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Table 5 Risk factors for S. aureus and methicillin-resistant S. aureus skin and soft tissue infection episodes, Kaiser Permanente of Northern California, 2009-2011 a

From: Incidence, microbiology, and patient characteristics of skin and soft-tissue infections in a U.S. population: a retrospective population-based study

  Adjusted odds ratio (95% CI)b
  Among all episodes with a culture (n = 108243)c Among episodes positive for S. aureus(n = 47518)d
Characteristic Odds of S. aureusvs. not S. aureus Odds of MRSA vs. MSSA
Gender   
  Female 0.86 (0.84,0.88) 1.04 (1.00,1.09)
  Male ref ref
Age (years)   
  Under 5 3.89 (3.64,4.14) 1.28 (1.17,1.40)
  5- < 18 2.64 (2.52,2.78) 0.79 (0.73,0.85)
  18- < 50 1.91 (1.83,1.98) 1.11 (1.04,1.18)
  50- < 65 1.40 (1.34,1.46) 1.03 (0.96,1.10)
  65+ ref ref
Race/Ethnicity   
  Asian 1.02 (0.98,1.06) 0.73 (0.68,0.78)
  African-American 1.02 (0.98,1.07) 1.79 (1.67,1.92)
  Hispanic 1.05 (1.01,1.08) 1.24 (1.18,1.31)
  Native American 1.11 (0.95,1.30) 1.16 (0.92,1.46)
  Multiracial 0.95 (0.89,1.02) 1.01 (0.91,1.13)
  White ref ref
Diabetes status   
  Diabetes 0.93 (0.90,0.97) 0.75 (0.71,0.80)
  No diabetes ref ref
Census Block Income Quintile   
  Unknown 1.16 (1.10,1.23) 1.27 (1.17,1.38)
  1st (lowest income) 1.17 (1.12,1.22) 1.42 (1.33,1.51)
  2nd 1.13 (1.09,1.18) 1.25 (1.17,1.34)
  3rd 1.08 (1.03,1.12) 1.15 (1.08,1.22)
  4th 1.02 (0.98,1.07) 1.12 (1.05,1.20)
  5th (highest income) ref ref
Type of SSTI   
  Carbuncle and furuncle 1.33 (1.26,1.40) 1.22 (1.14,1.30)
  Impetigo 1.03 (0.97,1.09) 0.16 (0.14,0.18)
  Other infections of the skin 1.06 (1.00,1.11) 0.55 (0.51,0.59)
  Folliculitis 0.87 (0.83,0.91) 0.50 (0.46,0.53)
  Other SSTI 0.48 (0.42,0.53) 0.68 (0.56,0.82)
  Cellulitis and abscess ref ref
  1. a CI = 95% confidence interval; MSSA = methicillin-sensitive S. aureus; MRSA = methicillin-resistant S. aureus; ref = reference group for other odds ratios within characteristic.
  2. bOdds ratios estimated using multivariate logistic regression. A separate model was run for each column in the table. For both models the independent variables were gender, age, race/ethnicity, diabetes status, income quintile based on census block, and type of SSTI.
  3. c The analytic dataset had one record per SSTI episode with a microbiologic test, and the dependent variable was whether or not the test was positive for S. aureus. Specimens may have been positive for other organisms or no organism may have been identified. Episodes without a microbiologic test were not included in the model.
  4. d The analytic dataset had a record for each SSTI episode that tested positive for S. aureus. The dependent variable was whether or not the isolate was methicillin-resistant.