Association Between Homelessness and Group A Streptococcus Skin and Soft Tissue Infections Among Hospitalized Dermatology Consult Patients

Skin and soft tissue infections (SSTIs) are common among persons experiencing homelessness (PEH).¹ While studies have investigated higher rates of methicillin-resistant Staphylococcus aureus (MRSA) SSTIs among PEH,² group A Streptococcus (GAS) also causes SSTIs and requires different first-line antibiotic coverage.³ Given reports of invasive GAS outbreaks among PEH,^4-6 we evaluated the association between homelessness and GAS SSTIs.

We performed a retrospective, cross-sectional analysis of inpatients seen by the dermatology consult services at University of California, San Francisco, Moffitt-Long Hospital or Zuckerberg San Francisco General Hospital between March 2018 and March 2020 for SSTI with test-positive bacterial skin cultures. We collected data through patient chart review. Housing status was dichotomized, with patients classified as homeless if they reported no primary address or an institutional primary address within the past 12 months. Monomicrobial and polymicrobial culture results were included. Racial and ethnic categorization (Asian, Black, White, other) was based on patient self-identification. Other racial and ethnic group information collected included patients self-identifying as American Indian, Alaska Native, Native Hawaiian, other Pacific Islander, or 2 or more races or ethnicities. The University of California, San Francisco, institutional review board approved this study, waiving patient informed consent for use of de-identified data.

To quantify referring clinicians’ therapeutic practices, rates of first-line antibiotic coverage against GAS (beta-lactam antibiotics) or MRSA (vancomycin, doxycycline, linezolid, daptomycin, trimethoprim-sulfamethoxazole) were compared between housing groups using χ² testing. We determined associations between housing status (primary predictor) and both GAS SSTI (primary outcome) and MRSA SSTI (secondary outcome) in logistic regression after controlling for confounders identified through literature review, including age, gender, race, ethnicity, alcohol use disorder, and injection drug use. P < .05 was considered statistically significant.

Among 239 patients with SSTI, 181 with microbiology data were included (age 51.9 [SD 19.8] years; 70 [39%] female patients; 52 [29%] PEH) (Table 1). Persons experiencing homelessness had significantly higher rates of ecthyma (21% [95% CI, 10%-32%] vs 3% [95% CI, 0.1%-6%]; P = .001) and ectoparasitic disease (8% [95% CI, 0.4%-15%] vs 0.8% [95% CI, 0%-2%]; P = .01) (Table 2). At the time of dermatology consultation, PEH had significantly higher rates of first-line MRSA coverage (91% [95% CI, 82%-99%] vs 70% [95% CI, 61%-80%]; P = .008) and nonsignificantly reduced rates of first-line GAS coverage (30% [95% CI, 16%-43%] vs 47% [95% CI, 37%-58%]; P = .05).

Among PEH, 42% (95% CI, 29%-57%) had GAS-positive cultures and 33% (95% CI, 20%-47%) had MRSA-positive cultures. Among patients with stable housing, 15% (95% CI, 9%-22%) had GAS-positive cultures and 23% (95% CI, 16%-32%) had MRSA-positive cultures. Prior to adjustment, PEH had significantly higher odds of GAS SSTI (OR, 4.25 [95% CI, 2.04-8.85]; P < .001) and nonsignificantly higher odds of MRSA SSTI (OR, 1.60 [95% CI, 0.79-3.26]; P = .19) relative to patients with stable housing. After controlling for confounders, PEH had significantly higher odds of GAS SSTI (OR, 4.25 [95% CI, 1.86-9.70]; P = .001) and nonsignificantly higher odds of MRSA SSTI (OR, 1.49 [95% CI, 0.68-3.27]; P = .33).

Our finding that PEH were more likely to have first-line MRSA coverage suggests that health care professionals may prioritize MRSA among PEH presenting with SSTI. Given that 42% of PEH had cultures that tested positive for GAS and PEH had 4.25 times higher odds of GAS SSTI, the present study results suggest that health care professionals may need to consider GAS more strongly among PEH presenting with SSTI.

This study has several limitations. First, we were unable to differentiate between purulent and non-purulent forms of SSTI and cannot confirm that purulent SSTIs were uniformly overrepresented. Second, GAS SSTIs excluded owing to lack of microbiologic data could be differential between the 2 groups. Third, our cohort likely had more severe skin disease relative to outpatients with SSTI or inpatients with SSTI managed without dermatology.

In summary, we found that homelessness was independently associated with GAS SSTI in our study population. Future studies are needed to demonstrate causation, establish a more precise effect size estimate, and evaluate outcomes among PEH receiving empirical GAS coverage for SSTI.

Accepted for Publication: December 10, 2021.

Published Online: February 9, 2022. doi:10.1001/jamadermatol.2021.5845

Corresponding Author: Aileen Chang, MD, 995 Potrero Ave, Bldg 90, Ward 92, San Francisco, CA 94110 (aileen.chang@ucsf.edu).

Author Contributions: Mr Zakaria and Dr Chang had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Zakaria, Abuabara, Fox, Amerson, Chang.

Acquisition, analysis, or interpretation of data: Zakaria, Abuabara, Szumowski, Kim-Lim, Amerson, Chang.

Drafting of the manuscript: Zakaria.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Zakaria, Abuabara, Kim-Lim.

Administrative, technical, or material support: Zakaria, Kim-Lim, Chang.

Supervision: Abuabara, Fox, Amerson, Chang.

Conflict of Interest Disclosures: Mr Zakaria reported funding from the National Institutes of Health. Dr Chang is supported by the Dermatology Foundation Public Health Career Development Award. Dr Abuabara reported research funding from Pfizer and Cosmetique Active International SNC to her institution and personal fees from Target RWE outside the submitted work. No other disclosures were reported.

Funding/Support: This work was supported by the Dermatology Foundation (Dr Chang).

Role of the Funder/Sponsor: The Dermatology Foundation had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Disclaimer: Aileen Y. Chang is the Viewpoints Editor of JAMA Dermatology, but she was not involved in any of the decisions regarding review of the manuscript or its acceptance.