UT7 - Infeções do Trato Urinário (1)

Question 1

Urinary Tract Infections - Definitions - UTI, Bacteriuria, Pyuria?

Answer 1

◆ UTI is an inflammatory response of the urothelium to bacterial invasion that is usually associated with bacteriuria and pyuria.
◆ Bacteriuria is the presence of bacteria in the urine, which is normally free of bacteria.
◆ Pyuria, the presence of white blood cells (WBCs) in the urine, is generally indicative of infection and/or an inflammatory response of the urothelium to the bacterium, stones, or other indwelling foreign body.
– Bacteriuria without pyuria is generally indicative of bacterial colonization without infection of the urinary tract.
– Pyuria without bacteriuria warrants evaluation for tuberculosis, stones, or cancer.

◆ Uma ITU sem piúria é uma situação verdadeiramente rara e à qual devemos levantar sérias dúvidas.

Question 2

Urinary Tract Infections - Definitions - Cystitis?

Answer 2

◆ Cystitis describes a clinical syndrome of dysuria, frequency, urgency,(por vezes hematúria) and occasionally suprapubic pain.
◆ These symptoms, although generally indicative of bacterial cystitis, may also be associated with infection of the urethra or vagina or noninfectious conditions such as interstitial cystitis, bladder carcinoma, or calculi.

Question 3

Urinary Tract Infections - Definitions - Acute Pyelonephritis?

Answer 3

◆ Acute pyelonephritis is a clinical syndrome of chills, fever, and flank pain that is accompanied by bacteriuria and pyuria, a combination that is reasonably specific for an acute bacterial infection of the kidney.
◆ Síndrome que caracteriza uma infeção do aparelho urinário superior (rim).
◆ Além das queixas do trato urinário inferior, também febre, arrepios e dores no flanco.

Question 4

Urinary Tract Infections - Definitions - Chronic Pyelonephritis?

Answer 4

◆ Chronic pyelonephritis describes a shrunken, scarred kidney, diagnosed by morphologic, radiologic, or functional evidence of renal disease that may be postinfectious but is frequently not associated with UTI.
◆ Associada a pielonefrites de repetição por cálculos, refluxo vesico-ureteral, e que leva a alterações crónicas do rim (cicatrizes e áreas disfuncionais).

Question 5

Definitions - First or isolated?

Answer 5

◆ First or isolated infection is one that occurs in an individual who has never had a UTI or has one remote infection from a previous UTI.

Question 6

Definitions - Unresolved?

Answer 6

◆ Unresolved infection is one that has not responded to antimicrobial therapy and is documented to be the same organism with a similar resistance profile.
– E mantém bacteriúria pelo mesmo organismo! (causas mais à frente)

Question 7

Definitions - Recurrent?

Answer 7

◆ Recurrent infection is one that occurs after documented, successful resolution of an antecedent infection.
– Reinfection describes a new event associated with the reintroduction of bacteria into the urinary tract from outside (novo evento associado a nova infeção)
– Bacterial persistence refers to a recurrent UTI caused by the same bacteria reemerging from a focus within the urinary tract, such as an infectious stone or the prostate. Quando temos persistência bacteriana -> pensar em alguma situação anómala que esteja a condicionar

Question 8

Correctable Urologic Abnormalities that cause bacterial persistence?

Answer 8

◆ Infection stones
◆ Chronic bacterial prostatitis
◆ Unilateral infected atrophic kidneys
◆ Ureteral duplication and ectopic ureters
◆ Foreign bodies

◆ In patients whose bacteriuria fails to resolve after appropriate antimicrobial therapy or who have rapid recurrence of infection, abnormalities that cause bacterial persistence should be sought.
◆ Although these patients are uncommon, it is important to identify them because they may have correctable urologic abnormalities that represent the only surgically curable causes of recurrent UTIs.

Question 9

Causes of Unresolved Bacteriuria in Descending order of importance?

Answer 9

◆ Bacterial resistance to the drug selected for treatment
◆ Development of resistance from initially susceptible bacteria
◆ Bacteriuria caused by two different bacterial species with mutually exclusive susceptibilities
◆ Rapid reinfection with a new resistant species during initial therapy for the original suspceptible organism
◆ Azotemia
◆ …

◆ Unresolved infection indicates that initial therapy has been inadequate in eliminating symptoms and/or bacterial growth in the urinary tract.
◆ If the symptoms of UTI do not resolve by the end of treatment or if symptoms recur shortly after therapy, urinalysis and urine culture with susceptibility testing should be obtained.

Question 10

Uncomplicated vs Complicated?

Answer 10

◆ Uncomplicated
– Women
– Premenopausal
– Healthy, no known anatomic or functional abnormality to the urinary tract

◆ Complicated
– Everyone else?
– Men, women, or children with functional, metabolic, or anatomical conditions that may increase the risk of treatment failure or serious outcomes
– Obstruction, stone, pregnancy, male sex, diabetes, neurogenic bladder, renal insufficiency, immunosuppression

Question 11

Incidence and Epidemiology?

