Laboratory diagnosis of bone, joint, soft-tissue, and skin infections

Clinical Practice Guideline by the Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA): 2023 Guideline on Diagnosis and Management of Acute Bacterial Arthritis in Pediatrics

This clinical practice guideline for the diagnosis and treatment of acute bacterial arthritis (ABA) in children was developed by a multidisciplinary panel representing the Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA). This guideline is intended for use by healthcare professionals who care for children with ABA, including specialists in pediatric infectious diseases and orthopedics. The panel's recommendations for the diagnosis and treatment of ABA are based upon evidence derived from topic-specific systematic literature reviews. Summarized below are the recommendations for the diagnosis and treatment of ABA in children. The panel followed a systematic process used in the development of other IDSA and PIDS clinical practice guidelines, which included a standardized methodology for rating the certainty of the evidence and strength of recommendation using the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation) (see Figure 1). A detailed description of background, methods, evidence summary and rationale that support each recommendation, and knowledge gaps can be found online in the full text.

Radiometal chelators for infection diagnostics

Infection of native tissues or implanted devices is common, but clinical diagnosis is frequently difficult and currently available noninvasive tests perform poorly. Immunocompromised individuals (for example transplant recipients, or those with cancer) are at increased risk. No imaging test in clinical use can specifically identify infection, or accurately differentiate bacterial from fungal infections. Commonly used [18F]fluorodeoxyglucose (18FDG) positron emission computed tomography (PET/CT) is sensitive for infection, but limited by poor specificity because increased glucose uptake may also indicate inflammation or malignancy. Furthermore, this tracer provides no indication of the type of infective agent (bacterial, fungal, or parasitic). Imaging tools that directly and specifically target microbial pathogens are highly desirable to improve noninvasive infection diagnosis and localization. A growing field of research is exploring the utility of radiometals and their chelators (siderophores), which are small molecules that bind radiometals and form a stable complex allowing sequestration by microbes. This radiometal-chelator complex can be directed to a specific microbial target in vivo, facilitating anatomical localization by PET or single photon emission computed tomography. Additionally, bifunctional chelators can further conjugate therapeutic molecules (e.g., peptides, antibiotics, antibodies) while still bound to desired radiometals, combining specific imaging with highly targeted antimicrobial therapy. These novel therapeutics may prove a useful complement to the armamentarium in the global fight against antimicrobial resistance. This review will highlight current state of infection imaging diagnostics and their limitations, strategies to develop infection-specific diagnostics, recent advances in radiometal-based chelators for microbial infection imaging, challenges, and future directions to improve targeted diagnostics and/or therapeutics.

Stain-free Gram staining classification of pathogens via single-cell Raman spectroscopy combined with machine learning

Gram staining (GS) is one of the routine microbiological operations to classify bacteria based on the cell wall structure. Accurate GS classification of pathogens is of great significance since it helps correct administration of antimicrobial treatment. The laborious procedure and low sensitivity results related to conventional GS have resulted in reluctance among clinicians. In this study, we integrate confocal Raman spectroscopy and machine learning techniques to distinguish Gram-negative (GN) or Gram-positive (GP) bacteria. A single-cell Raman database including seven most common clinical pathogens (three GP strains and four GN strains) was constructed. Machine learning algorithms including the support-vector machine (SVM), k-nearest neighbors' algorithm (k-NN), gradient boosting machine (GBM), linear discriminant analysis (LDA), and t-distributed stochastic neighbor embedding (t-SNE) were trained to achieve the binary classification for GS. With such a relatively small database, the SVM model achieved the highest accuracy of 98.1%. The molecular signatures of GN and GP embedded in their Raman fingerprints were identified with hierarchical cluster analysis (HCA). The results indicated that Raman peaks for peptidoglycan and teichoic acid were the most significant factors that contributed to accurate classification. The Raman machine learning approach could greatly enhance the diagnosis of pathogenic infections.

Clinical Practice Guideline by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America: 2021 Guideline on Diagnosis and Management of Acute Hematogenous Osteomyelitis in Pediatrics

This clinical practice guideline for the diagnosis and treatment of acute hematogenous osteomyelitis (AHO) in children was developed by a multidisciplinary panel representing Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA). This guideline is intended for use by healthcare professionals who care for children with AHO, including specialists in pediatric infectious diseases, orthopedics, emergency care physicians, hospitalists, and any clinicians and healthcare providers caring for these patients. The panel's recommendations for the diagnosis and treatment of AHO are based upon evidence derived from topic-specific systematic literature reviews. Summarized below are the recommendations for the diagnosis and treatment of AHO in children. The panel followed a systematic process used in the development of other IDSA and PIDS clinical practice guidelines, which included a standardized methodology for rating the certainty of the evidence and strength of recommendation using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach. A detailed description of background, methods, evidence summary and rationale that support each recommendation, and knowledge gaps can be found online in the full text.

