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Volume 32, Number 11—November 2026
Research
Microbial Etiology of Postoperative Spinal Fusion Infections and Factors Associated with Gram-Negative Infections, United States, 2021–2022
Table 3
Multinomial logistic regression analysis of factors associated with gram-negative spinal infections in study of microbial etiology of postoperative spinal fusion infections and factors associated with gram-negative infections, United States, 2021–2022*
| Characteristic | Staphylococcus aureus infection, N = 1,822 | Gram-negative infection, N = 2,265 |
||
|---|---|---|---|---|
| No. infections | OR (95% CI) | p value | ||
| Mean age, y (SD) |
59.4 (13.6) |
64.1 (13.5) |
1.03 (1.02–1.03) |
<0.001 |
| Mean BMI (SD) | 31.1 (7.6) | 33.4 (8.1) | 1.03 (1.02–1.04) | <0.001 |
| Unknown |
123 (6.8) |
112 (4.9) |
– |
– |
| Male sex | 862 (47.3) | 884 (39.1) | 0.72 (0.63–0.84) | <0.001 |
| Unknown |
– |
1 |
– |
– |
| Outpatient surgery |
28 (1.5) |
10 (0.4) |
0.41 (0.18–0.96) |
0.041 |
| Duration of surgery, h |
3.59 (2.1) |
4.4 (2.5) |
1.20 (1.16–1.24) |
<0.001 |
| Approach | ||||
| Anterior | 208 (12.2) | 204 (9.5) | Referent | |
| Posterior | 1,447 (85.2) | 59 (2.7) | 1.01 (0.80–1.28) | >0.9 |
| Both | 44 (2.6) | 1,890 (87.8) | 0.87 (0.54–1.40) | 0.6 |
| Unknown |
123 (6.8) |
112 (4.9) |
– |
– |
| ASA class | ||||
| 1 | 16 (0.9) | 2 (0.1) | Referent | |
| 2 | 465 (27.4) | 369 (17.2) | 4.90 (1.06–22.6) | 0.042 |
| 3 | 1,131 (66.6) | 1,556 (72.3) | 7.15 (1.56–32.8) | 0.011 |
| 4 | 86 (5.1) | 224 (10.4) | 15.7 (3.35–73.5) | <0.001 |
| Unknown |
123 (6.8) |
113 (5.0) |
– |
– |
| Diabetes |
492 (29.0) |
757 (35.2) |
1.07 (0.92–1.24) |
0.4 |
| Wound class | ||||
| Clean | 1,656 (97.5) | 2,064 (95.9) | Referent | |
| Clean-contaminated | 28 (1.7) | 54 (2.5) | 1.74 (1.06–2.86) | 0.030 |
| Contaminated | 4 (0.2) | 12 (0.6) | 2.14 (0.65–7.07) | 0.2 |
| Dirty | 11 (0.7) | 23 (1.1) | 1.75 (0.79–3.85) | 0.2 |
| Unknown |
123 (6.8) |
112 (4.9) |
– |
– |
| Spinal level | ||||
| Axis-atlas/cervical | 12 (0.7) | 21 (0.7) | Referent | |
| Cervical/dorsal/dorsolumbar | 332 (19.5) | 330 (14.5) | 1.11 (0.77–1.62) | 0.6 |
| Dorsal/dorsolumbar | 350 (20.6) | 469 (21.8) | 1.27 (0.99–1.63) | 0.056 |
| Lumbar/lumbosacral | 916 (53.9) | 1,333 (61.9) | 1.51 (1.23–1.86) | <0.001 |
| Unknown |
123 (6.8) |
112 (4.9) |
||
| Trauma |
87 (5.1) |
139 (6.5) |
1.91 (1.38–2.64) |
<0.001 |
| Closure | ||||
| Intentionally left open | 14 (0.8) | 21 (0.98) | Referent | |
| Fully closed or partial | 1,684 (99.2) | 2,131 (99.0) | 1.08 (0.50–2.33) | 0.9 |
| Unknown |
123 (6.8) |
112 (4.9) |
||
| Timing of infection, days from procedure, mean (IQR) |
24 (17–33) |
19 (14–27) |
0.97 (0.96–0.97) |
<0.001 |
| Depth of infection | ||||
| Superficial | 424 (23.3) | 657 (29.0) | Referent | |
| Deep | 868 (47.6) | 1,025 (45.3) | 0.88 (0.74–1.05) | 0.15 |
| Organ space |
530 (29.1) |
583 (25.7) |
0.85 (0.70–1.03) |
0.1 |
| Emergency | 120 (7.1) | 167 (7.8) | 0.99 (0.75–1.32) | >0.9 |
| Unknown |
123 (6.8) |
112 (4.9) |
– |
– |
| Use of scope | 2 (0.1) | 7 (0.3) | 2.60 (0.51–13.4) | 0.3 |
| Unknown | 123 (6.8) | 112 (4.9) | – | – |
*Values are no. (%) except as indicated. ORs represent the relative odds of gram-negative infection compared with the reference group of monomicrobial Staphylococcus aureus spinal fusion surgical site infection. ASA level 5 was removed because of insufficient numbers. Dashes indicate value was not calculated. ASA, American Society of Anesthesiologists; IQR, interquartile range; OR, odds ratio.