Effects of enrofloxacin on porcine phagocytic function

The Prophylactic Protection of Salmonella Typhimurium Infection by Lentilactobacillus buchneri GX0328-6 in Mice

Salmonellosis is a disease caused by non-typhoid Salmonella, and although some lactic acid bacteria strains have been shown previously to relieve Salmonellosis symptoms, little has been studied about the preventive mechanism of Lentilactobacillus buchneri (L. buchneri) against Salmonella infection in vivo. Therefore, the L. buchneri was fed to C57BL/6 mice for 10 days to build a protective system of mice to study its prevention and possible mechanisms. The results showed that L. buchneri GX0328-6 alleviated symptoms caused by Salmonella typhimurium infection among C57BL/6 mice, including low survival rate, weight loss, increase in immune organ index and hepatosplenomegaly, and modulated serum immunoglobulin levels and intrinsic immunity. Importantly, the L. buchneri GX0328-6 enhanced the mucosal barrier of the mouse jejunum by upregulating the expression of tight junction proteins such as ZO-1, occludins, and claudins-4 and improved absorptive capacity by increasing the length of mouse jejunal villus and the ratio of villus length to crypt depth and decreasing the crypt depth. L. buchneri GX0328-6 reduced the intestinal proliferation and invasion of Salmonella typhimurium by modulating the expression of antimicrobial peptides in the intestinal tract of mice, and reduced intestinal inflammation and systemic spread in mice by downregulating the expression of IL-6 and promoting the expression of IL-10. Furthermore, L. buchneri GX0328-6 increased the relative abundance of beneficial bacteria colonies and decreased the relative abundance of harmful bacteria in the cecum microflora by modulating the microflora in the cecum contents.

Intracellular delivery, accumulation, and discrepancy in antibacterial activity of four enrofloxacin-loaded fatty acid solid lipid nanoparticles

Four fatty acid-solid lipid nanoparticles (SLNs) were formulated and evaluated for intracellular delivery, accumulation, as well as discrepancy in antimicrobial efficacy of their loaded enrofloxacin by using RAW 264.7 cells. The delivery efficacy of enrofloxacin into the macrophages by docosanoic acid SLNs (DAS), octadecanoic acid SLNs (OAS), hexadecanoic acid SLNs (HAS), and tetradecanoic acid SLNs (TAS) were 26.1-29.0, 9.3-10.3, 4.7-5.3 and 4.5-5.0 folds, respectively, compared to free drug when co-incubation for 0.25-4 h. The longer fatty acid prepared nanoparticles loaded enrofloxacin eliminated more slowly and accumulated in the cells for a longer time.The confocal microscopy also demonstrated that higher amount of fatty acid SLNs entered the cells with stronger accumulation performance and less amount SLNs absorbed on the cytomembrane as the carbon chain of fatty acids increased. The bactericidal activity of the four fatty acid SLNs against intracellular Salmonella CVCC541 significantly enhanced compared to the free enrofloxacin. These results revealed that fatty acid SLNs, especially docosanoic acid nanoparticles, might be effective nanocarriers to ferry enrofloxacin or other lipid soluble drugs into cells for intracellular bacterial infection treatment.

Inhibition of Salmonella Typhimurium adhesion, invasion, and intracellular survival via treatment with methyl gallate alone and in combination with marbofloxacin

