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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
(American Society for Microbiology, 2025-04-09)
Jose R. W. Martínez
;
Manuel Alcalde-Rico
;
Estefanía Jara-Videla
;
Jinnethe Reyes
;
Lina P. Carvajal
(MRSA) is a major public health menace. The global spread of MRSA is characterized by successive waves of epidemic clones dominating specific geographical regions. The acquisition of genes encoding resistance to heavy metals (HMRGs) is thought to be a key feature in the geographic divergence of MRSA. However, the cause-effect relationship between the presence of HMRGs and the divergence of MRSA clones remains to be clarified. In this study, we assessed the role that HMRGs may have played in the evolutionary divergence of the MRSA ST5-SCC <jats:italic>mec</jats:italic> I lineage in Latin America. We conducted a genomic characterization of 113 MRSA clinical isolates from six Latin American healthcare centers, including 53 isolates collected from two cities in Chile (Santiago and Concepción). We found a plasmid (pSCL4752) harboring arsenic, cadmium, and mercury resistance genes in 65% ( <jats:italic>n</jats:italic> = 71) of the ST5-SCC <jats:italic>mec</jats:italic> I isolates. We also observed a geographic divergence associated with the presence of pSCL4752 in Chilean isolates, with a higher frequency in isolates from Concepción (88%) compared to Santiago (29%). Interestingly, a molecular clock analysis revealed that this divergence occurred in the aftermath of an 8.8 Mw earthquake and tsunami that struck the Concepción area in 2010. Moreover, our results demonstrate that the carriage of pSCL4752 can be beneficial or detrimental for ST5-SCC <jats:italic>mec</jats:italic> I isolates, depending on the environmental availability of these heavy metals. Our results suggest that the divergence of the ST5-SCC <jats:italic>mec</jats:italic> I MRSA lineage in Latin America could have been fostered by environmental disasters and influenced by the presence/absence of HMRGs harbored in a plasmid. </jats:p> <jats:sec> <jats:title>IMPORTANCE</jats:title> <jats:p> Methicillin-resistant <jats:italic>Staphylococcus aureus</jats:italic> (MRSA) is a major cause of life-threatening infections worldwide and a growing public health concern. The rise of antibiotic-resistant bacteria, such as MRSA, is often linked to genetic adaptations that enhance their survival. Our research sheds light on how environmental changes, such as those triggered by a natural disaster, can influence the evolution and geographic spread of a highly resistant MRSA lineage in Latin America. We identified a plasmid carrying genes for resistance to arsenic, cadmium, and mercury, which was associated with the geographic divergence of the ST5-SCC <jats:italic>mec</jats:italic> I MRSA lineage, with striking differences in its prevalence between regions affected by a major earthquake and tsunami. By linking environmental events to pathogen evolution, our study highlights the role of ecological pressures in the spread of MRSA. These findings emphasize the need to integrate environmental monitoring into public health strategies to better understand the global challenge of antimicrobial resistance.
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Prevalence and Distribution of Salmonella in Water Bodies in South America: A Systematic Review
(MDPI AG, 2025-02-22)
Makarena Sofia Gonzalez Reyes
;
Rayana Santos Araujo Palharini
;
Felipe Ferreira Monteiro
;
Salvador Ayala
;
Eduardo A. Undurraga
The presence of Salmonella in rivers, lakes, or beaches in South America represents a challenge to public health and aquatic ecosystems. This review explores the distribution, prevalence, and the main factors contributing to the survival and spread of Salmonella, including wastewater discharge, agricultural runoff, and climatic variables such as high temperatures and precipitation. These factors also facilitate the distribution of multidrug-resistant strains in water. The review is based on bibliographic searches in various databases, focusing on Salmonella species, South American countries, and types of water bodies. Predominant serovars include S. Enteritidis and S. Typhimurium, with S. Typhi and S. Panama frequently detected in Chile, S. Enteritidis in Argentina, and S. Typhimurium in Brazil. Less common serovars, including S. Dublin and S. Paratyphi B, were identified, along with subspecies such as diarizonae and houtenae. These findings highlight the role of environmental, physicochemical, and anthropogenic factors influencing Salmonella dynamics. The review identifies research gaps, advocating for further studies to better understand the interactions between Salmonella, climate change, and human activity. Strengthening surveillance and mitigation strategies is crucial to protect water resources and public health in South America.
