Trends of central line-associated bloodstream infections in the intensive care unit in the Kingdom of Bahrain: Four years’ experience

BACKGROUND

The central venous line is an essential component in monitoring and managing critically ill patients. However, it poses patients with increased risks of severe infections with a higher probability of morbidity and mortality.

AIM

To define the trends of the rates of central line-associated bloodstream infections (CLABSI) over four years, its predicted risk factors, aetiology, and the antimicrobial susceptibility of the isolated pathogens.

METHODS

The study was a prospective case-control study, performed according to the guidelines of the Center for Disease Control surveillance methodology for CLABSI in patients admitted to the adult intensive care unit (ICU) and auditing the implementation of its prevention bundle.

RESULTS

Thirty-four CLABSI identified over the study period, giving an average CLABSI rate of 3.2/1000 central line days. The infection's time trend displayed significant reductions over time concomitantly with the CLABSI prevention bundle's reinforcement from 4.7/1000 central line days at the beginning of 2016 to 1.4/1000 central line days by 2018. The most frequently identified pathogens causing CLABSI in our ICU were gram-negative organisms (59%). The most common offending organisms were Acinetobacter, Enterococcus, and Staphylococcus epidermidis, each of them accounted for 5 cases (15%). Multidrug-resistant organisms contributed to 56% of CLABSI. Its rate was higher when using femoral access and longer hospitalisation duration, especially in the ICU. Insertion of the central line in the non-ICU setting was another identified risk factor.

CONCLUSION

Implementing the prevention bundles reduced CLABSI significantly in our ICU. Implementing the CLABSI prevention bundle is crucial to maintain a substantial reduction in the CLABSI rate in the ICU setting.

ET-1- and NO-mediated signal transduction pathway in human brain capillary endothelial cells

Previous studies have demonstrated that functional interaction between endothelin (ET)-1 and nitric oxide (NO) involves changes in Ca(2+) mobilization and cytoskeleton in human brain microvascular endothelial cells. The focus of this investigation was to examine the possible existence of analogous interplay between these vasoactive substances and elucidate their signal transduction pathways in human brain capillary endothelial cells. The results indicate that ET-1-stimulated Ca(2+) mobilization in these cells is dose-dependently inhibited by NOR-1 (an NO donor). This inhibition was prevented by ODQ (an inhibitor of guanylyl cyclase) or Rp-8-CPT-cGMPS (an inhibitor of protein kinase G). Treatment of endothelial cells with 8-bromo-cGMP reduced ET-1-induced Ca(2+) mobilization in a manner similar to that observed with NOR-1 treatment. In addition, NOR-1 or cGMP reduced Ca(2+) mobilization induced by mastoparan (an activator of G protein), inositol 1,4,5-trisphosphate, or thapsigargin (an inhibitor of Ca(2+)-ATPase). Interestingly, alterations in endothelial cytoskeleton (actin and vimentin) were associated with these effects. The data indicate for the first time that the cGMP-dependent protein kinase colocalizes with actin. These changes were accompanied by altered levels of phosphorylated vasodilator-stimulated phosphoprotein, which were elevated in endothelial cells incubated with NOR-1 and significantly reduced by ODQ or Rp-8-CPT-cGMPS. The findings indicate a potential mechanism by which the functional interrelationship between ET-1 and NO plays a role in regulating capillary tone, microcirculation, and blood-brain barrier function.

Endothelin-1 and nitric oxide affect human cerebromicrovascular endothelial responses and signal transduction

Endothelium plays a central role in regulating the vascular tone, blood flow and blood brain barrier (BBB) permeability. The experiments presented here examine the mechanisms by which nitric oxide (NO) and endothelin-1 (ET-1) may be involved in these processes. The findings indicate that ET-1-stimulated [Ca2+]i accumulation occurs through activation of ETA receptor. The capacity of NO to affect this response was indicated by results showing: 1) a two-fold increase in ET-1-stimulated [Ca2+]i by L-NAME, the inhibitor of nitric oxide synthase, and 2) a dose-dependent decrease in [Ca2+]i accumulation by pretreatment with Nor-1 (NO donor). Abrogation of this Nor-1 effect by ODQ (an inhibitor of guanylyl cyclase) or Rp-8-pCPT-cGMPS (an inhibitor of protein kinase G) and inhibition of ET-1 stimulated intracellular Ca2+ accumulation by 8-bromo-cGMP (a permeable, analog of cGMP) substantiate the involvement of interplay between ET-1 and NO in [Ca2+]i accumulation in HBMEC. ET-1 treatment also increased thickness of F-actin cytoskeletal filaments in HBMEC. This effect was attenuated by pretreatment with NO; NO also rarefied F-actin filaments in control cultures. The findings support a linkage between NO and ET-1 in regulating microvascular tone, microcirculation and BBB permeability and indicate a role for cGMP/cGMP protein kinase system and cytoskeletal changes in responses of HBMEC.