Salmonella enterica serovar Typhimurium infects intestinal epithelia and macrophages, which is prevented by inhibiting adhesion and cell invasion. This study aimed to investigate the role of methyl gallate (MG) in adhesion, invasion, and intracellular survival of Salmonella Typhimurium in Caco-2 and RAW 264.7 cells via a gentamicin protection assay, confocal microscopy, and quantitative reverse-transcription polymerase chain reaction. MG (30 µg/mL) inhibited adhesion and invasion of Salmonella Typhimurium by 54.01% and 60.5% in RAW 264.7 cells, respectively. The combination of MG with sub-minimum inhibitory concentration (MIC) of marbofloxacin (MRB) inhibited the adhesion, invasion, and intracellular survival by 70.49%, 67.36%, and 74%, respectively. Confocal microscopy further revealed reductions in bacterial count in Caco-2 cells treated with MG alone or with sub-MIC of MRB. Furthermore, MG alone or in combination with sub-MIC of MRB decreased the motility of Salmonella Typhimurium. Quorum sensing genes including sdiA, srgE, and rck were downregulated by 52.8%, 61.7%, and 22.2%, respectively. Moreover, rac-1 was downregulated by 56.9% and 71.9% for MG alone and combined with sub-MIC of MRB, respectively, in mammalian cells. Furthermore, MG downregulated virulence genes of Salmonella Typhimurium including cheY, ompD, sipB, lexA, and ompF by 59.6%, 60.2%, 20.5%, 31.4%, and 16.2%, respectively. Together, the present results indicate that MG alone or in combination with a sub-MIC of MRB effectively inhibited the adhesion, invasion, and intracellular survival of Salmonella Typhimurium in vitro by downregulating quorum sensing and virulence genes.

Bactericidal and Anti-biofilm Effects of Polyhexamethylene Biguanide in Models of Intracellular and Biofilm of Staphylococcus aureus Isolated from Bovine Mastitis

Staphylococcus aureus infection is a common cause of mastitis, reducing milk yield, affecting animal welfare and causing huge economic losses within the dairy industry. In addition to the problem of acquired drug resistance, bacterial invasion into udder cells and the formation of surface biofilms are believed to reduce antibiotic efficacy, leading to treatment failure. Here, we investigated the antimicrobial activities of enrofloxacin, an antibiotic that is commonly used in mastitis therapy and polyhexamethylene biguanide (PHMB), an antimicrobial polymer. The antimicrobial activities were tested against intracellular S. aureus in infected Mac-T cells (host cells). Also, fluorescein-tagged PHMB was used to study PHMB uptake and localization with S. aureus within the infected Mac-T cells. Anti-biofilm activities were tested by treating S. aureus biofilms and measuring effects on biofilm mass in vitro. Enrofloxacin and PHMB at 15 mg/L killed between 42 to 92 and 99.9% of intracellular S. aureus, respectively. PHMB-FITC entered and colocalized with the intracellular S. aureus, suggesting direct interaction of the drug with the bacteria inside the host cells. Enrofloxacin and PHMB at 15 mg/L reduced between 10 to 27% and 28 to 37% of biofilms' mass, respectively. The half-maximal inhibitory concentrations (IC₅₀) obtained from a cytotoxicity assay were 345 ± 91 and 21 ± 2 mg/L for enrofloxacin and PHMB, respectively; therefore, both compounds were tolerated by the host cells at high concentrations. These findings suggest that both antimicrobials are effective against intracellular S. aureus and can disrupt biofilm structures, with PHMB being more potent against intracellular S. aureus, highlighting the potential application of PHMB in mastitis therapy.

Enrofloxacin in therapeutic doses alters cytokine production by porcine PBMCs induced by lipopolysaccharide

The effect of enrofloxacin on cytokine secretion by porcine peripheral blood mononuclear cells (PBMCs) was studied. Twenty 8-20-week-old pigs were randomly divided into two groups: control (C, n = 10) and experimental (E, n = 10) were used. Pigs from group E received enrofloxacin at therapeutic dose for 5 consecutive days. Blood samples were collected at 0 (before antibiotic administration), 2, 4 (during antibiotic therapy) 6, 9, 14 21, 35, 49, and 63 d of study (after treatment). PBMCs of pigs from both groups were incubated with or without lipopolysaccharide (LPS). Ex vivo production on interleukin (IL)-4, IL-6, IL-10, INF-γ, and TNF-α were analyzed using ELISA assay. Intramuscular administration of enrofloxacin to healthy pigs for 5 consecutive days induced a transitory reduction of the ex vivo response of PBMCs to LPS in terms of IL-6 and TNF-α secretion. The level of IL-6 returned to day 0 level shortly after end of treatment, while the TNF-α production remained reduced 10 d after the end of treatment. Our results indicate that enrofloxacin given in vivo in therapeutic doses has an immunomodulatory effect through its capacity to inhibit ex vivo secretion of IL-6 and TNF-α by porcine PBMC after LPS stimulation.

