Proteus Infections

					17/08/2013                                                  Proteus Infections

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  Proteus Infections
             Author: Kelley Struble, DO; Chief Editor: Burke A Cunha, MD more...

  Updated: Mar 25, 2013

  Background
  Proteus species are part of the Enterobacteriaceae family of gram-negative bacilli. Proteus organisms are
  implicated as serious causes of infections in humans, along with Escherichia, Klebsiella, Enterobacter, and
  Serratia species.

  Proteus species are most commonly found in the human intestinal tract as part of normal human intestinal flora,
  along with Escherichia coli and Klebsiella species, of which E coli is the predominant resident. Proteus is also
  found in multiple environmental habitats, including long-term care facilities and hospitals. In hospital settings, it is
  not unusual for gram-negative bacilli to colonize both the skin and oral mucosa of both patients and hospital
  personnel. Infection primarily occurs from these reservoirs. However, Proteus species are not the most common
  cause of nosocomial infections.

  Proteus mirabilis causes 90% of Proteus infections and can be considered a community-acquired infection.
  Proteus vulgaris and Proteus penneri are easily isolated from individuals in long-term care facilities and hospitals
  and from patients with underlying diseases or compromised immune systems.

  Patients with recurrent infections, those with structural abnormalities of the urinary tract, those who have had
  urethral instrumentation, and those whose infections were acquired in the hospital have an increased frequency of
  infection caused by Proteus and other organisms (eg, Klebsiella, Enterobacter, Pseudomonas,enterococci,
  staphylococci).

  Pathophysiology
  Proteus species possess an extracytoplasmic outer membrane, a feature shared with other gram-negative
  bacteria. In addition, the outer membrane contains a lipid bilayer, lipoproteins, polysaccharides, and
  lipopolysaccharides.

  Infection depends on the interaction between the infecting organism and the host defense mechanisms. Various
  components of the membrane interplay with the host to determine virulence. Inoculum size is important and has a
  positive correlation with the risk of infection.

  Certain virulence factors have been identified in bacteria. The first step in the infectious process is adherence of
  the microbe to host tissue. Fimbriae facilitate adherence and thus enhance the capacity of the organism to
  produce disease. E coli, P mirabilis, and other gram-negative bacteria contain fimbriae (ie, pili), which are tiny
  projections on the surface of the bacterium. Specific chemicals located on the tips of pili enable organisms to
  attach to selected host tissue sites (eg, urinary tract endothelium). The presence of these fimbriae has been

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  demonstrated to be important for the attachment of P mirabilis to host tissue.

  The attachment of Proteus species to uroepithelial cells initiates several events in the mucosal endothelial cells,
  including secretion of interleukin 6 and interleukin 8. Proteus organisms also induce apoptosis and epithelial cell
  desquamation. Bacterial production of urease has also been shown to increase the risk of pyelonephritis in
  experimental animals. Urease production, together with the presence of bacterial motility and fimbriae, may favor
  the production of upper urinary tract infections (UTIs) by organisms such as Proteus.

  Enterobacteriaceae (of which Proteus is a member) and Pseudomonas species are the microorganisms most
  commonly responsible for gram-negative bacteremia. When these organisms invade the bloodstream, endotoxin, a
  component of gram-negative bacterial cell walls, apparently triggers a cascade of host inflammatory responses
  and leads to major detrimental effects. Because Proteus and Pseudomonas organisms are gram-negative bacilli,
  they can cause gram-negative endotoxin-induced sepsis, resulting in systemic inflammatory response syndrome
  (SIRS), which carries a mortality rate of 20%-50%.

  Although other organisms can trigger a similar response, it is useful to consider gram-negative bacteremia as a
  distinct entity because of its characteristic epidemiology, pathogenesis, pathophysiology, and treatment. The
  presence of the sepsis syndrome associated with a UTI should raise the possibility of urinary tract obstruction.
  This is especially true of patients who reside in long-term care facilities, who have long-term indwelling urethral
  catheters, or who have a known history of urethral anatomic abnormalities.

  The ability of Proteus organisms to produce urease and to alkalinize the urine by hydrolyzing urea to ammonia
  makes it effective in producing an environment in which it can survive. This leads to precipitation of organic and
  inorganic compounds, which leads to struvite stone formation. Struvite stones are composed of a combination of
  magnesium ammonium phosphate (struvite) and calcium carbonate-apatite.

  Struvite stone formation can be sustained only when ammonia production is increased and the urine pH is elevated
  to decrease the solubility of phosphate. Both of these requirements can occur only when urine is infected with a
  urease-producing organism such as Proteus. Urease metabolizes urea into ammonia and carbon dioxide: Urea →
  2NH3 + CO2. The ammonia/ammonium buffer pair has a pK of 9.0, resulting in the combination of highly alkaline
  urine rich in ammonia.

