Hospital-Acquired Infections

Updated: Oct 21, 2021
  • Author: Haidee T Custodio, MD; Chief Editor: Russell W Steele, MD  more...
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Practice Essentials

Hospital-acquired infections are caused by viral, bacterial, and fungal pathogens; the most common types are bloodstream infection (BSI), pneumonia (eg, ventilator-associated pneumonia [VAP]), urinary tract infection (UTI), and surgical site infection (SSI).

Risk factors for catheter-associated BSI in neonates include the following [1] :

  • Catheter hub or exit-site colonization

  • Catheter insertion after the first week of life

  • Duration of parenteral nutrition

  • Extremely low birth weight (< 1000 g) at catheter insertion

  • In the pediatric ICU, neutropenia, prolonged catheter dwell time (>7 days), percutaneously placed central venous lines, and frequent manipulation of lines have been identified as risk factors for catheter-associated BSI [2]

Risk factors for candidemia in neonates include the following [3] :

  • Gestational age of less than 32 weeks

  • 5-minute Apgar scores below 5

  • Shock, disseminated intravascular coagulation

  • Prior intralipid use

  • Parenteral nutrition, central venous line placement

  • H2 blocker administration

  • Intubation

  • Hospital stay longer than 7 days

Risk factors for VAP in pediatric patients include the following [4, 5] :

  • Reintubation

  • Genetic syndromes

  • Immunodeficiency, immunosuppression

  • Prior BSI [6]

Risk factors for hospital-acquired UTI in pediatric patients include the following [7] :

  • Bladder catheterization

  • Prior antibiotic therapy

  • Cerebral palsy

The source of infection may be suggested by the instrumentation, as follows:

  • Endotracheal tube: Sinusitis, tracheitis, pneumonia

  • Intravascular catheter: Phlebitis, line infection

  • Foley catheter: UTI

Patients with pneumonia may have the following:

  • Fever, cough, purulent sputum

  • Abnormal chest auscultatory findings (eg, decreased breath sounds, crackles, wheezes)

Patients with UTI may have the following:

  • Fever or normal temperature

  • Tenderness, suprapubic (cystitis) or costovertebral (pyelonephritis)

  • Cloudy, foul-smelling urine

See Clinical Presentation for more detail.


Because not all bacterial or fungal growth on a culture is pathogenic and because such growth may reflect simple microbial colonization, interpretation of cultures should take into account the following:

  • Clinical presentation of the patient

  • Reason for obtaining the test

  • Process by which the specimen was obtained

  • Presence or absence of other supporting evidence of infection

Methods used to diagnose and characterize BSIs include the following:

  • Suspected catheter-associated BSI: Differential time to positivity of paired blood cultures (simplest) [8] ; quantitative culture of blood obtained from the catheter and peripheral vein; quantitative culture of catheter segment

  • Suspected fungal infection: Fungal cultures, detection of (1,3)-β-D-glucan and galactomannan

  • Possible thrombosis or vegetations: Imaging studies such as echocardiography

  • Immunocompromised patients: Occasional special studies (eg, cultures for Nocardia, atypical mycobacteria, cytomegalovirus [CMV], and CMV antigenemia)

Tests used to identify pneumonia include the following:

  • Acute-phase reactants

  • Oxygen saturation and hemodynamic studies

  • Chest radiography

  • Sputum Gram stain and culture (if necessary, samples can also be obtained through bronchoalveolar lavage or thoracocentesis)

  • Rapid diagnostic tests (eg multiplex PCR capable of identifying multiple pathogens in a specimen)

Urinalysis and urine culture, along with clinical findings, are essential for differentiating between asymptomatic bacteriuria, cystitis, and pyelonephritis. The following factors should be kept in mind in the interpretation of urine cultures:

  • Number of colonies and species isolated

  • Method of sample collection

  • Time from collection to laboratory processing

  • Sex of the patient

  • Previous antibiotic use

Most experts recommend imaging studies in evaluating children with first-time UTI.

See Workup for more detail.


Medical care includes supportive care addressing shock, hypoventilation, and other complications, along with empiric broad-spectrum antimicrobial therapy.

Management of BSI may include the following:

  • Line removal as appropriate [8]

  • Antibiotic therapy covering gram-positive and gram-negative organisms, started empirically and then tailored according to specific susceptibility patterns

  • Antifungal therapy as appropriate

  • Antiviral therapy as appropriate

  • Prevention through use of catheter disinfection caps

Management of pneumonia includes the following:

  • Initial empiric broad-spectrum antibiotic therapy, later streamlined on the basis of identified organisms and susceptibilities, with attention to the risk of multidrug-resistant (MDR) pathogens

  • Antiviral medications against influenza for symptomatic patients and patients with immunodeficiency or chronic lung diseases to limit morbidity and mortality

Management of UTI includes the following:

  • Removal of indwelling catheters if possible

  • Empiric antibiotic and antifungal therapy

Management of SSI includes the following:

  • Surgical debridement

  • Antibiotic therapy

See Treatment and Medication for more detail.