Enhanced intracellular delivery and antibacterial efficacy of enrofloxacin-loaded docosanoic acid solid lipid nanoparticles against intracellular Salmonella

Enrofloxacin-loaded docosanoic acid solid lipid nanoparticles (SLNs) with different physicochemical properties were developed to enhance activity against intracellular Salmonella. Their cellular uptake, intracellular elimination and antibacterial activity were studied in RAW 264.7 cells. During the experimental period, SLN-encapsulated enrofloxacin accumulated in the cells approximately 27.06-37.71 times more efficiently than free drugs at the same extracellular concentration. After incubation for 0.5 h, the intracellular enrofloxacin was enhanced from 0.336 to 1.147 μg/mg of protein as the sizes of nanoparticles were increased from 150 to 605 nm, and from 0.960 to 1.147 μg/mg of protein when the charge was improved from -8.1 to -24.9 mv. The cellular uptake was more significantly influenced by the size than it was by the charge, and was not affected by whether the charge was positive or negative. The elimination of optimal SLN-encapsulated enrofloxacin from the cells was significantly slower than that of free enrofloxacin after removing extracellular drug. The inhibition effect against intracellular Salmonella CVCC541 of 0.24 and 0.06 μg/mL encapsulated enrofloxacin was stronger than 0.6 μg/mL free drug after all of the incubation periods and at 48 h, respectively. Docosanoic acid SLNs are thus considered as a promising carrier for intracellular bacterial treatment.

Haemophilus parasuis: infection, immunity and enrofloxacin

Haemophilus parasuis is an early colonizer of the porcine upper respiratory tract and is the etiological agent of Glasser’s disease. The factors responsible for H. parasuis colonization and systemic infection are not yet well understood, while prevention and control of Glasser’s disease continues to be challenging. Recent studies on innate immunity to H. parasuis have demonstrated that porcine alveolar macrophages (PAMs) are able to differentially up-regulate several genes related to inflammation and phagocytosis, and several pro-inflammatory cytokines are produced by porcine cells upon exposure to H. parasuis. The susceptibility of H. parasuis strains to phagocytosis by PAMs and the bactericidal effect of complement are influenced by the virulent phenotype of the strains. While non-virulent strains are susceptible to phagocytosis and complement, virulent strains are resistant to both. However, in the presence of specific antibodies against H. parasuis, virulent strains become susceptible to phagocytosis. More information is still needed, though, in order to better understand the host immune responses to H. parasuis. Antimicrobials are commonly used in the swine industry to help treat and control Glasser’s disease. Some of the common antimicrobials have been shown to reduce colonization by H. parasuis, which may have implications for disease dynamics, development of effective immune responses and immunomodulation. Here, we provide the current state of research on innate and adaptive immune responses to H. parasuis and discuss the potential effect of enrofloxacin on the development of a protective immune response against H. parasuis infection.

In vivo comparative pharmacokinetics and pharmacodynamics of moxifloxacin and levofloxacin in human neutrophils

OBJECTIVE

Most of the newer fluoroquinolones are active against bacteria such as Streptococcus pneumoniae and Staphylococcus aureus, which are able to multiply inside polymorphonuclear leukocytes (PMNs). The aim of this study was to determine moxifloxacin and levofloxacin intracellular behaviour with their usual dosage regimen.

METHODS

We determined the pharmacokinetics of moxifloxacin and levofloxacin at steady state in the PMNs of ten healthy volunteers receiving moxifloxacin 400mg and levofloxacin 500mg as a once-daily dosing regimen for 3 days.

