Department of Biomedical Sciences, University of South Alabama, 5721 USA Dr. N, Mobile, AL 36688.
J Med Imaging Radiat Sci. 2020 Dec;51(4):590-598. doi: 10.1016/j.jmir.2020.08.016. Epub 2020 Sep 15.
Thermoplastic immobilization masks used during radiation therapy treatment have been shown to harbor several different types of bacteria. Recovered bacteria included Staphylococcus aureus, Enterococcus species, Gram-negative rods, coagulase-negative staphylococci, and several different Bacillus species. Two of the recovered Bacillus bacteria were examined for their ability to attach to and survive over time on patient head-only masks from four different manufacturers. B. halosaccharovorans was recovered from a treatment facility's water bath while B. cereus was recovered from a patient mask in the same facility. Bacillus bacteria were chosen for this study due to their capability to form dormant spores.
Inoculums containing either B. halosaccharovorans or B. cereus bacteria were seeded onto predesignated areas of each test mask. Masks were subsequently sampled at intervals of 1-h, 1 week, 2 weeks, 3 weeks, and 4 weeks. Recovered bacterial numbers at each sampling interval were determined using the direct plate count method. Spore stains were made of both bacterial isolates and number of detected spores were enumerated.
B. halosaccharovorans attached to each mask type after a 1-h contact time at a number 3X greater than B. cereus. B. halosaccharovorans was also recovered at a number 8.5X greater than B. cereus after 4 weeks. Variation was seen in the attachment capability of each bacterium on tested mask types. Both bacilli were recovered from all 4 masks at each sampling interval including week 4. Examination of spore stains of each bacteria demonstrated nearly a 25:1 ratio of B. halosaccharovorans spores over B. cereus.
The large variation seen between B. halosaccharovorans and B. cereus capability to attach to each of the four tested masks is revealing, especially when it is combined with determined spore numbers. It suggests that spores play a role in mediating their attachment to mask surfaces. Moreover, the recovery of both bacteria from stored masks after 4 weeks indicates a continued presence of dormant spores since growth-supportive nutrients are lacking. It also implies the potential for their transfer to a patient wearing a contaminated mask during a treatment session.
The demonstrated ability of these two Bacillus bacteria to attach to and reside on patient masks presents a dilemma. Routine cleaning with approved disinfectants may not be sufficient to eliminate dormant spores on masks surfaces. This matter requires further investigation. For now, a small modification to the routine mask cleaning procedure before its application may help to reduce the possibility of spore transfer.
放射治疗过程中使用的热塑性固定面罩已被证明可容纳多种不同类型的细菌。回收的细菌包括金黄色葡萄球菌、肠球菌、革兰氏阴性杆菌、凝固酶阴性葡萄球菌和几种不同的芽孢杆菌。从四个不同制造商的患者仅戴头罩中回收了两种芽孢杆菌，以检查它们附着和随时间存活的能力。从治疗设施的水浴中回收了 B. halosaccharovorans，而从同一设施中的患者面罩中回收了 B. cereus。选择芽孢杆菌进行这项研究是因为它们能够形成休眠孢子。
将含有 B. halosaccharovorans 或 B. cereus 细菌的接种物接种到每个测试面罩的预定区域。随后在 1 小时、1 周、2 周、3 周和 4 周的时间间隔处采样。使用直接平板计数法确定每个采样间隔的回收细菌数量。对两种细菌分离物进行了孢子染色，并对检测到的孢子数量进行了计数。
B. halosaccharovorans 在与每种面罩类型接触 1 小时后附着在每个面罩类型上的数量是 B. cereus 的 3 倍。4 周后，B. halosaccharovorans 的回收数量也比 B. cereus 多 8.5 倍。每种细菌在测试面罩类型上的附着能力都存在差异。在每个采样间隔，包括第 4 周，从所有 4 个面罩中均回收了两种芽孢杆菌。对每种细菌的孢子染色的检查表明，B. halosaccharovorans 孢子的数量几乎是 B. cereus 的 25:1。
B. halosaccharovorans 和 B. cereus 附着在四种测试面罩上的能力之间存在较大差异，这一点很明显，尤其是当与确定的孢子数量结合起来时。这表明孢子在调节其附着到面罩表面方面发挥了作用。此外，在 4 周后从储存的面罩中回收两种细菌表明，由于缺乏生长支持性营养物质，休眠孢子仍然存在。这也意味着它们在治疗过程中转移到佩戴受污染面罩的患者的可能性。
这两种芽孢杆菌附着并存在于患者面罩上的能力提出了一个难题。使用批准的消毒剂进行常规清洁可能不足以消除面罩表面的休眠孢子。这需要进一步调查。目前，在应用面罩之前对常规面罩清洁程序进行微小修改可能有助于降低孢子转移的可能性。
