Table 2.
Associations of demographic and clinical characteristics with MRSA and SSTI case status compared to controls, in multinomial and binomial logistic regression models, respectivelya
| Characteristic | HA-MRSA | CA-MRSA | SSTI | |||
|---|---|---|---|---|---|---|
| Crude OR (95% CI) | Adjusted ORb (95% CI) | Crude OR (95% CI) | Adjusted OR (95% CI) | Crude OR (95% CI) | Adjusted OR (95% CI) | |
| Male sex | 1·1 (1·0–1·2) | 1·0 (0·9–1·2) | 0·9 (0·8–1·0) | 0·9 (0·8–1·0) | 1·0 (0·9–1·1) | 1·0 (0·9–1·1) |
| Age in years at infection or visit | ||||||
| <7 | 0·5 (0·4–0·7) | 0·8 (0·6–1·0) | 1·6 (1·3–1·9) | 1·9 (1·6–2·4) | 1·0 (0·8–1·2) | 1·3 (1·1–1·5) |
| 7 to <19 | 0·3 (0·2–0·4) | 0·4 (0·3–0·5) | 1·9 (1·6–2·4) | 2·3 (1·9–2·8) | 1·0 (0·8–1·2) | 1·2 (1·0–1·5) |
| 19 to <46 | 0·6 (0·5–0·7) | 0·6 (0·5–0·7) | 1·6 (1·3–1·9) | 1·6 (1·3–1·9) | 1·0 (0·9–1·2) | 1·0 (0·9–1·2) |
| 46 to <62 | Reference | Reference | Reference | Reference | Reference | Reference |
| 62 to <75 | 1·2 (0·9–1·4) | 1·2 (1·0–1·5) | 0·6 (0·4–0·7) | 0·6 (0·4–0·7) | 0·9 (0·8–1·1) | 1·0 (0·8–1·2) |
| ⩾75 | 1·7 (1·4–2·0) | 2·0 (1·7–2·4) | 0·4 (0·3–0·5) | 0·4 (0·3–0·6) | 1·1 (0·9–1·3) | 1·2 (1·0–1·5) |
| Race/ethnicity | ||||||
| Whitec | Reference | Reference | Reference | Reference | Reference | Reference |
| Black | 0·9 (0·6–1·5) | 1·4 (0·9–2·2) | 1·6 (1·1–2·4) | 1·3 (0·9–1·8) | 0·8 (0·5–1·1) | 0·8 (0·5–1·1) |
| Hispanic | 0·5 (0·3–0·9) | 0·8 (0·4–1·4) | 1·1 (0·7–1·7) | 0·8 (0·5–1·3) | 0·9 (0·7–1·4) | 1·0 (0·7–1·4) |
| Other | 0·6 (0·3–1·1) | 0·9 (0·5–1·8) | 0·6 (0·3–1·1) | 0·5 (0·3–1·0) | 0·6 (0·4–1·0) | 0·7 (0·4–1·1) |
| Adult BMId | ||||||
| Normal | Reference | Reference | Reference | Reference | Reference | Reference |
| Overweight | 0·6 (0·5–0·8) | 0·6 (0·5–0·8) | 0·8 (0·6–0·9) | 1·0 (0·8–1·2) | 1·7 (1·2–2·2) | 1·5 (1·1–2·1) |
| Obese | 1·3 (1·1–1·5) | 1·1 (0·9–1·3) | 1·3 (1·1–1·5) | 1·3 (1·1–1·6) | 1·8 (1·3–2·4) | 1·7 (1·2–2·3) |
| Child BMIe | ||||||
| Normal | Reference | Reference | Reference | Reference | Reference | Reference |
| Overweight | 0·8 (0·4–1·4) | 1·0 (0·5–1·8) | 1·4 (1·0–1·9) | 1·5 (1·1–2·1) | 1·2 (0·9–1·6) | 1·2 (0·9–1·7) |
| Obese | 2·2 (1·3–3·6) | 2·2 (1·3–3·8) | 1·5 (1·1–2·0) | 1·6 (1·2–2·3) | 1·4 (1·0–1·8) | 1·4 (1·0–1·9) |
| Smoking | ||||||
| Ever | 4·0 (3·4–4·7) | 3·9 (3·3–3·6) | 2·0 (1·6–2·3) | 2·4 (2·0–2·8) | 2·4 (2·0–2·7) | 2·4 (2·2–3·0) |
| Seasonf | ||||||
| Winter | Reference | Reference | Reference | Reference | Reference | Reference |
