José Cordero-Ampuero

PCR-hybridization after sonication improves diagnosis of implant-related infection

Purpose We wanted to improve the diagnosis of implant-related infection using molecular biological techniques after sonication. Methods We studied 258 retrieved implant components (185 prosthetic implants and 73 osteosynthesis implants) from 126 patients. 47 patients had a clinical diagnosis of infection (108 components) and 79 patients did not (150 components). The fluids from sonication of retrieved implants were tested in culture and were also analyzed using a modified commercial PCR kit for detection of Gram-positive and Gram-negative bacteria (GenoType BC; Hain Lifescience) after extraction of the DNA. Results 38 of 47 patients with a clinical diagnosis of infection were also diagnosed as being infected using culture and/or PCR (35 by culture alone). Also, 24 patients of the 79 cases with no clinical diagnosis of infection were identified microbiologically as being infected (4 by culture, 16 by PCR, and 4 by both culture and PCR). Comparing culture and PCR, positive culture results were obtained in 28 of the 79 patients and positive PCR results were obtained in 35. There were 21 discordant results in patients who were originally clinically diagnosed as being infected and 28 discordant results in patients who had no clinical diagnosis of infection. Interpretation For prosthetic joint infections and relative to culture, molecular detection can increase (by one tenth) the number of patients diagnosed as having an infection. Positive results from patients who have no clinical diagnosis of infection must be interpreted carefully.

Are Antibiotics Necessary in Hip Arthroplasty With Asymptomatic Bacteriuria? Seeding Risk With/Without Treatment

BackgroundIn patients with asymptomatic bacteriuria undergoing hip arthroplasty, the risk of prosthetic joint infection (PJI) and appropriateness of specific antibiotics are unclear.Questions/purposesWe determined (1) the prevalence of asymptomatic bacteriuria; and (2) the incidence of PJI in patients with asymptomatic bacteriuria managed with or without specific antibiotics.MethodsWe conducted a prospective, randomized study of all 471 patients without urinary symptoms receiving a total hip arthroplasty (THA; n = 228; average age 68 years; 122 female) or hemiarthroplasty (HA; n = 243; average age 85 years; 170 female) between April 2009 and November 2010. No patients were catheterized in the perioperative period and all received intravenous cefazolin (allergy, vancomycin) for 48 hours postoperatively. Urinalysis was conducted on all patients; if abnormal, a urine culture was performed. Patients with bacteriuria (> 100,000 colonies/mL cultured) were randomly assigned to receive specific antibiotics (Group A) or not (Group B). Minimum followup was 1 month including those six who died or were lost to followup (average, 10.4 months; range, 1–12 months).ResultsAsymptomatic bacteriuria occurred in eight of 228 patients undergoing THAs (three of eight with specific antibiotics) and 38 of 243 patients undergoing HAs (23 of 38 with specific antibiotics). Arthroplasty infection after 3 months occurred in one of 228 patients undergoing THAs and 12 of 243 patients undergoing HAs (six of 117 in Group A and six of 126 in Group B); bacteria cultured from the wound were dissimilar to those cultured in urine samples in any case. No patient presented signs of PJI by 1 year after the index surgery.ConclusionsWe identified no case of PJI from urinary origin in patients with asymptomatic bacteriuria whether or not they had been treated with specific antibiotics.Level of EvidenceLevel IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

In vitro susceptibility to antibiotics of staphylococci in biofilms isolated from orthopaedic infections

Prosthetic joint infections (PJIs) are related to the formation of biofilms, mainly by Staphylococcus aureus and Staphylococcus epidermidis. Therapy is usually selected according conventional susceptibility testing, but these data may be insufficient to detect the true antibiotic susceptibility in the biofilm. In total, 32 clinical strains (17 S. aureus and 15 S. epidermidis) isolated from patients with PJIs as well as 2 collection strains (S. aureus 15981 and S. epidermidis ATCC 35984) were tested against nine antibiotics commonly used in the treatment of PJIs (rifampicin, vancomycin, tigecycline, clindamycin, trimethoprim/sulfamethoxazole, ciprofloxacin, cloxacillin, daptomycin and fosfomycin) using the Calgary Biofilm Device. None of the antibiotics proved to be totally effective against biofilms in both species, with minimum biofilm eradication concentrations (MBECs) highly above the minimum inhibitory concentrations for most of the antibiotics (>1024 mg/L). Rifampicin and tigecycline showed MBECs slightly lower, mainly against S. epidermidis biofilms, and only two strains of this staphylococcal species were susceptible to almost all of the antibiotics tested. These results show that the search for new compounds with antimicrobial and antibiofilm properties is mandatory as well as the development of other strategies that could lead to the prevention and treatment of PJIs. In addition, more studies are necessary to obtain a better understanding of the mechanisms involved in antimicrobial resistance of biofilms.

