Polymyxin B has been considered to be the last line of defense for life-threatening infections caused by multiple drug resistant gram-negative pathogens, including carbapenem-resistant Pseudomonas aeruginosa (CRPA). The present study analyzed CRPA resistance to polymyxin B in the Suzhou district of China. Additionally, polymyxin B resistance rates were compared in different parts of the world to determine global trends. The present study also assessed the reliability and effectiveness of the Etest ® in a clinical setting, as laboratories lack a reliable and efficient susceptibility test for polymyxin B. The susceptibility rate of polymyxin B reached 96.0%, which is in accordance with results obtained from the United States of America, Europe, Africa and the majority of Asian countries. However, the rate of polymyxin B non-susceptibility (resistant or intermediate) in Singapore is 0.53 (95% confidence interval, 0.12-0.93). In addition, the susceptibility rate of polymyxin B determined via Etest ® was not significantly increased compared with that determined via broth microdilution (98.0 vs. 96.0%; P= 0.558). Essential and categorical agreement rates reached 98.0%. In conclusion, the polymyxin B resistance rate of CRPA isolates is relatively low in the majority of countries, with the exception of Singapore. Furthermore, Etest ® may be a reliable clinical method for the measurement of polymyxin B resistance in CRPA isolates.

Background: Multi-dose eye drops are easily contaminated by microorganisms, and reportedly, the highest contamination rate can reach 96.46%. The use of contaminated eye drops can cause serious eye infections.Methods: Carteolol hydrochloride eye drops provided by glaucoma patients who visited the ophthalmic clinic of the First Affiliated Hospital of Soochow University from May 2018 to December 2019 were collected. Microbial culture was carried out on the eye drops, and the microbial species were identified by standard procedures. At the same time, the unsealing time, storage method, hand cleaning before dripping, and contact with the eyelid or the surrounding environment during infusion were recorded. Univariate and multivariate logistic regression analyses were used to analyze the risk factors associated with the contamination of carteolol hydrochloride eye drops.Results: A total of 244 bottles of carteolol hydrochloride eye drops were collected, and the positive rate of flora culture was 6.6%. A total of 18 strains of bacteria were isolated. The most common bacteria were Staphylococcus epidermidis and Corynebacterium. Univariate analysis showed that the risk factors associated with contamination were the unsealing time, the frequency of daily use, contact with the eyelid or the surrounding environment during the infusion process, and the use of more than 2 kinds of eye drops at the same time. Multivariate analysis showed that the unsealing time, the frequency of daily use, and contact with the eyelid or the surrounding environment were independent risk factors associated with contamination. Conclusions:A long unsealing time, frequent use, and non-standard operation can increase the risk of eye drop contamination, which cannot be ignored.