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To examine the impact of surgical-site infection (SSI) due to Staphylococcus aureus on mortality, duration of hospitalization, and hospital charges among elderly surgical patients and the impact of older age on these outcomes by comparing older and younger patients with S. aureus SSI.
A nested cohort study.
A 750-bed, tertiary-care hospital and a 350-bed community hospital.
Ninety-six elderly patients (70 years and older) with S. aureus SSI were compared with 2 reference groups: 59 uninfected elderly patients and 131 younger patients with S. aureus SSI.
Compared with uninfected elderly patients, elderly patients with S. aureus SSI were at risk for increased mortality (odds ratio [OR], 5.4; 95% confidence interval [CI95], 1.5-20.1), postoperative hospital-days (2.5-fold increase; CI95, 2.0-3.1), and hospital charges (2.0-fold increase; CI95, 1.7-2.4; $41,117 mean attributable charges per SSI). Compared with younger patients with S. aureus SSI, elderly patients had increased mortality (adjusted OR, 2.9; CI95, 1.1-7.6), hospital-days (9 vs 13 days; P = .001), and median hospital charges ($45,767 vs $85,648; P < .001).
Among elderly surgical patients, S. aureus SSI was independently associated with increased mortality, hospital-days, and cost. In addition, being at least 70 years old was a predictor of death in patients with S. aureus SSI.
Surgical-site infection (SSI) is a serious and costly complication following coronary artery bypass graft (CABG). We analyzed surgical factors, microbiology, and complications at a 608-bed community teaching hospital to identify opportunities for prevention.
All patients undergoing CABG procedures from June 1997 through December 2000 were analyzed. Hospital records and postdischarge surveillance data were reviewed for demographics, surgical information, timing and classification of infection, microbiology, and bacteremic events.
Of 3,443 patients undergoing CABG, sternal SSI developed in 122 (3.5%); 71 (58.2%) were classified as superficial SSI and 51 (41.8%) as deep SSI. Surgical antimicrobial prophylaxis was employed in all cases. On average, infection occurred 21.5 days (range, 4 to 315) after CABG. Most cases were diagnosed on readmission (59%); 20 cases (16%) were identified by postdischarge surveillance. Microbiological data were positive in 109 (89.3%), with a single pathogen implicated in most (86.2%). Gram-positive cocci were most frequently recovered (81%); gram-negative bacilli (17%), gram-positive bacilli (1%), and yeast (1%) were less common. Staphylococcus aureus was the most frequently isolated pathogen (49%). Bacteremia was noted in 22 instances (18%). It was significantly associated with deep SSI (P =. 002) and identified only in S. aureus cases.
SSI complicated 3.5% of the procedures. S. aureus was implicated in most of the cases and was significantly associated with deep SSI. It was the only pathogen associated with secondary bacteremia. In addition to standard guidelines, targeted methods against S. aureus should help reduce the overall rate of SSI.
The Victorian Infection Control Surveillance Project (VICSP) is a multicenter collaborative surveillance project established by infection control practitioners. Five public hospitals contributed data for patients undergoing coronary artery bypass graft (CABG) surgery.
To determine the aggregate and comparative interhospital surgical-site infection (SSI) rates for patients undergoing CABG surgery and the risk factors for SSI in this patient group.
Each institution used standardized definitions of SSI, risk adjustment, and reporting methodology according to the National Nosocomial Infections Surveillance System of the Centers for Disease Control and Prevention. Data on potential risk factors were prospectively collected.
For 4,474 patients undergoing CABG surgery, the aggregate SSI rate was 7.8 infections per 100 procedures (95% confidence interval [CI95], 7.0-8.5), with individual institutions ranging between 4.5 and 10.7 infections per 100 procedures. Multivariate risk factor analysis demonstrated age (odds ratio [OR], 1.02; CI95, 1.01-1.04; P < .001), obesity (OR, 1.8; CI95, 1.4-2.3; P < .001), and diabetes mellitus (OR, 1.6; CI95, 1.2-2.1; P < .001) as independent predictors of SSI. Three hundred thirty-four organisms were isolated from 296 SSIs. Of the total SSIs, methicillin-resistant Staphylococcus aureus was isolated from 32%, methicillin-sensitive S. aureus from 24%, gram-negative bacilli (eg, Enterobacter and Escherichia colt) from 18%, and miscellaneous organisms from the remainder.
We documented aggregate and comparative SSI rates among five Victorian public hospitals performing CABG surgery and defined specific independent risk factors for SSI. VICSP data offer opportunities for targeted interventions to reduce SSI following cardiac surgery.
To identify risk factors associated with the development of surgical-site infection (SSI) following total knee arthroplasty (TKA).
A case-control study.
A 1,100-bed, university-affiliated, tertiary-care teaching hospital.
