ESBL and Carbapenem Resistance Mechanisms

A 62-year-old man with chronic kidney disease stage 4 and indwelling urinary catheter for 3 weeks presents with fever (38.5°C), dysuria, and cloudy urine. Urine culture yields Klebsiella pneumoniae producing extended-spectrum beta-lactamase (ESBL). The organism is resistant to ceftriaxone but susceptible to carbapenems and colistin. Which of the following statements regarding this isolate is MOST accurate?

A 34-year-old woman with a history of recurrent urinary tract infections is found to have a urinary isolate of Escherichia coli that is resistant to ampicillin, amoxicillin-clavulanate, and cephalosporins, but remains susceptible to carbapenems and fluoroquinolones. The isolate produces a positive Extended-Spectrum Beta-Lactamase (ESBL) test. Which of the following mechanisms best explains the resistance pattern observed in this isolate?

A 42-year-old woman from Mumbai is admitted with severe pneumonia and sepsis. Sputum culture grows a gram-negative rod identified as *Klebsiella pneumoniae*. Antibiotic susceptibility testing shows resistance to all beta-lactams including carbapenems (meropenem MIC 16 µg/mL), but susceptibility to colistin and tigecycline. The organism produces a Hodge test-positive result. Which carbapenemase enzyme is most likely responsible for this resistance pattern in this Indian hospital setting?

A 52-year-old man with diabetes mellitus presents with fever, dysuria, and flank pain. Urine culture grows an ESBL-producing Escherichia coli. The organism is susceptible to cephalosporins on disk diffusion but resistant on ESBL confirmatory testing. What is the drug of choice for this upper urinary tract infection?

A 62-year-old male from Delhi with diabetes mellitus presents with fever and dysuria. Urine culture grows a gram-negative rod. The organism is resistant to ceftriaxone and cefotaxime but susceptible to carbapenems. The microbiology lab reports a positive ESBL phenotype. Which investigation is most appropriate to confirm the ESBL production mechanism?