Infectious diseases that are acquired or develop during a stay in a medical facility are known as healthcare-associated infections (HAIs). This concept seems incongruous at first thought, because a hospital or clinic is regarded as a place to get treatment for a medical problem, not a place to acquire one. Yet it is not uncommon for a surgical incision to become infected or a patient with a catheter to develop a urinary tract infection after being treated in a hospital or clinic. The rate of hospital-acquired infections can be as low as 0.1% or as high as 20% of all admitted patients, depending on the clinical setting or hospital. The average rate is about 3% (1 out of 31 patients). In light of the number of admissions, this adds up to 1 million to 2 million cases a year, which result in around 72,000 deaths. By one estimate, they amount to 8 million additional days of hospitalization a year and an increased cost of $5 billion to $10 billion.
So many factors unique to the hospital environment create conditions that favor HAIs that a certain number of them are virtually unavoidable. After all, the hospital both attracts and creates compromised patients, and it serves as a collection point for opportunistic pathogens. Some patients become infected when surgical procedures or lowered defenses permit resident microbes to invade their bodies. Other patients ac quire infections directly or indirectly from contaminated catheters or ventilators and other medical equipment, other patients, medical personnel, visitors, air, and water.
The health care process itself increases the likelihood that infectious agents will be transferred from one patient to another. Treatments using reusable instruments such as respirators and endoscopes constitute a possible source of infectious agents. Indwelling devices such as catheters, prosthetic heart valves, grafts, and tracheostomy tubes form a ready portal of entry and habitat for infectious agents. Because such high numbers of the hospital population receive antimicrobial drugs during their stay, drug-resistant microbes are selected for at a much greater rate compared to outside the hospital.
The most common HAIs involve surgical incisions and the respiratory tract, GI tract, skin, urinary tract, and blood (sepsis) (figure 1). Gram-negative intestinal bacteria (Escherichia coli, Klebsiella, Pseudomonas) are cultured in more than half of patients with HAIs. Gram positive bacteria (staphylococci and streptococci) and yeasts (Candida) make up most of the remain der. True pathogens such as the tubercle bacillus, Salmonella, hepatitis B, and influenza virus can be transmitted in the clinical setting as well.
Fig1. Prevalence of healthcare-associated infections (HAIs). Relative frequency by body site. These are the most common isolates out of the nearly 500 pathogens that are known to cause HAIs. Source: National Health Safety Network, a unit of the CDC.
The potential seriousness and impact of healthcare-associated infections have required hospitals to develop committees that monitor infectious outbreaks and develop guidelines for infection control and aseptic procedures. Medical asepsis includes practices that lower the microbial load in patients, caregivers, and the hospital environment. These practices include proper hand washing, disinfection, and sanitization, as well as patient isolation. Table 1 summarizes guidelines for the major types of isolation. The goal of these procedures is to limit the spread of infectious agents from person to person. The most rigorous level of precautions is associated with surgical asepsis, which involves all of the strategies listed previously plus ensuring that all surgical procedures are conducted under sterile conditions. This includes sterilization of surgical instruments, dressings, sponges, and the like, as well as clothing personnel in sterile garments and scrupulously disinfecting the room surfaces and air.
Table1. Levels of Isolation Used in Clinical Settings
Hospitals generally employ an infection control officer who not only implements proper practices and procedures throughout the hospital but also is charged with tracking potential outbreaks, identifying breaches in asepsis, and training other health care workers in aseptic technique. Among those most in need of this training are nurses and other caregivers whose work, by its very nature, exposes them to needlesticks, infectious secretions, blood, and physical contact with the patient. The same practices that interrupt the routes of infection in the patient can also protect the health care worker. It is for this reason that most hospitals have adopted Standard Precautions that recognize that all secretions from all persons in the clinical setting are potentially infectious and that transmission can occur in either direction.
