Table 1.
Case Series and Microbiological (Phenotypic and Genotypic) Description and Comparative Analysis According to Methicillin Susceptibility and Clinical Presentation of the Prosthetic Joint Infection
| All Cases (n = 88), No. (%) | MRSA (n = 20), No. (%) | MSSA (n = 68), No. (%) | P | Hematogenous Infection (n = 19),a No. (%) | Postsurgical <90 d (EPI) (n = 45),a No. (%) | Postsurgical >90 d (CPI) (n = 21),a No. (%) | P (HI vs EPI) | P (EPI vs CPI) | P (HI vs CPI) | |
|---|---|---|---|---|---|---|---|---|---|---|
| Baseline features | ||||||||||
| Sex (men) | 35 (39.8) | 8 (40.0) | 27 (39.7) | .981 | 8 (42.1) | 15 (33.3) | 11 (52.4) | .504 | .140 | .516 |
| Age, yb | 74.7 ± 14.1 | 79.8 ± 8.8 | 73.2 ± 15.0 | .102 | 77.4 ± 13.9 | 74.2 ± 14.1 | 73.5 ± 15.3 | .293 | .962 | .307 |
| Diabetes mellitus | 16 (18.2) | 5 (25.0) | 11 (16.2) | .509 | 4 (21.1) | 8 (17.8) | 3 (14.3) | .739 | 1.000 | .689 |
| Chronic renal impairment | 14 (15.9) | 3 (15.0) | 11 (16.2) | 1.000 | 4 (21.1) | 6 (13.3) | 4 (19.0) | .466 | .714 | 1.000 |
| Rheumatoid arthritis | 7 (8.0) | 2 (10.0) | 5 (7.4) | .655 | 2 (10.5) | 3 (6.7) | 1 (4.8) | .629 | 1.000 | .596 |
| Prosthesis location (knee)c | 40 (45.5) | 8 (40.0) | 32 (47.1) | .619 | 16 (84.2) | 18 (40.0) | 4 (19.0) | .002* | .160 | <.001* |
| Revision prosthesis | 22 (25.0) | 4 (20.0) | 18 (26.5) | .770 | 5 (26.3) | 9 (20.0) | 7 (33.3) | .742 | .355 | .736 |
| Clinical presentation | ||||||||||
| Hematogenous infectiona | 19 (21.6) | 2 (10.0) | 17 (25.0) | .220 | - | - | - | - | - | - |
| Polymicrobial infection | 14 (15.9) | 3 (15.0) | 11 (16.2) | 1.000 | 0 (0.0) | 8 (17.8) | 6 (28.6) | .093 | .346 | .021* |
| Bacteremia | 18 (20.5) | 3 (15.0) | 15 (22.1) | .753 | 9 (47.4) | 6 (13.3) | 2 (9.5) | .008* | 1.000 | .007* |
| Temperature >37ºC | 31 (35.2) | 6 (30.0) | 25 (36.8) | .578 | 11 (57.9) | 16 (35.6) | 3 (14.3) | .098 | .075 | .004* |
| Sinus tract | 24 (27.3) | 8 (40.0) | 16 (23.5) | .146 | 0 (0.0) | 7 (15.6) | 16 (76.2) | .094 | <.001* | <.001* |
| Leukocytes, ×109/Lb,d | 10.3 ± 6.3 | 7.6 ± 6.8 | 11.1 ± 5.9 | .010* | 11.4 ± 7.6 | 10.4 ± 5.4 | 9.0 ± 6.5 | .397 | .247 | .124 |
| C-reactive protein, mg/Lb,d | 140.4 ± 128.9 | 121.4 ± 127.1 | 145.8 ± 129.9 | .367 | 244.8 ± 130.1 | 128.5 ± 122.3 | 75.0 ± 89.4 | .002* | .096 | <.001* |
| Surgical management | ||||||||||
| DAIRg | 58 (65.9) | 9 (45.0) | 49 (72.1) | .025* | 16 (84.2) | 33 (73.3) | 8 (38.1) | .521 | .006* | .003* |
| Antimicrobial resistance | ||||||||||
| Oxacillin | 20 (22.7) | - | - | - | 2 (10.5) | 9 (20.0) | 7 (33.3) | .483 | .239 | .133 |
| Levofloxacin | 21 (23.9) | 17 (85.0) | 4 (5.9) | <.001* | 3 (15.8) | 9 (20.0) | 8 (38.1) | 1.000 | .117 | .115 |
