Urinary Tract Infections (UTIs)

1. Urinary Tract Infections (UTIs) Microbiological Investigation

2. What are UTIs? • A significant bacteriuria in the presence of symptoms • Bacteria most often of faecal origin • Common causes of acute UTIs: • 50-70% = E. coli strains • 5-15% = Klebsiella pneumoniae • 5-15% = Enterobacteriaceae or enterococci

3. Genito-Urinary tract

4. Presentation of UTIs • Urethritis • The inflammation and infection is limited to the urethra • It is usually a sexually transmitted disease. • Present in men and women • Cystitis • Irritation of the lower urinary tract mucosa (i.e. bladder) • Dysuria (painful urination) • Urgency & frequency but small • Suprapubic tenderness • Pyuria • Haemorrhagic cystitis • Large quantities of visible blood in the urine • Caused by an infection (bacterial or viral) • Irritation when voiding • Pyelonephritis • Kidney infection from lower UTI infection • Complications – sepsis, septic shock and death

5. Epidemiology • Second only to respiratory infections (8 million visits to doctors for UTI per year [USA]) • ~2% incidence in preschool children 2 - 10 times more common in females • ~5% of school-aged females but rare in school-aged males • Large majority of adult cases are females - 30:1 • Forty percent of all females have at least one episode of a UTI at some time in their lives.

6. Epidemiology (2) • Women generally don't have many problems with UTI's until they become sexually active. • Postmenopausal: • bladder or uterine prolapse • loss of estrogen that causes a change in the vaginal flora • loss of lactobacilli in the vaginal flora which results in periurethral colonisation • Males experience a rapid increase in the incidence UTI's sometime in their 50’s - benign prostatic hypertrophy.

7. Predisposing factors • Sexual activity in females (75–90%) • Abnormality of the UT that obstructs or slows the flow of urine (i.e. kidney stone) • Elderly males: prostatic hypertrophy • Pregnancy • Catheterisation • Surgery, e.g. prostatectomy • Diabetes mellitus

8. Predisposing factors (2) • Immunosuppressed patients • Congenital abnormalities in infants that sometimes require surgery, e.g. vesico-uretic reflux • Women who use the diaphragm and spermicides • Patients with a neurogenic bladder or bladder diverticulum

9. Human kidney • Infection due to ascent from the lower urinary tract = pyelonephritis • Factor leading to retrograde flow of the urine to the kidney/pyelonephritis: • Cystitis due to a strain of E coli (mannose resistant pili bind epithelial/RBC) • Internalisation of E coli in the proximal tubular epithelial cells • Reflux of urine to the kidney - incomplete development of ureterovesical valves. • Physiological malfunctions – e.g. poor emptying of the bladder • Urethral catheters – bacteria conduit • Urinary tract stones - a place in which bacteria can escape antibiotics and cause further infections. Bacteria can cause stone formation.

10. Human kidney (2) • Kidney damage from: • the pathogen producing polysaccharide, which inhibits phagocytosis • alpha haemolysin and cytotoxic necrotising factor 1, causes tissue damage directly • endotoxin that contributes to inflammation

11. Types of UTI • Non- sexually transmitted! • Cystitis: inflammation of bladder wall; accompanied by dysuria and frequency • Cystitis is much the commonest, discomforting but not serious • Upper tract infections, e.g. pyelonephritis, are much more serious • Accompanied by fever and risk of complications

12. Community -acquired Escherichia coli Proteus mirabilis Klebsiella pneumoniae Enterococcus faecalis Staphylococcus species Hospital –acquired Pseudomonas aeruginosa Candida albicans AND (community acquired)Mycobacterium tuberculosis (renal TB – will be a ‘sterile pyuria’ Causative agents: mainly faecal bacteria

13. Investigation: the specimen • Mid-stream urine (MSU) is the specimen of choice • Suprapubic urine • Catheter urine • In all cases, urine must be examined immediately or stored at 4oC • Contamination of urine is a big problem!! • Should also determine the site of infection

