Intraoperative bacterial contamination in operations for joint replacement

Which regions of the operating gown should be considered most sterile?

Various guidelines have been proposed regarding which portions of a surgical gown may be considered sterile. Unfortunately, the validity of these recommendations has not been definitively established. We therefore evaluated gown sterility after major spinal surgery to assess the legitimacy of these guidelines. We used sterile culture swabs to obtain samples of gown fronts at 6-inch increments and at the elbow creases of 50 gowns at the end of 29 spinal operations. Another 50 gowns were swabbed immediately after they were applied to serve as negative controls. Bacterial growth was assessed using semiquantitative plating techniques on a nonselective, broad-spectrum media. Contamination was observed at all locations of the gown with rates ranging from 6% to 48%. Compared with the negative controls, the contamination rates were greater at levels 24 inches or less and 48 inches or more relative to the ground and at the elbow creases. The section between the chest and operative field had the lowest contamination rates. Based on these results, we consider the region between the chest and operative field to be the most sterile and any contact with the gown outside this area, including the elbow creases, should be avoided to reduce the risk of infection.

Self-Reinforced Ciprofloxacin-Releasing Polylactide-Co-Glycolide 80/20 Inhibits Attachment and Biofilm Formation by Staphylococcus Epidermidis

We have observed the efficiency of antibiotic-releasing polylactide-co-glycolide (PLGA) 80/20 in preventing Staphylococcus epidermidis attachment and biofilm formation in vitro. The aim of the present study was to evaluate the effect of self-reinforced (SR) implants with enhanced antibiotic release on bacterial attachment and biofilm formation rates, and also on growth inhibition of Staphylococcus epidermidis. Cylindrical SR-PLGA+AB specimens (length 30 mm, diameter 3 mm) were examined by scanning electron microscopy (SEM) for attachment of S. epidermidis ATCC 35989 on biomaterial surface and formation of biofilm, after incubating with bacterial suspension of ca. 10 cfu/mL for 1, 3, 7, 14 and 21 days. SR-PLGA and SR-PLGA+AB implants were tested on agar plates by measuring the inhibition distance around implants. On the surface of SR-PLGA+AB, at days 1, 3, 7, 14 and 21, the percentage of areas with not a single bacteria attached, was 88.6%, 71.1%, 73.7%, 73.7%, and 68.4%, respectively. On the areas where bacteria were detected, the number of bacterial cells remained low during whole study period, and no significant increase by time was seen. There was no biofilm observed on 97-99% of the examined areas during the whole study period on SR-PLGA+AB. In agar plates, the SR-PLGA+AB showed inhibition of bacterial growth, with (mean) 53.2 mm diameter of inhibition area with peeled implants and 50.5 mm with non-peeled implants. There was no inhibition seen around implants without ciprofloxacin. Bioabsorbable ciprofloxacin-releasing self-reinforced PLGA (SR-PLGA+AB) was superior to plain SR-PLGA in preventing bacterial attachment, biofilm formation, and also the growth of Staphylococcus epidermidis.

The microbiology of infected hip arthroplasty

Infection following joint replacement surgery although rare presents a challenging problem. Bacterial resistance to antibiotics is an emerging problem. We analysed the microbiology of 337 single-stage revisions for deep infection. Coagulase negative staphylococcus was found to be the predominant organism, although staphylococcus aureus is gaining importance. Gentamicin only provides cover for 64.1% of organisms. Resistance to this commonly used antibiotic prophylaxis is escalating. Fusidic acid and erythromycin provide improved cover. We would suggest on a microbiological basis that these antibiotics be considered for addition to acrylic bone cement. This will provide local antibiotic delivery when performing a revision for deep infection.

Should we use a separate knife for the skin?

The aim of this study was to re-assess whether the use of a ‘one-knife technique’ can be considered as safe as the alternative practice of using separate skin and inside knives for elective orthopaedic surgery. A total of 609 knife blades from 203 elective orthopaedic operations, with equal numbers of skin, inside and control blades, were cultured using direct and enrichment media. We found 31 skin blades (15.3%), 22 inside blades (10.8%), and 13 control blades (6.4%) gave bacterial growth.

Of the 31 contaminated skin blades only three (9.7%) had growth of the same organism as found on the corresponding inside blade. It is not known whether contamination of deeper layers in the remaining 90% was prevented by changing the knife after the skin incision. The organisms cultured were predominantly coagulase-negative staphylococci and proprionibacterium species; both are known to be the major culprits in peri-prosthetic infection. Our study suggests that the use of separate skin and inside knives should be maintained as good medical practice, since the cost of a single deep infection in human and financial terms can be considerable.

