Effects of co-exposure to lead and manganese on learning and memory deficits.

Lead (Pb) and manganese (Mn) are common neurotoxins. However, individuals are subject to co-exposures in real life, and it is therefore important to study these metals in combination. Weaning Sprague-Dawley rats were given ad libitum access to drinking water solutions containing Pb (100 mg/L), Mn (2.5 mg/mL) or a mixture, and each treatment had its own minocycline (50 mg/(kg•day)) supplement group. The results showed a significant difference in spatial memory and induction levels of hippocampal long-term potentiation (LTP) in all exposure groups when compared with controls. The combined-exposure group exhibited the most pronounced effect when compared with each of the single-metal exposure groups. Microglia displayed activation at day 3 after exposure alone or in combination, while astrocytes showed activation at day 5, accompanied by decreased expression levels of GLAST, GLT-1, and GS. Furthermore, the levels of glutamate in the synaptic cleft increased significantly. When microglial activation was inhibited by minocycline, the activation of astrocytes and the expression of GLAST, GLT-1, and GS were both reversed. In addition, upon minocycline treatment, hippocampal LTP impairment and cognitive injury were significantly alleviated in each of the exposure groups. These results suggest that combined exposure to Pb and Mn can cause greater effects on cognition and synaptic plasticity when compared to single-metal exposure groups. The reason may involve abnormal activation of microglia leading to excessive regulation of astrocytes, resulting in glutamate reuptake dysfunction in astrocytes and leading to perturbed cognition and synaptic plasticity.

Altered Gut Microbiota and Its Metabolites in Hypertension of Developmental Origins: Exploring Differences between Fructose and Antibiotics Exposure.

Gut microbiota-derived metabolites, in particular short chain fatty acids (SCFAs) and their receptors, are linked to hypertension. Fructose and antibiotics are commonly used worldwide, and they have a negative impact on the gut microbiota. Our previous study revealed that maternal high-fructose (HF) diet-induced hypertension in adult offspring is relevant to altered gut microbiome and its metabolites. We, therefore, intended to examine whether minocycline administration during pregnancy and lactation may further affect blood pressure (BP) programmed by maternal HF intake via mediating gut microbiota and SCFAs. Pregnant Sprague-Dawley rats received a normal diet or diet containing 60% fructose throughout pregnancy and lactation periods. Additionally, pregnant dams received minocycline (50 mg/kg/day) via oral gavage or a vehicle during pregnancy and lactation periods. Four groups of male offspring were studied (n = 8 per group): normal diet (ND), high-fructose diet (HF), normal diet + minocycline (NDM), and HF + minocycline (HFM). Male offspring were killed at 12 weeks of age. We observed that the HF diet and minocycline administration, both individually and together, causes the elevation of BP in adult male offspring, while there is no synergistic effect between them. Four groups displayed distinct enterotypes. Minocycline treatment leads to an increase in the F/B ratio, but decreased abundance of genera Lactobacillus, Ruminococcus, and Odoribacter. Additionally, minocycline treatment decreases plasma acetic acid and butyric acid levels. Hypertension programmed by maternal HF diet plus minocycline exposure is related to the increased expression of several SCFA receptors. Moreover, minocycline- and HF-induced hypertension, individually or together, is associated with the aberrant activation of the renin-angiotensin system (RAS). Conclusively, our results provide a new insight into the support of gut microbiota and its metabolite SCAFs in the developmental programming of hypertension and cast new light on the role of RAS in this process, which will help prevent hypertension programmed by maternal high-fructose and antibiotic exposure.

Microglial deletion and inhibition alleviate behavior of post-traumatic stress disorder in mice.

