Use of equivocal zone in interpretation of results of the amplified mycobacterium tuberculosis direct test for diagnosis of tuberculosis

The sensitivity and specificity of the Amplified Mycobacterium Tuberculosis Direct (AMTD) test, evaluated with 1,363 respiratory samples (128 from tuberculous patients), were 92.97 and 98.7%, respectively. When an equivocal zone (30,000 to 1,000,000 relative light units [RLU]) was used instead of a 30,000-RLU cutoff, the sensitivity and specificity of the AMTD test were 92.97 and 100%, respectively.     

Evaluation of the automated phoenix system for potential routine use in the clinical microbiology laboratory

A comparative study was designed to evaluate the identification (ID) and antimicrobial susceptibility testing (AST) performances of the BD Phoenix Automated Microbiology System (Becton Dickinson Diagnostic Systems [BD], Pont de Claix, France). A total of 305 single clinical isolates were collected, and comparisons were made with routine manual methods in use in our microbiology laboratories. The percentages of correct IDs were 93.3, 89.4, 91.8, and 85.7% for enterobacteria, nonfermenting gram-negative bacilli, staphylococci, and streptococci-enterococci, respectively. The median ID time was 3 h, and the median time for AST was 10 h 30 min. AST results showed variable percentages of errors for the different antibiotics. None of the enterobacteria and 0.3% of Pseudomonas aeruginosa isolates showed a very major error (VME). Only one strain of Staphylococcus aureus showed a VME with oxacillin. We demonstrate here the efficiency of the Phoenix system, which can be used for the majority of strains encountered in a university-based laboratory, for ID and AST.     

IFNgamma and antibody responses among French nurses during a tuberculosis contact tracing investigation

Study

A comparative study which compared PPD skin testing inserted according to the French Society of Pneumology's recommendations and interferon gamma release assay (IGRA) (QuantiFERON^® TB Gold In-tube, QF–TB–IT, Cellestis, Carnegie, Australia) was performed during a tuberculosis contact investigation in our hospital.

Patients

Nineteen French health-care workers (HCWs) volunteered to participate. All of the HCW enrolled were BCG vaccinated and had a normal chest X-ray at entry.

Results

Among the HCW, 68.4% were TST positive. By comparison, only 31.6% had a positive QF-TB-IT result. We took advantage of the negative tube and the corresponding plasma for antibody detection by ELISA. None were ELISA positive. Fourteen HCWs were followed up. None of the HCWs accepted a course of antiTB chemoprophylaxis. Despite the difficulty in establishing a trend in kinetics, we saw the complexity of interpretation of a dynamic T-cell response after contact with an index case.

Conclusion

This initial and first French picture provides us with the observation that only 44% of TST-positive HCW were IGRA positive, and the IGRA test allowed the detection of LTBI in two TST negative HCWs.     

Heterogeneity in the granulomatous response to mycobacterial infection in patients with defined genetic mutations in the interleukin 12-dependent interferon-gamma production pathway

Patients with genetic lesions in the Type-1 cytokine/cytokine receptor pathway exhibit a selective susceptibility to severe infections with poorly pathogenic mycobacteria and non-typhi salmonella spp. These experiments of nature demonstrate that IL-12-dependent IFNgamma production is critical for granuloma formation and therefore host immunity against such pathogens. The essential role of granuloma formation for protective immunity to these organisms is emphasized by the differing granuloma forming capabilities and resultant clinical sequelae observed in these patients which seems to reflect their ability to produce or respond to IFNgamma (Fig. 9). At one pole of this spectrum, represented by the complete IFNgammaR1/2 deficient patients, there is a complete absence of mature granuloma formation, whereas with the less severe mutations (i.e. partial IFNgammaR1/2, complete IL-12p40 and complete IL-12Rbeta1 deficiency), granuloma formation is very heterogenous with wide variations in composition being observed. This suggests that in the latter individuals, who produce partial but suboptimal IFNgamma responses, other influences, including pathogen virulence and host genotype may also affect the type and scale of the cellular response elicited.     

