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Cost-effectiveness of screening, decolonisation and isolation strategies for carbapenem-resistant Enterobacterales and methicillin-resistant Staphylococcus aureus infections in hospitals: a sex-stratified mathematical modelling study
(Elsevier BV, 2025-03)
Kasim Allel
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Patricia Garcia
;
Anne Peters
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MUNITA SEPULVEDA, JOSE MANUEL
;
Eduardo A. Undurraga
2
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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
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Manuel Alcalde-Rico
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Estefanía Jara-Videla
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Jinnethe Reyes
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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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Excess burden of antibiotic-resistant bloodstream infections: evidence from a multicentre retrospective cohort study in Chile, 2018–2022
(2024)
Kasim Allel
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Anne Peters
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Hassan Haghparast-Bidgoli
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Maria Spencer-Sandino
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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
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Cristobal Cuadrado
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Eduardo A. Undurraga
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Christian García
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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
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Marcela Cifuentes
Scopus© Citations 8 4
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Effectiveness of an inactivated SARS-CoV-2 vaccine in children and adolescents: a large-scale observational study
(2023)
Alejandro Jara
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Eduardo A. Undurraga
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Juan Carlos Flores
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José R. Zubizarreta
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Cecilia González
Scopus© Citations 10 7
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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
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Tomás Fontecilla
Scopus© Citations 665 5
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Childhood adversity increases risk of psychotic experiences in patients with substance use disorder
(2022)
Ignacio Bórquez-Infante
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Javiera Vasquez
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Sofía Dupré
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Eduardo A. Undurraga
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Nicolás A. Crossley
Scopus© Citations 10 4
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Transmission of gram-negative antibiotic-resistant bacteria following differing exposure to antibiotic-resistance reservoirs in a rural community: a modelling study for bloodstream infections
(2022)
Kasim Allel
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Lara Goscé
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ARAOS BRALIC, RAFAEL IGNACIO
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Daniel Toro
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Catterina Ferreccio
<jats:title>Abstract</jats:title><jats:p>Exposure to community reservoirs of gram-negative antibiotic-resistant bacteria (GN-ARB) genes poses substantial health risks to individuals, complicating potential infections. Transmission networks and population dynamics remain unclear, particularly in resource-poor communities. We use a dynamic compartment model to assess GN-ARB transmission quantitatively, including the susceptible, colonised, infected, and removed populations at the community-hospital interface. We used two side streams to distinguish between individuals at high- and low-risk exposure to community ARB reservoirs. The model was calibrated using data from a cross-sectional cohort study (N = 357) in Chile and supplemented by existing literature. Most individuals acquired ARB from the community reservoirs (98%) rather than the hospital. High exposure to GN-ARB reservoirs was associated with 17% and 16% greater prevalence for GN-ARB carriage in the hospital and community settings, respectively. The higher exposure has led to 16% more infections and attributed mortality. Our results highlight the need for early-stage identification and testing capability of bloodstream infections caused by GN-ARB through a faster response at the community level, where most GN-ARB are likely to be acquired. Increasing treatment rates for individuals colonised or infected by GN-ARB and controlling the exposure to antibiotic consumption and GN-ARB reservoirs, is crucial to curve GN-ABR transmission.</jats:p>
Scopus© Citations 2 3

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