Which of the following statements regarding pyelonephritis is correct -

• A. Relapse is defined as recurrent infection with the same strain usually occurring in less than two weeks of cessation of therapy
• B. Antiboby coated bacteria test does not help to distinguish upper and and lower urinary tract
• C. The incidence has been found to behigher in women with pregnancy toxaemia
• D. 10000 viable bacteria per ml in clean voided midstream urine is of significance