Diagnostic concordance of clinical diagnosis, tissue culture, and histopathology testing for skin and soft tissue infections: A single-center retrospective study

BACKGROUND

Tissue culture and histopathology are the conventional diagnostic modalities for skin and soft tissue infections (SSTIs), but few studies have investigated their concordance.

OBJECTIVE

Determine concordance between histopathology and tissue culture in the diagnosis of suspected SSTIs.

METHODS

Single-center retrospective study of 355 cases with suspected SSTIs identified from the dermatology inpatient consultation log January 2014-July 2017.

RESULTS

Overall concordance between histopathology testing and tissue culture results was high (76.1%). Concordance was high for cases defined as no evidence of infection, fungal infection and mycobacterial infection by histopathology (77.8%, 74.2%, and 80.0%) and tissue culture (92.1%, 67.7%, and 83.3%). Concordance was lower for suspected SSTIs with bacterial infection by histopathology (61.9%) and tissue culture (28.4%). Concordance rates were not significantly affected by age, sex, race, antimicrobial agent use, immunologic status, or biopsy size.

LIMITATIONS

Retrospective and single-institution nature of the study.

CONCLUSION

This study demonstrated a high concordance between histopathology and tissue culture in SSTIs with no clinical evidence of infection and suspected fungal and mycobacterial SSTIs, though concordance was lower for suspected SSTIs with evidence of bacterial infection. Clinicians should not be deterred from relying on initial histopathological results based on patients' immunosuppressed status, antimicrobial agent use, age, or biopsy tissue size.

Metagenomic Next-Generation Sequencing Improves Diagnosis of Osteoarticular Infections From Abscess Specimens: A Multicenter Retrospective Study

Background: We conducted this retrospective study to reveal the accuracy of metagenomic next-generation sequencing (mNGS) for diagnosing osteoarticular infections from fresh abscess specimens obtained from patients in an HIV-naive population.

Methods: We retrospectively analyzed hospital records at three participating TB-specialized hospitals for patients admitted with suggestive diagnoses of osteoarticular tuberculosis between January 2018 and August 2019. Abscess specimens obtained from each patient were tested via pathogen culture, GeneXpert Mycobacterium tuberculosis (MTB)/rifampicin (RIF), and mNGS assay.

Results: A total of 82 abscess samples were collected from patients with osteoarticular infections, including 53 cases with (64.6%) bacterial, 21 (25.6%) with mycobacterial, 7 (8.5%) with fungal, and 1 (1.2%) with actinomycetal organisms detected. Analysis of mNGS assay results identified potential pathogens in all cases, with M. tuberculosis complex (MTBC) most frequently isolated, followed by Staphylococcus aureus and Brucella melitensis. Conventional culture testing identified causative pathogens in only 48.4% of samples, a significantly lower rate than the mNGS pathogen identification rate (100%, p < 0.01). Culture-positive group specimens yielded significantly greater numbers of sequence reads than did culture-negative group specimens (p < 0.01). Of patients receiving surgical interventions and mNGS-guided treatment, 76 (92.7%) experienced favorable outcomes by the time of follow-up assessment at 3 months post-treatment. Notably, MTBC detection in two patients experiencing treatment failure suggests that they had mixed infections with MTBC and other pathogens.

Conclusion: Results presented here demonstrate that mNGS has a greater pathogen detection rate in osteoarticular infections than conventional culture-based methods.

New synthesis of 6″-[18 F]fluoromaltotriose for positron emission tomography imaging of bacterial infection

6″-[18 F]fluoromaltotriose is a positron emission tomography tracer that can differentiate between bacterial infection and inflammation in vivo. Bacteria-specific uptake of 6″-[18 F]fluoromaltotriose is attributed to the targeting of maltodextrin transporter in bacteria that is absent in mammalian cells. Herein, we report a new synthesis of 6″-[18 F]fluoromaltotriose as a key step for its clinical translation. In comparison with the previously reported synthesis, the new synthesis features unambiguous assignment of the fluorine-18 position on the maltotriose unit. The new method utilizes direct fluorination of 2″,3″,4″-tri-O-acetyl-6″-O-trifyl-α-D-glucopyranosyl-(1-4)-O-2',3',6'-tri-O-acetyl-α-D-glucopyranosyl-(1-4)-1,2,3,6-tetra-O-acetyl-D-glucopyranose followed by basic hydrolysis. Radiolabeling of the new maltotriose triflate precursor proceeds using a single HPLC purification step, which results in shorter reaction time in comparison with the previously reported synthesis. Successful synthesis of 6″-[18 F]fluoromaltotriose has been achieved in 3.5 ± 0.3% radiochemical yield (decay corrected, n = 7) and radiochemical purity above 95%. The efficient radiosynthesis of 6″-[18 F]fluoromaltotriose would be critical in advancing this positron emission tomography tracer into clinical trials for imaging bacterial infections.

