Homelessness Independently Associated with Group A Streptococcus Skin and Soft Tissue Infections

Katrina Abuabara, MD

A recent investigation found that homelessness was independently associated with group A Streptococcus (GAS) skin and soft tissue infections (SSTI).

Previous studies reported that skin and soft tissue infections were common among the homeless population, some of which suggested higher rates of methicillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections.

However, GAS outbreaks have been reported among persons experiencing homelessness, which inspired investigators led by Katrina Abuabara, MD, Department of Dermatology at the University of California to evaluate the association.

The Methods

The team conducted a retrospective, cross-sectional analysis of inpatients seen by the dermatology consult services of University of California, San Francisco, Moffitt-Long Hospital or Zuckerberg San Francisco General Hospital between March 2018 and March 2020.

Data from patuent chart reviews were collected and 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.

Racial and ethnic categorization (Asian, Black, White, other) was based on patient self-identification.

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.

Investigators also determined associations between housing status and GAS SSTI (primary outcome) and MRSA SSTI (secondary outcome) through logistic regression after controlling for confounders identified through literature reviews including age, gender, race, ethnicity, alcohol use disorder, and injection drug use.

The Findings

Among the 239 patients with soft skin and tissue infections included in the study, 181 patients with microbiology data were included. The mean age of patients with skin and soft tissue infections was 51.9 ([SD 19.8] years; 70 [39%] female patients; 52 [29%] PEH).

Investigators observed that 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)

During the dermatology consultation, persons experiencing homelessness had significantly higher rates of first-line MRSA coverage (91% [95% CI, 82%-99%] vs 70% [95% CI, 61%-80%]; P = .008) and non-significantly reduced rates of first-line GAS coverage (30% [95% CI, 16%-43%] vs 47% [95% CI, 37%-58%]; P = .05).

Among the participants, 42% (95% CI, 29%-57%) had GAS-positive cultures and 33% (95% CI, 20%-47%) had MRSA-positive cultures.

Among those with stable housing, 15% (95% CI, 9%-22%) had GAS-positive cultures and 23% (95% CI, 16%-32%) had MRSA-positive cultures.

Furthermore, persons experiencing homelessness had significantly higher odds of GAS skin and soft tissue infections (OR, 4.25 [95% CI, 2.04-8.85]; P < .001) and non-significantly higher odds of MRSA skin and soft tissue infections (OR, 1.60 [95% CI, 0.79-3.26]; P = .19) relative to patients with stable housing prior to adjustment.

After controlling for confounders, persons experiencing homelessness had significantly higher odds of GAS skin and soft tissue infections (OR, 4.25 [95% CI, 1.86-9.70]; P = .001).

The investigative team concluded that homelessness was independently associated with GAS skin and soft tissue infections.

“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,” the team wrote.

The study, "Association Between Homelessness and Group A Streptococcus Skin and Soft Tissue Infections Among Hospitalized Dermatology Consult Patients," was published online in JAMA Dermatology.