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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.

Micrograph showing  oddly (roughly round) shaped structures.
Ureaplasma urealyticum microcolonies (white arrows) on agar surface after anaerobic incubation, visualized using phase contrast microscopy (800×). The black arrow indicates cellular debris. (credit: modification of work by American Society for Microbiology)
  • What are the three most common causes of urethritis?
  • What three members of the normal microbiota can cause urethritis?

Bacterial infections of the urinary tract

Urinary tract infections can cause inflammation of the urethra (urethritis), bladder (cystitis), and kidneys (pyelonephritis), and can sometimes spread to other body systems through the bloodstream. [link] captures the most important features of various types of UTIs.

Table titled: Bacterial Infections of the Urinary Tract. Columns: Disease, Pathogen, Signs and Symptoms, Transmission, Diagnostic Tests, Antimicrobial Drugs. Disease - Cystitis; Escherichia coli, Enterococcus faecalis, Streptococcus agalactiae, Klebsiella pneumoniae, Staphylococcus saprophyticus, others; Dysuria, pyuria, hematuria, and bladder pain; most common in females due to the shorter urethra and abundant normal vaginal microbiota; Nontransmissible; opportunistic infections occur when fecal bacteria are introduced to urinary tract or when normal urination or immune function is impaired; Urine dipstick, urine culture for confirmation; Fluoroquinolones, nitrofurantoin, cephalosporins, trimethoprim, sulfamethoxazole. Disease - Leptospirosis; Leptospira spp.; Fever, headache, chills, vomiting, diarrhea, rash, muscular pain; in disseminated infections, may cause jaundice, pulmonary hemorrhaging, meningitis; From animals to humans via contact with urine or body fluids; PCR, ELISA, slide agglutination, indirect immunofluorescence; Doxycycline, amoxicillin, ampicillin, erythromycin, penicillin. Disease - Nongonococcal urethritis (NGU); Chlamydia trachomatis, Mycoplasma genitalium, Mycoplasma hominis, Ureaplasma urealyticum; Mild or asymptomatic; may cause purulent discharge and dysuria Transmitted sexually or from mother to neonate during birth; Urethral swabs and urine culture, PCR, NAAT; Azithromycin, doxycycline, erythromycin, fluoroquinolones. Disease Pyelonephritis, glomerulonephritis; E. coli, Proteus spp., Klebsiella spp., Streptococcus pyogenes, others; Back pain, fever, nausea, vomiting, blood in urine; possible scarring of the kidneys and impaired kidney function; severe infections may lead to sepsis and death; Nontransmissible; infection spreads to kidneys from urinary tract or through bloodstream; Urinalysis, urine culture, radioimaging of kidneys; Penicillins, cephalosporins, fluoroquinolones, aminoglycosides, others

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.

Fill in the blank

Pyelonephritis is a potentially severe infection of the _____.

kidneys

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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