Lecture 17: Infections of the Urogenital System V

True or false: The entire urinary tract is directly connected to the exterior and mucosal bacterial flora.

true

What structure of the urinary tract are considered sterile?

structures proximal to the distal urethra

What refers to the bacterial colonization (infection) of urine or any urinary tract organ, except distal urethra which has a normal bacterial flora?

Urinary tract infection

What is the most common type of UTI in dogs?

lower UTI (cystitis)

What are the most frequently isolate pathogens in canine UTIs?

E. coli, proteus, klebsiella

When examining the a sample for a suspected UTI case, you note gram negative rods that are urease negative. What pathogen is causing the UTI?

E. coli

When examining the a sample for a suspected UTI case, you note gram negative coccobacilli that are rapid urease positive. What pathogen is causing the UTI?

proteus spp.

When examining the a sample for a suspected UTI case, you note gram negative small rods that are delayed urease positive. What pathogen is causing the UTI?

Klebsiella spp.

When examining the a sample for a suspected UTI case, you note gram positive cocci in bunches that are urease positive. What pathogen is causing the UTI?

Staphylococcus spp.

When examining the a sample for a suspected UTI case, you note gram positive cocci in chains that are urease negative. What pathogen is causing the UTI?

Streptococcus spp.

What are the most frequently isolated pathogens causing UTI in cats?

E. coli, proteus, staphylococcus aureus, pasteurella multocida

What are the most frequently isolated pathogens causing UTI in horses?

E. coli, staphylococcus aureus, streptococcus

What are the most frequently isolate pathogens causing UTI in cattle/sheep/goats?

• E. coli and Trueperella pyogenes

• Corynebacterium renale, C. pilosum, and C. cystitidis in cattle

How is bacteria encountered in the case of a UTI?

• usually, normal flora of the lower UT (distal urethra)

• opportunistic infections

• normal flora in abnormal bladder

What type of infection is a UTI?

opportunistic infection

What is the most common mode of bacterial entry in a UTI?

ascension: bacteria ascend through the urethra into normally sterile bladder

What host UT defenses prevent ascension?

• flushing by urine to prevent access to bladder

• anti-adherence mechanisms

  • urinary oligosaccharides to coat bacteria, prevent receptor binding

  • bladder glycosaminoglycan to coat transitional epithelium

  • epithelial cell exfoliation

  • urine osmolality to inhibit bacterial growth

When does bacterial ascension occur?

when defenses are disrupted

What is the number one cause of cystitis?

abnormal urine flow

What are factors that can impair host defenses leading to UTI?

• urinary stasis (locked in house all day)

• mechanical impediments to flow (cystic calculi, indwelling catheters- foreign body)

• damage to the epithelial surface that impedes urine flow and promotes bacterial colonization

What virulence factors prevent bacteria from being washed away in UTIs?

fimbriae (pili) to mediate attachment to epithelium

What are the clinical signs of lower UTI?

• dysuria

• pollakiuria: increased frequency urination

• oliguria: reduction in daily output

• anuria: complete absence of urine

• stranguria: straining and difficulty

• hematuria: blood in urine (beginning = urethra, end = bladder)

• small, firm, sometime painful bladder on palpation

What is ruled out when a patient presents with dysuria?

• urethrocystitis

• pyelonephritis

• prostatitis

How are lower UTIs diagnosed?

• clinical signs

• urinalysis

• chem dipsticks

• microscopic exam

If the pH of the urine is acidic, what organisms could be causing the UTI?

E. coli, Strep, Enterococcus

If the pH of the urine is alkaline, what organisms could be causing the UTI?

Proteus, staph

What is the best source to obtain urine for UTI testing and why?

cystocentesis because the bladder is normally sterile

What is the complication with using catheterization to obtain a urine sample?

the process will introduce genital flora into the urine and can cause false positive

How should a diagnosis of a lower UTI be interpreted?

• species: common UTI pathogen, single species

• numbers: greater than 100,000 per ml

• consistent urinalysis results: pyuria, hematuria

Why is the urinary tract a conditionally susceptible site?

antibiotics that are renal excreted in active form will be concentrated in the urine