TABLE 4.
Clinical and microbiological characteristics of cases with discordant tissue and sonication culture results that did not meet the clinical definition of infection
| Case no. | No. of mo since device implantation |
Antibiotics in preceding 14 days |
No. of tissue specimens |
Sonication specimen | Sonication culture (CFU/ml)e |
Tissue culture (no. specimens culture positive for each organism)e |
Treated | Follow-up (mo) | Outcome | Diagnosis following blinded clinical review of case notes |
|---|---|---|---|---|---|---|---|---|---|---|
| Prosthetic joint infection (PJI) cases |
||||||||||
| 9 | 44 | No | 6 | Knee components |
Propionibacterium acnes
(>100), CoNSa (>500) |
Bacillus species (1) | Yes | 85 | Good | Not infected |
| 70 | 5 | Yes | 5 | Hip prosthesis |
Staphylococcus epidermidis (4), Enterococcus faecalis (1) |
Yes | 2 | Died of pneumonia |
Infected (PJI) | |
| 77 | 37 | No | 4 | Elbow components | CoNS (90) | No | 25 | Good | Not infected | |
| 171 | 52 | No | 4 | Hip prosthesis | CoNS (>250) | No | 33 | Good | Not infected | |
| 241 | 13 | No | 5 | Hip components | CoNS (>100) |
Moraxella osloensis (1), Micrococcus luteus (1) |
No | 47 | Good | Not infected (metallosis) |
| 269 | 40 | No | 4 | Knee prosthesis | P. acnes (>100) | No | 44 | Goodb | Not infected (aseptic loosening) | |
| 334 | 0 | No | 5 | Hip components | CoNS-1 (4), CoNS-2 (1) | Yes | 6 | Good | Probably not infected (loosening due to trauma) |
|
| 397 | 124 | No | 4 | Hip components | S. epidermidis (4) | Yes | 19 | Good | Probably not infected (aseptic loosening) |
|
| 432 | 3 | Yes | 5 | Hip prosthesis |
S. epidermidis (3), Bacillus spp. (1) |
Yes | 18 | Good | Infected (PJI) | |
| 491 | 193 | Yes | 4 | Hip prosthesis | S. aureus (4) | Yes | 5 | Good | Infected (PJI) | |
| Other orthopedic device- related (non-PJI) cases |
||||||||||
| 124 | 77 | No | 3 | Bone knee | CoNS (>500) | No | 49 | Good | Not infected (mechanical failure) | |
| 179 | 248 | No | 3 | Metalware spine | CoNS (<50) | CoNS (2), S. epidermidis (1) | No | 23 | Poor | Infected |
| 197 | 8 | No | 5 | Metalware tibia |
S. epidermidis (2), S. aureus (1) |
Yes | 9 | Good | Probably infected (infected nonunion) |
|
| 210 | 17 | No | 5 | Metalware tibia | CoNS (>100) | No | 3 | Died of pneumonia |
Uncertain | |
| 262 | 4 | No | 4 | Metalware | CoNS-1 (>100), CoNS-2 (>100) | No | 45 | Good | Not infected (aseptic nonunion) | |
| 339 | 7 | No | 4 | Metalware femur | P. acnes (>250) | No | 40 | Poor (ongoing pain) |
Uncertain | |
| 368 | 47 | No | 5 | Metalware ankle/foot | CoNSc (<50) | CoNS (2), S. epidermidis-1 (2), S. epidermidis-2 (1) |
Yes | 24 | Good | Probably not infected (aseptic nonunion) |
| 376 | 1 | No | 4 | Metalware ankle/foot | CoNS (>100) | No | 36 | Good | Not infected (aseptic nonunion) | |
| 429 | 3 | No | 3 | Metalware femur | CoNS (>100), Bacillus spp. (>100) | No | 5 | Good | Not infected (mechanical failure; periprosthetic fracture) |
|
| 489 | 9 | No | 4 | Metalware ankle/foot | CoNSd | No | 2 | Good | Not infected | |
| 498 | 1 | Yes | 5 | Metalware ankle/foot | CoNS (>250) | Yes | 6 | Good | Uncertain | |
| 535 | 22 | No | 5 | Metalware ankle/foot |
S. epidermidis-1 (4), S. epidermidis-2 (3), S. epidermidis-3 (1) |
Yes | 17 | Good | Infected (infected nonunion and septic arthritis) |
a
CoNS, coagulase-negative staphylococci (not further identified).
b
Later revision for metallosis, but no clinical or microbiological evidence of infection at repeat surgery.
c
Sonication culture below the 50 CFU/ml threshold for positive culture.
d
Number of CFU per milliliter not documented.
e
Organism numerical suffixes denote different isolates of the same species; e.g., “CoNS-1” and “CoNS-2” denote two isolates of coagulase-negative staphylococci that are distinguished by their antimicrobial susceptibility profile.