Colonization with Staphylococcus aureus and methicillin-resistant S. aureus among a sample of homeless individuals, Ohio

Infectious Diseases Among People Experiencing Homelessness: A Systematic Review of the Literature in the United States and Canada, 2003-2022

Homelessness increases the risk of acquiring an infectious disease. We conducted a systematic review of the literature to identify quantitative data related to infectious diseases and homelessness. We searched Google Scholar, PubMed, and SCOPUS for quantitative literature published from January 2003 through December 2022 in English from the United States and Canada. We excluded literature on vaccine-preventable diseases and HIV because these diseases were recently reviewed. Of the 250 articles that met inclusion criteria, more than half were on hepatitis C virus or Mycobacterium tuberculosis. Other articles were on COVID-19, respiratory syncytial virus, Staphylococcus aureus, group A Streptococcus, mpox (formerly monkeypox), 5 sexually transmitted infections, and gastrointestinal or vectorborne pathogens. Most studies showed higher prevalence, incidence, or measures of risk for infectious diseases among people experiencing homelessness as compared with people who are housed or the general population. Although having increased published data that quantify the infectious disease risks of homelessness is encouraging, many pathogens that are known to affect people globally who are not housed have not been evaluated in the United States or Canada. Future studies should focus on additional pathogens and factors leading to a disproportionately high incidence and prevalence of infectious diseases among people experiencing homelessness.

Community-acquired Staphylococcus aureus skin and soft tissue infection risk assessment using hotspot analysis and risk maps: the case of California emergency departments

BACKGROUND

Community-acquired Staphylococcus aureus (CA-Sa) skin and soft tissue infections (SSTIs) are historically associated with densely populated urban areas experiencing high poverty rates, intravenous drug use, and homelessness. However, the epidemiology of CA-Sa SSTIs in the United States has been poorly understood since the plateau of the Community-acquired Methicillin-resistant Staphylococcus aureus epidemic in 2010. This study examines the spatial variation of CA-Sa SSTIs in a large, geographically heterogeneous population and identifies neighborhood characteristics associated with increased infection risk.

METHODS

Using a unique neighborhood boundary, California Medical Service Study Areas, a hotspot analysis, and estimates of neighborhood infection risk ratios were conducted for all CA-Sa SSTIs presented in non-Federal California emergency departments between 2016 and 2019. A Bayesian Poisson regression model evaluated the association between neighborhood-level infection risk and population structure, neighborhood poverty rates, and being a healthcare shortage area.

RESULTS

Emergency departments in more rural and mountainous parts of California experienced a higher burden of CA-Sa SSTIs between 2016 and 2019. Neighborhoods with high infection rates were more likely to have a high percentage of adults living below the federal poverty level and be a designated healthcare shortage area. Measures of population structure were not associated with infection risk in California neighborhoods.

CONCLUSIONS

Our results highlight a potential change in the epidemiology of CA-Sa SSTIs in California emergency departments. Future studies should investigate the CA-Sa burden in other geographies to identify whether this shift in epidemiology holds across other states and populations. Further, a more thorough evaluation of potential mechanisms for the clustering of infections seen across California neighborhoods is needed.

Frequent Methicillin-Resistant Staphylococcus aureus Introductions Into an Inner-city Jail: Indications of Community Transmission Networks

BACKGROUND

Jails may facilitate spread of methicillin-resistant Staphylococcus aureus (MRSA) in urban areas. We examined MRSA colonization upon entrance to a large urban jail to determine if there are MRSA transmission networks preceding incarceration.

METHODS

Males incarcerated in Cook County Jail (Chicago) were enrolled, with enrichment for people living with human immunodeficiency virus (PLHIV), within 72 hours of intake. Surveillance cultures assessed prevalence of MRSA colonization. Whole-genome sequencing (WGS) identified preincarceration transmission networks.We examined methicillin-resistant Staphylococcus aureus (MRSA) isolates to determine if there are transmission networks that precede incarceration. A large proportion of individuals enter jail colonized with MRSA. Molecular epidemiology and colonization risk factors provide clues to community reservoirs for MRSA.

