• Nosocomial comes from the Greek words “nosus” which means disease and “komeion” which means to take care of.• A nosocomial infection is an infection that occurs or originates in a hospital or a health care setting, and whose development and spread is favored by hospital environment such as an infection acquired during a hospital stay or visit.• Also defined as an infection not present and without evidence of incubation at the time of admission to a healthcare setting.
• Nosocomial infections are also known as hospital-acquired infections (HAI).• As health care increasingly expands beyond hospitals into outpatient settings, nursing homes, long-term care facilities, and even home care, the more appropriate term has become healthcare- associated infections (also healthcare-acquired infections), Replacing older ones such as nosocomial, hospital-acquired or hospital-onset infections.
• 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.
• In the United States, the Centers for Disease Control and Prevention (CDC) estimate that roughly 2 million hospital-associated infections occur each year.• They affect 5% to 10% of hospitalized patients.• They cause approximately 90.000 deaths.• They add $45 billion to the total US healthcare bill each year.
• A prevalence survey conducted under the auspices of WHO in 55 hospitals of 14 countries representing 4 WHO Regions (Europe, Eastern Mediterranean, South-East Asia and Western Pacific) showed that: An average of 8.7% of hospital patients had nosocomial infections. At any time, over 1.4 million people world-wide suffer from infectious complications acquired in hospital.
• The overall increase in the duration of hospitalization for patients with surgical wound infections was 8.2 days, ranging from 3 days for gynaecology to 9.9 for general surgery and 19.8 for orthopaedic surgery.
• Nosocomial infections are important contributors to morbidity and mortality.• They will become even more important public health problems with increasing human and economic impact because of: Crowded hospital conditions. More frequent impaired immunity (age, illness, treatments). More than 70 % of bacteria that cause hospital-acquired infections are resistant to at least one of the drugs most commonly used in treatment. Emerging pathogens.
• Nosocomial infections are the result of three factors occurring in tandem:1. High prevalence of pathogens.2. Large numbers of compromised hosts.3. Efficient mechanisms of transmission from patient to patient (chain of transmission).
• Hospitals house large numbers of people whose immune systems are often in a weakened state.• Medical staff move from patient to patient, providing a way for pathogens to spread.• Many medical procedures bypass the bodys natural protective barriers.
• The most common sites affected by nosocomial infections are: urinary tract. surgical wounds. respiratory tract . skin (especially burns). blood (bacteremia). gastrointestinal tract. central nervous system.
• Antimicrobial agents Antimicrobial chemotherapy disturbs normal microbial flora populations eliminating the competition for pathogens. Antibiotics also exert selective pressure which favors the emergence of resistant strains in hospital environments.
• Surgery: breaches natural barriers to infection providing microbes with access to sensitive unprotected tissues and organs.• Invasive devices: such as intubation tubes, catheters, surgical drains, and tracheostomy tubes all bypass the body’s natural lines of defense.
• Contact transmission is the most important and frequent mode of transmission of nosocomial infections.• It is divided into two subgroups: direct contact and indirect contact.
• Direct contact transmission: Involves direct contact between body surfaces which physically transfers microorganisms from an infected or colonized person (doctor, nurse, co-patient, etc..) to a susceptible host, during patient care activities (e.g. feeding). Direct contact transmission can occur between patients.
• Indirect-contact transmission: Involves contact between a susceptible host and a contaminated intermediate object. Such objects include contaminated instruments, needles, or dressings, or contaminated gloves that are not changed between patients.
• Droplet transmission: Occurs when droplets generated by coughing, sneezing, talking, or during certain procedures such as bronchoscopy are propelled through the air and deposited on a susceptible host.
• Airborne transmission: Occurs by the dissemination of small droplet nuclei or evaporated droplets that contain microorganisms that remain suspended in the air for a long time. Microbes can also be carried by dust particles. In this mode of transmission organisms can be dispersed by air currents in different directions and long distances (e.g. other rooms, wards etc..)
• Common vehicle transmission: The mode of transmission of infectious pathogens from a source that is common to all the cases of a specific disease, by means of a medium, or "vehicle," such as water, food, air, or the blood supply used by a transfusion service to a number of people.
• Vector transmission: Occurs when an insect, arthropod, or rodent is the source of infection.
• The source of the infecting organism may be: Exogenous: from another patient or a member of the hospital staff, or from the inanimate environment in the hospital. Endogenous: from the patient’s own flora which may have acquired new characteristics from other organisms in the hospital environment.
• A large number of microorganisms are responsible for hospital infection.• In fact any microbe may have the ability to cause an infection in the hospitalized patient.• Healthcare-associated infections can be caused by bacterial, viral, fungal, and even parasitic agents.
