Bioburden of Surgical Devices

In general, used medical devices are contaminated with a relatively low bioburden of organisms^{179, 911, 912}. Nystrom evaluated medical instruments used in general surgical, gynecological, orthopedic, and ear-nose-throat operations and found that 62% of the instruments were contaminated with <10¹organisms after use, 82% with <10², and 91% with <10³. After being washed in an instrument washer, more than 98% of the instruments had <10¹organisms, and none >10² organisms⁹¹¹. Other investigators have published similar findings^{179, 912}. For example, after a standard cleaning procedure, 72% of 50 surgical instruments contained <10¹ organisms, 86% <10², and only 6% had >3 × 10²⁹¹². In another study of rigid-lumen medical devices, the bioburden on both the inner and outer surface of the lumen ranged from 10¹ to 10⁴ organisms per device. After cleaning, 83% of the devices had a bioburden £10² organisms¹⁷⁹. In all of these studies, the contaminating microflora consisted mainly of vegetative bacteria, usually of low pathogenicity (e.g., coagulase-negative Staphylococcus)^{179, 911, 912}.

An evaluation of the microbial load on used critical medical devices such as spinal anesthesia needles and angiographic catheters and sheaths demonstrated that mesophilic microorganisms were detected at levels of 10¹ to 10² in only two of five needles. The bioburden on used angiographic catheters and sheath introducers exceeded 10³ CFUs on 14% (3 of 21) and 21% (6 of 28), respectively⁹⁰⁷.