Hospitals and infectious disease

ALSO KNOWN AS: Health-care-associated infections, nosocomial infections

Definition

Healthcare-Associated-Infections (HAIs), also referred to as nosocomial infections, materialize as a result of exposure to a healthcare setting. HAIs can occur while a patient is receiving care or can develop soon afterward. According to a 2020 estimate, the Centers for Disease Control and Prevention (CDC), reports that 5 percent of admissions to hospitals will result in an HAI. Annually, this will approximate 722,000 infections and 75,000 deaths. In 2023, CDC data reported that each day one in every thirty-one patients in the US contracts an HAI. To be diagnosed as nosocomial, the infection must not be associated with the admitting diagnosis and must occur because of a patient’s exposure to the surrounding pool of infectious agents. The infection usually becomes clinically evident after forty-eight hours of hospitalization or within thirty days of discharge. These infectious agents can colonize a person’s skin, respiratory tract, genitourinary tract, gastrointestinal tract, and bloodstream.

Causes

Most hospital acquired infections are caused by bacteria, viruses, or parasites. The causative organisms can be introduced through endotracheal (ET) intubation, catheterization, gastric drainage tubes, and intravenous procedures for medication delivery, blood transfusions, or nutrition supplementation. Infection also occurs through surgical procedures and by healthcare workers’ failing to wash their hands before procedures and between encountering patients. Other risk factors for hospital acquired infections include prolonged hospitalization, the severity of the patient’s underlying illness, the prevalence of antibiotic-resistant bacteria from the prolonged use or overuse of antibiotics, contaminated air-conditioning systems, contaminated water systems, lack of an appropriate ratio of nurses to patients, and overcrowding of beds. Later studies suggested that the uniforms and laboratory coats of hospital personnel may also help transfer pathogens. Also, it has been suggested that the shedding of epithelial tissues from the patients onto their hospital clothing may contribute to infections. Other reservoirs of contamination include stethoscopes, blood pressure cuffs, bed pans, water pitchers, telephones, and other objects. Airborne infections in hospitals may contribute to infections that include tuberculosis and herpes varicella.

Among the most common hospital acquired infections are pneumonia and urinary tract infections. In terms of the latter, the common procedure of placing a catheter into the bladder for delivery of medication, for measuring urinary output, for the relief of pressure, or for other medical reasons creates a port of entry for infectious agents. The healthy bladder is normally sterile; it contains no harmful bacteria or other organisms. The catheter can pick up bacteria or organisms from the urethra, providing an easy route to the bladder. This infection, known as catheter-associated urinary tract infection (CAUTI), can occur because of improper sterilization techniques, which creates a mechanical entry for infection through, for example, multiple tries to insert the catheter; even the composition of the catheter can lead to infection of the bladder. It is now recognized that a major cause of nosocomial infection is the picking up of bacteria, such as Escherichia coli (E. coli), or other organisms from the intestinal tract and transferring them to the bladder. Irritation from the catheter’s insertion and prolonged use of the catheter can transfer bacteria (and a fungus called Candida). An infection caused by an indwelling catheter will need long-term treatment with antibiotics; this long-term treatment can compromise the patient’s immune system, thereby causing further harm.

Nosocomial pneumonia is another leading hospital-acquired infection. Bacteria and other microorganisms enter the respiratory system through procedures treating respiratory illnesses. The placement of ET tubes for mechanical ventilation is of primary concern. If ET tubes are inserted (such as by a paramedic) while the patient is outside a hospital or even in an emergency room, the risk of infection is greater. The introduction of aids for ensuring adequate ventilation often leads to infection. Aspiration from the nose, throat, and lungs is a direct pathway for introduction of microorganisms.

Surgery accounts for similar numbers of all US nosocomial infections. Agents of surgical-site infection (SSI) include contaminated surgical equipment, the contaminated hands of healthcare providers, contaminated dressings, trauma wounds, burn wounds, and pressure sores from prolonged bed rest or wheel chair use. The continuous delivery of medications, transfusions, antibiotics, or nutrients through the bloodstream by intravenous (IV) routes is yet another common cause of infection, known as central line–associated blood stream infection (CLABSI). Improper technique causes bacteria to enter the body at the placement of IVs and increases the risk of infection the longer the IVs are in place. Infections in the blood are of special concern because they can produce disseminating infections. Gastrointestinal procedures, such as colonoscopy; obstetric procedures; and kidney dialysis can also lead to major infections.

