Ceftolozane / tazobactam (Zerbaxa®) is recommended as an option for restricted use within NHS Wales for the treatment of the following infections in adults: complicated intra-abdominal infections; acute pyelonephritis; and complicated urinary tract infections. Ceftolozane/tazobactam (Zerbaxa®) is recommended only following non responsive first line therapy due to resistance, i.e. where susceptibility has been confirmed and ceftolozane/tazobactam (Zerbaxa®) is considered the most clinically appropriate option following Consultant Microbiologist advice. Ceftolozane/tazobactam (Zerbaxa®) is not recommended for use within NHS Wales outside of this subgroup of patients. Consideration should be given to official guidance on the appropriate use of antibacterial agents.