الفهرس 
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Abstract
Summary
An antimicrobial is an agent that kills microorganisms or
inhibits their growth. Antimicrobial medicines can be grouped
according to the microorganisms they act primarily against. For
example, antibacterials (commonly known as antibiotics) are used
against bacteria, antifungals are used against fungi and antivirals are
used against viruses. They can also be classed according to their
function. Antimicrobials that kill microbes are called microbicidal;
those that merely inhibit their growth are called microbiostatic.
Disinfectants such as bleach are non-selective antimicrobials.
Examples of antimicrobial agents: Tetracycline, an antibiotic
used to treat urinary tract infections, Oseltamivir, an antiviral that
treats the flu, and Terbinafine, an antifungal that treats athlete’s foot.
Antimicrobial therapy is probably overused in the ICU,
possibly resulting from difficulties in diagnosis and the perceived
greater risk of untreated infection when compared to the risks of
potentially unnecessary antimicrobial therapy. Efforts to improve
antimicrobial-related decision-making should be mandatory.
Selecting and initiating an antibiotic regimen:
An infectious disease diagnosis is reached by determining the
site of infection, defining the host (e.g.; immunocompromized,
diabetic, of advanced age), and establishing, when possible, a
microbiological diagnosis. It is critical to isolate the specific pathogen
in many serious, life-threatening infections, especially for situations
that are likely to require prolonged therapy (e.g.; endocarditis, septic
arthritis, disk space infection, and meningitis). Similarly, when a
patient does not benefit from antimicrobial therapy chosen on the
basis of clinical presentation, additional investigations are needed to
determine the etiologic agent or exclude noninfectious diagnoses.
Microbiologic resistance is said to occur when growth of the
infecting organism or pathogen is inhibited by an antimicrobial agent
concentration higher than the range seen for wild-type strains. Clinical
resistance is defined by the situation in which the infecting organism
is inhibited by a concentration of an antimicrobial agent that is
associated with a high likelihood of therapeutic failure. In other
words, the pathogen is inhibited by an antimicrobial concentration that
is higher than could be safely achieved with normal dosing.
By the composite definition, resistance is present when isolates
are not inhibited by the usually achievable concentrations of the agent
with normal dosage schedules and/or when they demonstrate MICs
(Minimum inhibitory concentrations) that fall in the range where
specific microbial resistance mechanisms are likely, and where
clinical efficacy against the isolate has not been reliably shown in
treatment studies.
Minimum inhibitory concentration (MIC) is the lowest
concentration of an antimicrobial that will inhibit the visible growth of
a microorganism after overnight incubation. A MIC is generally
regarded as the most basic laboratory measurement of the activity of
an antimicrobial agent against an organism.
Ventilator-associated pneumonia (VAP) is nosocomial
infection that develops following at least 48 h of mechanical
ventilation. It can be divided into the following two categories based
on duration of mechanical ventilation: early onset VAP (occurring on
days 2-4) and late onset VAP (occurring on days ≥ 5). A third
category is based on the risk of VAP being caused by multidrug
resistant pathogens, but occurring on days 2-4.
The incidence of VAP ranges from 9% to 27% and increases
with the duration of mechanical ventilation. It can increase duration of
mechanical ventilation by 5 days, length of ICU stay by 10 days,
hospitalization by 12 days. Interestingly, attributable mortality for
VAP varies depending on the patient population.
Sepsis is a clinical syndrome characterized by systemic
inflammation due to infection. There is a continuum of severity
ranging from sepsis to severe sepsis and septic shock. Even with
optimal treatment, mortality due to severe sepsis or septic shock is
approximately 40 percent and can exceed 50 percent in critically ill
patients.
According to the American College of Chest Physicians and
the Society of Critical Care Medicine, there are different levels of
sepsis:
● Systemic inflammatory response syndrome (SIRS) is the
presence of two or more of the following: abnormal body temperature,
heart rate, respiratory rate or blood gas, and white blood cell count.
● Sepsis is defined as SIRS in response to an infectious
process.
● Severe sepsis is defined as sepsis with sepsis-induced organ
dysfunction or tissue hypoperfusio (manifesting as hypotension,
elevated lactate, or decreased urine output).
● Septic shock is severe sepsis plus persistently low blood
pressure despite the administration of intravenous fluids.
Sepsis is caused by an immune response triggered by an
infection. The infection is most commonly by bacteria, but can also be
by fungi or viruses. Common locations for the primary infection
include: lungs, brain, urinary tract, skin, and abdominal organs. Risk
factors include young or old age, a weakened immune system from
conditions such as cancer or diabetes, and major trauma or burns.