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.