RESULTS

Both antibacterials showed a high level of intracellular penetration exhibiting PMNs/plasma ratios of 17.34 +/- 8.29 for moxifloxacin versus 8.15 +/- 5.23 for levofloxacin for maximum concentrations (C(max)) and 14.72 +/- 8.29 for moxifloxacin versus 8.15 +/- 5.23 for levofloxacin for the area under the plasma concentration-time curve. Estimation of the most predictive pharmacodynamic surrogate markers for concentration-dependent bactericidal antibacterials in the intracellular milieu by taking into account the susceptibility of S. pneumoniae and methicillin-susceptible S. aureus demonstrated consistently higher values with moxifloxacin than with levofloxacin, even though with both drugs the levels obtained are well above the recommended targets values. Indeed, C(max)/MIC ratios calculated in PMNs for moxifloxacin were 287.3 and 718.2 for S. pneumoniae and S. aureus, respectively, and for levofloxacin were 25.6 and 205.1, respectively.

CONCLUSION

Moxifloxacin and levofloxacin seem to be well adapted for the treatment of infections due to susceptible intracellular bacteria, and moxifloxacin provides a greater margin of safety than levofloxacin.

The influence of antibiotics on B-cell number, percentage, and distribution in the bursa of Fabricius of newly hatched chicks

Antibiotics are commonly used to prevent and treat poultry microbial infections, but certain antibiotic families depress humoral immunity, such as antibody production. Poultry humoral immunity depends on the normal functioning of the bursa of Fabricius and the B lymphocytes that mature in that gland. In this study, recommended therapeutic doses of enrofloxacin, florfenicol, or ceftiofur were administered to 2-d-old chicks. On d 7 post-hatch, bursae were sampled for histological, immunohistochemical, and flow cytometric determination of Bu-1-positive (Bu-1+) cell number, percentage, and distribution. The bursa of Fabricius from all treatment and control groups had normal morphology. The administration of antibiotics significantly decreased the number of Bu-1+ cells in the bursal medulla, with a simultaneous increase of these cells in the cortex. Flow cytometry revealed a significant decrease in the percentage of bursal Bu-1+ cells from all of the studied antibiotics: enrofloxacin (93.91 ± 3.27), florfenicol (87.84 ± 7.14), and ceftiofur (89.16 ± 5.68) compared with that of the control (96.48 ± 2.60). The combination of reduced percentages of Bu-1+ cells and a decrease in these cells in the medullary region suggests lower B cell maturation.

Responses of pigs to a re-challenge with Actinobacillus pleuropneumoniae after being treated with different antimicrobials following their initial exposure

Four groups of six specific pathogen-free (SPF) pigs were inoculated intranasally with Actinobacillus pleuropneumoniae serotype 2 and treated with either enrofloxacin, tetracycline or penicillin at the onset of clinical disease, or left untreated. A fifth group was left uninoculated. The inoculated control and the penicillin-treated groups developed severe disease, but the groups treated with enrofloxacin and tetracycline recovered rapidly. All the inoculated pigs, except those treated with enrofloxacin developed serum antibodies to A pleuropneumoniae. On day 28, all five groups were challenged with A pleuropneumoniae without any subsequent treatment. The previously uninoculated control group and the enrofloxacin-treated group developed severe disease, but the three seropositive groups remained unaffected.

Influence of fluoroquinolones on phagocytosis and killing of Candida albicans by human polymorphonuclear neutrophils

Candida albicans infections often occur during or shortly after antibacterial treatment. Phagocytosis by polymorphonuclear neutrophil granulocytes (PMN) is the most important primarily defence mechanism against C. albicans. Certain antibiotics such as some fluoroquinolones (FQ) are known to influence phagocyte functions. Thus, we investigated the influence of older and newer FQ on the phagocytosis and killing of C. albicans by human PMN paying special attention to CD11b expression of these cells as an indicator of the degree of their activation. In order to obtain comprehensive and comparable results we tested 13 FQ over a wide range of concentrations and in a time dependent manner in a standardized approach. When used at therapeutic concentrations, the FQ tested did not influence to a clinically significant degree the phagocytosis or the killing of C. albicans by human PMN and also not their activation. However, at high concentrations those FQ with cyclopropyl-moiety at position N1 showed increase in CD11b expression and diminished phagocytosis and oxidative burst.

