Nosocomial infections epidemiology and key concepts
Nosocomial Infections Epidemiology and key concepts D-r Mitova MU-Sofia
Nosocomial infection: <ul><li>It is an infection acquired in a medical setting in the course of medical treatment. It meets the following criteria: </li></ul><ul><li>1 - Not found on admission </li></ul><ul><li>2 – Temporally associated with admission or a procedure at a health-care facility </li></ul><ul><li>3 – Was incubating at admission but related to a previous procedure or admission to same or other health-care facility. </li></ul>
Why Nosocomial infection ? <ul><li>It is an important public health problem because of their frequency, attributable morbidity and mortality and cost. In the USA and in Europe, approximately 5–10% of hospitalized patients develop an infection during their hospital stay. Higher incidence rates are reported in hospitals in developing countries. </li></ul><ul><li>In our hospital (National cancer Institute,), blood stream infections among pediatric patients accounted for 87.6/1000 discharges at 1999). Hospital acquired infection HAI contributed to 37.5% of these episodes. </li></ul>
Impact of nosocomial infection? <ul><li>Increased morbidity (serious consequences and permanent disability ) </li></ul><ul><li>The length of hospital stay is prolonged, on average by 5–10 days. </li></ul><ul><li>The risk of death approximately doubles in patients who acquire hospital infection. </li></ul><ul><li>Hospital-acquired infections are very expensive and contribute significantly to the escalating costs of health care. It has been argued that, even if moderately effective , a hospital infection control program is one of the most cost-effective and cost-beneficial preventative medical interventions currently available. </li></ul>
Definition of Nosocomial infection <ul><li>The use of uniform definition is crucial if data from one hospital are to be compared with those of another hospital (inter-hospital) or with an aggregated database (intra-hospital). </li></ul><ul><li>NI is a localized or systemic condition: </li></ul><ul><li>1- that results from adverse reaction to the presence of an infectiuos agent(s) or its toxins and </li></ul><ul><li>2- that was not present or incubating at the time of admission to the hospital. </li></ul><ul><li>For most bacterial NI, it become evident 48 hours or more (typical incubation period) after admission. Because the incubation period varies with type of pathogen, and extent of the underlying condition, each infection should be assessed individually for evidence that links it to hospitalization. </li></ul>
Specific situations of NI <ul><li>In superficial incisional surgical site infections (SSI) which involve only the skin or subcutaneuos tissues, it occurs within 30 days after the operation. </li></ul><ul><li>In deep incisional SSI which involves deep soft tissues (fascia and muscles) and organ/space SSI which involves anatomic structures not opened or manipulated during operation, in both conditions; it occurs 30 days of operation or within one year if an implant is present. </li></ul>
<ul><li>There are two special situations in which an infection is considered nosocomial : </li></ul><ul><li>a) Infection that is aquired in the hospital but does not become evident until after hospital discharge. </li></ul><ul><li>b) Infection in a neonate that results from passage through the birth canal. </li></ul><ul><li>There are two special situations in which an infection is not considered nosocomial : </li></ul><ul><li>Infection that is associated with a complication or extension of infection already present on admission, unless a change in pathogen or symptoms strongly suggests the acquisition of new infection. </li></ul><ul><li>In an infant, an infection that is known or proved to have been acquired transpalcentally (e.g congenital rubella, toxoplasmosis) and become evident at or before 48 hours after birth </li></ul>
There are two conditions that are not infections: <ul><li>1) Colonization , which is the presence of microorganisms (on skin, mucous membranes, in open wounds or in execretions or secretions) that are not causing clinical signs or symptoms. . </li></ul><ul><li>2) Inflammation , which is a condition that results from tissue response to injury or stimulation by noninfectious agnets such as chemicals. </li></ul>
Goals for infection control and hospital epidemiology <ul><li>There are three principal goals for hospital infection control and prevention programs: </li></ul><ul><li>Protect the patients </li></ul><ul><li>Protect the health care workers , visitors , and others in the healthcare environment. </li></ul><ul><li>Accomplish the previous two goals in a cost effective and cost efficient manner, whenever possible. </li></ul><ul><li>. </li></ul>
" An example of the most simple chain of infection is an infected patient cared for by a healthcare worker (HCW) who doesn't wash his or her hands before caring for another patient," says Richard Wenzel, MD, MSc, of the Department of Internal Medicine of Virginia Commonwealth University in Richmond, Va. Wenzel adds that contaminated hands are one of the most likely means of transmission of bacteria in hospitals.
Human sources of microorganisms are healthcare workers (HCWs), patients and visitors, any of whom may be individuals in the incubation period of a disease, those who already have a disease, or those who are considered to be chronic carriers of an infectious agent. Other sources of bacteria are the patient's endogenous (produced or originating from a cell or organism) flora and inanimate objects that have become contaminated
While there are five main routes of transmission of bacteria -- contact, droplet, airborne, common vehicle and vectorborne -- the first three routes are most critical to the discussion of nosocomial infections.
Infection control experts agree that following standard precautions, isolation guidelines when required and engaging in proper handwashing is essential to breaking the chain of infection. Following aseptic technique is especially critical when caring for patients with hardy microorganisms such as MRSA. A HCW can break the chain in the following way: Infectious agent : MRSA Reservoir : patient with MRSA in an open wound Portal of exit : drainage from the open wound; Break in the chain: HCW uses proper handwashing techniques, wears protective gloves and handles bed linens properly Mode of transmission : MRSA transferred on to hands by indirect contact; Break in the chain: HCW performs proper handwashing, gloving and linen handling Portal of entry : Break in the chain: Organisms isolated with use of medical asepsis and body-substance isolation Susceptible host : protected due to chain of infection being broken.