Diarreia associada a Shigella em crianças e sensibilidade a antimicrobianos / Diarrhea associated with Shigella in children and susceptibility to antimicrobials

OBJETIVO: Avaliar a distribuição e suscetibilidade a antimicrobianos de Shigella isolada de crianças com diarreia aguda e sem diarreia em Teresina (PI). MÉTODOS: Quatrocentas crianças com idade até 60 meses foram estudadas. Fezes foram coletadas de todos os pacientes entre janeiro de 2004 e agosto de 2007. Shigella foi identificada por métodos convencionais e antibiograma e pesquisa de β-lactamase de espectro ampliado (ESBL) foram realizados por difusão em ágar. RESULTADOS: Shigelose foi detectada apenas em crianças com diarreia aguda (26/250; 10,4%), especialmente naquelas entre 6 e 24 meses de idade e nos meses chuvosos. Shigella foi suscetível a ceftriaxona, ciprofloxacina e ácido nalidíxico. Mais da metade das amostras foram resistentes a sulfametoxazol-trimetoprim e ampicilina. ESBL não foi detectada. CONCLUSÕES: S. flexneri é comum em Teresina. A resistência a ampicilina e sulfametoxazol-trimetoprim é preocupante, pois estas drogas são amplamente utilizadas na prática e sulfametoxazol-trimetoprim ainda é recomendada para tratamento de crianças com suspeita de shigelose.

OBJECTIVE: To evaluate the distribution and susceptibility to antimicrobials of Shigella isolated from children with acute diarrhea and without diarrhea in Teresina, state of Piauí, Brazil. METHODS: Four hundred children aged up to 60 months were studied. Stools were collected from all the patients between January 2004 and August 2007. Shigella was identified by conventional methods and antibiogram and extended-spectrum β-lactamase (ESBL) were performed by agar diffusion. RESULTS: Shigellosis was only detected in children with acute diarrhea (26/250; 10.4%), especially in those aged from 6 to 24 months and in the rainy months. Shigella was susceptible to ceftriaxone, ciprofloxacin and nalidixic acid. More than half of the strains were resistant to sulphametoxazole-trimethoprim and ampicillin. ESBL was not detected. CONCLUSIONS: S. flexneri is common in Teresina. The resistance to ampicillin and sulphametoxazole-trimethoprim gives cause for concern, as these drugs are widely used in practice and sulphametoxazole-trimethoprim is also recommended for treating children suspected of having shigellosis.

Diarrhea associated with Shigella in children and susceptibility to antimicrobials.

OBJECTIVE: To evaluate the distribution and susceptibility to antimicrobials of Shigella isolated from children with acute diarrhea and without diarrhea in Teresina, state of Piauí, Brazil. METHODS: Four hundred children aged up to 60 months were studied. Stools were collected from all the patients between January 2004 and August 2007. Shigella was identified by conventional methods and antibiogram and extended-spectrum beta-lactamase (ESBL) were performed by agar diffusion. RESULTS: Shigellosis was only detected in children with acute diarrhea (26/250; 10.4%), especially in those aged from 6 to 24 months and in the rainy months. Shigella was susceptible to ceftriaxone, ciprofloxacin and nalidixic acid. More than half of the strains were resistant to sulphametoxazole-trimethoprim and ampicillin. ESBL was not detected. CONCLUSIONS: S. flexneri is common in Teresina. The resistance to ampicillin and sulphametoxazole-trimethoprim gives cause for concern, as these drugs are widely used in practice and sulphametoxazole-trimethoprim is also recommended for treating children suspected of having shigellosis.

Differentiation of engrafted multipotent neural progenitors towards replacement of missing granule neurons in meander tail cerebellum may help determine the locus of mutant gene action.

Previously we observed that stable clones of multipotent neural progenitor cells, initially isolated and propagated from the external granular layer of newborn wild-type mouse cerebellum, could participate appropriately in cerebellar development when reimplanted into the external granular layer of normal mice. Donor cells could reintegrate and differentiate into neurons (including granule cells) and/or glia consistent with their site of engraftment. These findings suggested that progenitors might be useful for cellular replacement in models of aberrant neural development or neurodegeneration. We tested this hypothesis by implanting clonally related multipotent progenitors into the external granular layer of newborn meander tail mice (gene symbol=mea). mea is an autosomal recessive mutation characterized principally by the failure of granule cells to develop in the cerebellar anterior lobe; the mechanism is unknown. We report that approximately 75% of progenitors transplanted into the granuloprival anterior lobe of neonatal mea mutants differentiated into granule cells, partially replacing or augmenting that largely absent neuronal population in the internal granular layer of the mature meander tail anterior lobe. (The ostensibly 'normal' meander tail posterior lobe also benefited from repletion of a more subtle granule cell deficiency.) Donor-derived neurons were well-integrated within the neuropil, suggesting that these progenitors' developmental programs for granule cell differentiation were unperturbed. These observations permitted several conclusions. (1) That exogenous progenitors could survive transplantation into affected regions of neonatal meander tail cerebellum and differentiate into the deficient cell type suggested that the microenvironment was not inimical to granule cell development. Rather it suggested that mea's deleterious action is intrinsic to the external granular layer cell. (Any cell-extrinsic actions--albeit unlikely--had to be restricted to readily circumventable prenatal events.) This study, therefore, offers a paradigm for using progenitors to help determine the site of action of other mutant genes or to test hypotheses regarding the pathophysiology underlying other anomalies. (2) In the regions most deficient in neurons, a neuronal phenotype was pursued in preference to other potential cell types, suggesting a 'push' of undifferentiated, multipotent progenitors towards compensation for granule cell dearth. These data suggested that progenitors with the potential for multiple fates might differentiate towards repletion of deficient cell types, a possible developmental mechanism with therapeutic implications. Neural progenitors (donor or endogenous) might enable cell replacement in some developmental or degenerative diseases--most obviously in cases where a defect is intrinsic to the diseased cell, but also, under certain circumstances, when extrinsic pathologic forces may exist.

