الفهرس 
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Abstract
HAIs are the most frequent and widely studied adverse effect of hospitalization. They have emerged as an important public health problem and are a leading cause of morbidity and mortality in both developed and developing countries. HAIs results in unnecessary human suffering and death as well as health care expenditures. They can affect any part of the body, but respiratory tract infections, central line infections, urinary tract infections, and wound infections are the most common sites. In addition to their association with increased morbidity and mortality, HAIs are frequently caused by drug resistant micro-organisms, including MRSA, VRE, and ESBL-producing gram negative bacteria, which pose considerable therapeutic problems. The main mechanisms by which the bacteria resist the antibiotic action in HAIs include: enzymes that modify the drug, antibiotic resistance due to target alteration, and antibiotic efflux pumps. The genetic bases underlying these mechanisms of resistance include either mutation and selection or acquisition of external genes. Acquisition of genes is greatly aided by MGEs that move genes from one DNA system to another and from one bacterial cell to another. Bacterial plasmids serve as the scaffold on which arrays of antibiotic resistance genes are assembled. Determining the antimicrobial susceptibility profile of a pathogen is considered as important as the identification of the pathogen involved in the infection. Susceptibility testing in most clinical microbiology laboratories represents a combination of phenotypic assays and molecular-based tests. Phenotypic assays provide either qualitative results (susceptible, intermediate, or resistant) for a series of antimicrobial agents, or quantitative results (MICs) that can guide dosing regimens. Molecular-based tests, such as real-time PCR, may provide rapid information on the presence of MRSA or VRE in patients, which will assist in infection control decisions. Hospital infection control programs are seen as very important for the control of antibiotic-resistant organisms. Other considerations for an infection control program include antibiotic control programs and surveillance systems for infections with nosocomial pathogens. This type of surveillance is essential for establishing endemic rates.