Functional GABA(B) receptors are expressed at the cone photoreceptor terminals in bullfrog retina

GABA(B) receptors at the cone terminals in bullfrog retina were characterized by immunocytochemical and whole-cell patch clamp techniques in retinal slice preparations. Somata, axons and synaptic terminals (pedicles) of cones were both GABA(B) receptor (GABA(B)R) 1 and GABA(B)R2 immunoreactive. Physiologically, barium/calcium currents of cones to voltage steps were significantly reduced in size when GABA was puffed to cone terminals in the presence of picrotoxin that is supposed to block both GABA(A) and GABA(C) receptors. Similar reduction in barium currents was obtained with puff application of baclofen to cone terminals. These results suggest the presence of functional GABA(B) receptors at the bullfrog cone terminals. Suppression of barium currents of cones by baclofen was dose-dependent. Moreover, barium currents of cones were potentiated by background illumination, as compared with those recorded in the dark. 6,7-Dinitroquinoxaline-2,3-dione, an antagonist of non-NMDA receptors that hyperpolarizes horizontal cells and reduces GABA release from these cells, and saclofen, a GABA(B) receptor antagonist, both potentiated barium currents of cones in the dark, thereby mimicking the effects of background illumination. It is suggested that changes in calcium influx into the cone synaptic terminals due to activation of GABA(B) receptors may provide a negative feedback mechanism for regulating signal transmission between cones and second-order neurons in the retina by modifying the amount of glutamate released from the cones.     

Neural tube defects and vitamin B12: a report of three cases

Periconceptional folic acid supplementation reduces the frequency of embryological neural tube defects (NTD). This fact led the USA to fortify grain products with folic acid (140 microg/100 g) starting in January 1998, with a resultant decrease in the incidence of NTD. Folate deficiency is thus confirmed to be a risk factor for NTD. However, in a prospective study, we investigated three women who conceived a fetus with NTD; no folate deficiency was found in these women but all three had decreased vitamin B12 levels (cobalamin), which can be an other risk factor. Samples were obtained from two women in Algeria, 2 days after interruption of pregnancy, and from a vegetarian woman, in France, one month after interruption of pregnancy. Red cell folate and plasma folate, vitamin B12, B6 and homocysteine were assayed and the mutations C677T (in metylenetetrahydrofolate reductase gene), A2756G (in methionine synthase gene) and A66G (in methionine synthase reductase gene) were sought. Elevated plasma folate levels were found in both Algerian women. Vitamin B 12 levels in all three women were decreased or in the lowest quartile of normal values. One woman presented simultaneously a vitamin B 12 deficiency, and heterozygous mutations in the three genes. The second woman presented a A66G homozygous mutation and the third heterozygous C677T and A66G mutations. Acquired and inborn factors are intricated in some cases of pregnancies with NTD and B 12 deficiency can be responsible for intracellular folate cycle failure. It would therefore be advisable to consider fortifying grain products with both folic acid and vitamin B12.     

Synaptic transmission of chaotic spike trains between primary afferent fiber and spinal dorsal horn neuron in the rat

Primary sensory neurons can generate irregular burst firings in which the existence of significant deterministic behaviors of chaotic dynamics has been proved with nonlinear time series analysis. But how well the deterministic characteristics and neural information of presynaptic chaotic spike trains were transmitted into postsynaptic spike trains is still an open question. Here we investigated the synaptic transmission of chaotic spike trains between primary Adelta afferent fiber and spinal dorsal horn neuron. Two kinds of basic stimulus unit, brief burst and single pulse, were employed by us to comprise chaotic stimulus trains. For time series analysis, we defined "events" as the longest sequences of spikes with all interspike intervals less than or equal to a certain threshold and extracted the interevent intervals (IEIs) from spike trains. Return map analysis of the IEI series showed that the main temporal structure of chaotic input trains could be detected in postsynaptic output trains, especially under brief-burst stimulation. Using correlation dimension and nonlinear prediction methods, we found that synaptic transmission could influence the nonlinear characteristics of chaotic trains, such as fractal dimension and short-term predictability, with greater influence made under single-pulse stimulation. By calculating the mutual information between input and output trains, we found the information carried by presynaptic spike trains could not be completely transmitted at primary afferent synapses, and that brief bursts could more reliably transmit the information carried by chaotic input trains across synapses. These results indicate that although unreliability exists during synaptic transmission, the main deterministic characteristics of chaotic burst trains can be transmitted across primary afferent synapses. Moreover, brief bursts that come from the periphery can more reliably transmit neural information between primary afferent fibers and spinal dorsal horn neurons.     