Peripheral target reinnervation following orthotopic grafting of fetal allogeneic and xenogeneic dorsal root ganglia.

The sensory reinnervation of dermal papillae and epidermis of glabrous skin, interosseal Pacinian corpuscles, and muscle spindles of the soleus and extensor digitorum longus muscles has been examined 1, 3, and 8 months (allografts) or 3 and 5 weeks (xenografts) following orthotopic grafting of fetal allogeneic or xenogeneic (mouse) dorsal root ganglia (DRG) into ganglionectomized adult rats. Sensory axons in target tissues were identified immunohistochemically by monoclonal antibodies against growth-associated peptide (GAP-43), heavy neurofilament protein (RT-97), anti-mouse-specific membrane glycoprotein Thy-1.2, and polyclonal antibody to calcitonin gene-related peptide (CGRP). Absence of axonal marker staining in target structures of control animals 10 days or 3 months following ipsilateral enucleation of the L3-L6 DRG without grafting indicated an elimination of host normal (intact), regenerating, or collaterally sprouting nerve fibers. The consistent finding of immunolabeled axons ending free and in encapsulated structures in the target tissues of both allo- and xenografted rats indicates that grafted primary sensory neurons can survive and send axonal processes down the full length of the hind limb, to terminate in host target tissues. Axons of xenografted fetal mouse sensory neurons grow in adult rat hosts for distances of 4 cm or more, attaining lengths far greater than called for by their normal developmental programs.

Peripherally grafted human foetal dorsal root ganglion cells extend axons into the spinal cord of adult host rats by circumventing dorsal root entry zone astrocytes.

Human foetal dorsal root ganglia were grafted in place of native lumbar dorsal root ganglia in adult rat hosts. Between 4 weeks and 4 months later, the dorsal root entry zone (DREZ) in the grafted roots showed extensive peripheral outgrowth of astrocytic processes, in contrast to the normal 'smooth' interface between the peripheral and central nervous system compartments of the DREZ. Fibres originating from the grafted neurones and approaching the DREZ changed their direction of growth and entered the spinal cord through the pia by following blood vessels, grew into the grey matter and ramified there. These findings suggest that the DREZ astrocytes in vivo are non-permissive not only to mature peripheral regenerating axons, but also to growing axons from immature neurones.

Expression of mRNAs for neurotrophin receptors in the dorsal root ganglion and spinal cord during development and following peripheral or central axotomy.

Expression of mRNAs for the protein tyrosine kinases trk, trkB and trkC, encoding essential components of high-affinity neurotrophin receptors, was studied in the spinal cord and dorsal root ganglion during normal development and in the adult rat following peripheral and central axon injury. Northern blots revealed multiple trkB transcripts in the embryonic, early postnatal and adult spinal cord with different patterns of expression during development. The levels of 9.0 kb and 4.8 kb trkB transcripts, encoding a full-length trkB receptor, increased progressively during embryonic development with maximal levels around birth, followed by a decline at adulthood. In contrast, the level of 7.5/7.0 kb trkB transcripts, encoding a truncated trkB receptor, reached maximal levels shortly after birth and similar levels remained in the adult animal. In the spinal cord a 4.7kb trkC transcript was detected with maximal levels shortly after birth. In situ hybridization revealed a uniform labeling throughout the spinal cord for both trkB and trkC mRNAs with maximal intensities of labeling shortly after birth. The level of the 2.4 kb trkB transcript in the spinal cord increased 5-fold 8 days after a crush lesion of the sciatic nerve or the dorsal root, while no change was seen in the levels of the other trkB transcripts. No change in the 4.7 kb trkC mRNA was seen following these two injuries, although increased levels of several smaller size trkC transcripts were observed. For both trkB and trkC, similar size transcripts as seen in the spinal cord were also detected in adult rat dorsal root ganglia. Consistent with previous observations of decreased levels of cytoskeletal proteins after peripheral and central axotomy, the level of neurofilment light chain mRNA decreased markedly in the dorsal root ganglia following a crush lesion of the sciatic nerve or of the dorsal root. A small decrease was also seen in the level of preprotachykinin-A mRNA encoding the protein precursor of substance P. In the same animals, the levels of all five trkB transcripts increased 3-fold in the dorsal root ganglia in response to these two injuries. A small increase was also seen in the level of trkC mRNA. The level of brain-derived neurotrophic factor (BDNF) mRNA increased two-fold in the dorsal root ganglia following either of the two lesions, while no change was detected in trk mRNA following these two injuries.(ABSTRACT TRUNCATED AT 400 WORDS)

Differentiation and axonal outgrowth pattern of fetal dorsal root ganglion cells orthotopically allografted into adult rats.

