Antimicrobial rationing in orthopaedic surgery

Antimicrobials in Orthopedic Infections: Overview of Clinical Perspective and Microbial Resistance

Orthopedic infections are challenging pathologies that impose a heavy burden on patients and the healthcare system. Antimicrobial therapy is a critical component of the successful management of orthopedic infections, but its effectiveness depends on patient-, surgery-, drug-, and hospital-related factors. The dramatic increase in the emergence of multidrug-resistant microbial strains necessitates new clinical approaches in order to prevent or limit this phenomenon and to ensure a favorable therapeutic outcome. The present paper reviews the currently available antimicrobial strategies in the management of orthopedic infections, highlighting their clinical use related to the occurrence of microbial resistance. Some approaches for reducing antibiotic resistance emergence in orthopedics are also presented. The use of antibiotics tailored to the microorganism's sensitivity profile, patient factors, and pharmacokinetic profile in terms of monotherapy or combinations, the understanding of microbial pathogenicity and resistance patterns, strict control measures in healthcare facilities, the development of new antimicrobial therapies (drugs, devices, technologies), and patient education for improving compliance and tolerance are some of the most important tools for overcoming microbial resistance.

The role of implant retention and conservative management in the management of fracture-related infection

Fracture-related infection (FRI) management has advanced considerably in recent years, offering new possibilities for predictable rates of infection eradication. Debridement, antibiotics, and implant retention (DAIR) procedures have shown promise in the treatment of early FRI. This article provides an overview of the principles and indications of DAIR, including the importance of meticulous debridement and the management of dead space. The outcomes of DAIR are discussed, highlighting the range of fracture union rates reported in the literature. The role of antimicrobial suppression in optimizing host biology and facilitating surgical intervention is also explored. While further research is needed to establish optimal treatment strategies, DAIR offers a valuable treatment approach for FRI when specific criteria are met.

LEVEL OF EVIDENCE

IV.

High-dose dual-antibiotic loaded cement for hip hemiarthroplasty in the UK (WHiTE 8): a randomised controlled trial

BACKGROUND

Hip fracture is the most common injury requiring treatment in hospital. Controversy exists regarding the use of antibiotic loaded bone cement in hip fractures treated with hemiarthroplasty. We aimed to compare the rate of deep surgical site infection in patients receiving high-dose dual-antibiotic loaded cement versus standard care single-antibiotic loaded cement.

METHODS

We included people aged 60 years and older with a hip fracture attending 26 UK hospitals in this randomised superiority trial. Participants undergoing cemented hemiarthroplasty were randomly allocated in a 1:1 ratio to either a standard care single-antibiotic loaded cement or high-dose dual-antibiotic loaded cement. Participants and outcome assessors were masked to the treatment allocation. The primary outcome was deep surgical site infection at 90 days post-randomisation as defined by the US Centers for Disease Control and Prevention in an as-randomised population of consenting participants with available data at 120 days. Secondary outcomes were quality of life, mortality, antibiotic use, mobility, and residential status at day 120. The trial is registered with ISRCTN15606075.

FINDINGS

Between Aug 17, 2018, and Aug 5, 2021, 4936 participants were randomly assigned to either standard care single-antibiotic loaded cement (2453 participants) or high-dose dual-antibiotic loaded cement (2483 participants). 38 (1·7%) of 2183 participants with follow-up data in the single-antibiotic loaded cement group had a deep surgical site infection by 90 days post-randomisation, as did 27 (1·2%) of 2214 participants in the high-dose dual-antibiotic loaded cement group (adjusted odds ratio 1·43; 95% CI 0·87-2·35; p=0·16).

INTERPRETATION

In this trial, the use of high-dose dual-antibiotic loaded cement did not reduce the rate of deep surgical site deep infection among people aged 60 years or older receiving a hemiarthroplasty for intracapsular fracture of the hip.

FUNDING

Heraeus Medical. Supported by the UK National Institute for Health and Care Research Oxford Biomedical Research Centre.

Effectiveness of mechanical cleaning, antibiotics, and induction heating on eradication of Staphylococcus aureus in mature biofilms

Aims

Here we used a mature seven-day biofilm model of Staphylococcus aureus, exposed to antibiotics up to an additional seven days, to establish the effectiveness of either mechanical cleaning or antibiotics or non-contact induction heating, and which combinations could eradicate S. aureus in mature biofilms.