RESULTS

There were 718 individuals (800 incarcerations) enrolled; 58% were PLHIV. The prevalence of MRSA colonization at intake was 19%. In multivariate analysis, methamphetamine use, unstable housing, current/recent skin infection, and recent injection drug use were predictors of MRSA. Among PLHIV, recent injection drug use, current skin infection, and HIV care at outpatient clinic A that emphasizes comprehensive care to the lesbian, gay, bisexual, transgender community were predictors of MRSA. Fourteen (45%) of 31 detainees with care at clinic A had colonization. WGS revealed that this prevalence was not due to clonal spread in clinic but rather to an intermingling of distinct community transmission networks. In contrast, genomic analysis supported spread of USA500 strains within a network. Members of this USA500 network were more likely to be PLHIV (P < .01), men who have sex with men (P < .001), and methamphetamine users (P < .001).

CONCLUSIONS

A large proportion of individuals enter jail colonized with MRSA. Molecular epidemiology and colonization risk factors provide clues to identify colonized detainees entering jail and potential community reservoirs of MRSA.

Methicillin Resistant Staphylococcus aureus and public fomites: a review

Staphylococcus genus is a Gram-positive coccus normally associated with skin and mucous membranes of warm-blooded animals. It is part of the commensal human microflora, or found in animals, or contaminating surfaces in the community and hospital settings. Staphylococcus aureus is the most pathogenic species belonging to this genus, as it possesses a collection of virulence factors that are expressed solely to evade the immune system. The increase in the misuse of antimicrobial agents predisposed S. aureus to develop antibiotic resistance, including the resistance to methicillin which led to the emergence of Methicillin-Resistant S. aureus (MRSA). MRSA is considered one of the most dangerous nosocomial pathogens causing many hard to treat infections in hospitals and was named as Hospital Associated MRSA (HA-MRSA). Over the past 20-25 years, MRSA was isolated from community settings and thus Community Associated MRSA (CA-MRSA) has emerged. Inside hospitals, MRSA has been isolated from fomites in contact with patients, as well as staff's protective and personal items. This review highlights the worldwide prevalence of MRSA on fomites within the contexts of hospital and community settings.

The Homelessness Crisis and Burn Injuries: A Cohort Study

The United States is facing a growing homelessness crisis. We characterize the demographics and outcomes of homeless patients who sustain burn injury and compare them to a cohort of domiciled patients. A retrospective cohort study was performed at the Los Angeles County + University of Southern California Regional Burn Center for consecutive acute burn admissions in adults from June 1, 2015, to December 31, 2018. Patients were categorized as either domiciled or homeless at the time of their injury. Prevalence rates were estimated using data from the regional homeless count. From 881 admissions, 751 (85%) had stable housing and 130 (15%) were homeless. The rate of burn injury requiring hospitalization for homeless adults was estimated at 88 per 100,000 persons. Homeless patients had a significantly larger median burn size (7 vs 5%, P < .05) and a greater rate of flame burns (68 vs 42%, P < .001). For the homeless, rates of assault and self-inflicted injury were 4- (18 vs 4%, P < .001) and 2-fold higher (9 vs 4%, P < .001), respectively. Homeless patients had higher rates of mental illness (32 vs 12%, P < .001) and substance abuse (88 vs 22%, P < .001), and were less likely to follow-up as outpatients (54 vs 87%, P < .001). There was no difference in mortality. Homeless patients had a longer median length of stay (LOS; 11 vs 7 days, P < .001) without significant differences in LOS per percentage TBSA. Homeless individuals should be considered a high-risk population for burn injury. This distinction serves as a call to action for the development of burn prevention strategies.

