In Abrutyn and colleagues' straightforward cohort study [1], they concluded that "screening and treatment of asymptomatic bacteriuria in ambulatory elderly women to decrease mortality do not appear warranted."

That criterion began as a working hypothesis by Kass [2], who in 1956 postulated that all "significant" bacteria found in urine will grow freely and exponentially in bladder urine as a good culture medium incubated at 37 °C and thus will reach 10⁵ colony-forming units (CFU)/mL. This was uniformly true in his reference gold standard, a group of 25 patients with florid pyelonephritis, but other patients with 10⁵ CFU/mL were asymptomatic. Kass assumed that counts less than 10⁵ CFU/mL were from contaminants acquired in voiding. The latter assumption has never been proved and is not true.

If the exponential increase in bacterial counts in bladder urine is fully integrated [3], it becomes clear that only a few organisms can divide rapidly enough to fulfill Kass's criterion and that these are labeled as "commonly found." The accumulated data prove only that if rapid growth is required for "significance," then only bacteria that grow rapidly will be "significant." Since 1956, many investigators [3], including Kaye [4], reported that only a few strains can grow rapidly enough to meet this criterion in filter-sterilized urine. Many important pathogens grow too slowly or die in urine, and many streptococci also fail to grow in routine media on initial isolation. Many important reports of "asymptomatic bacteriuria" that were published before 1956 and were based on the use of more generalized culture media have been set aside by the 10⁵ convention [3, 5]. These pathogens are easily detected by microscopy, and subsequent treatment may be life-saving.

Thus, despite a good report, Abrutyn and colleagues' final conclusion is a "managed care" bureaucrat's dream, which may lead to a detrimental rationing of the diagnosis and treatment of bacteriuria among elderly patients.