Urinary Tract Infections: Role of the Clinical Microbiology Laboratory Mark Smyth John E. Moore Colin E. Goldsmith rinary tract infections Urinary tract infections (UTIs) are common infectious diseases in all (UTIs) are common both ages of humans, from the neonate through to the elderly, with certain in the community and ages having an increasesed occurrence of specific bacterial etiolo- hospital and involve the gies. Clinical microbiology forms an important cornerstone in the sci- Uinteraction between clinician and entific workup of (a) detecting a causal agent responsible for the UTI, clinical microbiologist. To many, (b) phenotypic and increasingly genotypic identification of causal the role of the clinical microbiolo- agents of UTIs, and (c) characterization of identified agents of UTIs, gy laboratory remains a “black including antibiotic susceptibility testing and virulence testing. For box,” which generates microbiol- most clinicians, the workings of clinical microbiology remain a “black ogy laboratory reports that may box;” hence, the main objective of this review is to present scientif- aid in patient management. ic insight into how clinical microbiology handles the laboratory Several authoritative reviews on the management of UTIs have workup of urine specimens, and the pearls and pitfalls of urine micro- been published recently (Dulczak biology that may cause delay and frustration in the feedback of & Kirk, 2005). Therefore, the aim microbiology data to the patient’s clinician. of this review is to discuss the role of the microbiology laboratory to those clinical disciplines inter- nificant proportion of the work- lower and upper urinary tracts. ested in learning about updates load in most clinical microbiolo- Infections can be further classi- in diagnostic methodologies in gy laboratories. A UTI is normal- fied as uncomplicated and com- microbiologic urology. ly diagnosed based on medical plicated depending on the extent UTIs are among the most history and a physical examina- and duration of the infection. prevalent bacterial infections tion. Confirmation of a urinary In an uncomplicated UTI, the affecting both genders and all age tract infection requires a labora- most common site of infection is groups. They also represent a sig- tory examination of a urinary usually the urinary bladder. The sample, using a combination of most common route of access for microscopy and bacterial cul- pathogenic micro-organisms is Mark Smyth, MSc, BSc, is a ture. Bacterial isolates will then an ascending infection from Biomedical Scientist, Northern Ireland undergo antimicrobial sensitivity neighboring sites, in particular, Public Health Laboratory, Belfast City testing to provide the clinician from the urethra and perianal Hospital, Northern Ireland, United with antibiotic choices, if regions. A less-common route is Kingdom. required for the patient. spread from the cardiovascular system, which is typical in infec- John E. Moore, PhD, BSc, is a Overview of Urinary Tract tions caused by Salmonella spp. Clinical Scientist, Northern Ireland Infections Public Health Laboratory, Belfast City and Mycobacterium tuberculosis Hospital, Northern Ireland, United The urinary tract above the (Hawkey & Lewis, 2003). Kingdom. level of the distal urethra is nor- Cystitis is the term used to mally sterile but infection can describe uncomplicated lower Colin E. Goldsmith, MB, BCh, BAO, occur at any site from the kidney urinary tract infection of the BSc, MRCPath, is a Consultant in to the urethra. Urinary tract bladder. Signs and symptoms Medical Microbilogy, Northern Ireland infections may involve just the include a combination of factors Public Health Laboratory, Belfast City lower urinary tract, or the infec- including dysuria, urgency, fre- Hospital, Northern Ireland, United tion may encompass both the quency, hematuria, and suprapu- Kingdom. 198 UROLOGIC NURSING / June 2006 / Volume 26 Number 3 bic pain. Upper urinary tract infection is commonly described Once adulthood is reached, the prevalence of as pyelonephritis and is often bacteriuria steadily increases in the female associated with the symptoms of cystitis combined with flank population. pain and abdominal tenderness. Cystitis and pyelonephritis often present as acute diseases, but recurrent or chronic infections abnormalities. Patients with of the female population will may also occur (Jawetz, Melnick, renal abnormalities are more experience a symptomatic uri- & Adelberg, 1995). likely to suffer from true mixed nary tract infection at some time The risk of suffering from a infections. Frequently, the infect- in their life, with a prevalence of UTI is dependent on age, underly- ing bacteria may be antibiotic- between 1% to 3% among non- ing renal impairments, and most