Publications by authors named "Marissa Griffith"
We report 2 outbreaks comprising a cluster of 18 group A Streptococcal infections across 2 nursing facilities. Point prevalence surveillance testing identified 8 of 18 cases, and whole genome sequencing validated transmission pathways. Infection prevention interventions at the facility level comprised symptomatic and asymptomatic carriage-based case finding, transmission-based precautions, and treatment to eradicate colonization.
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- Current outbreak detection methods in hospitals are inadequate on their own; a new program called the Enhanced Detection System for Healthcare-associated Transmission (EDS-HAT) uses real-time genomic surveillance to identify outbreaks.
- The study, conducted at UPMC Presbyterian Hospital from November 2021 to October 2023, involved weekly whole genome sequencing of bacterial isolates, leading to the identification of 172 outbreaks and successful intervention strategies that prevented further transmission in over 95% of cases.
- Results revealed significant benefits: 62 infections were avoided, translating to over $1 million in gross savings and a net savings of nearly $700,000, showing that integrating genomic surveillance can greatly enhance infection control and patient safety.
Article Synopsis
- - The study investigates the role of heteroresistance in cefiderocol treatment failure among patients with carbapenem-resistant Acinetobacter baumannii (CRAb) infections, finding a significant portion (59%) of the isolates had heteroresistance, particularly higher in Italy compared to the USA.
- - Patients with cefiderocol-heteroresistant strains had worse clinical outcomes, with 81% experiencing treatment failure, compared to 55% for those with susceptible strains, and higher minimum inhibitory concentrations (MICs) were linked to increased failure rates.
- - Whole-genome sequencing revealed a genetic mutation in some heteroresistant isolates, supporting the idea that both higher MICs and the presence of resistant subpopulations contribute to
Article Synopsis
- ST131 E. coli is a globally recognized strain that causes hard-to-treat, multidrug-resistant infections due to its production of extended-spectrum β-lactamases (ESBLs).
- Researchers sequenced the genomes of 154 clinical isolates from the ST131 lineage at the University of Pittsburgh Medical Center and found that clade C predominated, comprising 89% of the samples.
- Analysis revealed genes under selection in clade C and highlighted the diversity of ESBL-encoding genes and mobile elements, indicating ongoing adaptation in this strain.
Article Synopsis
- VREfm is a significant healthcare-acquired pathogen that can lead to serious bloodstream infections, and previous studies focused on its presence within healthcare facilities.
- A study involving 710 clinical isolates collected from 2017-2022 revealed that nearly half of the isolates formed genetically similar clusters, indicating a high rate of transmission in the hospital.
- Comparison with a large database of VREfm genomes over 20 years showed a notable shift in the populations of VREfm within hospitals, suggesting that antimicrobial peptides like bacteriocin T8 might play a crucial role in the emergence and persistence of these strains.
Article Synopsis
- - The study focused on KPC-Kp bloodstream infections, which are deadly, and aimed to understand how these bacteria resist a key defense mechanism in our blood, called complement.
- - Researchers tested various KPC-Kp isolates from patients, discovering that 27% of them resisted killing by human serum; a specific gene mutation (wcaJ) linked to capsule production contributed to this resistance.
- - This mutation resulted in less capsule presence, paradoxically increasing the bacteria's ability to bind complement proteins while also improving their survival against immune responses, potentially allowing them to thrive in the bloodstream without being overly virulent in tissues.
Impact of discontinuation of contact precautions on surveillance- and whole genome sequencing-defined methicillin-resistant healthcare-associated infections.
Antimicrob Steward Healthc Epidemiol
June 2024
Objective: Prior studies evaluating the impact of discontinuation of contact precautions (DcCP) on methicillin-resistant (MRSA) outcomes have characterized all healthcare-associated infections (HAIs) rather than those likely preventable by contact precautions. We aimed to analyze the impact of DcCP on the rate of MRSA HAI including transmission events identified through whole genome sequencing (WGS) surveillance.
Design: Quasi experimental interrupted time series.
Article Synopsis
- VRE infections are a major healthcare challenge due to their complex transmission dynamics, which involve patient colonization and spread through various healthcare settings.
- Whole genome sequencing (WGS) was used to analyze 352 clinical and 891 rectal screening VRE isolates, revealing that the majority (87.3%) of VRE infections were acquired through rectal carriage.
- The study identified significant genetic relatedness among isolates and hotspots for VRE transmission, emphasizing the importance of WGS in infection control and highlighting the impact on patient outcomes, including ICU admissions and mortality rates.
Article Synopsis
- Many species of bacteria are resistant to antibiotics, creating challenges in treating infections caused by them.
- Bacteriophage therapy, which uses viruses that infect bacteria, may be a potential solution, but finding specific phages can be challenging.
- The study found that prophages within bacterial genomes could be a source of effective phages, showing various lytic activities against different bacterial isolates, suggesting they might be beneficial for future phage therapy.
Article Synopsis
- NDM (New Delhi metallo-β-lactamase) is a significant threat due to its role in carbapenem resistance, leading to high mortality and few treatment options.
- An outbreak at an acute care hospital was detected using traditional infection prevention methods and supplemented with weekly whole genome sequencing (WGS), which revealed complex plasmid transfer dynamics between various bacterial species.
- The investigation identified 15 patients with NDM-5-producing Enterobacterales, illustrating the effectiveness of combining traditional and genomic approaches in tracking and controlling outbreaks involving plasmid transfer and bacterial spread.
