(1) Etiology of Urinary Tract Infection + Enterobacteriaceae

8/7/2019 (1) Etiology of Urinary Tract Infection + Enterobacteriaceae

1/14

Etiology of Urinary TractEtiology of Urinary TractInfectionsInfections

Prof. Dr. Mohamed ElProf. Dr. Mohamed El--SweifySweify


2/14

Microbial flora in the UTMicrobial flora in the UTOnly urethra hosts microflora, Other areas are sterileOnly urethra hosts microflora, Other areas are sterile

11)) Resident colonizing microfloraResident colonizing microflora::

Coagulase negative staph (exceptCoagulase negative staph (except S. saprophyticusS. saprophyticus).).

Viridans and non hemolytic StreptococciViridans and non hemolytic Streptococci

Corynebacterium sppCorynebacterium spp..

Lactobacilli (anerobic)Lactobacilli (anerobic)

Non pathogenicNon pathogenic Neisseria sppNeisseria spp..

SaprophyticSaprophytic Mycobacteria sppMycobacteria spp..

SaprophyticSaprophytic Mycoplasma sppMycoplasma spp..

Anerobic cocci and gram negative bacilli.Anerobic cocci and gram negative bacilli.

22)) Transient colonizers (potentially pathogenic)Transient colonizers (potentially pathogenic)::

Aerobic gram negative rods of gut flora (enterobacteriaceae)Aerobic gram negative rods of gut flora (enterobacteriaceae)

Candida albicansCandida albicans, and other yeasts., and other yeasts.


3/14

Urine is normally Sterilewhy ?Urine is normally Sterilewhy ?

Due to Innate protective mechanisms:Due to Innate protective mechanisms:

1.1. The free flow of urine through an anatomicallyThe free flow of urine through an anatomically

normal urinary tract.normal urinary tract.

2.2. Physical barriers in UT: Urethral length, urethral/Physical barriers in UT: Urethral length, urethral/

urethral valves, oneurethral valves, one--way urine flow.way urine flow.3.3. Low pH, high osmolarity, and high NHLow pH, high osmolarity, and high NH33 content ofcontent of

urine are bacteriostatic.urine are bacteriostatic.

4.4. Prostatic secretions and IgA antiProstatic secretions and IgA anti--bacterialbacterialantibodies are bacteriostatic as well.antibodies are bacteriostatic as well.

5.5. PP antigen in mucosal secretions.antigen in mucosal secretions.

6.6. Absence ofAbsence ofPP antigen on mucosal cellsantigen on mucosal cells ((see latersee later).).


4/14

Incidence of UTI inIncidence of UTI in Females > Males,Females > Males, why?why?

1.1. Short female urethraShort female urethra

2.2. Urethra is closer to anal orifice.Urethra is closer to anal orifice.

3.3. Sexual activity and/or antibiotic therapy increaseSexual activity and/or antibiotic therapy increasechance of contaminating female urethra withchance of contaminating female urethra with

uropathogenic organisms.uropathogenic organisms.

4.4. Anatomical and hormonal changes in pregnancyAnatomical and hormonal changes in pregnancy

5.5. Use of contraceptive foams, gels, or diaphragmUse of contraceptive foams, gels, or diaphragmincreases colonization of vagina and introitus.increases colonization of vagina and introitus.

6.6. ~~ 2020% of all women have UTI at least once.. The% of all women have UTI at least once.. The

incidence increases with age.incidence increases with age.


5/14

Conditions which predispose to UTI in generalConditions which predispose to UTI in general((see also slide#see also slide#11))

Stasis Invites Infection.. a Golden Rule

Stasis Invites Infection.. a Golden Rule In Males >In Males >5050--6060 years with enlarged prostate urine stasis in UB.years with enlarged prostate urine stasis in UB.

UT stones stasis above stoneUT stones stasis above stone infectioninfection..

Traumatic injury of ureterTraumatic injury of ureter healing by fibrosishealing by fibrosis stricture andstricture andnarrowingnarrowing stasisstasis UTI.UTI.

Foreign body into UT (catheter) infection.Foreign body into UT (catheter) infection.

2020% of in% of in--patients with shortpatients with short--term catheter develop nosocomial UTIterm catheter develop nosocomial UTIIts the most common NCI in USAIts the most common NCI in USA UTI is the most common source of nosocomial bacteremia as well !!UTI is the most common source of nosocomial bacteremia as well !!

Circumcision protects against UTI in young male infants.Circumcision protects against UTI in young male infants.The periurethral area was found to be more frequently and moreThe periurethral area was found to be more frequently and moreheavily colonized withheavily colonized with uropathogens, especially E. coli, inuropathogens, especially E. coli, inuncircumcised infants, than in circumcised infantsuncircumcised infants, than in circumcised infants..


