Paper of the week: Polymerase chain reaction assay using the restriction fragment length polymorphism technique in the detection of prosthetic joint infections: A Multi-Centered Study

Paper of the week: Polymerase chain reaction assay using the restriction fragment length polymorphism technique in the detection of prosthetic joint infections: A Multi-Centered Study. Moshirabadi A, Razi M, Arasteh P, Sarzaeem MM, Ghaffari S, Aminiafshar S, Hosseinian Khosroshahy K, Sheikholeslami FM. J Arthroplasty. 2018 Oct 25. pii: S0883-5403(18)31057-X. doi: 10.1016/j.arth.2018.10.017. [Epub ahead of print].

Summary and Editorial by Sreeram Penna

The main aim of this prospective study was to assess the diagnostic accuracy of polymerase chain reaction (PCR) using RFLP (restriction fragment length polymorphism) method. Researchers also obtained bacterial cultures at the same time. The study assessed 76 samples using this technique. International consensus meeting criteria were used to identify prosthetic joint infection. 50% of the samples were deemed infected based on the above criteria. Results showed that using PCR RFLP Sensitivity and specificity was found to be 97.4% and 100% respectively. This was superior compared to the culture where sensitivity and specificity was 31.6% and 100%. Researchers isolated a broad range of bacteria including fastidious organisms like Chlamydophila pneumonia, Stenotrophomonas maltophilia, Brucella melitensis. One advantage of this technique is the amount of time required to get the pathogen identification is approximately 3 to 4 hours compared to multiple days for microbiological culture methods.

Restriction fragment length polymorphism (RFLP) is a difference in homologous DNA sequences which are identified by the different length of sequences after digestion of DNA samples using specific restriction endonucleases. RFLP probes are widely used in genome mapping and variation analysis such as genotyping, forensics, paternity tests, hereditary disease diagnostics, etc. This process requires a large amount of DNA and is labor intensive.[1] Combining PCR along with RFLP (also called cleaved amplified polymorphic sequences or CAPS) solves the problem of the requirement of a large sample.[2] Using PCR RFLP method with 16s bacterial DNA has been used in bacterial identification in clinical situations, food safety and also identify different strains of bacteria.[3–6] Rohit et al., used this technique to rapidly diagnose bacterial species in the setting of neonatal sepsis.[3] This study provides importance of such technique in PJI setting where it is very important to identify pathogens as it has huge implications in the management.


[1] Restriction Fragment Length Polymorphism (RFLP) n.d. https://www.ncbi.nlm.nih.gov/probe/docs/techrflp/ (accessed December 17, 2018).

[2] Cleaved Amplified Polymorphic Sequences (CAPS) n.d. https://www.ncbi.nlm.nih.gov/probe/docs/techcaps/ (accessed December 17, 2018).

[3] Rohit A, Maiti B, Shenoy S, Karunasagar I. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for rapid diagnosis of neonatal sepsis. Indian J Med Res 2016;143:72–8. doi:10.4103/0971-5916.178613.

[4] Schütte UME, Abdo Z, Bent SJ, Shyu C, Williams CJ, Pierson JD, et al. Advances in the use of terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA genes to characterize microbial communities. Appl Microbiol Biotechnol 2008;80:365–80. doi:10.1007/s00253-008-1565-4.

[5] Meyer R, Höfelein C, Lüthy J, Candrian U. Polymerase chain reaction-restriction fragment length polymorphism analysis: a simple method for species identification in food. J AOAC Int 1995;78:1542–51.

[6] González A, Moreno Y, González R, Hernández J, Ferrús MA. Development of a simple and rapid method based on polymerase chain reaction-based restriction fragment length polymorphism analysis to differentiate Helicobacter, Campylobacter, and Arcobacter species. Curr Microbiol 2006;53:416–21. doi:10.1007/s00284-006-0168-5.


Paper of the week: Humidity a potential risk factor for prosthetic joint infection in a tropical Australian hospital.

