A 26-year-old male patient complains of pain in the right knee, which is getting worse in the morning. Two weeks before, he consulted an urologist about prostatitis. Objectively: conjunctivitis is present. There is also periarticular edema of the knee joint, redness of the overlying skin. Rheumatoid factor was not detected. Until further diagnosis is specified, it would be reasonable to start treatment with the following antibiotic: