Browsing by Author "Olivares, Jorge"
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Publication A minimal One Health approach? Lessons from the salmon aquaculture crisis in Chile(2025) Aguilera, Bernardo; Lecaros Urzúa, Juan Alberto; Olivares, JorgeThis paper explores the application of the One Health approach through an analysis of the response to the 2007 crisis in Chile's salmon aquaculture industry. To evaluate the extent to which the case aligns with a "minimal" One Health framework, we draw on four key dimensions of this framework (methodological, epistemic, ontological, and ethical) and contrast the case with the response to the 2009 Q fever outbreak in the Netherlands. We conclude that the Dutch response to Q fever, characterized by limited institutional collaboration, a narrow disciplinary focus, and an anthropocentric ethical stance, fell short of even a minimal One Health approach. In contrast, the response by the Aquaculture Health Management Program (PGSA) to Chile's salmon aquaculture crisis represents a more integrated approach, involving multisectoral collaboration, interdisciplinary dialogue, and concern for animal and environmental health. While the Chilean case does not fully achieve a strong One Health model, it demonstrates the practical benefits of adopting a minimal One Health perspective, including reduced antibiotic use and improved disease control. The paper concludes that One Health should be understood as a flexible, problem-solving framework, and that clarity regarding its core dimensions is essential for strengthening One Health approaches.Publication Antimicrobial Resistance in the Aconcagua River, Chile: Prevalence and Characterization of Resistant Bacteria in a Watershed Under High Anthropogenic Contamination Pressure(2025) González, Nicolás; Lira, Diego; Covarrubia, Richard; Plaza, Johan; Munita, Jose M.; Carter, Mauricio; Olivares, JorgeBackground: Antimicrobial resistance (AMR) is a growing global health concern, driven in part by the environmental release of antimicrobial-resistant bacteria (ARB) and antimicrobial resistance genes (ARGs). Aquatic systems, particularly those exposed to urban, agricultural, and industrial activity, are recognized as hotspots for AMR evolution and transmission. In Chile, the Aconcagua River-subject to multiple anthropogenic pressures-offers a representative model for studying the environmental dimensions of AMR. Methods: Thirteen surface water samples were collected along the Aconcagua River basin in a single-day campaign to avoid temporal bias. Samples were filtered through 0.22 μm membranes and cultured on MacConkey agar, either unsupplemented or supplemented with ceftazidime (CAZ) or ciprofloxacin (CIP). Isolates were purified and identified using MALDI-TOF mass spectrometry. Antibiotic susceptibility was evaluated using the Kirby-Bauer disk diffusion method in accordance with CLSI guidelines. Carbapenemase activity was assessed using the Blue-Carba test, and PCR was employed for the detection of the blaVIM, blaKPC, blaNDM, and blaIMP genes. Results: A total of 104 bacterial morphotypes were isolated; 80 were identified at the species level, 5 were identified at the genus level, and 19 could not be taxonomically assigned using MALDI-TOF. Pseudomonas (40 isolates) and Aeromonas (25) were the predominant genera. No growth was observed on CIP plates, while 24 isolates were recovered from CAZ-supplemented media, 87.5% of which were resistant to aztreonam. Five isolates exhibited resistance to carbapenems; two tested positive for carbapenemase activity and carried the blaVIM gene. Conclusions: Our results confirm the presence of clinically significant resistance mechanisms, including blaVIM, in environmental Pseudomonas spp. from the Aconcagua River. These findings highlight the need for environmental AMR surveillance and reinforce the importance of adopting a One Health approach to antimicrobial stewardship and wastewater regulation.Publication Ceftazidime/avibactam resistance is associated with PER-3-producing ST309 lineage in Chilean clinical isolates of non-carbapenemase producing Pseudomonas aeruginosa(2024) Soto, Katherine; Alcalde, Manuel; Ugalde, Juan; Olivares, Jorge; Quiroz, Valeria; Brito, Bárbara; Rivas Jiménez, Lina María; Munita, Jose M.; García, Patricia; Wozniak, AnielaIntroduction: Ceftazidime/avibactam (CZA) is indicated against multidrug-resistant Pseudomonas aeruginosa, particularly those that are carbapenem resistant. CZA resistance in P. aeruginosa producing PER, a class A extended-spectrum