eMedicine Specialties > Pediatrics: General Medicine > Infectious Disease

Hospital-Acquired Infections

Author: Quoc V Nguyen, MD, Assistant Professor, Department of Pediatrics, New York State Health Department
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Updated: Jan 14, 2009

Introduction

Background

Hospital-acquired infections (HAIs), also known as health-care–associated infections, encompass almost all clinically evident infections that do not originate from a patient's original admitting diagnosis. Within hours after admission, a patient's flora begins to acquire characteristics of the surrounding bacterial pool. Most infections that become clinically evident after 48 hours of hospitalization are considered hospital-acquired. Infections that occur after the patient's discharge from the hospital can be considered to have a nosocomial origin if the organisms were acquired during the hospital stay.

Pathophysiology

Within hours of admission, colonies of hospital strains of bacteria develop in the patient's skin, respiratory tract, and genitourinary tract. Risks factors for the invasion of colonizing pathogens can be categorized into 3 areas: iatrogenic, organizational, and patient-related.

• Iatrogenic risk factors include pathogens on the hands of medical personnel, invasive procedures (eg, intubation and extended ventilation, indwelling vascular lines, urine catheterization), and antibiotic use and prophylaxis.
• Organizational risk factors include contaminated air-conditioning systems, contaminated water systems, and staffing and physical layout of the facility (eg, nurse-to-patient ratio, open beds close together).
• Patient risk factors include the severity of illness, underlying immunocompromised state, and length of stay.

Frequency

United States

The National Nosocomial Infections Surveillance (NNIS) System of the Centers for Disease Control and Prevention (CDC) performed a survey from October 1986 to April 1998.¹ They ranked hospital wards according to their association with central-line bloodstream infections. The highest rates of infection occurred in the burn ICU, the neonatal ICU, and the pediatric ICU.

Nosocomial infections are estimated to occur in 5% of all acute-care hospitalizations; the incidence rate is 5 infections per 1,000 patient-days. Based on the 35 million patients admitted to 7,000 acute-care institutions in the United States, the incidence of HAIs is more than 2 million cases per year.² HAIs result in an additional 26,250 deaths (range 17,500-70,000) and an added expenditure in excess of $4.5 billion.

International

The impact of HAIs on the health care systems of developed countries is significant and is proportionate to that of the United States.

Mortality/Morbidity

Nosocomial infections are estimated to more than double the mortality and morbidity risks of any admitted patient and probably result in as many as 70,000 deaths per year in the United States. This is the equivalent of 350,000 years of life lost in the United States.

Sex

HAIs do not have a discernible sex predilection. However, in the neonatal period, low birth weight and male sex (male-to-female ratio is 1.7:1) are associated with an increased risk of HAIs.

Age

Among bacterial HAIs, bacteremias and surgical site infections were more common in infants younger than 2 months than in older children. However, urinary tract infections (UTIs) were reported more frequently in children older than 5 years than in younger children.

Clinical

History

• Nosocomial infections are caused by viral, bacterial, and fungal pathogens. These pathogens should be investigated in all febrile patients who are admitted for a nonfebrile illness.
• During their hospital stay, many patients acquire viral respiratory infections (eg, influenza, parainfluenza, respiratory syncytial viruses) in the winter, rotaviral infections in winter, and enteroviral infections in the summer. Viruses are the leading etiologies of nosocomial infections in pediatric patients (responsible for ≤14% of hospital-acquired infections [HAIs] with identifiable pathogens).
• Bacterial and fungal infections are less common. However, they are significantly associated with more morbidity and mortality. Most patients who are infected with nosocomial bacterial and fungal pathogens have a predisposition to infection caused by invasive supportive measures such as intubation and the placement of intravascular lines and urinary catheters. Fungal infections are more likely to arise from the patient's own flora; occasionally, they are caused by contaminated solutions (eg, those used in parenteral nutrition).

Physical

In addition to the presence of systemic signs and symptoms of infection (eg, fever, tachycardia, tachypnea, skin rash, general malaise), the source of HAIs may be suggested by the instrumentation used in various procedures. For example, an endotracheal tube may be associated with sinusitis, otitis, tracheitis and pneumonia; an intravascular catheter may be the source of phlebitis or line infection; and a Foley catheter may be associated with a candidal UTI.

Causes

• Among 6,290 pediatric ICU patients surveyed between 1992 and 1997, the incidence of nosocomial invasive bacterial and fungal infections were as follows:³
  • Bloodstream infections - 28%
  • Ventilator-associated pneumonia - 21%
  • Urinary tract infection (UTI) - 15%
  • Lower respiratory infection - 12%
  • Gastrointestinal, skin, soft tissue, and cardiovascular infections - 10%
  • Surgical-site infections - 7%
  • Ear, nose, and throat infections - 7%
• Nosocomial etiologies in bloodstream infections
  • Coagulase-negative staphylococci - 40%
  • Enterococci - 11.2%
  • Fungi - 9.65%
  • Staphylococcus aureus - 9.3%
  • Enterobacter species - 6.2%
  • Pseudomonads - 4.9%
  • Acinetobacter baumannii with substantial antimicrobial resistance - Reported with increasing frequency
• Nosocomial etiologies in UTI
  • Gram-negative enterics - 50%
  • Fungi - 25%
  • Enterococci - 10%
• Nosocomial etiologies in surgical-site infections
  • S aureus - 20%
  • Pseudomonads - 16%
  • Coagulase-negative staphylococci - 15%
  • Enterococci, fungi, Enterobacter species, and Escherichia coli - Less than 10% each
• Nosocomial etiologies in fever
  • Viral infections are most common causes of nosocomial fevers.
  • Phlebitis is the second most common cause of nosocomial fevers in the hospitalized child.
  • Clostridium difficile colitis is also a cause of nonsocomial fevers.

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