BACKGROUND: Alteration of immune status in the central nervous system (CNS) has been implicated in the development of post-traumatic stress disorder (PTSD). However, the nature of overall changes in brain immunocyte landscape in PTSD condition remains unclear. METHODS: We constructed a mouse PTSD model by electric foot-shocks followed by contextual reminders and verified the PTSD-related symptoms by behavior test (including contextual freezing test, open-field test, and elevated plus maze test). We examined the immunocyte panorama in the brains of the naïve or PTSD mice by using single-cell mass cytometry. Microglia number and morphological changes in the hippocampus, prefrontal cortex, and amygdala were analyzed by histopathological methods. The gene expression changes of those microglia were detected by quantitative real-time PCR. Genetic/pharmacological depletion of microglia or minocycline treatment before foot-shocks exposure was performed to study the role of microglia in PTSD development and progress. RESULTS: We found microglia are the major brain immune cells that respond to PTSD. The number of microglia and ratio of microglia to immunocytes was significantly increased on the fifth day of foot-shock exposure. Furthermore, morphological analysis and gene expression profiling revealed temporal patterns of microglial activation in the hippocampus of the PTSD brains. Importantly, we found that genetic/pharmacological depletion of microglia or minocycline treatment before foot-shock exposure alleviated PTSD-associated anxiety and contextual fear. CONCLUSION: Our results demonstrated a critical role for microglial activation in PTSD development and a potential therapeutic strategy for the clinical treatment of PTSD in the form of microglial inhibition.

Genotoxic effect of non-lethal concentrations of minocycline in human glial cell culture.

Minocycline has been proposed as a neuroprotective agent with pleiotropic effects on several experimental models of neurodegenerative diseases, including microglial inhibition. However, although most studies have focused on the central actions of minocycline in affecting microglial functions, other central nervous system (CNS) cell types may also be affected by this drug toxicity. Hence, considering that glial cells play a pivotal role on CNS physiology and are the main responsible for neuronal integrity, a comprehensive investigation on the effects of minocycline treatment on human glial cells is mandatory before translational studies to afford neuroprotection in humans. Therefore, we explored the cytotoxic and genotoxic effects of minocycline at different concentrations in glial cells using an in vitro model. To achieve this, U87 glial cell were exposed to 10-50 µg/mL for 24 h. After exposure, cell viability, general metabolic status and genotoxic assays were performed. No changes were observed in cell viability, however, the general metabolic status decreased over 20 µg/mL. In addition, although no chromossome aberrations were observed, evidences of genotoxicity, such as increase on micronucleus, buds and bridges, were observed from 10 µg/mL. These results suggest that minocycline may induce genotoxic effects even at concentrations considered previously safe and should be used with caution in translational studies.

Minocycline induces apoptosis of photoreceptor cells by regulating ER stress.

Our previous work reported that minocycline induced inhibition of microglial activation aggravated visual injury in an oxygen induced retinopathy animal model. We hypothesized that minocycline might have aggravated injury to the photoreceptor. Some patients who use minocycline to treat acne complain of visual impairment; however, no studies have addressed minocycline toxicity to photoreceptors. Here, we identified mechanistic effect of minocycline on photoreceptor apoptosis. The results of Cell Counting Kit-8 and Ki67 staining demonstrated that minocycline inhibited the proliferation of 661W cells, and flow cytometry and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) demonstrated that minocycline promoted cell apoptosis. Additionally, minocycline administration activated signaling associated with endoplasmic reticulum stress, the pancreatic ER kinase-like ER kinase (PERK)-eukaryotic translation initiation factor 2α (eIF2α)-CCAAT/enhancer-binding protein homologous protein (CHOP) cascade, which represented the key mechanism underlying the initiation of apoptosis. Moreover, we observed downregulated nuclear factor erythroid 2-related factor 2 (Nrf2) after administration of minocycline for 12 h (12 hours) and Nrf2 transferred from nuclear to cytoplasm after 6 h, indicating that Nrf2 in nuclear may alleviated the pro-apoptotic effect of minocycline on photoreceptor cells. Upregulating Nrf2 inhibited apoptosis in minocycline treated 661W cells. These represent the first data demonstrating minocycline toxicity to photoreceptors via its pro-apoptotic effects through the regulation of ER stress pathways.

