Browsing by Author "Legarraga, Paulette"

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    Bacterial identification based on protein mass spectrometry: A new insight at the microbiology of the 21st century
    (SOC CHILENA INFECTOLOGIA, 2012) Garcia, Patricia; Allende, Fidel; Legarraga, Paulette; Huilcaman, Marcos; Solari, Sandra
    Bacterial identification is important for the proper treatment of infected patients hospitalized with serious infections especially in critical care units. Identification by conventional methods used in microbiology laboratories takes at least 16 hours since a culture is positive. The introduction of mass spectrometry, specifically MALDI-TOF MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometer) in the microbiology laboratory could mean a radical change in the identification accuracy, turn around time (6 minutes per bacteria) and cost (about 5 times cheaper than conventional identification). Since its introduction in clinical microbiology laboratories in 2008, many reports about its usefulness in identifying microorganisms from colonies, as well as directly from positive blood cultures and urine samples have been published. This review describes MALDI-TOF MS methodology, its identification performance for bacteria (aerobic and anaerobic), mycobacterium and yeasts, its future applications in microbiology and its main disadvantages.
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    Chromosome-Mediated Colistin Resistance in Clinical Isolates of Klebsiella pneumoniae and Escherichia coli: Mutation Analysis in the Light of Genetic Background
    (Dove Medical Press Ltd, 2023) Riquelme, María Paz; Martínez, Rodrigo W.; Brito, Bárbara; García, Patricia; Wozniak Banchero, Aniela; Legarraga, Paulette
    © 2023 Riquelme et al.Purpose: Colistin resistance mechanisms involving mutations in chromosomal genes associated with LPS modification are not completely understood. Mutations in genes coding for the MgrB regulator frequently account for colistin resistance in Klebsiella pneumoniae, whereas mutations in genes coding for PhoPQ and PmrAB are frequent in E. coli. Our aim was to perform a genetic analysis of chromosomal mutations in colistin-resistant (MIC ≥4 µg/mL) clinical isolates of K. pneumoniae (n = 8) and E. coli (n = 7) of different STs. Methods: Isolates were obtained in a 3-year period in a university hospital in Santiago, Chile. Susceptibility to colistin, aminoglyco-sides, cephalosporins, carbapenems and ciprofloxacin was determined through broth microdilution. Whole genome sequencing was performed for all isolates and chromosomal gene sequences were compared with sequences of colistin-susceptible isolates of the same sequence types. Results: None of the isolates carried mcr genes. Most of the isolates were susceptible to all the antibiotics analyzed. E. coli isolates were ST69, ST127, ST59, ST131 and ST14, and K. pneumoniae isolates were ST454, ST45, ST6293, ST380 and ST25. All the isolates had mutations in chromosomal genes analyzed. K. pneumoniae had mutations mainly in mgrB gene, whereas E. coli had mutations in pmrA, pmrB and pmrE genes. Most of the amino acid changes in LPS-modifying enzymes of colistin-resistant isolates were found in colistin-susceptible isolates of the same and/or different ST. Eleven of them were found only in colistin-resistant isolates. Conclusion: Colistin resistance mechanisms depend on genetic background, and are due to chromosomal mutations, which implies a lower risk of transmission than plasmid-mediated genes. Colistin resistance is not associated with multidrug-resistance, nor to high-risk sequence types.
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    Clinical and epidemiological changes of candidemia among adult patients from 2000 to 2013
    (SOC CHILENA INFECTOLOGIA, 2017) Siri, Leonardo; Legarraga, Paulette; Garcia, Patricia; Gonzalez, Tamara; Rabagliati, Ricardo
    Background: Invasive Candida spp. infections have been described more frequently. Aim: To characterize the epidemiological data of candidemia in recent years. Methods: A retrospective study of adult patients in a University Hospital in Santiago, Chile, with 1 or more documented episodes of candidemia, from January 2000 to December 2013. Results: One hundred and twenty episodes of candidemia were identified in 120 patients, annual incidence of 0.4 cases per 1000 discharges, 53.3% were male patients, 58.3%> 60 years, 77,5% had at least one co-morbidity. Candida albicans was the species most frequently identified 55%, followed by C. glabrata 18.3%, C. tropicalis 11.7% and C. parapsilosis 9.2%. Comparing 2000-2006 vs 2007-2013, increased the frequency of C. parapsilosis among non-albicans and echinocandins prescription. Patients with C. albicans showed higher APACHE-II, more requirement for invasive mechanical ventilation, greater association with CVC, and shorter incubation time compared with non-albicans species. The 30-day mortality was 31.7%. Conclusions: During this 14-years period we observed that C. albicans was the predominant specie and more recently a change among C. non-albicans increasing C. parapsilosis and decreasing C. glabrata 30-days and attributable mortality decreased together with more echinocandins prescription.
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    Performance of the VITEK MS System for the Identification of Filamentous Fungi in a Routine Microbiological Laboratory in Chile
    (2024) Porte, Lorena; Cruz, Rodrigo; Pérez, Inia; Varela, Carmen; Díaz, Cristina; García Cañete, Patricia; Legarraga, Paulette; Valdivieso, Francisca; Weitzel, Thomas
    Background: Filamentous fungi are an emergent cause of severe infections in immunocompromised patients. Timely and accurate identification is crucial to initiate appropriate therapy. Traditional identification methods are time-consuming, labor-intensive, and operator-dependent. Ma-trix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry is a rapid and easy-to-perform identification method. This study evaluates the effectiveness of a commercial MALDI-TOF MS platform to identify filamentous fungi in a routine laboratory. Material and Methods: We included 67 fungal isolates from 35 species/species complexes within 15 genera, confirmed in mycology reference laboratories. 33 were from clinical samples and 34 from strain collections. The study used the VITEK MS system (v3.2.0 database), after sample extraction by VITEK MS Mould Kit. Results were classified into categories: ‘correct species’, ‘correct species complex’, ‘correct genus’, ‘incorrect identification’, and ‘no identification’. We also evaluated the practicality of the kit. Results: VITEK MS correctly identified 91.0% of isolates (58.2% to species, 29.9% to species complex, and 1.5% to genus level). In 82%, the result matched the species/species complex identified by reference methods. No misidentifications were observed. The kit was rapid and easy to use. Conclusion: The VITEK MS system showed a high capability to accurately identify filamentous fungi in a routine laboratory.