Adverse Trends in the Etiology of Orthopedic Infection: Results of 6-Year Monitoring of the Structure and Resistance of Leading Pathogens

Microbiological profile of patients with orthopedic implant-associated infection in the post-COVID period

Background. The etiological structure of implant-associated infection and antibiotic resistance of pathogens are important when choosing empirical antibiotic therapy. COVID-19 pandemic and increased consumption of antibiotics by the population could provoke an increase in antibiotic resistance.The aim of the work. To compare the spectrum of leading pathogens of implantassociated infection in the pre- and post-Covid period and to assess antibiotic resistance.Materials and methods. A continuous retrospective study of biomaterial samples from traumatology and orthopedic patients with implant-associated infection was carried out for 2018–2019 and 2021–2022. The sample consisted of 548 microorganism strains (n = 237 and n = 317, respectively) in 442 cases of infectious complications. The antibiotic resistance of all isolated microorganisms, including those from microbial associations, was assessed.Results. The leading pathogen of monomicrobial implant-associated infection in both study periods was Staphylococcus epidermidis (33–37 %). In 2021–2022, the proportion of microbial associations increased (from 12.5 to 17.5 %; p = 0.147) with the appearance of fungi in the microbial landscape. In the post-Covid period, the increase in Staphylococcus aureus resistance to tetracycline and doxycycline was revealed; the isolation of methicillin-resistant strains among Staphylococcus aureus decreased from 4 cases (out of 187) to 3 (out of 232); 100 % sensitivity to rifampicin and co-trimoxazole was maintained. An increase in Staphylococcus epidermidis resistance to all tested antibiotics was detected (statistically significant increase in resistance to fluoroquinolones; p = 0.002–0.003) with the isolation of methicillin-resistant strains in 80.5% and 80.9% of cases, respectively. All staphylococcal isolates were susceptible to vancomycin and linezolid. Enterobacteriaceae representatives showed a decrease in resistance to carbapenems and an increase in resistance to co-trimoxazole; in Pseudomonas aeruginosa and Acinetobacter baumannii, there is an increase in resistance to carbapenems and fluoroquinolones. All gram-negative microorganisms were sensitive to colistin.Conclusion. The high frequency of isolation of methicillin-resistant staphylococci determines the choice of vancomycin for empirical therapy. Increasing resistance of staphylococci to fluoroquinolones may limit their use. Increasing resistance of gram-negative bacteria and a narrow spectrum of antibiotics acting on carbapenemase producers may reduce the effectiveness of therapy.

Short-Term Outcomes of Phage-Antibiotic Combination Treatment in Adult Patients with Periprosthetic Hip Joint Infection

Implant-associated infections are the most costly problem in modern orthopedics due to the continued increase in the occurrence of antibiotic-resistant bacterial strains that requires the development of new effective antimicrobials. A non-randomized, prospective, open-label, with historical control study on the use of combined phage/antibiotic therapy of periprosthetic joint infection (PJI) was carried out. Forty-five adult patients with deep PJI of the hip joint were involved in the study, with a 12-month follow-up after one-stage revision surgery. Patients from a prospective study group (SG, n = 23) were treated with specific phage preparation and etiotropic antibiotics, whereas patients from a retrospective comparator group (CG, n = 22) received antibiotics only. The rate of PJI relapses in the SG was eight times less than that in the CG: one case (4.5%) versus eight cases (36.4%), p = 0.021. The response rate to treatment was 95.5% (95% confidence interval (CI) = 0.7511-0.9976) in the SG and only 63.6% (95% CI = 0.4083-0.8198) in the CG. The odds ratio for PJI relapse in patients of the SG was 0.083 (95% CI = 0.009-0.742), which was almost 12 times lower than that in the CG. The obtained results support the efficacy of the combined phage-antibiotic treatment of PJI.

[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.

Effects of bacteriophages on biofilms formed by Staphylococcus aureus isolated from patients with orthopedic infection

