Peter Graber

Periprosthetic joint infection following Staphylococcus aureus bacteremia

OBJECTIVES The incidence of haematogenous periprosthetic joint infections (PJI) among patients with remote infections has been reported to be less than 1%. This incidence may be much higher in cases after documented Staphylococcus aureus bacteremia (SAB). We evaluated the incidence of haematogenous PJI following SAB in patients with previously uninfected arthroplasties. METHODS A retrospective analysis of our cohort including patients with SAB and prosthetic joints at the Basel University Medical Clinic Liestal from 1998 to 2008. RESULTS We identified 31 patients with 45 uninfected prosthetic joints in situ at the time of SAB. In 12 patients (39%) and 13 arthroplasties (29%), SAB caused PJI. In comparison to nosocomial SAB, infections occurred only in cases with community-acquired SAB (p=0.002). PJI was diagnosed within a median time of 2.5 days (IQR 1-3.5) after admission. The comparison between patients with and without PJI revealed no significant difference in gender, age, comorbidities and number of prostheses per patient and age of the prosthesis. CONCLUSIONS The rate of PJI after SAB is high, ranging from 30% to 40%, and clearly higher than rates reported for bacteremia with other pathogens. PJIs were observed in community-onset bacteremia, in which there is a typically delay from symptoms to antimicrobial treatment.

Clinical comparison between exogenous and haematogenous periprosthetic joint infections caused by Staphylococcus aureus

Patient-related risk factors for invasive Staphylococcus aureus infection overlap with those for periprosthetic joint infections (PJIs). We compared these factors and clinical characteristics between 17 exogenous and 40 haematogenous PJIs caused by S. aureus. Exogenous cases presented significantly more often with damaged periprosthetic soft tissue, whereas haematogenous cases more often had systemic signs of infection, such as fever, chills, and sepsis syndrome. However, comorbid conditions associated with S. aureus infection and/or PJIs did not differ between the two groups. These findings imply that patient-related risk factors for S. aureus infection do not help to predict the mode of infection acquisition in prosthetic joints.

Escherichia coli Variants in Periprosthetic Joint Infection: Diagnostic Challenges with Sessile Bacteria and Sonication

ABSTRACT The diagnostic yield of prosthetic joint-associated infection is hampered by the phenotypic change of bacteria into a sessile and resistant form, also called biofilm. With sonication, adherent bacteria can be dislodged from the prosthesis. Species identification may be difficult because of their variations in phenotypic appearance and biochemical reaction. We have studied the phenotypic, genotypic, and biochemical properties of Escherichia coli variants isolated from a periprosthetic joint infection. The strains were collected from synovial fluid, periprosthetic tissue, and fluid from the explanted and sonicated prosthesis. Isolates from synovial fluid revealed a normal phenotype, whereas a few variants from periprosthetic tissue and all isolates from sonication fluid showed different morphological features (including small-colony variants). All isolates from sonication fluid were beta-galactosidase negative and nonmotile; most were indole negative. Because of further variations in biochemical properties, species identification was false or not possible in 50% of the isolates included in this study. In contrast to normal phenotypes, variants were resistant to aminoglycosides. Typing of the isolates using pulsed-field gel electrophoresis yielded nonidentical banding patterns, but all strains were assigned to the same clonal origin when compared with 207 unrelated E. coli isolates. The bacteria were repeatedly passaged on culture media and reanalyzed. Thereafter, most variants reverted to normal phenotype and regained their motility and certain biochemical properties. In addition, some variants displayed aminoglycoside susceptibility after reversion. Sonication of an explanted prosthesis allows insight into the lifestyle of bacteria in biofilms. Since sonication fluid also reveals dislodged sessile forms, species identification of such variants may be misleading.

