Variation and trends in transmission dynamics of Methicillin-resistant Staphylococcus aureus in veterans affairs hospitals and nursing homes

Health care worker carriage of drug-resistant bacteria and infection control practices at a tertiary care hospital in Uganda: a cross-sectional survey

Introduction

bacterial carriage by health care workers (HCWs) is a major risk factor for transmission of healthcare-associated infections (HAIs). Often, these pathogens are multiple drug resistant (MDR) and are transmitted from hospital environments. We aimed to study the carriage of pathogenic bacteria among HCWs at a tertiary care hospital in Uganda.

Methods

a cross-sectional study was done at Naguru Regional Referral Hospital from June 2017 to August 2017. Five finger imprints of both hands-on blood and MacConkey agar were done. We assessed pathogenic bacterial carriage by HCWs and characterized drug sensitivity and relatedness of these isolates. Genotyping of extended-spectrum beta-lactamase (ESBL) and Methicillin-resistant Staphylococcus aureus (MRSA) positive isolates was done to determine intra-hospital transmission. A survey of the hospital's IPC de program was done.

Results

one hundred and eight (108) HCWs were enrolled. Carriage of pathogenic bacteria was highest in surgical and emergency wards at 36% and 35.6% respectively, p-value of 0.00. The proportion of microbial carriage was highest among nurses 16 (34.8%) followed by medical officers 11 (23.9%). Among the isolated pathogenic bacteria, 25 (36.2%) were Gram-positive and 44 (63.8%) were Gram-negative. Fifty percent of Staphylococcus aureus were methicillin-resistant, and one isolate was vancomycin-resistant. Fifty-four percent (54.6%) of HCWs had never been trained on moments of hand hygiene, only 44.4% recognized the presence of an IPC program in the hospital and 49% were not aware of problems associated with poor IPC practices.

Conclusion

this study demonstrated that hands of HCWs at Naguru Regional Referral Hospital were colonized with pathogenic bacteria with varying prevalence, some with multidrug-resistant strains including MRSA and ESBL.

Microbiome-pathogen interactions drive epidemiological dynamics of antibiotic resistance: A modeling study applied to nosocomial pathogen control

The human microbiome can protect against colonization with pathogenic antibiotic-resistant bacteria (ARB), but its impacts on the spread of antibiotic resistance are poorly understood. We propose a mathematical modeling framework for ARB epidemiology formalizing within-host ARB-microbiome competition, and impacts of antibiotic consumption on microbiome function. Applied to the healthcare setting, we demonstrate a trade-off whereby antibiotics simultaneously clear bacterial pathogens and increase host susceptibility to their colonization, and compare this framework with a traditional strain-based approach. At the population level, microbiome interactions drive ARB incidence, but not resistance rates, reflecting distinct epidemiological relevance of different forces of competition. Simulating a range of public health interventions (contact precautions, antibiotic stewardship, microbiome recovery therapy) and pathogens (Clostridioides difficile, methicillin-resistant Staphylococcus aureus, multidrug-resistant Enterobacteriaceae) highlights how species-specific within-host ecological interactions drive intervention efficacy. We find limited impact of contact precautions for Enterobacteriaceae prevention, and a promising role for microbiome-targeted interventions to limit ARB spread.

Association Between Contact Precautions and Transmission of Methicillin-Resistant Staphylococcus aureus in Veterans Affairs Hospitals

Importance

The effectiveness and importance of contact precautions for endemic pathogens has long been debated, and their use has broad implications for infection control of other pathogens.

Objective

To estimate the association between contact precautions and transmission of methicillin-resistant Staphylococcus aureus (MRSA) across US Department of Veterans Affairs (VA) hospitals.

Design, Setting, and Participants

This retrospective cohort study used mathematical models applied to data from a population-based sample of adults hospitalized in 108 VA acute care hospitals for at least 24 hours from January 1, 2008, to December 31, 2017. Data were analyzed from May 2, 2019, to December 11, 2020.

Exposures

A positive MRSA test result, presumed to indicate contact precautions use according to the VA MRSA Prevention Initiative.

Main Outcomes and Measures

The main outcome was the association between contact precautions and MRSA transmission, defined as the relative transmissibility attributed to contact precautions. A contact precaution effect estimate (<1 indicates a reduction in transmission associated with contact precautions) was estimated for each hospital and then pooled over time and across hospitals using meta-regression.

Results

In this cohort study of 108 VA hospitals, more than 2 million unique individuals had over 5.6 million admissions, of which 14.1% were presumed to have contact precautions with more than 8.4 million MRSA surveillance tests. Pooled estimates found associations between contact precautions and transmission to be stable from 2008 to 2017, with estimated transmission reductions ranging from 43% (95% credible interval [CrI], 38%-48%) to 51% (95% CrI, 46%-55%). Over the entire 10-year study period, contact precautions reduced transmission 47% (95% CrI, 45%-49%), and the intrafacility autocorrelation coefficient estimate was 0.99, suggesting consistent estimates over time within facilities. Larger facilities and those with higher admission screening compliance observed additional reductions in transmission associated with contact precautions (relative rate, 0.84; 95% CI, 0.74-0.96 and 0.74; 95% CI, 0.58-0.96, respectively) compared with smaller facilities and those with lower admission screening compliance. Facilities in the southern US had a smaller transmission reduction attributable to contact precautions (relative rate, 1.14; 95% CI, 1.01-1.28) compared with facilities in other regions in the US.

Conclusions and Relevance

In this cohort study of adults in VA hospitals, transmissibility of MRSA was found to be reduced by approximately 50% among patients with contact precautions. These results provide an explanation for decreasing acquisition rates in VA hospitals since the MRSA Prevention Initiative.

Transmission Dynamics of Clostridioides difficile in 2 High-Acuity Hospital Units

BACKGROUND

The key epidemiological drivers of Clostridioides difficile transmission are not well understood. We estimated epidemiological parameters to characterize variation in C. difficile transmission, while accounting for the imperfect nature of surveillance tests.

METHODS

We conducted a retrospective analysis of C. difficile surveillance tests for patients admitted to a bone marrow transplant (BMT) unit or a solid tumor unit (STU) in a 565-bed tertiary hospital. We constructed a transmission model for estimating key parameters, including admission prevalence, transmission rate, and duration of colonization to understand the potential variation in C. difficile dynamics between these 2 units.

RESULTS

A combined 2425 patients had 5491 admissions into 1 of the 2 units. A total of 3559 surveillance tests were collected from 1394 patients, with 11% of the surveillance tests being positive for C. difficile. We estimate that the transmission rate in the BMT unit was nearly 3-fold higher at 0.29 acquisitions per percentage colonized per 1000 days, compared to our estimate in the STU (0.10). Our model suggests that 20% of individuals admitted into either the STU or BMT unit were colonized with C. difficile at the time of admission. In contrast, the percentage of surveillance tests that were positive within 1 day of admission to either unit for C. difficile was 13.4%, with 15.4% in the STU and 11.6% in the BMT unit.

CONCLUSIONS

Although prevalence was similar between the units, there were important differences in the rates of transmission and clearance. Influential factors may include antimicrobial exposure or other patient-care factors.