Comparative Evaluation of the Cytotoxic and Angiogenic Effects of Minocycline and Clindamycin: An In Vitro Study.

INTRODUCTION: This study aimed to compare the cytocompatibility and angiogenic potential of 2 antibiotics (clindamycin [CLIN] and minocycline [MINO]) at distinct concentrations on dental pulp stem cells (DPSCs) and human umbilical vein endothelial cells (HUVECs). METHODS: DPSCs and HUVECs were exposed to cell culture media modified with CLIN or MINO at concentrations ranging from 30 µg/mL-1000 µg/mL. Cell toxicity and proliferation were investigated using the lactate dehydrogenase and tetrazolium reduction assays, respectively. A capillarylike tube formation in vitro assay was conducted to determine the angiogenic potential associated with each antibiotic. Additionally, selected morphometric angiogenesis parameters were determined using dedicated software (WimTube; Onimagin Technologies SCA, Córdoba, Spain). All statistical analyses were performed using 1-way analysis of variance and the Tukey post hoc test (α= .05). RESULTS: The collected data showed that compared with the control (cell culture media, alpha-minimum essential medium Eagle) increasing the antibiotic concentration significantly decreased cell viability and proliferation of both DPSCs and HUVECs. In terms of angiogenic potential, when tested at 30 µg/mL and 50 µg/mL, CLIN significantly amplified tube formation when compared with MINO with angiogenesis parameters (ie, tube length and tube number) similar to the effect promoted by exogenous vascular endothelial growth factor (50 ng/mL). CONCLUSIONS: CLIN was less cytotoxic when compared with MINO at higher concentrations. Of note, CLIN did not hinder the proangiogenic activity induced by vascular endothelial growth factor to the same extent as MINO, suggesting that the replacement of MINO by CLIN might translate into positive implications in the overall regenerative outcome.

Preparation and characteristics of thermoresponsive gel of minocycline hydrochloride and evaluation of its effect on experimental periodontitis models.

In this study, a thermoresponsive gel for minocycline (MCL) with chitosan/ß-glycerophosphate (C/ß-GP) was formulated and its characterization, in vitro release, stability, toxicity and pharmacodynamics were investigated. The formulation containing MCL was prepared by pouring the chitosan solution directly onto the sterilized drug powder and stirring before mixing with the ß-glycerophosphate (ß-GP) solution. The final preparations contained 0.5% (w/v) chitosan, 1.8% (w/v) ß-GP and 2% (w/v) MCL. The drug content of prepared gels was in the range of 92-99%, and the pH value of the optimized formulation was found to be 5.6-6.2. The gelation temperature of the prepared C/ß-GP thermogelling solutions was 37 °C. Color, consistency, pH, viscosity and drug content of the in situ gels were found to be consistent, and no signs of separation and deterioration were observed over a period of 90 d. In vivo studies showed that rats' liver and kidney tissue sections were normal, with no structural damage. The constituents of the in situ gels formulation had a well-sustained release efficacy on the animal model of periodontitis.

Antagonism of PACAP or microglia function worsens the cardiovascular consequences of kainic-acid-induced seizures in rats.

Seizures are accompanied by cardiovascular changes that are a major cause of sudden unexpected death in epilepsy (SUDEP). Seizures activate inflammatory responses in the cardiovascular nuclei of the medulla oblongata and increase neuronal excitability. Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide with autocrine and paracrine neuroprotective properties. Microglia are key players in inflammatory responses in the CNS. We sought to determine whether PACAP and microglia mitigate the adverse effects of seizure on cardiovascular function in a rat model of temporal lobe epilepsy. Kainic acid (KA)-induced seizures increased splanchnic sympathetic nerve activity by 97%, accompanied by increase in heart rate (HR) but not blood pressure (BP). Intrathecal infusion of the PACAP antagonist PACAP(6-38) or the microglia antagonists minocycline and doxycycline augmented sympathetic responses to KA-induced seizures. PACAP(6-38) caused a 161% increase, whereas minocycline and doxycycline caused a 225% and 215% increase, respectively. In intrathecal PACAP-antagonist-treated rats, both BP and HR increased, whereas after treatment with microglial antagonists, only BP was significantly increased compared with control. Our findings support the idea that PACAP and its action on microglia at the level of the spinal cord elicit cardioprotective effects during seizure. However, intrathecal PACAP did not show additive effects, suggesting that the agonist effect was at maximum. The protective effect of microglia may occur by adoption of an M2 phenotype and expression of factors such as TGF-ß and IL-10 that promote neuronal quiescence. In summary, therapeutic interventions targeting PACAP and microglia could be a promising strategy for preventing SUDEP.

