Letters to the Editor
To the Editors:
An 11-year-old boy was referred to our pediatric outpatient clinic with a complaint of foul smelling urine. The mother said that she had noticed the smell first when the child was 5 years. She said he had always had a good intake of water and did not have any other odd smells in sweat or elsewhere. He was not on any regular medications. He ate the same normal diet as the rest of the family. He had no difficulty or discomfort passing urine. Examination was unremarkable. He weighed 48.1 Kg. Clinic staff noted that the urine had an odd pungent ammoniacal odor. Full blood count, urea, electrolytes and glucose were normal.
A urine sample sent for chemistry has shown prominent lactate and benzoate peaks suggestive of bacterial contamination or infection.
The urine culture grew Aerococcus urinae. This unusual isolate prompted us to find the letter published recently in this journal describing an almost identical case.1 We were able to isolate A. urinae repeatedly.
We went on to treat with oral penicillin, which resulted in elimination of the smell within 3 days, and the culture was subsequently negative.
We think there are a number of lessons to be learned from this case that make it worth reporting.
First, the initial publication and the ease of literature searching meant we were able to make a connection with the previous case and to speculate that there may be other similar cases elsewhere.
Second, we found that it required an extended incubation of around 48 hours to isolate the organism. Gram-positive cocci were seen consistently in the samples before culture, but an initial sample was reported as negative after 24-hour incubation of the culture plates.
Third, identification of the A. urinae is difficult on conventional methods but easy using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.2 This new technology for bacterial identification has been implemented in some diagnostic laboratories in recent years. The availability of matrix-assisted laser desorption/ionization time-of-flight may explain why the association with foul smell has only recently come to light. Slow growing cocci in urine that were not identified as a recognized pathogen may have been dismissed as contaminants in many previous cases.
Fourth, this case illustrates the difficulty in interpreting antibiotic susceptibility results on unusual organisms. We use European Committee on Antimicrobial Susceptibility Testing criteria,3 which do not specifically address Aerococcus. They do give pharmacokinetic-based criteria but say there is “insufficient evidence” to interpret the trimethoprim result. This was our rational for choosing penicillin, which we were confident was active with a minimum inhibitory concentration of 0.016 μg/mL.
Fifth, we think that persisting bacteriuria without evidence of inflammation is unusual and out of line with our understanding of urinary tract physiology. We wonder what the explanation is for this conundrum.
Alan Patrick Gibb, FRCPath
Department of Laboratory Medicine
Baskaran Sivaraman, FRCPCH
Saint John’s Hospital
1. de Vries TW, Brandenburg AH. Foul smelling urine in a 7-year-old boy caused by Aerococcus urinae. Pediatr Infect Dis J. 2012;31:1316–1317
2. Schulthess B, Brodner K, Bloemberg GV, et al. Identification of Gram-positive cocci by use of matrix-assisted laser desorption ionization-time of flight mass spectrometry: comparison of different preparation methods and implementation of a practical algorithm for routine diagnostics. J Clin Microbiol. 2013;51:1834–1840