normal flora in gu tract

8/13/2019 Normal flora in Gu Tract

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a presentation from FARRAH ERMAN

Introducing

normal flora in GU tract


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Microbeinside your GU tract !

We have features for every step of the way

What is

normal?

What is

abnormal?

How come?


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Kinds of interactions between microorganism and host

a. mutualism - beneficial to both.b. commensalism - beneficial to one; not harmful to other.

c. parasitism - beneficial to one; harmful to other.

Majority of the normal flora - commensal or mutualistic

relationship with the host. Example: 1011 bacteria/g fecal

material - most harmless.

This can change if:

there is a change in the many chemical, cellular, andimmunologic mechanisms that have evolved to prevent bacterial

infections (underlying disease)

local anatomic barriers are breached (trauma,

instrumentation)


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Factors that influence the kind and number of

microorganisms at any body site are:

1. availability or unavailability of oxygen;

2. the availability of appropriate receptor sites for attachment;

3. the pH of the host site (stomach, vagina);

4. the availability of nutrients;

5. the influence exerted by other microorganisms at the site;6. the immunological response of the host to the presence of themicrobe.

Normal flora = indigenous flora = autochthonous flora = commensals

The skin, the oral cavity, the GI tract, and the female genital tract:resident normal flora

Esophagus, urinary tract, and stomach - few microbes.

Blood, spinal fluid, urine, and endothelial tissues - normally sterile.


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Specific bacterial virulence factors:

Colonization of surfacesmediated by adhesins. Examples: fimbriae (pili)

of some E. coli contain

carbohydrate-specificreceptors (lectins). P pili ofE. coli bind to a-D-gal-(1,4)-b-D-gal linked to aceramide lipid of bladder

epithelium. The adherentbacteria are not washedout of the bladder withthe flow of urine.


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Bacterial invasion of host tissues

Most adherence does not lead to invasion unless

mechanical or chemical injury allows the bacteria

to penetrate the skin or intestinal epithelium.


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Anatomical Lines of Defense

A. Acidity

B. Everything goes out

C. Mucosal lining

D. Normal flora

1. Urinary bladdersterile

2. Vagina and urethra - lactobacilli, Staph.

epid, diphtheroids, Strep. Sp

E. A matter of distance -> urethra- rectum


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What is normal?

Urine is normally sterile, and since the urinary tract is flushed with urine every few

hours, microorganisms have problems gaining access and becoming established


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The flora of the anterior urethra, as indicated principally by urine

cultures, suggests that the area my be inhabited by a relativelyconsistent normal flora consisting of Staphylococcus epidermidis,

Enterococcus faecalis and some alpha-hemolytic streptococci.

Their numbers are not plentiful

In addition, some enteric bacteria (e.g. E. coli, Proteus) andcorynebacteria, which are probably contaminants from the skin,

vulva or rectum, may occasionally be found at the anterior urethra.


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IN WOMEN?

The vagina becomes colonized soon after birth with corynebacteria, staphylococci,streptococci, E. coli, and a lactic acid bacterium historically named "Doderlein's

bacillus" (Lactobacillus acidophilus).


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During reproductive life, from puberty to menopause, the vaginal epithelium containsglycogen due to the actions of circulating estrogens.

Doderlein's bacillus predominates glycogen lactic acid.

The lactic acid and other products of metabolism inhibit colonization by all except this

lactobacillus and a select number of lactic acid bacteria. The resulting low pH of the

vaginal epithelium prevents establishment by most other bacteria as well as thepotentially-pathogenic yeast, Candida albicans. This is a striking example of the

protective effect of the normal bacterial flora for their human host.


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What is abnormal?

Recurrent urinary tract infections (UTIs) fall into one of two categories:

Reinfectionoccurs after successful therapy for a UTI, is caused by bacteria from outsidethe

urinary tract and characterized by varying, delayed recurrencewith different strains.Relapse is caused by bacteria that persist within the urinary tract despite antimicrobial therapy

and characterized by rapid recurrencewith the same strain.


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healthy women: (Escherichia coli[E. coli], Staphylococcus saprophyticus) and risk

factors (sexual intercourse, spermicide use, low vaginal estrogen, and genetic

predisposition) that cause acute, uncomplicated cystitis (an inflammation of thebladder).

Healthy young men: (lack of circumcision, or intercourse with a woman with a

UTIthat cause acute, uncomplicated cystitis

. In most of these women and some of these men, the infections are

uncomplicated(the urinary tract has normal structure and function) and are cured

and prevented by antimicrobial therapy.

Sometimestypically in some young women, most elderly women, and most men

UTIs are complicated.

This means the urinary tract is functionally and structurally abnormal, the

host is compromised, and/or the bacteria have increased virulence factorsand/or antimicrobial resistance (Table 1). These factors increase the chance of

acquiring bacteria and decrease the effectiveness of therapy.


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ETIOLOGI

complicated UTIs are caused by a broad range of bacteria including E. coli, other gram-negative bacteria (including Proteus, Klebsiella, and pseudomonas species), and gram-

positive bacteria (enterococci and staphylococci).


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