Antimicrobial Resistance Profile and Genetic Profiling of Pseudomonas aeruginosa Strains Obtained from Different Inpatient Wards at Kenyatta National Hospital

This study sought to determine the antimicrobial susceptibility profiles of Pseudomonas aeruginosa isolates from inpatients populations at the Kenyatta National Hospital. A total of 188 P. aeruginosa strains were obtained from different inpatient wards from August 2015 to January 2016. Minimum inhibitory concentrations (MICs) were conducted on the Vitek 2-Compact (Biomereux company-France). P. aeruginosa ATCC 27853 and E. coli ATCC 25922 were used as reference strains for drug resistance testing and interpretation done based on the CLSI 2017 guideline. High resistance was recorded towards Tetracycline (92%) with an MIC of ≥ 128μg/ml followed by Cefotaxime (88.8%) and Ceftriaxone (86.2%) with MICs of ≥ 64μg/ml. Lowest resistance was recorded towards Piperacillin (25%) and Amikacin (46.3%). Pseudomonas aeruginosa isolates recovered from the Critical care unit (CCU) recorded the highest resistance of 83% to all the antimicrobial tested while least resistance was observed in strains from the Newborn unit (NBU) ward (38%). On the other hand, isolates obtained from urine (92%) sample were the most resistant while lowest resistance was recorded from blood samples (29%). PCR screening revealed 68 Metallo β-lactamase (MBL) positive strains amongst 127 isolates that were Meropenem resistance. Resistance to Aztreonam amongst the 68 MβL positive producers was 89.7%. Resistance to CAZ, CIP, CN, and AMK was 82.4%, 80.9%, 88.2% and 78% respectively. At least 52(76.5%) of these MβL positive isolates were recovered from patients in the Critical Care Unit. Among the total 188 recovered P. aeruginosa, 48 (25.5%) carried class-1 integron with a single strain among them also harbouring a class-3 integron. Carriage of integron among the 64 blaVEB positive isolates was 70.3%. Among the 68 isolates that were positive for blaNDM, 47 (69.1%) carried class-1 integron. Overall, 45 (23.9%) among the 188 P. aeruginosa isolates were positive for a co-carriage of blaNDM, blaVEB, and class I integron. Plasmid screening revealed 3 types of incompatibility groups. One P. aeruginosa isolate had both incW and incFIB, while another isolate had an incN. Phylogenic cluster analysis using the Gelcompar2® revealed four major clusters based on age, specimen type and wards. The four clusters had a significant genetic similarity of >80% amongst P. aeruginosa strains obtained from different wards which is indicative of cross-infection.