This study was conducted to determine the effect of using IC in decreasing ABCPs of PSBTs and comparing it with the recommended Two-drape method by AORN. Hence, we designed a number of hypotheses about the effect of covering which outlined such as falling.
(1) The results of our study regarding the first hypothesis that covering the PSBTs in an OR during static and dynamic testing would significantly decrease the bioburden of ABCPs settling on surface of them, showed covering PSBTs in the OR during static and dynamic testing (time-points 60, 120, 180, 240 min and 24 hours) resulted in a significantly decreased ABCPs on the PSBTs (P < 0.05). In line with our findings, Markel et al. (12) have shown to covering the PSBTs during static and dynamic OR conditions resulted in a significantly decreased bioburden of ABCPs on the PSBTs in time-points 60 min, 4 and 8 hours (above cover 1, 5.5; IQR, 9.5; beneath cover 1, 0; IQR, 1; P < .0001; above cover 2, 14; IQR, 22.5; beneath cover 2, 0; IQR, 0.25; P < .0001).
Also, their study showed no difference in the bioburden of ABCPs beneath the covers, when the sterile plastic and paper covers were directly compared (P = 0.1). At 24 hours, their results of study showed no significant difference bioburden of ABCPs above and beneath the cover of PSBTs at 24 hours (above cover, 0; IQR, 0.25; beneath cover, 0; IQR, 0; P = 0.1) and it was inconsistent with results of our study (Group 2, P = 0.004; Group 3, P = 0.0001).
That seems possible reason this discrepancy to be that our study at 24 hour tests were performed in OR, whereas the 24-hour test in study Markel et al. was performed in adjacent of an OR, where foot traffic and the possibility of contamination PSBTs were higher.
In line with our findings, Qvistgaard et al. (11) indicated that to cover PSBTs properly with at least a single-layer drape before a surgical procedure is good practice but, it is a better option to support them with a double-layer drape. Because, covering with double-layer drape are significantly reduced the CFUs/plate compared to the single-layer drape.
A study by Wistrand et al. (20) showed that the uncovered PSBTs had 98 CFUs/plate versus 20 in the covered PSBTs during static periods (P < 0.0001). Also, they declared protecting PSBTs from ABCPs with sterile covers enhances the durability of their sterile items up to 24h.
Our study showed no statistical difference between the bioburden of ABCPs on top of each of the covers in Group 2 ,3 and PSBTs no cover in Group 1 at all (P < 0.05). These results were in line with findings of Markel et al. (12) (P = 0.19). So, the bacterial bioburden on PSBTs no cover was equivalent to the bioburden on top of each cover in Group 2 and 3, again confirming there was no break or bias in our methodology.
In the present study the most common bacteria detected on the plates were CoNS (n:1801 [46.6%]). In line with the present study, earlier studies have shown the most common bacteria detected on the contaminated instruments had CoNS 60.4% (28) and 44% (16). Because, CoNS were frequently isolated from air samples obtained throughout the OR room, they were recovered from 86% of air samples (24).
(2) The results of our study regarding the second hypothesis that using IC would be more effective in decreasing the bioburden of ABCPs compared to Two-drape method during static and dynamic testing, showed no significant difference in the bioburden of ABCPs beneath the covers, when group 2 and 3 at the mentioned time points were directly compared (P < 0.05). The use of Two-drape method currently recommends by AORN while, our findings showed there is no preference for using IC compared to Two-drape method. But, due to economic issues may many hospitals may resist to cover PSBTs by Two disposable drapes and prefer our transparent and cost effective IC to a non-transparent cover in Two-drape method.
(3) The results of our study regarding the third hypothesis that starting ABC of the uncovered PSBTs (Group 1) during static testing would have longer compared to the same PSBTs during dynamic testing, showed contamination of PSBTs starts within 0–15 minutes in Group1. There was no statistical difference in the start and mean ABC of PSBTs during static and dynamic periods in Group1(P < 0.05).
While, in real surgery conditions, Uzun et al. (25) showed bacterial growth on PSBTs started after 30 and 60 min in the uncovered (6 of 30 [20%] sets) and covered groups (2 of 30 [6.7%]), respectively (P = 0.024). Dalstrom et al. (16) found that no contamination has occur in the covered group while, rate of 30% contamination appeared in group without cover after 4 hours. The results of both studies was different together, and also was inconsistent with results of our study, and perhaps the differences in starting ABC of the uncovered PSBTs in our study and Two studies else, be related to differences in ORs condition, study deign, and ventilation systems. We did not evaluate the beginning of PSBTs contamination at different time-points in the covered groups, because accessing the covered PSBTs would have disturbed the covers that were being assessed for sterility.
There was a correlation between increasing time (15 to 240 min) and increasing mean contamination of PSBTs with ABCPs during static and dynamic periods in Group1. Also, the mentioned association was seen on top of each of the covers in Groups 2 and 3 during static and dynamic periods, but no such association was seen beneath the covers. In line with our findings, Wistrand et al. (20) showed there was a positive correlation between increasing time (0 to 24 hours) and number of total CFUs/plate (2 to 30) in the group uncovered during static periods, while no such correlation was seen in the covered group (CFUs/plate: 2 to 7). They believed when PSBTs is covered, time has little effect on ABC.
Uzun et al. (25) demonstrated the contamination of uncovered and covered PSBTs increases with over time (uncovered group; contamination rate instrument trays with increasing time was 20% at 30 min vs. 43.4% at 120 min). Hence, covering may serves as a barrier to ABCPs and several research support the covering sterile areas to diminish the potential for contamination in the OR (12, 15, 16). Although, under normal situation, it is rare that surgical instrument trays open and left unattended in the OR unless short delays in begging of surgery occur. In these circumstance, the PSBTs may realistically be covered for a short period before the begin of the surgery (12, 20).