Plungers of disposable syringes can contact internal surfaces of the syringes with movement of the plungers. We studied bacterial contamination of those syringes after repeated movements of plungers applied with bacteria (methicillin-resistant
Staphylococcus aureus: MRSA). Twenty-five ml of brain-heart-infusion broth were aspirated into 20 ml disposable syringes; thereafter, the protruded sites of the plungers were evenly applied with fluid containing MRSA. The plungers were pushed to empty the media. These procedures were repeated 10 times with each syringe, and each aspiration-emptying procedure was comprised of five syringes. Bacteria grew in the first emptying procedure of the emptied media from one syringe, none in the second procedure, two in the third, and four in the fourth. All syringes were contaminated after five or more aspiration-emptying procedures. In a controlled study, five syringes were applied with bacteria-free fluid in a similar procedure, and almost no syringes were contaminated. We conclude that repeated aspiration-emptying procedures should be avoided when the plungers are contaminated with bacteria in a clinical setting.
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