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Assessing yield and impact of 5-day versus 10-day incubation time in suspected prosthetic joint infection: a
Victoria Jordan1, Joshua S Davis2, Syeda Naqvi3
1Department of Microbiology, NSW Health Pathology, John Hunter Hospital, New Lambton Heights, NSW, Australia; School of Medicine and Public Health, University of Newcastle, Callaghan, NSW, Australia.
Abstract:
Optimising laboratory processes is paramount in differentiating prosthetic joint infection (PJI) from non-infectious causes of joint dysfunction. However, the optimal duration of incubation of PJI samples remains unclear in the modern laboratory. This study explored whether an increased incubation time in the routine processing of samples from suspected PJI, from 5-7 to 10 days, would significantly increase the yield of clinically relevant bacteria. A total of 280 prosthetic joint samples from 53 patients were included prospectively over a 3-month period. After an initial standard 5-day incubation plus additional 2 days subculture of thioglycolate broth in high-risk samples (current standard in this laboratory), incubation was extended until day 10. From the 280 samples included, 190 organisms were isolated. Potentially significant additional pathogens that were not detected with standard approaches were found in 5 of 280 samples (2%) with prolonged incubation, though the overall clinical significance of these organisms was unclear. Of all non-significant growth, the majority (70%) occurred on extended incubation. In conclusion, extending incubation of prosthetic hip and knee joint samples from 5-7 to 10 days routinely was associated with increased risk of isolating contaminating organisms without significant benefit. However, further studies are needed to clarify the utility of extended incubation in upper limb joints.
Insights
Extending prosthetic joint infection (PJI) sample incubation to 10 days increased bacterial contamination without significant diagnostic benefit. Standard 5-7 day incubation remains optimal for most PJI diagnoses.
Area of Science:
- Medical Microbiology
- Orthopedic Surgery
- Laboratory Diagnostics
Background:
- Differentiating prosthetic joint infection (PJI) from non-infectious causes is crucial for patient outcomes.
- Current incubation protocols for PJI samples lack standardized optimal duration.
- Modern laboratory practices necessitate re-evaluation of established diagnostic timelines.
Purpose of the Study:
- To investigate if extending incubation time for PJI samples from 5-7 to 10 days improves bacterial yield.
- To assess the clinical significance of additional pathogens detected with prolonged incubation.
- To determine the impact of extended incubation on contamination rates.
Main Methods:
- Prospective analysis of 280 prosthetic joint samples from 53 patients over 3 months.
- Comparison of standard 5-7 day incubation with extended 10-day incubation.
- Inclusion of thioglycolate broth subculture for high-risk samples.
Main Results:
- Extended incubation detected additional pathogens in 2% of samples (5/280), with unclear clinical significance.
- The majority (70%) of non-significant bacterial growth occurred during the extended incubation period.
- No significant diagnostic benefit was observed from routine 10-day incubation for hip and knee PJI samples.
Conclusions:
- Routine extension of PJI sample incubation to 10 days increases contamination risk without substantial diagnostic gain.
- Current 5-7 day incubation protocols appear adequate for most prosthetic joint infection diagnoses.
- Further research is required to evaluate extended incubation for upper limb joint samples.
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