Biofilm development by clinical isolates of Staphylococcus spp. from retrieved orthopedic prostheses.

Background Biofilms are considered the key factor in the development of implant-related infections. However, only a few reports have dealt with the ability of organisms isolated from such infections to develop biofilms in vitro. Methods We evaluated different phenotypic techniques (2 microtiter plate assays and confocal laser scanning microscopy (CLSM) and genotypic techniques (detection of the ica operon) related to biofilm development by clinical isolates of Staphylococcus spp. Results All 26 strains tested (from 23 specimens) were biofilm producers. Stepanovic test detected biofilm formation in 85% of the strains, microtiter plate assay in 65%, and CLSM in 39%. The ica operon was detected in 73% of all strains (all 13 S. aureus strains and 6 of the 13 coagulase-negative Staphylococcus strains). 7 ica-negative strains were biofilm-positive by phenotypic methods. Interpretation The detection of ica genes could not be related to the phenotypic ability of the strains to develop a biofilm in vitro, so both studies (genetic and phenotypic) are required for a better evaluation of the biofilm-producing ability of clinical strains of Staphylococcus isolated from orthopedic infections.

Low relapse with oral antibiotics and two-stage exchange for late arthroplasty infections in 40 patients after 2–9 years

Background and purpose Exchange surgery in late arthroplasty infection is directed against bacteria adhering to implants. Therapies based on antibiotics that are effective intracellularly have been proposed recently. We have combined both strategies to improve the cure rate. Methods 40 consecutive patients (16 hips, 24 knees) were diagnosed with late arthroplasty infection. The organisms isolated were 35 Staphylococcus, 19 of which were methicillin-resistant, 4 Enterococcus, 6 Gram-neg-ative bacilli, and 4 Corynebacterium. The infections were managed by a combined therapy consisting of two-stage exchange surgery and two oral intracellularly-effective antibiotics. The antibiotics were selected according to bacterial sensitivity and intracellular and biofilm effectiveness. Second re-implantation surgery was delayed until clinical and analytical normalization. Patients were in hospital for only 1 week after each surgery, and were followed up prospectively on an outpatient basis (2–9 years). Cure of the infection was defined as absence of clinical, serological, and radiographic signs of infection during the whole follow-up. Results The infection was resolved in 38/40 patients (15/16 hips and 23/24 knees). Interpretation Oral antibiotics that are effective intracellularly in combination with two-stage exchange surgery is a promising alternative for treating late arthroplasty infections. Oral antibiotics shorten hospitalization and reduce patient discomfort.

Treatment of prosthetic osteoarticular infections.

Introduction: Despite being relatively infrequent, prosthetic joint infections are a devastating medical complication. However, recent advances in surgical techniques, new antibiotics, and knowledge about pathogenic mechanisms have improved the outcome for affected patients. Areas covered: We have analyzed recent advances in pathogenesis, medical and surgical therapy of prosthetic joint infections, with special focus on new antibiotics useful for this disease. Recent studies focused on the important role of biofilms and intracellular bacteria in the pathogenesis of biomaterial-related infections. These advances must guide the management of the patients. Together with more classical antibiotics, linezolid and daptomycin have shown their usefulness for the treatment of these infections. Recently developed lipoglycopeptides have the potential to be used for these infections. In this sense, the possibility of treating patients with oral antibiotics without lack of efficacy is of great interest. Expert opinion: Individualized therapies that take into account the microbial etiology, pathogenesis of the disease, antimicrobial susceptibility, and efficacy of antibiotics against biofilms and intracellular organisms make it possible to treat even those infections caused by multidrug-resistant organisms. A multidisciplinary approach (including a surgeon, infectious diseases specialist and microbiologist) provides the best possible management of patients.

Sonication of Intramedullary Nails: Clinically-Related Infection and Contamination

Background and Aim: Sonication is currently considered the best procedure for microbiological diagnosis of implant-related osteoarticular infection, but studies in nail-related infections are lacking. The study aim was to evaluate implant sonication after intramedullary nail explantation, and relate it to microbiological cultures and clinical outcome. Patients and Methods: A study was performed in two University Hospitals from the same city. Thirty-one patients with implanted nails were prospectively included, whether with clinical infection (8 cases) or without (23 cases). Retrieved nails underwent sonication according a previously published protocol. The clinical and microbiological outcome patient was related to the presence of microorganisms in the retrieved implant. Results: Positive results appeared in 15/31 patients (9 with polymicrobial infections) almost doubling those clinically infected cases. The most commonly isolated organisms were Staphylococcus epidermidis (19.2 %) and Staphylococcus aureus (15.4 %). A significant relationship was found between the presence of positive cultures and previous local superficial infection (p=0.019). The presence of usual pathogens was significantly related to clinical infection (p=0.005) or local superficial infection (p=0.032). All patients with positive cultures showed pain diminution or absence of pain after nail removal (15/15), but this only occurred in 8 (out of 16) patients with negative cultures. Conclusions: In patients with previously diagnosed infection or local superficial infection, study of the hardware is mandatory. In cases where pain or patient discomfort is observed, nail sonication can help diagnose the implant colonization with potential pathogens that might require specific treatment to improve the final outcome.

