Bacteriuria In Various Populations regardless of the number of organisms found, providing that the specimen is not contaminated prior to culture. Bacteriologic Findings. The species of bacteria most likely to be recovered in individuals with bacteriuria depends, for the most part, upon the previous history of infection, receipt of antimicrobial therapy, hospitalization, and instrumentation of the urinary tract. In this respect, the bacterial flora found in individuals with asymptomatic bacteriuria is no different from that in cases of clinically obvious pyelonephritis. Enterobacteriaceae are by far the most common organisms identified. E. coli generally accounts for more than 80 percent of all species recovered in so-called uncomplicated cases, whereas Proteus, Klebsiella, Enterobacter, Pseudomonas aerugino so, enterococci, and Staphylococcus aureus are more likely to be found in patients who have had previous infection or instrumentation (the so-called complicated group).
Occasionally, organisms such as Serratia marcescens, Mima-Herellea, Candida albicans, and even Cryptococcus neo-forms may be significant and produce disease in diabetics and in patients treated with corticosteroids and immunosuppressive agents. Dipthyroids, Staphylococcus epidermidis, and microaerophilic streptococci are highly suspect as contaminants. They usually will not be isolated on repeated culture. They should not, however, be dismissed if repeatedly recovered under optimal conditions of collection. Despite the abundance of anaerobic flora in the gut, they are actually rare in urinary infections, presumably owing to the poor growth of these organisms in urine. Microscopic Methods. Rapid diagnostic meth-ods are available by either preparation of a Gram stain of unedited urine and examination with’ an oil immersion lens, or by the study of the centrifuged urinary sediment for bacteria, employ-ing the high dry objective under reduced light with or without the addition of methylene blue.
Bacteriuria In Various Populations the Gram stain has been the most widely used of these methods and correlates about 80 to 90 percent with quantitative culture. Examination of the unstained sediment as prepared for the search for formed elements in the urine is very helpful. It is much less time consuming than the preparation of a stained slide and can be done in conjunction with the routine examination for formed elements. This method lends itself particularly well in office practice to assessing the presence of a urinary tract infection. The criterion for a positive sentiment is the presence of many (preferably more than 20) obvious bacteria. The presence of marked pyuria can mask bacteria in the sediment. Fresh urine is required because crystals will also obscure the bacteria. If crystals do form, the urine should be warmed until they dissolve. Ten or more leukocytes per high-powered field in the centrifuged specimen is usually accepted as representing pyuria.
When inflammation of the bladder mucosa is intense, there may bestow erythrocytes in the urine, and gross hermits sometimes occur. Proteinuria is not common in urinary infections. Epidemiology and Natural History. Extensive epidemiologic studies have provided information of the frequency of bacteriuria in various populations. Bacteriuria in the newborn period has been difficult to define because of problems inherent in the collection, but the information is being obtained with the widespread use of the bladder puncture methodInfection of the urinary tract in this age group appears to be part of a generalized, life-threatening gram-negative sepsis and is more common in boys than girls. Symptomatic urinary infections, particularly among girls, are prominent in the preschool years and are frequently associated with important obstructive or neurogenic lesions.
The urologic investigation is extremely valuable in this age group. It is mandatory in males of any age because of the high frequency of important structural abnormalities found (valves, malformations, obstructive and neurogenic lesions). The prevalence of bacteriuria among schoolgirls is 1.2 percent; it is only 0.03 percent in boys of the same’ age. The incidence rate in girls is 0.3 percent per year; it is linear with time throughout the school years and is unaffected by menarche. The cumulative frequency or urinary infection in girls occur-ring at one time or another during the school years exceeds 5 percent. Bacteriuria in schoolgirls is independent of socioeconomic status and race and is not increased in diabetic girls. The prevalence of bacteriuria rises with age and is increased in lower socioeconomic groups, probably because of limited antimicrobial therapy delivered to this population. Urinary infection is common after marriage.
The “honeymoon cystitis” syndrome may be due to either infection or local irritation, and these should be clearly differentiated by culture. Bacteriuria in pregnancy varies from 2 to 6 percent, depending upon age, parity, and socioeconomic groups. Early detection and treatment of bacteriuria in this age group will prevent the emergence of symptomatic infection. Elderly women may have frequencies of bacteriuria as high as 10 percent; this rate may rise even higher in hospitalized patients, particularly diabetics. Bacteriuria in the male often to appear in the “prostate” years and is often initiated by instrumentation.
Role of Instrumentation. Persistent bacteriuria follows single catheterizations at a frequency of 1 to 2 percent and with open indwelling catheter drainage exceeds 90 percent within three to four days. This may lead to life-threatening pyelonephritis and gram-negative sepsis. Fortunately, it is partially avoidable by (1) careful preselection of criteria for catheterization, and (2) use of aseptic closed drainage or antimicrobial bladder rinse during prolonged catheterization. The catheter should be removed as soon as it is no longer needed.