Antibiotic resistance has led to an increase in several other nosocomial infections, including superinfections. Generally, the major causative pathogens for hospital acquired infections relate to the location of the involved body system or systems, except for the bloodstream, which when infected can cause dissemination of the infection to all major organs. By classifying major pathogens according to the organ systems they affect, one can differentiate among these varying pathogens. The major pathogens for the genitourinary system are gram-negative enterics, fungi, and enterococci. Bloodstream infectious agents are usually coagulase-negative staphylococci, enterococci, fungi, Staphylococcus aureus, Enterobacter species, Pseudomonas, and Acinetobacter baumannii (which causes substantial antimicrobial resistance). Surgical-site infections include S. aureus, Pseudomonas, coagulase-negative staphylococci, and (rarely) enterococci, fungi, Enterobacter species, and E. coli.

Ventilator-associated pneumonia (VAP) is designated as either early or late onset. Early onset begins within the first three to four days of mechanical ventilation. The infections are usually antibiotic-sensitive and are most often caused by S. pneumoniae, H. influenza, or S. aureus. Late-onset infections that are antibiotic-resistant and are main causative agents are those caused by Ps. aeruginosa, Actinobacter spp., and Enterobacter spp. Other pneumonias caused by gram-negative bacterium are Klebsiella pneumoniae, Legionella, or methicillin-resistant Staphyloccocus aureus (MRSA), known as the superbug.

A relatively new hospital-acquired infection is colitis, caused by the organism Clostridium difficile. This gram-positive, anaerobic, spore-forming bacillus is responsible for antibiotic-associated diarrhea and colitis. The infection is caused by a disturbance of the normal bacterial flora in the colon, precipitated by antibiotic therapy. The colonization of C. difficile releases two toxins: toxin A, an endotoxin, and toxin B, a cytotoxin, leading to mucosal inflammation and damage of the colon.

Risk Factors

Although all hospital patients are susceptible to nosocomial infections, young children, especially those in the neonatal intensive care unit (ICU); adult ICU patients; older adults; and patients with compromised immune systems are more likely to acquire these infections. Other risk factors include having underlying diseases such as chronic lung disease, diabetes, or cardiac disease; being obese; being malnourished; having a malignancy; having a remote infection; using prophylactic antibiotics; and hospitalization before surgery (especially for twelve hours or longer), which increases the patient’s exposure to the reservoir of infectious agents.

Symptoms

The primary sign of infection is fever. A person’s admission temperature and those temperatures recorded at the time of hospitalization and after hospitalization are paramount for recognizing a developing infection. Other symptoms of infection include an increased respiratory rate; increased pulse rate; sweating, especially at night; chest pain; productive phlegm with coughing or an inability to cough; pain and discharge from the nose or mouth; fatigue; difficulty and pain with swallowing; nausea; vomiting; excessive diarrhea; pain with urination or blood present in urine; reduced urine output; redness and swelling with pustular discharge around surgical wounds or openings in sutures from skin closures with exposure to subcutaneous tissues; and the development of skin rashes.

Screening and Diagnosis

The foregoing signs and symptoms suggest infection. It is recommended to notify the doctor immediately if any of these symptoms are present during or after hospitalization. The first diagnostic tool is a complete physical examination, which includes laboratory studies and x-rays. Other tests include extensive blood testing, with a complete blood count that looks for an increase in infection-fighting white blood cells; a complete urinalysis that includes culture and checks for a sensitivity to antibiotics; two blood samples drawn twenty minutes apart for culture and sensitivity; sputum for culture and sensitivity; and wound cultures for culture and sensitivity. Ancillary tests include abdominal x-rays or computed tomography (CT) scans (detailed x-rays that identify abnormalities of fine tissue structure); kidney x-rays; kidney, liver, and pancreas function tests; blood gas tests; and tests for fungus infective agents.

