Body mass index matters: morbid obese patients have different microorganism profiles in the setting of periprosthetic hip joint infections.

PURPOSE

This study investigated the relationship between BMI and microorganism profiles, with a particular focus on gut microorganisms in patients with PJI following total hip arthroplasty (THA). It also explored comorbidities, that may contribute to these variations.

METHODS

This study included all patients treated at our institution for a PJI of a THA between 1996 and 2021. Patients were categorized into four distinct BMI groups: <30; 30-34.9; 35-39.9; ≥ 40. Bivariate and logistic regression analysis were conducted, with presentation of odds ratio (OR) and 95% confidence interval (CI).

RESULTS

A total of 3645 hip PJI cases were recruited for the final analysis. Patients with a BMI ≥ 40 had approximately a ten fold higher risk for Streptococcus dysgalactiae (p < 0.001; OR = 9.92; 95% CI 3.87-25.44) and a seven fold higher risk for Proteus mirabilis (p < 0.001; OR = 7.43; 95% CI 3.13-17.67) and Klebsiella pneumoniae (p < 0.001; OR = 6.9; 95% CI 2.47-19.31). Furthermore, polymicrobial infections (p < 0.001; OR = 2.17; 95% CI 1.50-3.15) were found to be significantly more prevalent in patients with a BMI ≥ 40.

CONCLUSION

Obese patients (BMI ≥ 30) displayed a distinct microorganism profile in hip PJIs, mainly dominated by Firmicutes and Proteobacteria. Comorbidities such as diabetes, hypertension, and hyperlipidaemia may contribute to a leaky gut syndrome, increasing PJI risk caused by gut microorganisms. Optimizing comorbidities may help reduce the risk of hip PJI. Further research is needed to clarify the relationship between obesity, gut microbiome alterations and hip PJI development.