In vitro susceptibility of Staphylococcus aureus and Staphylococcus epidermidis isolated from prosthetic joint infections

Prosthetic joint infections (PJI) are severe complications in Orthopedics, with Staphylococcus aureus and Staphylococcus epidermidis being the most commonly isolated pathogens. The variable antimicrobial susceptibility found in these microorganisms, along with the increasing number of methicillin-resistant strains, increases the difficulty of antibiotic selection and makes it necessary to perform individual susceptibility studies to select the optimal antibiotic treatment. The aim of this study was to evaluate the in vitro susceptibility pattern of 35 clinical strains isolated from PJI (17 S. aureus and 18 S. epidermidis) against rifampin, vancomycin, tygecicline, clindamycin, cotrimoxazole, cloxacillin, ciprofloxacin, daptomycin and fosfomycin. In vitro susceptibility assays were performed using the broth microdilution method and agar dilution for fosfomycin. MBC was also determined. Tygecicline and daptomycin showed the highest antimicrobial activity with low MIC90 values, and no resistant strains were detected. On the other hand, ciprofloxacin and cloxacillin exhibited a poor antimicrobial effect with a high percentage of nonsusceptible strains in both species. Bactericidal activity rates revealed the bacteriostatic behavior of rifampin, tygecicline, cotrimoxazole, fosfomycin and clindamycin, whereas vancomycin and cloxacillin showed species- and strain-dependent behavior. Daptomycin and ciprofloxacin were observed to be efficient bactericidal agents against the tested strains. According to our data, rifampin, tigecycline, daptomycin and fosfomycin showed high in vitro activity against most staphylococcal strains isolated from the PJIs tested, although daptomycin seems to be the best alternative to vancomycin therapy.

Girdlestone procedure: when and why

Girdlestone is one of the options for treating an infected hip arthroplasty (along with isolated antibiotics, debridement, and one or two-stage exchange). The choice must be based on a list of previous considerations. Results of girdlestone Major differences among different series are reported in literature: from 13% to 83% of patients are satisfied with the result. Healing of infection is attained in 80% to 100% of patients, but figures are worse in special subsets (rheumatoid arthritis, enterococcal and methicillin-resistant infections, or when cement is retained). Pain is reported as severe in 16% to 33% of patients, moderate in 24% to 53% and mild in 76%, while only some authors refer to “satisfactory pain relief”. Up to 45% of geriatric patients are unable to walk and only 29% walk independently. The literature reports Harris Hip scores from 25 to 64. Indications for girdlestone Absolute indications: non-ambulatory patients because of other problems or diseases, and impossible reimplantation (2nd-stage surgery) (unacceptable anaesthetic or surgical risk, technical difficulties, patient rejection). Relative indications Dementia (risk of dislocation vs. severely reduced walking ability), immunocompromise (up to what degree of immune impairment do we accept to take the risk?), intravenous drug abuse (how can you prove it?)

Reinforcement Rings for Deficient Acetabular Bone in Revision Surgery: Long-Term Results

This study analyzes the long-term results of 23 metal ring supports used in revision surgery since 1979. Only a metallic ring and a cemented cup were used in this series. Bone grafts and cementless cups were excluded from this study. One deep infection was excluded from the follow-up study. In the 22 cases analyzed, the mean follow-up period was 10 years for all cases and 12.2 years for unrevised cases. Bone defects according to the AAOS classification were: Grade 1, 1 case, Grade 2, 1 case, Grade 3, 10 cases, and Grade 4, 10 cases. A Müller ring was indicated in an anterior or medial wall defect (12 cases) and a Burch-Schneider ring was indicated in an anterior or posterior column defect or in pelvic discontinuity (10 cases). The clinical results were good in 8 cases, fair in 8 cases, and poor in 6 cases. Six cases were rerevised or removed, resulting in a total cumulative probability of rerevison or removal of 23.8% after 10 years according to the Kaplan-Meier analysis. Postoperatively, 18 cases had neutral rings, 2 cases had horizontal rings, and 2 cases had vertical rings. Radiological cup migration was found in 12 cases, resulting in a total cumulative probability of migration of 56.8% after 13 years according to the Kaplan-Meier analysis. Changes in the acetabular angle were present in 2 cases, vertical migration in 12 cases, and medial migration in 10 cases. Our data suggest that the metal ring and cemented cup alone could be used for salvage surgery in elderly patients and in low-demand patients. Possibly, adding bone graft could improve these results.