MedicalResearch.com Interview with:
Thomas M. Hooton M.D.
Professor of Medicine and Vice Chair for VA Affairs,
University of Miami Miller School of Medicine
Associate Chief of Staff, Medical Service, Miami VA Healthcare System
Clinical Director, Division of Infectious Diseases
MedicalResearch.com: What are the main findings of the study?
Dr. Hooten: The main findings from this study are:
· Voided urine colony counts of E. coli as low as 101 to 102 cfu/mL are highly sensitive and specific for their presence in bladder urine in symptomatic women (growth of bacteria in bladder urine is the gold standard for the etiology of UTI). Moreover, even when E. coli is found along with other mixed flora in voided urine, it should not be considered a contaminant since it likely represents true bladder infection.
· On the other hand, enterococci and Group B streptococci, which are frequently isolated from voided urine, are rarely isolated from paired catheter specimens, suggesting that these organisms only rarely cause acute uncomplicated cystitis. In our study, E. coli frequently grew from the urines of these women and is the likely cause for UTI symptoms in such episodes.
· Organisms usually considered contaminants, such as lactobacilli, occasionally grow from catheter urines, but they are rarely found alone with pyuria, suggesting that these bacteria rarely cause acute uncomplicated cystitis.
· The etiology of a quarter of acute uncomplicated cystitis episodes is unknown. It is possible that some of these women have E. coli urethritis, which has been documented in some women with UTI symptoms, but we did not do further studies to evaluate this. It is possible also that enterococci and Group B streptococci may also cause urethritis, but there is no published evidence of this in young women with UTI symptoms.
· Although voided urine cultures growing mixed flora are common in women with acute cystitis, true polymicrobic cystitis, as determined by sampling bladder urine, appears to be rare in this population.
MedicalResearch.com: Were any of the findings unexpected?
Dr. Hooten: The strong predictive value of E. coli in voided urine at almost any colony count as an indicator of true bladder infection supports previous findings in young symptomatic women. The main surprise was the lack of a correlation with enterococci and Group B streptococci in paired voided urine and bladder urine specimens, even when they grew at high colony counts in voided urine. Certainly such findings need to be confirmed in other studies, but the findings were dramatic in this study.
We were also surprised that Klebsiella pneumoniae and Staphylococcus saprophyticus were both found only in high colony counts (in both voided and catheter urine specimens) and are not sure of the reasons for this. Perhaps E. coli is more virulent and can cause UTI symptoms to occur in lower quantities than these two uropathogens, although this is only speculative.
MedicalResearch.com: What should clinicians and patients take away from your report?
Dr. Hooten: These data reinforce the opinion of many that the voided urine culture for diagnosis of cystitis in healthy women has limited value. However, for the clinician who feels that a voided urine culture is warranted for the diagnosis of UTI in a symptomatic woman, it is important to know that:
· E. coli in voided urine even in very low counts or in mixed flora is predictive of bladder urine growth and, thus, the likely cause of the woman’s UTI symptoms – and should not be ignored by the clinician.
· Thus, in such women the laboratory should be asked to quantify Gram negative rods to low levels in voided urine specimens (most laboratories do not quantify to low levels unless asked to do so) in order to improve sensitivity of the culture.
· On the other hand, enterococci and Group B streptococci, when grown in voided urine in a woman with UTI symptoms, are not likely to be the cause of such symptoms. E. coli is the likely cause for symptoms in many of these women.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Dr. Hooten: Voided urine and catheter urine comparison studies should be performed in other types of patients with UTI, such as pregnant women (asymptomatic and symptomatic since both warrant treatment) and older women with symptoms of cystitis. Organisms such as enterococci or Group B streptococci are occasionally isolated from such women and are treated accordingly, and it would be useful to know whether they warrant treatment.