Paper of the week: Humidity a potential risk factor for prosthetic joint infection in a tropical Australian hospital. Armit D, Vickers M, Parr A, Van Rosendal S, Trott N, Gunasena R, Parkinson B. ANZ J Surg. 2018 Dec;88(12):1298-1301. doi: 10.1111/ans.14916. Epub 2018 Oct 24.

Summary and Editorial by Sreeram Penna and Javad Parvizi

This study aims to determine the role of humidity as a risk factor for the development of prosthetic joint infection (PJI) in total knee replacement patients. In this single-center retrospective study researchers looked at the incidence of deep PJI and correlated with daily weather data. Deep PJI was diagnosed using the Australian Commission on Safety and Quality in Health Care criteria for deep incisional organ space infection. Weather variables used for analysis was relative humidity and apparent temperature on the day of the primary procedure. Results showed humidity more than 60% (OR 1.4) and apparent temperature more than 30-degree centigrade (OR 2.4) are possible potential risk factors for the development of deep PJI. However, these variables were not statistically significant.

A Study by Parkinson et al. based on Australian Orthopaedic Association National Joint Replacement Registry, have shown higher PJI incidence in tropical regions (0.73%) compared to the non-tropical areas (0.37%). [1] Their results also showed seasonal variation in the tropical areas with a higher incidence in summer/fall (0.98%) compared to winter/spring (0.51%). Hot and humid weather increases sweating and provide conditions to bacterial growth which might explain the reason behind the increase in infection. One issue with the above study is that weather variables were recorded on the day of surgery, where the patient is indoors, and air conditioning would provide a constant stable environment inside the hospital.


[1] Parkinson B, Armit D, McEwen P, Lorimer M, Harris IA. Is Climate Associated With Revision for Prosthetic Joint Infection After Primary TKA? Clin Orthop Relat Res 2018;476:1200–4. doi:10.1007/s11999.0000000000000144.


Paper of the week: Cutibacterium acnes and the shoulder microbiome.

Paper of the week: Cutibacterium acnes and the shoulder microbiome. Qiu B, Al K, Pena-Diaz AM, Athwal GS, Drosdowech D, Faber KJ, Burton JP, O’Gorman DB. J Shoulder Elbow Surg. 2018 Oct;27(10):1734-1739. doi: http://dx.doi.org/10.1016/j.jse.2018.04.019.

Summary and Editorial by Dr. Sreeram Penna and Dr. Surena Namdari

The aim of this study is to determine if there is a microbiome in the native shoulder joint and whether Cutibacterium acnes (previously known as Propionibacterium acnes), the most common cause of shoulder infections, is part of this microbiome. The indolent nature of Cutibacerium acnes (C. acne) along with lack of significant biomarker response makes it a difficult bacteria to manage. Also, its presence in culture samples in cases with negative joint infection leads to a theory that this bacterium could be commensal in the native joint.

In this study, researchers collected tissue samples from patients undergoing primary open shoulder arthroplasty with no history of previous infection. Twenty-three patients were included in the study. Researchers collected tissue samples from skin, subcutaneous fat, anterior edge of the supraspinatus tendon, middle glenohumeral ligament, and humeral head. A total of 136 samples were collected. Samples were then analyzed using 16s RNA sequencing to identify operational taxonomic units. After careful removal of contamination, results showed that 53 samples showed positive for microbial genome and most abundant bacterial type was Acinetobacter and Oxalobacteraceae. C. acnes was only identified in one skin sample. Anatomical structure wise 74% of supraspinatus tendon samples and 49% of joint capsule samples were positive for a microbial genome.

This study shows that the native shoulder joint is not completely sterile, and bacteria are present. Interestingly C. acnes is not present in the native shoulder joint. Advances in the genomic analysis are making it easier to identify bacterial species and to characterize the microbial genome. Studies of 16s RNA sequencing remain limited by both the risk of contamination and the risk of identifying dead bacteria [1,2]. Further research is needed on the impact of oral and gut microbial load on tissue microbiome as it is well known that transient bacteremia can occur following activities like oral brushing and can lead to tissue seeding.[3,4]


[1]    Salter SJ, Cox MJ, Turek EM, Calus ST, Cookson WO, Moffatt MF, et al. Reagent and laboratory contamination can critically impact sequence-based microbiome analyses. BMC Biology 2014;12:87. doi:10.1186/s12915-014-0087-z.

