Purpose: Infection and transmission of carbapenem-resistant Aeromonas  is a serious threat to public health. Rapid and accurate detection carbapenem-resistant of these organisms is essential for reasonable treatment and infection control. This study aimed to find a simple and effective method to detect carbapenem-resistant phenotype in Aeromonas .
Methods: A total of 131 clinical preserved Aeromonas  strains were used in this study. The carbapenemase genes were detected by PCR. Modified carbapenem inactivation method (mCIM) in conjunction with EDTA-modified carbapenem inactivation method (eCIM) and simplified carbapenem inactivation method (sCIM) were performed to detect carbapenemases. We also designed a simple method, carbapenem inactivation method using supernatant (CIM-s), to detect the carbapenemase activity in the medium.
Results: Of the 131 Aeromonas  strains, 79 contained carbapenemase genes, including 68 bla _CphA , 6 bla _KPC-2 , 2 bla _NDM-1  and 3 bla _KPC-2+CphA . However, routine antibiotic susceptibility testing could not completely identify carbapenemase-producing Aeromonas . In phenotypic assays, the sensitivity and specificity of mCIM were 100%. The combined mCIM and eCIM could distinguish serine carbapenemase and metallo-β-carbapenemases except co-producing organisms. The sensitivity and specificity of sCIM were 92.4% and 100%, respectively, which could not detect CphA totally. CIM-s results indicate that these carbapenemases could secrete into the medium to perform their hydrolytic activities and had a sensitivity and specificity of 97.5% and 100%, respectively.
Conclusion: The combination of mCIM and eCIM can effectively detect and distinguish different types of carbapenemase in Aeromonas , and could be used as an important supplement approach to the antibiotic susceptibility testing.
Keywords: Aeromonas , modified carbapenem inactivation method, carbapenemase, multidrug resistant, phenotypic detection