Risk Factors for Periprosthetic Ankle Joint Infection: A Case-Control Study

BACKGROUND Periprosthetic ankle joint infection is a feared complication of total ankle arthroplasty because the implant fails in the majority of cases. However, risk factors for developing these infections are unknown. METHODS We aimed to determine risk factors for infection in a matched case-control study that included twenty-six patients with periprosthetic ankle joint infection and two control groups, each consisting of fifty-two patients. RESULTS The prevalence of periprosthetic ankle joint infection within our cohort was 4.7%. Four infections (15%) had a hematogenous origin and twenty-two (85%), an exogenous origin. Staphylococcus aureus was the most common pathogen, followed by coagulase-negative staphylococci. Preoperative predisposing factors associated with infection included prior surgery at the site of infection (odds ratio [OR] = 4.56, 95% confidence interval [CI] = 0.98 to 21.35, and OR = 4.78, 95% CI = 1.53 to 14.91, in comparison with the two control groups) and a low American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot score (35.8 versus 49.8 and 47.6 in the two control groups, p ≤ 0.02). The mean duration of the index surgery was significantly longer in the case group than in both control groups (119 versus eighty-four and ninety-three minutes, p ≤ 0.02). After surgery, persistent wound dehiscence (OR = 15.38, 95% CI = 2.91 to 81.34, p = 0.01, in comparison with both control groups) and secondary wound drainage (OR = 7.00, 95% CI = 1.45 to 33.70, and OR = 5.31, 95% CI = 1.01 to 26.78, in comparison with the two control groups, p ≤ 0.04) were associated with the development of a periprosthetic ankle joint infection. CONCLUSIONS Patients at risk for periprosthetic ankle joint infection following total ankle arthroplasty include those with a history of surgery on the ankle, a low preoperative AOFAS hindfoot score, and a long operative time. Postoperatively, patients with a prolonged wound dehiscence or a secondary wound-healing problem are also at risk for infection.

Mycoplasma pneumoniae infection complicated by severe mucocutaneous lesions

A 38-year-old man presented with a 5-day history of productive cough, headache, and fever. He complained of mouth and throat soreness and painful lip lesions. His medical history was unremarkable. Physical examination revealed severe conjunctivitis (fi gure, A), swollen, crusted lips, and pseudomembranous lesions in the oropharynx (fi gure, B). Blood, sputum, and urine cultures, urinary antigen test for Legionella pneumophila, and antibody tests for HIV and Mycoplasma pneumoniae were negative. On lung auscultation, bilateral whistling rales were detected. Chest radiograph demonstrated prominent peribronchial cuffi ng, and bronchoscopy showed extensive ulcerative endobronchial lesions and purulent bronchitis. PCR from bronchoalveolar lavage fl uid was, however, positive for M pneumoniae, and seroconversion was documented 10 days later. Despite antimicrobial therapy with clarithromycin (250 mg twice a day), his condition worsened, and new target lesions on the scrotal skin (fi gure, C), as well as erosive lesions on the anal mucosa and the glans penis (fi gure, D) evolved 48 h after admission. Based on the clinical presentation, StevensJohnson syndrome secondary to M pneumoniae infection was diagnosed, and a short-course treatment with corticosteroid initiated. Symptoms resolved completely within 3 weeks, and the patient is in good health after a follow-up of 12 months. Stevens-Johnson syndrome is characterised by erythematous target lesions on the skin, and bullous or erosive lesions on mucous membranes in systemically ill patients. Oral mucosa, lips, and conjunctivae are particularly involved. There is no uniform defi nition for this syndrome, and overlap with erythema multiforme and toxic epidermal necrolysis has been recognised. Drugs and infections, most commonly M pneumoniae, are well-known precipitating factors. Histopathological fi ndings, such as perivasculitis and necrosis of the epidermis, are similar in Stevens-Johnson syndrome and toxic epidermal necrolysis, but diff er from erythema multiforme. Treatment remains supportive and symptomatic. The role of corticosteroids is controversial, but may hasten the resolution of Stevens-Johnson lesions.