Treatment and Therapy

While waiting for the laboratory culture and sensitivity results, which may take up to forty-eight hours to complete, most patients begin broad-spectrum antibiotic therapy. This usually includes penicillin, cephalosporins, tetracycline, or erythromycin, and supplemental oxygen if needed. The doctor will need to know if the patient is allergic to certain antibiotics or if the patient has been on prolonged antibiotic therapy. It is usual to combine antibiotics for therapy, so, for best results, the doctor must determine if the infecting organism is gram-positive or gram-negative or whether it is anaerobic bacteria, resistant bacteria, or fungi. Once the causative agent for infection has been identified, aggressive therapy begins. Recommended treatments include vancomycin, imipenem plus cilastatin, meropenem, azteonam, piperacillin plus tazobactam, ceftazidme, and cefepime. If MRSA is suspected, limezoid can be used.

Other treatments that can be used to supplement antibiotic therapy include pulmonary hygiene and respiratory treatments, aggressive wound care, fever control until the antibiotics show evidence of effectiveness, body cleansing, changing of hospital garments, and extreme sterile techniques when treating the patient (which may include putting the patient in reverse isolation for protection of further exposure to infections). Close monitoring of cardiac status, urine output, and pulmonary functions is recommended. The changing of catheters, IV lines, gastrointestinal (GI) tubes, and other invasive forms of exposure may also be ordered by the doctor. The hospital’s medical team and infectious disease control team will monitor the patient’s status and present complete documentation of the case.

Prevention and Outcomes

The recommendations for the prevention of infections acquired in hospitals and other healthcare facilities cover a broad geographic, demographic, cultural, and ecological spectrum. The recommendations are based on the type of causative agents as precursors for disease in the associated populations. Requirements, although based on sound science, can sometimes be misinterpreted or even ignored. A good foundation for practice is to bring together basic infection-control measures and the history of epidemiology. Historically, this practice could be said to have begun in the nineteenth century with Florence Nightingale, who believed respiratory secretions could be dangerous, and with Ignaz Semmelweis, a nineteenth century obstetrician who demonstrated that routine handwashing could prevent the spread of puerperal fever. Joseph Lister, a nineteenth century professor of surgery, was the first to realize the connection between the suppuration of wounds and the discoveries of the fermentation process (by chemist and microbiologist Louis Pasteur) in the mid-nineteenth century. Lister published his findings in 1867 and was credited with helping to start the practice of sterilizing operating rooms with carbolic acid.

The CDC began hospital surveillance in the United States in the 1960s. The 1970s saw the introduction of training courses in disease prevention and the establishment of the CDC’s Division of Healthcare Quality and Promotion for hospital infection programs and the National Nosocomial Infections Surveillance System. The Study on the Efficacy of Nosocomial Infection Control was conducted in the early 1970s. The Healthcare Infection Control Practices Advisory Committee was formed in 1991. In 2005, hospitals began contributing surveillance to the National Healthcare Safety Network, which was reworked with a comparison study in 2007. The initiatives created by these agencies and programs provide guidelines for improvement in the prevention of hospital acquired infections.

These guidelines include adopting infection control programs in accordance with the CDC to track trends in infection rates, ensuring that one practitioner is available for every two hundred beds in hospitals and other healthcare facilities, identifying high-risk medical procedures, strict adherence by medical staff and visitors to handwashing policies, and other sterilization techniques. These include using sterile gowns, gloves, masks, and barriers; sterilizing reusable equipment, including ventilators, humidifiers, or other respiratory equipment that comes in contact with a patient’s respiratory tract; frequently changing wound dressings and using antimicrobial ointments; removing nasalgastric and endotracheal tubes as soon as possible; using antibacterial-coated venous catheters; preventing infection by airborne microbes through wearing masks (by hospital personnel and patients); limiting the use of high-risk procedures such as urinary catheterization; isolating patients with known infections; and reducing the general use of antibiotics.

Patients are also able to positively influence a reduction of HAIs. Steps that can be taken include becoming more knowledgeable on treatments so that a dialogue can be maintained with healthcare providers. This includes attaining background information on antibiotics and how to recognize an infection. Patients can also ensure they are up to date on vaccinations. A simple but effective measure is to always ensure that hands are washed on a regular basis. This is likely the best way to prevent infection from spreading.

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