Community- and Healthcare-Associated Methicillin-Resistant Staphylococcus aureus Strains: An Investigation Into Household Transmission, Risk Factors, and Environmental Contamination

Cross-sectional study of the association of social relationship resources with Staphylococcus aureus colonization in naturally occurring social groups along the US/Mexico border

Asymptomatic carriage of Staphylococcus aureus is a major risk factor for subsequent clinical infection. Diminishing returns from mitigation efforts emphasize the need to better understand colonization, spread, and transmission of this opportunistic pathogen. While contact with other people presents opportunities for pathogen exposure and transmission, diversity of social connections may be protective against pathogens such as the common cold. This study examined whether social relationship resources, including the amount and diversity of social contacts, are associated with S. aureus colonization. Participants were community members (N = 443; 68% Hispanic) in naturally occurring social groups in southwestern Arizona. Four types of social relationships and loneliness were assessed, and samples from the skin, nose and throat were obtained to ascertain S. aureus colonization. Overall S. aureus prevalence was 64.8%. Neither the amount nor the diversity of social contacts were associated with S. aureus colonization. The concurrent validity of the social relationship assessments was supported by their moderate intercorrelations and by their positive association with self-rated health. The results suggest that the association of social network diversity and susceptibility to the common cold does not extend to S. aureus colonization. Conversely, colonization prevalence was not higher among those with more social contacts. The latter pattern suggests that social transmission may be relatively infrequent or that more intimate forms of social interaction may drive transmission and colonization resulting in high community prevalence of S. aureus colonization. These data inform communicable disease control efforts.

Tracking Infection and Genetic Divergence of Methicillin-Resistant Staphylococcus aureus at Pets, Pet Owners, and Environment Interface

Staphylococcus aureus (S. aureus) has become a leading animal and public health pathogen that keeps on transferring from one host to other, giving rise to newer strains by genetic shifts. The current study was designed to investigate the epidemiology and genetic relatedness of mecA gene in S. aureus isolated from pets, immediate individuals in contact with pets, and veterinary clinic environments. A total of n = 300 samples were collected from different veterinary hospitals in Pakistan using convenience sampling. The collected samples were subjected to microbiological and biochemical examination for the isolation of S. aureus. Methicillin resistance was investigated by both phenotypically using oxacillin disk diffusion assay and by genotypically targeting mecA gene by PCR. PCR amplicons were subjected for sequencing by Sanger method of sequencing, which were subsequently submitted to NCBI GenBank under the accession numbers MT874770, MT874771, and MT874772. Sequence evolutionary analysis and mecA gene characterization was done using various bioinformatics tools. Overall, 33.66% mecA genes harboring S. aureus strains were isolated from all sources (33.33% from pets, 46.0% from surrounding, and 28.0% from immediate contact individuals). The bioinformatics analysis noted that one SNP was identified at position c.253C>A (Transvertion). The phylogenetic tree (two clades) of S. aureus mecA revealed a possibility of inter-transmission of disease between the environment and pets. Frequency of adenine and thymine nucleotide in motifs were found to be the same (0.334). Cytosine and guanine frequency were also the same (0.166). Threonine was replaced by asparagine (p.T84D) in each sample of cat, environment, and human. On the other hand, protein structures ofcat-1 and cat-2 proteins were found identical while cat-3, environmental, and human proteins shared identical structures. The study thus concludes rising circulation of methicillin-resistant S. aureus (MRSA) strains in animal-human-environment interfaces, forecasting the development of novel strains withmodified range of resistance.

The remarkable genetic relationship between Staphylococcus aureus isolates from hemodialysis patients and their household contacts: Homes as an important source of colonization and dissemination

Introduction

Staphylococcus aureus is a successful pathogen in hospital and community. Hemodialysis patients have high colonization rates. Interactions between them and their household contacts, are an opportunity to understand the S. aureus colonization between hospitals and community. This study aims to determine the clinical and epidemiological characteristics of S. aureus colonization in hemodialysis patients and their household contacts, as well as the genetic relationship between their isolates.

Methods

A cross-sectional study was conducted on hemodialysis patients from hospital-associated dialysis center in Medellín-Colombia, and their household contacts between 2019 and 2020. Colonization was assessed in the nostrils for household contacts and nostrils and skin around the catheter insertion for hemodialysis patients. Epidemiological information was obtained, and colonization was evaluated in their pets’ oral cavities. Bacterial identification and susceptibility were assessed using phenotypic and molecular methods. Molecular typing included SCCmec typing, pulsed-field gel electrophoresis (PFGE), spa typing, and virulence factor detection.

