Using an antibiotic to prevent MRSA (methicillin-resistant Staphylococcus aureus) infections and related complications in people having surgery

Most bacterial wound infections after surgery heal naturally or after treatment with antibiotics.  Some bacteria are resistant to commonly-used antibiotics, e.g. methicillin-resistant Staphylococcus aureus (MRSA). MRSA infection after surgery is rare, but can occur in wounds (surgical site infections, or SSI), the chest, or bloodstream (bacteraemia), and can be life-threatening. MRSA SSIs occur in 1% to 33% of people having surgery (depending on the type of operation) and result in extended hospitalisation.

Antibiotics can be used individually, or combined, and administered for different durations. To identify the best antibiotic(s), or dose pattern, for preventing development of MRSA infection after surgery, we investigated studies that compared different antibiotics with each other, or with no treatment, to prevent MRSA SSIs. We included only randomised controlled trials (RCTs), and set no limits regarding language, or date, of publication, or trial size. Two review authors identified studies and extracted data independently.

We identified 12 RCTs, with 4704 participants. Eleven trials compared 16 preventative (prophylactic) antibiotic treatments, and one compared antibiotic prophylaxis with no prophylaxis. Generally, MRSA status of the participants prior to surgery was not known.

Four studies reported deaths (14/1401 participants): approximately 1% of participants died from any cause after surgery, but there were no significant differences between treatment groups. Four trials reported on serious antibiotic-related adverse events - there were none in 561 participants. None of the trials reported quality of life, length of hospital stay or use of healthcare resources. Overall, 221 SSIs due to any bacterium developed in 4032 people (6%), and 46 MRSA SSIs developed in 4704 people (1%). There were no significant differences in development of SSIs between the 15 comparisons of one antibiotic treatment against another. When antibiotic prophylaxis with co-amoxiclav was compared with no antibiotic prophylaxis, a significantly lower proportion of people developed SSIs after receiving co-amoxiclav (74% reduction in all SSIs, and 95% reduction in MRSA SSIs).

Two trials reported that 19 participants developed MRSA infection in wounds (SSIs), chest, or bloodstream, but there were no significant differences in the proportion of people who developed them between the two comparisons.

Prophylaxis with co-amoxiclav decreases the proportion of people developing MRSA infections compared with no antibiotic prophylaxis in people without cancer undergoing surgery for feeding tube insertion into the stomach using endoscopy, although this may be due to decreasing overall infection thereby preventing wounds from becoming secondarily infected with MRSA. There is currently no other evidence that either a combination of prophylactic antibiotics, or increased duration of antibiotic treatment, benefits people undergoing surgery in terms of reducing MRSA infections. Well-designed RCTs are necessary to assess different antibiotic treatments for preventing MRSA infections after surgery.

Authors' conclusions: 

Prophylaxis with co-amoxiclav decreases the proportion of people developing MRSA infections compared with placebo in people without malignant disease undergoing percutaneous endoscopic gastrostomy insertion, although this may be due to decreasing overall infection thereby preventing wounds from becoming secondarily infected with MRSA. There is currently no other evidence to suggest that using a combination of multiple prophylactic antibiotics or administering prophylactic antibiotics for an increased duration is of benefit to people undergoing surgery in terms of reducing MRSA infections. Well designed RCTs assessing the clinical effectiveness of different antibiotic regimens are necessary on this topic.

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Background: 

Risk of methicillin-resistant Staphylococcus aureus (MRSA) infection after surgery is generally low, but affects up to 33% of patients after certain types of surgery. Postoperative MRSA infection can occur as surgical site infections (SSIs), chest infections, or bloodstream infections (bacteraemia). The incidence of MRSA SSIs varies from 1% to 33% depending upon the type of surgery performed and the carrier status of the individuals concerned. The optimal prophylactic antibiotic regimen for the prevention of MRSA after surgery is not known.

Objectives: 

To compare the benefits and harms of all methods of antibiotic prophylaxis in the prevention of postoperative MRSA infection and related complications in people undergoing surgery.

Search strategy: 

In March 2013 we searched the following databases: The Cochrane Wounds Group Specialised Register; The Cochrane Central Register of Controlled Trials (CENTRAL); Database of Abstracts of Reviews of Effects (DARE) (The Cochrane Library); NHS Economic Evaluation Database (The Cochrane Library); Health Technology Assessment (HTA) Database (The Cochrane Library); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid EMBASE; and EBSCO CINAHL.

Selection criteria: 

We included only randomised controlled trials (RCTs) that compared one antibiotic regimen used as prophylaxis for SSIs (and other postoperative infections) with another antibiotic regimen or with no antibiotic, and that reported the methicillin resistance status of the cultured organisms. We did not limit our search for RCTs by language, publication status, publication year, or sample size.

Data collection and analysis: 

Two review authors independently identified the trials for inclusion in the review, and extracted data. We calculated the risk ratio (RR) with 95% confidence intervals (CI) for comparing binary outcomes between the groups and planned to calculated the mean difference (MD) with 95% CI for comparing continuous outcomes. We planned to perform meta-analysis using both a fixed-effect model and a random-effects model. We performed intention-to-treat analysis whenever possible.

Main results: 

We included 12 RCTs, with 4704 participants, in this review. Eleven trials performed a total of 16 head-to-head comparisons of different prophylactic antibiotic regimens. Antibiotic prophylaxis was compared with no antibiotic prophylaxis in one trial. All the trials were at high risk of bias. With the exception of one trial in which all the participants were positive for nasal carriage of MRSA or had had previous MRSA infections, it does not appear that MRSA was tested or eradicated prior to surgery; nor does it appear that there was high prevalence of MRSA carrier status in the people undergoing surgery.

There was no sufficient clinical similarity between the trials to perform a meta-analysis. The overall all-cause mortality in four trials that reported mortality was 14/1401 (1.0%) and there were no significant differences in mortality between the intervention and control groups in each of the individual comparisons. There were no antibiotic-related serious adverse events in any of the 561 people randomised to the seven different antibiotic regimens in four trials (three trials that reported mortality and one other trial). None of the trials reported quality of life, total length of hospital stay or the use of healthcare resources. Overall, 221/4032 (5.5%) people developed SSIs due to all organisms, and 46/4704 (1.0%) people developed SSIs due to MRSA.

In the 15 comparisons that compared one antibiotic regimen with another, there were no significant differences in the proportion of people who developed SSIs. In the single trial that compared an antibiotic regimen with placebo, the proportion of people who developed SSIs was significantly lower in the group that received antibiotic prophylaxis with co-amoxiclav (or cefotaxime if allergic to penicillin) compared with placebo (all SSI: RR 0.26; 95% CI 0.11 to 0.65; MRSA SSI RR 0.05; 95% CI 0.00 to 0.83). In two trials that reported MRSA infections other than SSI, 19/478 (4.5%) people developed MRSA infections including SSI, chest infection and bacteraemia. There were no significant differences in the proportion of people who developed MRSA infections at any body site in these two comparisons.

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