6/14

Renal stagRenal stag--horn stonehorn stone is a branched stone, filling theis a branched stone, filling the

renal pelvis and calyces, due to bacteria producing NHrenal pelvis and calyces, due to bacteria producing NH33from urea (ureafrom urea (urea--splitter, most often Proteus orsplitter, most often Proteus or

Klebsiella pneumoniaeKlebsiella pneumoniae, and some other strains of, and some other strains of

Enterobacteraciae).Enterobacteraciae).

The NHThe NH33 precipitates triple phosphate = MgNHprecipitates triple phosphate = MgNH44POPO44..

Infection cannot be cured until the stagInfection cannot be cured until the stag--horn is surgicallyhorn is surgically

removed.removed.

Bacterialinfection

Stag-hornstone

formation

SecondBacterialinfection


7/14

Pathogenesis of UTIPathogenesis of UTI


8/14

Urine is bacteriostatic to most of the commensal organisms,Urine is bacteriostatic to most of the commensal organisms,inhabiting the perineum and vagina as: lactobacillus,inhabiting the perineum and vagina as: lactobacillus,

corynebacterium, diptheroids, and Scorynebacterium, diptheroids, and Staph. epidermidistaph. epidermidis..

In contrast, many gram negative organisms thrive in urine.In contrast, many gram negative organisms thrive in urine.

So, most infections are caused by aerobic gram negativeSo, most infections are caused by aerobic gram negative

rods of the GIT.rods of the GIT. The cause of infection inThe cause of infection in uncomplicated outpatientsuncomplicated outpatients isis

typically as follows:typically as follows:

8585% of all UTI are due to% of all UTI are due to E. coliE. coli . while;. while; 1010 % are due to Klebsiella, Proteus, Pseudomonas,% are due to Klebsiella, Proteus, Pseudomonas,

Enterobacter. (both via ascending rout)Enterobacter. (both via ascending rout)


9/14

NosocomialNosocomialUTI is less likely to be caused byUTI is less likely to be caused by E.E.colicoli..!!..!! WhyWhy ??

Gram negative rods thrive in urine and are speciallyGram negative rods thrive in urine and are speciallyadapted to cause infection by havingadapted to cause infection by having fimbriaefimbriae withwithterminal receptors for specific glycolipids andterminal receptors for specific glycolipids andglycoproteins.glycoproteins.

E. coliE. coli species causing UTIs typically have fimbriaespecies causing UTIs typically have fimbriae(pili) with a terminal receptor for the (pili) with a terminal receptor for the PP antigen. antigen.

and, What isand, What is PP antigen ??antigen ??

See nextSee next!!!!


10/14

PP antigen is a blood group marker (receptor),antigen is a blood group marker (receptor),

also found on surface of cells lining thealso found on surface of cells lining theperineum and urinary tract.perineum and urinary tract.

~~ 7575% of population expresses% of population expresses PP antigen.antigen.

PP antigen is also found in vaginal and prostaticantigen is also found in vaginal and prostatic

secretionssecretions::

Thesesecreted (free) Thesesecreted (free) PPantigens areantigens are

protectiveprotective ....


11/14

..Simply because they bind to the bacterial receptors,..Simply because they bind to the bacterial receptors,

keeping them busy (occupied)keeping them busy (occupied) Preventing suchPreventing such

organisms from using them to bind to surface epithelium.organisms from using them to bind to surface epithelium.

(Now go back to slide #(Now go back to slide # 33 nownow.hurry please !!).hurry please !!)


12/14

Most common uropathogenic bacteria:Most common uropathogenic bacteria:

1.1. Most bacterial uropathogens are members of theMost bacterial uropathogens are members of the

EnterobacteriaceaeEnterobacteriaceae family:family:A.A. E.coli,E.coli,

B.B. Klebiella oxytoca, K. pneumoniae,Klebiella oxytoca, K. pneumoniae,

C.C. Proteus mirabilis, P. vulgarisProteus mirabilis, P. vulgaris

D.D. Enterobacter aerogenesEnterobacter aerogenes

E.E. Citrobacter freundiiCitrobacter freundii

2.2. EnterococciEnterococci

3.3. Staphylococcus saprophyticusStaphylococcus saprophyticus

4.4. Pseudomonas aeruginosa.Pseudomonas aeruginosa.


13/14

Diagnosis of UTIDiagnosis of UTI Among asymptomatic females of CB age or older, >Among asymptomatic females of CB age or older, >101055

cfu/ml of single bacterial species and >cfu/ml of single bacterial species and >55 WBC/hpf= UTIWBC/hpf= UTI

UTIs that show midUTIs that show mid--stream bacterial count


14/14

Thank you..

Documents

(1) Etiology of Urinary Tract Infection + Enterobacteriaceae