Article Synopsis
- Many bacterial species are resistant to antibiotics, making infections hard to treat and prompting interest in bacteriophage therapy as an alternative.
- Researchers investigated the ability of prophages (virus-like elements in bacteria) in these species to kill similar and different bacterial strains, identifying four distinct phages with varying effectiveness.
- The study indicates that prophages in bacteria could be a valuable resource for developing new phage therapy options, particularly since one type of bacteria was found to be more susceptible to these phages than another.
Article Synopsis
- ST131 is a global lineage of bacteria that causes drug-resistant infections, often producing enzymes that make treatment challenging.
- Researchers sequenced genomes of 154 drug-resistant isolates from a hospital to understand the lineage better.
- The study found that subclades C1 and C2 were the most common and indicated signs of ongoing changes within the bacteria, which could affect their treatment and spread.
Objective: To evaluate the utility of selective reactive whole-genome sequencing (WGS) in aiding healthcare-associated cluster investigations.
Design: Mixed-methods quality-improvement study.
Setting: Thes study was conducted across 8 acute-care facilities in an integrated health system.
Objectives: Ceftazidime/avibactam and meropenem/vaborbactam are preferred agents for carbapenemase (KPC)-producing (KPC-) infections and are often used in combination with other agents. We aimed to characterize the synergy of combinations against KPC- with varying genotypes.
Methods: KPC- that harboured WT, IS or glycine-aspartic acid duplication (GD) genotypes were selected.
We describe 2 cases of extensively drug-resistant Pseudomonas aeruginosa infection caused by a strain of public health concern, as it was recently associated with a nationwide outbreak of contaminated artificial tears. Both cases were detected through database review of genomes in the Enhanced Detection System for Hospital-Associated Transmission (EDS-HAT), a routine genome sequencing-based surveillance program. We generated a high-quality reference genome for the outbreak strain from an isolate from our center and examined the mobile elements encoding blaVIM-80 and bla-GES-9 carbapenemases.
View Article and Find Full Text PDFBackground: New Delhi metallo-β-lactamase (NDM) represents an emergent mechanism of carbapenem resistance associated with high mortality and limited antimicrobial treatment options. Because the resistance gene is often carried on plasmids, traditional infection prevention and control (IP&C) surveillance methods like speciation, antimicrobial resistance testing, and reactive whole genome sequencing (WGS) may not detect plasmid transfer in multispecies outbreaks.
Methods: Initial outbreak detection of NDM-producing Enterobacterales identified at an acute care hospital occurred via traditional IP&C methods and was supplemented by real-time WGS surveillance, which was performed weekly using the Illumina platform.
Article Synopsis
- *Researchers found that 27% of KPC-Kp isolates showed increased resistance to human serum, linked to a mutation that reduces capsule content and helps the bacteria evade immune responses.
- *The mutation allows KPC-Kp to survive better in the bloodstream while being less virulent in tissues, highlighting a complex interaction that aids the bacteria's persistence in the host.
Background: Healthcare-associated bacterial pathogens frequently carry plasmids that contribute to antibiotic resistance and virulence. The horizontal transfer of plasmids in healthcare settings has been previously documented, but genomic and epidemiologic methods to study this phenomenon remain underdeveloped. The objectives of this study were to apply whole-genome sequencing to systematically resolve and track plasmids carried by nosocomial pathogens in a single hospital, and to identify epidemiologic links that indicated likely horizontal plasmid transfer.
View Article and Find Full Text PDFWe describe two cases of XDR infection caused by a strain of public health concern recently associated with a nationwide outbreak of contaminated artificial tears. Both cases were detected through database review of genomes in the Enhanced Detection System for Hospital-Associated Transmission (EDS-HAT), a routine genome sequencing-based surveillance program. We generated a high-quality reference genome for the outbreak strain from one of the case isolates from our center and examined the mobile elements encoding and carbapenemases.
View Article and Find Full Text PDFBackground: Healthcare-associated infections can be acquired via transmission of pathogens within the healthcare setting. Often, patients are assumed to have short duration (< 90 days) of transmissibility with bacterial pathogens after developing a clinical infection. This assumption may wrongly exclude patients as sources of transmission when they have persistent bacterial carriage.
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- New β-lactam/β-lactamase inhibitors, such as ceftazidime/avibactam, meropenem/vaborbactam, and imipenem/relebactam, are showing promise in treating KPC-producing infections, but their effectiveness varies based on the specific genetic make-up of the bacteria.
- The study analyzed 104 KPC- isolates to understand how differences in their genetic profiles affected antibiotic efficacy, and found that mutations significantly influenced resistance levels.
- Time-kill tests revealed that ceftazidime/avibactam was effective across different isolates, while imipenem/relebactam struggled with certain mutations, indicating the need for targeted treatment strategies based on genetic
Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) control on college campuses is challenging given communal living and student social dynamics. Understanding SARS-CoV-2 transmission among college students is important for the development of optimal control strategies.
Methods: SARS-CoV-2 nasal swab samples were collected from University of Pittsburgh students for symptomatic testing and asymptomatic surveillance from August 2020 through April 2021 from 3 campuses.
We performed whole genome sequencing on SARS-CoV-2 from 59 vaccinated individuals from southwest Pennsylvania who tested positive between February and September, 2021. A comparison of mutations among vaccine breakthrough cases to a time-matched control group identified potential adaptive responses of SARS-CoV-2 to vaccination.
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