Human brain capillary endothelium: 2-arachidonoglycerol (endocannabinoid) interacts with endothelin-1

In brain, the regulatory mechanism of the endothelial reactivity to nitric oxide and endothelin-1 may involve Ca(2+), cytoskeleton, and vasodilator-stimulated phosphoprotein changes mediated by the cGMP/cGMP kinase system.(1) Endothelium of human brain capillaries or microvessels is used to examine the interplay of endothelin-1 with the putative vasorelaxant 2-arachidonoyl glycerol, an endogenous cannabimimetic derivative of arachidonic acid. This study demonstrates that 2-arachidonoyl glycerol counteracts Ca(2+) mobilization and cytoskeleton rearrangement induced by endothelin-1. This event is independent of nitric oxide, cyclooxygenase, and lipoxygenase and is mediated in part by cannabimimetic CB1 receptor, G protein, phosphoinositol signal transduction pathway, and Ca(2+)-activated K(+) channels. The induced rearrangements of cellular cytoskeleton (actin or vimentin) are partly prevented by inhibition of protein kinase C or high levels of potassium chloride. The 2-arachidonoyl glycerol-induced phosphorylation of vasodilator-stimulated phosphoprotein is mediated by cAMP. These findings suggest that 2-arachidonoyl glycerol may contribute to the regulation of cerebral capillary and microvascular function.

TNF-alpha pretreatment prevents subsequent activation of cultured brain cells with TNF-alpha and hypoxia via ceramide

We have developed a cellular model in which cultured astrocytes and brain capillary endothelial cells preconditioned with tumor necrosis factor-alpha (TNF-alpha) fail to upregulate intercellular adhesion molecule-1 (ICAM-1) protein (80% inhibition) and mRNA (30% inhibition) when challenged with TNF-alpha or exposed to hypoxia. Inasmuch as ceramide is known to mediate some of the effects of TNF-alpha, its levels were measured at various times after the TNF-alpha preconditioning. We present evidence for the first time that, in normal brain cells, TNF-alpha pretreatment causes a biphasic increase of ceramide levels: an early peak at 15-20 min, when ceramide levels increased 1.9-fold in astrocytes and 2.7-fold in rat brain capillary endothelial cells, and a delayed 2- to 3-fold ceramide increase that occurs 18-24 h after addition of TNF-alpha. The following findings indicate that the delayed ceramide accumulation results in cell unresponsiveness to TNF-alpha: 1) coincident timing of the ceramide peak and the tolerance period, 2) mimicking of preconditioning by addition of exogenous ceramide, and 3) attenuation of preconditioning by fumonisin B1, an inhibitor of ceramide synthesis. In contrast to observations in transformed cell lines, the delayed ceramide increase was transient and did not induce apoptosis in brain cells.

Nitric oxide modulates endothelin 1-induced Ca2+ mobilization and cytoskeletal F-actin filaments in human cerebromicrovascular endothelial cells

A functional interrelation between nitric oxide (NO), the endothelial-derived vasodilating factor, and endothelin 1 (ET-1), the potent vasoconstrictive peptide, was investigated in microvascular endothelium of human brain. Nor-1 dose-dependently decreased the ET-1-stimulated mobilization of Ca2+. This response was mimicked with cGMP and abrogated by inhibitors of guanylyl cyclase or cGMP-dependent protein kinase G. These findings indicate that NO and ET-1 interactions involved in modulation of intracellular Ca2+ are mediated by cGMP/protein kinase G. In addition, Nor-1-mediated effects were associated with rearrangements of cytoskeleton F-actin filaments. The results suggest mechanisms by which NO-ET-1 interactions may contribute to regulation of microvascular function.

Stimulation of tyrosine phosphorylation of a brain protein by hibernation

Mammalian hibernation is a state of natural tolerance to severely decreased brain blood flow. As protein tyrosine phosphorylation is believed to be involved in the development of resistance to potentially cell-damaging insults, we used immunoblotting for the phosphotyrosine moiety to analyze extracts from various tissues of hibernating and nonhibernating ground squirrels. A single, hibernation-specific phosphoprotein was detected in the brain, but not in any other tissue tested. This protein, designated pp98 to reflect its apparent molecular weight, is distributed throughout the brain, and is associated with the cellular membrane fraction. The presence of the protein is tightly linked to the hibernation state; it is not present in contemporaneously assayed animals that are exposed to the same cold temperature as the hibernators, is present for the duration of a hibernation bout (tested from 1 to 14 days), and disappears within 1 hour of arousal from hibernation. The close association of pp98 with the hibernation state, its presence in cellular membranes, and the known properties of membrane phosphotyrosine proteins suggest that it may transduce a signal for adaptation to the limited availability of oxygen and glucose and low cellular temperature that characterizes hibernation in the ground squirrel.

Mice lacking GFAP are hypersensitive to traumatic cerebrospinal injury

Glial fibrillary acidic protein (GFAP) is an intermediate filament protein expressed primarily in astrocytes. We have tested whether GFAP protects against mechanical stress by inducing percussive head injury in GFAP-null mice with a weight drop device. When mice were positioned on a foam bed which allowed head movement at impact, all 14 wild-type mice tested survived, but 12 of 15 GFAP-null mice died within a few minutes. The cause of death appeared to be upper cervical spinal cord injury resulting in respiratory arrest. When the foam bed was replaced by a firm support, both GFAP-null and wild-type mice survived. These results indicate that mice lacking GFAP are hypersensitive to cervical spinal cord injury caused by sudden acceleration of the head.

Influence of 17 beta-estradiol and progesterone on rat ocular lens

The effect of 17 beta-estradiol and progesterone on ocular lens in rats and untreated controls was studied. In the treated lenses, the activity of hexokinase and glucose-6-phosphate dehydrogenase remained unchanged. The activity of aldolase was increased in 18- and 20-month-old lenses as compared to controls. Aldose reductase activity was decreased at the age of 20 months (p < 0.001). Structural lens proteins studies by SDS polyacrylamide gel electrophoresis and immunodecoration with specific antibodies for crystallines alpha A + alpha B and beta + gamma suggest some protective effect in treated animals.