Microbiological profile of chronic osteomyelitis with special reference to anaerobic osteomyelitis in a tertiary care hospital of coastal Karnataka

Chronic osteomyelitis is a relapsing, persistent, low-grade inflammation of bone caused by various infectious agents. The present study, conducted over a two-year period, on specimens received from cases of chronic osteomyelitis was, to determine the frequency of isolation of aerobic and anaerobic bacteria and to analyse their antimicrobial susceptibility pattern. Specimens were processed for Gram stain, aerobic and anaerobic culture, and were identified according to standard techniques. Significant growth was observed in 102/204 specimens, in which aerobic growth was observed in 62 (60.8%) and anaerobic in 40 (39.2%). Resistance to metronidazole and clindamycin was observed in 6.7% and 30% of the anaerobic isolates, respectively. None of these were resistant to meropenem. A significant proportion of anaerobic isolates were found to be resistant to commonly used empirical drugs, such as clindamycin, thus necessitating a need for routine anaerobic susceptibility testing.

A systematic review on current osteosynthesis-associated infection animal fracture models

Objective

Osteosynthesis-associated infection is a challenging complication post fracture fixation, burdening the patients and the orthopaedic surgeons alike. A clinically relevant animal model is critical in devising new therapeutic strategies. Our aim was to perform a systematic review to evaluate existing preclinical models and identify their applications in aspects of animal selection, bacterial induction, fracture fixation and complications.

Methods

A systematic literature research was conducted in PubMed and Embase up to February 2020. A total of 31 studies were included. Information on the animal, bacterial induction, fracture fixation, healing result and complications were extracted.

Results

Animals selected included murine (23), rabbit (6), ewe (1) and goat (1). Larger animals had enabled the use of human-sized implant, however small animals were more economical and easier in handling. Staphylococcus aureus (S. aureus) was the most frequently chosen bacteria for induction. Bacterial inoculation dose ranged from 10^2-8 ​CFU. Consistent and replicable infections were observed from 10⁴ ​CFU in general. Methods of inoculation included injections of bacterial suspension (20), placement of foreign objects (8) and pretreatment of implants with established biofilm (3). Intramedullary implants (13), plates and screws (18) were used in most models. Radiological (29) and histological evaluations (24) in osseous healing were performed. Complications such as instability of fracture fixation (7), unexpected surgical death (5), sepsis (1) and persistent lameness (1) were encountered.

Conclusion

The most common animal model is the S. aureus infected open fracture internally fixated. Replicable infections were mainly from 10⁴ ​CFU of bacteria. However, with the increase in antibiotic resistance, future directions should explore polymicrobial and antibiotic resistant strains, as these will no doubt play a major role in bone infection. Currently, there is also a lack of osteoporotic bone infection models and the pathophysiology is unexplored, which would be important with our aging population.

The translational potential of this article

This systematic review provides an updated overview and compares the currently available animal models of osteosynthesis-associated infections. A discussion on future research directions and suggestion of animal model settings were made, which is expected to advance the research in this field.

Comparing the sterility and visibility of surgical marking pens available in Australia

BACKGROUND

Surgical site marking is an important safety procedure prior to surgery. Visibility of pen marks is affected by surgical wash which increases the risk of wrong-site surgery. Additionally, multiple patient contact with a single pen is a potential source of bacterial transmission. In this study we compare pens commonly used for surgical marking in Australia.

METHODS

We conducted an unblinded, prospective cohort study comparing 12 marking pens. Six volunteers' thighs were marked with each pen. Standardized photographs were taken before and after wash with four prep solutions. Ink visibility was analysed using grayscale images, comparing the pen mark tone before and after wash. The pen tips were swabbed for culture.

RESULTS

Red tinted 2% chlorhexidine gluconate (w/v) with 70% isopropyl alcohol (v/v) was shown to reduce pen mark visibility significantly more than the other solutions used. The Pentel N50 permanent marker and Aspen WriteSite Plus were least affected by wash. No pen tip cultured any bacteria.

CONCLUSIONS

When marking the correct site for surgery, we recommend the use of either the Pentel N50 permanent marker or Aspen Writesite Plus pen. A 2-min interval between patient contact limits bacterial transmission.

A novel synthesis of 6''-[18 F]-fluoromaltotriose as a PET tracer for imaging bacterial infection

