With minimally invasive techniques improving, various types of medical luminal devices are widely used in surgeries. Low-temperature hydrogen peroxide gas plasma sterilizers significantly shorten the sterilization cycle and greatly improve the turnover rate of endoscopic instruments. This study aimed to investigate the effective sterilization of low-temperature hydrogen peroxide gas plasma sterilizers and to explore the applicability of different biological monitoring methods based on medical luminal devices. Basic information of low-temperature hydrogen peroxide gas plasma sterilizers in 58 hospitals across 22 provincial-level administrative divisions (PLADs) was investigated, and these sterilizers were tested with biological process challenge devices (PCD) and normal biological indicators (BI) at the same time to test the effectiveness of sterilization and to compare the monitoring results. The qualification rate, i.e., that the sterilizing process was effective, of biological PCD monitoring was lower than that of common biological monitoring. Therefore, more effective personnel training should be employed for the use of hydrogen peroxide gas plasma sterilizers. In addition, use of biological PCD monitoring when sterilizing tube-type/luminal devices is recommended.
Central sterile supply departments, operating rooms, and endoscopy centers in most of the hospitals are equipped with low-temperature hydrogen peroxide gas plasma sterilizers. However, due to the long lumen and the often-complex structures of luminal devices, they are often improperly sterilized. To understand the effective sterilization of luminal devices sterilized by low-temperature hydrogen peroxide gas plasma sterilizers, a survey was carried out as part of “National Surveillance Program for Hospital Disinfection and Sterilization Effects and Nosocomial Infection” conducted by China CDC. This survey included 58 sentinel hospitals across 22 PLADs of China.
A questionnaire was designed to investigate the low-temperature hydrogen peroxide gas plasma sterilizers, including items needing to be sterilized, and biological monitoring methods, etc.
PCD biological indicators used in this study, which contain a self-contained bacterial tablet with recovery medium and 2 thin plastic tubes, the inner diameter of 1 millimeter and length of 1,000 millimeters, and common self-contained biological indicators were issued to the sentinel hospitals, where the indicating strain was Bacillus stearothermophilus ATCC7953. From June 2015 to December 2019, the investigators from provincial and municipal-level CDCs conducted the examination of sterilizers in the surveyed hospitals.
The following biological monitoring methods were applied: 1) the common biological indicator and PCD biological indicator were placed close to the cabinet door near the lower shelf inside the sterilization chamber and were sterilized with other objects; 2) after a complete sterilization cycle, the two kinds of biological indicators were inoculated in a 56 °C incubator with positive controls and cultured for 48 hours. A positive control culture being observed with a negative test group culture was judged as qualified sterilization, while a positive control culture with a positive test group culture was judged as unqualified sterilization. Statistical analysis was performed using SPSS for Windows (version 19, SPSS Inc., Chicago, Il, USA). The chi-squared test was used to compare the results of biological PCD monitoring with those of general biological monitoring. A P-value of <0.05 was considered to be statistically significant.
A total of 114 questionnaires were collected from 58 sentinel hospitals. Survey results showed that sterilizer use life ranged from 0.5 to 14 years, while about 24.6% of the sterilizers were over 10 years old. In this survey, laparoscopy, cystoscope, arthroscopy, choledochoscope, hysteroscope, and similar luminal devices were included, which implied sterilization by hydrogen peroxide. The tubes for these luminal devices have the smallest diameter of only 1 millimeter and a length of 50–130 centimeters. Low-temperature hydrogen peroxide gas plasma sterilizers are primarily used in central sterile supply departments (63.2%, 72/114), operating rooms (34.2%, 39/114), and endoscopy centers (2.6%, 3/114) (Table 1). All sterilizers are used for sterilization of luminal devices, such as endoscopies. In the survey, 38 sterilizers (33.3%) used biological PCD in daily monitoring, and the remaining 76 sterilizers still used common biological indicators for luminal devices.
Biological PCD monitoring and common biological monitoring were simultaneously conducted 338 times. The qualification rate of biological PCD monitoring was 95.6% (323/338), while common biological monitoring was 99.1% (335/338); the difference was statistically significant (P<0.001, Fisher exact probability test) (Table 2).
Total Secondary CSSD 3 11 14 Operating room 3 8 11 Tertiary CSSD 23 35 58 Endoscopic Center 1 2 3 Operating room 8 20 28 Total − 38 76 114 Note: Biological PCD, the number of sterilizers using biological PCD in daily monitoring for luminal devices. Common BI, the number of sterilizers using common biological indicators in daily monitoring for luminal devices.
Abbreviations: PLADs=provincial-level administrative divisions; PCD=process challenge devices; BI=biological indicators; CSSD=central sterile supply department.
Table 1. Biological monitoring of low-temperature hydrogen peroxide sterilizers in 58 sentinel hospitals across 22 PLADs from June 2015 to December 2019.
Common BI Biological PCD Total Qualified Unqualified Qualified 323 12 335 Unqualified 0 3 3 Total 323 15 338 Note: Biological PCD, the number of sterilizers using biological PCD in daily monitoring for luminal devices. Common BI, the number of sterilizers using common biological indicators in daily monitoring for luminal devices.
Abbreviations: PCD=process challenge devices; BI=biological indicators.
Table 2. Comparison of 338 times biological PCD monitoring and common biological monitoring of low-temperature hydrogen peroxide sterilizers