Scopus© Citations 3 1
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Excess burden of antibiotic-resistant bloodstream infections: evidence from a multicentre retrospective cohort study in Chile, 2018–2022
(2024)
Kasim Allel
;
Anne Peters
;
Hassan Haghparast-Bidgoli
;
Maria Spencer-Sandino
;
Jose Conejeros
Scopus© Citations 2 4
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Effectiveness of the second COVID-19 booster against Omicron: a large-scale cohort study in Chile
(2023)
Alejandro Jara
;
Cristobal Cuadrado
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Eduardo A. Undurraga
;
Christian García
;
Manuel Nájera
<jats:title>Abstract</jats:title><jats:p>In light of the ongoing COVID-19 pandemic and the emergence of new SARS-CoV-2 variants, understanding the effectiveness of various booster vaccination regimens is pivotal. In Chile, using a prospective national cohort of 3.75 million individuals aged 20 or older, we evaluate the effectiveness against COVID-19-related intensive care unit (ICU) admissions and death of mRNA-based second vaccine boosters for four different three-dose background regimes: BNT162b2 primary series followed by a homologous booster, and CoronaVac primary series followed by an mRNA booster, a homologous booster, and a ChAdOx-1 booster. We estimate the vaccine effectiveness weekly from February 14 to August 15, 2022, by determining hazard ratios of immunization over non-vaccination, accounting for relevant confounders. The overall adjusted effectiveness of a second mRNA booster shot is 88.2% (95%CI, 86.2–89.9) against ICU admissions and 90.5% (95%CI 89.4–91.4) against death. Vaccine effectiveness shows a mild decrease for all regimens and outcomes, probably linked to the introduction of BA.4 and BA.5 Omicron sub-lineages and the waning of immunity. Based on our findings, individuals might not need additional boosters for at least 6 months after receiving a second mRNA booster shot in this setting.</jats:p>
Scopus© Citations 11 2
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Trends and socioeconomic, demographic, and environmental factors associated with antimicrobial resistance: a longitudinal analysis in 39 hospitals in Chile 2008–2017
(2023)
Kasim Allel
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Jaime Labarca
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Camila Carvajal
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Patricia Garcia
;
Marcela Cifuentes
Scopus© Citations 8 4
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Transmission dynamics and control of COVID-19 in Chile, March-October, 2020
(2021)
Amna Tariq
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Eduardo A. Undurraga
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CASTILLO LABORDE, CARLA CECILIA
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Katia Vogt-Geisse
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Ruiyan Luo
<jats:p>Since the detection of the first case of COVID-19 in Chile on March 3<jats:sup>rd</jats:sup>, 2020, a total of 513,188 cases, including ~14,302 deaths have been reported in Chile as of November 2<jats:sup>nd</jats:sup>, 2020. Here, we estimate the reproduction number throughout the epidemic in Chile and study the effectiveness of control interventions especially the effectiveness of lockdowns by conducting short-term forecasts based on the early transmission dynamics of COVID-19. Chile’s incidence curve displays early sub-exponential growth dynamics with the deceleration of growth parameter,<jats:italic>p</jats:italic>, estimated at 0.8 (95% CI: 0.7, 0.8) and the reproduction number,<jats:italic>R</jats:italic>, estimated at 1.8 (95% CI: 1.6, 1.9). Our findings indicate that the control measures at the start of the epidemic significantly slowed down the spread of the virus. However, the relaxation of restrictions and spread of the virus in low-income neighborhoods in May led to a new surge of infections, followed by the reimposition of lockdowns in Greater Santiago and other municipalities. These measures have decelerated the virus spread with<jats:italic>R</jats:italic>estimated at ~0.96 (95% CI: 0.95, 0.98) as of November 2<jats:sup>nd</jats:sup>, 2020. The early sub-exponential growth trend (<jats:italic>p</jats:italic>~0.8) of the COVID-19 epidemic transformed into a linear growth trend (<jats:italic>p</jats:italic>~0.5) as of July 7<jats:sup>th</jats:sup>, 2020, after the reimposition of lockdowns. While the broad scale social distancing interventions have slowed the virus spread, the number of new COVID-19 cases continue to accrue, underscoring the need for persistent social distancing and active case detection and isolation efforts to maintain the epidemic under control.</jats:p>
Scopus© Citations 45 1
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Effectiveness of an Inactivated SARS-CoV-2 Vaccine in Chile
(2021)
Alejandro Jara
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Eduardo A. Undurraga
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Cecilia González
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Fabio Paredes
;
Tomás Fontecilla
Scopus© Citations 665 5
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Effectiveness of CoronaVac in children 3–5 years of age during the SARS-CoV-2 Omicron outbreak in Chile
(2022)
Alejandro Jara
;
Eduardo A. Undurraga
;
José R. Zubizarreta
;
Cecilia González
;
Acevedo, Johanna
<jats:title>Abstract</jats:title><jats:p>The outbreak of the B.1.1.529 lineage of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Omicron) has caused an unprecedented number of Coronavirus Disease 2019 (COVID-19) cases, including pediatric hospital admissions. Policymakers urgently need evidence of vaccine effectiveness in children to balance the costs and benefits of vaccination campaigns, but, to date, the evidence is sparse. Leveraging a population-based cohort in Chile of 490,694 children aged 3–5 years, we estimated the effectiveness of administering a two-dose schedule, 28 days apart, of Sinovac’s inactivated SARS-CoV-2 vaccine (CoronaVac). We used inverse probability-weighted survival regression models to estimate hazard ratios of symptomatic COVID-19, hospitalization and admission to an intensive care unit (ICU) for children with complete immunization over non-vaccination, accounting for time-varying vaccination exposure and relevant confounders. The study was conducted between 6 December 2021 and 26 February 2022, during the Omicron outbreak in Chile. The estimated vaccine effectiveness was 38.2% (95% confidence interval (CI), 36.5–39.9) against symptomatic COVID-19, 64.6% (95% CI, 49.6–75.2) against hospitalization and 69.0% (95% CI, 18.6–88.2) against ICU admission. The effectiveness against symptomatic COVID-19 was modest; however, protection against severe disease was high. These results support vaccination of children aged 3–5 years to prevent severe illness and associated complications and highlight the importance of maintaining layered protections against SARS-CoV-2 infection.</jats:p>
Scopus© Citations 82 8

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