resistant due to repeated antimi- pregnant woman. Sexual activity importantly gender (Hawkey & crobial therapy (Murray, 1998). and use of spermicides also Lewis, 2003). Bacteriuria is signif- With nosocomial or hospital- increase the risk for UTIs in icantly more prevalent in the acquired infections, the actual young women (Sanford, 1975). In female population, and it increas- hospital environment is an adult men, the prevalence rates es with age in both sexes until the important determinant of the are low at around 0.1% until the gender ratio of infection becomes nature of the infecting organisms. later years in life, when it steadi- nearly equal in the elderly. Proteus, Klebsiella, Enterobacter, ly increases. Bacteriuria among Pseudomonas, staphylococci, adult men, as in childhood, is Epidemiology of Infecting and enterococci are more often frequently associated with uri- Organisms isolated from inpatients, as com- nary anatomic abnormalities There are differences between pared to the preponderance of E. (Kaye, 1972). the infecting bacterial species in a coli in an outpatient population In the elderly patient, the patient suffering from an initial (Turck & Stamm, 1970). female/male UTI ratio becomes acute episode of urinary tract The incidence of UTI spans less significant. For patients of infection as compared to those all age groups starting with both genders over the age of 65, with frequent recurring infec- neonates. In infants up to 6 the prevalence increases substan- tions. Escherichia coli are by far months, the infection rate is tially; at least 10% of men and the most frequent infecting bacte- about 2 cases per 1,000 live 20% of women over 65 will suf- ria in acute UTIs. E. coli causes births and is more prevalent in fer from a UTI (Kaye, 1980). 80% to 90% of acute uncompli- boys (Boineau & Lewy, 1975). There are several factors that cated bacterial UTIs in young During the preschool years, the increase the prevalence of UTIs women (Hawkey & Lewis, 2003). incidence of UTI becomes more in the elderly. This includes Other enteric bacteria and prevalent in females. In a study obstructive uropathy from the Staphylococcus saprophyticus of this age group, the prevalence prostate and the weakening of cause most of the other culture- was 4.5% for girls and less than the bactericidal activity of prosta- positive infections in this patient 0.5% for boys. The infections tic secretions in men. In women, group. Some young women with that occur in preschool boys are the increases can be partially acute dysuria, suggesting cystitis, often associated with congenital attributed to soiling of the per- have negative urine cultures for renal abnormalities (Boineau & ineum from fecal incontinence bacteria. In these patients, selec- Lewy, 1975; Randolph & and poor bladder emptying due tive cultures for more difficult-to- Greenield, 1964). to prolapse (Romano & Kaye, culture organisms, such as In a study of children of 1981). Catheterization also dra- Neisseria gonorrhoea and school age, bacteriuria was com- matically increases the risks of Chlamydia trachomatis, and mon, frequently asymptomatic, developing an upper UTI in the evaluation for herpes simplex and commonly recurred in the elderly. Even with optimal care viral infection should be investi- female population. The preva- and closed drainage systems, gated (Jawetz et al., 1995). lence for girls was reported as 50% of catheterized patients will In recurrent or chronic UTIs, 1.2%, with 5% experiencing a become infected after 4 to 5 days, the frequency of infection caused UTI during their time at school. 75% after 7 to 9 days, and 100% by Proteus spp., Pseudomonas Among boys, bacteriuria was after 2 weeks (Hawkey & Lewis, spp., Klebsiella spp., Enterobacter reported as being very low, at 2003). spp., and by enterococci and approximately 0.03% in the staphylococci is significant. group studied (Kunin, 1970; Role of the Clinical Chronic and recurrent UTIs are 1976). Laboratory generally due to the presence of Once adulthood is reached, The aim of clinical laborato- structural abnormalities such as the prevalence of bacteriuria ry diagnostic procedures should obstructive uropathy, neurogenic steadily increases in the female be the detection of the abnormal bladder, and congenital renal population. At least 10% to 20% presence of bacteria within the UROLOGIC NURSING / June 2006 / Volume 26 Number 3 199 urinary tract together with evi- from around the urethra. The Urine Microscopy dence of inflammation. The mid-stream section of the urine Microscopy can be a useful detection and identification of should then be collected. tool in the diagnosis of bacteri- bacteria is normally carried out Reliability of a positive result uria and is often the first step in using routine culture