Dr. med. Dirk Manski

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Urinary Tract Infections (2/4): Causes, Pathogens and Risk Factors

Review literature: (Krieger, 2002) (Nickel, 2005a) (Nickel, 2005b) (Sussman and Gally, 1999) (Wagenlehner and Naber, 2006) (DGU 2009, S3-guideline for UTI).

Etiology and Pathogenesis of Urinary Tract Infections

Mechanisms of colonization:

Urinary tract infections are most often caused by ascending colonization, possible are hematogenous or lymphatic colonization and invasion of pathogens from neighboring organs.

Ascending infection:

Ascending infections are the most common cause of urinary tract infections. As the female urethra is short and intestinal bacteria tend to colonize the perineum and vulva, women tend more often than men to urinary tract infections.

Hematogenous infection:

Hematogenous caused urinary tract infections are rare: urogenital tuberculosis, renal abscess, perinephric abscess or in some cases epididymitis.

Lymphatic spread of urinary tract infection:

Lymphatic spread of UTI are rare and unsecured. There are speculations about the lymphatic spread of rectal bacteria to prostate, bladder, and internal female sex organs.

Direct spread from adjacent organs:

Urinary tract infections may be causes by direct spread of abscess or fistula formation (e.g. abscess after PID, vesicovaginal fistula, vesicosigmoidal fistula).

Pathogens in Urinary Tract Infections:

Pathogens of uncomplicated urinary tract infections are most common E. coli (80%), followed by Proteus mirabilis, Staphylococcus saprophyticus, and Klebsiella pneumoniae [Table pathogen spectrum of bacterial cystitis].

Pathogen spectrum of acute uncomplicated cystitis in women in Germany, modified after the S3 guideline for urinary tract infections of the DGU.
Gram-negative pathogens:
Escherichia coli 77
Proteus mirabilis 5
Klebsiella pneumoniae 2-3
Enterobacter spp. 1
Citrobacter spp. 1
Other Enterobacteriaceae 2
Gram-positive bacteria
Staphylococcus saprophyticus 3
Staphylococcus aureus 2
Other staphylococci 4
Enterococcus spp. 3
Streptococcus spp. 1

Further pathogens of urinary tract infections:

Bacterial Virulence Factors in Urinary Tract Infections:

Most UTIs are caused by E. coli (80% of ambulatory patients). Uropathogenic E. coli (UPEC) tend to adhere more tightly to the urothelium and vaginal epithelium. The increased adherence is mediated by fimbriae or pili. The subdivision of virulence factors of E. coli involves the ability to agglutinate animal erythrocytes and on the possibility to inhibit the agglutination with sugar: type 1 pili (mannose-sensitive hemagglutnation = MSHA) and type 2 pili (mannose-resistant hemagglutination = MRHA).

Most UTIs are caused by E. coli with MSHA or MRHA pili. The MSHA properties are responsible for binding to the urothelium, the MRHA property allows invasive infection. MSHA properties alone are not sufficient for urinary tract infection. Further bacterial virulence factors of E. coli are hemolysins (detroy urothelium cells), the formation of intracellular bacterial communities and biofilm production.

Gender-Independent Risk Factors for Urinary Tract Infection:

Female Risk Factors for Urinary Tract Infections:

Male Risk Factors for Urinary Tract Infection:

Index: 1–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


Deutsche Gesellschaft für Urologie, S3-guideline for urinary tract infection
Epidemiologie, Diagnostik, Therapie und Management unkomplizierter bakterieller ambulant erworbener Harnwegsinfektionen bei erwachsenen Patienten
AWMF, 2010, Register-Nr. 043/044

Bauer u.a. 2002 BAUER, H. W. ; RAHLFS, V. W. ; LAUENER, P. A. ; BLESSMANN, G. S.:
Prevention of recurrent urinary tract infections with immuno-active E. coli fractions: a meta-analysis of five placebo-controlled double-blind studies.
In: Int J Antimicrob Agents
19 (2002), Nr. 6, S. 451–6

Kass 2002 KASS, E. H.:
Asymptomatic infections of the urinary tract. 1956.
In: J Urol
167 (2002), Nr. 2 Pt 2, S. 1016–9; discussion 1019–21

Krieger 2002 KRIEGER, J. N.:
Urinary tract infections: what’s new?
In: J Urol
168 (2002), Nr. 6, S. 2351–8

Nickel 2005a NICKEL, J. C.:
Management of urinary tract infections: historical perspective and current strategies: Part 1–Before antibiotics.
In: J Urol
173 (2005), Nr. 1, S. 21–6

Nickel 2005b NICKEL, J. C.:
Management of urinary tract infections: historical perspective and current strategies: Part 2-Modern management.
In: J Urol
173 (2005), Nr. 1, S. 27–32

Sobel und Vazquez 1999 SOBEL, J. D. ; VAZQUEZ, J. A.:
Fungal infections of the urinary tract.
In: World J Urol
17 (1999), Nr. 6, S. 410–4

Sussman und Gally 1999 SUSSMAN, M. ; GALLY, D. L.:
The biology of cystitis: host and bacterial factors.
In: Annu Rev Med
50 (1999), S. 149–58

Tauchnitz 1991 TAUCHNITZ, C:
In: HAHN, H (Hrsg.) ; FALKE, D (Hrsg.) ; KLEIN, P (Hrsg.): Medizinische Mikrobiologie.
Berlin, Heidelberg : Springer, 1991, S. 501–507

Wagenlehner und Naber 2006 WAGENLEHNER, F. M. ; NABER, K. G.:
Treatment of bacterial urinary tract infections: presence and future.
In: Eur Urol
49 (2006), Nr. 2, S. 235–44

  Deutsche Version: Ursachen einer Harnwegsinfektion