Infections have been the major cause of disease throughout the history of human population. With the introduction of antibiotics, it was thought that this problem should disappear. However, bacteria have been able to resist the action of antibiotics. Resistance to antibiotics is a major obstacle in the treatment of infectious diseases, leading to treatment failure and increased treatments' costs.
Bacterial resistance to antibiotics is subdivided into two categories, innate and acquired. Innate resistance is attributed to physiological factors inherently present in the bacteria rendering it immune to certain antibiotics.
Acquired resistance is driven by two genetic processes in bacteria:
• Mutation and selection (sometimes referred to as vertical evolution);
• Exchange of genes between strains and species (sometimes called horizontal evolution). Some bacterial species are able to spread drug resistance to other strains and species during genetic exchange processes.
A number of resistance genes have been associated with large plasmids, on which many other mobile elements; as transposons and integrons are present.
These DNA mobile elements have been shown to possess genetic determinants for several different antibiotic resistance mechanisms and are largely responsible for the rapid dissemination of resistance genes among different bacterial genera and species.
Bacterial resistance to antibiotics is manifested by changes in antibiotic permeability, alteration of target molecules, enzymatic degradation of the antibiotics, and efflux of antimicrobials from the cytoplasm. Bacteria use all of these mechanisms to evade the toxic effects of antibiotics.
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.
The burden of HAIs increased during the past decade due to the increase in immuno-comprimised patients in hospitals, the development of more delicate life support treatments, advanced surgical operations, increasing numbers of elderly patients, more complex hospital environments, and failures in infection control measures.
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 cause of this problem is multifactorial, including selective pressure that results from inappropriate use of antibiotics, Poor hand hygiene by hospital staff and poor quality infection control in the belief that infection has been beaten by antibiotics.
The number of antibiotics belonging to various families, their various modes of action and the number of bacteria in which antibiotic resistance has been documented suggest that, in principle, any microbe could develop resistance to any antibiotic.
Antibiotic resistance is found among essentially all the major bacterial pathogens, and the emergence of multi-resistant ‘super bugs’ within hospitals now poses a very real and formidable threat.
Determining the antimicrobial susceptibility profile of a pathogen is considered as important as the identification of the pathogen involved in the infection. This is becoming more essential in an era of increasing antimicrobial resistance, in which treatment options are limited to newer, more costly antimicrobial agents.
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.
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