Infection in hip arthroplasty after previous injection of steroid

Immunosuppression following intra-articular injections of steroid into the hip may interfere with asepsis in a subsequent total hip arthroplasty (THA). We have undertaken a retrospective, matched, cohort study of infective complications after THA, in 40 patients who had received such an injection and 40 who had not. In the injection group there were five revisions, four of which were for deep infection. There were none in the matched group. The overall rate of revision in our database of 979 primary THAs was 1.02%. Six additional patients who had received injections underwent investigation for infection because of persistent problems in the hip as compared with one in the control group.

Perioperative contamination in primary total hip arthroplasty

All surgical procedures have the risk of microbial contamination. However, procedures in which prosthetic materials are involved have a high risk for future infectious problems because of the protection offered by the biofilm mode of growth. Studies of perioperative contamination have been done on involved surgical instruments, but whether these instruments transmit contamination to the prosthesis or future site of the prosthesis is not known. The aim of this study was to detect possible bacterial contamination in total hip arthroplasty through instruments that are used at the direct site of implantation during the primary procedure. Samples of the broaches used for preparing the acetabulum and femur, and samples of the reamed acetabular and femoral bone, were collected during 67 consecutive primary total hip arthroplasties in 67 patients. Broach samples were taken at the start and end of every reaming procedure. Four hundred two samples were taken, of which 26 were found to be positive for microorganisms. In 20 patients, at least one of these positive samples had been in direct contact with the actual prosthesis site, indicating that at least 30% of the involved patients had a possible bacterial contamination when leaving the operating theater.

LEVEL OF EVIDENCE

Diagnostic study, Level I-1 (testing of previously developed diagnostic criteria in series of consecutive patients--with universally applied reference gold standard). See the Guidelines for Authors for a complete description of levels of evidence.

Glove perforation and contamination in primary total hip arthroplasty

We conducted a randomised, controlled trial to determine whether changing gloves at specified intervals can reduce the incidence of glove perforation and contamination in total hip arthroplasty. A total of 50 patients were included in the study. In the study group (25 patients), gloves were changed at 20-minute intervals or prior to cementation. In the control group (25 patients), gloves were changed prior to cementation. In addition, gloves were changed in both groups whenever there was a visible puncture. Only outer gloves were investigated.

Contamination was tested by impression of gloved fingers on blood agar and culture plates were subsequently incubated at 37°C for 48 hours. The number of colonies and types of organisms were recorded. Glove perforation was assessed using the water test. The incidence of perforation and contamination was significantly lower in the study group compared with the control group. Changing gloves at regular intervals is an effective way to decrease the incidence of glove perforation and bacterial contamination during total hip arthroplasty.

Periprosthetic total joint infections: staging, treatment, and outcomes

Forty-three patients having 49 treatment protocols for periprosthetic total joint infections were staged prospectively, using an osteomyelitis classification system designed to stratify treatment selection according to patient risk factors. Implant salvage was possible in 66% of the infections treated within 30 days of the surgical procedure or within 14 days of symptom onset after a late, septic event. After debridement and implant removal, 88% of the patients with long-standing, refractory infections now have infection-free, functional reconstructions; 64% of these patients have a new, total joint replacement at the original site of treatment. All of the treatment failures, deaths, and amputations occurred in the high-risk patient cohorts prospectively identified within the staging system. Infection duration and the condition of the host are the two most important variables in predicting outcomes in patients with periprosthetic infections.

Prevention of infection with tobramycin-containing bone cement or systemic cefazolin in an animal model

We investigated in an animal model the efficacy of tobramycin-containing bone cement and systemic cefazolin for infection prophylaxis. In 18 female rabbits, the femoral cavity was inoculated with Staphylococcus aureus before injection of bone cement. The first group of six rabbits received tobramycin-containing Simplex-P bone cement. Two other groups of six rabbits received plain Simplex-P bone cement. Preoperatively, in one of the two latter groups cefazolin was administered intravenously. The other group served as untreated controls. The rabbits were monitored for clinical signs of infection. At 7 days' follow-up, the femora were harvested and cultures from the bone adjacent to the cement plug were quantified. Cultures from the rabbits which received antibiotic prophylaxis (either cefazolin systemically or tobramycin-containing bone cement) were all negative. In contrast, all rabbits in the untreated control group had positive cultures. These rabbits also had other signs of infection such as an elevated erythrocyte sedimentation rate and loss of body weight. Culture results were confirmed by the absence of bacterial DNA in the polymerase chain reaction hybridization assay. In conclusion, we found that both tobramycin-containing bone cement and systemic cefazolin are effective in preventing implant bed infection in rabbits up to 7 days after contamination with S. aureus.