| Spring | 1·0 (0·8–1·2) | 1·0 (0·8–1·2) | 0·9 (0·7–1·0) | 0·9 (0·7–1·1) | 1·1 (0·9–1·2) | 1·1 (0·9–1·2) |
| Summer | 1·2 (1·0–1·4) | 1·3 (1·1–1·5) | 1·4 (1·2–1·6) | 1·3 (1·1–1·6) | 1·4 (1·2–1·6) | 1·4 (1·2–1·6) |
| Autumn | 1·2 (1·0–1·4) | 1·2 (1·0–1·4) | 1·5 (1·3–1·8) | 1·5 (1·3–1·8) | 1·2 (1·0–1·3) | 1·2 (1·0–1·3) |
| Community typeg | ||||||
| Township | Reference | Reference | Reference | Reference | Reference | Reference |
| Borough | 1·2 (1·0–1·4) | 1·2 (1·0–4·0) | 1·6 (1·3–1·9) | 1·5 (1·2–1·8) | 1·1 (1·0–1·2) | 1·1 (0·9–1·2) |
| Cityh | 2·0 (1·6–2·5) | 2·1 (1·6–2·6) | 2·1 (1·6–2·6) | 1·8 (1·4–2·3) | 1·2 (1·0–1·5) | 1·2 (1·0–1·4) |
| Socioeconomic deprivation, per quartilei | 1·2 (1·1–1·3) | 1·2 (1·1–1·3) | 1·2 (1·1–1·3) | 1·1 (1·1–1·2) | 1·1 (1·0–1·1) | 1·1 (1·0–1·1) |
| Any antibiotic prescription in previous 2 years | 3·0 (2·7–3·5) | 2·9 (2·6–3·4) | 2·5 (2·2–2·8) | 2·4 (2·1–2·8) | 2·2 (2·0–2·4) | 2·1 (1·9–2·3) |
| Antibiotic prescriptionj | ||||||
| No prescription | Reference | Reference | Reference | Reference | Reference | Reference |
| Cephalosporins | 6·9 (5·7–8·3) | 3·4 (2·8–4·2) | 3·9 (3·3–4·8) | 2·8 (2·3–3·4) | 2·9 (2·5–3·5) | 2·1 (1·8–2·5) |
| Clindamycin | 12·8 (7·7–21·3) | 4·2 (2·4–7·4) | 4·7 (2·7–8·2) | 2·6 (1·4–4·6) | 4·2 (2·5–6·9) | 2·3 (1·4–3·9) |
| Macrolides | 2·7 (2·2–3·3) | 1·1 (0·9–1·4) | 2·1 (1·7–2·5) | 1·2 (1·0–1·4) | 1·9 (1·6–2·2) | 1·2 (1·0–1·4) |
| Penicillins | 2·6 (2·3–3·0) | 1·4 (1·2–1·7) | 2·3 (2·0–2·7) | 1·3 (1·1–1·5) | 1·8 (1·6–2·1) | 1·4 (1·2–1·6) |
| Penicillin | 2·1 (1·0–4·2) | 1·8 (0·8–3·9) | 1·5 (0·8–3·0) | 0·7 (0·3–1·4) | 1·6 (0·9–2·9) | 0·9 (0·5–1·7) |
| Amino | 2·0 (1·7–2·5) | 1·2 (1·0–1·5) | 2·4 (2·0–2·8) | 1·3 (1·1–1·6) | 1·8 (1·5–2·0) | 1·3 (1·1–1·5) |
| Antistaphylococcal | 15·3 (3·4–72·4) | 3·2 (0·6–18·6) | 2·8 (0·4–19·6) | 1·1 (0·1–8·8) | 2·6 (0·5–14·2) | 1·1 (0·2–7·0) |
| β-lactam/β-lactamase inhibitors | 4·4 (3·5–5·6) | 1·7 (1·3–2·2) | 2·9 (2·3–3·6) | 1·3 (1·0–1·7) | 2·3 (1·9–2·9) | 1·5 (1·2–1·8) |
| Quinolones | 7·7 (6·3–9·5) | 2·4 (1·9–3·0) | 1·8 (1·4–2·4) | 1·5 (1·1–2·2) | 1·9 (1·5–2·3) | 1·1 (0·9–1·4) |
| Tetracyclines | 3·9 (2·8–5·3) | 1·5 (1·1–2·2) | 2·6 (1·9–3·6) | 1·6 (1·1–2·2) | 2·4 (1·8–3·2) | 1·7 (1·3–2·2) |
| TMP/SMX | 4·8 (3·8–6·1) | 1·7 (1·3–2·2) | 3·5 (2·8–4·5) | 2·1 (1·6–2·7) | 2·2 (1·7–2·7) | 1·4 (1·1–1·7) |
| Vancomycin | 31·1 (15·5–63) | 3·3 (1·5–7·2) | 0·6 (0·1–2·8) | 0·2 (0·04–1·0) | 2·7 (1·2–6·1) | 1·1 (0·5–2·6) |
| Antibiotic prescriptionk | ||||||
| 0 | Reference | Reference | Reference | Reference | Reference | Reference |
