Investigation of Carbapenemase Production Among Carbapenem-Resistant Pseudomonas aeruginosa Isolates

Background: Pseudomonas aeruginosa is an opportunist organism that causes potentially life threatening nosocomial infections, particularly in immunocompromised patients. Carbapenems are regarded to be the last line of treatment against severe infections caused by multi drug resistant P. aeruginosa isolates. isolates. Production of the carbapenemase enzyme is the primary mechanism of carbapenem resistance and has become a serious health concern worldwide as these enzymes are highly transferable and limit therapeutic alternatives. Rapid detection of carbapenemase production is important for prompt planning the treatment of car-bapenemase-producing isolates and preventing the spread of these strains. This study aimed to investigate carbapenemase produc-tion in carbapenem resistant Pseudomonas aeruginosa isolates by the Carbapenem inactivation method. Materials and Methods: In this retrospective study a total of 172 Pseudomonas aeruginosa isolates were obtained from different samples sent from various clinics to Tokat Gaziosmanpaşa University Research and Application Hospital Microbiology Laboratory between 2016-2019 and were evaluated. Of the 172 isolates, 51 (29.7%) were found to be carbapenem- resistant and included in this investigation. Identification and antibiotic susceptibility tests of the isolates were performed with the Vitek 2 (Biomerieux, France) automated system. Carbapenem sensitivities were also determined by the disc diffusion method. Carbapenemase production in isolates was investigated by the Carbapenem inactivation method. Results: These samples were sent from clinical units, such as neurology (n =10), general surgery (n =8), internal medicine (n =7), and pediatric (n =6). The isolates were identified from wounds (n = 17), sputum (n = 15), blood (n = 11), urine (n = 5), and cerebrospinal fluid (n = 3) samples. Of all the carbapenem –resistant samples 32 (62.8%) were obtained from male, and 19 (37.3%) from female patients. Of the 51 carbapenem resistant isolates, 38 (74.5%) were found to be resistant to both imipenem and meropenem. Eight (15.7%) isolates were found to be resistant to imipenem only, and five (9.8%) isolates were resistant to meropenem. Carbapenemase production was detected in 31 (60.8%) isolates by using using the Carbapenem inactivation method. The antibiotic resistance rates of the carbapenem-resistant isolates were as follows: piperacillin-tazobactam 65%, amikacin 6.8%, gentamicin 15.2%, ceftazidime 34.6%, cefepime 38.3%, ciprofloxacin 26.7%, levofloxacin 24.2%. Conclusions: Rapid identification of carbapenemase enzymes among carbapenem resistant Pseudomonas aeruginosa isolates using phenotypic and genotypic approaches is important to control the transmission of infection caused by carbapenem-resistant isolates and to control the morbidity and mortality associated with them. In this study, the carbapenem inactivation test was seen as a method that can be preferred in the laboratory in terms of its easy and fast application in the detection of carbapenemase production. Key Words: Pseudomonas aeruginosa, Carbapenem inactivation method, Antimicrobial resistance