الفهرس 
EPIDIMIOLOGYOnly 14 pages are availabe for public view
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Abstract
Patients admitted with symptoms of infection prior to hospitalization are considered to have community-acquired infections, and those who develop infection more than 48 hours following admission are considered to have hospital-acquired, or nosocomial, infections.
The prevalence of nosocomial infections is higher in intensive care unit than other units in hospital . The length of ICU stay is the predominant risk factor for nosocomial infection followed by the use of medical devices. Other risk factors, some of which related to patient (severity of illness, chronic diseases, obesity, immunosupression, steroid) and other related to organisms
(virulence, resistance, formation of membrane) .
The prevalence of different types of NIs are varies from surgical and medical ICUs in same hospital, from hospital to another and from country to another.
The relative prevalences of the 4 most common nosocomial infections in intensive care units (ICUs) in the United States -- pneumonia, bloodstream infections, urinary tract infections (UTIs), and surgical site infections -- changed between 1975 and 2003. Pneumonia and bloodstream infections increased in prevalence by approximately 5%, while UTIs and surgical site infections (SSTIs) decreased by approximately 40% and 15%, respectively. The prevalences of pneumonia and bloodstream infection and SSTIs are similar in both medical ICU and surgical ICU patients although UTIs are notably more common in the medical (30%) than the surgical (18%) ICU.
The most common pathogens responsible for ICU infections are gram-positive organisms; coagulase-negative staphylococci (CoNS) were responsible for 42.9% of bloodstream infections, whereas S aureus was implicated in 27.8% of pneumonia cases. Methicillin-resistant S aureus (MRSA) and vancomycin-resistant enterococci have shown substantial increases in prevalence in both ICU and non-ICU hospital settings. gram-negative pathogen was P aeruginosa, which was associated with 18.1% of pneumonia cases, also K pneumoniae, Enterobacter spp. associated with occurrence of pneumonia in the ICU between 1986 and 2003 E.coli isolates are urine samples (32.1%)
Prevention plays a major role in the control of NIs. First, methods and techniques are needed to prevent cross-contamination and to control the potential sources of pathogens that could be transmitted from patient to patient or from Health Care Worker (HCW) to patient. These methods and techniques include appropriate protocols for cleaning, disinfecting, and caring for various pieces of equipment and devices. Second, guidelines are needed for the appropriate use of surgical antibiotic prophylaxis or empirical therapy among selected groups of patients. Third, strategies to limit the emergence of resistant microorganisms need to be developed.
Effective infection control programmes are usually based on the cooperation of the intensive care physician, the infectious disease specialist, the microbiologist and the clinical epidemiologist. The infectious disease specialist develops specific guidelines for the antimicrobial therapy of typical infections which minimize the selective pressure for microorganisms within the ICU. The microbiologist provides rapid and accurate diagnosis of the pathogens involved. The clinical epidemiologist identifies epidemics at early stages, using epidemiological tools and molecular typing methods, as well as summarizing trends of antimicrobial susceptibility patterns and setting standards for isolation practices. The intensive care physician is responsible for a simple and inexpensive way to reduce nosocomial infections in ICUs which is to ensure that staffs disinfect their hands after dealing with a patient. Also, ensuring that the use of intravascular devices, mechanical ventilation and urinary catheterization which are major risk factors for nosocomial infections should be evaluated daily and discontinued as soon as clinically possible and using selective decontamination of the digestive tract and the use of standard immunoglobulin for prophylaxis .
The challenge to the critical care specialist is to make the diagnosis early in the course of the disease to increase the likelihood of a successful outcome.
Seriously ill patients presenting with fever must be quickly evaluated for possible infection because most are treatable. In contrast, some patients may appear to be stable but nonetheless have serious infections. Elderly patients, uremic patients, and patients with end-stage liver disease or those receiving corticosteroids often will fail to mount a significant febrile response even to serious infection .
All appropriate microbiological specimens, including blood cultures, should be obtained before commencing antibiotic therapy. An immediate Gram-stained report may indicate the appropriate antibiotic to use; otherwise a ‘best-guess’ choice is made, which is dependent on the clinical situation.
Almost all infections could be controlled, but finding an effective antibiotic typically requires 2-3 days as bacterial cultures with extensive growth are needed to test antibiotic susceptibility and resistance. With critically ill patients in the ICU, the physicians cannot wait for lab results before attempting to control an infection, therefore antibiotic therapy is started within a few hours of symptoms onset in the form of antibiotic combinations. These empiric antibiotic combinations fail in approximately 20- 40% of cases and even switching drugs after receiving lab results fails to improve the outcome.
Antibiotic resistance is occurring more rapidly and more frequently all over the world, with Gram negative bacilli and Gram-positive bacteria being important causes of hospital-acquired infections affecting patient outcomes. Therefore, avoiding unnecessary antibiotic use and optimizing the administration of antimicrobial agents will help to improve patient outcomes while minimizing further pressures for resistance.
Clinicians practicing in intensive care units must develop and promote strategies for more effectively employing antimicrobial therapy. The most successful strategies will be multidisciplinary, involving cooperation from the pharmacist, infection control individuels, nursing staff, treating physicians, and infectious disease consultants. Such programmes should also focus both on promoting infection control practices and employing rational antibiotic utilization aimed at minimizing future emergence of resistance such as restriction of prescription, combining antibiotic therapy, de-escalation strategy and rotating antibiotics.