This study reports that the incidence of MSSA-colonization in patients undergoing TJA in South Africa was 31.9%. Analysis of the TJA population indicated a 1.7-fold increased risk for MSSA-colonization in those awaiting TKA compared to THA respectively (OR TKA = 0.58, OR THA = 0.33). In the USA, Ramos et al. (2016) found that the prevalence of S aureus colonization in 13, 828 consecutive THA, TKA and spinal fusions was 18.21%.  A similar increased prevalence for MRSA was observed in TKA patients (16.3%) compared to THA patients (12.99%) respectively. 
Whilst no previous studies conducted on S aureus prevalence in a TJA population in South Africa, an epidemiological study found that nosocomial incidence of MSSA and MRSA varied from 1.9 to 3.7 cases per 1000 admissions and 0.03 to 0.08 cases per 1000 admissions, respectively.  In the USA, several studies of patients for TJA report the incidence of S aureus colonization to range between 17.5%-25.1% for MSSA and 1.8%-5% for MRSA respectively. [29-31] There have been several published S aureus prevalence studies in the USA for a TJA population, however respective data for other regions is limited. Hadi et al. (2018) reported that 20.8% of 226 patients awaiting TJA in Arak, Iran were S aureus carriers.  Tsang et al. (2018) reported the prevalence for MSSA at 37.9% and MRSA at 2.3% respectively, in 273 TJA patients in the UK.  Barbero Allende et al. (2015) identified 26.7% of patients colonized with S aureus awaiting TJA in Spain. 
Several risk factors have been described for S aureus colonization including gender, age, recent hospitalization, ethnicity, genetic predisposition, diabetes mellitus, HIV, haemodialysis, other concurrent skin infections and antibiotic treatment misuse.  This study did not identify any statistically significant risk factors that predicted for the pre-operative colonization with S aureus, which was likely due to the small sample size.
The small cohort of patients showed a trend of increased prevalence of S aureus colonization in HIV positive patients (p=0065). Higher rates of S aureus colonization have been reported in HIV-infected patients with the incidence of MRSA reported as high as 31%. [36-37] Amongst nosocomial S aureus infections in South Africa, the overall prevalence of HIV was found to be 32%, which subdivided into 42% and 27% for MRSA and MSSA cases respectively (p=0.106).  In a review of 404 HIV-infected outpatients from two separate centers in Botswana, the nasal colonization of S aureus and MRSA was 36.9% and 3.2% respectively.  In HIV-infected patients, those living with children and in high population-density areas were at significantly increased risk for S aureus colonization.  All HIV-infected patients in this study were on HAART pre-operatively. The VL of all patients was undetectable before surgery. The low incidence of HIV-infected patients colonized with S aureus may be as a result of good disease control although the population sample was too small to correlate statistically significant conclusions.
In our study 81.6% of identified MSSA-carriers had positive cultures from swabs taken from the anterior nares. The anterior nares are the primary site of S aureus colonization whilst other areas that may serve as reservoirs include the oropharynx, axillae, groin, perineum, forehead, and neck. [12,38] Sampling these sites in addition to the anterior nares may improve the detection rates of S aureus however this will infer an increased financial burden.
The decolonization rate using mupirocin and chlorhexidine was 94.74% in this study and is in keeping with literature. Moroski et al. (2015) evaluated the effectiveness of a MSSA and MRSA decolonization regime of nasal carriers in patients undergoing primary and revision TJA.  The decolonization strategy was a five-day pre-operative course of intranasal mupirocin only and chlorhexidine was not included.  Moroski et al. demonstrated that 34% of MSSA carriers remained colonized despite treatment, while 92% of MRSA-carriers were successfully decolonized.  Conversely Jeans et al. (2018) showed that eradication therapy with mupirocin ointment in patients awaiting TJA was most efficacious in patients colonized with MSSA rather than MRSA.  Barbero Allende et al. (2015) showed that the identical strategy to the one employed in our study resulted in a 98% decolonization rate.  The use of intranasal mupirocin and full body chlorhexidine wash yielded good results and supports the combination of both treatment modalities.