Intersection of HIV and community-associated methicillin-resistant Staphylococcus aureus

The epidemiology of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has evolved over the past approximately 20 years, with certain populations appearing to have disproportionate risk. Of concern is the potential worsening of S. aureus infections in light of the continued opioid crisis. This review will discuss how CA-MRSA has significantly impacted HIV-infected individuals and address additional factors and populations that are associated with increased risk for MRSA. It will review therapeutic options and infection control strategies as well as highlight how whole genome sequencing can be used to extend traditional epidemiologic analysis and ultimately, inform infection prevention efforts. Continued work identifying those at the highest risk for MRSA, what the best infection prevention settings are in community settings and how to effectively implement and target these strategies is needed. Ultimately, infection control efforts will likely need to extend beyond healthcare settings to effectively and sustainably reduce MRSA infections.

Homelessness, Personal Hygiene, and MRSA Nasal Colonization among Persons Who Inject Drugs

Methicillin-resistant Staphylococcus aureus (MRSA) infection is a leading cause of hospitalization and medical visits among individuals experiencing homelessness and also among persons who inject drugs (PWID), populations with significant overlap in urban centers in the USA. While injection drug use is a risk factor for MRSA skin infections, MRSA is also known to transmit easily in crowded, public locations in which individuals have reduced personal hygiene. Individuals in urban centers who experience homelessness or drug addiction may spend significant amounts of time in environments where MRSA can be easily transmitted, and may also experience reduced access to facilities to maintain personal hygiene. We assessed the relationship between homelessness, personal hygiene, and MRSA nasal colonization, a proxy for MRSA infection risk, in a study of PWID in Boston, MA (n = 78). Sleeping in a homeless shelter for at least one night in the last 3 months was significantly associated with MRSA nasal colonization (OR 3.0; p = 0.02; 95% CI 1.2, 7.6). Sleeping at more than one place during the last week (considered a metric of elevated housing instability) was also associated with a threefold increase in odds of MRSA nasal colonization (OR 3.1; p = 0.01; 95% CI 1.3, 7.6). MRSA nasal colonization was strongly associated with use of public showers (OR 13.7; p = 0.02; 95% CI 1.4, 132.8), although few people in this study (4 of 78) reported using these public facilities. Sharing bedding with other people was also associated with increased risk of MRSA colonization (OR 2.2; p = 0.05; 95% CI 1.0-4.7). No associations between hand hygiene, frequency of bathing or clothes laundering, or street sleeping were observed. Use of public facilities supporting persons experiencing homelessness and housing instability, including shelters and public showers, is associated with an increased risk of MRSA nasal colonization in this study. Personal hygiene behaviors appear less associated with MRSA nasal colonization. Environmental assessments of MRSA contamination in homeless shelters and public sanitation facilities are warranted so as to inform appropriate intervention activities.

Staphylococcus aureus nasal carriage among homeless population in Lisbon, Portugal

Methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage is a major risk factor for infection, namely among populations in the community with inherent prompting factors, such as the homeless. In Portugal, there are no data on S. aureus/MRSA nasal carriage among the homeless community. A total of 84 homeless individuals living in Lisbon (34 with no permanent address and 50 living in shelter) were nasally screened for S. aureus/ MRSA. All isolates were characterized to determine antimicrobial susceptibility and clonal type. A total of 43 (51.2%) S. aureus carriers were identified, including a single individual colonized with MRSA (1.2%). S. aureus carriage rate was higher among individuals with no permanent address (58.8% versus 46%), younger (45.7 ± 12.7 versus 52.5 ± 10.8 years), and with diagnosis of asthma (9% versus 0%). The single MRSA belonged to the EMRSA-15 clone (PFGE D, ST15-SCCmec IVh, and spa type t790). Almost half of the methicillin-susceptible S. aureus (MSSA) isolates (41.9%, n = 18) belonged to two major clones, ST398-t1451 (n = 13) and ST30-t399/t11980/t12808 associated with PFGE I (n = 5). A high proportion of isolates showed non-susceptibility to mupirocin (64%), erythromycin (45%), and fusidic acid (20%) and induced resistance to clindamycin (39%). None of the isolates harboured PVL. Our results suggest that the homeless population of Lisbon does not constitute a reservoir of MRSA in the community, but harbour the highly transmissible ST398-t1451 MSSA lineage.