The aim of this study was to develop a positron emission tomography (PET) tracer to visualize and monitor therapeutic response to bacterial infections. In our continued efforts to find maltose based PET tracers that can image bacterial infections, we have designed and prepared 6''-[¹⁸ F]fluoromaltotriose as a second generation PET imaging tracer targeting the maltodextrin transporter of bacteria. We have developed methods to synthesize 6''-deoxy-6''-[¹⁸ F]fluoro-α-D-glucopyranosyl-(1-4)-O-α-D-glucopyranosyl-(1-4)-O-D-glucopyranose (6''-[¹⁸ F]-fluoromaltotriose) as a bacterial infection PET imaging agent. 6''-[¹⁸ F]fluoromaltotriose was prepared from precursor, 2'',3'',4''-tri-O-acetyl-6''-O-nosyl-α-D-glucopyranosyl-(1-4)-O-2',3',6'-tri-O-acetyl-α-D-glucopyranosyl-(1-4)-1,2,3,6-tetra-O-acetyl-D-glucopyranose (per-O-acetyl-6''-O-nosyl-maltotriose 4). This method utilizes the reaction between precursor 4 and anhydrous [¹⁸ F]KF/Kryptofix 2.2.2 in dimethylformamide (DMF) at 85°C for 10 minutes to yield per-O-acetyl-6''-deoxy-6-'' [¹⁸ F]-fluoromaltotriose (7). Successive acidic and basic hydrolysis of the acetyl protecting groups in 7 produced 6''-[¹⁸ F]fluoromaltotriose (8). Also, cold 6''- [¹⁹ F]fluoromaltotriose was prepared from per-O-acetyl-6''-hydroxymaltotriose via a diethylaminosulfur trifluoride reaction followed by a basic hydrolysis. A successful synthesis of 6''-[¹⁸ F]-fluoromaltotriose has been accomplished in 8 ± 1.2% radiochemical yield (decay corrected). Total synthesis time was 120 minutes. Serum stability of 6''-[¹⁸ F]fluoromaltotriose at 37°C indicated that 6''-[¹⁸ F]-fluoromaltotriose remained intact up to 2 hours. In conclusion, we have successfully synthesized 6''-[¹⁸ F]-fluoromaltotriose via direct fluorination of an appropriate precursor of a protected maltotriose.

Diagnostic accuracy of various modalities relative to open bone biopsy for detection of long bone posttraumatic osteomyelitis

BACKGROUND

Long bone posttraumatic osteomyelitis (PTOM) is a relatively common complication following surgical fixation of open fractures. There is a lacking consensus on ideal strategies for diagnostic evaluation of long bone PTOM. While open bone biopsy and culture is considered the 'gold diagnostic standard,' its cost and invasiveness are often prohibitive and have prompted the search for alternate diagnostic methods.

OBJECTIVE

To evaluate the sensitivity and specificity of various diagnostic modalities relative to open bone biopsy and culture for the detection of long bone PTOM.

DESIGN

Retrospective cohort study; Level of Evidence, III.

SETTING

Urban Level I trauma center and safety-net institution.

PATIENTS/PARTICIPANTS

A consecutive cohort of 159 adult patients presenting with long bone PTOM at our Level I trauma center between January 1, 2004, and December 31, 2013, were retrospectively identified. All included patients fulfilled diagnostic criteria for PTOM (as defined by the Center for Disease Control and Prevention) that involved a long bone (femur, fibula, tibia, humerus, radius, and ulna). Patients with diabetic foot infection, septic arthritis, osteomyelitis of the spine/pelvis/hand, or insufficient medical records were excluded.

MAIN OUTCOME MEASUREMENTS

Sensitivity and specificity of deep wound culture, soft tissue histopathologic examination, and elevated levels of acute phase reactants [C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and leukocyte count (WBC)] were determined using findings of open bone biopsy and culture as a reference standard.

RESULTS

The most common pathogen isolated on open bone culture was staphylococci, contributing to 89 (57%) of 159 cases of long bone PTOM (p < 0.001). Relative to open bone biopsy and culture as the gold diagnostic standard, soft tissue histopathology demonstrated a sensitivity of 69.8% [95% confidence interval (CI) 53.7-82.3%] and specificity of 38.9% (95% CI 18.3-63.9%) for the detection of long bone PTOM. Deep wound culture exhibited a lower sensitivity of 66.0% (95% CI 56.1-74.8%) and specificity of 28.1% (95% CI 12.9-49.5%), a difference that was statistically significant (p = 0.021). Among inflammatory markers, elevated levels of CRP and ESR were equally sensitive for the detection of PTOM compared to open bone biopsy and culture, while WBC was significantly less sensitive (sensitivity 33.2%; 95% CI 25.3-43.7; p < 0.001).

CONCLUSION

Soft tissue histopathologic examination and deep wound culture are relatively poor substitutes for the diagnosis of long bone PTOM compared to open bone biopsy and culture. The accurate identification of causative pathogens underlying long bone PTOM is critical for diagnosis and choice of antibiotic treatment. Future studies investigating the use of higher-resolution diagnostic methods are merited.

Bone cultures from war-wounded civilians in the Middle East: a surgical prospective

PURPOSE

Hidden infections in a reconstructive surgery program are frequently underestimated.

METHODS

A retrospective study was undertaken of 1,891 civilian war-wounded patients from Iraq, Syria, Yemen and Gaza treated in Amman from August 2006 to January 2016. One thousand three hundred and fifty-three underwent surgical interventions for previous bone injury and had systematic bone cultures.

RESULTS

Among patients (167) without any clinical, biological or radiological signs of infection, 46% demonstrated infection based on bone cultures. We conclude that bone culture should become a prerequisite for any reconstruction in such contexts.