Fetal allogeneic dorsal root ganglia (DRG) between 13 and 15 days (E13-E15) were transplanted into the enucleated fourth and fifth lumbar (L4, L5) ganglionic capsules of adult rat hosts. Some of the grafts were prelabeled with the vital carbocyanine dye DiI. Three to 9 months later, neuroanatomic tracers were applied singly or in combination to the sciatic nerve at a transection site 2-3 cm distal to the ganglion and to the dorsal quadrant of the spinal cord. Tissues in selected cases were stained with antibodies to calcitonin gene-related peptide (CGRP) or to neurofilament protein (antibody RT-97) as evidence of neuronal differentiation and axonal growth. In two grafted animals serial sections were made across the root-cord junction which was examined by light and electron microscopy. This material was compared to similarly prepared sections from two nongrafted animals subjected to dorsal root crush. Some grafted ganglion neurons survived for the 3-9 months of the study. Many of these cells became labeled after tracers were applied to the peripheral nerve, to the lumbar spinal cord, or to both. Additional signs of differentiation included expression of CGRP and neurofilament protein immunoreactivity in neuronal cell bodies and processes. Electron microscopic examination showed many small diameter fibers, both myelinated and unmyelinated, in the grafted root on both sides of the PNS/CNS junction. The results with this orthotopic transplantation model show that fetal DRG neurons can differentiate in an adult host and grow axonal branches into peripheral nerves as well as centrally through the dorsal root toward the spinal cord. In addition, our findings suggest that some of the centrally growing fibers cross the PNS/CNS border into the mature spinal cord.

Combination of non-specific cholinesterase histochemistry and immunofluorescence staining for the study of the sensory innervation of skin and muscle.

In the present study we describe the application of the non-specific cholinesterase (nChE) histochemical method for the detection of encapsulated sensory nerve endings prior to immunofluorescence staining of the sensory nerve fibres. The nChE staining of Schwann-derived structures surrounding sensory terminals allowed us to identify unequivocally the sensory corpuscles in the skin and the muscle proprioceptors (muscle spindles and Golgi tendon organs) in longitudinal sections of muscle tissue. The nChE staining of sensory nerve endings and immunofluorescence-labelled nerve fibres and their terminals could be viewed and photographed in the same section using appropriate filters. Since nChE activity persists in terminal Schwann cells for a long time after loss of the sensory axons, this combined enzyme- and immunohistochemical approach is also useful for experimental studies involving denervation and re-innervation of sensory nerve endings.

Centrifugal growth in orthotopic grafts of allogeneic dorsal root ganglia in adult rats: evidence for possible central ingrowth?

Fetal allogeneic dorsal root ganglion (DRG) transplants from 13-15 day rat embryo's (E13-E15) survived and differentiated when grafted orthopically (within the capsules of the excised 4th and 5th lumbar (L4-L5) ganglia) in adult rats. Survival of grafted neurones was established by prelabeling the grafts with a fluorescent vital dye (DiI) and visualizing the retained fluorescent marker 3 to 9 months later. Simultaneous retrograde tracing using fluorescent tracers applied in the spinal cord and peripheral nerve, respectively, yielded double-labeled dorsal root ganglion neurons, some of which were prelabeled. These findings demonstrate that prelabeled E13-E15 ganglia survive orthopic grafting, organotypically differentiate into mature DRG neurones, and can be double-labeled with fluorescent dyes applied to their peripherally and centrally directed processes. The presence of DiI containing cells which were retrogradely labeled from the spinal cord suggests that fetal (E13-E15) ganglia may have the capability of growing into a mature spinal cord.

Rabbit retinal ganglion cells survive optic nerve transection and entubulation repair with type I collagen nerve guide tubes.

The major objective of the experiments reported in this paper was to qualitatively test the hypothesis that rabbit retinal ganglion cells survive optic nerve transection and entubulation repair of the proximal optic nerve stump. The optic nerve of rabbits was transected immediately behind the globe, and a 1-cm length of a Type I collagen nerve guide tube was sutured onto the short proximal stump. The nerve guide was either left empty or was filled with a Type I collagen gel (Vitrogen, Collagen Corp.). Following 8-12 weeks survival time, the animals were sacrificed and the retinae were prepared as whole mounts and processed for immunocytochemistry using an antibody which selectively labels the retinal ganglion cells. Although no formal cell counts were carried out, the animals which received Vitrogen within the nerve guide showed a qualitative enhancement of retinal ganglion cell survival compared to the group with the nerve guide alone. The results suggest that specific manipulations of the central nervous system microenvironment may enhance neuronal survival following axonal transection.