Healthcare-associated infections (HAI) are defined as infections not present and without evidence of incubation at the time of admission to a healthcare setting. As a better reflection of the diverse healthcare settings currently available to patients, the term healthcare-associated infections replaced old ones such as nosocomial, hospital-acquired or hospital-onset infections. [9] 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 is discharged from the hospital can be considered healthcare-associated if the organisms were acquired during the hospital stay.

Hospital-based programs of surveillance, prevention and control of healthcare-associated infections have been in place since the 1950s. [10] The Study on the Efficacy of Nosocomial Infection Control Project (SENIC) from the 1970s showed nosocomial rates could be reduced by 32% if infection surveillance were coupled with appropriate infection control programs. [11] In 2005, the National Healthcare Safety Network (NHSN) was established with the purpose of integrating and succeeding previous surveillance systems at the Centers for Disease Control and Prevention (CDC): National Nosocomial Infections Surveillance (NNIS), Dialysis Surveillance Network (DSN) and National Surveillance System for Healthcare Workers (NaSH). [12]

Continued surveillance, along with sound infection control programs, not only lead to decreased healthcare-associated infections but also better prioritization of resources and efforts to improving medical care.

Healthcare-associated infections are of important wide-ranging concern in the medical field. They can be localized or systemic, can involve any system of the body, be associated with medical devices or blood product transfusions. This article focuses on the 3 major sites of healthcare-associated infections (ie, bloodstream infection, pneumonia, and urinary tract infection) with focus on the pediatric population.



Infectious agents causing healthcare-associated infections may come from endogenous or exogenous sources.

Endogenous sources include body sites normally inhabited by microorganisms. Examples include the nasopharynx, GI, or genitourinary tracts. Exogenous sources include those that are not part of the patient. Examples include visitors, medical personnel, equipment and the healthcare environment.

Patient-related risk factors for invasion of colonizing pathogen include severity of illness, underlying immunocompromised state, and/or the length of in-patient stay.



In a survey done on 110,709 pediatric ICU patients, 6,290 healthcare-associated infections were noted. [13]  The top 3 major sites of infections, accounting for 64% of all healthcare-associated infections, were bloodstream infections (28%), pneumonia (21%), and urinary tract infection (15%). Each of these infections was strongly associated with use of an invasive device.

The top 3 pathogens in bloodstream infections were coagulase-negative staphylococci (38%), Enterococcus (11%), and Staphylococcus aureus (9%). Candida albicans accounted for about 5.5% of bloodstream infections. The top 3 pathogens for pneumonia were P aeruginosa (22%), S aureus (17%), and Haemophilus influenzae (10%). The top 3 pathogens for urinary tract infections were Escherichia coli (19%), C albicans (14%), and P aeruginosa (13%). Gram-negative enteric organisms accounted for about 50% of all urinary tract infections. The top 3 pathogens for surgical site infections were S aureus (20%), P aeruginosa (15%), and coagulase-negative staphylococci (14%).

Methicillin-resistant Staphylococcus aureus (MRSA) has become a prevalent cause of infections. Traditionally, community-associated MRSA infections have been associated with USA300 or USA400 strains and healthcare-associated infections with USA100 or USA200 strains. However this distinction is becoming less clear with USA300 strains now increasingly identified as a cause of HAI. A population-based study showed MRSA USA300 was not associated with mortality for either central line–associated bloodstream infections or community-onset pneumonia. [14]

Surgical site infections (SSI) occur within 30 days after the operative procedure or within 1 year if an implant was placed. Criteria for the diagnosis of SSI include purulent drainage at the site of incision, clinical symptoms of infection (such as pain, redness, swelling, etc), presence of an abscess, isolation of organism from the site culture, and clinical diagnosis of SSI by the surgeon. [15]

Rotavirus continues to be a cause of acute gastroenteritis in hospitalized children, with greatest susceptibility in children younger than 3 years. Aside from having nonbloody diarrhea, patients may present with fever, vomiting, and abdominal cramps. Other viruses that can cause hospital-associated gastroenteritis include norovirus and adenoviruses. Gastroenteritis due to adenovirus can be especially debilitating in immunocompromised patients.

Clostridium difficile is the most important bacterial cause of healthcare-associated gastroenteritis. Associated clinical conditions include asymptomatic carriage, diarrhea, and pseudomembranous colitis. Diagnosis is suspected in a patient with diarrhea and recent history of antibiotic use (especially cephalosporins and clindamycin).



