The effects of shelf life of sterile instruments on the colony count of instruments sterilized in the Al-Zahra Hospital affiliated to the Isfahan University of Medical sciences Download PDF

Introduction: One of the most important sources and means of transmitting nosocomial infections is improper sterilization of surgical tools and instruments, because contamination transmission through contaminated surgical equipment and tools is one of the main causes of infection in the surgical wound. The present study aimed to investigate the effect of shelf life of sterile instruments on colony count of instruments sterilized. Method: this study was field trial. The population included 66 surgical packs and 66 instruments sterilized in the Hospital Central Supplies. 22 of them were randomly selected according to the considered periods (3, 15 and 30 days for fabric packs and 6, 15 and 30 days for surgical instruments) and colony counting was performed. In order to perform colony counting, a sterile swab plated with normal saline was rotationally rubbed on the 5*6 cm rectangular area of the inner surface of surgical packs and 1*5 cm area of the sterilized instruments packs and then, the swab was returned to normal saline. The specimens were transferred to the laboratory and placed in a medium of Blood Agar and Eosin methylene blue at 35 ° C for 24 to 48 hours. Microorganisms were then examined in terms of type and number. SPSS V.23 Software was used to analyze the data and the data was analyzed using descriptive and analytical statistical tests. Results: average number of colonies counted in the sterile packs opened 30 days after sterilization was greater compared to the sterile packs opened 3 and 15 days after sterilization (p-value0.05) (3 days after sterilization: 68.18±319.80 VS 15 days after sterilization: 113.64±169.86 and 30 days after sterilization: 6527.27±21400.16). Also, no significant difference was observed among the sterilized instruments packs used 6, 15 and 30 days after sterilization (p-value0.05) (6 days after sterilization: 45.45±147.12 VS 15 days after sterilization: 172.73±636.35 and 30 days after sterilization: 172.73±443.13). The bacteria of Coagulase-Negative Staphylococci, Staphylococcus aureus and Bacillus spp were more present in the samples. Conclusion: according to the results, it is recommended that in the studied hospital, the sterilized instruments packs are stored up to 30 days and the sterile packs are stored up to 15 days after sterilization that due to the reduction in the repetition of sterilization, this results in the economic savings and less damage to the packs and tools in the Hospital Central Supplies as well as the reduction in the workload of the personnel of this department. However, given the fact that each package has its unique half-life and number of bacteria, it is suggested to conduct the same study with greater number of specimens.