Results

Colonization frequency was 35.6% (n = 16/45) in patients (87.5% MSSA– 12.5% MRSA) and 43.1% (n = 53/123) in household contacts (88.7% MSSA—11.3% MRSA). Of 45 homes, 77.8% presented colonized people. Colonization was detected in at least two household members in 46.7% of homes, of which 52.4% had a genetic relationship. Colonization was 16% (n = 4/25) in pets (75% MRSA—25% MSSA). The most frequent clonal complex was CC8 (15.6%), and the spa typing revealed high diversity.

Conclusion

This study shows a high frequency of colonization by S. aureus in both hemodialysis patients and their household contacts and a significant genetic relationship between their isolates. This demonstrates an exchange of this bacterium and that homes are an important source of colonization to patients, highlighting the need for prevention strategies outside the hospital to avoid future infections, and the importance of the populations with permanent transit between the two environments.

National Surveillance of Antimicrobial Susceptibility of Bacteremic Gram-Negative Bacteria with Emphasis on Community-Acquired Resistant Isolates: Report from the 2019 Surveillance of Multicenter Antimicrobial Resistance in Taiwan (SMART)

A multicenter collection of bacteremic isolates of Escherichia coli (n = 423), Klebsiella pneumoniae (n = 372), Pseudomonas aeruginosa (n = 300), and Acinetobacter baumannii complex (n = 199) was analyzed for susceptibility. Xpert Carba-R assay and sequencing for mcr genes were performed for carbapenem- or colistin-resistant isolates. Nineteen (67.8%) carbapenem-resistant K. pneumoniae (n = 28) and one (20%) carbapenem-resistant E. coli (n = 5) isolate harbored bla _KPC (n = 17), bla _OXA-48 (n = 2), and bla _VIM (n = 1) genes.

HOME2: Household vs. Personalized Decolonization in Households of Children with Methicillin-Resistant Staphylococcus aureus Skin and Soft Tissue Infection - A Randomized Clinical Trial

BACKGROUND

A household approach to decolonization decreases skin and soft tissue infection (SSTI) incidence, though this is burdensome and costly. As prior SSTI increases risk for SSTI, we hypothesized the effectiveness of decolonization measures to prevent SSTI when targeted to household members with prior year SSTI would be non-inferior to decolonizing all household members.

METHODS

Upon completion of our 12-month observational HOME study, 102 households were enrolled in HOME2, a 12-month, randomized non-inferiority trial. Pediatric index patients with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) SSTI, their household contacts, and pets were enrolled. Households were randomized 1:1 to the Personalized (decolonization performed only by household members who experienced SSTI during the HOME study) or Household (decolonization performed by all household members) approaches. The 5-day regimen included hygiene education, twice-daily intranasal mupirocin, and daily bleach-water baths. At 5 follow-up visits in participants' homes, swabs to detect S. aureus were collected from participants, environmental surfaces, and pets; incident SSTI were ascertained.

RESULTS

Non-inferiority of the Personalized Approach was established for the primary outcome 3-month cumulative SSTI: 23 of 212 (10.8%) participants reported SSTI in Household Approach households, while 23 of 236 (9.7%) participants reported SSTI in Personalized Approach households; difference in proportions -1.1% (95% CI -6.7%, 4.5%). In multivariable analyses, prior year SSTI and baseline MRSA colonization were associated with cumulative SSTI.

CONCLUSIONS

The Personalized Approach was non-inferior to the Household Approach in preventing SSTI. Future studies should interrogate longer durations of decolonization and/or decontamination of the household environment to reduce household MRSA burden.

Environmental Methicillin-resistant Staphylococcus aureus Contamination, Persistent Colonization, and Subsequent Skin and Soft Tissue Infection

IMPORTANCE

The longitudinal association among persistent Staphylococcus aureus colonization, household environmental contamination, and recurrent skin and soft tissue infection (SSTI) is largely unexplored to date.

OBJECTIVES

To identify factors associated with persistent S aureus colonization and recurrent SSTI in households with children with community-associated methicillin-resistant S aureus (MRSA) SSTI.

