Bacteriostatic and bactericidal actions of boric acid against bacteria and fungi commonly found in urine

Abstract
 Boric acid has been used for  over 20 years to preserve urine while in transit fer bacteriological examination.
It has been suggested that it may be toxic for some urinary pathogens. To investigate this several strains of
bacteria and fungi commonly found in urine were exposed to different concentrations. of boric acid in
nutritnt broth. Viable counts were made at the outest and nt intervals for up to 24 hours at room temperature todetect bacteriostatic and bactericidal effect at the concentration between 10 and 20 g/l boric acid was bacteriostatic or fungi static for very nearly all the common urinary pathogens. At 10 g/l boric acid acid was weakly bactericidal for Some strians  of Acinetobacter calcoaceticus and Pseudomonas aeruginosa though higher concentrations were bacteriostatic only Group B streptococel varied in their response to boric acid but for most of them 10 to 20 g/l was satisfactorily bacteriostatic. It is concluded that boric acid is rarly toxic and when it is the effect is usually sufficiently delayed to be of only theoretical importance In 1969 Porter and Brodie described the use of boric acid at a concentration of 18 g/l to preserve urine while in transit for bacteriological examination. Although urine is a culture medium, they showed that when boric acid was added the number of any bacteria presented did not chnge significantly for up to 48 hours at room temperature and other cellular elements remained substantially intact.
 They claimed this effective bacteriostasis allowed the numericla criteria for the labooatory diagnosis of urinary tract infection (UTI) to be applied despite delay in performing the examination. This cheap and simple way to increase accuracy in the diagnosis of bacteriauria and pyuria has not been widely adopted.