The Nonantibiotic Anti-Inflammatory Effect of Antimicrobial Growth Promoters, the Real Mode of Action? A Hypothesis

Societal concern and government regulations increasingly press for restricting the use of antibiotics as antimicrobial growth promoters (AGP). The search for alternatives is on, hampered by a lack of knowledge about the exact mechanism of AGP. Feed additives, such as AGP and alternatives, interact with the intestine. In the intestine, feed components, microbiota, and the mucosa interact in a very complex and dynamic way. Various mechanisms for AGP have been proposed, invariably based on the direct antibiotic influence on the microbial composition of the intestines. In the literature on antibiotics, however, the direct effects of antibiotics on host cells, in particular inflammatory cells, have been described. It is curious that this has never been considered in the literature on AGP. Presently, a case is being made that AGP most likely work as growth permitters by inhibiting the production and excretion of catabolic mediators by intestinal inflammatory cells. Concomitant or subsequent changes in microflora are most likely the consequence of an altered condition of the intestinal wall. This common, basic mechanism potentially offers an excellent explanation for the highly reproducible effects of AGP, as opposed to those obtained by alternatives aimed at microflora management. Therefore, the search for alternatives could be aimed at nonantibiotic compounds with an effect on the inflammatory system similar to that of AGP.

Encapsulation of Enrofloxacin in Liposomes I: Preparation and In Vitro Characterization of LUV

Liposomes are effectively used in the treatment of microbial infections. Higher cellular uptake has been reported when antibiotics are encapsulated in liposomes. In this study, enrofloxacin (ENF) was encapsulated in large unilamellar vesicles (LUVs) and the effects of formulation variables on the liposome characteristics were investigated. Liposomes were prepared using dry lipid film method. A number of variables such as molar ratios of phospholipid (DPPC; DL-alpha-phosphatidylcholine dipalmitoyl), cholesterol, ENF and amount of alpha-tocopherol and the volumes of internal (chloroform) and external phases [phosphate buffered saline PBS (pH 7.4)] were studied. In vitro characterization of the liposomes including the encapsulation capacity, size and drug release properties were carried out. Using of this method, spherical LUV liposomes with high drug content could be produced. Particle size of liposomes changed between 3.12 and 4.95 microm. The molar ratios of DPPC, cholesterol and ENF affected the size of the liposome (p < 0.05). The drug encapsulation capacities were high and changed between 37.1% and 79.5%. The highest ENF encapsulation was obtained with the highest cholesterol content. An increase in the drug encapsulation capacity of the liposome was found with increasing molar ratios of DPPC, cholesterol and ENF (p < 0.05). Furthermore, the release of ENF from the liposomes decreased as the molar ratios of DPPC, cholesterol and ENF increased (p < 0.05). In conclusion, a convenient colloidal carrier for the controlled release of ENF can be prepared by changing the formulation parameters of LUVs.

Lactoferrin against Staphylococcus aureus Mastitis. Lactoferrin alone or in combination with penicillin G on bovine polymorphonuclear function and mammary epithelial cells colonisation by Staphylococcus aureus

Antibiotics should combine good antibacterial activity and the capacity to work in association with the host defence system. In this study, we have investigated the effects of bovine lactoferrin alone or in combination with penicillin G on the phagocytic activity of bovine polymorphonuclear leukocytes against Staphylococcus aureus. We have shown that susceptibility of S. aureus to phagocytosis was decreased in the presence of penicillin in the medium. In a kinetic study, lactoferrin alone did not affect phagocytosis but, when used with penicillin, it reversed the negative effect of this antibiotic on phagocytosis. In addition, in an epithelial invasion assay, lactoferrin alone or in combination with penicillin reduced the invasion of mammary epithelial cells in culture by S. aureus. Lactating female CD-1 mice were infected by intra-mammary delivery of a virulent penicillin-susceptible S. aureus strain and were then randomly assigned to treatments according to a 2 x 2 factorial design. In this mouse mastitis model, 2 days of systemic treatments with lactoferrin and/or penicillin did not lead to a total clearance of infection by S. aureus, but bacterial number was significantly reduced by treatments with lactoferrin or penicillin. These data suggest that bovine lactoferrin, alone or in combination with penicillin G, enhances S. aureus susceptibility to immuno-defense mechanisms, which can be beneficial in the treatment of S. aureus infections.

