Different healthcare systems adopt different policies for screening of patients prior to TKA. In the United Kingdom, the Department of Health recommends that all patients being admitted for elective orthopaedic surgery should be screened for MRSA by way of nasal, axillary and perineal swabs, with those exhibiting colonization being treated with topical antiseptic ointment; they recommend against routine treatment without screening and do not give guidance on treatment of staff [7]. The situation in the United States is less straightforward; a 2015 current concepts review recommended that screening and eradication should be performed, as a cost-effective, low-risk intervention, although further evidence was needed [12]. In Europe, practice varies between countries, but most jurisdictions have policies for routine screening of high-risk patients or those admitted for high-risk procedures such as arthroplasty [8].

The introduction of MRSA screening programs has led to the establishment of standardized protocols for the detection and eradication of colonizing organisms. Whilst these vary between countries, the principles are broadly similar. No country has a national program by which every patient is screened; in most cases, patients deemed ‘at risk’ (including all orthopaedic patients) are screened with low-risk patients such as those presenting for day-case general surgery being excluded [8].

Various methods of screening are used. Typically, culture swabs are taken from the nose and perineum; other sites may be screened if of importance for the procedure being performed (such as the axilla in shoulder arthroplasty) or if of particularly high risk of colonization (such as indwelling lines and wounds) [13]. Both conventional culture and molecular techniques (polymerase chain reaction, PCR) are used for detection of organisms. PCR provides a rapid result within 2–4 h and so may be used for emergency admissions; however, it is more expensive than conventional culture and has little benefit over culture methods if performed prior to elective admission [14, 15]. For conventional culture, MRSA chromogenic agar is generally used—on this medium, MRSA grows as blue colonies which allows rapid visual identification without specialist equipment. However, this does not allow the identification of methicillin-sensitive staphylococcal strains (see Sect. 6.2.4) [16].

Patients identified as carriers of MRSA then go on to decolonization which is normally performed using mupirocin, which is a naturally occurring antibiotic. The use of mupirocin is advocated by the World Health Organization and the International Consensus Meeting on Prosthetic Joint Infection [17, 18]. Concerns exist as to resistance to the development of bacterial strains which are resistant to mupirocin [19]. Mupirocin resistance can be classified as low level (which occurs as a consequence of spontaneous chromosomal mutations) or high level (which is plasmid-mediated), and the prevalence of resistance by either mode may be as high as 95% [20]. The majority of these are the low-level type, which is of uncertain clinical significance, but the high prevalence of resistant strains is important to bear in mind, indicating the need for mupirocin to be part of antimicrobial stewardship arrangements like any other antibiotic. Other protocols, including the addition of chlorhexidine or the use of povidone iodine, have been developed and are advocated by some groups [21, 22].

The effectiveness of an MRSA screening and eradication program have been demonstrated by multiple studies, but the literature is not homogenous. A recent systematic review demonstrated significant falls in MRSA infection once screening programs were introduced [23]. A meta-analysis of ten studies across different specialties was more guarded demonstrating a relative risk of surgical site infections of 0.69 (95% CI 0.46–1.01) in screened patients [24]. Within orthopaedic surgery, the literature is strongly in favour of screening and decolonization, and this, together with the population-level data, suggests that this practice should continue [9–11, 15, 25].

The cost-effectiveness of screening and eradication is dependent on the prevalence of MRSA within the population concerned. In the UK National Health Service, procedures or practices are considered to be cost-effective if they result in a cost per quality-adjusted life year (QALY) of less than £30,000; whilst screening and eradication of high-risk patients is the most cost-effective strategy, even this only reaches the threshold for cost-effectiveness if the prevalence of MRSA was three times the current level [9]. This was supported by the study of de Wouters et al. who found that conventional criteria for designating a patient at high risk of MRSA were not effective in a population with a low level of colonization overall [26]. A Markov decision analysis performed by Slover et al. reported that in order to be cost saving, screening had to result in a reduction in the rate of revision of arthroplasty cases by 35% to be cost-effective [27]. However, this assumed that the cost of treating an infected arthroplasty was the same as the cost of a primary arthroplasty, which would appear to be a substantial underestimate [28]. A study of the Veterans Affairs program found the cost per QALY to be between $28,000 and $57,000, which was considered to be cost-effective [29]. The huge financial and personal costs associated with PJI would appear to render screening and eradication to be a proportionate and pragmatic course of action.

Whilst most screening and eradication programs focus on MRSA, susceptible strains of S. aureus (methicillin-sensitive Staphylococcus aureus, MSSA) are much more common agents of PJI, and up to a third of people are colonized with such bacteria [16]. Dancer et al. compared the rates of PJI in 6 months before and after extending their preoperative screening program to include MSSA, reporting that rates of deep S. aureus infection fell from 15/213 (6.5%) to 1/307 (0.3%, with that one case being in a patient with a negative screen). The change in policy involved a small change in laboratory procedures and was inexpensive; the authors estimated that the change in infection rates led to an overall saving of £812,559 after taking into account the cost of screening and eradication [16].

These results were supported by the study of Sporer et al. who introduced a combined MRSA/MSSA screening program in 1999 (having not previously screened for either); their retrospective study of 9690 patients demonstrated a reduction in the overall rate of infection from 1.1 to 0.3% after the introduction of the combined screening program [30]. Prior to screening, two thirds of cases of PJI isolated Staphylococcus aureus; this fell to one third following the introduction of screening. Likewise, the study of Malcolm et al. reported a 50% fall in cases of PJI after a combined MRSA/MSSA screening and eradication program was introduced [31].

Some authors have proposed the universal provision of eradication without screening [32]. This has the advantage of being effective against all bacteria, and it does not generate the costs associated with laboratory testing and transport of samples. In the acute setting, it has the advantage of avoiding a lead time for the screening result to become available; it was in this context that Huang et al. recommended routine decolonization for admissions to ITU, where universal decolonization resulted in a significant decrease in the rate of MRSA bacteraemia [32]. In planned orthopaedic surgery, the benefits are more limited, and to our knowledge, there is no study in the literature comparing universal decolonization to screening and decolonization in orthopaedics [9].