14. Diagnosis • Urine culture yielding greater than 100,000 colony-forming units (105 CFU) per ml = significant bacteriuria. • However, 30% or more of symptomatic women have CFU counts below this level • Therefore, urine cultures are no longer advocated – pyuria (slide/dipstick) • Leukocyte esterase test - sensitivity of 75-90% pyuria associated UTI • Dipstick test for nitrite a surrogate marker for bacteriuria - not all uropathogens reduce nitrates to nitrite • Gram stains of urine can be used to detect bacteriuria - time-consuming and has low sensitivity

15. Standard procedures • Investigation of UTI involves the detection of bacteriuria together with evidence of an inflammatory response • Microscopy for pyuria and haematuria (can also reveal other structures, e.g. crystals, other cells, casts) • Culture for detection of bacteria • Sensitivity testing to advise on antibiotic treatment

16. Microscopy • Not always performed as it is time consuming • The finding of a rise in WBCs (pyuria) should be linked to a bacteriuria • May also see RBCs (haematuria); this is potentially an important finding • Microtitre plate and an inverted microscope enables many urines to be simply screened

17. White cells in urine • In normal state, there is a continuous secretion of WBCs into urine • In a UTI caused by bacteria, neutrophils may be secreted in large numbers • Labs may report >200/μl (>200 x 103/ml) and will suggest this as significant pyuria • Lower numbers: < 103/ml are regarded as not significant

18. Automation • Looking for particles suspended in a fluid • In the same way platelets and white cells can be automatically estimated in blood, so, too, can urine be analysed for its cellular content • Faster, less labour intensive and reliable • For example, flow cytometry

19. Culture: procedure • Cystitis is usually caused by a single species of bacterium present at >105/ml • Standard loopful of urine is streaked onto a selective medium, e.g. CLED, CHROMagar • Typically 1μl • Incubate overnight and count the colonies • If a genuine UTI, should see >100 colonies; this = >100 bacteria/μl or >105/ml

20. Culture: interpretation • >105/ml of a single species strongly suggests a UTI • 104-105/ml of a single species is equivocal – needs repeat specimen for testing • <104/ml is regarded as no significant growth • >1 species in any numbers suggests contamination • Catheter and suprapubic urines should be interpreted differently

21. Sensitivity testing • Clinical isolates are tested against antibiotics that a) are filtered by kidneys b) are usually effective against common agents • Since UTIs are common, drugs should be cheap! • Typical course of treatment: 5-7 days orally, resulting in sterile urine • Nitrofurantoin, nalidixic acid, trimethoprim, gentamicin, ampicillin, cephalosporins

22. Sensitivity testing (2) • Nitrofurantoin - rapid reduction of nitrofurantoin inside the bacterial cell = bacterial DNA damage • Nalidixic acid - a synthetic quinolone antibiotic that inhibits the topoisomerase II ligase leading to DNA fragmentation • Trimethoprim - dihydrofolate reductase inhibitor (inhibits thymadine production) • Gentamicin - inhibits 30S ribosomal subunit • Ampicillin - cell wall synthesis • Cephalosporins - cell wall synthesis

23. Antibiotic sensitivities

24. Therapy and Prevention • Clinical manifestations determine the initial step in therapy: • Afebrile UTI patients = outpatient • UTI patients experiencing high fever = hospitalised • General guidelines • Cystitis and/or urethritis treated for three days with norfloxacin or ciprofloxacin. • Pyelonephritis is more difficult to cure, can reoccur (i.e., treatment failure or reinfection) • Three day therapy is inappropriate • Intravenous antibiotics until fever breaks -> oral antibiotic for 14 days. • Culturing as a follow-up to insure treatment success. • Longer course for pregnant/diabetic women

25. Therapy and Prevention (2) • If the patient has urinary tract infections urge them to: • Maintain a high fluid intake • Drink cranberry juice (tannins) • Empty their bladder as soon as they feel the urge • Take medications prescribed by the doctor exactly as instructed

26. Therapy and Prevention (3) • 12 million urine analyses • Cases caused by E. coli resistant to ciprofloxacin grew five-fold, from 3% to 17.1% of cases. • E. coli resistant to trimethoprim-sulfame-thoxazole - 17.9% to 24.2% • The two of the most commonly prescribed antibiotics used to treat UTIs. • When they are not effective, doctors must turn to more toxic drugs, and the more those drugs are used, the less effective they in turn become.

27. Therapy and Prevention (4)