MALDI-TOF MS Andromas strategy for the routine identification of bacteria, mycobacteria, yeasts, Aspergillus spp. and positive blood cultures

Clin Microbiol Infect 2012; 18: 1117-1125 ABSTRACT: All organisms usually isolated in our laboratory are now routinely identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) using the Andromas software. The aim of this study was to describe the use of this strategy in a routine clinical microbiology laboratory. The microorganisms identified included bacteria, mycobacteria, yeasts and Aspergillus spp. isolated on solid media or extracted directly from blood cultures. MALDI-TOF MS was performed on 2665 bacteria isolated on solid media, corresponding to all bacteria isolated during this period except Escherichia coli grown on chromogenic media. All acquisitions were performed without extraction. After a single acquisition, 93.1% of bacteria grown on solid media were correctly identified. When the first acquisition was not contributory, a second acquisition was performed either the same day or the next day. After two acquisitions, the rate of bacteria identified increased to 99.2%. The failures reported on 21 strains were due to an unknown profile attributed to new species (9) or an insufficient quality of the spectrum (12). MALDI-TOF MS has been applied to 162 positive blood cultures. The identification rate was 91.4%. All mycobacteria isolated during this period (22) were correctly identified by MALDI-TOF MS without any extraction. For 96.3% and 92.2% of yeasts and Aspergillus spp., respectively, the identification was obtained with a single acquisition. After a second acquisition, the overall identification rate was 98.8% for yeasts (160/162) and 98.4% (63/64) for Aspergillus spp. In conclusion, the MALDI-TOF MS strategy used in this work allows a rapid and efficient identification of all microorganisms isolated routinely.     

Dynamic interplays between memory systems depend on practice: the hippocampus is not always the first to provide solution

Previous studies showed that the optimization of behavioral performance through extended training depends on a switch from hippocampus-based memory to striatum-based habit. Here we investigate whether the amount of training within one learning session influences the retention of memory for hippocampal versus striatal strategies. Mice were trained to search for a submerged cue-marked platform which remained in the same spatial location in the water-maze for each of three training regimens (4, 12 or 22 trials). Subsequently, they were either tested for retention of memory 1 h or 24 h later on a probe test or killed at different time points over a 7-h period to determine the kinetic of cAMP response element binding protein (CREB) phosphorylation in both memory systems. During the probe test mice had to choose between a submerged platform located in the same position as during the acquisition phase (spatial solution) and a platform marked by the cue but located in the opposite quadrant of the pool (cue-guided solution). Results showed that the animals first preferred the cue-marked platform, which represents a strategy that was selectively impaired by lesions of the dorsolateral caudate-putamen. With further practice, or context pre-exposure, animals transiently favored the hippocampus-dependent place solution but finally, both strategies became interchangeable and insensitive to either lesion. CREB phosphorylation increased in both memory systems following acquisition but training-dependent changes selectively occurred in the hippocampus wherein biphasic activation was initiated by the four-trial training and blocked by training for 22 trials. These findings indicate that learning in one session consists of three acquisition stages with parallel engagement of multiple memory systems at the beginning of learning. They suggest, however, that, in a later phase, dynamic interplays promote the use of the most adapted brain system depending on practice and this is accompanied by specific patterns of CREB phosphorylation in the hippocampus.