Lecture 19: Urinary Tract Infections

(Urinary Tract Infections) Lecture 19 Urinary Tract Infections (UTI) · more common in females · majority of infections are acute (sudden) and uncomplicated eg. cystitis, urethritis · most common type of nosocomial infection ↳ due to catheters because bacteria can climb up them and form biofilms · severe infections with complications affect kidney function (pyelonephritis) Urine · Kidney: removes wastes from blood (filtration) · Valves control against backward flow of urine from bladder to ureters · urine is normally low pH (acidic), has some antimicrobial properties, and is normally sterile · flushing of urine: mechanism of physical defense · urine sedimentation test: analysis of cell content, osmolality, protein and glucose content, "casts" important for diagnosis of complicated infection ↳ centrifuges the urine, doesn't need to be as sterile · urine culture: sterile container, urine cannot touch skin, midstream sample Common Causes of UTI » outpatients » Inpatients · CNS · Other enteric bacteria · E. coli (80% ) · E. coli (40% ) · S. aureus · Gram + · Enterococci · Streptococcus Group B E. coli is #1 ! · Proteus mirabilis · Candida species Catheters and Bacteria (Biofilms form) Symptoms of UTI · Upper UTI (kidneys) · Lower UTI ↳ painful urination (dysuria) ↳ fever and some of same ↳ catheter infections usually asymptomatic ↳ may have lower back pain symptoms as lower UTI ↳ urgency and frequency of peeing ↳ cloudy urine due to WBC (pyuria) and bacteria (bacteriuria) Urethritis: infection of the urethra Asymptomatic UTI Ureteritis: infection of the ureters (bacteriuria) in absence of symptoms Cystitis: infection of the urinary bladder · presence of significant numbers of bacteria Pyelonephritis: infection of the kidney · can cause complications (scarring) in young ↳ may lead to sepsis Significant Bacteria · 100 x 10^6 cfu/mL midstream urine ↳ this many in order to be labelled a UTI ↳ must be held in bladder for 4+ hours · Exceptions: catheritized patients, infants, immunosuppressed, urine held in bladder under 4 hours, infection with S. saphrophyticus · "contaminated urine" has often several species growing (usually theres only one) children and pregnant women ↳ Kidney damage scarring UTI in Children · reflux found in 30-50% of asymptomatic children ↳ urine goes back up to the kidney instead of normal route (valve problem) ↳ corrected with surgery · high risk for renal scarring · very difficult to get "good specimens", especially from infants; often require supra-pubic aspiration for uncontaminated sample -- Organisms Common in UTI · E. coli: facultative G-bacillus, motile, maybe capsule ↳ antigens on surface of E. coli · Staphylococcus saphrophyticus - O: somatic - H: flagellar - K: capsular ↳ primary pathogen for UTI ↳ G+ cocci in clusters, coagulase negative ↳ infections in healthy young women - F: fimbrial ↳ adhesion: p-fimbriae attach to uroepithelial cells on inside of bladder ↳ usually susceptible to many antibiotics · other G-bacilli that live in the colon can also cause UTI, but less commonly unless it is an elderly or catheterized patient · Streptococcus agalactiae (Group B) ↳ G + cocci in chains ↳ beta-hemolytic on blood agar ↳ neonatal meningitis: Sepsis and respiratory failure for the infected neonate ↳ lives in intestine, easy travel to vagina, bad for pregnant women and babies · Enterococcus faecalis or faecium ↳ proper name is Streptococcus ↳ G+ elongated cocci, in short chains or pairs ↳ may produce alpha, beta, or no (gamma) hemolysis on BAP ↳ bile and salt tolerant, lives in intestine ↳ VRE (vancomycin resistant entero cocci) ↳ common in elderly people Specimens · collection and transportation to lab important due to quantitative nature of cultures · Midstream sample (MSU) in sterile container · urine sample best when in bladder for 4 hours · babies: bag urine often contaminated (bad sample) ↳ suprapubic aspiration recommended but rarely done · Catheterized patients: withdraw from tube with syringe · Urine esterase can be measured by dip-stick, positive means presence of WBC (infection) ↳ send urine for culture! ↳ esterase is an enzyme produced by neutrophils Congenital: infection during gestation (before birth) Perinatal or Neonatal Infections: Neonatal: infection up to 4 weeks after birth · Hepatitis B and C Perinatal: infection during labour and childbirth Perinatal or Neonatal Infections: · infection in first 4 weeks of life (no adaptive immune system) · usually