Streptococcus agalactiae in Relapsing Cellulitis

To the Editor—We read with interest the report by Del Giudice et al. [1] about a case of relapsing erysipelas caused by Streptococcus agalactiae. Molecular analyses of the strains, which were isolated from skin and vaginal specimens during 2 episodes, revealed identical restriction patterns, leading the authors to suggest that vaginal carriage of S. agalactiae served as a reservoir for relapsing skin infection. Nevertheless, the detailed pathogenesis of relapsing cellulitis/erysipelas has not been fully elucidated. We report a case of fasciitis that was followed by 4 episodes of cellulitis, and we discuss an additional mechanism of recurrence. A 38-year-old, previously healthy woman presented with fever, chills, and severe pain in the left leg. Clinical examination of the extremity revealed edematous erythema with pronounced tenderness. MRI delineated a fluid collection between the subcutaneous tissue and the fascia. Wide debridement was performed immediately, and intravenous antimicrobial treatment (amoxicillinclavulanate, 2.2 g 3 times per day, plus clindamycin, 600 mg 3 times per day) was administered. Gram-positive cocci in chains were abundant throughout the tissue specimens, but they failed to grow on culture. Broad-spectrum PCR and blood culture results remained negative. The patient’s subsequent clinical course was favorable, but lymphedema persisted at the infection site. During the subsequent 2 years, cellulitis occurred in the same area 4 times (7, 15, 17, and 24 months after the occurrence of fasciitis). S. agalactiae grew in blood cultures during the first and fourth episodes of cellulitis and from a vaginal swab culture during the third episode of cellulitis. Extensive investigations, including echocardiography, gynecological, and immunological examinations, revealed neither the source of bacteremia nor evidence of primary or secondary immunosuppression. The infections resolved after 8–14 days of intravenous penicillin (plus aminoglycosides during 2 episodes). After the third episode, a 5-month prophylactic course of amoxicillin (750 mg 3 times per day) was initiated. Two months after completion of the amoxicillin regimen, the cellulitis relapsed. SmaI digestion of the strains isolated from the vagina (third episode) and blood (fourth episode), followed by PFGE, revealed identical restriction patterns. The patient is currently being treated with a second course of long-term oral prophylaxis. Our case and the reported cases of relapsing cellulitis/erysipelas due to S. agalactiae involved a skin region affected by chronic lymphedema [1–3], which is strongly associated with recurrent streptococcal infection [4]. Lymphatic tissue alterations may lead to locally impaired immune responses and insufficient bacterial clearance. Therefore, spread from vaginal colonization may not be the only explanation for multiple relapses. In situ persistence of microorganisms in nonprofessional phagocytes can cause relapsing infection, as shown with Staphylococcus aureus [5, 6]. Furthermore, analyses of biopsy specimens obtained from persons with severe soft-tissue infection have revealed significant amounts of viable Streptococcus pyogenes, despite the administration of antibiotics, up to 14 days after disease onset [7]. Group B streptococci can interact with extracellular matrix components of eukaryotic cells and may invade fibroblasts and epithelial and endothelial cells [8]—findings that could support our hypothesis of in situ persistence. This does not conflict with the results of the study by Del Giudice et al. [1], but it might contribute an additional possible mechanism in recurrent cellulitis/erysipelas. Intracellular persistence of viable group A streptococci in erysipelas is currently being analyzed at our center [9].

The treatment and outcome of peri-prosthetic infection of the ankle: a single cohort-centre experience of 34 cases

