Genito-urinary infections

ADVANCE ORGANIZER
Genito-urinary tract infections are either caused by opportunists that are part of the normal flora or by pathogens introduced from the outside. Many of these require direct human -to-human contact, thus they are often called STDs [sexually transmitted diseases].

READING Assignment CHAPTER 27

ANATOMY AND PHYSIOLOGY
The main structures of the urinary tract–the kidneys, bladder, ureter and urethra are generally sterile.
The urinary tract of women is more susceptible to infection because the urethra is shorter and because it is closer to the genital and intestinal tracts. The flushing action of urination is a key defense mechanism against bladder infections.
The vagina is the site of entry for a number of infections. Sexual activity is thought to play a significant role in the introduction of uropathogens into the urethra. In addition the use of diaphrams and spermicides has also been shown to predispose women to urinary tract infections [UTIs]. Specific pathogens can bind specifically to vaginal and peri-urethral epithelial cells. This binding is greatest when estrogen levels reach their peak during the menstral cycle. UTIs are the most common reason why adolescent and adult women seek health care. Interestingly, it has been observed that prostatic fluid inhibits the growth of common urinary tract pathogens in men.
NORMAL FLORA IN THE FEMALE GENITAL TRACT
In women, normal flora is dependent upon the hormone, estrogen, promoting the deposition of glycogen in cells lining the vagina. Lactobacilli normally help prevent colonization by pathogens.

URINARY TRACT INFECTIONS

Escherichia coli is the cause of the majority of urinary tract infections. Pseudomonas aeruginosa infections are difficult to treat because these bacteria are quite antibiotic resistant. 90% of urinary tract infections are caused by enterobacteria from the person’s own normal flora. Kidney infections [pyelonephritis] can result from bladder infections [cystitis].
GENITAL TRACT INFECTIONS

BACTERIAL

Gonorrhea, is among the most prevalent venereal diseases. It is caused by Neisseria gonorrhoeae, a Gram negative coccobacillus with specific attachment pili. We will discuss its virulence mechanisms and its phagocytosis as a stepwise process.
A very destructive eye disease, ophthalmia neonatorum can be acquired during passage through the birth canal. Infections in men may include the prostate and the testes. In women when infection spreads upward through the uterus and into the fallopian tubes, pelvic inflammatory disease results. This can cause sterility but also promotes ectopic pregnancy. This is the most common of the reportable (to the Center for Infectious Diseases in Atlanta) bacterial diseases. Resistance to anti-microbial medicines is increasing.
12 Nov 2015 news

Syphilis is a progressive chronic disease transmissible during its primary and secondary stages. It can pass the placenta from mother to fetus. Diagnosis can be missed because its symptoms mimic other diseases. It is caused by Treponema pallidum, a slender spiral bacterium best seen under dark-field illumination or with special stains. The cell adhesion molecules that this invader eludes are called ___________. These are probably responsible for the containment of the initial infection in a chancre.

Chlamydia infections are clinically very similar to gonorrhea. They are caused by Chlamydia trachomatis , a spherical obligate intracellular bacterium. Asymptomatic carriers are common.

Being an intracellular organism makes it necessary for the specific immune response to use a whole new strategy. Different locations of infection mean different immune effector mechanisms are needed to clear the infection.Chancroid is caused by Haemophilus ducreyi, a small Gram-negative rod that require X factor for pathogenesis. It is common in some tropical countries, that is, second to gonorrhea. Chancroid is an ulcerative sexually transmitted disease.

Viral STDs

Genital herpes simplex is caused by herpes simplex virus type 2. It is among the most common venereal diseases causing painful recurrent genital sores. The viral chromosome exists within nerve cells during asymptomatic times. The disease is incurable.

There is another non-adaptive response that helps keep these lesions in check. This involves both the production of interferons [which inhibit viral replication and activate additional host defenses] and Natural Killer [NK] cells. NK cells can serve as an early defense against certain intracellular infections. NK cells were first identified by their ability to kill certain lymphoid tumor cell lines in tissue culture without the need for prior immunization or activation. NK cells are known to be important in the early phases of infection with several intracellular pathogens–Herpes and Listeria monocytogenes are two examples. Without NK cells these infections are much more devastating.
The activity of NK cells is increased by 20 to 100 fold by exposure of NK cells to interferons alpha and beta. The killing activity of NK cells can also be increased by IL12. On the target cell side, TNF-alpha and interferon-gamma render the infected host cells [the targets] more susceptible to lysis by NK cells.

Cytomegla Virus [CMV]-will be discussed later in the course.

Genital warts are caused by human papillomaviruses. Some strains are strongly associated with cervical cancer screening by PAP test is effective is providing a early detection. Again, there is no cure for infection and asymptomatic infections are common.

HIV (human immunodeficiency virus) infection is pandemic and probably fatal in all cases. No vaccine or medical cure is known. Transmission can occur during the asymptomatic period that can last for years. Spread of infection can only be stopped by prevention. Immune deficiency is a late stage of HIV disease and is called AIDS.

Other genital tract infections
The exact cause of bacterial vaginosis is unknown. It is characterized by a decrease in lactobacilli and increase in Gardnerella vaginalis and anaerobic bacteria. “Clue cells” are diagnostic.

Yeast vulvovaginitis is caused by Candida albicans, a part of normal flora. Suffering from this is a common aftermath of treatment with antimicrobial medicines that suppress other normal vaginal bacterial flora.
Vaginitis can be caused by the protozoan Trichomonas vaginalis, — flagellated . Infections in men are usually asymptomatic and carriers are common.

Puerperal fever (also known as childbirth fever) can be caused by Streptococcus pyogenes. This is spread by contaminated instruments or hands of medical attendants who are asymptomatic carriers and results in a severe infection of the female genital system following childbirth.
Toxic shock syndrome is caused by certain strains of Staphylococcus aureus. The mechanism involves bogus activation of many T cells in the immune system–by a “superantigen.” That sounds great but remember that the immune system has T cells that are specific for real antigens–these are not the ones that get activated! Highly absorbent vaginal tampons predispose a woman to this infection.

Arthropod disease:

Genito-urinary infections

ADVANCE ORGANIZER Genito-urinary tract infections are either caused by opportunists that are part of the normal flora or by pathogens introduced from the outside. Many of these require direct human -to-human contact, thus they are often called STDs [sexually transmitted diseases].

READING Assignment CHAPTER 27

ADVANCE ORGANIZER
Genito-urinary tract infections are either caused by opportunists that are part of the normal flora or by pathogens introduced from the outside. Many of these require direct human -to-human contact, thus they are often called STDs [sexually transmitted diseases].