Culture-Negative Infection After Operative Fixation of Fractures

OBJECTIVES

(1) Compare the outcomes of patients with orthopaedic trauma with culture-negative infection with those with pathogens identified; (2) identify the incidence of culture-negative infection and describe the common characteristics.

DESIGN

Retrospective study.

SETTING

Two level 1 trauma centers.

PATIENTS

A total of 391 patients 16 years of age or older who underwent irrigation and debridement for surgical site infection after having undergone fracture fixation were included.

INTERVENTION

Patients underwent irrigation and debridement with cultures, and antibiotic therapy was initiated.

MAIN OUTCOME MEASUREMENT

Treatment failure due to unsuccessful eradication of infection and time to union.

RESULTS

We found 9% incidence of culture-negative infection. Approximately one-third of patients in both groups went on to have treatment failure (25% of pathogen-specific infections, 38% of culture-negative infections, P = 0.15), and there was no difference between the 2 groups with regard to time to union (22 vs. 24 weeks, P = 0.55). More than one-third of patients required subsequent reconstructive procedure and 5% of patients in each group required amputation to control their infection. There was no difference between the groups with respect to the use of antibiotics before intervention and culture.

CONCLUSION

This study confirms the devastating effect that postoperative infections can have and suggests that, with clinical sign of infection, negative cultures do not portend a better prognosis. These entities should be treated in a similar manner to infections with positive cultures. Furthermore, we believe that future studies should not strictly rely on the presence of positive intraoperative cultures. Consensus as to what constitutes a clinical infection, in the absence of positive cultures, is needed.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Diagnostic performance of swab PCR as an alternative to tissue culture methods for diagnosing infections associated with fracture fixation devices

BACKGROUND

Molecular procedures could potentially improve diagnoses of orthopaedic implant-related infections, but are not yet clinically implemented. Analysis of sonication fluid shows the highest sensitivity for diagnosing implant infections in cases of revision surgery with implant removal. However, there remains controversy regarding the best method for obtaining specimens in cases of revision surgery with implant retention. Tissue culture is the most common diagnostic method for pathogen identification in such cases. Here we aimed to assess the diagnostic performance of swab PCR analysis compared to tissue culture from patients undergoing revision surgery of fracture fixation devices.

METHODS

We prospectively investigated 62 consecutive subjects who underwent revision surgery of fracture fixation devices during a two-year period. Tissue samples were collected for cultures, and swabs from the implant surface were obtained for 16S rRNA PCR analysis. Subjects were classified as having an implant-related infection if (1) they presented with a sinus tract or open wound in communication with the implant; or (2) purulence was encountered intraoperatively; or (3) two out of three tissue cultures tested positive for the presence of the same pathogen. Tissue culture and swab PCR results from the subjects were used to calculate the sensitivity, specificity, accuracy, positive predictive value (PPV), negative predictive value (NPV), and area under the ROC curve (AUC) for identifying an orthopaedic implant-related infection.

RESULTS

Orthopaedic implant-related infections were detected in 51 subjects. Tissue culture identified infections in 47 cases, and swab PCR in 35 cases. Among the 11 aseptic cases, tissue culture was positive in 2 cases and swab PCR in 4 cases. Tissue culture showed a significantly higher area under the ROC curve for diagnosing infection (AUC=0.89; 95% CI, 0.67-0.96) compared to swab PCR (AUC=0.66; 95% CI, 0.46-0.80) (p=0.033).

CONCLUSIONS

Compared to swab PCR, tissue culture showed better performance for diagnosing orthopaedic implant-related infection. Although molecular methods are expected to yield higher diagnostic accuracy than cultures, it appears that the method of obtaining specimens plays an important role. Improved methods of specimen collection are required before swab PCR can become a reliable alternative to tissue-consumptive methods.

Infection Imaging With (18)F-FDS and First-in-Human Evaluation

PURPOSE

The noninvasive imaging of bacterial infections is critical in order to reduce mortality and morbidity caused by these diseases. The recently reported (18)F-FDS ((18)F-2-fluorodeoxy sorbitol) as a PET (positron emission tomography) tracer can be used to image Enterobacteriaceae-specific infections and provides a potential alternative to this problem compared with other probes for imaging infections. In this study, automatic synthesis, validation of (18)F-FDS and a first-in-human study were performed and discussed.

METHODS

A multifunctional synthesis module was employed for the radiosynthesis of (18)F-FDG ((18)F-2-fluorodeoxy glucose) and (18)F-FDS starting from (18)F ion using two-pot three-step fully automated reactions. The behavior of (18)F-FDS as an in vivo imaging probe for infections was evaluated in an Escherichia coli mouse infection model. The first detailed pharmacokinetic and biodistribution parameters were obtained from healthy human volunteers.