acquire pathogens during birth (messy process) · Host Factors: immature immunity · breached skin barrier common during the trauma of birth · severity depends on the infectious agent and when it is acquired Neonatal Herpes · risk to infant: disseminated (spread throughout body) Herpes infection and encephalitis (inflammation of the brain) · Caused by HSV 1 or HSV 2 · HIV 1 and 2 · Varicella zoster virus · Herpes simplex · Group B Streptococci · E. coli and other G- · Listeria monocytogenes · Chlamydia trachomatis · Neisseria gonorrhoeae · Papillomavirus Streptococcus agalactiae (Group B) · leading cause of neonatal meningitis and sepsis E. coli and G- · early onset (2-7 days) or late onset (7-12 days) areas, rare in developed areas · very rapid progression of disease · major problem in underdeveloped ↳ early onset more common · infection at birth can lead to prolonged rupture of membranes ("water breaking" prognosis ↳ risk factors: prematurity (bad immune system) and meningitis and sepsis with poor membrane) · antibiotic resistance is an issue · late onset infection usually not acquired at birth, but in the hospital by mother/nurses/visitors · portal of entry: respiratory tract · Mortality due to meningitis is 50% Neonatal Gonorrhoeae and Chlamydia · Chlamydia: usually begins as an eye infection, progresses to pneumonia/meningitis/sepsis but takes about a month · GC infection: opthalmia neonatorum in newborns, infection can become obvious within a week and spread (development of sepsis) Congenital Infections · fetus most commonly infected in utero · often result of a primary infection of the mother during pregnancy, not seen with latent infection ↳ not as bad if mother has had it before · fetus may die, spontaneously abort, or survive with abnormalities · fetus cannot protect itself immunologically from infection · lack of symptoms in the mother (striking feature! ) Congenital CMV (cytomegalovirus) · mother infected with a primary infection during pregnancy · 40% of babies infected at birth, but effects may not become apparent until later in life (15 years) · If manifest at birth: ↳ severe developmental disabilities ↳ spasticity (stiff muscles) ↳ eye abnormalities ↳ hearing defects ↳ hepatosplenomegaly (liver and spleen are enlarged) ↳ thrombocytopenic purpura (decrease in platelets/don't work) ↳ anemia · no vaccine! Congenital Hepatitus B and C · the earlier in life the infection, the greater the chance to become chronic · chronic infection = increased risk of liver cancer · 70-90% of neonates with HBV become chronic · 10% chronic if infected between birth and 6 years · vaccinate newborns with Hep B and hepatitus immunoglobulin Congenital Rubella · fetus is susceptible when mother is in first trimester ↳ heart, eyes, brain, and ears formed · RNA virus, pathogenesis unknown · Fetal death common when infection in first month ↳ 26% abnormalities month 2 ↳ 18% abnormalities month 3 ↳ 7% abnormalities month 4 Congenital Toxoplasmosis · only 10-15% of infections are symptomatic in the fetus when infected during the first trimester, but these give SEVERE defects · clinical features of severe disease ↳ convulsions ↳ microcephaly (small head) ↳ chorioretinitis (inflammation of eye) ↳ hepatosplenomegaly (liver and spleen enlarged) ↳ jaundice ↳ hydrocephaly (water on brain causing pressure) ↳ mental development impairment ↳ defective vision Congenital HIV · reduction in vertical transmission in western world due to treatment of mothers before birth · elective caesarians, no breast feeding unless necessary ↳ underdeveloped countries breastfeed for 6 months (IgG antibodies) · "failure to thrive" → small and underdeveloped · perinatal transmission: transmitted to fetus during gestation, at delivery, or by breast feeding ↳ maternal plasma viral load most important factor in determining chance of transmission to fetus · Vitamin A deficiency in pregnancy increases risk for infection · maternal HIV is not associated with abnormalities, prematurity, low birth rate, or miscarriage · infection of embryo usually occurs in last 2 months Congenital Syphilis · transmitted via the placenta (moms blood) · severe damage to the fetus: ↳ mental development ↳ nerve system Prevention of Congenital Infections · screening during pregnancy · reducing infection rates in the population · vaccination when possible ↳ abnormalities due to tissue damage, facial deformities ↳ death (sometimes) · "Hutchinson's Teeth" - characteristic abnormality (soft enamel notches)