DESIGN, SETTING, AND PARTICIPANTS

This 12-month prospective cohort study included 150 children with community-associated MRSA SSTI, 542 household contacts, and 154 pets enrolled from January 3, 2012, through October 20, 2015. A total of 5 quarterly home visits were made to 150 households in the St Louis, Missouri, region. Statistical analysis was performed from September 18, 2018, to January 7, 2020.

EXPOSURES

Covariates used in S aureus strain persistence and interval SSTI models included S aureus colonization and contamination measures, personal hygiene and sharing habits, health history, activities external to the home, and household characteristics (eg, cleanliness, crowding, home ownership, and pets). Serial samples to detect S aureus were collected from household members at 3 anatomic sites, from pets at 2 anatomic sites, and from environmental surfaces at 21 sites.

MAIN OUTCOMES AND MEASURES

Molecular epidemiologic findings of S aureus isolates were assessed via repetitive-sequence polymerase chain reaction. Individual persistent colonization was defined as colonization by an identical strain for 2 consecutive samplings. Longitudinal, multivariable generalized mixed-effects logistic regression models were used to assess factors associated with persistent S aureus personal colonization, environmental contamination, and interval SSTI.

RESULTS

Among 692 household members in 150 households, 326 (47%) were male and 366 (53%) were female, with a median age of 14.82 years (range, 0.05-82.25 years). Of 540 participants completing all 5 samplings, 213 (39%) were persistently colonized with S aureus, most often in the nares and with the strain infecting the index patient at enrollment. Nine pets (8%) were persistently colonized with S aureus. Participants reporting interval intranasal mupirocin application were less likely to experience persistent colonization (odds ratio [OR], 0.44; 95% credible interval [CrI], 0.30-0.66), whereas increasing strain-specific environmental contamination pressure was associated with increased individual persistent colonization (OR, 1.17; 95% CrI, 1.06-1.30). Strains with higher colonization pressure (OR, 1.47; 95% CrI, 1.25-1.71) and MRSA strains (OR, 1.57; 95% CrI, 1.16-2.19) were more likely to persist. Seventy-six index patients (53%) and 101 household contacts (19%) reported interval SSTIs. Individuals persistently colonized with MRSA (OR, 1.56; 95% CrI, 1.17-2.11), those with a history of SSTI (OR, 2.55; 95% CrI, 1.88-3.47), and index patients (OR, 1.54; 95% CrI, 1.07-2.23) were more likely to report an interval SSTI.

CONCLUSIONS AND RELEVANCE

The study findings suggest that recurrent SSTI is associated with persistent MRSA colonization of household members and contamination of environmental surfaces. Future studies may elucidate the effectiveness of specific combinations of personal decolonization and environmental decontamination efforts in eradicating persistent strains and mitigating recurrent SSTIs.

Longitudinal, strain-specific Staphylococcus aureus introduction and transmission events in households of children with community-associated meticillin-resistant S aureus skin and soft tissue infection: a prospective cohort study

BACKGROUND

Devising effective, targeted approaches to prevent recurrent meticillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infection requires an understanding of factors driving MRSA acquisition. We comprehensively defined household longitudinal, strain-level S aureus transmission dynamics in households of children with community-associated MRSA skin and soft tissue infection.

METHODS

From 2012-15, otherwise healthy paediatric patients with culture-confirmed, community-onset MRSA infections were recruited for the Household Observation of MRSA in the Environment (HOME) prospective cohort study from hospitals and community practices in metropolitan St Louis (MO, USA). Children with health-care-related risk factors were excluded, as determined by evidence of recent hospital admission, an invasive medical device, or residence in a long-term care facility. Household contacts (individuals sleeping in the home ≥four nights per week) and indoor dogs and cats were also enrolled. A baseline visit took place at the index patient's primary home, followed by four quarterly visits over 12 months. At each visit, interviews were done and serial cultures were collected, to detect S aureus from three anatomic sites of household members, two anatomic sites on dogs and cats, and 21 environmental surfaces. Molecular typing was done by repetitive-sequence PCR to define distinct S aureus strains within each household. Longitudinal, multivariable generalised mixed-effects logistic regression models identified factors associated with S aureus acquisition.