RESULTS

The uptake of (18)F-FDS in an E. coli mouse-myositis infection model was easily differentiated from other organs and normal muscle. Intensive lesion uptake declined after antibiotic treatment. In the pilot human study, no adverse effects due to (18)F-FDS were observed up to 24 h post-injection. The radiotracer was rapidly cleared from the circulation and excreted mainly through the urinary system.

CONCLUSION

We conclude that (18)F-FDS PET holds great potential for appropriate and effective for the imaging of bacterial infections in vivo. These preliminary results indicate that further clinical studies are warranted.

Novel Strategies for the Diagnosis of Posttraumatic Infections in Orthopaedic Trauma Patients

Orthopaedic infections that occur after trauma are common. Clinical examination, laboratory markers, imaging modalities, and culture and molecular technologies are used to aid the diagnosis of infection. Culture methods comprise the backbone of diagnostic systems used in hospital laboratory settings; however, several studies have questioned the ability of these techniques to adequately identify infections, particularly in cases where orthopaedic implants were used or when the presence of biofilm bacteria is suspected. Advances in imaging and molecular diagnostics can provide orthopaedic surgeons with an improved means of diagnosing and treating infections.

Testing for Infectious Diseases in Sudden Unexpected Infant Death: A Survey of Medical Examiner and Coroner Offices in the United States

OBJECTIVES

To determine interoffice variability in routinely performed sudden unexpected infant death (SUID) postmortem studies for infection and to assess availability and perceived utility of various tests of infectious diseases.

STUDY DESIGN

Online surveys were sent to all 154 offices of US medical examiners and coroners serving populations >300,000 people. Surveys included a set of potential laboratory tests for infectious disease. Respondents were asked to select which tests were available in their offices, and which tests were performed routinely in SUIDs vs which tests should be performed routinely.

RESULTS

Of the 45 complete responses, 4.4% did not routinely perform histology, 8.9% did not routinely perform viral studies (ie, culture or molecular diagnostics), 22.2% did not routinely perform blood cultures, 26.7% did not routinely perform lung bacterial cultures, and 44.4% did not routinely perform cerebrospinal fluid cultures.

CONCLUSIONS

Our findings suggest that there is considerable interoffice variability with testing for infectious diseases in SUIDs. This appeared to be largely the result of a perceived lack of testing utility rather than a lack of test availability. Evidence-based practice guidelines regarding the interpretation of microbial testing results, as well as common testing protocols/algorithms, may lead to more accurate and standardized data, thus improving SUID investigation and surveillance.

Bacterial imaging comes of age

Enterobacteriaceae, a type of highly virulent Gram-negative bacteria, can be imaged in vivo in animals via positron emission tomography with (18)F-sorbitol (Weinstein et al., this issue).

Preoperative and intraoperative infection workup in apparently aseptic revision shoulder arthroplasty

The possibility of infection should be considered in every revision shoulder arthroplasty even in the absence of clinical symptoms and signs of infection because indolent infection is prevalent. Detection of infection in apparently aseptic failed arthroplasties poses a diagnostic challenge as the conventional principles and criteria used for hip and knee arthroplasty are not generally applicable. Propionibacterium acnes and Staphylococcus epidermidis are among the infectious organisms most commonly identified in such situations. Serum inflammatory markers are essential but are often unreliable as they have poor sensitivity in the shoulder. Preoperative shoulder joint aspiration culture is an important step but is subject to high false-negative rates. Lower cutoff values of synovial fluid analysis are used for detection of periprosthetic infection than for native joint infection as demonstrated in the knee literature. Intraoperatively, frozen section should be considered when a diagnosis of infection has not been established even in the presence of clinical suspicion. Gram stain is currently not recommended because of its low sensitivity and negative predictive value. Intraoperative culture is critical and should be performed whenever there is clinical suspicion of infection. Unexpected positive intraoperative cultures are not uncommon, and 6% to 25% of them appear to represent true infection as demonstrated with positive follow-up cultures or subsequent development of infection. In revision shoulder arthroplasty, determining the presence of infection can be difficult. A standardized approach is needed to determine the best course of treatment in this particular clinical setting.

Septic bursitis in an 8-year-old boy

Background. The prepatellar bursa can become inflamed owing to repeated trauma. Prepatellar bursitis is extremely rare in children. Methods. We report the case of an 8-year-old boy who was treated for an erythematous, swollen, and severely painful right knee, fever, inability to bear weight on the leg, and purulent material draining from a puncture wound. We describe the differential diagnosis for tender swollen knee, including infection, gout, rheumatoid arthritis, and osteoarthritis. If untreated, prepatellar bursitis can progress to patellar osteomyelitis. Results. Wound cultures grew Streptococcus pyogenes, with the infection resolving with amoxicillin. Conclusions. A high index of suspicion is necessary in children presenting with prepatellar bursitis to prevent potentially devastating sequelae of infection of the septic joint.