Determination of Intracellular Concentrations of Free and Two Types of Liposome-Encapsulated Enrofloxacin in Anatolian Shepherd Dog Monocytes

In this study, it was evaluated the accumulation of free and two types of liposome-encapsulated enrofloxacin (LEE) at the doses of 0.25, 0.5 and 1 microg/ml, which were clinically relevant concentrations into monocytes of healthy Anatolian shepherd dogs. Enrofloxacin was encapsulated with two different types of liposome in multilamellar large vesicles (MLV). Type A MLV composed of 15 mg egg phosphatidylcholine and 35 mg cholesterol, Type B MLV composed of phosphatidylcholine (PC), cholesterol and enrofloxacin, in a molar ratio of 1 : 1 : 1. The mean sizes of Type A and Type B liposome were found to be 7.65 and 4.27 microm, respectively. However, the mean encapsulation rate determined of Type A (13 +/- 2%) was found lower than Type B liposome (44 +/- 3%). The amounts of intracellular enrofloxacin concentrations were determined by high performance liquid chromatography. Type B LEE accumulated significantly higher level into monocytes when compared to free drug or Type A liposome. This study showed that Type B LEE markedly concentrated within monocytes and may improve the antibacterial efficacy of the antibiotic.

Peritoneal, systemic, and distant organ inflammatory responses are reduced by a laparoscopic approach and carbon dioxide versus air

BACKGROUND

Advantages of laparoscopic surgery have, among other factors, been attributed to a shorter length of abdominal incision and the use of CO2 versus air. An analysis of these factors taking pressure-induced alterations into account is lacking. The objective of the study was to determine the impact of laparoscopy and laparotomy with exposure to CO2 and room air under a similar pressure on local, systemic, and distant organ immune responses.

METHODS

Twenty piglets were randomized into four groups: CO2 laparoscopy, air laparoscopy, CO2 laparotomy, and air laparotomy. Laparotomy was performed in a sterile balloon pressurized similar to laparoscopy. Peritoneal interleukin-1, interleukin-6, tumor necrosis factor-a, and counts of polymorphnuclear cells (PMNs), and macrophages (MFs) were determined in abdominal lavage fluids at 0, 2, and 48 h. Macrophages were assessed for reactive oxygen species (ROS) production. Systemic responses were gauged by white blood cell count (WBC) and cytokines. Alveolar lavage was performed at 48 h to determine cytokine levels, cell counts, and MF ROS production. Blood, lavage fluids, and mesenteric lymph nodes were tested for bacterial translocation.

RESULTS

Regarding the peritoneal response, laparotomy versus laparoscopy when performed with CO2 significantly increased PMN and decreased the percentage of macrophages (%MF) up to 48 h. There was a significant increase in interleukin-6, and there was a fourfold increase in MF ROS production. Similar differences between the procedures were found with exposure to air. The use of air versus CO2 in laparoscopy, but not in laparotomy, resulted in an increase of peritoneal PMN and a decrease of the %MF up to 48 h. Air increased the local interleukin-6 release in both procedures and increased MF ROS production fourfold. Regarding the systemic response, laparotomy produced a significant increase in WBC, which was significantly more pronounced with exposure to air. No alteration of other systemic cytokines was seen. Regarding the pulmonary response, the number of MFs and MF ROS production were significantly increased after air versus CO2 laparoscopy. There were no such differences between the laparotomy groups. Regarding bacterial translocation, no bacteria were cultured from peritoneal fluids, lymph nodes, or blood.

CONCLUSIONS

Inflammatory responses were reduced by a laparoscopic approach and by exposure to CO2 versus air. Peritoneal responses were affected to a larger degree than systemic parameters. Laparotomy overruled the effects of CO2 on chemotaxis and distant organ injury but not on peritoneal cytokine release.