Re: Uncomplicated urinary tract infection in women
Dear Editor,
I maintain that MSU culture remains a useful and valid investigation for the diagnosis of infection. Sathiananthamoorthy et al [1] are quite rightly critical of hospital laboratories in the United Kingdom which use a threshold of ≥ 105 CFU/ml to confirm both uncomplicated and complicated UTI.
This threshold has been validated only for asymptomatic pregnant females. In symptomatic women lower counts and mixed growths may be clinically relevant. Infections caused by opportunistic or atypical organisms will be missed if culture is limited to a single selective culture medium.
In my laboratory, urine from symptomatic patients with pyuria had additional cultures on non-selective media incubated in an anaerobic atmosphere and in 5% CO2. Six clinically significant anaerobic infections were reported [2]. The study also showed that selective media can be inhibitory to common infecting organisms.
The request form accompanying a specimen should be considered a consultation document: the laboratory should respond to the clinical data provided. Clinicians should communicate with the microbiologist about complicated cases when additional cultures will be required. In particular, culture of a fresh MSU specimen free of inhibitory transport medium should be arranged with the laboratory wherever possible. Patients with chronic and recurrent infections are usually willing to visit the local laboratory to provide a fresh specimen. Moving microbiology services off-site to remote centralised laboratories may interfere with clinical liaison and are not in the best interest of patients.
If controlling cost is an issue, I suggest minimal processing of “routine specimens” which merely state “dip-stick positive” and those unsupported by clinical information. The latter might well be discarded.
2. Bannon, Hatem & Noone, Anaerobic infections of the urinary tract are they being missed? J Clin Pathol, 1998 Sep; 51(9): 709–710. doi: 10.1136/jcp.51.9.709
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Re: Uncomplicated urinary tract infection in women
Dear Editor,
I maintain that MSU culture remains a useful and valid investigation for the diagnosis of infection. Sathiananthamoorthy et al [1] are quite rightly critical of hospital laboratories in the United Kingdom which use a threshold of ≥ 105 CFU/ml to confirm both uncomplicated and complicated UTI.
This threshold has been validated only for asymptomatic pregnant females. In symptomatic women lower counts and mixed growths may be clinically relevant. Infections caused by opportunistic or atypical organisms will be missed if culture is limited to a single selective culture medium.
In my laboratory, urine from symptomatic patients with pyuria had additional cultures on non-selective media incubated in an anaerobic atmosphere and in 5% CO2. Six clinically significant anaerobic infections were reported [2]. The study also showed that selective media can be inhibitory to common infecting organisms.
The request form accompanying a specimen should be considered a consultation document: the laboratory should respond to the clinical data provided. Clinicians should communicate with the microbiologist about complicated cases when additional cultures will be required. In particular, culture of a fresh MSU specimen free of inhibitory transport medium should be arranged with the laboratory wherever possible. Patients with chronic and recurrent infections are usually willing to visit the local laboratory to provide a fresh specimen. Moving microbiology services off-site to remote centralised laboratories may interfere with clinical liaison and are not in the best interest of patients.
If controlling cost is an issue, I suggest minimal processing of “routine specimens” which merely state “dip-stick positive” and those unsupported by clinical information. The latter might well be discarded.
1. Sathiananthamoorthy et al, Reassessment of routine midstream culture in diagnosis of urinary tract infection. J Clin Microbiol, 2019. 57(3) https://jcm.asm.org/content/early/2018/12/10/JCM.01452-18
2. Bannon, Hatem & Noone, Anaerobic infections of the urinary tract are they being missed? J Clin Pathol, 1998 Sep; 51(9): 709–710. doi: 10.1136/jcp.51.9.709
Competing interests: No competing interests