FINDINGS

Across household members, pets, and environmental surfaces, 1267 strain acquisition events were observed. Acquisitions were driven equally by 510 introductions of novel strains into households and 602 transmissions within households, each associated with distinct factors. Frequent handwashing decreased the likelihood of novel strain introduction into the household (odds ratio [OR] 0·86, credible interval [CrI] 0·74-1·01). Transmission recipients were less likely to own their homes (OR 0·77, CrI 0·63-0·94) and were more likely to share bedrooms with strain-colonised individuals (OR 1·33, CrI 1·12-1·58), live in homes with higher environmental S aureus contamination burden (OR 3·97, CrI 1·96-8·20), and report interval skin and soft tissue infection (OR 1·32, CrI 1·07-1·64). Transmission sources were more likely to share bath towels (OR 1·25, CrI 1·01-1·57). Pets were often transmission recipients, but rarely the sole transmission source.

INTERPRETATION

The household environment plays a key role in transmission, a factor associated with skin and soft tissue infection. Future interventions should inclusively target household members and the environment, focusing on straightforward changes in hand hygiene and household sharing behaviours.

FUNDING

National Institutes of Health, Agency for Healthcare Research and Quality, Children's Discovery Institute, Burroughs Wellcome Foundation, Defense Advanced Research Projects Agency.

How the Pathologist Can Help the Surgeon Collect Better Specimens for Microbiology Culture

CONTEXT.—

Specimen quality is paramount for microbiology culture in order to ensure the testing is performed appropriately and the results, generated accurately, reflect the patient's clinical situation and guide proper treatment. Several factors play a critical role in guaranteeing the accuracy of the culture results, including adequate specimen collection by the surgeon, proper labeling, and timely transport to the laboratory.

OBJECTIVE.—

To educate pathologists, surgeons, and other medical personnel involved in the collection and processing of surgical specimens submitted for microbiologic culture. To assure the pathogen is correctly identified, proper protocols must be followed. The accurate identification of the infectious microorganisms from surgical specimens is vital for the treating clinician to ensure the correct antimicrobial therapy is administered.

DATA SOURCES.—

An analysis of relevant literature was performed by using PubMed. Articles were selected on the basis of their relevance to the topic as well as their date of publication. Articles published between 2000 and 2018 were deemed sufficient for inclusion, while older references, regardless of relevance, were excluded.

CONCLUSIONS.—

The process of properly obtaining specimens for microbiology culture from the operating room is a complex process that requires collaboration between the collecting surgeon and the pathologist and microbiology laboratory in order to provide the highest quality of results from which important treatment decisions are then implemented. Engaging leadership to develop mutually agreed-upon institutional best practices will help not only to standardize practices but also to improve the quality of microbiology results reported.

Prevalence and predictors of MRSA carriage among employees in a non-outbreak setting: a cross-sectional study in an acute care hospital

BACKGROUND

Health care workers have an increased risk of being infected with Methicillin-resistant Staphylococcus aureus (MRSA), though little information is available about how prevalent (dormant) MRSA colonization is among health care workers. The aim of this study was to estimate the prevalence and predictors of MRSA carriage in a non-outbreak setting in a university hospital in Germany.

METHODS

The entire staff of a university hospital heart center for cardiologic maximum medical care and cardiac surgery were invited to participate in a cross-sectional study (N = 575). The sampled population included health care workers as well as employees with no close patient contact.A questionnaire concerning personal and occupational risk factors as well as lifestyle and demographic factors was applied and nasal swabs were taken. In total 180 persons (31.3%) participated in the study.

RESULTS

The majority of study participants had close contact to patients at work (n = 149, 82.8%). Thereof, about one-third had contact to MRSA-patients (n = 53, 35.6%), and most reported wearing protective clothing (n = 44, 83.0%). None of the administrative staff tested positive for MRSA and only one in 149 persons (0.7%, CI 0.00-0.02) with close patient contact carried MRSA (strain CC1-MRSA-IV). This person had close contact to patients with MRSA, less than 1 year of work experience, and had been treated with antibiotics within the last 12 months.

CONCLUSION

The results of our study suggest low point prevalence rates of MRSA colonization in health care workers in a non-outbreak setting.

Interplay of personal, pet, and environmental colonization in households affected by community-associated methicillin-resistant Staphylococcus aureus

OBJECTIVE

We sought to determine the prevalence, molecular epidemiology, and factors associated with Staphylococcus aureus environmental surface and pet colonization in households of children with community-associated methicillin-resistant S. aureus (CA-MRSA) infection.

