Aim

Gram negative bacteria (GNB) are emerging pathogens in chronic post-traumatic osteomyelitis. However, data on multi-drug (MDR) and extensively drug resistant (XDR) GNB are sparse.

Aim

Data on Prosthetic joint infection (PJI) caused by multi-drug resistant (MDR) or XDR (extensively drug resistant) Gram negative bacteria (GNB) are limited. Treatment options are also restricted. We conducted a multi-national, multi-center assessment of clinical data and factors of outcome for these infections.

Prosthetic joint infections are difficult to treat due to bacterial biofilm. Our group has developed a linezolid elution system by human cancellous bone delivering high concentrations the first 48 hours (Giannitsioti et al. 53rd ICAAC, 2013: A-1050). We tested the activity of this system to inhibit growth of one ica expressing isolate of Staphylococcus epidermidis (MRSE).

At a first step, sterile mesh cylinders containing bone particles of the femoral head of healthy volunteers (MCB) were impregnated into 3mg/ml linezolid for 1, 24 and 48 hours. Then log-phase inocula of 103, 105 and 107cfu/ml were exposed to MCB at 370C for 8 days with regular readings of bacterial growth. MCB were transferred into fresh Muller-Hinton Broth (MHB) every 24h to avoid material corrosion. At a second step, to simulate the ability of the system against biofilm-coated MCB, MCB without linezolid were incubated with 103 and 105 cfu/ml for 1 and 24h. MCB were daily transferred into fresh MHB containing 100μg/ml on day 1, 15 μg/ml on day 2, 3 μg/ml on day 3 and 0.5 μg/ml on day 4.

24h linezolid impregnated MCB achieved rapid bacterial killing of the 105 cfu/ml bacterial suspension followed by re-growth (Figure, n= 5). Similar results were observed for 1h and 48h impregnation and for both tested inocula. When biofilm-coated MCB generated by 24h exposure to 105 cfu/ml were exposed to linezolid, rapid bacterial killing was achieved followed by re-growth.

Linezolid local elution may inhibit biofilm-producing MRSE only when locally eluted concentrations exceed 10μg/ml.

The objective of the present study is to analyse the clinical, microbiological, and therapeutic features of patients with infective spondylodiscitis (ISD), who were followed up in our Outpatient Bone Infection Clinic.

We retrospectively studied the epidemiological and clinical characteristics of all patients diagnosed with ISD from January 1998 to December 2006. Data were extracted from an electronic data base registry and patients’ files.

Sixty patients either with spontaneous (n= 42, 70%) or postoperative (n= 18, 30%) ISD were evaluated. Population mean age was 56 years, 33 (55%) were male and 27 (45%) were female. The infection was localised in the lumbar (78%), thoracic (18%) or cervical (4%) spine. Predominate symptoms were pain (87%) and fever (50%). Fistula was observed exclusively in postoperative ISD (45%). In spontaneous ISD, the major causes were Brucella spp (33%), gram positive cocci (12%), gram negative bacteria (14%), Mycobacterium tuberculosis (7%), while in 33% of cases no pathogen was detected. In postoperative episodes of ISD the major causes were gram positive cocci (45%), gram negative bacteria (30%) and polymicrobial infection was documented in 22% of cases while in 25% of cases no pathogen was detected. Based on clinical, laboratory and imaging (especially MRI) data, treatment was individualised. Most patients (88%) received a combined antimicrobial treatment. Patients with spontaneous pyogenic/brucellosis or tuberculous/post-operative ISD received treatment for a median duration of 8/12/10 months and the response rate was 84%/81%/55.5%, respectively. Surgery was necessary in 40% of postoperative ISD cases for healing, while only one spontaneous case required a surgical intervention.

ISD is more frequently localised at the lumbar level. Long term combination antimicrobial treatment may be essential. Surgery may be required in iatrogenic cases in the presence of foreign bodies.