United States statistics

Healthcare-associated infections are estimated to occur in 5% of all hospitalizations in the United States. [16]  In 1999, national point-prevalence surveys in pediatric intensive care units (PICU) and neonatal intensive care units (NICU) showed 11.9% of 512 patients had PICU-acquired infections, whereas 11.4% of 827 patients had NICU-acquired infections. [17, 18]

The incidence of central line-associated BSI and VAP declined significantly between 2007 and 2012 in critically ill pediatric patients, according to a national cohort study of patients admitted to 173 neonatal intensive care units (NICUs) and 64 pediatric intensive care units (PICUs). [19, 20]  No change was observed, however, in the rate of catheter-associated UTI. In the NICUs, the rate of central line-associated BSI decreased from 4.9 to 1.5 per 1000 central-line days during the study period; in the PICUs, the rate fell from 4.7 to 1.0 per 1000 central-line days. [20]  The rate of VAP decreased from 1.6 to 0.6 per 1000 ventilator days in the NICUs and from 1.9 to 0.7 per 1000 ventilator days in the PICUs.

In 2014, the Centers for Disease Control and Prevention (CDC) released a pair of reports on healthcare-associated infections, with one indicating that significant progress has been made in their prevention. [21, 22]

In the National and State Healthcare-associated Infections Progress Report, the CDC notes a 44% reduction in central line–associated bloodstream infections and a 20% decrease in infections related to 10 surgical procedures, between the years 2008 and 2012. Other decreases were much smaller, with a 4% reduction in hospital-onset methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections and a 2% decrease in hospital-onset Clostridium difficile infections, occurring between 2011 and 2012. Catheter-associated urinary tract infections (UTIs) increased by 3% between 2009 and 2012.

In the second report, a survey of 11,282 patients from 183 acute care hospitals, Magill and colleagues found that 452 patients (4.0%) had at least 1 healthcare-associated infection (504 total infections). Device-associated infections, such as catheter-associated UTIs, were responsible for 25.6% of these. Surgical-site infections and pneumonia each accounted for 21.8%, and gastrointestinal infections accounted for approximately 17.1%. C difficile was the most common pathogen, causing 12.1% of healthcare-associated infections. The researchers estimated that nationwide, 648,000 patients had at least 1 healthcare-associated infection in 2011, with the total number of such infections coming to an estimated 721,800.

International statistics

Both developed and resource-poor countries are faced with the burden of healthcare-associated infections. In a World Health Organization (WHO) cooperative study (55 hospitals in 14 countries from four WHO regions), about 8.7% of hospitalized patients had nosocomial infections. [23]

A 6-year surveillance study from 2002-2007 involving intensive care units (ICUs) in Latin America, Asia, Africa, and Europe, using CDC's NNIS definitions, revealed higher rates of central-line associated blood stream infections (BSI), ventilator associated pneumonias (VAP), and catheter-associated urinary tract infections than those of comparable United States ICUs. [24]  The survey also reported higher frequencies of methicillin-resistant Staphylococcus aureus (MRSA), Enterobacter species resistance to ceftriaxone, and Pseudomonas aeruginosa resistance to fluoroquinolones.

A study of bacteremia in African children found distinct differences in the microbiological causes of nosocomial bacteremia compared with community-acquired bacteremia. Nosocomial bacteremia resulted in a higher rate of morbidity and mortality and longer hospital stay. Because it is largely unrecognized in low-income countries, nosocomial infections are likely to become public health priorities as their occurrence increases. [25]

Among pediatric patients in Ethiopia, Sahiledengle et al reported that the overall cumulative incidence of hospital-acquired infections was 12.7% (95% CI, 9.8-15.8%) over an 8-month period. Risk factors for infection were length of hospital stay and severe acute malnutrition. [26]

With increasing recognition of burden from healthcare-associated infections, national surveillance systems have been developed in various countries; these have shown that nationwide healthcare-associated infection surveillance systems are effective in reducing healthcare-associated infections. [27]




Healthcare-associated infections result in excess length of stay, mortality and healthcare costs. In 2002, an estimated 1.7 million healthcare-associated infections occurred in the United States, resulting in 99,000 deaths. [28]  In March 2009, the CDC released a report estimating overall annual direct medical costs of healthcare-associated infections that ranged from $28-45 billion. [29]

A report from the CDC showed that among the intensive care units in the United States, the year 2009 had 25,000 fewer central line-associated bloodstream infections (CLABSI) than in 2001, representing a 58% reduction. Between 2001 and 2009, an estimated 27,000 lives were saved and potential $1.8 billion cumulative excess health-care costs were prevented. Coordinated efforts from state and federal agencies, professional societies, and healthcare personnel in implementing best practices for insertion of central lines were thought to play a role in this achievement. [30]

Sex- and age-related demographics


Healthcare-associated infections do not have a discernible sex predilection.


Healthcare-associated infections occur in both adult and pediatric patients. Bloodstream infections, followed by pneumonia and urinary tract infections are the most common healthcare-associated infections in children; urinary tract infections are the most common healthcare-associated infections in adults. [13]  Among pediatric patients, children younger than 1 year, babies with extremely low birth weight (≤1000 g) and children in either the PICU or NICU have higher rates of healthcare-associated infections. [9, 17, 18, 13]