Case-patients with SSI occurring up to 1 year following primary TKA performed between January 1999 and December 2001 were identified prospectively by infection control practitioners using National Nosocomial Infections Surveillance (NNIS) System methods. Three control-patients were selected for each case-patient, matched by date of surgery. Stepwise logistic regression analysis was used to determine the relation of potential risk factors to the development of infection.
Twenty-two patients with infections (6 superficial and 16 deep) were identified. Infection rates per year were 0.95%, 1.07%, and 1.19% in 1999, 2000, and 2001, respectively. Logistic regression analysis identified two variables independently associated with the development of infection: the use of closed suction drainage (odds ratio [OR], 7.0; 95% confidence interval [CI95], 2.1-25.0; P = .0015) and increased international normalized ratio (INR) (OR, 2.4; CI95, 1.1-5.7; P = .035). Factors not statistically associated with the development of infection included age, NNIS System risk index score, presence of various comorbidities, surgeon, duration of procedure or tourniquet time, type of bone cement or prosthesis used, or receipt of blood product transfusions.
The use of closed suction drainage and a high postoperative INR were associated with the development of SSI following TKA. Avoiding the use of surgical drains and careful monitoring of anticoagulant prophylaxis in patients undergoing TKA should reduce the risk of infection.
Staphylococcus aureus nasal carriage is a risk factor for surgical-site infections (SSIs) caused by S. aureus, and eradication of carriage reduces postoperative nosocomial infections caused by it. No study has compared large groups of preoperative carriers and non-carriers to identify factors that are linked to S. aureus nasal carriage.
While conducting a clinical trial evaluating whether mupirocin prevented S. aureus SSIs, we prospectively collected data on 70 patient characteristics that might be associated with S. aureus carriage. We performed stepwise logistic regression analysis.
Of the 4,030 patients, 891 (22%) carried S. aureus. Independent risk factors for S. aureus nasal carriage were obesity (odds ratio [OR], 1.29; 95% confidence interval [CI95], 1.11-1.50), male gender (OR, 1.29; CI95,1.11-1.51), and a history of a cerebrovascular accident (OR, 1.53; CI95, 1.03-2.25) for all patients. Factors associated with nasal carriage varied somewhat by surgical specialty. In all groups, preoperative use of antimicrobial agents was independently associated with a lower risk of carrying S. aureus in the nares. Previously identified risk factors were not significantly associated with S. aureus nasal carriage in this large group of surgical patients.
Male gender, obesity, and a history of a cerebrovascular accident were identified as risk factors for S. aureus nasal carriage. It remains to be seen whether preoperative weight loss would reduce the rate of nasal carriage. In addition, the value of screening this patient population for S. aureus nasal carriage merits further investigation.
To evaluate the prevalence and risk factors of nasal Staphylococcus aureus (SA) in the community.
Wake Forest University, Winston-Salem, North Carolina.
Four hundred fifty students were screened for nasal SA carriage during the fall of 2000, 2001, and 2002.
Students were screened by nose swabs. A self-administered questionnaire collected information on demographics and medical history. Antibiotic testing and PFGE were performed on isolates. Risk factors were determined by logistic regression analysis.
Of 450 volunteers, 131 (29%) were SA carriers. Antibiotic resistance was high for azithromycin (26%) and low for ciprofloxacin (1%), tetracycline (5%), mupirocin (1%), and methicillin (2%). PFGE patterns were not associated with carriage. Age, male gender, white race, medical student, allergen injection therapy, chronic sinusitis, rheumatoid arthritis, hospitalization for 6 months or less, and use of antibiotics were associated with carrier status by univariate analysis. Stepwise multivariate logistic regression led to a best fitting model with older age (OR, 1.04; CI95, 1.005-1.079), male gender (OR, 1.50; CI95, 0.982-2.296), and chronic sinusitis (OR, 2.71; CI95, 0.897-8.195) as risk factors. Antibiotic use (< 4 weeks) (OR, 0.41; CI95, 0.152-1.095) and allergen injection therapy (OR 0.41; CI95, 0.133-1.238) were protective. Analyses of carriers revealed candidate factors for persistent carriage to be nasal SA colonization rate and male gender. Factors for azithromycin resistance were non-medical students and antibiotic use in the past 6 months.
Older male volunteers suffering from chronic sinusitis and not taking antibiotics were at higher risk for carrying SA.
To implement a comprehensive infection control (IC) program for prevention of cardiac device-associated infections (CDIs).
Prospective before-after trial with 2 years of follow-up.
A tertiary-care, university-affiliated medical center.
A consecutive sample of all adults undergoing cardiac device implantation between 1997 and 2002.