The treatment of peri-prosthetic joint infection (PJI) of the ankle is not standardised. It is not clear whether an algorithm developed for hip and knee PJI can be used in the management of PJI of the ankle. We evaluated the outcome, at two or more years post-operatively, in 34 patients with PJI of the ankle, identified from a cohort of 511 patients who had undergone total ankle replacement. Their median age was 62.1 years (53.3 to 68.2), and 20 patients were women. Infection was exogenous in 28 (82.4%) and haematogenous in six (17.6%); 19 (55.9%) were acute infections and 15 (44.1%) chronic. Staphylococci were the cause of 24 infections (70.6%). Surgery with retention of one or both components was undertaken in 21 patients (61.8%), both components were replaced in ten (29.4%), and arthrodesis was undertaken in three (8.8%). An infection-free outcome with satisfactory function of the ankle was obtained in 23 patients (67.6%). The best rate of cure followed the exchange of both components (9/10, 90%). In the 21 patients in whom one or both components were retained, four had a relapse of the same infecting organism and three had an infection with another organism. Hence the rate of cure was 66.7% (14 of 21). In these 21 patients, we compared the treatment given to an algorithm developed for the treatment of PJI of the knee and hip. In 17 (80.9%) patients, treatment was not according to the algorithm. Most (11 of 17) had only one criterion against retention of one or both components. In all, ten of 11 patients with severe soft-tissue compromise as a single criterion had a relapse-free survival. We propose that the treatment concept for PJI of the ankle requires adaptation of the grading of quality of the soft tissues.

Multiple opportunistic infections after high-dose steroid therapy for giant cell arteritis in a patient previously treated with a purine analog

We present the case of a 74-y-old HIV-negative female who suffered simultaneously from multiple opportunistic infections and a Klebsiella pneumoniae sepsis during high-dose steroids for giant cell arteritis. The patient was treated with a purine analog due to hairy cell leukaemia 10 y previously. Purine analog therapy can lead to long lasting defects in cell-mediated immunity. In these patients, treatment with steroids should be closely monitored with CD4 counts.

Debridement and implant retention in the management of hip periprosthetic joint infection: outcomes following guided and rapid treatment at a single centre

Aims To analyse the effectiveness of debridement and implant retention (DAIR) in patients with hip periprosthetic joint infection (PJI) and the relationship to patient characteristics. The outcome was evaluated in hips with confirmed PJI and a follow‐up of not less than two years. Patients and Methods Patients in whom DAIR was performed were identified from our hip arthroplasty register (between 2004 and 2013). Adherence to criteria for DAIR was assessed according to a previously published algorithm. Results DAIR was performed as part of a curative procedure in 46 hips in 42 patients. The mean age was 73.2 years (44.6 to 87.7), including 20 women and 22 men. In 34 hips in 32 patients (73.9%), PJI was confirmed. In 12 hips, the criteria for PJI were not fulfilled and antibiotics stopped. In 41 (89.1%) of all hips and in 32 (94.1%) of the confirmed PJIs, all criteria for DAIR were fulfilled. In patients with exogenous PJI, DAIR was performed not more than three days after referral. In haematogenous infections, the duration of symptoms did not exceed 21 days. In 28 hips, a single debridement and in six hips two surgical debridements were required. In 28 (87.5%) of 32 patients, the total treatment duration was three months. Failure was noted in three hips (9%). Long‐term follow‐up results (mean 4.0 years, 1.4 to 10) were available in 30 of 34 (88.2%) confirmed PJIs. The overall successful outcome rate was 91% in 34 hips, and 90% in 30 hips with long‐term follow‐up results. Conclusion Prompt surgical treatment with DAIR, following strict diagnostic and therapeutic criteria, in patients with suspected periprosthetic joint infection, can lead to high rates of success in eradicating the infection.

Multidrug-resistant Providencia stuartii expressing extended-spectrum β-lactamase PER-1, originating in Kosovo

triple-base-pair mutation involved in the high-level tetracycline resistance in H. pylori, whereas nucleotide 1054 contacts the A-site tRNA. In contrast, the G346A mutation is located in a 16S rRNA region not closely associated with tetracycline binding. For M. pneumoniae, two mutations were found in the brothselected mutants and were associated with 2to 16-fold increases in MICs of the three tetracyclines studied, in comparison with those of the parental strain FH. The two mutations described for this species, G1193A and T968C, are located very close to or contact the primary tetracycline binding site, respectively. In summary, this is the first description of mutations in 16S rRNA associated with decreased susceptibility to tetracyclines in human mycoplasmas. However, what real effect these new mutations have on the tetracycline susceptibility of both mycoplasmas has yet to be determined.