Orthopedic implant-associated infection: the main etiological agents, local resistance and antimicrobial therapy recommendations

[Possible routes of infection in hip replacement]

OBJECTIVE

To evaluate the probability of direct inoculation of pathogens into the bone bed by surgical instruments and implants.

MATERIAL AND METHODS

The study included 22 patients who underwent surgery at the Vreden National Medical Research Center of Traumatology and Orthopedics. Mean age was 73.3±3.7 years. These patients underwent total hip replacement. Intraoperative skin scrapings within the wound edge were made. Pressure on the scalpel was applied in two fashions. In 10 cases, scraping was performed by minimally pressure on the skin (superficial contact). In 12 cases, scalpel was pressed with force (skin deformation to a depth of 3-4 mm). Next, microbiological analysis of scrapings was performed.

RESULTS

There was no growth of microorganisms in samples obtained by minimal pressure on the scalpel. Analysis of 12 scrapings in the second group (tight contact simulating damage to the skin with surgical instruments) revealed growth of microflora in all cases.

CONCLUSION

Contact of cutters, rasps and implants with skin can be a mechanism for direct inoculation of pathogens into the bone tissue and potentially cause periprosthetic infection.

Important Aspects of Staging of Biofilm’s Formation and Justification of Time Intervals of Conduction of Prophylactics of Infectious Complications

In this article there are presented materials regarding problems of infectious complications, that appear as the result of formation of microbial biofilms, which is especially actual in medical practice nowadays because of wide usage of different invasive materials in surgical and traumatological and orthopedical departments of clinics. Classifications, which are based on works of many authors, of surgical infections are given, and also of pathogens, known nowadays, of which Staphylococcus aureus и S. epidermidis are superior. Stages of process and laboratory-experimental proven time intervals and special features of biofilm’s formation are determined, which points to an importance and perspectivity of prophylaxis of infectious complications at moments of contaminations and primary adhesion. In light of usage in implantational surgery of constantly advancing materials, the contemplation is necessary of biofilmforming features of known pathogenic and opportunistic bacterias and potentially dangerous, in particular, pathogens that lead to generalization of process.

[PCR research as an auxiliary method for diagnostics of periphresitical infection after endostreditision of joints (clinical case).]

Periprosthetic infection (PPI) after arthroplasty of large joints is the third (among the main causes of unsatisfactory results of surgical treatment) a serious threat to the health of patients. The «gold standard» for the diagnosis of PPI is the bacteriological examination of samples of periprosthetic tissues and synovial fluid. In 10-30% of cases, it is impossible to isolate microorganisms, which is explained by the difficulty of cultivation and taking antibiotics before sampling. The purpose of study is to demonstrate the diagnostic value of PCR diagnostics for identifying the genetic material of an infectious pathogen of a culture-negative periprosthetic infection. Material of the study is a description of a clinical case of a culture-negative periprosthetic infection that caused a second two-stage revision of the hip joint prosthesis In the first episode of PPI that occurred 3 years after hip replacement, a microbiological examination of the puncture of the trochanteric zone of the operated joint revealed a massive increase in methicillin-resistant Staphylococcus epidermidis (MRSE). A two-stage revision joint replacement was performed. 5 years after the revision, the patient was hospitalized with clinical and radiological signs of PPI, while examining the puncture of the joint revealed characteristic PPI cytosis. Microbiological examination of punctate and intraoperative aspirate at the first stage of the repeated two-stage revision endoprosthesis replacement did not reveal aerobic and anaerobic microorganisms. In PCR studies, the DNA of methicillin-sensitive Staphylococcus aureus (MSSA) was detected in washouts from the removed components of the endoprosthesis; no resistance marker (mecA gene) was found. Given the concomitant oncological disease, this result determined the appointment of pathogenetic antibiotic therapy, the effectiveness of which was confirmed after 8 weeks at the II stage of revision. The PCR study of joint and trochanteric punctures (before surgery), flushing from the removed spacer components (after ultrasound treatment) and intraoperative aspirate from the joint did not reveal Staphylococcus aureus DNA and resistance marker (mecA gene). In some cases of periprosthetic infection, traumatologists and orthopedists deal with culturally negative results of a microbiological study of the patient's biomaterial and swabs from the components of endoprostheses in the presence of clinical manifestations of PPI, confirmed by laboratory diagnostics and X-ray examination. According to the literature, such clinical situations are observed in 10-30% of cases and are caused by previous antibiotic therapy in the early stages of an infectious complication. After surgical treatment of PPI for the selection of adequate antibiotic therapy, such patients need to at least indirectly determine the type of infection pathogen, which is achieved by the use of additional diagnostic methods, such as a PRC study. In the case described by us, after a course of antibiotic therapy, prescribed according to the results of the first PCR study, the patient's body does not contain DNA traces of the desired infectious agent. Thus, the repeated PCR not only confirmed the accuracy of the initial diagnosis of the source of infection, but also further illustrated the success of the rehabilitation of the periprosthetic infection using a correctly selected antibacterial drug at the previous stage of the study. The use of the PCR method made it possible to diagnose the pathogen and prescribe adequate antibiotic therapy for culture-negative periprosthetic infection.