β-lactamase, has been well documented in vitro. However, data regarding clinical isolates are scarce. Our aim was to analyze the contribution of PER to CZA resistance in non-carbapenemase-producing P. aeruginosa clinical isolates that were ceftazidime and/or carbapenem non-susceptible. Methods: Antimicrobial susceptibility was determined through agar dilution and broth microdilution, while bla PER gene was screened through PCR. All PER-positive isolates and five PER-negative isolates were analyzed through Whole Genome Sequencing. The mutational resistome associated to CZA resistance was determined through sequence analysis of genes coding for PBPs 1b, 3 and 4, MexAB-OprM regulators MexZ, MexR, NalC and NalD, AmpC regulators AmpD and AmpR, and OprD porin. Loss of bla PER-3 gene was induced in a PER-positive isolate by successive passages at 43°C without antibiotics. Results: Twenty-six of 287 isolates studied (9.1%) were CZA-resistant. Thirteen of 26 CZA-resistant isolates (50%) carried bla PER. One isolate carried bla PER but was CZA-susceptible. PER-producing isolates had significantly higher MICs for CZA, amikacin, gentamicin, ceftazidime, meropenem and ciprofloxacin than non-PER-producing isolates. All PER-producing isolates were ST309 and their bla PER-3 gene was associated to ISCR1, an insertion sequence known to mobilize adjacent DNA. PER-negative isolates were classified as ST41, ST235 (two isolates), ST395 and ST253. PER-negative isolates carried genes for narrow-spectrum β-lactamases and the mutational resistome showed that all isolates had one major alteration in at least one of the genes analyzed. Loss of bla PER-3 gene restored susceptibility to CZA, ceftolozane/tazobactam and other β-lactamsin the in vitro evolved isolate. Discussion: PER-3-producing ST309 P. aeruginosa is a successful multidrug-resistant clone with blaPER-3 gene implicated in resistance to CZA and other β-lactams.Item Comparación del número de especies detectadas por los métodos de diagnóstico para DEMODEX SPP. en pacientes con rosácea de Clínica Alemana de Vitacura, año 2022(2023) Di Gennaro, Angelo; Olivares, Jorge; Olivares, TomásDemodex spp. es un ectoparásito microscópico que forma parte de la microbiota de la piel del ser humano, sin embargo, su presencia se ha relacionado a un rol patógeno en la Rosácea, que es una enfermedad inflamatoria cutánea crónica que se presenta con flushing, eritema persistente, telangiectasias, pápulas y pústulas en la zona facial. Para su diagnóstico, se pueden utilizar dos métodos, la Biopsia de Superficie Cutánea Estandarizada y el Examen Microscópico Directo, útiles para tomar muestras de piel en las que se pueda observar este ectoparásito, pero se desconoce, actualmente, cuál de ellos detecta mayor cantidad de ácaros en pacientes con Rosácea. Objetivo: Determinar cuál método detecta significativamente una mayor cantidad de ácaros en pacientes con Rosácea de la Clínica Alemana de Vitacura, Santiago de Chile. Metodología: Se aplicaron los métodos de Biopsia de Superficie Cutánea Estandarizada y Examen Microscópico Directo en 30 pacientes diagnosticados con Rosácea, para luego hacer el conteo de ácaros al microscopio, que fue registrado posteriormente en una base de datos, obteniendo así el promedio de los ácaros pesquisados con ambos métodos y realizando un análisis estadístico. Resultado: El método de Biopsia de Superficie Cutánea Estandarizada detecta significativamente mayor cantidad de ácaros que el método de Examen Microscópico Directo en pacientes con Rosácea. Conclusión: el método de Biopsia de Superficie Cutánea Estandarizada posee mayor detección de Demodex spp. en pacientes con Rosácea, lo que influye en la positividad y en la obtención del tratamiento oportuno, por ende, es importante implementarlo en el diagnóstico.Publication Comparison of two techniques for measuring Demodex folliculorum and Demodex brevis in rosacea patients: standardized skin surface biopsy vs. direct microscopic examination(2025) Pérez Wilson, Jaime; Andreani Figueroa, Sebastián; Aspillaga Vergara, Soledad; Benedetto Eblen, Juana; Lecaros Cornejo, Cristóbal; García Ramos, Viviana; Méndez Villanueva, Diego; Velásquez Muñoz, Daniel; Ríos, Paulina; Di Gennaro, Angelo; Olivares, Tomás; Olivares, JorgeRosacea is a chronic inflammatory skin disease affecting approximately 5.4% of the world population. Among its pathogenic factors is infestation by Demodex spp. Standardized skin surface biopsy (SSSB) and direct microscopic examination (DME) are widely used methods to measure Demodex