The direct cytotoxic effects of medicaments used in endodontic regeneration on human dental pulp cells.

AIM: The purpose of this in vitro study was to evaluate the effects of intracanal medicaments commonly used in endodontic regeneration on the survival of human dental pulp cells (DPCs). METHODS: DPCs were cultured and exposed to either no medicament treatment or low concentrations (0.3-5 mg ml(-1) ) of calcium hydroxide [Ca(OH)2 ], triple antibiotic paste (TAP), or double antibiotic paste (DAP) for 3 days. After that, toxicity to the DPCs was determined by lactate dehydrogenase activity assays (LDH) and cell proliferation was measured by colorimetric assays (WST-1). Two-way anova followed by Fisher's protected least significant differences was used for statistical analyses (α = 0.05). RESULTS: The group-by-concentration interactions were significant for the LDH and WST-1 assays (P < 0.0001). For the LDH assays, only the highest tested concentration (5 mg ml(-1) ) of Ca(OH)2 and TAP caused significant toxicity to the DPCs compared with the untreated control, while four tested concentrations of DAP (0.5, 1, 2.5, and 5 mg ml(-1) ) caused significant toxicity to the DPCs compared with the untreated control. For the WST-1 assays, the highest concentrations that did not negatively affect the proliferation rate of DAP, TAP and Ca(OH)2 were 0.3, 2, and 2.5 mg ml(-1) , respectively. CONCLUSION: The low concentrations of intracanal medicaments tested in this study were not cytotoxic in cultured cells. However, these concentrations are much lower than the concentrations that have been advocated in endodontic regeneration. Furthermore, the negative effects of TAP on DPCs were detected at lower concentrations by using the WST-1 assays than by measuring the LDH release.

Prolonged minocycline treatment impairs motor neuronal survival and glial function in organotypic rat spinal cord cultures.

BACKGROUND: Minocycline, a second-generation tetracycline antibiotic, exhibits anti-inflammatory and neuroprotective effects in various experimental models of neurological diseases, such as stroke, Alzheimer's disease, amyotrophic lateral sclerosis and spinal cord injury. However, conflicting results have prompted a debate regarding the beneficial effects of minocycline. METHODS: In this study, we analyzed minocycline treatment in organotypic spinal cord cultures of neonatal rats as a model of motor neuron survival and regeneration after injury. Minocycline was administered in 2 different concentrations (10 and 100 µM) at various time points in culture and fixed after 1 week. RESULTS: Prolonged minocycline administration decreased the survival of motor neurons in the organotypic cultures. This effect was strongly enhanced with higher concentrations of minocycline. High concentrations of minocycline reduced the number of DAPI-positive cell nuclei in organotypic cultures and simultaneously inhibited microglial activation. Astrocytes, which covered the surface of the control organotypic cultures, revealed a peripheral distribution after early minocycline treatment. Thus, we further analyzed the effects of 100 µM minocycline on the viability and migration ability of dispersed primary glial cell cultures. We found that minocycline reduced cell viability, delayed wound closure in a scratch migration assay and increased connexin 43 protein levels in these cultures. CONCLUSIONS: The administration of high doses of minocycline was deleterious for motor neuron survival. In addition, it inhibited microglial activation and impaired glial viability and migration. These data suggest that especially high doses of minocycline might have undesired affects in treatment of spinal cord injury. Further experiments are required to determine the conditions for the safe clinical administration of minocycline in spinal cord injured patients.

