Garai et al.; A novel mechanism of ceftolozane-tazobactam resistance in Pseudomonas aeruginosa mediated by L2 β-lactamase; (Raw data files); 2026

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The files contain raw experimental data that are part of the manuscript prepared by Garai et al (2026). These data indicate that L2 β-lactamase (bla_L2 gene) contributes to resistance to ceftolozane-tazobactam (C/T) in P. aeruginosa. A P. aeruginosa clinical isolate (PA-NM-086) collected from the bone biopsy of a patient with multiple comorbidities and acute sacral osteomyelitis was found to be highly resistant to C/T with a minimum inhibitory concentration (MIC) of >256/4 µg/mL). This isolate was genetically distinct from another isolate (PA-NM-055) obtained from the patient during a prior admission, which was C/T sensitive. The C/T-resistant isolate PA-NM-086 contained five copies of a genetic element that contained the L2 β-lactamase gene (bla_L2) and a truncated ampR _L2 transcriptional regulator gene, which were identical to those found in Stenotrophomonas maltophilia strains. This genetic element was absent in the C/T-sensitive isolate, PA-NM-055. Since bla_L2 has not been reported to mediate resistance to C/T, we assessed the effect of exogenous expression of this gene in P. aeruginosa lab strains PA14 and PAO1. Our results show that induction of bla_L2 expression in these distinct strains of P. aeruginosa increases their C/T MIC (MIC Raw data). Two other P. aeruginosa clinical isolates, PS2045 and PS2046, were found to have one and two copies, respectively, of the genetic element containing bla_L2 and truncated ampR_L2. Comparison of C/T MICs with other clinical isolates containing different copies of the bla_L2 gene indicated a correlation between copy number and resistance to multiple antibiotics, including C/T (MIC Raw data). Our gene expression analysis (RTqPCR Raw data) further showed that the truncated AmpR_L2 in P. aeruginosa does not regulate the expression of bla_L2 in response to the β-lactam antibiotic imipenem, unlike the full-length AmpR_L2 found in S. maltophilia. This was also validated by our finding that the disruption of the gene bla_L2 and not the truncated ampR_L2 in PS2045 led to a significant decrease in C/T MIC values (MIC Raw data). Thus, these data support our conclusion that C/T resistance in P. aeruginosa is mediated by L2 β-lactamase independently of its canonical regulator AmpR_L2.

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