Objective. To study effects of bacteriophages on biofilm formation and formed biofilm by S. aureus isolated from patients with orthopedic infection. Materials and Methods. A total of 50 clinical strains of S. aureus were tested. Species identification was performed by MALDI-TOF MS, antibiotic susceptibility – in accordance with the EUCAST v21. Isolates susceptibility to bacteriophages «Sextafag» (Microgen, Russia) was determined by MPA medium. The antibacterial activity of phages against S. aureus ATCC 29213 and S. aureus ATCC 43300 was evaluated by growth kinetic curves. Biofilms of bacteriophage-sensitive S. aureus strains were formed according to the protocol described by O’Toole. Isolates were divided into categories in accordance with the Stepanovic criteria. The effects of bacteriophages on the formation of S. aureus biofilm were studied by co-incubation of phages and bacteria followed by calculation of the percentage inhibition relative to the control without the introduction of the phages. The effect of phages on 24-hour biofilms formed by staphylococci was also evaluated in comparison with the control. Results. Out of 50 clinical S. aureus strains studied, 43 isolates (86%) were susceptible to phages, including 22 MSSA and 21 MRSA. All phage-susceptible cultures were characterized by biofilm-forming ability of varying degree: 28% – weak biofilm producer, 35% – moderate, 37% – strong. Inhibition of biofilm formation was determined in all tested MRSA strains, while in 73% of isolates the index of biofilm formation inhibition was more than 80%, which exceeded this indicator for MSSA by 2.5 times. In turn, the destruction of the formed biofilm under the action of the bacteriophage was 72% for all S. aureus. In 57% of MSSA strains, the decrease in biofilm biomass in comparison with the control was more than 80%, while this indicator was 2 times higher than for MRSA. Conclusions. The results demonstrated a high in vitro efficacy of bacteriophages against biofilm formation in S. aureus.

Comparative analysis of pathogen structure in patients with PJI after primary total hip and knee arthroplasty

BACKGROUND

Microbiological profile of pathogens causing periprosthetic joint infection (PJI) after primary total hip (THA) and knee (TKA) arthroplasty varies in different regions, clinics and even departments. The objective of this study was to analyze the pathogen structure in patients with PJI after primary THA and TKA and its influence on the effectiveness of the infection eradication after two-stage reimplantation.

MATERIALS AND METHODS

We collected the retrospective data of 364 patients-161 with PJI after primary TKA (113 treated in two stages 48 with failure after spacer implantation) and 203 patients with infected THA (127 after successful two-stage reimplantation and 76 with PJI recurrence after the first stage) within the time period from January 2012 to December 2017, treated with two-stage protocol in the single center. A comparative analysis of pathogen structure was performed between cohorts of patients with hip and knee PJI. A subanalysis was made between the subsets comprised from patients with successful two-stage treatment and the subsets with failure to treat the infection.

RESULTS

Staphylococcus epidermidis was the most commonly identified pathogen in the full hip and knee cohorts: 30.1% and 32.5%, respectively. However, the percentage of methicillin-resistant Staphylococcus epidermidis (MRSE) among all S. epidermidis isolates was higher in the hip cohort-50% compared with 35% in the knee cohort (p = 0.073). Other coagulase-negative Staphylococci were more common to patients with PJI after primary TKA-10.3% compared with 5% (p < 0.02). Streptococcus sp. caused hip PJI in a larger percentage of cases than in knee PJI (p < 0.01)-7% and 2%, respectively (p < 0.01). Polymicrobial associations were significantly more common in hip PJI compared to knee PJI: 45.3% and 14% of cases, respectively (p < 0.001). The presence of polymicrobial infection significantly raised the risk of PJI recurrence [OR 2 (95% CI from 1.24 to 3.24)] in knee PJI patients and reduced the effectiveness of infection eradication from 73.9% to 47.8%.

CONCLUSION

Comparative analysis showed significant differences in the structure of PJI pathogens in the hip and knee. These findings are useful when choosing treatment strategies and empirical antibiotics regimens, in the management of patients with PJIs after primary hip and knee arthroplasty.

Short-term results of treatment of staphylococcal periprosthetic hip joint infection with combined antibiotics and bacteriophages treatment

Infectious complications after primary implantation of the hip joint are 0.5–3 %, and in the case of re-endoprosthetics, the risk of periprosthetic infection can reach 30 %. Also, we should not forget about the high percentage (16–20 %) of recurrence of periprosthetic infection of the hip joint, which leads to an unsatisfactory result of treatment up to amputation of a limb or even death of the patient. The reasons for the recurrence of the infectious process can be antibiotic resistance and antibiotic tolerance of microorganisms, as well as the ability of microorganisms to form biofilms on implants. In this regard, there is a constant need to search for alternative means of antimicrobial therapy, as well as to select the optimal ways of their delivery and deposition, which is of practical importance when performing surgical interventions in traumatology and orthopedics to protect the implantable structure from possible infection of the surgical site. One of the methods currently available to combat bacterial infections acquired antibiotic resistance and antibiotic tolerance is the use of natural viruses that infect bacterial bacteriophages. The above suggests a more effective suppression of periprosthetic infection, including persisters that deviate from antibiotics. It is, as a rule, associated with biofilms if used in conjunction with antibiotics and phages, when the use of bacteriophages predetermines the effectiveness of treatment. With the use of sensitive bacteriophages in the treatment of periprosthetic infections, a significant (p = 0.030) reduction in the rate of recurrence of infection (from 31 to 4.5 %) was observed. The use of lytic bacteriophages in traumatology and orthopedics is of great interest for phagotherapy of infections caused by antibiotic-resistant and biofilm-forming strains of bacteria. A clinical study using a single-stage surgical revision with simultaneous application of antibiotics and phages in the treatment of deep periprosthesis infection of the hip joint endoprosthesis, followed by 12 months follow-up for periprosthetic infection recurrence, demonstrated the effectiveness of the use of combined antibiotic and bacteriophages treatment.

