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Duncan A. Friedman, John O. Mason, III, Tracy L. Emond, Lindsey R. Wallace; Potential for Iatrogenic Contamination of Sterile Conditions During Intravitreal Injection. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1695.
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Endophthalmitis is a devastating complication of any intravitreal injection. Although the possibility is approximately 1/6000, any effort to reduce the chance of endophthalmitis is beneficial to the patient (Mason et al, 2008). Efforts to reduce iatrogenic factors that could increase the likelihood of endophthalmitis are at the forefront of current research for proper injection methods (Mason et al, 2010). One current hypothesis is that oral flora from clinicians could contaminate the surgical field, increasing the possibility of intravitreal seeding. We believe that iatrogenic contamination does not play a significant role in field contamination.
Using a previously described experimental culture method, we exposed sterilized 30 gauge needles to different potential sources of contamination. Cultures were taken from needles in three conditions: 1) taken directly from the package, 2) a physician speaking directly in front of the needle for 30 seconds, and 3) needles exposed to the same physician’s breathing for 30 seconds. These needles were then inoculated onto blood and chocolate agar and allowed to incubate at 37 degrees for 6 days. A control throat swab was also cultured using this same method.
A total of 45 plates were divided evenly between the 3 conditions (15 blood and chocolate plates per group). None of the plates in Group 1 (sterile needle) grew positive cultures. Only one plate in each of the other groups grew a colony forming unit. The control plate grew 335 and 180 colony forming units on blood and chocolate agar, respectively. Compared to the control plate the experimental groups had a significant absence of growth (p<0.0001). The control plate grew predominantly Gram positive organisms.
The needles exposed to normal conditions during office based injections (i.e., talking and breathing), did not yield substantial growth of colony forming units. Compared to a direct throat culture, there was a significant absence of growth from any of the needles inoculated onto culture media. Based on our observations, it appears that normal oral flora is not a major source for needle contamination during intravitreal injections.
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