MRSA鼻部定植可预测胃肠手术部位MRSA感染

圣迭戈(EGMN)——一项大型回顾性研究显示，耐甲氧西林金黄色葡萄球菌(MRSA)鼻部定植与接受大型胃肠道手术患者的手术部位感染和住院时间延长相关，这一结果出乎研究者意料，研究者原以为MRSA在胃肠道中并非常规可见或定植，应该对预后指标的影响很小。

为了评估MRSA鼻部定植与手术部位感染、伤口培养、住院时间和死亡率之间的关系，德克萨斯州Scott and White纪念医院的结直肠外科主任Papaconstantinou博士及其同事回顾了2007年12月~2009年8月在该院接受大型胃肠手术的患者医疗记录。将在入院后24~48 h内接受鼻部拭子检测的患者分为3组：MRSA拭子阳性、甲氧西林敏感金黄色葡萄球菌(MSSA)拭子阳性或两种拭子均为阴性。

结果显示，入选的1,137例患者的平均年龄为59.5岁，73例(6.4%)为MRSA拭子阳性，167例(14.7%)为MSSA拭子阳性，897 例(78.9%)两种拭子均为阴性，MRSA拭子阳性患者的感染发生率最高，为14%，MSSA拭子阳性和两种拭子均为阴性患者的感染发生率分别为4%和9%。

“在校正其他混淆因素后，并未发现鼻部拭子是手术部位感染的独立预测因子，但我们发现，MRSA鼻部定植与手术部位感染中的微生物类型具有很强的关联。”该研究中共获得92例患者的伤口培养数据，在检测为MRSA阳性的患者中，70%的伤口感染来源于MRSA，而在MRSA检测为阴性的患者中，仅有8.5%的伤口感染来源于MRSA。提示鼻部MRSA定植是感染微生物类型的一个指征。

MRSA拭子阳性、MSSA拭子阳性以及两种拭子均为阴性组的住院时间分别为12.5、7.6和8.8天。“通过多重回归分析，我们发现，MRSA拭子阳性是住院时间延长的独立危险因素。”但如果仅限于手术部位感染患者，住院时间由6.2天增至15.7天，各组之间不再有显著差异。相似的，研究人群中的45例死亡患者也均匀分布于各组中。

研究总结认为，MRSA鼻部拭子检测定植阳性是接受大型胃肠手术患者发生MRSA相关手术部位感染的强预测因子。建议在术前对患者进行筛查和治疗定植，以降低术后感染的发生率，并改善患者预后。

Papaconstantinou医生披露与Covidien公司之间存在利益关系。

BY DIANA MAHONEY
Elsevier Global Medical News
Breaking News

SAN DIEGO (EGMN) – Nasal colonization of methicillin-resistant Staphylococcus aureus was linked to an increase in surgical site infections and longer hospital stays in patients undergoing major gastrointestinal surgery in a large retrospective study, a finding that surprised investigators who had hypothesized that nasal colonization of the organism, which is not routinely found or colonized in the GI tract, would have little impact on outcome measures.

“Gastrointestinal operations are different from other surgeries in that infectious pathogens are typically organisms found in the gut, not bacteria that colonize in the skin, which is why we didn’t expect to find a correlation,” lead investigator Dr. Harry T. Papaconstantinou said during a teleconference reporting the results, which he presented on Sunday, May 20, at the annual Digestive Disease Week conference. While it’s unlikely that nasal colonization of MRSA necessarily increases the risk of developing a surgical site infection following GI surgery, “it is possible that it might be an indicator of the type of organism that is involved in the infection.” For example, in the current analysis, wound culture data were available for 92 patients. In patients who tested positive for MRSA, 70% of the wound infections stemmed from MRSA, compared with only 8.5% in of those who tested negative, he said.

To evaluate the relationship between MRSA nasal colonization and surgical site infection, wound cultures, hospital length of stay, and mortality, Dr. Papaconstantinou, chief of colorectal surgery at Scott and White Memorial Hospital in Temple, Texas, and his colleagues examined the records of patients who underwent major GI surgery at the hospital between December 2007 and August 2009. The patients, who also had nasal swab tests within 24-48 hours after admission, were divided into one of three categories: MRSA-swab positive, methicillin-sensitive Staphylococcus aureus (MSSA)–swab positive, or negative for both.

Of the 1,137 patients, mean age 59.5 years, 73 (6.4%) were MRSA-swab positive, 167 (14.7%) were MSSA-swab positive, and 897 (78.9%) were negative, Dr. Papaconstantinou reported. Surgical site infection was identified in 101 patients (8.9%), and the rate of infection was highest, at 14%, in the MRSA-swab positive patients, compared with 4% and 9%, respectively, in the MSSA-swab positive and negative patients, he said. “When we controlled for other confounding factors, we didn’t find nasal swab to be an independent predictor of surgical site infection, but what we did find was a strong relationship between MRSA-positive nasal colonization and type of organism involved [in the surgical site infection].”

Regarding mean hospital length of stay, the respective durations for the MRSA-swab positive, MSSA-swab positive, and the negative groups overall were 12.5 days, 7.6 days, and 8.8 days, representing a significant increase, said Dr. Papaconstantinou. “By multiregression analysis, we found a MRSA-positive swab to be an independent risk factor for extended length of stay.” However, when looking specifically at patients with surgical site infections, the presence of which increased hospital length of stay significantly from 6.2 days to 15.7 days, “there was no between group differences based on nasal swab,” he said. Similarly, the 45 deaths in the study population wee distributed evenly across the nasal swab groups.

Based on the findings, Dr. Papaconstantinou said in an interview, “we can conclude that a positive MRSA nasal swab test for colonization is a strong predictor that MRSA-associated surgical site infections will occur in patients undergoing major GI surgery.” As such, “we propose the possibility that it might be beneficial to preoperatively screen and decolonize these patients in an effort to reduce the incidence of these infections and improve patient outcomes following surgery.” Toward this end, he and his colleagues are anticipating performing such a study and plan on including a cost-benefit analysis to determine whether screening is economically beneficial, he said.

Dr. Papaconstantinou disclosed a financial relationship with Covidien.