Cytotoxic effects and antibacterial efficacy of a 3-antibiotic combination: an in vitro study.

INTRODUCTION: A 3-antibiotic combination (3Mix) is widely used in endodontics for root canal disinfection, particularly in pulp revascularization procedures. However, the cytotoxicity of 3Mix has not been evaluated. The purpose of this study was to determine the cytotoxicity and antibacterial efficacy of 3Mix and each single antibiotic component of 3Mix. METHODS: For the cytotoxicity test, human dental pulp cells and apical papilla cells were exposed to either 3Mix or to each single antibiotic component of 3Mix using concentrations of 0.024, 0.097, 0.39, 1.56, 6.25, and 25.00 µg/mL for 1, 3, 5, and 7 days. Cell viability was determined using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. For the antibacterial test, 25.00 µg/mL and 0.39 µg/mL 3Mix or single antibiotic were tested on bacteria isolated from necrotic teeth by measuring bacterial recovery on blood agar. RESULTS: The 0.024-µg/mL concentration of all experimental groups generated the highest dental pulp cell or apical pulp cell viability at all time periods. On day 7, 0.39 µg/mL 3Mix produced more than 90% cell viability; 25.00 µg/mL 3Mix completely eliminated isolated bacteria, whereas 0.39 µg/mL was unable to eradicate all bacteria. However, the overall bacterial reduction was significantly different compared with the control group (P < .01). CONCLUSIONS: All drugs except metronidazole induced cytotoxicity on cultured cells. 3Mix generated higher cytotoxicity compared with a single drug. The cytotoxicity increased in a concentration- and time-dependent manner; 0.39 µg/mL 3Mix had less cytotoxicity and was able to significantly reduce bacteria isolated from necrotic teeth.

Effects of minocycline and its degradation products on the growth of Microcystis aeruginosa.

This work aimed to investigate the influence of Microcystis aeruginosa on the rate of minocycline (MNC) removal (abiotic degradation, physical binding or chemical transformation by cells) and the toxicity of MNC and its degradation products to the cyanobacterium. Most of the work was carried out in culture media in the presence or in the absence of M. aeruginosa. The rate of the MNC abiotic degradation in culture media strongly decreased with the increase of the MNC initial concentration. The exudates did not influence the rate of MNC degradation in the media. For concentrations ≥0.48 µM, the rate of the MNC removal from the media was faster in the presence of M. aeruginosa. Biotic MNC removal occurs by both physical binding by the cells (10%) and chemical transformations. EC(50) and EC(20) for MNC on the growth of M. aeruginosa were 0.92 and 0.13 µM, respectively. Interestingly, MNC degradation products might promote M. aeruginosa growth.

Chemotactic and cytotoxic effects of minocycline on human retinal pigment epithelial cells.

PURPOSE: To reveal the effects of minocycline, an anti-inflammatory and neuroprotective agent, on the viability and physiological properties of retinal pigment epithelial (RPE) cells and to compare the effects with those of triamcinolone acetonide. METHODS: The proliferation of human RPE cells in vitro was investigated with a bromodeoxyuridine immunoassay; chemotaxis was examined with a Boyden chamber assay. Cell viability was determined by trypan blue exclusion. The gene expression of growth factors and MMP-9 was determined with real-time RT-PCR, and the secretion of VEGF was examined with ELISA. The phosphorylation of p38 MAPK and ERK1/2 proteins was determined with Western blot analysis. RESULTS: Minocycline at low concentrations (50 nM-20 microM) stimulated chemotaxis and decreased the proliferation of RPE cells. Minocycline at high concentrations (above 5 microM) decreased the viability of RPE cells through the induction of cell necrosis. The chemotactic effect of minocycline was mediated by the stimulation of autocrine PDGF signaling and the activation of p38 MAPK. Minocycline promoted the expression of PDGF-B, HGF, VEGF, and MMP-9 and increased the amounts of phosphorylated p38 and ERK1/2 proteins in RPE cells. Triamcinolone reduced PDGF-evoked chemotaxis and VEGF expression and secretion and had no significant effects on cell viability and proliferation. Triamcinolone did not reverse the effects of minocycline on cell proliferation, chemotaxis, or viability or the expression of VEGF. CONCLUSIONS: Low-dose minocycline induces the activation of RPE cells, as indicated by the activation of p38 and ERK1/2 and by enhanced chemotaxis mediated by autocrine PDGF signaling. High-dose minocycline induces RPE cell degeneration.

