23.2 Bacterial infections of the urinary system  (Page 5/8)

M. genitalium is a more common cause of urethritis in most settings than N. gonorrhoeae , although it is less common than C. trachomatis . It is responsible for approximately 30% of recurrent or persistent infections, 20–25% of nonchlamydial NGU cases, and 15%–20% of NGU cases. M. genitalium attaches to epithelial cells and has substantial antigenic variation that helps it evade host immune responses. It has lipid-associated membrane proteins that are involved in causing inflammation.

Several possible virulence factors have been implicated in the pathogenesis of U. urealyticum ( [link] ). These include the ureaplasma proteins phospholipase A , phospholipase C , multiple banded antigen (MBA), urease , and immunoglobulin α protease . The phospholipases are virulence factors that damage the cytoplasmic membrane of target cells. The immunoglobulin α protease is an important defense against antibodies. It can generate hydrogen peroxide, which may adversely affect host cell membranes through the production of reactive oxygen species.

Treatments differ for gonorrheal and nongonococcal urethritis. However, N. gonorrhoeae and C. trachomatis are often simultaneously present, which is an important consideration for treatment. NGU is most commonly treated using tetracyclines (such as doxycycline ) and azithromycin ; erythromycin is an alternative option. Tetracyclines and fluoroquinolones are most commonly used to treat U. urealyticum , but resistance to tetracyclines is becoming an increasing problem. Ken B Waites. “Ureaplasma Infection Medication.” Medscape , 2015. http://emedicine.medscape.com/article/231470-medication. While tetracyclines have been the treatment of choice for M. hominis , increasing resistance means that other options must be used. Clindamycin and fluoroquinolones are alternatives. M. genitalium is generally susceptible to doxycycline, azithromycin, and moxifloxacin . Like other mycoplasma, M. genitalium does not have a cell wall and therefore β-lactams (including penicillins and cephalosporins) are not effective treatments.

Key concepts and summary

• Bacterial cystitis is commonly caused by fecal bacteria such as E. coli.
• Pyelonephritis is a serious kidney infection that is often caused by bacteria that travel from infections elsewhere in the urinary tract and may cause systemic complications.
• Leptospirosis is a bacterial infection of the kidney that can be transmitted by exposure to infected animal urine, especially in contaminated water. It is more common in tropical than in temperate climates.
• Nongonococcal urethritis (NGU) is commonly caused by C. trachomatis, M. genitalium, Ureaplasma urealyticum, and M. hominis.
• Diagnosis and treatment for bacterial urinary tract infections varies. Urinalysis (e.g., for leukocyte esterase levels, nitrite levels, microscopic evaluation, and culture of urine) is an important component in most cases. Broad-spectrum antibiotics are typically used.

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