Answer 11

◆ UTIs are considered to be the most common bacterial infection
◆ Nearly 30% of women will have a symptomatic UTI requiring antimicrobial therapy by age 24, and almost half of all women will experience a UTI during their lifetime.
◆ Catheter-associated UTIs (CAUTIs) are the most common nosocomial infection.
◆ Alto impacto económico

Question 12

Virulence vs Host factors?

Answer 12

◆ UTIs are a result of interactions between the uropathogen and the host.
◆ Successful infection of the urinary tract is determined in part by the virulence factors of the bacteria, the inoculum size, and the inadequacy of host defense mechanisms.

◆ Interação entre os fatores de virulência das bactérias e os fatores protetores do hospedeiro – é nesta dinâmica que surgem as infeções.
◆ Podemos ter colonização do aparelho urinário inferior e não haver clínica de infeção.

Question 13

Host protective factors?

Answer 13

◆ Flushing mechanism of micturition.
◆ Acid pH of urine (4,6-6) antibacterial.
◆ Acid vaginal pH (3,5-4,5) suppresses colonization.
◆ Urinary Tamm-Horsefall protein (secreted by ascending loop of Henle), blocks E. coli.
◆ Chemotactic factors – interleukin-8

Question 14

Bacterial virulence factors?

Answer 14

◆ E. coli strains expressing O-atg cause a high proportion of infections
◆ Bacterial adhesins – an expression of a number of adhesins that allow it to attach to urinary tract tissues. These adhesins are classified as either fimbrial or afimbrial.
◆ P-fimbriae enhance attachment of E. coli to uroepithelial cells
◆ Motile bacteria ascend the ureter against urine flow

◆ Bacterial urease (Proteus) splits urea – loss of acid pH – stone formation
◆ Gram-negative endotoxin decreases ureteral peristalsis
◆ Hemolysin damages the renal tubular epithelium
◆ Aerobactin of E. coli promotes iron accumulation for bacterial replication

Question 15

Host agravating factors?

Answer 15

◆ High post-void residual volume
◆ Turbulent urethral flow (stricture)
◆ Foreign bodies
◆ Atrophic vaginal mucosa
◆ Vesico-ureterl reflux
◆ Childhood pyelonephritis
◆ Diabetic nephropathy
◆ Chronic pyelonephritis

Question 16

Vias de aparecimento das infeções - Ascending route?

Answer 16

◆ Most common
◆ Colonization of the urethra and peri-urethral tissue is the initial event
◆ More in women than in men due to short female urethra
◆ Once in the bladder, multiply, then pass up the ureters (esp. If vesicoureteral reflux) to the renal pelvis and parenchyma
◆ Hospital infection associated with lower urinary tract instrumentation (catheterization, cystoscopy)

Question 17

Vias de aparecimento das infeções - Hematogenous route & Lymphatic route?

Answer 17

Hematogenous route
◆ Less frequent than ascending infection
◆ Kidney a common site of abscess in St aureus bacteremia, less often in candidemia, rarely with gram-negative bacteremia
◆ Hematogenous seeding of kidney also occurs with Salmonella (typhoid) and Mycobacterium tuberculosis

Lymphatic Route
◆ Direct extension of bacteria from the adjacent organs via lymphatics may occur in unusual circumstances, such as a severe bowel infection or retroperitoneal abscesses.

Question 18

Etiologia UTIs?

Answer 18

◆ E. coli is by far the most common cause of UTIs, accounting for 85% of community-acquired and 50% of hospital-acquired infections.
◆ Clinically symptomatic UTIs in which only anaerobic organisms are cultured are rare.
◆ Ao tratar a ITU, pensar que a grande maioria é por Echerichia coli mas considerar também os gram-negativos e S. saprophyticus em mulheres jovens.
◆ Pensar em TB quando surgem situações de piúria persistente mas não associada à presença de bactérias na urina!

Question 19

Asymptomatic bacteriuria in adults?

Answer 19

◆ Asymptomatic bacteriuria in an individual without urinary tract symptoms is defined by a mid-stream sample of urine (MSU), showing bacterial growth ≥ 105 cfu/mL, in two consecutive samples in women and in a single sample in men
◆ É uma entidade muito prevalente que não deve ser tratada na maioria das situações.
◆ Corresponde à presença de bactérias na urina sem qualquer sintoma.

Question 20

Asymptomatic bacteriuria in adults(2)?

Answer 20

◆ In healthy individuals, the absence of symptoms is clear cut, but, for example, in catheterized or neurologically compromised patients, it may be difficult to discern whether the UTI is truly asymptomatic.
◆ E. coli is the most common isolate among patients with bacteriuria.
◆ Screening and treatment of ABU is not recommended in patients without risk factors.
◆ Não pedir exame bacteriológico de rotina se não existir clínica de infeção!

Question 21

Asymptomatic bacteriuria in adults – Quem tratar?

Answer 21

◆ Pregnant women
– Based on the beneficial maternal and fetal effects of antibiotic treatment pregnant women should be screened and treated for ABU.
– standard short course treatment should be applied to treat ABU in pregnancy
◆ Prior to urological surgery
– A urine culture must therefore be taken prior to such interventions and in case of ABU, pre-operative treatment should be given.