Identification of Chromobacterium violaceum by MALDI-TOF mass spectrometry in blood culture

Report of Chromobacterium violaceum isolation from blood culture. Identification by MALDI-TOF mass spectrometry. Relevant report due to the site affected, infection severity, and importance of correct and rapid identification for a successful treatment and lower risk of morbidity and mortality.Keywords: Chromobacterium; blood Culture; sepsis; spectrometry, mass; Matrix-Assisted Laser Desorption-Ionizatio

MALDI-TOF mass spectrometry identification of yeast-form fungi: A comparison between methods

Introduction: Identification of yeast species has clinical and epidemiological value. Different methods can be used, such as chromogenic media, microculture on corn meal agar with Tween 80, as well as conventional biochemical and automated methods. Recently, proteomic studies employing matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry have been a major advance in diagnosis due to speed of execution and accuracy of results. Methods: For this study, 79 yeast samples were submitted to identification using chromogenic medium, microculture on corn meal-Tween 80 agar, VITEK® 2 Compact identification, and MALDI-TOF mass spectrometry. Results: Most of the 79 samples were identified, with differences in the performance of the methods used. Colonial morphology and microscopy were compatible with the genus Candida. MALDI-TOF mass spectrometry had the best performance, with 78 strains identified (98.7%), compared to VITEK® 2 Compact (92.4%) and microculture on corn meal agar (70.9%). Conclusion: MALDI-TOF mass spectrometry using the VITEK® MS instrument performed best and has proven to be a revolutionary method in clinical microbiology laboratories. Regarding the identification of C. albicans and C. tropicalis, the chromogenic medium had excellent performance, thus being a good option to optimize the process. Keywords: Mass spectrometry; matrix-assisted laser desorption-ionization; candidiasis; Candida; yeast

Identification of Cryptococcus neoformans by MALDI-TOF mass spectrometry in blood culture

This is a report of isolation of Cryptococcus neoformans from blood culture. Identification was conducted by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry. The relevance of this report is related to the site affected, the severity of the infection, and the importance of correct and rapid identification of the causative pathogen for a successful treatment and for reducing the risk of morbidity and mortality. Keywords: Cryptococcus neoformans; blood culture; spectrometry; mass; Matrix-Assisted Laser Desorption-Ionizatio

Susceptibility of Streptococcus agalactiae to erythromycin and clindamycin in pregnant women in the prenatal screening

Introduction: Group B streptococcus (GBS), or Streptococcus agalactiae, is a bacterium found in normal human microbiota. However, it may cause neonatal pneumonia, sepsis, and meningitis. Genital colonization in pregnant women is associated with a higher risk of preterm birth. The treatment of choice is antibiotic therapy with beta-lactams, but in the case of multidrug-resistance, erythromycin and clindamycin can be used.   Methods: This study evaluated bacterial cultures in the period from 2014 to 2015 from a group of 29,875 pregnant women. GBS colonization and resistance to erythromycin and clindamycin were investigated. Results: Positive cultures were found in 26.8% and 26.1% of the samples in 2014 and 2015, respectively. Levels of resistance to erythromycin and clindamycin were, respectively, 2.4% and 5.5% in 2014 and 3.2% and 6.5% in 2015. Conclusion: The investigation of GBS colonization and the evaluation of GBS resistance to erythromycin and clindamycin are of extreme relevance, given the increasing incidence of bacterial resistance, risks of preterm birth, and serious consequences to newborns, representing a global health problem.   Keywords: Streptococcus agalactiae; erythromycin; clindamycin; prenatal care; drug resistance, microbia

Extraction of the Muon Signals Recorded with the Surface Detector of the Pierre Auger Observatory Using Recurrent Neural Networks

We present a method based on the use of Recurrent Neural Networks to extract the muon component from the time traces registered with water-Cherenkov detector (WCD) stations of the Surface Detector of the Pierre Auger Observatory. The design of the WCDs does not allow to separate the contribution of muons to the time traces obtained from the WCDs from those of photons, electrons and positrons for all events. Separating the muon and electromagnetic components is crucial for the determination of the nature of the primary cosmic rays and properties of the hadronic interactions at ultra-high energies. We trained a neural network to extract the muon and the electromagnetic components from the WCD traces using a large set of simulated air showers, with around 450 000 simulated events. For training and evaluating the performance of the neural network, simulated events with energies between 1018.5, eV and 1020 eV and zenith angles below 60 degrees were used. We also study the performance of this method on experimental data of the Pierre Auger Observatory and show that our predicted muon lateral distributions agree with the parameterizations obtained by the AGASA collaboration

A search for ultra-high-energy photons at the Pierre Auger Observatory exploiting air-shower universality

The Pierre Auger Observatory is the most sensitive detector to primary photons with energies above ∼0.2 EeV. It measures extensive air showers using a hybrid technique that combines a fluorescence detector (FD) with a ground array of particle detectors (SD). The signatures of a photon-induced air shower are a larger atmospheric depth at the shower maximum (X$_{max}$) and a steeper lateral distribution function, along with a lower number of muons with respect to the bulk of hadron-induced background. Using observables measured by the FD and SD, three photon searches in different energy bands are performed. In particular, between threshold energies of 1-10 EeV, a new analysis technique has been developed by combining the FD-based measurement of X$_{max}$ with the SD signal through a parameter related to its muon content, derived from the universality of the air showers. This technique has led to a better photon/hadron separation and, consequently, to a higher search sensitivity, resulting in a tighter upper limit than before. The outcome of this new analysis is presented here, along with previous results in the energy ranges below 1 EeV and above 10 EeV. From the data collected by the Pierre Auger Observatory in about 15 years of operation, the most stringent constraints on the fraction of photons in the cosmic flux are set over almost three decades in energy