Molecular characterization of Carbapenem-resistance genes among Pseudomonas aeruginosa and Acinetobacter baumannii clinical isolates in Riyadh Download PDF

Background: Antimicrobial resistance in Gram-negative bacteria has been a serious threat and a global problem. Acinetobacter baumannii and Pseudomonas aeruginosa are considered a leading cause of nosocomial infections worldwide and in the KSA. Objectives: The present study aimed to recognize the genes encoding Carbapenem resistance in two different non-fermentative, Gram-negative, non-fastidious pathogens, such as P. aeruginosa and A. baumannii strains isolated from a tertiary care hospital in Riyadh, Saudi Arabia. Materials/Methods: A total of 115 clinical isolates (80 P. aeruginosa and 35 A. baumannii) were obtained from different body sources at the clinical microbiology laboratory at King Khalid University Hospital, Riyadh, Saudi Arabia, from June to December 2017. The identification and antibiotic susceptibility testing were made for all the isolates using conventional (E-test) and the automated Vitek®2 system. The antibiotic susceptibility profiles of the isolates were determined as recommended by the Clinical and Laboratory Standards Institute (CLSI 2014). Polymerase Chain Reaction (PCR) was carried out to detect 13 Carbapenemase genes (OXA-23, OXA-24, OXA-40, OXA-51, OXA-10, OXA-48, OXA-1, VIM, IMP, GIM, NDM, KPC, ISAba-1) with a total of 50 ng DNA template added to the 25μl reaction mixture. Sanger sequencing was carried out using BigDye® Terminator v3.1 Cycle Sequencing kit (in 20 μl reaction mixture) to confirm the amplification of the target sequence. Results: A total of 80 isolates of P. aeruginosa were tested for the presence of Carbapenemase genes by PCR amplification method. It was found that the most prevalent genes were OXA-23 (55%) followed by bla_VIM (46%). The OXA-1 and bla_GIM genes were present in 22% and 15% of the isolates, respectively. A. baumannii isolates, tested for the presence of Carbapenem-resistant genes, also showed a prevalence of OXA-23 gene with an occurrence of 85.7%. ISAba-1 insertion sequence was found in 27 isolates. Conclusion: The rates of carbapenem-resistant isolates conferring multiple resistance genes are worrisome, leaving the clinicians with limited treatment options with antimicrobial drugs. Therefore, proper use for infection control procedures and revision of the treatment and management strategies is undoubtedly required to reduce the spread of resistance genes in these pathogens.