Nosocomial infection

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

A nosocomial infection is an infection whose development is favoured by a hospital environment, such as one acquired by a patient during a hospital visit or one developing among hospital staff. Such infections include fungal and bacterial infections and are aggravated by the reduced resistance of individual patients.^[1]

In the United States, the Centers for Disease Control and Prevention estimated roughly 1.7 million hospital-associated infections, from all types of microorganisms, including bacteria, combined, cause or contribute to 99,000 deaths each year. In Europe, where hospital surveys have been conducted, the category of Gram-negative infections are estimated to account for two-thirds of the 25,000 deaths each year. Nosocomial infections can cause severe pneumonia and infections of theurinary tract, bloodstream and other parts of the body. Many types are difficult to attack with antibiotics, and antibiotic resistance is spreading to Gram-negative bacteria that can infect people outside the hospital.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

The drug-resistant Gram-negative bacteria, for the most part, threaten only hospitalized patients whose immune systems are weak. They can survive for a long time on surfaces in the hospital and enter the body through wounds, catheters, and ventilators.

Contact transmission is divided into two subgroups: direct-contact transmission and indirect-contact transmission.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

• Acinetobacter baumannii
• Candida albicans
• Clostridium difficile
• Gastroenteritis
• Hospital-acquired pneumonia
• Legionnaires’ disease
• Methicillin resistant Staphylococcus aureus
• Pseudomonas aeruginosa
• Staphylococcus aureus
• Stenotrophomonas maltophilia
• Tuberculosis
• Urinary tract infection
• Vancomycin-resistant enterococcus
• Ventilator-associated pneumonia

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Nosocomial infections are commonly transmitted when hospital officials become complacent and personnel do not practice correct hygiene regularly. Also, increased use of outpatient treatment in recent decades means that a greater percentage of people who are hospitalized today are likely to be seriously ill with more weakened immune systems than in the past. Moreover, some medical procedures bypass the body’s natural protective barriers. Since medical staff move from patient to patient, the staff themselves serve as a means for spreading pathogens. Essentially, the staff act as vectors. The methods used differ from country to country (definitions used, type of nosocomial infections covered, health units surveyed, inclusion or exclusion of imported infections, etc.), so the international comparisons of nosocomial infection rates should be made with the utmost care. One-third of nosocomial infections are considered preventable. The CDC estimates 2 million people in the United States are infected annually by hospital-acquired infections, resulting in 20,000 deaths.^[1] The most common nosocomial infections are of the urinary tract, surgical site, and various pneumonias.^[2]

The Centers for Disease Control and Prevention (CDC) estimated roughly 1.7 million hospital-associated infections, from all types of bacteria combined, cause or contribute to 99,000 deaths each year.^[3] Other estimates indicate 10%, or 2 million, patients a year become infected, with the annual cost ranging from $4.5 billion to $11 billion. In the USA, the most frequent type of infection hospitalwide is urinary tract infection (36%), followed by surgical site infection (20%), and bloodstream infection and pneumonia (both 11%).

Estimates ranged from 6.7% in 1990 to 7.4% (patients may have several infections).^[4] At national level, prevalence among patients in health care facilities was 6.7% in 1996,^[5] 5.9% in 2001^[6] and 5.0% in 2006.^[7] The rates for nosocomial infections were 7.6% in 1996, 6.4% in 2001 and 5.4% in 2006. In 2006, the most common infection sites were urinary tract infections (30,3%), pneumopathy (14,7%), infections of surgery site (14,2%). Infections of the skin andmucous membrane (10,2%), other respiratory infections (6,8%) and bacterial infections / blood poisoning (6,4%).^[8] The rates among adult patients in intensive care were 13,5% in 2004, 14,6% in 2005, 14,1% in 2006 and 14.4% in 2007.^[9] Nosocomial infections are estimated to make patients stay in the hospital four to five additional days. Around 2004-2005, about 9,000 people died each year with a nosocomial infection, of which about 4,200 would have survived without this infection.^[10]

Since 2000, estimates show about a 6.7% infection rate, i.e. between 450,000 and 700,000 patients, which caused between 4,500 and7,000 deaths.^[11] A survey in Lombardy gave a rate of 4.9% of patients in 2000.^[12]

Estimates show a 10% infection rate,^[13] with 8.2% estimated in 2006.^[14]

Estimates range between 2 and 14%.^[15] A national survey gave a rate of 7.2% in 2004.^[16]

Rate were estimated at 8.5% of patients in 2005.^[17]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Factors predisposing a patient to infection can broadly be divided into three areas:

• People in hospitals are usually already in a ‘poor state of health’, impairing their defense against bacteria – advanced age or premature birth along withimmunodeficiency (due to drugs, illness, or irradiation) present a general risk, while other diseases can present specific risks – for instance, chronic obstructive pulmonary disease can increase chances of respiratory tract infection.
• Invasive devices, for instance intubation tubes, catheters, surgical drains, and tracheostomy tubes, all bypass the body’s natural lines of defence againstpathogens and provide an easy route for infection. Patients already colonised on admission are instantly put at greater risk when they undergo invasive procedures.
• Patients’ treatments can leave them vulnerable to infection – immunosuppression and antacid treatment undermine the body’s defences, while antimicrobial therapy (removing competitive flora and only leaving resistant organisms) and recurrent blood transfusions have also been identified as risk factors.

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