{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,12]],"date-time":"2026-05-12T06:16:51Z","timestamp":1778566611314,"version":"3.51.4"},"reference-count":34,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,5,12]],"date-time":"2026-05-12T00:00:00Z","timestamp":1778544000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Cell. Infect. Microbiol."],"abstract":"\n Objectives<\/jats:title>\n \n To investigate the\n in vitro<\/jats:italic>\n susceptibility of recent clinical Enterobacterales and\n Pseudomonas aeruginosa<\/jats:italic>\n isolates collected in the Arabian Gulf region to ceftolozane\/tazobactam, imipenem\/relebactam, and comparator antimicrobial agents.\n <\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n From 2020 to 2024, two clinical laboratories in Kuwait and one each in Qatar, the United Arab Emirates, and Oman (participated in 2022\u20132024 only) collected up to 250 consecutive Gram-negative isolates per year from patients with bloodstream, intra-abdominal, lower respiratory tract, and urinary tract infections. MICs were determined by CLSI broth microdilution and interpreted with 2025 EUCAST breakpoints. Most imipenem, imipenem\/relebactam, and ceftolozane\/tazobactam non-susceptible isolates were interrogated for their acquired \u03b2-lactamase content.<\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n Ceftolozane\/tazobactam was active against 85.6% of the Enterobacterales (\n n<\/jats:italic>\n = 3,603), including 92.0% of ESBL-positive, non-CRE (non-carbapenem-resistant Enterobacterales) phenotype\n Escherichia coli<\/jats:italic>\n and 91.6% of ESBL-positive, non-CRE phenotype\n Klebsiella pneumoniae<\/jats:italic>\n , but was poorly active against MDR (multiple-drug resistant) isolates (21.6% susceptible). In total, 90.6% of non-\n Morganellaceae<\/jats:italic>\n Enterobacterales (\n n<\/jats:italic>\n \u00a0=\u00a03,421) were imipenem\/relebactam-susceptible, including 95.6% of the\n E. coli<\/jats:italic>\n and 80.7% of the\n K. pneumoniae<\/jats:italic>\n .\n Pseudomonas aeruginosa<\/jats:italic>\n isolates (\n n<\/jats:italic>\n = 1,347) were highly susceptible to both ceftolozane\/tazobactam and imipenem\/relebactam, with 91.2% and 89.0% inhibited, respectively. Both ceftolozane\/tazobactam and imipenem\/relebactam retained activity against \u226570% of cefepime-resistant, ceftazidime-resistant, and piperacillin\/tazobactam-resistant\n P. aeruginosa<\/jats:italic>\n . Ceftolozane\/tazobactam inhibited the greatest percentage of meropenem-resistant\n P. aeruginosa<\/jats:italic>\n (66.9%) among comparator \u03b2-lactam antimicrobials. Molecular characterization showed that the majority of both the imipenem\/relebactam- and ceftolozane\/tazobactam-resistant Enterobacterales harbored the NDM metallo-\u03b2-lactamase (MBL). Most of the imipenem\/relebactam-resistant\n P. aeruginosa<\/jats:italic>\n characterized did not possess acquired \u03b2-lactamases, while the majority of those resistant to ceftolozane\/tazobactam carried a variety of acquired enzymes, including MBLs (IMP, VIM, NDM) and ESBLs (VEB, GES).\n <\/jats:p>\n <\/jats:sec>\n \n Conclusion<\/jats:title>\n \n Recent clinical isolates of Enterobacterales collected in the Arabian Gulf region were highly susceptible to imipenem\/relebactam, while both imipenem\/relebactam and ceftolozane\/tazobactam exhibited excellent activity against\n P. aeruginosa.<\/jats:italic>\n However, the incidence of MBLs in the region remains a significant concern for future therapeutic strategies.\n <\/jats:p>\n <\/jats:sec>","DOI":"10.3389\/fcimb.2026.1827575","type":"journal-article","created":{"date-parts":[[2026,5,12]],"date-time":"2026-05-12T05:44:10Z","timestamp":1778564650000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Antimicrobial activity of ceftolozane\/tazobactam, imipenem\/relebactam, and comparators against Gram-negative pathogens collected in Arabian Gulf countries: SMART 2020\u20132024"],"prefix":"10.3389","volume":"16","author":[{"given":"Mark G.","family":"Wise","sequence":"first","affiliation":[{"name":"IHMA","place":["Schaumburg, IL, United States"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Irina","family":"Alekseeva","sequence":"additional","affiliation":[{"name":"MSD","place":["Dubai, United Arab Emirates"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Fakhar","family":"Siddiqui","sequence":"additional","affiliation":[{"name":"Merck & Co., Inc.","place":["Rahway, NJ, United States"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Katherine","family":"Young","sequence":"additional","affiliation":[{"name":"Merck & Co., Inc.","place":["Rahway, NJ, United States"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mary R.","family":"Motyl","sequence":"additional","affiliation":[{"name":"Merck & Co., Inc.","place":["Rahway, NJ, United States"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Daniel F.","family":"Sahm","sequence":"additional","affiliation":[{"name":"IHMA","place":["Schaumburg, IL, United States"]}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1965","published-online":{"date-parts":[[2026,5,12]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"529","DOI":"10.1007\/s44197-024-00191-y","article-title":"Antimicrobial resistance profiles of pseudomonas aeruginosa in the arabian gulf region over a 12-year period (2010-2021)","volume":"14","author":"Alatoom","year":"2024","journal-title":"J. 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