An IC program was implemented during late 2001 and included staff education, preoperative modification of patient risk factors, intraoperative control of strict aseptic technique, surgical scrubbing and attire, control of environmental risk factors, optimization of antibiotic prophylaxis, postoperative wound care, and active surveillance. The clinical endpoint was CDI rates.
Between 1997 and 2000, there were 7 CDIs among 725 procedures (mean annual CDI incidence, 1%). During the first 9 months of 2001, there were 7 CDIs among 167 procedures (4.2%; P = .007): CDIs increased from 7 among 576 to 3 among 124 following pacemaker implantation (P = .39) and from 0 among 149 to 4 among 43 following cardioverter-defibrillator implantation (P = .002). Of the 14 CDIs, 5 involved superficial wounds, 7 involved deep wounds, and 2 involved endocarditis. Following intervention, there were no cases of CDI among 316 procedures during 24 months of follow-up (4.2% reduction; P = .0005).
We observed a high CDI rate associated with substantial morbidity. IC measures had an impact on CDI. Although the relative weight of each measure in the prevention of CDI remains unknown, our results suggest that implementation of a comprehensive IC program is feasible and efficacious in this setting.
To investigate a Staphylococcus epidermidis outbreak among patients undergoing cardiac surgery.
Retrospective cohort study.
A 260-bed community referral center.
Case-patients were patients with S. epidermidis mediastinals, endocarditis, or both after valve implantation at Hospital de La Ribera from January to June 2002. The study population included patients undergoing valve surgery at Hospital de La Ribera from January 2000 to June 2002.
From January to June 2002, 8 cases of mediastinals, endocarditis, or both occurred among 53 patients undergoing cardiac surgery. In the same months of 2000, there had been no cases among 22 patients, and in 2001, only 1 case among 47 patients (P = .095 and P = .034, respectively). In 2002, there were 4 cases of mediastinitis and endocarditis, 3 cases of medi-astinitis, and 1 case of endocarditis, all following aortic valve replacement. The epidemic curve suggested a protracted outbreak. Patients with chronic obstructive lung disease were sixfold more likely to be case-patients (95% confidence interval, 1.6-23.8). The mean duration of surgery tended to be longer in non-case-patients (161.4 ± 57.9 minutes) than in case-patients (123.7 ± 23.7 minutes) (P = .06).
The cause of this protracted outbreak was likely multifactorial. Reemphasis of existing policies was associated with resolution of the outbreak.
To investigate whether rhinovirus infection leads to increased airborne dispersal of coagulase-negative staphylococci (CoNS).
Prospective nonrandomized intervention trial.
Wake Forest University School of Medicine, Winston-Salem, North Carolina.
Twelve nasal Staphylococcus aureus-CoNS carriers among 685 students screened for S. aureus nasal carriage.
Participants were studied for airborne dispersal of CoNS in a chamber under three conditions (street clothes, sterile gown with a mask, and sterile gown without a mask). After 2 days of pre-exposure measurements, volunteers were inoculated with a rhinovirus and observed for 14 days. Daily quantitative nasal and skin cultures for CoNS and nasal cultures for rhinovirus were performed. In addition, assessment of cold symptoms was performed daily, mucous samples were collected, and serum titers before and after rhinovirus inoculation were obtained. Sneezing, coughing, and talking events were recorded during chamber sessions.
All participants had at least one nasal wash positive for rhinovirus and 10 developed a symptomatic cold. Postexposure, there was a twofold increase in airborne CoNS (P = .0004), peaking at day 12. CoNS dispersal was reduced by wearing a gown (57% reduction, P < .0001), but not a mask (P = .7). Nasal and skin CoNS colonization increased after rhinovirus infection (P<.05).
We believe this is the first demonstration that a viral pathogen in the upper airways can increase airborne dispersal of CoNS in nasal S. aureus carriers. Gowns, gloves, and caps had a protective effect, whereas wearing a mask did not further reduce airborne spread.
Fifteen (8.4%) of 179 patients admitted with femoral neck fractures carried MRSA Among 96 patients admitted from their homes, only 2 (2%) were carriers, whereas 13 (15.6%) of 83 patients from nursing or residential homes or long-term-care facilities were colonized (P = .001). Routine prophylaxis with vancomycin is recommended in the latter group.
In 2001, 7.58% of our coronary artery bypass graft (CABG) patients developed surgical-site infection (SSI) as compared with 3.57% in National Nosocomial Infections Surveillance System hospitals from January 1992 to June 2001. Seven new preventive measures were implemented and in 2002, the rate was 3.47%. Implementing evidence-based measures improved patient outcomes.
To determine whether postoperative urinary infections were related to shaving before undergoing endoscopic urological surgery, 90 patients were randomly assigned to shaving or not shaving. Urinary cultures revealed infection in 10 patients. Half of them had been shaved, suggesting that this practice does not affect the incidence of urinary infections.