A number of strategies regarding the management of potential S aureus colonization of patients awaiting THA and TKA exist. The two most common are a “Screen and Treat” protocol [40-41] and a policy of universal decolonization.  The efficacy of screening and subsequently treating patients colonized with S aureus has been proven. [9,11,42-44] However, decolonizing all patients pre-operatively without screening for S aureus is simpler, less time consuming and less dependant on other resources, such as laboratories and staff to process the tests for instance.  Universal treatment has also been shown to be more cost-effective.  However, the evolution of bacterial resistance to the topical antimicrobials such as mupirocin becomes a factor of concern.  The Proceedings of the International Consensus on Orthopaedic Infections could not make any definitive recommendations regarding the most effective approach to managing and treating S aureus colonization pre-operatively due to inconsistent literature reports.  Screening and treating or only treating patients with certain medical or demographic risk profiles was, however, strongly discouraged.  Risk factors for S aureus colonization vary greatly and are poorly defined. The most suitable approach may actually differ at various individual institutions and be influenced by that institutions’ PJI rate and patient subpopulations seen and treated. 
There were no post-operative septic sequelae, with no incidences of SSIs or PJIs and no cases of revision TJA in this study at a mean follow-up of 37.34 months. However this study included a small sample size and this data cannot be extrapolated to be of statistical significance. S aureus colonization has been identified as a modifiable risk for SSI.  Patients colonized with S aureus have a nine- to ten- fold increased risk of developing a SSI. [10,16] MRSA-colonization infers an additional four fold increased risk of infective complications in comparison with MSSA-colonization.  Molecular typing has helped link S aureus colonization with SSI in THA, TKA and spine surgery.  The exact S aureus subtype found pre-operatively on nasal swab sampling was found to be the infective organism in 85.71% of cases. 
Ramos et al. (2016) found that S aureus colonization was identified as a significant risk factor for SSI in TKA patients.  The incidence of SSI in the colonized patients after receiving eradication therapy was lower (2.39%) than in non-colonized patients (4.35%).  Sporer et al. (2016) reported that decolonization of S aureus carriers revealed a 69% reduction in the rate of SSIs in comparison with a control group who had not been screened and treated.  In a systematic review of 79 papers from both the Portuguese and English literature, Sadigursky et al. (2017) reported that the use of prophylaxis to promote pre-operative decolonization of MRSA decreased the incidence of SSI by almost 39%.  Jeans et al. (2018) showed that the adoption a S aureus screening and decolonization programme in patients awaiting TJA reduced the PJI rate significantly from 1.92% to 1.41%.  Ultimately, £1893 was saved per case by decreasing the PJI rate.  Similarly, Barbero Allende et al. (2015) showed that the identical decolonization strategy to the one employed in our study resulted in an amelioration of the rate of SSI by 40.7%. 
There were several major weaknesses identified in evaluation of the study. The primary limitation was the small sample size of the population. The sample size was calculated in order to evaluate an accurate prevalence denomination for a specific population, however it was not large enough to determine the secondary aims such as significant risk factors or post-operative consequences.
Secondly, the success of eradication was only assessed on repeat swabs taken immediately after completion of the eradication therapy. A systematic review reported that the successful eradication of S aureus was 95% after one week, however rate decreased to 64% upon a subsequent review after two weeks.  Treatment failure risks were associated with colonization at multiple anatomic sites, longer hospital stays, and bacterial resistance to mupirocin. 
Additionally, the testing for S aureus did not make use of other techniques like polymerase chain reaction (PCR) tests or pre-plating the broth enrichment of swabs for culture to optimize the yield. These have been shown to definitively improve the detection rate of nasal MSSA colonization.  Tsang et al. (2018) showed that almost one third of both MRSA and MSSA carriers are missed should PCR and pre-plating of the broth enrichment of culture swabs not be added to traditional swabbing techniques.  However the use of PCR testing would have increased the costs of conducting this study and is notable in the context of a developing country such as South Africa. Lastly, only patients awaiting TJA that were screened for S aureus colonization pre-operatively were included in the study and there was no control group with which to compare all outcomes.