NOSOCOMIAL INFECTION

DEFINITION

• nosocomial infections are any infection that acquired while in a hospital or healthcare setting.

• These types of infections are acquired while a patient is admitted to the hospital for treatment of other conditions.

• Most infections that become clinically evident after 48 hours of hospitalization are considered hospital-acquired

• The source of infections are:

1. other patients,

2. hospital staff,

3. contaminated objects or solutions,

4. from the patient himself (such as transfer from one site of the body to another).

• Most common nosocomial infections are surgical wound infections, urinary and respiratory tract infections, and bacteremia (bloodstream infections).

CONTAMINATED SURFACES INCREASE CROSS-TRANSMISSION

KNOWN NOSOCOMIAL INFECTION

• Ventilator-associated pneumonia

• Staphylococcus aureus

• Methicillin resistant Staphylococcus aureus

• Candida albicans

• Pseudomonas aeruginosa

• Acinetobacter baumannii

• Stenotrophomonas maltophilia

• Clostridium difficile

• Tuberculosis

• Urinary tract infection

• Hospital-acquired pneumonia

• Gastroenteritis

• Vancomycin-resistant Enterococcus

• Legionnaires' disease

REASONS WHY THE PROBLEM EXISTS

• 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).

SITES COMMONLY AFFECTED

• 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.

RISK FACTORS

• all poor health: advanced age, premature birth, and concurrent conditions (e.g. chronic obstructive pulmonary disease COPD, diabetes).

• Compromised immunity: Immunodeficiency, immunosuppressive therapy, irradiation, undernourishment etc..

• Antimicrobial chemotherapy disturbs normal microbial flora populations (eliminating the competition for pathogens)

• Surgery: openings natural barriers to infection, so microbes can enter 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.

MODES OF TRANSMISSION

• Contact transmission.

• Droplet transmission.

• Airborne transmission.

• Common vehicle transmission.

• Vector borne transmission.

MODES OF TRANSMISSION

• 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 (transfer of microorganisms between a susceptible host and an infected person)

• 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.

MODES OF TRANSMISSION

• Droplet transmission:

Occurs when droplets generated by coughing, sneezing, talking (short distance )

• Airborne transmission: Dissemination can be either airborne of evaporated droplets containing microorganisms

that remain suspended in the air for long periods of time) or dust particles containing the infectious agent.

Microorganisms carried in this manner can be spread widely by air currents and may become inhaled by a susceptible host within the same room or over a longer distance from the source patient, therefore, special air-handling and ventilation are required to prevent airborne transmission.

Microorganisms transmitted by airborne transmission include Legionella, Mycobacterium tuberculosis and the rubeola and varicella viruses.

MODES OF TRANSMISSION

Common vehicle transmission:

"vehicle," such as water, food, air, or the blood supply used by a transfusion service .

• Vector transmission:

Occurs when an insect, arthropod, or rodent is the source of infection.

SOURCES OF NOSOCOMIAL INFECTIONS

• 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.

CAUSES

• The causative microorganisms may be broadly classified into the following categories:

1. “Conventional” pathogens that could cause disease in healthy persons

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.

CAUSESMOST COMMON PATHOGENS

• 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%).

CAUSES

• 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.

CAUSES

• 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).

CAUSESVIRUSES

• 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.

CAUSESACCORDING TO SOURCE

Fungi Viruses Bacteria Source

Aspergillus Varicella zoster (chickenpox)

Influenza

Gram-positive cocci (originating from skin)

Tuberculosis

Air

CAUSESACCORDING TO SOURCE

Fungi Viruses Bacteria Source

Aspergillus

Exophiala jeanselmei

Molluscum contagiosum

Human papillomavirus (bath water)

Noroviruses

•Gram-negative bacteria :Pseudomonas aeruginosaAeromonas hydrophilia Burkholderia cepacia Stenotrophomonas maltophilia Serratia marcescens Flavobacterium meningosepticum Acinetobacter calcoaceticusLegionella pneumophila•Mycobacteria:Mycobacterium xenopi Mycobacterium chelonaeMycobacterium avium-intracellularae

Water(tap and bath)

CAUSESACCORDING TO SOURCE

Fungi Viruses Bacteria Source

Rotavirus

Caliciviruses

Salmonella speciesStaphylococcus aureusClostridium perfringensClostridium botulinum Bacilluscereus and other aerobic spore-forming bacilliEscherichia coliCampylobacter jejuniYersinia enterocolitica Vibrio parahaemolyticusVibrio cholerae Aeromonas hydrophilia Streptococcus speciesListeria monocytogenes

Food

PREVENTION OF NOSOCOMIAL INFECTIONS

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.

PREVENTION OF NOSOCOMIAL INFECTIONS

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.

PREVENTION OF NOSOCOMIAL INFECTIONSHAND WASHING

• 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.

PREVENTION OF NOSOCOMIAL INFECTIONSPROTECTIVE CLOTHING

• 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.

PREVENTION OF NOSOCOMIAL INFECTIONSPROTECTIVE CLOTHING (GLOVES)• 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.

PREVENTION OF NOSOCOMIAL INFECTIONS ARCHITECTURAL SEGREGATION

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.

PREVENTION OF NOSOCOMIAL INFECTIONSROLE OF THE MICROBIOLOGISTThe 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.

PREVENTION OF NOSOCOMIAL INFECTIONSROLE OF THE MICROBIOLOGIST• 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.

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