| Rifampin | 3 (3.4) | 1 (5.0) | 2 (2.9) | .543 | 0 (0.0) | 1 (2.2) | 2 (9.5) | 1.000 | .236 | .488 |
| Vancomycin MIC ≥1.5 mg/L | 11 (12.5) | 6 (30.0) | 5 (7.4) | .015* | 2 (10.5) | 1 (2.2) | 7 (33.3) | .208 | .001* | .133 |
| Phenotypic characteristics | ||||||||||
| agr functionality | ||||||||||
| Negative | 30 (34.1) | 6 (30.0) | 24 (35.3) | 6 (31.6) | 13 (28.9) | 9 (42.9) | ||||
| Weak | 24 (27.3) | 4 (20.0) | 20 (29.4) | .474 | 10 (52.6) | 7 (15.6) | 6 (28.6) | .003* | .117 | .335 |
| Strong | 34 (38.6) | 10 (50.0) | 24 (35.3) | 3 (15.8) | 25 (55.6) | 6 (28.6) | ||||
| β-hemolysis | 77 (87.5) | 20 (100) | 57 (83.8) | .063 | 15 (78.9) | 42 (93.3) | 17 (81.0) | .182 | .196 | 1.000 |
| Biofilm formation, OD 595 nmb | 0.12 ± 0.11 | 0.18 ± 0.17 | 0.11 ± 0.07 | .001* | 0.09 ± 0.04 | 0.13 ± 0.14 | 0.13 ± 0.07 | .150 | .117 | .008* |
| Molecular epidemiology | ||||||||||
| Clonal complex | ||||||||||
| CC5 | 27 (30.7) | 17 (85.0) | 10 (14.7) | 2 (10.5) | 15 (33.3) | 8 (38.1) | ||||
| CC15 | 7 (8.0) | 0 (0.0) | 7 (10.3) | 1 (5.3) | 4 (8.9) | 2 (9.5) | ||||
| CC30 | 13 (14.8) | 0 (0.0) | 13 (19.1) | <.001* | 3 (15.8) | 5 (11.1) | 5 (23.8) | .162 | .605 | .088 |
| CC45 | 12 (13.6) | 1 (5.0) | 11 (16.2) | 2 (10.5) | 8 (17.8) | 2 (9.5) | ||||
| Othere | 29 (33.0) | 2 (10.0) | 27 (39.7) | 11 (57.9) | 13 (28.9) | 4 (19.0) | ||||
| agr group | ||||||||||
| agr I | 26 (29.5) | 2 (10.0) | 24 (35.3) | 8 (42.1) | 13 (28.9) | 4 (19.0) | ||||
| agr II | 35 (39.8) | 17 (85.0) | 18 (26.5) | <.001* | 5 (26.3) | 18 (40.0) | 10 (47.6) | .495 | .685 | .225 |
| agr III | 27 (30.7) | 1 (5.0) | 26 (38.2) | 6 (31.6) | 14 (31.1) | 7 (33.3) |
Abbreviations: CC, clonal complex; CPI, chronic postoperative infection; DAIR, debridement, antibiotics, and implant retention; EPI, early postoperative infection; HI, hematogenous infection; MIC, minimum inhibitory concentration; MRSA, methicillin-resistant Staphylococcus aureus; MSSA, methicillin-susceptible Staphylococcus aureus; OD, optical density.
aThree cases (2 infections caused by a contiguous suppurative focus and 1 positive intraoperative culture) were excluded from this comparison.
bMean ± SD.
cThere were 40 knee prostheses and 46 hip prostheses (14 hemiarthroplasties and 32 total hip replacements).
dData obtained at diagnosis, before the performance of surgical treatment (either debridement or prosthesis removal).
eOther CCs in all cases (n = 88): 1 (1.1%) CC1, 2 (2.3%) CC6, 4 (4.5%) CC8, 2 (2.3%) CC9, 1 (1.1%) CC10, 5 (5.7%) CC22, 2 (2.3%) CC25, 1 (1.1%) CC188, 6 (6.8%) CC398, 3 (3.4%) CC509, 1 (1.1%) CC707, and 1 (1.1%) CC1021.
*These results are statistically significant.