Prevalence and risk factors for MRSA nasal colonization among persons experiencing homelessness in Boston, MA

Homeless individuals face an elevated risk of methicillin-resistant Staphylococcus aureus (MRSA) infection. Identifying the prevalence and risk factors for MRSA nasal colonization may reduce infection risk. A cross-sectional study was conducted at a health clinic for homeless persons in Boston, MA, USA (n=194). In-person interviews and nasal swab specimens were collected. MRSA isolates were genotyped using pulse-field gel electrophoresis (PFGE) and assessed for antibiotic susceptibility. The prevalence of MRSA nasal colonization was 8.3 %. Seventy-five percent of isolates reflected clonal similarity to USA300. USA100 (18.8 %) and USA500 (6.3 %) were also recovered. Resistance to erythromycin (81.3 %), levofloxacin (31.3 %) and clindamycin (23.1 %) was identified. Recent inpatient status, endocarditis, haemodialysis, heavy drinking, not showering daily and transience were positively associated with MRSA nasal colonization. Carriage of community-acquired MRSA strains predominated in this population, although nosocomial strains co-circulate. Attention to behavioural and hygiene-related risk factors, not typically included in MRSA prevention efforts, may reduce risk.

Joint replacement surgery in homeless veterans

Total joint arthroplasty (TJA) in a homeless patient is generally considered contraindicated. Here, we report our known medical and social (housing and employment) results of homeless veterans who had TJA. Thirty-seven TJAs were performed on 33 homeless patients (31 men) at our hospital between November 2000 and March 2014. This was 1.2% of all TJAs. Average age was 54 years. Average hospital stay was 4.1 days. There were no major inpatient complications. Thirty-four cases had at least 1-year follow-up in any clinic within the Veterans Affairs health care system. There were no known surgery-related reoperations or readmissions. At final follow-up, 24 patients had stable housing and 9 were employed. The extensive and coordinated medical and social services that were provided to veterans from the Department of Veterans Affairs contributed to our positive results.

Prevalence of Nasal Colonization by Methicillin-Resistant Staphylococcus aureus in Persons Using a Homeless Shelter in Kansas City

Nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA) plays an important role in the epidemiology and pathogenesis of disease. Situations of close-quarter contact in groups are generally regarded as a risk factor for community-acquired MRSA strains due to transmission via fomites and person-to-person contact. With these criteria for risk, homeless individuals using shelter facilities, including showers and toilets, should be considered high risk for colonization and infection. The aim of this study was to determine the prevalence of nasal colonization of MRSA in a homeless population compared to established rates of colonization within the public and a control group of subjects from a neighboring medical school campus, and to analyze phylogenetic diversity among the MRSA strains. Nasal samples were taken from the study population of 332 adult participants and analyzed. In addition, participants were surveyed about various lifestyle factors in order to elucidate potential patterns of behavior associated with MRSA colonization. Homeless and control groups both had higher prevalence of MRSA (9.8 and 10.6%, respectively), when compared to the general population reported by previous studies (1.8%). However, the control group had a similar MRSA rate compared to health-care workers (4.6%), while the homeless population had an increased prevalence. Risk factors identified in this study included male gender, age over 50 years, and use of antibiotics within the past 3 months. Phylogenetic relationships between nine of the positive samples from the homeless population were analyzed, showing eight of the nine samples had a high degree of relatedness between the spaA genes of the MRSA strains. This indicates that the same MRSA strain might be transmitted from person-to-person among homeless population. These findings increase our understanding of key differences in MRSA characteristics within homeless populations, as well as risks for MRSA associated with being homeless, such as age and gender, which may then be a useful tool in guiding more effective prevention, treatment, and health care for homeless individuals.

