My research into antibiotic loaded bone cement was carried out in an eight week summer research project with Professor Tom Smith at Sheffield Hallam University, UK. This was funded by a Society for Applied Microbiology (SfAM) Students Into Work Grant, for which i am very grateful!
The data from this work was recently published in the Journal of Antimicrobial Chemotherapy, titled: Temocillin: a new candidate antibiotic for local antimicrobial delivery in orthopaedic surgery? If anyone wants to read this but cannot access it, please let me know.
The aim of my work was to look at the antibiotic temocillin, a derivative of penicillin, with a narrow-range specificity for some Gram negative bacteria, mainly the Enterobacteriaceae which include Escherichia coli. As i have mentioned in the previous two posts, there is widespread use of antibiotics loaded into orthopaedic bone cement for prophylactic treatment of surgical site infection (SSI) causing bacteria. Temocillin hadn’t previously been tested in this role, despite being originally described in 1982. Rather than repeat myself here and write a carbon copy of my paper, i am going to give the highlights!
Temocillin was added to the bone cement (already containing the antibiotic gentamicin) at varying concentrations, which was then submerged in buffer to elute. This eluate was analysed by high-perfomance liquid chromatography mass spectrometry (HPLC-MS). Increasing the temocillin added to the cement increased the amount that was released, but decreased the amount of the gentamicin that could be eluted. However even at the highest concentration of temocillin, the concentration of eluted gentamicin was still more than high enough to kill its target bacteria.
As the bone cement will be load-bearing once the patient is walking post-surgery, the addition of antibiotics cannot weaken the structure of the cement. The temocillin loaded cement was impact tested, and no significant difference was seen in strength between cement with 1.25 and 10% weight temocillin.
Finally, to make sure the eluted temocillin retained its antimicrobial activity, it was tested against a number of lab strains and clinical isolates of E.coli. This was done using minimum inhibitory concentration (MIC) tests comparing eluted and standard temocillin. Although there were some differences in the minimum concentration required to inhibit E. coli growth, the values were relatively similar between eluted and standard temocillin. Additionally, all 6 strains, even SSI clinical isolates were affected by the eluted antibiotic.
So in conclusion, this work proves the concept of the inclusion of temocillin in bone cement with at least one other antibiotic for the prophylactic treatment of some important Gram negative SSIs.
If you enjoyed reading this, or have any questions about my work, please leave me a comment below!
Thanks for reading!