Aims

The aim of this study was to determine whether the sequential application of povidone iodine-alcohol (PVI) followed by chlorhexidine gluconate-alcohol (CHG) would reduce surgical wound contamination to a greater extent than PVI applied twice in patients undergoing spinal surgery.

Recent work has demonstrated that intra-operative contamination of spinal surgical wounds is relatively common. The most frequently isolated wound contaminants are Propionibacterium spp. and coagulase negative Staphylococcus spp. The aim of this study is to examine the efficacy of prophylactic antibiotics used for spinal surgery against bacterial contaminants isolated from intra-operative samples retrieved during spinal surgical procedures.

Intra-operative wound samples were taken from 94 patients undergoing spinal surgery. Samples including skin, subcutaneous tissue and wound washings were processed, inoculated onto agar and incubated under both aerobic and anaerobic conditions for a period of 2 weeks. Bacterial growth was identified using commercially available biochemical test galleries. Thirty-six bacterial isolates were identified. The predominant bacteria isolated included Propionibacterium spp. (n=21) and coagulase negative Staphylococcus spp. (n=15). Each bacterial isolate was tested for its susceptibility to antibiotics used as antimicrobial prophylaxis during spinal surgery. Antibiotic sensitivities were determined in accordance with National Committee for Clinical Laboratory Standards (NCCLS) guidelines.

The antibiotic that performed best against Staphylococcus spp. isolated was ciprofloxacin with 93% of isolates being susceptible to this antibiotic. Cefamandole and cefuroxime also performed well against Staphylococcus spp. isolates.

The antibiotic that performed best against Propioni-bacterium spp. isolates was cefamandole with 100% of isolates being susceptible. Cefuroxime and ciprofloxacin also performed well. The antibiotic that performed least well against bacterial isolates was erythromycin with only 76% of Propionibacterium spp. and 47% of Staphylococcus spp. exhibiting susceptibility.

The results of this study demonstrate that ciprofloxacin, cefuroxime and cefamandole are effective against the majority of Propionibacterium spp. and Staphylococcus spp. isolated from within the spinal wound during surgery. The use of erythromycin in the penicillin allergic patient is questioned and ciprofloxacin proposed as a possible alternative.

The first aim of the study was to investigate if bacteria were implicated in non-union of fractures of the tibia and femur, which had been treated with intramedullary nailing. The second aim was to evaluate the antimicrobial susceptibility of bacteria isolated from the retrieved intramedullary nails.

Forty intramedullary nails removed from tibial and femoral fractures were retrieved for the purpose of the study. Twenty of these nails were from fractures, which had successfully united and 20 were removed from fractures which had failed to unite prior to further operative intervention. There was no evidence of clinical infection in either of the two groups. The nails were subjected to ultrasound in the research laboratory to dislodge adherent bacteria formed as biofilm from the surface of the nail. Using both standard culture techniques and non-culture techniques (Immunofluorescence microscopy and PCR analysis) any dislodged bacteria were isolated and identified.

Isolated bacteria were tested for antimicrobial susceptibility to commonly used antibiotics in orthopaedic practice according to NCCLS guidelines.

Bacteria were detected in 15 out of 20 [75%] of the nails removed from fractures, which had developed a non-union, and in 5 out of 20 [25%] of fractures that had united, using both standard culture techniques and non-culture techniques. The bacterial isolates identified were mainly Staphylococcus epidermidis and the Gram-positive anaerobe Proprionibacterium acnes.

Vancomycin was the most effective antibiotic, with 2 out of 34 [6%] isolates being resistant. Erythromycin was the least effective, with 21 out of 34 [62%] isolates being resistant. Based on overall Minimum Bactericidal Concentrations at which 90% of all strains were killed, Vancomycin was the most active bactericidal agent tested followed in decreasing order by fucidic acid, ciprofloxacin, gentamicin, cefamandole and erythromycin.

Bacteria were detected more commonly in the fracture non-union group than in the union group [p< 0.01]. Of the antibiotic agents tested Vancomycin was the most effective and Erythromycin was the least effective.