Fewer adverse effects with doxycycline than with minocycline.

(1) In mid-2008 the French National Pharmacovigilance Committee examined spontaneous reports of adverse effects observed during tetracycline therapy; (2) When sales figures are taken into account, reports were more frequent with minocycline than with doxycycline. The proportion of severe adverse effects was also higher with minocycline than with doxycycline; (3) Life-threatening hypersensitivity reactions and autoimmune adverse effects were more frequent with minocycline than with doxycycline; (4) In practice, minocycline has a less favourable risk-benefit balance than doxycycline, particularly in the treatment of acne.

Brain and plasma riluzole pharmacokinetics: effect of minocycline combination.

PURPOSE: amyotrophic lateral sclerosis is a fatal neurodegenerative disease characterized by the loss of motorneurons. The only drug approved is riluzole. Minocycline is an antibiotic with numerous neuroprotective properties. riluzole and minocycline were given to an animal model of ALS and had beneficial effect on the disease. The combination was then tested in humans in phase II and phase III studies with less beneficial effects and a faster decline of the disease in the group treated with minocycline. In a previous study, we showed that riluzole is transported out of the brain by the P-glycoprotein at the blood-brain barrier level. METHODS: in this work, we studied in CF1 mice, the plasmatic and cerebral pharmacokinetics of riluzole combined or not with minocycline. RESULTS: our results showed that the kinetics of riluzole are not linear with dose, but that cerebral AUC0-infinity increase proportionally with plasmatic AUC0-infinity. At the dose of 10 mg/kg, the cerebral AUC0-infinity /plasmatic AUC0-infinity ratio was 4.6 in mdr1a (-/-) mice and 2.4 in mdr1a (+/+) mice. The combination of minocycline (170 mg/kg) and riluzole (10 mg/kg) induced a 2 fold increase in the cerebral AUC0-infinity of riluzole and induced a neuromuscular toxicity in mice. This effect of minocycline was not found at low concentration (10 mg/kg of minocycline). CONCLUSIONS: if our results are confirmed in humans, riluzole cerebral concentrations could be predicted by plasmatic concentrations. Furthermore, the combination of high doses of minocycline with riluzole could induce neurological toxicity that lead to deceiving results in ALS clinical studies.

The effect of doxycycline hyclate, chlorhexidine gluconate, and minocycline hydrochloride on osteoblastic proliferation and differentiation in vitro.

BACKGROUND: The purpose of this study was to determine the effect of the active substance of three types of local delivery systems, doxycycline hyclate 10% (DOXY), chlorhexidine gluconate, 2.5 mg (CHX), and minocycline hydrochloride, 1 mg (MINO), on osteoblastic cell proliferation and differentiation. METHODS: There were four groups: control osteoblastic cells (OB) alone, OB + DOXY, OB + CHX, and OB + MINO. Trypan blue and MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assays were used to test osteoblastic cell viability. Cell differentiation was tested by measuring alkaline phosphatase levels. Osteoblast morphology was investigated by light and scanning electron microscopy. RESULTS: At a concentration of 0.5 mg/ml, the Trypan blue test showed that DOXY, MINO, and CHX had significant toxicity effects on osteoblast cells compared to the control group, with a mean cell viability of 84%, 74%, and 51%, respectively (P <0.05). The MTT test showed that the control and DOXY groups were statistically significantly different (P <0.05) compared to CHX and MINO groups. The DOXY group showed a significantly higher alkaline phosphatase activity ( approximately 56%) than the control and MINO groups, and it was nearly 178% higher than the CHX group (P <0.05). The morphology of the osteoblasts seemed to be slightly altered when they were incubated with DOXY; however, with MINO, they appeared rounded with minimal attachment. In the CHX group, the osteoblasts assumed a shape of a very thin filopodia with a volcano-like nucleus. CONCLUSIONS: At a concentration of 0.5 mg/ml, CHX and, to a lesser extent, MINO had a cytotoxic effect on osteoblast proliferation in vitro. However, DOXY seemed to enhance maturation and differentiation rather than proliferation. In addition to DOXY's beneficial effect as an adjunctive therapy to mechanical debridement in the treatment of periodontal disease, it may have an effect on periodontal regeneration.

