Risk factors for surgical-site infections following cesarean section.

OBJECTIVE: To identify risk factors associated with surgical-site infections (SSIs) following cesarean sections. DESIGN: Prospective cohort study. SETTING: High-risk obstetrics and neonatal tertiary-care center in upstate New York. PATIENTS: Population-based sample of 765 patients who underwent cesarean sections at our facility during 6-month periods each year from 1996 through 1998. METHODS: Prospective surgical-site surveillance was conducted using methodology of the National Nosocomial Infections Surveillance System. Infections were identified during admission, within 30 days following the cesarean section, by readmission to the hospital or by a postdischarge survey. RESULTS: Multiple logistic-regression analysis identified four factors independently associated with an increased risk of SSI following cesarean section: absence of antibiotic prophylaxis (odds ratio [OR], 2.63; 95% confidence interval [CI95], 1.50-4.6; P=.008); surgery time (OR, 1.01; CI95, 1.00-1.02; P=.04); <7 prenatal visits (OR, 3.99; CI95, 1.74-9.15; P=.001); and hours of ruptured membranes (OR, 1.02; CI95, 1.01-1.03; P=.04). Patients given antibiotic prophylaxis had significantly lower infection rates than patients who did not receive antibiotic prophylaxis (P=02), whether or not active labor or ruptured membranes were present. CONCLUSION: Among the variables identified as risk factors for SSI, only two have the possibility to be changed through interventions. Antibiotic prophylaxis would benefit all cesarean patients regardless of active labor or ruptured membranes and would decrease morbidity and length of stay. Women's healthcare professionals also must continue to encourage pregnant women to start prenatal visits early in the pregnancy and to maintain scheduled visits throughout the pregnancy to prevent perinatal complications, including postoperative infection.

Selection of high-level oxacillin resistance in heteroresistant Staphylococcus aureus by fluoroquinolone exposure.

To study the effect of fluoroquinolone exposure on the expression of mec(A)-encoded oxacillin resistance, population analysis profiling was performed on four strains of fluoroquinolone-susceptible, mec(A)-positive, heteroresistant Staphylococcus aureus. Growth in the presence of 0.5 x MIC of a fluoroquinolone resulted in >10-fold increase in the proportion of the population that grew on agar containing oxacillin 128 mg/L. Ciprofloxacin exhibited a greater effect than moxifloxacin, levofloxacin and gatifloxacin (average 3400-, 220-, 170- and 49-fold increase in oxacillin-resistant colonies versus the control, respectively). The increase was directly proportional to the fluoroquinolone concentration and could be detected as early as 8 h after exposure to the fluoroquinolone. At 8 h, the absolute number of colonies that grew on oxacillin 128 mg/L was similar whether or not the isolate was exposed to the fluoroquinolone, but the total cfu on non-selective media decreased. The resultant oxacillin-resistant colonies also showed a 1.5- to 3-fold increase in fluoroquinolone MIC. No oxacillin resistance was observed on two similarly treated fluoroquinolone-susceptible, mec(A)-negative strains. It appears that fluoroquinolones influence oxacillin resistance by selective inhibition or killing of the more susceptible subpopulations in heteroresistant S. aureus. The surviving populations are more resistant to both oxacillin and fluoroquinolone. The mechanisms of resistance to the two agents may be unrelated but tend to be associated. This could explain in part the observed increases in fluoroquinolone-resistant MRSA.