  Symptoms attributable to struvite stones are uncommon. More often, women present with UTI, flank pain, or
  hematuria and are found to have a persistently alkaline urine pH (>7.0).

  Epidemiology
  Frequency

  United States

  The genitourinary tract is the site of disease responsible for gram-negative bacteremia in approximately 35% of
  patients. In previously healthy outpatients, E coli is by far the most often implicated cause of UTIs. In contrast,
  individuals with multiple prior episodes of UTI, multiple antibiotic treatments, urinary tract obstruction, or infection
  developing after instrumentation frequently become infected with Proteus bacteria or other bacteria such as
  Enterobacter, Klebsiella, Serratia, and Acinetobacter.

  Bacteriuria occurs in 10%-15% of hospitalized patients with indwelling catheters. The risk of infection is 3%-5%
  per day of catheterization.

  Mortality/Morbidity

  Among long-term care residents, UTIs are the second most common infection responsible for hospital admission,
  second only to pneumonia. UTIs can result in sepsis if not recognized and treated rapidly. Failure to treat or a
  delay in treatment can result in SIRS, which carries a mortality rate of 20%-50%.

  Sex

  Other factors that increase infection rates include female sex, duration of catheterization, underlying illness, faulty
  catheter care, and lack of systemic antibiotic therapy. Infection occurs either by migration of bacteria up the
  catheter along the mucosal sheath or by migration up the catheter lumen from infected urine.

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17/08/2013                                                 Proteus Infections

             UTIs are the most common clinical manifestation of Proteus infections. Proteus infection accounts for
             1%-2% of UTIs in healthy women and 5% of hospital-acquired UTIs. Complicated UTIs (ie, those associated
             with catheterization) have a prevalence of 20%-45%.
             UTIs are more common in males then females in the neonatal population. This is a result of congenital
             abnormalities seen more often in males.
             After age 50 years, the ratio between men and women begins to decline because of the increasing
             incidence of prostate disease. UTIs in men younger than 50 years are usually caused by urologic
             abnormalities.

  Age

  UTIs are more common in persons aged 20-50 years.

    Contributor Information and Disclosures
    Author
    Kelley Struble, DO Fellow, Department of Infectious Diseases, University of Oklahoma College of Medicine

    Kelley Struble, DO is a member of the following medical societies: American College of Physicians and
    Infectious Diseases Society of America

    Disclosure: Nothing to disclose.

    Coauthor(s)
    Michael Stuart Bronze, MD David Ross Boyd Professor and Chairman, Department of Medicine, Stewart G
    Wolf Endowed Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science
    Center

    Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American
    College of Physicians, American Medical Association, Association of Professors of Medicine, Infectious
    Diseases Society of America, Oklahoma State Medical Association, and Southern Society for Clinical
    Investigation

    Disclosure: Nothing to disclose.

    Rhett L Jackson, MD Associate Professor and Vice Chair for Education, Department of Medicine, Director,
    Internal Medicine Residency Program, University of Oklahoma College of Medicine; Assistant Chief, Medicine
    Service, Oklahoma City Veterans Affairs Hospital

    Rhett L Jackson, MD is a member of the following medical societies: American College of Physicians-American
    Society of Internal Medicine and American Medical Association

    Disclosure: Nothing to disclose.

    Gus Gonzalez, MD Medical Oncologist, The Center for Cancer and Blood Disorders

    Gus Gonzalez, MD is a member of the following medical societies: American College of Physicians-American
    Society of Internal Medicine

    Disclosure: Nothing to disclose.

    Specialty Editor Board
    Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center
    College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

    Disclosure: Medscape Salary Employment

    Aaron Glatt, MD Chief Administrative Officer, Executive Vice President, Mercy Medical Center, Catholic
    Health Services of Long Island

    Aaron Glatt, MD is a member of the following medical societies: American College of Chest Physicians,
    American College of Physician Executives, American College of Physicians, American College of Physicians-
    American Society of Internal Medicine, American Medical Association, American Society for Microbiology,
emedicine.medscape.com/article/226434-overview#showall                                                             3/5
17/08/2013                                                  Proteus Infections

    American Thoracic Society, American Venereal Disease Association, Infectious Diseases Society of America,
    International AIDS Society, and Society for Healthcare Epidemiology of America

    Disclosure: Nothing to disclose.

    Chief Editor
    Burke A Cunha, MD Professor of Medicine, State University of New York School of Medicine at Stony Brook;
    Chief, Infectious Disease Division, Winthrop-University Hospital

    Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians,
    American College of Physicians, and Infectious Diseases Society of America

    Disclosure: Nothing to disclose.


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emedicine.medscape.com/article/226434-overview#showall                                                              5/5

				
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