Molecular Techniques for the Study of Hospital Acquired Infection

Steven L. Foley, Anne Y. Chen, Shabbir Simjee, Marcus J. Zervos, Steven L. Foley, Anne Y. Chen, Shabbir Simjee, Marcus J. Zervos

• Publisher: Wiley-Blackwell
• Year: 2011
• Print ISBN: 9780470420850
• eBook ISBN: 9781118063835
• Edition: 1
• Topic: Medicine
• Subtopic: Infectious Diseases

Providing a broad overview of the microbial pathogens associated with hospital-acquired human illness, Techniques for the Study of Hospital Acquired Infection examines the cost-effective use of laboratory techniques in nosocomial infectious disease epidemiology and control. This concise guide addresses the cost benefits of combining modern molecular techniques with the traditional activities of infection control departments. The book is useful as a guide to hospital infection control programs as well as a text for medical practitioners, grad/medical students, researcher scientists, population biologists, molecular biologists, and microbiologists.

Part One

Introduction to Healthcare-Associated Infections and their Control

Chapter 1

The Hospital and Ambulatory Care Environment

Hiren Pokharna and Anne Y. Chen

Introduction

Healthcare-Associated Infections (HAIs): The Evolution

Although the modern-day concepts of prevention and control of hospital-associated infections originated in the middle of the nineteenth century, the history regarding knowledge about hospital-related infections dates back to the sixteenth century. Ambroise Pare (1517–1590), a surgeon at Hotel-Dieu in Paris, was one of the first physicians to describe increased frequency and severity of wound infections in hospitalized patients compared to nonhospitalized patients. The phrase “hospital disease” was first used in the eighteenth century. Hungarian physician Ignaz Philipp Semmelweiss (1818–1865) introduced the concept of hand washing while Sir Joseph Lister (1827–1912), a British surgeon, pioneered the concept of asepsis. Over the years, the Center for Disease Control and Prevention (CDC) has published several sets of definitions for Nosocomial Infections. Definitions used during the Comprehensive Hospital Infections Project (CHIP) (1969–1972) and in the National Nosocomial Infectious Study (NNIS) (1970–1974) were first used in the Proceedings of the First International Conference on Nosocomial Infection organized by CDC in 1970 (1]. Definitions were further extended in 1974 for hospitals participating in NNIS (2]. Definitions for nosocomial infections were again modified by CDC in 1988 (3]. The term HAI (4] was officially introduced in 2008 to reflect infections acquired by patients while receiving treatment for any surgical or medical conditions. It was defined as a localized or systemic condition resulting from an adverse reaction to the presence of an infectious agent(s) or its toxin(s) without any evidence that the infection was present or incubating at the time of admission to the acute care setting. HAIs can occur in acute care settings within hospitals or in ambulatory outpatient care settings, including same-day surgical centers or dialysis center. HAIs are increasingly associated with long-term facilities such as nursing homes and rehabilitation centers.

Healthcare-associated infections (HAIs) are a major cause of morbidity and mortality in the United States. It is estimated that there were 1.7 million HAI in 2002 which resulted in around 99,000 deaths, making it among the most common healthcare-associated adverse event (5]. HAIs can occur in patients at any age and in any healthcare setting, but the most common infections are seen among adults and children in the non-ICU setting. According to National Nosocomial Infections Surveillance (NNIS) system data from 1990 to 2002, out of an estimated 98,987 deaths associated with HAI in the United States hospitals, 35,967 were due to pneumonia, 30,665 were related to bloodstream infections, 13,088 were related to UTIs, 8205 were due to for surgical site infections (SSI), and 11,062 due to infections from other sites.

HAIs have significant economic implications as well. They increase the healthcare burden on the society by $35.7–45 billion every year (6].

Pathogens

Bacteria remain the most common pathogens and source of HAIs (7, 8]. HAI are typically associated with Gram-positive pathogens including methicillin-resistant Staphylococcus aureus (MRSA) (9–13], coagulase-negative Staphylococci (14], and glycopeptide (vancomycin)-resistant Enterococci spp. (15–20]. More recently, there are increasing reports of glycopeptide intermediate and glycopeptide-resistant S. aureus (21]. Clostridium difficile, a normal intestinal flora in 3% of healthy adults and 20–30% of hospitalized adults (22], is responsible for 25–30% of antibiotic-associated diarrhea and is being increasingly recognized as a major nosocomial pathogen (23–27]. There is increasing resistance among Gram-negative organisms. Among Enterobacteriaceae pathogenic isolates, resistance to fluoroquinolones, extended-spectrum cephalosporins, and carbapenems is increasing (14]. There is also an increasing carbapenem resistance among Acinetobacter spp. (14, 28] and Klebsiella pneumoniae (14]. MDR Pseudomonas spp., Klebsiella spp. and Enterobacter spp. are concerning as well. Emerging resistance to carbapenems conferred by New Delhi metallo-B-lactamase 1 (NDM-1) in countries such as India, Pakistan, and United Kingdom is a potential global health problem that will require coordinated international surveillance (29].