METHODS

Between 2012 and 2015, 150 children with CA-MRSA infections and their household contacts and pets were enrolled in this cross-sectional study in metropolitan Saint Louis, MO. Cultures to detect S. aureus were collected from 3 anatomic sites of household members, 2 dog/cat sites, and 21 environmental surfaces in each household. Molecular epidemiology of S. aureus isolates was determined via repetitive-sequence PCR. Generalized linear models were developed to identify factors associated with S. aureus/MRSA household contamination.

RESULTS

MRSA was recovered from environmental surfaces in 69 (46%) households (median 2 surfaces [range 1-18]). The enrollment infecting strain type was the most common strain recovered from the environment in most (64%) households. In generalized linear models, factors associated with a higher proportion of MRSA-contaminated environmental surfaces were household member MRSA colonization burden, MRSA as the dominant S. aureus strain colonizing household members, more strain types per household member, index case African-American race, and renting (vs. owning) the home. Of 132 pets, 14% were colonized with MRSA. Pets whose primary caretaker was MRSA-colonized were more likely to be MRSA-colonized than pets whose primary caretaker was not MRSA-colonized (50% vs. 4%, p < 0.001).

CONCLUSIONS

Household environments and pet dogs and cats serve as reservoirs of MRSA. Household member MRSA colonization burden predicts environmental MRSA contamination. Longitudinal studies will inform the directionality of household transmission.

The epidemiology and transmission of methicillin-resistant Staphylococcus aureus in the community in Singapore: study protocol for a longitudinal household study

BACKGROUND/AIM

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common multidrug-resistant organisms in healthcare settings worldwide, but little is known about MRSA transmission outside of acute healthcare settings especially in Asia. We describe the methods for a prospective longitudinal study of MRSA prevalence and transmission.

METHODS

MRSA-colonized individuals were identified from MRSA admission screening at two tertiary hospitals and recruited together with their household contacts. Participants submitted self-collected nasal, axilla and groin (NAG) swabs by mail for MRSA culture at baseline and monthly thereafter for 6 months. A comparison group of households of MRSA-negative patients provided swab samples at one time point. In a validation sub-study, separate swabs from each site were collected from randomly selected individuals, to compare MRSA detection rates between swab sites, and between samples collected by participants versus those collected by trained research staff. Information on each participant's demographic information, medical status and medical history, past healthcare facilities usage and contacts, and personal interactions with others were collected using a self-administered questionnaire.

DISCUSSION/CONCLUSION

Understanding the dynamics of MRSA persistence and transmission in the community is crucial to devising and evaluating successful MRSA control strategies. Close contact with MRSA colonized patients may to be important for MRSA persistence in the community; evidence from this study on the extent of community MRSA could inform the development of household- or community-based interventions to reduce MRSA colonization of close contacts and subsequent re-introduction of MRSA into healthcare settings. Analysis of longitudinal data using whole-genome sequencing will yield further information regarding MRSA transmission within households, with significant implications for MRSA infection control outside acute hospital settings.

Methodologic considerations of household-level methicillin-resistant Staphylococcus aureus decolonization among persons living with HIV

BACKGROUND

People living with HIV (PLWH) have a higher prevalence of methicillin-resistant Staphylococcus aureus (MRSA) colonization and likelihood of recurrent infection than the general population. Simultaneously treating MRSA-colonized household members may improve success with MRSA decolonization strategies. This article describes a pilot trial testing household-level MRSA decolonization and documents methodologic and pragmatic challenges of this approach.

METHODS

We conducted a randomized controlled trial of individual versus individual-plus-household MRSA decolonization to reduce recurrent MRSA. PLWH with a history of MRSA who are patients of an urban HIV clinic received a standard MRSA decolonization regimen. MRSA colonization at 6 months was the primary outcome.

RESULTS

One hundred sixty-six patients were referred for MRSA screening; 77 (46%) enrolled. Of those, 28 (36%) were colonized with MRSA and identified risk factors consistent with the published literature. Eighteen were randomized and 13 households completed the study.

CONCLUSIONS

This is the first study to report on a household-level MRSA decolonization among PLWH. Challenges included provider referral, HIV stigma, confidentiality concerns over enrolling households, and dynamic living situations. Although simultaneous household MRSA decolonization may reduce recolonization, recruitment and retention challenges specific to PLWH limit the ability to conduct household-level research. Efforts to minimize these barriers are needed to inform evidence-based practice.