Molecular characterization of carbapenemase-encoding genes in carbapenem-resistant Pseudomonas aeruginosa isolated from clinical samples in Yaoundé, Cameroon.

The surge in Carbapenem resistant Pseudomonas aeruginosa strains has significantly narrowed treatment options, a trend mainly driven by the production of carbapenemases disseminated through mobile genetic elements. Alarmingly, Cameroon has witnessed an increase in the spread of carbapenemases-producing Pseudomonas aeruginosa isolates, highlighting a pressing public health issue. These strains are known to cause outbreaks, and their isolation continues to increase. In Cameroon, however, there are limited data on the resistance profiles of circulating Carbapenem-resistant Pseudomonas aeruginosa isolates in the city of Yaoundé. This study aimed to determine the distribution, susceptibility profile and molecularly characterized carbapenemase-encoding genes in Carbapenem-resistant P. aeruginosa (CRPA) isolates recovered across six health facilities in Yaoundé, Cameroon. An analytical cross-sectional study was conducted over nine months (November 2023 to July 2024). Carbapenem-resistant Pseudomonas aeruginosa isolates from clinical specimens were collected and re-identified. After culturing on Cetrimid and Nutrient Agar, biochemical identification was done using the Analytical Profile Index 20 Non-Enteric System. Antimicrobial susceptibility testing was performed to assess resistance to carbapenems and other antibiotics. Carbapenemase and extended-spectrum beta-lactamases production in Carbapenem resistant Pseudomonas aeruginosa was detected using the Carbapenem inhibition and Combined disc methods.  Later on, the carbapenemases genes were detected via conventional polymerase chain reaction. We collected 416 Gram negative bacilli from the six tertiary hospitals in Yaounde; of the 416 initially collected, 217 were oxidase positive. Consistently, of these 217 isolates, 125 were confirmed as P. aeruginosa (representing 57.6 %), with 31.2 % (39/125) resistant to Carbapenems. Among these, 48.7 % (19/39) were resistant to Imipenem, and 51.3 % (20/39) were resistant to Meropenem. Carbapenemase production was observed in 46.2 % (18/39), while co-production of carbapenemases and extended-spectrum beta-lactamases was observed in 28.20 % (11/39).  High resistance was also seen to Cephalosporin (54.4 %) and Penicillin (59.2%). A majority of Carbapenem-resistant Pseudomonas aeruginosa isolates had a multiple antibiotic resistance index ≥ 0.2. The blaVIM gene was detected in 11 isolates (28.21 %), representing the most frequently identified carbapenemase in our study.  Specifically, we found that 5 isolates (12.82 %) expressed blaDIM, 3 isolates (7.69 %) presented blaKPC, 2 isolates (5 .13 %) displayed blaOXA-50, while blaNDM-1 and blaIMP were both found in 1 isolate (2.56 %) each. Consistently, the majority of isolates (n = 22, or 56.4 %) carried a single resistance gene. This study underscores the growing public health concern posed by Carbapenem-resistant Pseudomonas strains and provides evidence of the circulation of carbapenem resistant P. aeruginosa strains mediated by enzymatic resistance mechanisms in Yaoundé, Cameroon. Enhanced surveillance is crucial to curb the dissemination of these strains. There is an urgent need for innovative therapeutic strategies, antimicrobial stewardship and surveillance is imperative.