[2]    Weiss S, Amir A, Hyde ER, Metcalf JL, Song SJ, Knight R. Tracking down the sources of experimental contamination in microbiome studies. Genome Biology 2014;15:564. doi:10.1186/s13059-014-0564-2.

[3]    Maharaj B, Coovadia Y, Vayej AC. An investigation of the frequency of bacteraemia following dental extraction, tooth brushing and chewing. Cardiovasc J Afr 2012;23:340–4. doi:10.5830/CVJA-2012-016.

[4]    Lockhart Peter B., Brennan Michael T., Sasser Howell C., Fox Philip C., Paster Bruce J., Bahrani-Mougeot Farah K. Bacteremia Associated With Toothbrushing and Dental Extraction. Circulation 2008;117:3118–25. doi:10.1161/CIRCULATIONAHA.107.758524.


Paper of the week: Culturing periprosthetic tissue in blood culture bottles results in isolation of additional microorganisms.

Title: Culturing periprosthetic tissue in blood culture bottles results in isolation of additional microorganisms.  van den Bijllaardt W, van der Jagt OP, Peijs M, Janssens M, Buiting AG, Reuwer AQ. European Journal of Clinical Microbiology & Infectious Diseases. 2018 Epub. DOI: 10.1007/s10096-018-3420-6

Summary and Editorial by  Dr. Marjan Wouthuyzen-Bakker and Dr. Sreeram Penna

The aim of this prospective clinical validation study was to evaluate if there is an added diagnostic value to culturing periprosthetic tissues in blood culture bottles (BCB) in addition to standard conventional cultures in diagnosing periprosthetic joint infection (PJI). The study was conducted over a 12-month period with 113 episodes in 90 patients. The researchers utilized the Infectious Diseases Society of America (IDSA) criteria for PJI as a gold standard in assessing sensitivity and specificity of culture. In the studied cohort, 45 patients met the IDSA criteria for PJI, and of these cases, 34 were acute infections. The main finding of this study was that periprosthetic tissue cultures in BCB led to the isolation of additional microorganisms in 30% of cases and increased the sensitivity for PJI diagnosis with 10% compared to standard cultures in agar and broth. Moreover, in 9 cases, virulent microorganisms were cultured in BCB only.

Culture-negative PJIs remains a concern for physicians treating patients with PJIs and in the last decade, many studies have been performed to improve culture techniques in order to increase culture yield. Several studies already demonstrated the clinical benefit of culturing synovial fluid and sonication in fluid in BCB by increasing the diagnostic yield and reducing the time to detection[1,2], but only a few studies evaluated its potential benefit for tissues samples. Peel et al., demonstrated an increased sensitivity of inoculating tissue samples in BCB compared to conventional cultures. Its benefit was most evident in patients with chronic infections.[3] In addition, Minassian et al. demonstrated a shorter time to positivity in which the majority of microorganisms were identified within 3 days.[2] This paper of the week conducted by van den Bijllaardt et al. adds to the current literature. In the studied cohort, four cases would be missed as infected if only clinical, serological and conventional cultures findings were used to diagnose PJI and multiple microorganisms would remain undetected with conventional methods. As in the current study, synovial fluid was not inoculated in BCB and sonication was not performed, it is unclear whether the inoculation of tissue samples in BCB will add to these methods. A recent study by Yan et al. could not find a significant difference in sensitivity of tissue culture in BCBs compared to sonicate fluid culture[4], and the use of BCB for tissue samples could be an alternative approach for centers that do not apply sonication.


[1]    Portillo ME, Salvadó M, Trampuz A, Siverio A, Alier A, Sorli L, et al. Improved diagnosis of orthopedic implant-associated infection by inoculation of sonication fluid into blood culture bottles. J Clin Microbiol 2015;53:1622–7. doi:10.1128/JCM.03683-14.