spp density (Dd); however, there is no agreement on the method of choice, nor the prevalence of infestation in rosacea patients. This study compared both techniques in rosacea patients. A prospective study was conducted with 61 patients diagnosed with rosacea by dermatologists from two dermatology centres. Dd was evaluated using SSSB and DME in each patient. Results, median sampling time and reported pain were analyzed using appropriate statistical methods. The median Dd was significantly higher with SSSB (11 mites/cm2) compared to DME (1 mites/cm2; P < 0.001). Infestation (>5 mites/cm2) was detected in 64% of patients with SSSB and in 28% with DME (P < 0.001). The median sampling time was longer for SSSB (60 s) than for DME (30 s; P < 0.001). Both methods were associated with mild pain, slightly lower with DME (P = 0.033). SSSB proved more effective than DME for detecting Demodex spp. in rosacea, identifying a greater total number of mites and a higher percentage of infestation. Up to 64% of rosacea patients showed infestation with Demodex spp. using the SSSB technique. The results reinforce the use of SSSB as the standard technique for diagnosing Demodex spp. infestation in rosacea patients.Publication Genetic characterization of clinically relevant class 1 integrons carried by multidrug resistant bacteria (MDRB) isolated from the gut microbiota of highly antibiotic treated Salmo salar(2022) Vásquez, Felipe; Higuera, Sebastián; Parás, Juan; Cortés, Jimena; Opazo, Andrés; Ugalde, Juan; Alcalde, Manuel; Olivares, JorgeObjectives: The main objective of this study was the genetic characterization of clinically relevant class 1 integrons carried by multidrug resistant bacteria isolated from the intestinal microbiota of aquaculture salmon treated with high concentrations of antibiotics. Methods: In 82 multidrug resistant bacterial isolates, the prevalence of both the conserved elements of the integrons, qacEΔ1 and sul1 genes, and the variable region (VR) was determined. Further, whole genome sequencing and complete genetic analysis was performed in VR-positive isolates. Results: Despite the fact that 100% of the bacterial isolates presented the intI1 gene, only 12.3% carried the qacEΔ1 and sul1 genes and only two (2.4%) presented a VR with gene cassettes. In the Pseudomonas baetica 25P2F9 isolate, a VR carrying aac(6')31, qacH, and blaOXA-2 gene cassettes was described, whereas the VR of Aeromonas salmonicida 30PB8 isolate showed a dfrA14 gene cassette. The array of gene cassettes found in the Pseudomonas isolate appears with high frequency in clinically relevant pathogens such as Pseudomonas aeruginosa or Escherichia coli. Additionally, it was possible to determine that these integrons are contained in plasmids and coul be easily transferred. Resistome analysis demonstrated that both isolates carried a great diversity of antibiotic resistance genes, including many β-lactamases. Even in the Aeromonas isolate a new oxacillin-hydrolyzing beta-lactamase gene was described (blaOXA-956). Conclusion: The presence of multidrug resistant bacteria and clinically relevant genetic elements in the salmon intestinal microbiota make the aquaculture a hotspot in the phenomenon of antibiotic resistance; therefore, the control of antibiotics used in this activity is a key point to avoid its escalation.Publication Geographic divergence of methicillin-resistant Staphylococcus aureus ST5-SCCmecI in the aftermath of a major earthquake and tsunami: impact of a plasmid harboring heavy metal resistance genes(2025) Martínez, Jose; Alcalde, Manuel; Jara, Estefanía; Reyes, Jinnethe; Carvajal, Lina; Rincon, Sandra; Ríos, Rafael; Diaz, Lorena; Quesille, Ana; Riquelme, Roberto; Rivas Jiménez, Lina María; Moustafa, Ahmed; Hanson, Blake; Undurraga, Eduardo; Olivares, Jorge; García, Patricia; Araos Bralic, Rafael Ignacio; Planet, Paul; Arias, César; Munita, Jose M.El Staphylococcus aureus resistente a la meticilina (SARM) es una importante amenaza para la salud pública. La propagación global del SARM se caracteriza por sucesivas oleadas de clones epidémicos que dominan regiones geográficas específicas. Se cree que la adquisición de genes que codifican la resistencia a metales pesados (GMMP) es una característica clave en la divergencia geográfica del SARM. Sin embargo, la relación causa-efecto entre la presencia de GMMP y la divergencia de los clones de SARM aún no se ha dilucidado. En este estudio, evaluamos el papel que los GMMP pudieron haber desempeñado en la divergencia evolutiva del linaje ST5-SCC mec I del SARM