Detection of Carbapenemases in Pseudomonas aeruginosa Isolates: An Emerging Challenge

Aims: Determine the clinical characteristics of patients and the microbiological characteristics of the Pseudomonas aeruginosa isolates in respiratory samples from Adult Intensive Care Unity (ICU) of a University Hospital from Fortaleza, Brazil; Analyze the resistance profile of Pseudomonas aeruginosa isolates; Determine the phenotypic prevalence of Carbapenem-Resistant Pseudomonas aeruginosa (CRPA); Relate the prevalence to resistent Pseudomonas aeruginosa with patients’ death rate.

Study Design: This is a epidemiological, descriptive and retrospective study, carried out between January and December 2022 at a university hospital in Fortaleza, Brazil.

Place and Duration of Study: Microbiology Sector of the Central Laboratory of the Walter Cantídio University Hospital between January 2022 and December 2022.

Methodology: All tracheal aspirate and bronchoalveolar lavage samples that showed a positive culture for Pseudomonas aeruginosa from patients admitted to the Adult Intensive Care Unit at the Walter Cantídio University Hospital were included in the study. Their identification (ID) and the Antibiotic Sensitivity Test (TSA) were carried out using the automated system VITEK® 2 (BioMérieux®, Marcyl’Etoile, France), which uses the OBSERVA system for data archiving. The detection of carbapenemases production was performed using the immunochromatographic test NG-Test Carba 5 (Laborclin - Centerlab). The data was collected by the Microbiology Sector of the hospital's Central Clinical Analysis Laboratory through patient reports issued by the hospital management system, REDCap. The reports were reviewed by a microbiologist pharmacist from the microbiology service. The data were analyzed and audited in the Excel® program for statistical validation using the SPSS Statistics® program, version 17.0.

Results: After applying exclusion criteria, 25 bacterial isolates from respiratory samples of patients admitted to the Adult ICU of the hospital tested positive for Pseudomonas aeruginosa. 80% (n=20) of these isolates originated from tracheal aspirate samples and 20% (n=5) from bronchoalveolar lavage. Of these 25 isolates, 72% (n=18) were identified as Carbapenem-Resistant Pseudomonas aeruginosa (CRPA), of which NG-Test Carba 5 identified 33% (n=6) as producers of serine carbapenemase, 28% (n=5) as producers of enzyme not identified by the test, 22% (n=4) as producers of metallo-beta-lactamase, and 17% (n=3) as non-enzymatic. Considering only isolates producing serine carbapenemases, 50% showed resistance to ceftazidime/avibactam, 83.3% to amikacin, and 100% to tigecycline and ciprofloxacin. NG-Test Carba 5 identified all isolated serine carbapenemases as KPC producers and all isolated metallo-beta-lactamases as IMP producers. It was found that patients admitted to the Adult ICU with isolates of CRPA with enzymatic resistance mechanism in respiratory samples are related to patient mortality (p < 0.05).

Conclusion: The study highlights high mortality rates and detection of carbapenemases in respiratory samples from patients with Pseudomonas aeruginosa infection in ICUs. The reduced effectiveness of last-line antimicrobial therapies such as ceftazidime-avibactam and the high mortality rate associated with enzymatic resistance in CRPA, underscores the importance of hospital infection control to improve patient care.