Genomic Epidemiology of USA300 Methicillin-Resistant Staphylococcus aureus in an Urban Community

BACKGROUND

In a community, it is unknown what factors account for transmission of methicillin-resistant Staphylococcus aureus (MRSA). We integrated whole genome sequencing (WGS) and epidemiologic data to identify factors associated with MRSA transmission networks in an urban community.

METHODS

WGS was performed on colonizing USA300 MRSA isolates from 74 individuals within 72 hours of admission to a public hospital in Chicago, IL. Single nucleotide variants (SNVs) were used to reconstruct the phylogeny of sequenced isolates, and epidemiologic data was overlaid to identify factors associated with transmission networks.

RESULTS

The maximum within-patient SNV difference for an individual with multisite colonization was 41 SNVs, with no systematic divergence among body sites. We observed a minimum of 7 SNVs and maximum of 153 SNVs between isolates from different individuals. We identified 4 pairs of individuals whose isolates were within 40 SNVs of each other. Putting our isolates in the context of previously sequenced USA300 isolates from other communities, we identified a 13-member group and two 4-member groups that represent samples from putative local transmission networks. Individuals in these groups were more likely to be African American, to be human immunodeficiency virus-infected, to reside in high detainee release areas, and to be current users of illicit drugs.

CONCLUSIONS

Using WGS, we observed potential transmission networks in an urban community and that certain epidemiologic factors were associated with inclusion in these networks. Future work with contact tracing and advanced molecular diagnostics may allow for identification of MRSA "epicenters" in the community where interventions can be targeted.

Community-associated methicillin-resistant Staphylococcus aureus colonization burden in HIV-infected patients

BACKGROUND

The epidemic of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has had a disproportionate impact on patients with human immunodeficiency virus (HIV).

METHODS

We evaluated CA-MRSA colonization burden (number of colonized sites per total number sampled) among HIV-infected and HIV-negative inpatients within 72 hours of hospitalization. From March 2011 through April 2012, we obtained cultures from nasal and extranasal sites (throat, axilla, inguinal, perirectal, and chronic wound if present) and collected risk factor data.

RESULTS

Of 745 patients (374 HIV-infected, 371 HIV-negative), 15.7% were colonized with CA-MRSA at any site: 20% of HIV and 11% of HIV-negative patients (relative prevalence=1.8, P=.002). HIV-infected patients had a higher prevalence of nasal, extranasal, and exclusive extranasal colonization as well as higher colonization burden. Perirectal and inguinal areas were the extranasal sites most frequently colonized, and 38.5% of colonized patients had exclusive extranasal colonization. Seventy-three percent of isolates were identified as USA300. Among HIV-infected patients, male sex, younger age, and recent incarceration were positively associated whereas Hispanic ethnicity was negatively associated with higher colonization burden. Among HIV-negative patients, temporary housing (homeless, shelter, or substance abuse center) was the only factor associated with higher colonization burden. Predictors of USA300 included HIV, younger age, illicit drug use, and male sex; all but 1 colonized individual with current or recent incarceration carried USA300.

CONCLUSIONS

HIV-infected patients were more likely to have a higher CA-MRSA colonization burden and carry USA300. In certain populations, enhanced community and outpatient-based infection control strategies may be needed to prevent CA-MRSA cross-transmission and infection.

Revisiting Methicillin-Resistant Staphylococcus aureus Infections

Within less than 50 years, methicillin-resistant Staphylococcus aureus (MRSA) made a tremendous impact worldwide. It is not limited to medical facilities and healthcare institutions anymore. Indeed since two decades, cases of MRSA infections arising from the community among apparently healthy individuals are increasing. In this paper, I will present a case of community-associated MRSA sepsis followed by a comprehensive review about the history, pathogenesis, epidemiology, clinical presentations, diagnostic modalities, therapeutic options, contributing factors, growing cost and other pertinent elements of this newly evolving epidemic of MRSA infections.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic

Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.