Tigecycline susceptibility report from an Indian tertiary care hospital.

BACKGROUND & OBJECTIVE: Treatment of serious life threatening infections due to multi-drug resistant pathogens presents a difficult challenge due to the limited therapeutic options. Therefore, we studied the in vitro susceptibility of tigecycline, a new glycylcycline with promising broad spectrum of activity against Gram positive and Gram negative bacteria at a tertiary care hospital in north India. METHODS: A total of 75 multi-drug resistant isolates of methicillin resistant Staphylococcus aureus (21), vancomycin resistant enterococci (14), vancomycin resistant Streptococcus spp. (3), extended spectrum beta lactamase producing Gram negative bacteria (11) and multi-resistant Acinetobacter spp. (26) were tested for tigecycline susceptibility by the E-test and disc diffusion methods. An additional 83 multi-resistant Gram negative clinical isolates were screened by disc diffusion method alone. RESULTS: All the isolates of MRSA, VRE, vancomycin resistant Streptococcus spp. and ESBL producing enteric bacteria were sensitive to tigecycline by the E-test and disc diffusion methods. However, only 42 per cent of Acinetobacter spp. were found to be sensitive to tigecycline by the E-test method. INTERPRETATION & CONCLUSION: In conclusion, tigecycline was found to be highly effective against Gram-positive bacteria and Gram-negative members of Enterobacteriaceae, but a high prevalence of resistance in members of Acinetobacter spp. is worrisome.

Deleterious effects of minocycline after in vivo target deprivation of thalamocortical neurons in the immature, metallothionein-deficient mouse brain.

Compared with adults, immature metallothionein I and II knockout (MT(-/-)) mice incur greater neuronal loss and a more rapid rate of microglia accumulation after target deprivation-induced injury. Because minocycline has been proposed to inhibit microglial activation and associated production of neuroinflammatory factors, we investigated its ability to promote neuronal survival in the immature, metallothionein-deficient brain. After ablation of the visual cortex, 10-day-old MT(-/-) mice were treated with minocycline or saline and killed 24 or 48 hr after injury. By means of stereological methods, the number of microglia and neurons were estimated in the ipsilateral dorsal lateral geniculate nucleus (dLGN) by an investigator blinded to the treatment. No effect on neuronal survival was observed at 24 hr, but 48 hr after injury, an unanticipated but significant minocycline-mediated increase in neuronal loss was detected. Further, while failing to inhibit microglial accumulation, minocycline treatment increased the proportion of amoeboid microglia in the ipsilateral dLGN. To understand the molecular mechanisms underlying this neurotoxic response, we identified minocycline-mediated changes in the expression of three potentially proapoptotic/inflammatory genes: growth arrest- and DNA damage-inducible gene 45gamma (GADD45gamma); interferon-inducible protein 1 (IFI1), and cytokine-induced growth factor. We also observed increased mitogen-activated protein kinase p38 phosphorylation with minocycline treatment. Although minocycline inhibited calpain activity at 12 hr after injury, this effect was not sustained at 24 hr. Together, these results help to explain how minocycline has a deleterious effect on neuronal survival in this injury model.