en Latinoamérica. Realizamos una caracterización genómica de 113 aislamientos clínicos de SARM de seis centros de salud latinoamericanos, incluyendo 53 aislamientos recolectados en dos ciudades de Chile (Santiago y Concepción). Encontramos un plásmido (pSCL4752) que alberga genes de resistencia al arsénico, cadmio y mercurio en el 65% ( n = 71) de los aislados ST5-SCC mec I. También observamos una divergencia geográfica asociada a la presencia de pSCL4752 en aislados chilenos, con una mayor frecuencia en aislados de Concepción (88%) en comparación con Santiago (29%). Curiosamente, un análisis de reloj molecular reveló que esta divergencia se produjo tras el terremoto y tsunami de magnitud 8,8 Mw que azotó la zona de Concepción en 2010. Además, nuestros resultados demuestran que la presencia de pSCL4752 puede ser beneficiosa o perjudicial para los aislados ST5-SCC mec I, dependiendo de la disponibilidad ambiental de estos metales pesados. Nuestros resultados sugieren que la divergencia del linaje ST5-SCC mec I MRSA en América Latina podría haber sido fomentada por desastres ambientales e influenciada por la presencia/ausencia de HMRG albergados en un plásmido. IMPORTANCIA El Staphylococcus aureus resistente a la meticilina (MRSA) es una de las principales causas de infecciones potencialmente mortales en todo el mundo y una creciente preocupación para la salud pública. El aumento de bacterias resistentes a los antibióticos, como el MRSA, a menudo está vinculado a adaptaciones genéticas que mejoran su supervivencia. Nuestra investigación arroja luz sobre cómo los cambios ambientales, como los desencadenados por un desastre natural, pueden influir en la evolución y la propagación geográfica de un linaje de MRSA altamente resistente en América Latina. Identificamos un plásmido que porta genes de resistencia al arsénico, cadmio y mercurio, el cual se asoció con la divergencia geográfica del ST5-SCC mec.Se ha identificado un linaje de SARM con diferencias notables en su prevalencia entre las regiones afectadas por un gran terremoto y tsunami. Al vincular los eventos ambientales con la evolución del patógeno, nuestro estudio destaca el papel de las presiones ecológicas en la propagación del SARM. Estos hallazgos subrayan la necesidad de integrar el monitoreo ambiental en las estrategias de salud pública para comprender mejor el desafío global de la resistencia a los antimicrobianos.Item Real-world Performance of Susceptibility Testing for Ceftolozane/Tazobactam Against Non-Carbapenemase-Producing Carbapenem-Resistant Pseudomonas aeruginosa(2021) Rivas, Lina; Alcalde-Rico, Manuel; Martínez, José R.; Moreno, Victoria; Rojas, Pamela; Wozniak, Aniela; García, Patricia; Olivares, Jorge; Miller, William R.; Arias, Cesar A.; Khan, Ayesha; Munita, JoséCeftolozane/tazbactam (C/T) is a potent anti-pseudomonal agent that has clinical utility against infections caused by non-carbapenemase producing carbapenem-resistant P. aeruginosa (non-CP-CR-PA). Accurate, precise and reliable antimicrobial susceptibility testing (AST) is crucial to guide clinical decisions. However, studies assessing the performance of different AST methods against non-CP-CR-PA- (the main clinical niche for C/T), are lacking. Here, we evaluated performance of gradient strips (Etest and MIC test strip (MTS), and disk diffusion (DD) using CLSI breakpoints. Additionally, we assessed the performance of DD using EUCAST breakpoints. For all susceptibility tests, we used a collection of 97 non-CP-CR-PA clinical isolates recovered from 11 Chilean hospitals. Both gradient strips and DD had acceptable performance when using CLSI breakpoints, yielding a categorical agreement (CA) of >90% and 92%, respectively. In contrast, DD using EUCAST breakpoints performed sub-optimally (CA 81%). MTS yielded a higher essential agreement (EA, >90%) than Etest (84%). Importantly, the performance of all methods varied significantly when the isolates were stratified by their degree of susceptibility to other anti-pseudomonal β-lactams. All methods had 100% CA when testing isolates that were pan-susceptible to all β-lactams (Pan-β-S). However, the CA markedly decreased when testing isolates resistant to all β-lactams (Pan-β-R). Indeed, the CA was 81% for Etest (6 errors), 78% for MTS (7 errors) and 78% and 56% for DD when using CLSI (7 errors) or EUCAST breakpoints (14 errors), respectively. Our results suggest that all manual AST methods have strikingly decreased performance in the context of Pan-β-R P. aeruginosa with potentially major clinical implications.