Monitoring of the leading causative agents of osteomyelitis and their antibiotic resistance

The annual monitoring of the species composition of the causative agents of osteomyelitis, the identification of antibiotic-resistant strains, the study of the species composition of associations of microorganisms, their adhesive activity will prevent the spread of infection. Analyze the spectrum of the leading causative agents of osteomyelitis, their antibiotic sensitivity, and also the adhesive activity of the identified bacterial associations. A microbiological analysis of 2197 smears of adult patients with various etiological forms of osteomyelitis who were treated in the departments of the purulent center of the FSBI «NMRCTO» of the RF Ministry of Health in 2019. The spectrum of pathogenic microflora, sensitivity to standard antibacterial drugs used in the clinic was studied. The biofilm-forming ability of associations of microorganisms was investigated. According to the conducted microbiological monitoring for 2019, the microflora spectrum for osteomyelitis is diverse, the main pathogens are S. aureus, S. epidermidis, P. aeruginosa, K. pneumoniae, Enterococcus sp. A high percentage of isolation of microbial associations was noted, most often mix cultures of gram-positive and gram-negative bacteria. Bacterial associations: S. aureus + P. aeruginosa, S. aureus + S. marcescens, S. aureus + A. baumannii, S. epidermidis + E. cloacae - actively formed a biofilm on the surface of polystyrene plates, and the adhesive potential depended on interstrain relations in the composition of the formed biofilm. Among Gram-negative microflora, multiresistant strains prevail, among Gram-positive microflora - a high percentage of methicillin-resistant Staphylococci. When analyzing the antibiotic sensitivity of the isolated microorganisms, a high percentage of resistant strains is noted. So, with respect to enterobacteria, β-lactam antibiotics, drugs from the group of aminoglycosides, turned out to be ineffective. Among non-fermenting gram-negative bacteria, A. baumannii strains had multiple antimicrobial resistance. Among gram-positive microorganisms, a high percentage of isolation of methicillin-resistant staphylococci was noted. The specificity of the course of the disease and measures aimed at eliminating the pathogen depend on the species composition in the focus of infection. The study of the etiological structure of osteomyelitis, the monitoring of the antibiotic resistance of pathogens and their persistent potential, makes it possible to adopt sound tactics of conservative and surgical treatment.

[Microflora of surgical wounds and fistulas in patients with chronic osteomyelitis of the tibia before reconstructive treatment, in case of recurrence of infection.]

Relevance of microbiological monitoring in chronic osteomyelitis of the tibia developed during treatment of fractures with a plate is associated with a noticeable increase of various kinds of the microflora. A microbiological study was conducted of pathological material taken from wounds, fistulas and from the focus of inflammation in 49 patients with chronic tibial osteomyelitis, developed during treatment of fractures with a plate. The patients underwent sequestrectomy of the tibia and subsequent application of bilocal consecutive compression-distraction osteosynthesis or monolocal compression osteosynthesis. Microbiological study of smears taken before the reconstructive treatment from fistulas and wounds of patients showed that in monoculture there were 30 strains, the remaining 30 - as a part of 14 two - and three-component associations. The frequency of S. aureus strains was 55.3%, followed by coagulase-negative staphylococcus - 13.6% and representatives of the family Enterobacteriacae - 10.2%. There were methicillin-resistant strains of S. aureus in 11.8%, strains of coagulase-negative staphylococcus (MRCoNS) - 6.8%. Recurrence of the disease was observed in 7 patients. The microflora of the discharge from the fistula was represented by monocultures of S. aureus and associations of bacteria in which one of the components was methicillin-resistant strains of S. aureus. We observed differences in the contents of the microflora before reconstructive treatment of patients and in recurrence of infection. In case of recurrence of infection, the qualitative contents of the microflora changed: in 2 patients in the association of microorganisms and in 3 - in monocultures, S. aureus strains acquired resistance to ß-lactam antibiotics, new associations appeared, which were not present in primary cultures before reconstructive treatment. The study showed that the spectrum of micro-organisms in chronic osteomyelitis of the tibia, developed after osteosynthesis with a plate, varied and is subject to change and that dictates the need for microbiological monitoring to detect the etiological structure of pathogens, monitoring of antibiotic resistance of the isolated strains and rational approach to treatment of patients.