Screening for nasal carriage of Staphylococcus aureus among patients scheduled to undergo orthopedic surgery : Incidence of surgical site infection by nasal carriage

Background: Staphylococcus aureus (S. aureus), including MRSA, is considered to be the leading cause of surgical site infection (SSI) after orthopedic surgery. We screened for nasal carriers of S. aureus among patients who were scheduled to undergo orthopedic surgery at our hospital to reveal the effect of nasal S. aureus carriage on SSI. Our study design clearly has the intent of finding S. aureus nasal carriage and eradicating MRSA when found, and this strategy is to verify whether it's effective for preventing orthopedic surgical infections.
Methods: Subjects were 4148 patients who underwent preoperative screening for nasal carrier and subsequently underwent orthopedic surgery during a 7-year period between April 2007 and March 2014. The incidence of SSI among patients who were operated in our department was investigated, and the rates were compared between patients with and without nasal carriage to reveal the effect of preoperative nasal carriage on SSI.
Results: In total, 1036 patients were nasal carriers of S. aureus (carriage rate, 25.0%), whereas 140 patients carried MRSA (carriage rate, 3.4%). SSI developed in 24 patients [incidence, 0.58% (24/4148)] consisting of 12 non-carriers [0.39% (12/3112)] and 12 carriers [1.16% (12/1036)] with a significant difference in the incidence between the groups. Among 24 cases of SSI, more than half (13 cases) were caused by bacterial species other than S. aureus or those that could not be detected by the tests used. Only 7 patients out of 24 SSI patients, S. aureus was the bacterium detected in preoperative nasal cultures and the causal bacterium for SSI (concordance rate of 29.2%)
Conclusions: It was difficult to reduce the incidence rate of SSI in eradication group to the same level as nasal culture negative group. However, nasal carriage of S. aureus or MRSA may be a risk factor for SSI in orthopedic surgery.

内容要旨・審査要旨・論文本文の公開
本論文は, 著者Masaru Nakamuraの学位論文として提出され, 学位審査・授与の対象となっている。