Preoperative antiseptic skin preparations and reducing SSI

Surgical site infection (SSI) can affect the quality of care and increase the morbidity and mortality rate in after-surgical procedure. The use of an antiseptic skin preparation agent before the procedure can reduce the pathogens in the skin surface around the incision. Indicating the type of skin antiseptic preparation could prevent the infection and contamination of the wound. The most commonly used types of skin preparations are chlorhexidine and povidone iodine. However, the antiseptic solutions of both agents are strengthened with alcohol to prevent postoperative wound infection. The aim of this paper is to identify the best antiseptic agent in terms of skin preparation by evaluating the evidence in the literature. The factors associated with choosing the antiseptic skin agent, such as patients' allergies, skin condition and environmental risk, are also taken into account. This review suggests that cholorhexdine with alcohol may be the most effective in terms of reducing SSI.

Swab cultures are not as effective as tissue cultures for diagnosis of periprosthetic joint infection

BACKGROUND

While it is accepted accurate identification of infecting organisms is crucial in guiding treatment of periprosthetic joint infection (PJI), there remains no consensus regarding the best method for obtaining cultures.

QUESTIONS/PURPOSES

We compared the yield of intraoperative tissue samples versus swab cultures in diagnosing PJI.

METHODS

Tissue and swab cultures (three each) were collected prospectively during a consecutive series of 156 aseptic and septic revision arthroplasties from October 2011 to April 2012. The tissues and swabs were taken from standardized regions of the joint. After excluding 39 reimplantation procedures, we included 117 cases (74 hip, 43 knee; 30 septic, 87 aseptic) for analysis. We used a modified version of the Musculoskeletal Infection Society criteria for defining PJI, requiring three of five rather than four of six criteria. Tissue and swab cultures from septic and aseptic cases were used to calculate their sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for identifying PJI.

RESULTS

Tissue cultures were positive in a higher percentage of septic cases than swab cultures: 28 of 30 (93%) versus 21 of 30 (70%). Tissue cultures were positive in two of 87 aseptic cases (2%), while swab cultures were positive in 10 of 87 (12%). The sensitivity, specificity, PPV, and NPV were 93%, 98%, 93%, and 98%, respectively, for tissue cultures and 70%, 89%, 68%, and 90%, respectively, for swab cultures.

CONCLUSIONS

Tissue cultures demonstrated higher sensitivity, specificity, PPV, and NPV for diagnosing PJI than swab cultures. Swab cultures had more false-negative and false-positive results than tissue cultures. Because swab cultures pose a higher risk of not identifying or incorrectly identifying infecting organisms in PJI, we believe their use in obtaining intraoperative culture specimens should be discouraged.

LEVEL OF EVIDENCE

Level II, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

A guide to utilization of the microbiology laboratory for diagnosis of infectious diseases: 2013 recommendations by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM)(a)

The critical role of the microbiology laboratory in infectious disease diagnosis calls for a close, positive working relationship between the physician and the microbiologists who provide enormous value to the health care team. This document, developed by both laboratory and clinical experts, provides information on which tests are valuable and in which contexts, and on tests that add little or no value for diagnostic decisions. Sections are divided into anatomic systems, including Bloodstream Infections and Infections of the Cardiovascular System, Central Nervous System Infections, Ocular Infections, Soft Tissue Infections of the Head and Neck, Upper Respiratory Infections, Lower Respiratory Tract infections, Infections of the Gastrointestinal Tract, Intraabdominal Infections, Bone and Joint Infections, Urinary Tract Infections, Genital Infections, and Skin and Soft Tissue Infections; or into etiologic agent groups, including Tickborne Infections, Viral Syndromes, and Blood and Tissue Parasite Infections. Each section contains introductory concepts, a summary of key points, and detailed tables that list suspected agents; the most reliable tests to order; the samples (and volumes) to collect in order of preference; specimen transport devices, procedures, times, and temperatures; and detailed notes on specific issues regarding the test methods, such as when tests are likely to require a specialized laboratory or have prolonged turnaround times. There is redundancy among the tables and sections, as many agents and assay choices overlap. The document is intended to serve as a reference to guide physicians in choosing tests that will aid them to diagnose infectious diseases in their patients.

Review article: Joint aspiration for diagnosis of periprosthetic infection

Joint aspiration is a reliable tool for diagnosis of periprosthetic infection. There are different indications, techniques, and approaches for joint aspiration. We recommend that it be performed selectively when infection is suspected clinically. The specimens should be interpreted based on the results of the culture as well as the white cell count and differential. Specimen collection, transport, and analysis should be prompt to ensure yield accuracy.

Colletotrichum gloeosporioides sensu lato causing deep soft tissue mycosis following a penetrating injury

Colletotrichum species have been rarely implicated in human disease. We describe a case of deep soft tissue mycosis following a penetrating injury with a lemon tree thorn. Direct Blankophor BA (Bayer) stain from intraoperative tissue showed fungal elements. Pure growth fungus was apparent at 2-4 days. Morphological features provisionally identified the isolate as a coelomycetous fungus, likely Colletotrichum species. This was confirmed with molecular analysis of the internal transcribed spacer region (ITS) region.