| 1 | 1·7 (1·5–2·0) | 1·7 (1·4–2·0) | 1·7 (1·5–2·0) | 1·7 (1·4–2·0) | 1·6 (1·4–1·8) | 1·5 (1·4–1·7) |
| 2–3 | 3·6 (3·0–4·3) | 3·6 (3·0–4·4) | 2·7 (2·3–3·2) | 2·5 (2·0–3·0) | 2·2 (1·9–2·6) | 2·1 (1·8–2·5) |
| ⩾4 | 9·7 (7·7–12·2) | 9·0 (7·1–11·4) | 3·7 (2·9–4·8) | 3·7 (2·9–4·8) | 2·6 (2·1–3·3) | 2·4 (1·9–3·1) |
Data are no. (%) of patients, unless otherwise indicated.
BMI, Body mass index; CI, confidence interval; CA-MRSA; community-associated methicillin-resistant S. aureus; HA-MRSA; healthcare-associated MRSA; OR, odds ratio; SSTI, skin and soft tissue infection; TMP/SMX, trimethoprim/sulfamethoxzole.
SSTI cases and controls were frequency-matched to MRSA cases on age, sex, and year of diagnosis or outpatient encounter.
Adjusted for category [<7, 7 to <19, 19 to <45, 46 to <62 (ref.), 62 to <75 and ⩾75 years), sex, race/ethnicity, ever-smoking status.
White, non-Hispanic.
Body mass index was categorized as normal (<25 kg/m2), overweight (25–29 ·9 kg/m2) and obese (⩾30 kg/m2) for persons aged 18–59 ·9 years the most recent height and a weight within 2 years of the encounter/visit were used; for persons aged ⩾60 years the most recent height and weight within 1 year of encounter/visit were used. Missing either due to the absolute value of the z score being >5 or if height and weight were not recorded in the vitals table within the 3 months before the diagnosis or visit.
Body mass index z scores for children aged 2–18 years were calculated using the 2000 CDC Growth Reference by implementing the zanthro function in Stata version 11 (normal, z score <85th percentile; overweight, 85th percentile ⩽z score <95th percentile; obese, z score ⩾95th percentile.
Season of onset: spring (March–May), summer (June–August), autumn (September–November), winter (December–February).
The overall geocoding rate was 88·6%, non-geocoding patients could not be assigned a community type or a community socioeconomic deprivation score and thus were omitted from multilevel analysis.
Census tracts were assigned to patients in cities due to the large geographical area and heterogeneous community of some cities.
ORs for socioeconomic deprivation are quartile increase in level; a higher quartile represents a more deprived community.
Order for an antimicrobial prescription in the 30–365 days before infection or visit, these are additionally adjusted for all other antibiotic classes in the table. Data on linezolid is not presented due to small cell sizes.
Count of antimicrobial prescription order in the 30–365 days before infection or visit.