[2]    Minassian AM, Newnham R, Kalimeris E, Bejon P, Atkins BL, Bowler IC. Use of an automated blood culture system (BD BACTECTM) for diagnosis of prosthetic joint infections: easy and fast. BMC Infect Dis 2014;14:233. doi:10.1186/1471-2334-14-233.

[3]    Peel TN, Dylla BL, Hughes JG, Lynch DT, Greenwood-Quaintance KE, Cheng AC, et al. Improved Diagnosis of Prosthetic Joint Infection by Culturing Periprosthetic Tissue Specimens in Blood Culture Bottles. MBio 2016;7. doi:10.1128/mBio.01776-15.

[4]    Yan Q, Karau MJ, Greenwood-Quaintance KE, Mandrekar JN, Osmon DR, Abdel MP, et al. Comparison of Diagnostic Accuracy of Periprosthetic Tissue Culture in Blood Culture Bottles to That of Prosthesis Sonication Fluid Culture for Diagnosis of Prosthetic Joint Infection (PJI) by Use of Bayesian Latent Class Modeling and IDSA PJI Criteria for Classification. Journal of Clinical Microbiology 2018;56:e00319-18. doi:10.1128/JCM.00319-18.


Paper of the week: Irrigation and debridement with chronic antibiotic suppression for the management of infected total knee arthroplasty

Irrigation and debridement with chronic antibiotic suppression for the management of infected total knee arthroplastyWeston JT, Watts CD, Mabry TM, Hanssen AD, Berry DJ, Abdel MP. Bone Joint J. 2018 Nov;100-B(11):1471-1476.
doi: 10.1302/0301-620X.100B11.BJJ-2018-0515.R1.

Summary and editorial by Sreeram Penna

Above study is a single center retrospective review of 134 infected total knee arthroplasty cases ( acute post-operative infection in 23 and acute hematogenous infection in 111). All patients had Irrigation debridement using normal saline and retention of components except modular poly-ethylene components which were replaced. All patients had organism-specific antibiotic followed by long-term antibiotic suppression.

The study found the infection-free survival of 72% at two years and 66% at five years. The study also showed that age less than 60 and infection with staphylococcal species was associated with increased risk of subsequent infection. Culture-negative infection cases have a lower risk of recurrence or subsequent infections. Musculoskeletal Infection Society host type, body mass index (BMI), the duration of symptoms, gender, and the presence of a monoblock tibial component did not have any influence on the outcome.

In another study Siqueira et al., has shown similar infection-free prosthetic implant survival (68.5% at five years) following irrigation and debridement, polyethylene exchange and chronic antibiotic suppression. [1] However in that study cases with staphylococcal infection fared better following chronic antibiotic suppression compared to those who did not receive suppressive antibiotics following irrigation and debridement. Similarly Rao et al., showed favorable results in 86% of patients at 5 years were able to maintain functioning prosthesis.[2] In another study on patients with osteomyelitis Nowak et al showed successful suppression of the disease. [3] In this study diabetes was associated with a high failure rate and also there was a high incidence (25%) of adverse reactions associated with suppressive antibiotics.


[1] Siqueira MBP, Saleh A, Klika AK, O’Rourke C, Schmitt S, Higuera CA, et al. Chronic Suppression of Periprosthetic Joint Infections with Oral Antibiotics Increases Infection-Free Survivorship. J Bone Joint Surg Am 2015;97:1220–32. doi:10.2106/JBJS.N.00999.

[2] Rao N, Crossett LS, Sinha RK, Le Frock JL. Long-term suppression of infection in total joint arthroplasty. Clin Orthop Relat Res 2003:55–60. doi:10.1097/01.blo.0000087321.60612.cf.

[3] Nowak MA, Winner JS, Beilke MA. Prolonged oral antibiotic suppression in osteomyelitis and associated outcomes in a Veterans population. Am J Health Syst Pharm 2015;72:S150-155. doi:10.2146/sp150022.