Objective: In May 2013, an abnormal increase of surgical-site infection among post cesarean section patients was reported at one hospital in Zhongshan. An investigation was conducted to identify the risk factors and related control measures., Methods: All the reported surgical-site infection records among post cesarean section patients were checked. A review of cesarean section schedules of health workers was also performed. An 1 : 2 case-control study was conducted among surgical-site infection cases in May 2013. Microbiologic cultures were performed on 2 surgical site secretion samples and 12 samples from the environment. All the positive isolates were molecular typed by pulsed field gel electrophoresis (PFGE)., Results: In May 2013, 4 post cesarean section patients who developed surgical-site infection symptom at one hospital in Zhongshan were reported, with an attack rate as 10.3% (4/39). The emergence time of symptom was 2-3 days after operation. All of the 4 cases underwent an emergency operation. The median time interval for cases from admission to operation was 7.2 hours (ranged from 2 to 9 hours), lower than that seen in the controls, with a median time of 20.8 hours (Z = 5.50, P = 0.03). Two of the 4 cases took type-B ultrasonic inspection 1.4 h and 8.4 h before the operation, and the other two cases took continuous fetal heart monitoring 2 hours before the operation. Skin of the operation area on the 4 cases had been exposed to ultrasonic couplant, without a thorough clean. The proportion of type-B ultrasonic inspection or continuous fetal heart monitoring was much higher in cases than in controls (χ² = 5.19, P = 0.01). Burkholderia cepacia (BC) isolates were discovered from:one surgical site secretion, 2 type-B ultrasonic probe samples, one ultrasonic couplant in use and one ultrasonic couplant unopened. All the isolates were identified as 100% identical by PFGE., Conclusion: The skin of operation area of cesarean section patients had been exposed to BC contaminated ultrasonic couplant without thorough cleaning, which seemed to be related to the outbreak of surgical-site infection, in our case.