Methods

Mature biofilms of S. aureus (ATCC 29213) were grown on titanium alloy (Ti6Al4V) coupons for seven days and were subjected to the following treatments or their combinations: antibiotics, mechanical cleaning, or heat shock by induction heating of 60°C for one minute. Experiments were repeated at least five times.

Results

In the untreated biofilm, growth up to 1.8×10¹¹ colony-forming units (CFU)/cm² was observed. Treatment with ciprofloxacin, flucloxacillin, vancomycin, cefuroxime, and amoxicillin all with rifampicin gave 6.0 log, 6.1 log, 1.4 log, 4.8 log, and 3.6 log reduction in CFU/cm², respectively. Mechanical cleaning alone resulted in 4.9 log reduction and induction heating in 7.3 log reduction. There was an additional effect of ciprofloxacin, flucloxacillin, and induction heating when used in combinations. There was no additional effect for mechanical cleaning. No bacterial growth could be detected after induction heating followed by seven days of ciprofloxacin with rifampicin.

Conclusion

Mechanical cleaning, antibiotics, and non-contact induction heating reduced the bacterial load of mature S. aureus biofilms with approximately 5 log or more as a single treatment. The effect of mechanical cleaning on mature S. aureus biofilms was limited when used in combination with antibiotics and/or induction heating.

Cite this article: Bone Joint Res 2022;11(9):629–638.

Adaptive antimicrobial resistance, a description of microbial variants, and their relevance to periprosthetic joint infection

Periprosthetic joint infection (PJI) is a difficult complication requiring a comprehensive eradication protocol. Cure rates have essentially stalled in the last two decades, using methods of antimicrobial cement joint spacers and parenteral antimicrobial agents. Functional spacers with higher-dose antimicrobial-loaded cement and antimicrobial-loaded calcium sulphate beads have emphasized local antimicrobial delivery on the premise that high-dose local antimicrobial delivery will enhance eradication. However, with increasing antimicrobial pressures, microbiota have responded with adaptive mechanisms beyond traditional antimicrobial resistance genes. In this review we describe adaptive resistance mechanisms that are relevant to the treatment of PJI. Some mechanisms are well known, but others are new. The objective of this review is to inform clinicians of the known adaptive resistance mechanisms of microbes relevant to PJI. We also discuss the implications of these adaptive mechanisms in the future treatment of PJI. Cite this article: Bone Joint J 2022;104-B(5):575-580.

Animal experimental investigation on the efficacy of antibiotic therapy with linezolid, vancomycin, cotrimoxazole, and rifampin in treatment of periprosthetic knee joint infections by MRSA

Aims

Periprosthetic joint infections (PJIs) are rare, but represent a great burden for the patient. In addition, the incidence of methicillin-resistant Staphylococcus aureus (MRSA) is increasing. The aim of this rat experiment was therefore to compare the antibiotics commonly used in the treatment of PJIs caused by MRSA.

Methods

For this purpose, sterilized steel implants were implanted into the femur of 77 rats. The metal devices were inoculated with suspensions of two different MRSA strains. The animals were divided into groups and treated with vancomycin, linezolid, cotrimoxazole, or rifampin as monotherapy, or with combination of antibiotics over a period of 14 days. After a two-day antibiotic-free interval, the implant was explanted, and bone, muscle, and periarticular tissue were microbiologically analyzed.

Results

Vancomycin and linezolid were able to significantly (p < 0.05) reduce the MRSA bacterial count at implants. No significant effect was found at the bone. Rifampin was the only monotherapy that significantly reduced the bacterial count on implant and bone. The combination with vancomycin or linezolid showed significant efficacy. Treatment with cotrimoxazole alone did not achieve a significant bacterial count reduction. The combination of linezolid plus rifampin was significantly more effective on implant and bone than the control group in both trials.

Conclusion

Although rifampicin is effective as a monotherapy, it should not be used because of the high rate of resistance development. Our animal experiments showed the great importance of combination antibiotic therapies. In the future, investigations with higher case numbers, varied bacterial concentrations, and changes in individual drug dosages will be necessary to be able to draw an exact comparison, possibly within a clinical trial.

Cite this article: Bone Joint Res 2022;11(3):143–151.