• The causative microorganisms may be broadly classified into the following categories:1. “Conventional” pathogens that could cause disease in healthy persons in the absence of any specific immunity to them.
2. “conditional” pathogens that could cause disease (other than simple localized infections) only in persons with lowered resistance to infection or when implanted directly into tissue or normally sterile area.
3. “Opportunistic” pathogens that could cause severe disease only in patients with greatly diminished resistance to infection.• These distinctions are not clear cut and the grading of individual pathogens can be challenged.
• According to the United States National Nosocomial Infections Surveillance (NNIS) System data, the five most commonly reported pathogens are: Escherichia coli (13·7%). Staphylococcus aureus (11·2%). Enterococci (10·7%). Pseudomonas aeruginosa (10·1%). Coagulase-negative staphylococci (9·7%).
• Urinary tract infection: E. coli, enterococci, and P. aeruginosa.• Surgical wound infection: S. aureus, enterococci and coagulase-negative staphylococci.• Bloodstream: coagulase-negative staphylococci, S. aureus, enterococci, E. coli, and Candida spp.• Lower respiratory tract infection: S. aureus. P. aeruginosa and Enterobacter spp.
• Among patients in the intensive care unit (ICU) the commonest pathogens were: P. aeruginosa (12·4%). S. aureus (12·3%). coagulase-negative staphylococci (10·2%). Candida spp. (10·1%). Enterobacter spp. and enterococci (8·6% each).
• There is the possibility of nosocomial transmission of many viruses, including: The hepatitis B and C viruses (transfusions, dialysis, injections, endoscopy). Respiratory syncytial virus (RSV), rotavirus, and enteroviruses (transmitted by hand-to-mouth contact and via the faecal-oral route). Other viruses such as cytomegalovirus, HIV, Ebola, influenza viruses, herpes simplex virus, and varicella- zoster virus, may also be transmitted.
Source Bacteria Viruses FungiFood Salmonella species Rotavirus Staphylococcus aureus Clostridium perfringens Caliciviruses Clostridium botulinum Bacilluscereus and other aerobic spore-forming bacilli Escherichia coli Campylobacter jejuni Yersinia enterocolitica Vibrio parahaemolyticus Vibrio cholerae Aeromonas hydrophilia Streptococcus species Listeria monocytogenes
Methods of prevention of nosocomial infection (and breaking the chain of transmission ) include:• Observance of aseptic technique.• Frequent hand washing especially between patients.• Careful handling, cleaning, and disinfection of equipment.• Where possible, use of single-use disposable items.• Patient isolation.
Methods of prevention of nosocomial infection (continued):• Avoidance where possible of medical procedures that can lead with high probability to nosocomial infection.• Various institutional methods such as air filtration within the hospital (Architectural Design).• General awareness that prevention of nosocomial infection requires constant personal surveillance.• Active oversight within the hospital.
• Proper hand washing is the single most important measure for the Prevention of nosocomial infections.• Yet, compliance among healthcare workers is suboptimal ranging from 16% to 81%.• This is due to a variety of reasons, including: Lack of appropriate accessible equipment High staff-to-patient ratios Allergies to hand washing products. Insufficient knowledge of staff about risks and procedures. Too long a duration recommended for washing.
• Caps and dedicated shoes are required for operating rooms and aseptic units.• Masks protect staff against airborne pathogens and must be used when working in the operating room, to care for immunocompromised patients, to puncture body cavities or perform procedures such as bronchoscopy. Patients with air-borne pathogens wear masks when outside their isolation room.
• Sterile gloves for surgery, care for immuno- compromised patients, and invasive procedures.• Non-sterile gloves should be worn for all patient contacts where hands are likely to be contaminated.• Hands must be washed when gloves are removed or changed.• Disposable gloves should not be reused.• Latex or polyvinyl-chloride are the materials most frequently used for gloves.• Quality and duration of use vary considerably from one glove type to another.
According to the WHO guidelines on infection control, four areas of a healthcare facility are defined: • Administrative sections considered as low-risk areas. • Regular patient wards as moderate-risk areas. • Intensive care units, burn units, or isolation units as high-risk areas. • Operating rooms as very high-risk areas.WHO and others have recommended that traffic flow should be limited in higher risk areas.
The microbiologist is responsible for:• Handling patient and staff specimens to maximize the likelihood of a microbiological diagnosis.• Developing guidelines for appropriate collection, transport, and handling of specimens.• Ensuring laboratory practices meet appropriate standards.• Ensuring safe laboratory practice to prevent infections in staff.
• Performing antimicrobial susceptibility testing following internationally recognized methods, and providing summary reports of prevalence of resistance.• Monitoring sterilization, disinfection and the environment where necessary.• Timely communication of results to the Infection Control Committee or the hygiene officer.• Epidemiological typing of hospital microorganisms when necessary.