A biofilm approach to detect bacteria on removed spinal implants

STUDY DESIGN

This is a prospective study comparing the diagnosis of spinal implant infection by conventional peri-implant tissue culture with a technique which uses a combination of vortexing and bath sonication to dislodge bacteria growing as a biofilm on the surface of retrieved spinal implants.

OBJECTIVE

We hypothesized that the biofilm-sampling technique would be more sensitive than peri-implant tissue culture.

SUMMARY OF BACKGROUND DATA

Culture of peri-implant tissue is inaccurate for the diagnosis of orthopedic device-related infection; cultures taken from the implant may be more sensitive. We have developed a technique which uses vortexing-bath sonication to sample bacterial biofilms on the surface of retrieved hip and knee implants, and shown that it is more sensitive than peri-prosthetic tissue culture for the microbiologic diagnosis of prosthetic knee, hip, and shoulder infection.

METHODS

We compared peri-implant tissue culture to the vortexing-bath sonication technique which samples bacterial biofilm on the surface of retrieved spinal implants, for the diagnosis of spinal implant infection. In addition, we compared detection of Staphylococcus and Propionibacterium acnes by rapid cycle real-time polymerase chain reaction with culture of sonicate fluid.

RESULTS

A total of 112 subjects were studied; 22 had spinal implant infection. The sensitivities of peri-implant tissue and sonicate fluid culture were 73% and 91% (P = 0.046), and the specificities were 93% and 97%, respectively. P. acnes and coagulase-negative staphylococci were the most frequent microorganisms detected among subjects with spinal implant infection, with P. acnes detected in 56 and 45%, and coagulase-negative staphylococci detected in 31 and 40% of peri-implant tissue and sonicate fluid cultures, respectively. Compared with the culture of sonicate fluid, polymerase chain reaction was 100 and 67% sensitive for the detection of culture-positive Staphylococcus and P. acnes spinal implant infection, respectively.

CONCLUSION

Implant sonication followed by culture is more sensitive than peri-implant tissue culture for the microbiologic diagnosis of spinal implant infection.

Review Papers: Current Techniques to Detect Foot Infection in the Diabetic Patient

Diabetic foot infections can be a challenge to diagnose, especially when osteomyelitis is in question. Evaluation of infection should involve a thorough examination of the extremity for clinical signs of infection along with appropriate laboratory and imaging studies. Laboratory markers of inflammation such as peripheral leukocyte count, erythrocyte sedimentation rate, C-reactive protein, and procalcitonin may provide useful information when diagnosing soft tissue and bone infection. However, laboratory markers alone should not be used to diagnose a diabetic foot infection as they are non-specific in nature. Imaging studies may also provide valuable clues regarding the presence of infection. Plain radiographs are a good initial screening tool as they are both inexpensive and easily accessible. However, their sensitivity in diagnosing osteomyelitis is poor. Thus, more advanced imaging such as radionuclide imaging and magnetic resonance imaging are warranted when osteomyelitis is suspected. Magnetic resonance imaging is presently considered the gold standard in diagnosing osteomyelitis, despite its wide variation in reported sensitivity and specificity. However, the significant cost of magnetic resonance imaging prevents its use as a screening tool. Collection of reliable microbiologic data is critical in making a diagnosis as well as for treatment of infection, especially when osteomyelitis is concerned. Deep swabs and transcutaneous bone biopsy are considered the ideal methods of obtaining the necessary information. Finally, monitoring treatment should also be performed with an eye towards both laboratory data and the clinical exam.

Outcome of patients with meticillin-resistant Staphylococcus aureus bacteraemia at an Emergency Department of a medical centre in Taiwan

The number of patients presenting to the Emergency Department (ED) with meticillin-resistant Staphylococcus aureus (MRSA) is increasing, but few studies focus on patients with bacteraemia. From January 2001 to June 2006 the clinical characteristics and outcome of 177 consecutive patients with MRSA bacteraemia visiting an ED of a university hospital were studied. The average age of the patients was 65.8 years. Healthcare-associated MRSA bacteraemia comprised 76.3% of all cases. Catheter-related bacteraemia was the most common type of infection (22.6%), followed by soft tissue infection (20.9%) and primary bacteraemia (15.3%). Different types of infection were significantly related to different outcome. In-hospital mortality was 33.3%, but the mortality decreased to 17.7% when patients with rapidly fatal disease and mortality within 3 days were excluded. All isolates exhibited lower susceptibility to vancomycin (minimum inhibitory concentration (MIC) 1–2 μg/mL). Factors associated with mortality included severity of underlying illness, severity of bacteraemia and persistent bacteraemia. A detrimental effect of elevated MIC could not be demonstrated despite applying several definitions of patient outcome. Patients admitted to the ED with MRSA bacteraemia carry high overall mortality; however, the severity of underlying illness, severity of bacteraemia and persistent bacteraemia are correlated with mortality, but not vancomycin MICs (2 μg/mL) of MRSA isolates.