Abstract
Introduction: While the incidence of infection associated with hip and knee prosthesis is low, with the increasing number of arthroplasties being carried out, the total number of such cases is increasing. Also increasing is the number of multi-resistant organisms. These factors have raised questions regarding the optimal antibiotic impregnated cement for use in both spacers and in cemented revisions.
While gentamycin, erythromycin, cefotaxime and vanomycin have a proven record as effective thermostatic antibiotics, newer antibiotics teicoplanin (although used in clinical practice) are as yet untested.
Aim: To investigate the effectiveness of teicoplanin impregnated cement against a Staph Aureus.
Method: A pure culture of Staphlococcus Aureus with known antibiotic sensitivities was obtained. Six batches of Palacos cement were mixed without under sterile conditions. One batch contained cement alone. The other 5 batches were mixed with one of gentamycin, vancomycin, erythromycin, cefotaxime and teicoplanin.
Group 1: A pure culture of over 60 colonies was grown on 5 Columbian blood agar plates. A 1cm spherical sample of each batch of the cement was placed on each plate at regular intervals and allowed to heat and harden.
Group 2: A further 1cm spherical ball of cement from each batch were placed on a further 5 blood agar plates which were then inoculated with the Staph Aureus and the cement was allowed to heat and harden.
Group 3: 24 hours later, the cement was placed on a further 5 blood agar plates which were then inoculated with the Staph Aureus.
Results: Group 1: None of the cement groups had any effect on the established colonies of Staph Aureus.
Groups 2 & 3: The cement without antibiotic had no effect on the growth of the antibiotic even when allowed to heat on the plate. All the other groups including the teicoplanin impregnated cement both initially and after 24 hours, caused a zone of inhibition, ie prevented bacterial growth.
Conclusion:
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Heat alone did not affect the growth of the bacteria.
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None of the antibiotic impregnated cement batches had any effect on an established growth of Staph Aureus indicating the effect of antibiotic impregnated cement may be bacteriostatic rather than bacteriocidal.
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Teicoplanin is thermosable and is effective in the short term at least at halting the growth of Staph Aureus.
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Addition of antibiotics to cement may change the biomechanical properties of the cement. It was noted that it took on average twice as long for the teicoplanin-impregnated cement to harden. Further investigations into this are ongoing.
The abstracts were prepared by Mr Ray Moran. Correspondence should be addressed to him at Irish Orthopaedic Associaton, Secretariat, c/o Cappagh National Orthopaedic Hospital, Finglas, Dublin 11.