Study Design: In a prospective study, intervertebral disc material from 64 patients undergoing discectomy for sciatica and 23 control patients was analysed for the presence of bacteria.

Objective: There have been many theories postulated as to the pathogenesis of back pain and sciatica. Possible inflammatory or auto-immune aetiologies have been suggested. Stirling et al (2001) suggested a possible link between sciatica and bacterial infection by demonstrating the presence of bacteria in disc material from 19 of 36 patients with severe sciatica. Previously, we developed methods for improved detection of bacterial infection associated with failed hip implants (Tunney et al 1999).These techniques have now been applied to the detection of bacteria in intervertebral discs from patients with sciatica.

Outcome Measures: Bacterial culture and non-culture immunofluorescence microscopy, using specific monoclonal antibodies, were applied to intervertebral disc material for the detection of bacterial infection. The results were also compared with functional scores before and after surgery.

Results: This study found that 20% (n=13) of patients suffering from sciatica had culture-positive disc material compared to 9% (n=2) of controls. The anaerobe Propionibacterium acnes was the predominant bacterium isolated in both case and control groups. Bacteria were also identified in skin, wound tissue and wound washings in some patients.

Conclusions: We are unable to demonstrate an association between sciatica and infection (p=0.335). This study suggests that bacteria detected in retrieved disc material may result from skin contamination during surgery.

Aim: The aim of the project was to discover if bacteria were implicated in non-union of fractures of the tibia and femur, which had been treated with intramedullary nailing.

Method: 40 intramedullary nails removed from tibial and femoral fractures were retrieved for the purpose of the study. 20 of these nails were from fractures, which had successfully united and were removed for mainly anterior knee pain or discomfort at screw sites. These nails formed the control group for the project. 20 nails were removed from fractures which had failed to unite prior to further operative intervention such as exchange nailing or the application of an Ilizarov frame. These fractures had no clinical evidence of infection and formed the study group for the project. The nails were subjected to ultrasound in the research laboratory to dislodge adherent bacterial formed as biofilm from the surface of the nail. Using both standard culture techniques and non-culture techniques, any dislodged bacteria were isolated and identified. Non-culture techniques involved the use of specific monoclonal antibody labelled immunofluorescence microscopy. Isolated bacteria were tested for the sensitivities of commonly used antibiotics in orthopaedic practice according to NCCLS guidelines.

Results: We discovered that bacteria were detected in up to 70% of the nails removed from fractures, which had failed to unite, using both standard culture and non-culture techniques. Also, we discovered that bacteria were detected in up to 30% of the nails removed from fractures that had united. The organisms identified were mainly the coagulase negative staphylococcus epidermidis and the gram-positive anaerobe proprionibacterium acnes. The antibiotics gentamicin, erythromycin, cefotaxime and cefomandole performed poorly against the isolated bacteria. Vancomycin, ciproxin and fucidin however performed better.

Conclusion: Bacteria formed as biofilm on intramedullary nails may have a significant role in the development of non-union fractures treated by this method. The bacteria isolated showed worrying resistance to commonly used antibiotics in orthopaedic practice, in particular, those used as prophylaxis.

Our aim was to determine if the detection rate of infection of total hip replacements could be improved by examining the removed prostheses. Immediate transfer of prostheses to an anaerobic atmosphere, followed by mild ultrasonication to dislodge adherent bacteria, resulted in the culture of quantifiable numbers of bacteria, from 26 of the 120 implants examined. The same bacterial species were cultured by routine microbiological techniques from only five corresponding tissue samples. Tissue removed from 18 of the culture-positive implants was suitable for quantitative tissue pathology and inflammatory cells were present in all samples. Furthermore, inflammatory cells were present in 87% of tissue samples taken from patients whose implants were culture-negative. This suggests that these implants may have been infected by bacteria which were not isolated by the techniques of culture used.

The increased detection of bacteria from prostheses by culture has improved postoperative antibiotic therapy and should reduce the need for further revision.