Candida species remain the most common healthcare-associated pathogens among fungi (14, 30]; and although less common, viruses including Adenovirus, Rotavirus, Norovirus, and hepatitis B have been recognized as nosocomial pathogens.

Common HAIs

Urinary Tract Infection (UTI)

UTIs are the most common HAIs in both acute care setting and long-term care facilities. A major cause of septicemia and mortality, rates are similar in adult and pediatric patients (31] and account for 36% of all HAIs (5]. Intrinsic risk factors associated with UTIs include: advanced age, female gender, and severity of underlying illness (e.g., diabetes mellitus (DM)) (32]. Duration of indwelling catheterization is by far the most important extrinsic risk factor for UTIs (33]. Indwelling urinary catheters are used in nearly all hospital nursing units, unlike ventilators and many other devices. Various studies have emphasized that catheter use is frequently inappropriate; inattention to both the proper indications for catheter use and catheter status in patients seems to be an important factor (34–39].

The most common etiologic agents for catheter-associated UTI (CAUTI) as reported to the NHSN at CDC, 2006–2007, are E. coli (21%), Candida spp. (20%) [C. albicans (14%)], Enterococcus spp. (15%), P. aeruginosa (10%), K. pneumoniae (8%), Enterobacter spp. (4%), coagulase-negative Staphylococci (3%), S. aureus (2%), A. baumannii (1%), and K. oxytoca (1%) (14).

Hospitals and Long-Term Care Facilities (LTCF) should develop, maintain, and propagate policies regarding indications for catheter insertion and removal. Education of staff, use of condom catheters where appropriate, and consideration of intermittent catheterization and suprapubic catheterization as an alternative to short-term or long-term indwelling urethral catheterization have all been recommended to reduce the risk of nosocomial UTIs (40).

Pneumonia

Pneumonia is the third most common HAI, the second most common in the ICU, and the most common cause of mortality among all HAIs (5). It is associated with considerably increased healthcare costs and hospitalization days (32, 41). Hospital-acquired pneumonia (HAP) is defined as pneumonia that occurs 48 hours or more after admission, which was not incubating at the time of admission (42, 43). Ventilator-associated pneumonia (VAP) refers to pneumonia that arises more than 48–72 hours after endotracheal intubation (44, 45). Healthcare-associated pneumonia (HCAP) includes any patient who was hospitalized in an acute care hospital for two or more days within 90 days of the infection; resided in a nursing home or long-term care facility; received recent intravenous antibiotic therapy, chemotherapy, or wound care within the past 30 days of the current infection; or attended a hospital or hemodialysis clinic (43, 45, 46). Most current data, including microbiological, have been collected from patients with VAP but can be extrapolated to HAP and HCAP patients as well (47). Tracheal intubation and mechanical ventilation are the strongest risk factors, with 3- to 21-fold increase in risk for nosocomial pneumonia (48).

Among etiologic agents, S. aureus (24%) is the most common pathogen, followed by Gram-negative organisms: P. aeruginosa (16%), Enterobacter spp. (8%), A. baumannii (8%), K. pneumoniae (7%), and E. coli (5%) (14).

Various infection control measures can help modify the risk factors for pneumonia. Intubations and reintubations should be avoided if possible, and noninvasive modes of ventilation should be used whenever possible. Orotracheal intubations and orogastric tubes, semirecumbent position rather than supine position, continuous aspiration of subglottic secretions, adequate endotracheal cuff pressures to prevent leakage of bacterial pathogens into the lower respiratory tract, and passive humidifiers or heat-moisture exchangers can all help decrease the risk for VAP (47).

Surgical site infections (SSIs)

SSIs are second only to UTIs in frequency, accounting for 22% of all HAIs (5). It is estimated that SSI develop in 2–5% of the 27 million patients undergoing surgical procedures each year (49, 50). Healthcare personnel and operating room environment have been implicated as common sources of pathogens for SSIs. Prolonged preoperative stay, preoperative shaving, length of surgery, and skill of surgeons are well-documented risk factors for SSIs (51). Intrinsic host-related risk factors include: severity of underlying illness (e.g., high American Society for Anesthesiology score, DM), obesity, advanced age, malnutrition, trauma, loss of skin integrity (e.g., psoriasis), and presence of remote infections at time of surgery (32).

Most common etiologic agents are: S. aureus (30%), coagulase-negative Staphylococcus (14%), Enterococcus spp. (11%), E. coli (10%), P. aeruginosa (6%), Enterobacter spp. (4%), K. pneumoniae (3%), and Candida spp. (2%) (14).

Various pre-, intra- and postoperative measures will help minimize the risk of SSI (51). Preoperative bathing with an antimicrobial has been advocated to reduce skin colonization (52). Removing hair from the site of surgery and preoperative skin preparation reduces contamination of the operative site (53). Clipping with clippers or using cream to remove hair results in fewer surgical site i...

Table of contents

• Cover
• Title Page
• Copyright
• Dedication
• Contributors
• Foreword
• Preface
• Part I: Introduction to Healthcare-Associated Infections and Their Control
• Part II: Techniques to Characterize Nosocomial Pathogens
• Part III: Application of Techniques to Characterize Predominant Nosocomial Pathogens
• Index