NOSOCOMIAL (HOSPITAL ACQUIRED) INFECTIONS

Hospital acquired infections are also known as nosocomial infections or health-care-associated infections. These infections are those that are absent in the patient at the time of hospital admission but develop them 48 hours after admission. 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. Iatrogenic infections are physician-induced infections. Hospital-acquired infections are usually related to a procedure or treatment used to diagnose or treat the patient's initial illness or injury.

Epidemiology:
Within hours of admission into the hospital the patients skin, respiratory tract, GIT, genito-urinary tract may be colonised by hospital bacterial strains that are usually drug resistant. All hospitalised patients are at risk of acquiring an infection from their treatment or surgery. Some patients are at greater risk than others, especially young children, the elderly, and persons with compromised immune systems. The incidence of nosocomial infection is highest in burn units, surgical ICUs and ICUs for low birth weight neonates, intermediate in medical and paediatric ICUs and lowest in coronary care units. The infection rates may be low in the early days of ICU stay, but can increase up to 80% as the duration of stay exceeds 5 days or more. Risks factors for the invasion of colonizing pathogens are:
Iatrogenic risk factors: These include the prophylactic or therapeutic use of antibiotics, transmission of pathogens from medical personnel and the use of invasive procedures (use of indwelling catheters, kidney dialysis).
Organizational risk factors such as contaminated water, air-conditioning systems, physical layout of wards etc. 
Patient risk factors include the severity of illness, underlying immunocompromised state, compromised nutritional status and length of stay.
Other risk factors that increase the opportunity for hospitalised adults and children to acquire infections are failure of health care workers to wash their hands between patients or before procedures, prevalence of antibiotic-resistant bacteria from the overuse of antibiotics and concomitant therapy with immunosuppressive agents.

Etiology:
Nosocomial infections are caused by viral, bacterial, and fungal pathogens. These microorganisms may already be present in the patient's body or may come from the environment, contaminated hospital equipment, health care workers, or other patients. Common bacterial infections are due to Staphylococcus, Enterobacter, Klebsiella, Serratia, Pseudomonas, Proteus and Acinetobacter sps. Viruses are the leading etiologies of nosocomial infections in paediatric patients in some countries. Some of these include influenza, parainfluenza, respiratory syncytial viruses, rotavirus and enterovirus infections. Fungal infections more likely to arise from the patient's own flora; occasionally, they are caused by fungi in hospital environment. The source of hospital-acquired infection may be suggested by instrumentation. For example, endotracheal tube may be associated with sinusitis, otitis, and pneumonia; intravascular catheter may lead to phlebitis, endocarditis; Foley catheter may cause urinary tract infection, CSF shunt may cause meningitis. These infections can be localised such as surgical wound abscess or systemic when blood stream is infected.

Various nosocomial infections include bloodstream infections, ventilator-associated pneumonia, urinary tract infection, lower respiratory infection, surgical-site infections, burn infection. Prolonged use of antibiotics can lead to pseudomembranous colitis due to Clostridium difficle. Organisms responsible for blood stream infections are Coagulase-negative staphylococci, Enterococci, Fungi, Staphylococcus aureus, Enterobacter sps, Pseudomonas, Acinetobacter baumannii. Organisms causing urinary tract infections include Gram-negative enterics bacilli, Candida, Enterococci and Pseudomonas. Nosocomial etiologies in surgical-site infections include the following S aureus, Pseudomonads, Coagulase-negative staphylococci, Enterococci, fungi, Enterobacter species, and Escherichia coli.

Diagnosis
An infection is suspected any time a hospitalized patient develops a fever that cannot be explained by the underlying illness. Some patients, especially the elderly, may not develop a fever. Diagnosis includes evaluation of symptoms and signs of infection, examination of wounds and catheter entry sites for redness, swelling, or the presence of pus or an abscess. laboratory tests, including complete blood count, urinalysis, cultures of the infected area, blood, sputum, urine, or other body fluids or tissue to find the causative organism. Special Concerns must be given to multiple antibiotic-resistant organisms, such as vancomycin-resistant enterococci, glycopeptide-resistant S aureus, and inducible or extended-spectrum beta-lactamase producing gram-negative organism.

Prevention
About 36% of these infections are preventable through the adherence to strict guidelines by health care workers. Hospitals should take a variety of steps to prevent nosocomial infections such as:

• Adopt an infection control program, which includes quality control of procedures known to lead to infection, and a monitoring program to track infection rates. 

• Employ an infection control practitioner for every 200 beds. 

• Identify high-risk procedures and other possible sources of infection. 

• Strict adherence to hand-washing rules by health care workers and visitors to avoid passing infectious microorganisms to or between hospitalized patients. 

• Strict attention to aseptic (sterile) technique in the performance of procedures, including use of sterile gowns, gloves, masks, and barriers. 

• Sterilization of all reusable equipment such as ventilators, humidifiers, and any devices that come in contact with the respiratory tract. 

• Frequent changing of dressings for wounds and use of antibacterial ointments under dressings. 

• Remove nasogastric (nose to stomach) and endotracheal (mouth to stomach) tubes as soon as possible. 

• Use of an antibacterial-coated venous catheter that destroys bacteria before they can get into the blood stream. 

• Prevent contact between respiratory secretions and health care providers by using barriers and masks as needed. 

• Use of silver alloy-coated urinary catheters that destroy bacteria before they can migrate up into the bladder. 

• Limitations on the use and duration of high-risk procedures such as urinary catheterization. 

• Isolation of patients with known infections. 

• Sterilization of medical instruments and equipment to prevent contamination. 

• Reductions in the general use of antibiotics to encourage better immune response in patients and reduce the cultivation of resistant bacteria.