, metabolic inhibitors and membrane stimulation was also studied. The intracellular activity was determined by incubation of PMNs containing intracellular blastospores in the presence of voriconazole for 3 h. RESULTS: The uptake of voriconazole by PMNs was rapid and not saturable. The cellular to extracellular concentration (C/E) ratio for voriconazole was 8.5+/-1.3. Voriconazole was rapidly released from loaded PMNs. The uptake of voriconazole was not affected by environmental temperature and cell viability. Neither the external pH nor the metabolic inhibitors affected the uptake of voriconazole. The ingestion of opsonized zymosan, but not of opsonized Candida spp., significantly decreased the levels of PMN-associated voriconazole. At the extracellular concentrations evaluated, voriconazole did not affect the intracellular survival of Candida. CONCLUSIONS: Voriconazole reached high intracellular concentrations within human PMNs. The uptake was rapid and not saturable but it did not affect the intracellular killing of Candida spp.

Effect of linezolid on the phagocytic functions of human polymorphonuclear leukocytes.

The effect of linezolid on the phagocytic and bactericidal functions of human polymorphonuclear neutrophils (PMN) against gram-positive cocci was evaluated. Preincubation (30 min; 37 degrees C) of PMN with different concentrations of linezolid (2, 10 and 20 mg/l) did not significantly affect the phagocytosis of either Staphylococcus aureus (methicillin susceptible and resistant) or Enterococcus faecalis (vancomycin susceptible and resistant). Overnight exposure of vancomycin-resistant E. faecalis to 1/4 minimum inhibitory concentrations (MIC) of linezolid slightly increased phagocytosis by PMN. Preincubation of the other three strains with 1/4 MIC of linezolid did not affect phagocytosis by these cells. Preincubation of PMN (30 min; 37 degrees C) using different extracellular concentrations of linezolid (2, 10 and 20 mg/l) did not affect their production of either superoxide or hydrogen peroxide radicals. In conclusion, linezolid did not affect the phagocytic and bactericidal functions of human PMN.